This is driving me nuts!
After doing the bypass I'm getting a little engine whine and noise from panel lights. I undid the bypass and the noise goes away.

Here is what I did:


I just connected the corresponding HU outputs to the inputs. This leaves 4 wires exposed- the EQ inputs and outputs. I tried grounding the open EQ inputs but that does'nt alleviate the noise. The problem is definately coming from the bypass, but is there something I'm missing? Should I try a Line level noise suppressor? Am I gonna have to live with it?

Thanks,
Iggy

 

Iggy,
I'm thinking what things you might try

After such a great install job, it's a shame that you have to run across this problem.

From what you say and what you've done... The only thing I can think is happening is a gross mismatch of impedances between the head unit line out and the head unit bypass back in?

The EQ must act as a buffer amp as well as an equalizer. My GUESS is that the head unit output is a relatively high impedance output (1kohm-10kohm) and the head unit input that is supposed to come from the EQ output is also a relatively high impedance input.

The EQ output is probably a low impedance buffered drive amp out.

One possibility... Let's just say that the headunit output is a 10kohm impedance and the bypassed head unit input is also a 10kohm input impedance, then substantial noise could be picked up by the bypass wire and input electronics, etc. due to the now totally high impedance path???

In the stock install... If the input impedance of the EQ unit is lower than the returned input impedanace of the head unit, then you will have some noise immunity in that part of the path by the fact that that part of the signal path is kept down at a lower impedance. I would MOST PROABABLY guess that the output impedance of the EQ is a much lower impedance than the signal coming from the output of the head unit line outs. Even though it's not capable of driving a speaker level load... it's easy to buffer a signal and lower its apparant output impedance down to 10ohms or so. This would provide a LOT of noise immunity in that half of the path. If this is what the stock system does, than it would explain your problem...

If your problem does indeed go away by hooking the EQ back up... then something like this is going on? Was the STOCK interconnect cable between the head unit and EQ shielded? If so, you would want to also shield your bypass loop. You could also have a ground loop problem, that requires you to break the ground between the head unit and the EQ on that particular cable... You don't want to butcher the stock harness, though, just to try things that may or may not help.

The only thing I can think of to try would be to "LOAD" the returned bypassed input of the head unit with a resistor to lower the impedance of the bypass path. Of course this is not the same as adding a buffer amp in between the bypass, but it may help. Since the bypass is only a short loop, and any resistor you place across it to ground will also load the head unit line out, be careful not to start out with too low of a value resistor. I would think that the head unit line out would not be smoked by placing a 100ohm-1kohm resistor across its output to ground, however, the level may decrease. If the signal level decreases significantly, then there is a series build out resistor in line with the output, or it is NOT a buffered output. In that case, you may be screwed and will have to add a buffer amp or something else in between the bypass loop.

With no signal through the system, but powered up, check to see if there is any DC on either of the bypass lines. If there is, put a 100uF electrolytic capacitor in series with the resistor to ground. Be sure to have the polarity of the cap correct. I would hope that the stock outputs and inputs are cap coupled... but they may not be? Power things down and do an ohm meter check across the four outputs and inputs that we are talking about. See what kind of readings you get. If you get a steady ohm reading, then there is a direct resistor path to ground before any coupling caps. IF the ohmmeter just keeps charging up reading higher and higher values, and then when you reverse the leads of the ohmmeter it starts out as a short and rises and rises again, then there is a cap in series with whatever you are reading across. In any case, as long as there is no DC, you should be OK to use a direct resitor across the bypass to ground. If there is DC present, it may be becasue the lines are COMPLETLEY OPEN... put a 10kohm across that line to ground and see if the DC goes completly away as an output coupling cap charges up? DON'T PUT ANYTHING LOWER THAN THAT ACROSS SOMETHING THAT HAS DC ON IT OR YOU MIGHT CAUSE SOME DAMAGE!

After checking the DC status, start out by placing a 1kohm resistor across the bypass loop to the HEAD UNIT GROUND. Just to be safe, you can use a big electrolytic cap in series with the loading resistor... See if that does anything to reduce the noise. I'd keep trying until you have gone down to a 100ohm resistor... Until we've seen the actual schematic, I'd definitely put a cap in series with any resistor below 100ohms. If at that point, NOTHING has changed... then I'd probably not go much futher with this approach... and we'll have to re-think things...



Give the "resistor to ground across the bypass" a try to lower that path's impedance and see what it does... Also check into the shielded cable routine.

If none of that helps... That sucks! Do you have any DETAILED component level schematic drawings of the head unit and EQ unit? IF so, they would be invaluable to troubleshoot this grief. I would love to see the four inputs and outputs that we are talking about here on an actual schematic. With that, we could probably do an internal mod to the head unit that would fix the problem, but VOID THE WARRANTY!@#$%^

Good luck! Hope some of this ends up helping you... Southbound

 

Southy,

I read your post about ten times and I only understand about half of it :p .

Anyway, this is were I'm at.

Dash light noise:

I was able to reduce some of the dash light noise by soldering a jumped wire from the output shielding(B5) to the actual wire sheilding containing the HU input wires(B3,B4,B9). Somehow this particular wire bundle Shield was never grounded properly. could there be be a ground loop somewhere between the HU & EQ?

I found that there is no DC on the bypassed wires but there there is about 4 VDC on the EQ inputs(why would there be voltage on the inputs?). As far as the ohm meter check, I could find no continuity between any of the wires or to ground for that matter. I Do you still think I should try the resistor theory? I’m a little lost as to how exactly I should wire them up.

Engine noise:

I Still got it. When I take the RCA’s out of the LOC’s it all goes away, including the dash light noise, so I’m thinking it’s not the amp’s ground or power supply. Is my line of thinking correct? Maybe I should try an inline choke of some sort.

One intersting tidbit I happened upon last night was about what to do with the open EQ inputs:
__________________________________________________ _
Quote by DJSTEVE

"Forgot to mention one other caveat - after bypassing the EQ for the left and right channels (while leaving the "sum" signal intact) I found two small but odd behaviors:

(1) The subwoofer feed now follows the fade control on the HU. In stock configuration, the subwoofer is active whether faded fully forward or rearward, but after bypassing it fades with the rear speakers. When faded fully forward, the subwoofer is off. I found this to actually be an advantage in my case, in that now I have a convenient sub output control (as I fade from rear or all speakers to front, the subwoofer output decreases).

(2) I found that the sub output was greatly exaggerated if the left/right EQ inputs were left floating after the bypass. By grounding the open inputs to the EQ, the sub output returned to a normal level in comparison with that of the HU. The EQ appears to have some sort of active processing of output level (perhaps for distortion control?) which is confused by the open inputs. "

And then a follow up:

"I found that the EQ open input problem was alleviated either by grounding the inputs (connecting them to audio common) or by doing as you suggest - simply connecting the EQ inputs to the EQ outputs. In fact, that is the method I used since I had already attached mating connectors on each to allow switching between bypassed and non-bypassed configurations. If you make the connection "live" while music is playing, you'll notice a strange result - the sub output level will slowly over about 5 seconds (i.e., not instantaneously as you might expect) return to a level which is consistent with the HU. This is what leads me to believe that there is some active processing in the EQ unit which is artificially raising the sub output while the left/right inputs are left open."
__________________________________________________

I tried the same thing with spade & lug connectors and found this to be true!
I had originally grounded the open EQ inputs to the car and left the open outputs floating, and found that some really bassy music would make the sub really go wild. Last night I connected the respective EQ inputs to outputs and sub behaves normally now. Boy I need to get a new one with more power. Stop the insanity!


BTW, I'm having a hard time finding .05uF caps with voltage above 50V for the terminator mod. I'd rather go with 500v or 1kv. Any chance you could hook me up?

Iggy

 

Iggy,
There's some weird stuff going on in that EQ circuit. I would assume that it has a ALC circuit (automatic level control) and a compressor. (Sounds like a gain stage as well) This usually has an attack time which would account for the five second ramp up. This is actually a good thing for a low powered amp. It does prevent hard clipping and square waves being fed to the speakers. What I don't get is how having the EQ line outputs open affects the BASS level???? There's definitely some bazarre stuff going on. Bose has done all they can do to go to great lengths to screw things up. They should have just invested the money, time and effort into providing a stock amp with some REAL power and some REAL speakers... Instead of all of this bogus crap! SAD!!!

You wouldn't normally want to tie the output back to the input of any amplifier device. That would normally cause oscillations. But, if you've tried it and it helps... what the hell is going on is really weird. If we had an actual schematic of the EQ, we could probably do an internal mod that took the EQ high frequency pre-emphasis out of the circuit. We could probably find the componenents responsible for the high frequency boost and make it flat. But knowing BLOWS, they've probably put it all inside of some proprietary block and wont disclose a schematic.

I would still try a resitor from your bypass junction to ground to lower the impedance and susceptibility to noise at that point. I think you tied the bypass wires together with a wire nut. Take the wire nut apart and add a resistor with the other two wires. Take the other end and connect it to the head unit ground. Start with a high value first just to make sure nothing smokes or becomes unbiased. with no DC present on any of these head unit lines, I should think you would be safe. Try the resistor to B5 the shield connection. Also try it to B11 (the true head unit ground connection) and to B4 and B8 the "common" for the head unit signals. If you get a LOT of buzz or squeal with any of these connections, obviously it's the wrong place to connect to and/or the wrong thing to do. You can easily get buzz or squeal with your fingers on the contacts so use a short clip lead on the ground side to connect the resitor to these various points and then do a hands free test. Start with 10k and move down to 1kohm and 100ohms and possibly 10ohms depending upon the effect, if any? This might help, and it might not, but if it were mine, I'd give it a try.

Also the more I look at a partial schematic that I have, I'm wondering if you need to also loop the "common" as part of your bypass. THAT COULD VERY WELL BE WHERE THE PROBLEM LIES. Try directly looping the common by cutting and tieing together B4 to B8. The more I look at things, it appears that the head unit is either using balanced inputs and outputs or at least they are floating from hard ground a bit to prevent oscillations, etc. It just may be that when you bypassed the EQ without also carrying the common across in the bypass, the the head unit returned inputs have no proper common reference. My only concern here, is that if you cut and loop the common from the head unit by cutting and tieing B4 directly to B8, then the "SUM" output from the head unit will not carry across its appropriate common to the EQ. SO FIRST, Try shorting B4 directly to B8 with it still connected to the EQ and see if that helps. If we get lucky, it just might??? That would keep the subwoofer "SUM" path's "common" continuity intact. It could also cause a ground loop as well? When you start off with tieing the different grounds to the commons... You might want to use a 10ohm resistor, just in case there is some voltage potential across the floating commons to hard ground. Measure the DC on the commons and see if there is any voltage (proabably milivolts) with respect to the shield and/or hard ground B11. If there's a few milivolts, go ahead and directly short it to one of the hard grounds and see if that potential was the source of the noise. If there's over .5volts DC, I'd use a 10ohm resistor first, just to be safe since we have no schematic and we are only guessing at what is inside of the boxes. It may take a lot of experimentation with all of these options to finally find what fixes things. You could also try connecting the commons to a hard ground such as B11. These grounds are all isolated for a reason... but once the signal is isolated from the EQ, different rules may apply... there are the commons(B4/B8), then there is the shield ground (B5), and then there is the system ground (B11). SOMETHING will work, it's just finding the proper combination of power line conditioning, grounding, impedance matching, ground isolation, buffering, and shielding.

If pulling the RCA inputs from the LOCS stops the noise... That WOULD seem to indicate that the noise IS RIDING ON THE SIGNAL, as opposed to being picked up through the power line of the new amp. That also goes along with the fact that the noise goes away when you hook the EQ back up. If the new amp were picking up the noise through the power line or a bad ground... It should still pick it up in that mode as well.

As far as locating .05uF/1KV caps try looking up NTE electronics to locate a dealer near you. check them out at www.nteinc.com They spec the .05uF at 50,000pF I believe, but it's the same thing. If all fails, perhaps I could hook you up with some. But you'd owe me a FALL FOLIAGE update prediction for this year. I tend to visit New England about every other year during the first week of October to dig the FALL FOLIAGE COLOR! The first two trips were just unbelievable... The third trip, Oct 2000, was a bit disappointing. The leaves were not near as brilliant as the previous visits. Locals said it was because they had experienced a drought that year... What has the weather been like this year so far? Is it the winter weather and snow or the summer rains that make for the best foliage? We're thinking about another trip this year, but I want the foliage to be right. It's a bit too far to drive the TLS, but I'd LOVE to take it with the sunroof open cruising down the "KANK" highway!!!

Good luck
Southy

 

Southy,
I think I need to clean my panties now.
IT WORKED!

The first thing I did was to jump between the commons which reduced the panel light noise a bit, but the engine noise was still there.

Next I snipped the commons and tied off the HU side and the EQ side.......BINGO, all noise gone and the sub still works! Apparently the sub only need the sum signal to work. I'm surprised I did'nt blow anything up during this whole fiasco, and I don't know why it works but it does and that's good enough for me! I can't believe nobody else tried this to get rid of the noise. Maybe I'm just too freakin anal about things being perfect:devil: When I get some time I'll post a synopsis about the whole thing and maybe Snook will put it in the FAQ section

I've decided to move the LOC's behind everything by the firewall so I can get to the gain controls without taking anything apart.

The only thing left to do is figure out a new sub setup(with minimal intrusion to trunk) to take advantage of the fifth channel on my amp. That will be a piece of cake compared to all this other stuff.:o

Thanks for the link. I had used it before from one of your other posts, but I was looking in the wrong place. I found an electronics supply shop about 15min from home that carries 50,000pF 1kv caps. Time for the Arnold mod. I'll let you know what I think.

Dude,
Thanks for all the help on this thing. If you come up this way I'll fill your belly with all the lobster and Becks you can handle. I'll even throw in a free folliage report :p

Iggy,
the satisfied one

 

i can't believe you two were able to solve the problem with these posts! southy, you had me at "hello" very impressive! i didn't understand 1/4 of it., and i read like 5 times! mad props dude! that is so cool! iggy , what do you want to know about my box pics of the fabrication process? some of the install is missing pics , cos we were working here and there! i could tell you how it's done? it 's a little complex? alpine has the dimensions of our cars in their design systems software? i could probably get the schematic for you, or go to a local installer, alpine dealer. they could get the dimensions too. the molding, and dynamat extreme insulation are pretty basic! hope this helps... kman

 

TEAMWORK IGGY!

I'm really glad to hear your good news! As I said in the above quote, the more I looked at the circuit last night, the more it became apparent that the proper ground probably wasn't being carried through.

By simply looping and only bypassing the two signal wires, they would have to rely on chassis ground for their signal ground. That would have the potential for the ground loop that obviously occurred. The "common" of a signal path should have no voltage on it, but carries all of the return signal current. If the current on that common is unbalanced from the signal current on the high side of the line, then a small voltage potential will exist and be amplified. It would also be further amplified in your aftermarket amp, causing you even more noise. As bypassed in your first configuration, the common does make its way back to the head unit, but not before picking up extra current from the EQ box that is not associated with the signal current in your bypassed wires. That is why you had to break the ground between the two units and then tie the commons together to properly complete and balance the entire bypassed circuit path.

The "Sum" output is now getting its common ground from the head unit through the chassis ground, the head unit ground (B11), and the shield ground (B5). This could have the potential for a ground loop situation as well, but, in this case, apparantely not. We've luckily dodged another bullet there... Ground loops are very hard to sometimes predict. The proper grounding scheme depends upon the impedances and therefore the currents involved as well as the amount of gain involved. The EQ circuit would have very little gain I would think, and therefore not prone to unbalance the current through the "common" path as compared to the hard ground. It could also roll off any high frequency noise that it did manage to pick up by the fact of its low pass subwoofer EQ response. Sometimes it takes adding a ground to correct a ground loop condition, and sometimes it takes breaking a ground... voodoo...

It's probably just a matter of time before I will have to bypass my EQ as well. You mentioned that you thought the EQ did have some slight gain? Do you think this was just the high frequency pre-emphasis or actual gain across the band? If so, how much gain? Without the additional amp, could the stock head unit be driven to its limit with the EQ bypassed? My first step would be to simply bypass the EQ by following your now perfected method, and hope that I could live without adding another amp. The head unit gives me enough volume at this point (albeit just barely) but will I lose too much level with the bypass to be able to push the head unit back up to its full capable volume? Please let me know your feelings on that before I try to do the bypass and find myself disappointed by lack of adequate volume. Also, could you try and describe the difference in sound that you hear with the bypass installed verses the EQ in circuit? Does the EQ just add a lot of high frequency boost, or does it also add "mush" or distortion to the signal? Granted you can now push yours a lot harder with the extra amp. But at medium levels what is the difference that you hear?

Sorry for all the questions... but I'm now getting more and more excited about trying to do this for myself now. I have heard other people talk about the bypass and also mention the slight noise problem. Their solution was to ground the EQ inputs... but that didn't really cure the problem. It sounds like we have now come up with the proper solution

Just so I have it straight as to your final configuration...

1. You cut the FOUR signal wires between the head unit and EQ and then tied the left head unit output back to the left head unit input (old EQ return) by tieing B1 to B3. You also tied the right head unit output back to the right head unit input (old EQ return) by tieing B7 to B9.

2. To complete the bypass and to eliminate the ground loop condition which caused dash light and engine noise to be injected into the signal, You cut the TWO common wires between the head unit and EQ and tied the two isolated common wires together on the head unit side by tieing B4 to B8.

Did you also tie the two remaining cut common wires together on the EQ connector side? I would think so...

3. As a precaution against noise pickup and to prevent strange subwoofer output characteristics, you tied the OPEN EQ input wires to the corresponding OPEN EQ output wires.

After correcting the ground loop/noise/whine problem, do you feel it is still necessary to tie the EQ inputs to the EQ output? While you're making sure that you have come up with the "Perfect" bypass technique, it might be worth all of our while to see if that is still neccessary. I can see, for good engineering practice, shorting the OPEN EQ inputs to ground, but connecting them to the EQ LINE outputs to make the subwoofer output behave correctly definetly seems weird. HOWEVER, DON'T MESS WITH SUCCESS! Who knows what's going on in that POS box??? If that's what it takes to make the system behave properly, sound flat, have no noise or oscillation problems, and NOT smoke anything... THEN SO BE IT... I'd just like to know for sure how you end up with things, so that I can do my bypass the same way. In some ways I guess you're the guinea pig as well as YOU'RE THE MAN! You're the man for being persistent enough to force and track down this issue. I'm that anal as well, and am glad I was able to help. When I heard that you had the engine noise issue, I was saying to myself that I'm glad I hadn't pulled my dash all apart to end up with the same result. You are not the only one to experience this ill effect. I believe that there are a LOT of people out there that are just "living with the problem". As you said, it was mostly ignorable, but still a constant reminder that something was wrong... I like your perserverence! You are kind to think of posting the results of this so that others can perform the bypass without living with the noise problem. Others will also know what to do if they want to improve their already bypassed systems.

When you get the time, after you thank me again for Arnold's "terminator mod"... (just kidding) Although after looking at all of that zipcord running underneath your carpet and doors, I'm betting, you'll be pleased at the results if you give it a fair listening chance. Anyway, if you could find the time to post a detailed procedure for just getting to the back of the headunit in order to do the bypass, I'd REALLY appreciate it. Does the Helms manual really show you how things are attached. I'm afraid to just start yanking and prying at things hoping that they will come apart, when instead I might just end up breaking fasteners, etc. I want to make sure that I don't break any trim during the process, etc.

From the hours that you were working and the scope of your work... the neighbors MUST have been thinking that you had a "chop shop" going on in your garage! LOL

Thanks for the thanks, keep us posted on your final thoughts and configuration. BTW, I like Becks Dark and Lobster bisque! :p

Southbound

 

Hey Iggy..can you give a summary diagram to do the eq bypass? I'm so LOST!!! Well, maybe i should read this thread slowly rather than skim through

 

This might make more sense:


Iggy

 

Kman,

I was just curious how it all went together and what was fabricated and what was not. I must say, your setup makes mine look pretty insignifigant. This was my first install of this magnatude so I guess I did okay for an amatuer.

Cheers,
Iggy

 

Southbound,
These should answer your questions about getting the HU out. I'm still thinking over some of your other questions to which I will have answers soon.:p
treat 1
treat 2
treat 3
treat 4

BTW - why did you choose the screen name "Southbound"?

Iggy

 

You're the man Iggy!

Thanks for all of the work to scan and post these pics of the stereo removal process. I've printed them for reference.

Is it possible to just take the bowling ball trim off and the front side console piece off just to be able to reach around to the back of the radio? If all I wanted to do was cut and tie together the bypass wires, I would hope that I wouldn't have to actually remove the radio. Is that possible, Or is the harness so tight that you had to actually pull the radio and do the jumpers on the bench? If it's possible, it looks like the passenger side gives the best access to the connectors, is that correct?

The only other question I really had for you was how much gain/volume do you figure you lose with the bypass? Is there enough range left to just turn the volume knob up full and then still be able to drive the head unit to its max volume? If so, I'd be hip to doing the mod. If you think that the level drops enough that you need an extra amp to make up the gain, then I'll have to think twice about things. But I am getting tired of the "hash and pssst pssst cymbals, etc."

So how would you describe the difference in sound with the bypass. Did the EQ just seem to add a high frquency boost, or did it also add "mush and distortion" to the sound? I'm sure the response is now flatter, but does it also have better clarity?

Thanks again for all of your help in talking me through this procedure. Obviously, I'm not afraid of dealing with the wiring, I'm just concerned about breaking fasteners and scratching up things during the process... Do you have any TIPS on how to prevent this kind of damage? Do the clips break easy, or do they come out and go back together easily and securely?

I won't bug you for anything else, I know how tiresome it can get to keep answering the same question over and over. I'm sure you'll get to the point where you say "JUST DO IT"...

"Southbound"... Don't really know why I came up with that name, except that I had to think of something in a hurry the night I logged in. I grew up in the midwest and hated the cold winters. As soon as I was 16, a group of friends and I would always take road runs whenever and wherever we could. We were all "Allman Bros." freaks. We would follow them around in concert during the seventies. We seemed to always head south for our Road Runs and the Allman Bros. had a song named "Southbound"... So I just picked that name one night to re-live my youth and think about future road runs in my NEW TLS!

But you can call me "Southy"...

 

Southy,
Here are some thoughts I have on the whole thing. I think there is a slight gain across all bands from the EQ, which might be evidenced by the 4vdc I found on the EQ side. This is also most likely exaggerated by the high frequency boost the EQ puts into the signal. Before I hooked up the amp I did have a chance to listen to the set-up being driven just by the HU. The HU did have a hard time driving the JL’s in front but had no problem with the polks. There is no doubt that the bypass flattened things out, so I would say go for it! Here’s a quote from DJSTEVE a while ago:
__________________________________________________ __

“I just replaced all 4 door speakers with Infinity components and bypassed the BOSE EQ unit on my '02 TL-S this weekend, and I can tell you with certainty that the original speakers are all BOSE, while the headunit is manufactured by Pioneer.
BTW, for anyone thinking of replacing the stock speakers with high quality components, bypassing the BOSE EQ is necessary to avoid extremely exaggerated high end. The EQ is in a line-level "loop" with the headunit, making a pronounced frequency adjustment (mostly in the upper frequency range) in an attempt to make the existing BOSE one-way paper cones sound decent. Of course this means that you get to hear this EQ curve in all of its ugly glory once you put some decent drivers in the doors. There is one downside to doing the bypass - the EQ also adds a tiny bit of gain to the signal which you lose, but (at least for me) there is still plenty of power in the stock HU. The overall improvement is night and day - I can't believe how much better it sounds”
__________________________________________________ __

I had already spent a lot of time messing around in the radio bay, so when I finally connected the EQ inputs with the outputs and it worked I decided to let well enough alone and stay with it. As someone had mentioned earlier, there does seem to some kind of active noise processing going on in this thing and somehow it “likes to hear itself talk” if you know what I mean.

Getting to the harness is, unfortunately, not as easy as taking the bowling trim off and working around stuff. The two side panels below the bowling trim are interconnected with the rear console so that needs to come out first. Honda seems to like jigsaw puzzles because this is! The actual EQ harness is pretty tight also, and I found the only right way to do it was to pull everything out to give myself some room (I hate working in cramped spaces). There really is no way to do the bypass on “the bench” as you mentioned because Honda bundled bundles with other bundles, This is not a problem though once you get back there and pull a little bit of the electrical tape away.

As far as pulling this stuff apart, it really is not that bad. The car is well engineered in that things come apart and go together very nicely. There is never a need to force anything apart (if you are you’re doing it wrong). I really would not worry about breaking things, just take your time and study the pages I uploaded so you know where each type of Fastener is. The seats do not have to come out but you will need a very short Philips screwdriver to get between the seats and the two screws on each side of the rear console. Just move the seats until you get the most amount of room to work the screwdriver in there. The first time I took it apart I would say it took me about 20 minutes, and a little less to put it back together. I can now do it in ten, you get the idea.

Southy, I SAY GO FOR IT!

That’s all for now because I have to get dinner ready. See ya.

Igster

 

Iggy,

Thanks for all of your advice and help...
You've convinced me to go for it! Now that the noise issue has been resolved, and I have the removal instructions in hand... I'm running out of excuses. I can't handle that extreme HF response curve anymore. I've put tweeter resistors in series with my POLKS, but it still just doesn't sound quite right. It's a lot better than stock at this point, but the bypass mod is just too (electronically) simple not to try.

The mechanical disassembly is the scary part, but your print-outs have helped calm me down and have shown me where to start. When looking closely at the drawings, they even show you which direction to pry and pull first and then second. I don't think I'll have any problem getting the rear console off along with the following bowling ball trim and then the side panels. I'm hoping at that point that I might be able to pull the connector loose and do the bypass from the side. (I'm used to doing work in cramped places) and your wire nut technique should be fairly easy to accomplish. If not, I'll have to go through the whole routine to finish it. At that point, I'll be too far along to quit then! It sure seems ridiculous to have to take that much crap apart just to pull the radio. It's the stuff around the shifter and coin tray and front top console that looks difficult to me. I'm hoping to avoid that.

heyrandy, if you're reading this, I'm not sure if I'll get to the bypass mod this weekend or not. If I do, I'll keep everyone posted as to my evaluation. Who knows, after the bypass, I may have to pull the tweeter resistors back out??? I've only put them in the rear at this point... and I guess I'd rather see how things sound with the EQ bypassed than to add tweeter resistors in the front at this point. Will the madness ever stop!!!

Here's cheers to all of us

Southbound

 

Nice job Iggy and SB!

I just discovered this post. Wow! I think I'll wait a week or two to see what you (SB) find out on the volume with the EQ bypassed. Even if I need an amp, I can ante up for one if need be. What did you get and what did it cost Iggy? Does the fader/balance still work afterwards (not that I ever touch it once it's set)?

So you are into jam bands as well SB? I saw Devon Allman play fairly recently at a small venue with a Dead cover band from St. Louis. They played several ABB staples. He sounded alot like his dad. It was a great show.

 

Heyrandy,

JL XR650-CS front
Polk DX-6 rear
Earthquake Tnt-900(65wRMSx4, 200wRMSx1)
two 2ch PAC loc.
Tsunami double shield cable
Cascade V-block front & rear doors
Cascade DEFLEX powerpads (front)
Southy's Arnold mod
The elusive EQ bypass(without noise!)

All told about $650.00. If I had taken this to the local shop I'm sure I would have paid $2000.00. With the amount of time I have invested in this project I would have been paid $5000.00 for the work I have done with my real job(unfortunately stereo installs and flying airplanes are not the same thing), but I KNOW the work was done correctly and to MY standards.

As far as fader control goes.....yes everything works just like stock but that is because I installed front and back LOC's(line out converters) to feed a low level signal to the amp.

This was pretty much my first stereo install of this magnitude and the funny thing is that I had no idea what an LOC was before I started this project. Talk about a steep learning curve!

Here is most of it:

Iggies install

Iggy

 

This group just keeps getting more uncanny by the moment.

You say you fly airplanes, Iggy? I don't do it for a living, but I got my private pilot's license before I graduated high school at the age of 17. The FIRST weekend after my 16th birthday, I went out to the airport and took my first lesson. I soloed after 8 hours Of course that was in the midwest before all of the traffic and ATC control that exists today. Now I'm still just a Private Pilot, but I fly in the L.A. Basin. It's hard to find those grass fields out here to go land on while taking a date on a picnic. That used to be one of my smooth "moves" during my college years. While I may not have made a career out of aviation, one of my friends that I took up for his very first flight has worked his way up the ranks and is now a Captain for Vangard airlines based out of K.C. I went into broadcasting and am now the Chief Engineer for an L.A. TV station. What's your situation?

heyrandy knows more about petroleum products than you would ever want to know or be able to understand! Iggy tapped into the speaker lines to feed his LOCS... so if his system still has fader control, then the stock head unit would also still have fader control. I have also already asked and Iggy has reported back that the headunit volume "ramp-up" circuit still works whenever you turn the key off and on. That is a nice feature that I wouldn't really want to lose... it helps prevent blasting or blowing the speaker at startup, and helps you mentally adjust to your last "Cranked up Session".

Some other nice forum member posted a frequency response plot that I have printed before and after the EQ bypass. I can't remember the post that it was attached to, but it was probably back in March. It's very dramatic. It shows a boost starting at around 5khz and peaking with a 20db boost up at 15Khz!!! It also shows about a 12db suckout between 600hz and 2Khz... Ugly stuff! The only good thing that I can see it does, is that it does roll off the subsonic bass starting at 40hz. By 20hz the response is down by 12db. Since the door speakers can't really produce anything down at that range, it's probably a good thing to have that bass rolloff to protect them from excessive subsonic impulses. I hope the flattened out subsonic bass response doesn't damage the POLKS at LOUD VOLUME. We could always add a bass blocker cap at each speaker to prevent this, but that's another mod and another hassle. Iggy, Have you noticed the midrange woofers or the POLKS breakup during loud bass notes? If not, we're probably cool by the fact that the source material probably doesn't really put out 5hz and 10hz notes. (At least not the music that I listen to) Other than that feature, the EQ totally sucks... all of these response bumps seem to follow a 12db/octave slope.

The more I look, the more I gotta get rid of it. I just can't see any downside to doing it after you have replaced your speakers with REAL speakers. My only concerns at this point would be to find a way to "HIDE" the splices so that WHEN I have to have my head unit replaced due to the CD changer jamming, (it's already starting to have troubles) they won't see the work behind there and then tell me that the warranty is voided??? Are there any aftermarket harnesses that we could use in between the headunit and factory harness to perform the bypass on???? I also hope that the slight loss of gain is not enough to prevent me from driving the unit to its full potential (as poor as that might be). We need all the signal that we can get to feed the POLKS at highway cranking speeds... Other speakers probably need more level. The POLK DX6s were about as effecient of aftermarket speaker that I could fine without it being to cheap of a replacement.

Take care guys! We'll beat BOSE at it's own game... I just can't believe the effort they have put in to design and EQ to make up for a cheap speaker instead of just losing the EQ and using good speakers from the start??? I'm sure it must be cheaper in mass production, but the EQ box has got to cost something... and decent two way speakers aren't that expensive when you buy them by the millions!

Later, I'm hittin' the fridge for a cold dark Becks... and then go dig up that old copy of "Mountain Jam"! Vinyl, no less... Southbound

 

I fly model rc airplanes. Does that count?

Iggy - Where do I find info on the earthquake amp and loc's. Approximately what did the amp, loc's and cables cost?

What did you do with the 200W channel?

Thanks

 

Southy,
Well let me put it this way. When you come out east in the fall, buy your tickets on United and you will be helping out my ESOP fund. I’m currently based in New York and on the B767. I mostly fly international to Europe these days but occasionally I get out to the LA area.

I started out flying sailplanes in Boulder NV and soloed at 14. A couple years later I got my private flying out of a grass strip in southern WI. Once I decided to get serious about the flying thing I went on to get my Commercial, CFII, MEL, ATP, etc. After flight instructing for a couple of years I got a corporate job flying a King Air and Lear 35. A few years later I got on with a commuter and then eventually landed the job with UAL. A long road to be sure, but it paid off!

Iggy? Back in college I used to “play around” with this gal that our frat used to call Iguana because she had such a long tongue. It was just a matter of time before no one knew me by my real name, but referred to me as Iggy.


Enough about me and back to the subject matter. I have found the Polk mids to perform very well, even with the extra power I’m throwing at them. One thing though, The Polk’s are still just a bit too bright for my taste. I may eventually throw a resister on the tweets. What do you recommend?

Iggy out

btw- I downloaded "southbound" yesterday and jammed for a while. Brings back memories of my party days.

 

Heyrandy,

The only reason I got the Earthquake amp was because a friend of mine hooked me up with it for a pretty good price. It's nothing fancy but suites my needs just fine. I'm planning on using the fifth channel to power a Kicker RMB-8 free air minbass sub that drcookie found will fit in the factory location with minimum fuss.

Here's some info:

Earthquake
PAC LOC

Iggy

 

Iggy,
Let me salute you for keeping up the ambition and dedication to climb the insurmountable ladder of an aviation career. You are living my dream as a teenager. From the sixth grade on, that was my dream... I did jump on things as soon as I could by throwing a paper route to pay for flying lessons when I was 16. While I've stayed current as a Private Pilot for 30 years, there were a lot of factors that detracted me from continuing up to your level. YOU'RE THE MAN! My second passion was to work in Television Broadcasting... At least I've made a "behind the scenes" career out of Hollywood for the last 25 years. I hope you've got reinforced cockpit doors these days. I'm sure you have to be disturbed from events of 9-11. Hopefully you at least carry a Becks bottle with you to crack over somebody's head... (I'm sorry for that pun, I don't mean to make light of that situation at all)...

I've spent the weekend from hell dealing with my own issues of the EQ bypass. If you could pull all of that crap apart in 10 minutes, you must fly at mach 4 across the Pond! I must really thank you for all of your printouts. Without them, one would be lost and or would most certainly destroy something in the process. You left out one page that describes how to take off the driver's side under dash panel. PAGE 20-66 I believe? I futzed around with the side panel trying to find all three screws on that side, before realizing that I had to take off the underdash panel first. Then it took me a while to relate to the bottom screw that holds it on. I was underneath upside down, using a right angled screwdriver on it before I realized that the side of it was the fuse panel, and all I had to do to get to the screw was to pull the fuse panel door off! Duh!

Anyway, I've got some good and bad news to report when I get some more time. There's a LOT of interaction going on between the head unit and the EQ unit. I'm not sure it's such a good thing to do afterall UNLESS you also add an additional amp to make up for the loss of gain.

Iggy and heyrandy, I'll post my observations and final opinions when I get more time... Right now I'm sore as hell from being upside down all weekend. In the end, I found that for me, the system was better left stock than with the EQ bypassed. I think I can deal with the POLK speaker brightness with tweeter resistors and a rolloff cap connected to the resistor at the speaker itself. Without another amplifier, It's the only way to have enough volume, no thumps and bumps, no noise, and no anomalies.

Also, THAT AMP SURE RUNS HOT!!! Too hot to touch the back heatsink with fingers after only a few minutes of moderate volume. I DON'T LIKE THAT! I'm hoping that the amp has a temperature sensor and shutdown, similar to its short circuit protection... because I'm not used to running amps that hot over extended periods of time. I can now see why one member has had his smoke... hopefully this isn't going to become a common problem as well...

Stay tuned, more reports later,
Southbound

 

Southy,
I look foward to your usual detailed report. Please add a reference to "WHO?" smoked their amp, and are you refering to the HU or EQ as the "amp" or is there some external amp I don't know about. I'm guesing you mean the EQ unit itself.

Cheers,
Iggy

 

Way to climb the mountain SB! I look forward to reading about your experiences.

Regarding Unocal gasoline, when O'Malley (quite a character) was running Tosco, he wanted to be the first in CA to eliminate MTBE. So the announcements were made etc. However, as I mentioned before, it's harder (more expensive for most refiners) to make gasoline with EtOH because of the vapor pressure issues. So they are now using some MTBE and some EtOH to meet the required specs. That's why the stickers are back on.

Smell it when you refuel. If you smell an ether odor, it contains MTBE.

 

Iggy,
The member who smoked an amp is BJsTLS. There is a current thread on this board called "Blown Acura Radio, need new one fast"... Or something close to that. It was his STOCK HEAD UNIT that smoked. Kind of scary... You should be running cool though, since you are not feeding a speaker load. You are only feeding high impedance LOCs. That should just have the output stage idling. Although it is putting out voltage, it is not sourcing much current into the LOCs. There should be no difference between the heat when driving the BOSE speakers or aftermarket speakers. They are both 4ohms.

Iggy, heyrandy,
I'm sure we all have a pair of very different ears. Mine are probably the oldest, but I still have a good range and listen to classic rock. We may all prefer different listening characteristics. It's a very subjective thing.

Having said that, I spent the weekend doing trials on the EQ bypass. Again, I've got to thank Iggy for providing the removal instructions from the manual or I never would have attempted it. I was very careful and it took me a couple of hours to dismantle everything. I ABSOLUTELY agree with Iggy, in that there is NO WAY to accomplish the bypass without completely removing the Radio Headunit. You have to remove (in order) the bowling ball trim, the rear console, the driver's underdash panel, the two side panels on the center console, the seat heater switches, the switch assy, the trim ring around the shifter, the front console assy, and finally the radio itself. The second time would definitely be easier, but some of the clips might not fit back quite tight. I had to spring apart most of them to make them feel right on the first re-assembly. I did manage to pull it all apart and put it back together and only cause two small 1/4inch scratches on the front AC control panel

The pain, was working on the harness and taking the radio in and out without scratching up the shifter plate area. Use whatever you can to protect things in that area.

OK, so now for my sound results...

After all of the hassle to get things apart Friday night, I simply cut and wired things up EXACTLY as Iggy had posted. Cut the in and outs and commons from the HU to EQ and jumped the ins to the outs on BOTH sides and also jumped the commons together on both sides. I used wire nuts, so that it was easy to take back apart. The wire nuts worked fine for my test, but the smallest ones that I could find, (gray) could be pulled off with a good tug. The wires are only 22 gauge.

When I fired things up, I had no noise, no thumps or bumps, just music. However, the music was SIGNIFICANTLY lower in level. It was definitely flatter sounding, but also thin sounding as compared to before. At MAX volume, I would say that I could only get about half the level out of the head unit. I drove around for an hour listening to tunes, and soon realized that at highway speeds, the volume WASN'T going to be loud enough for me. It might be loud enough for some, but not if you like to crank it. THIS WAS A HUGE DISAPPOINTMENT! I came back home and thought about how to put a line amp in between the jumpers. That is when I felt HOW HOT the amp ran. I could NOT hold my finger against the back heat sink for even a moment. It did not sizzle spit on my finger, but it felt close???

So at that point, I decided to take things back apart and measure voltages, etc to make sure that I wasn't doing something bogus to the amp and causing it to run hot. I found all sorts of interactive things going on between the headunit and EQ I measured like 5volts between chassis ground and the commons! I also measured a few volts between chassis ground and the various inputs and outputs. I EVEN MEASURED VOLTS ACROSS THE COMMONS! This told me that the commons are definitely floating from ground and from each other. The amplifier and EQ unit must be using "balanced differential" inputs, and therefore, by tieing the commons together things could become unbalanced and also account for the loss of signal level. That would knock it down by 6db alone. I decided to connect the commons back up in the stock configuration and leave the two signal wires bypassed just to see what effect that had. When I did that, the signal level came up to a better level (probably the 6db) but it was still probably down about 6db below the stock level. Surprisingly, It also seemed to produce more high frequencies in this mode???? With the initial triple bypass, the highs were definitely flat to the point that I couldn't quite get as much highs as I was used to with the treble control. NOW the highs were back up to a stronger level, but I sort of had Iggy's noise problems. I couldn't hear any engine noise or dash light noise in my system, but I definitely got a little "thump and bump" from the subwoofer everytime I turned on the headlight switch. With the volume all the way down, I could also hear very low level "motorboating" in the subwoofer. This was not loud enough to be heard once the music was turned up, but it still meant that something wasn't entirely happy??? I again drove around in this mode, and found that while the volume was louder, it still wasn't quite loud enough for my highway cranking mode. The amplifier ran JUST AS HOT in this mode with the commons back to normal. I came back and measured volts across the commons that would increase with the volume and/or especially with bass material being played. I opened the jumpers on the EQ side of things and listened again. This time the BASS WAS DEFINITELY OVER PRONOUNCED??? This phenomenon has been reported by others, and I found it to be true as well. The fact that having the left and right EQ inputs opened causes the subwoofer output to fluctuate is strange indeed.

LONG story sort of short... I could find no combination of jumpers that provided me with enough volume to be satisfied. Each combination of grounding or shorting the EQ inputs and outputs, etc. caused some anomaly in the sound, or the grounding, or the DC bias to the amp circuits. Sometimes it would sound very exaggerated in the bass, sometimes it would sound very flat and thin, sometimes it would sound about right, but still be below the normal volume level and have thumps and bumps go on with the subwoofer when other electrical circuits were cycled. It would probably develop the Iggy's engine noise at that point if I listened long enough.

SO I PUT EVERYTHING BACK TO STOCK, and found it to sound the best for me. I think the EQ box has a compressor/limiter circuit that helps to make the overall sound to appear louder and have more punch. This probably decreases the dynamic range, but gives a lot of apparent volume for a relatively small sized amp. In my case, I found that to sound the best with the stock amplifier. Yes, the highs are still too bright, but I think tweeter resistors and a rolloff cap would tame that down about right for me. It also lets me know that I haven't messed up the warranty on the head unit, etc. and I haven't messed up any bias on the amplifiers in some possible strange way. Also, in the stock configuration, when you fade to the front, the subwoofer still plays. In any of the bypassed modes, the subwoofer fades away when you fade up front??? Like I say there are a LOT of interactions going on... HOWEVER, THE AMP DID RUN JUST AS HOT WHEN THINGS WERE PUT BACK TO STOCK! So none of the bypass configurations had anything to do with causing the amp to run hot.

Final thoughts... If you are going to add an additional amp following the headunit, then you WOULD WANT to perform this EQ bypass. I found Iggy's three way bypass to be the most flat sounding and provided no strange noises and thumps, etc. I would advise that method as the preferred method as long as you have an aftermarket amp to make up for the lost gain. You would also have a good dynamic range in this mode, and still obtain a loud volume due to the additional amplifier's output power.

However, in the stock headunit, I don't advocate this EQ bypass mode with aftermarket speakers, unless you can live with about 12db of reduced volume. It will sound about half as loud at full volume...

For those of us with the POLK DX6s, I would tinker with selected tweeter resistors and a roll off cap to your personal liking. I tried this with one of my spare POLK speakers fed from my house stereo and found various combinations to tame the brightness down. I would suggest getting 5 WATT resistor values from 2.7ohms up to 4.7ohms and try putting them in series with the tweeter. This is easy to do on the back terminal strip of the speaker. Unsolder the positive tweeter lead from the crossover cap, and put the resistor in series with that terminal and the loose tweeter wire. Then use a 10uF "non-polarized" elecltrolytic across the tweeter side of the resistor back to the negative (common) side of the speaker. This will cause a 6db/octave rolloff starting from somewhere around 3.5Khz to 6Khz depending upon the value of resistor used. The larger resistor, the lower the frequency will start to rolloff. So you can try just a resistor, or a resistor and a rolloff cap. What seemed about right for me, was a 3.3ohm resitor and the 10uF cap to "common" after it. This would drop the overall tweeter by about 3db, and start a 6db/octave roll off at around 5Khz. That cap rolloff would counteract the boost provided in the EQ without having to tear apart the console and losing amp gain to do it. But try out different values to fit your particular ears.

heyrandy, it's your turn to experiment... try some of these values and proceed with your original plan. There's got to be a suitable compromise solution. P.S. Chevron also has MTBE labels on the pumps out here?

Iggy, you should be REALLY cool with your mod because of your aftermarket amp.

Out of bandwidth, Thanks for listening... Southbound

 

Southy,

EXCELLENT post. I wish I was as articulate as you are! That pretty much answered any and all questions I had about this thing. When I read your prior post I thought to myself "maybe I should'nt have bypassed the EQ", but now I can relax.

I'm sorry to hear about the 1/4" scratches. I now wish I had a Scratchpad with me while I tore the HU out and jotted down notes to give a step by step recount of the proceedure, although I don't think I could have worded it as well as you have.

I think the work you and I have done with this thing will forever remain in the anals of history for those in the future behind us trying to "tweak" their system.

Iggy

ps - Don't worry about he "pun". Yeah 9-11 was most disturbing, but what really gets my goat are all the knee jerk beurocratic reactions to security issues, which for the most part has been "window dressing" so the public can get warm and fuzzy and return to flying, without really solving the problem. It's only 10am and I may need a becks just to calm myself down after thinking about it . The job certainly isn't as fun as it used to be.

 

Thanks for being the test pilot SB! I bet you were wondering what the hell you got yourself talked into during the whole ordeal?

OK - I think I have a plan. I will do the back pair first:

I will buy a pair of 5W 3.3Ohm resistors and 10uF eletrolytic caps plus the stuff for the Arnold mods for my new back speakers. I'm assumming that I remove the crossover cap that comes with the Polks?

After a week or so of driving around, I will decide what to do different (if anything) for the fronts.

Since everything sounds different installed, it's tough to trial and error on the bench???

Chevron and Arco will use MTBE through the end of the year.

 

Hey Southbound et all,

Glad to see that there are others attempting the EQ bypass that I wrote about some time ago. I've had my EQ bypassed w/the stock HU (no LOCs, amps, etc) for almost a year now, and haven't experienced any problems. Interestingly, I have not had *any* injected noise (thumps, bumps, hum, warble, whine, etc) despite having left the signal common passing through the EQ -- different from your experience, it seems. I'm not sure what the difference might be, but I can tell you that I have often marveled at the impressive SNR that my HU is exhibiting - it is truly quiet. I guess I got lucky?

Southbound, I did share your experience of about a 3-6dB drop in perceived output from the HU after the surgery. For my tastes, I find it more than adequate 99% of the time (and well worth the price for the wonderful flat response I get), though I of course have to turn the volume level up closer to max than before. HOWEVER, I too have thought about placing a high quality line-level amp inline between the jumped inputs and outputs of the HU to compensate for the level loss. The HU amps show absolutely no signs of being saturated even with the volume control at "max", so I believe there is significant headroom to be tapped. What are your thoughts on this idea? The "EQ common pass-thu" is my biggest concern here, especially if it is a component of a floating balanced signal pair. Thanks for any insight you might have.

P.S. - Isn't it strange that the EQ subwoofer output becomes exaggerated if the inputs are left floating??? It was blind luck that I found that things settled down by connecting them back to the outputs, but electrically it makes no sense - weird!

-djsteve

 

Iggy,
Thanks for the comments and hope things can return to being fun at work for you sometime in the future? Not quite sure how, though... Your system should be good to go. If the floating commons are truly balanced differential inputs, then by tieing them together, they become unbalanced inputs like a common single ended RCA connection. This reduces the gain by 6db, and lowers the cmrr (common mode rejection ratio). On LONG wire runs, that could tend to make the signal more suseptable to picking up crosstalk and noise, etc. However, the bypass run is only a couple of inches, and you obviously haven't picked up any extraneous noise. Rather, you cleaned up your engine noise situation, so I wouldn't change anything. Ground loops, etc are strange animals and if you've found a cure, stick with it. REMEMBER, THE ENEMY OF GOOD IS BETTER! As for djsteves configuration of just simply bypassing the two signal wires and letting the commons remain stock... puzzles me as to why he doesn't notice the same sort of noise and subwoofer issues that we did???

djsteve, Are you sure that you can't hear a slight thump in the subwoofer with the volume turned all the way down and then turn the headlight switch on and off? That is what I experienced with my system wired as you have yours. Iggy's engine noise could have been more pronounced because of his additional amp. As far as adding a line amp in between the bypass jumpers, I've gotten out of the mood. It would take a lot of research and design and then could still run into grounding problems with that piece of electronics hooked up to power and ground???? I'm sure it could be done, but I just don't have the energy left. I guess if I was going to go to that effort, I'd rather add an extra power amp like Iggy did, so that way, I would not only gain back the lost volume but also be capable of more!

heyrandy, we've got to clear up a couple of things about the tweeter resistor mod. YOU WANT TO KEEP THE STOCK SPEAKER CROSSOVER CAP INSTALLED AS IS! Leave the 4.7uF cap in place on the POLK DX6s. Just unsolder the positive lead of the tweeter AFTER it has come through the crossover cap. There is a SMALL terminal in the center of the terminal strip that has one side of the crossover cap tied to the positive tweeter wire. Disconnect the tweeter wire from this terminal post, but LEAVE THE CAP CONNECTED. Then take the tweeter resistor and solder one side of it to the crossover cap terminal where you just took off the tweeter lead. Next, solder the loose tweeter lead to the other side of the tweeter resistor. This will now put the resistor in series with the tweeter and knock down its overall level a bit. The rolloff cap is an extra step you can take if you still feel that the tweeter level is too bright. It's probably a better way to conteract the EQ because it will follow a curve like the EQ boost, instead of simply an OVERALL cut to the tweeter. Using both should provide a lot of options. The EQ boosts at 12/db per octave I believe, and this rolloff cap will only rolloff at 6db/octave. So this wont entirely flatten out the speaker, but with the help of the tweeter resistor as an overall high frequency cut, and the head unit treble control, you should be able to find a happy medium. Most ROCK listeners like a little boost in the bass and treble anyway.

As far as connecting the speaker rolloff cap... BE SURE TO BUY A "NON POLARIZED" 10uF Electrolytic. 50volts would be nice, but 35volts will do with our stock amp. Place one end of this cap on the tweeter side of the resistor, (where you soldered the loose tweeter wire and resistor together), and connect the other end to the speaker's overall negative terminal. Use some RTV silicone to mount the resistor to the side of the magnet and use some tie wraps as a band around the magnet to hold it tight in place as the RTV dries. I haven't thought about how to physically mount the cap yet, but I'm sure it will fit somewhere. It could probably float in the air or be glued down to the magnet as well. USE INSULATION ON ALL OF THE LEADS... so that they don't crossover and short out on each other... especially with the terminator mod also installed. The more I think about it, it might be a GOOD IDEA to move up to a 3.9ohm resistor. This would keep from loading the amp heavier at the higher frequencies. I don't think there's enough energy up there to smoke the amp, since I couldn't even get a 4.7ohm resistor to warm up, but just because the amp does run so hot, it might be safest to keep the resistor closer to the stock 4ohm value. WITHOUT the rolloff cap, IT DOESN'T matter what size resistor you use, because you are only increasing the impedance of the speaker and therefore making the amp work less hard. However, with the cap added, it looks like a short up at the upper frequencies AFTER the resistor. This would be up a few octaves up from the break point, but if you have a 4ohm resistor before the cap... no matter what frequency, the amp never sees less than the resistor impedance. 3.9ohm should be a good value to use. It's not that great of a decrease. I'm using 4.7ohms in my rears (without the cap at this point)

You are right in that you can't really hear the final sound without mounting the speakers, but you can get and idea as to the effect on the tweeter. I REALLY advise you get a handful of clip leads and a set of 3.3ohm, 3.9ohm, and 4.7ohm resistors, and give it a listen up next to your ears. What you will hear is the VERY high "pssst pssst" type of sound go away when listening to cymbals or hands clapping, etc. It's not dramatic with these values that I'm talking about, but it should be enough to take the "BITE OUT OF THINGS". Any of those values should be safe on the amp with a 10uF cap, but just to be extra safe, the closer to 4ohms the better. I doubt that you will find that value of resistor rolling things off too much... if you do, don't use the cap and use a larger resistor instead of both cap and resistor. I wouldn't go under the 3.3ohm range WITH a cap to ground after it. Again, without a cap, ANY value of resistor is no problem to the amp.

Hope this made sense... If you have any other questions, feel free to clack on back... GOOD LUCK!

Southbound