I have Polk DX6's in all 4 doors and 1" kicker tweeters all powered by an amp (Eclipse model). The tweeters are a bit bright. If I turn down the trebble, that takes away from all the door speakers, but I want to keep the tweeters. Can I use some kind of resistor on the tweeters even if it is powered by an amp?

thanks

 

You might want to try disconnecting the tweeters in the DX6s and see how that sounds...

If things are still too bright, yes you can still add a resistor with another power amp, but it will need to be bigger than the 5watt version used on the STOCK Head Unit.

However, you should have room for a bigger resistor, since the tweeters are mounted away from the other speakers. Use a 10 or 20 Watt resistor and experiment with values between 2.7ohms and 6.8ohms until you find a value that you like. I suggest 3.9ohms... You can physically place the power resistor anywhere inside of the door frame and run wires from the tweeter to it. I'm not sure of your amp wiring configuration, but you might also have room to put the resistor in series with the speaker wire out from the amp to the tweeter... In any case, put the resistor in series with the positive tweeter lead.

Again, you might sound good by just disconnecting the DX6 tweeter wire. I'm not sure why you have a coaxial speaker and an added component tweeter in the first place? Especially with the stock EQ, I can see why you think things sound too bright. A separate tweeter would sound better due to your ability to place it higher in the soundstage as well as the fact that it's not blocked by the door panel plastic and grill cloth. Try disconnecting the DX6 tweeter first, and then mess with resistors if you have to.

GOOD LUCK!
Southbound

 

Thanks Southbound

I have already disconnected the tweeter from the front DX6's, I did that a few months ago. The kicker tweeters ( mounded on the triangular piece that covers the wring for the side view mirrors) over powers the front DX6's. I wouldn't mind hearing a little more mid-range from them ( front DX6's). Where can buy resistors? Radio Shack? How much do they cost?

thanks again!!

 

Thanks again for the resistor info. I bought a pair today and installed them.....the sound is much better, plently of mid-range and just the right amount of highs!!!!!

 

stampsosu,
Glad to hear it!

I was just going to clack out where and how to get them. I'll do it anyway for others that may be interested.

NTE electronics makes all of the values. They have distributers nationwide at small electronic supply type stores... including FRYS electronics. You can look for a store near you from their website at www.nteinc.com

I was going to say that Radio Schlock also carries a couple of common values like 8ohms and maybe 4ohms. What value did you end up with? As long as you're happy that's cool! Remember that you can make other values by putting multiple resistors in either series or parallel configurations.

Two 8ohm/10watt resistors in series would give you the eqivalent of a 16ohm/20WATT resistor.

Two 8ohm/10watt resistors in parallel would give you the equivalent of a 4ohm/20WATT resistor.

The TOTAL POWER RATING WILL ALWAYS DOUBLE no matter which configuration you use the resistors (series or parallel) But, the resistance value in ohms is different depending upon the configuration.

So if you can't find a 20watt resistor, you can always use two 10watt resistors either in series or parallel to gain the needed power rating.

Standard resistor values that would be stocked by NTE would include...
2.0ohm
2.2ohm
2.7ohm
3.3ohm
3.9ohm
4.7ohm
5.6ohm
6.8ohm
7.5ohm
8.2ohm
10ohm

These are standard 10% tolerance values that all resistors come in. It's pretty easy to see that you could come up with an infinite combination of values to reach a desired overall resistance.

HOWEVER, this use IS NOT that critical. I doubt that you can hear much difference between a couple of ohms change with the resistor in series with the tweeter. It Sounds like you got results quickly. That's a good thing... I'm just curious what value and what power rating you found available to buy, and what value hit the "sweet spot"? Also, where did you buy them?

The wattage should be large enough that the resistor doesn't get too hot to touch for several seconds. A 10watt or 20watt resistor can run very hot to the touch and not cause any damage to itself... but you want to make sure it's mounted away from other items that may melt, etc. YOU DON'T WANT TO BURN UP A WIRING HARNESS or door panel plastic, etc! I doubt that this can happen with any reasonable sized aftermarket amp... but it wouldn't hurt to listen and then feel how hot the reistor gets just to know you're in the "cool". A continuous sinewave would probably heat the resistor up, but music is very sporadic and is not continuous at all frequencies. So in practice, you can get away with a smaller wattage resistor than actual power calcutions made by using RMS power would call for. But it never hurts to be overrated... especially when you have the room available. You also want to mount it securely to something. Silicone RTV will hold it down nicely, or tie wrap it to a standoff somewhere... OR if it's held down by terminal lugs on your amp or crossover, that would be OK as well. Just so the LEADS ARE SLEEVED and it's not bouncing around somewhere or hot up against some plastic part or wiring harness, etc. I'm sure this is common sense to you and I don't mean to sound arrogant. You just never know who else reads these threads and may try the same thing without the due considerations? A lot of people ended up with wiring shorts on their DX6 installs just because they didn't go to the extreme measures that it takes to make sure everything is cool...

This info might help others out there in your same situation who are stuck with the bogus factory EQ. Now that you have a BIG enough series resistor to handle your aftermarket amp's power... you could also add an additional rolloff cap, if you so chose to fine tune the system even more. The cap value would depend upon the value of the resistor that you chose and your particular listening preferences. As long as you're happy... don't mess with a success! I just wanted you to know that the option is available. If you get into it... I'd try caps between 2.2uF and 10uF. A 4ohm resistor and a 4.7uF cap is what I have called for as mods on the POLK DX6 tweeter. I'm guessing that you are in that same range. Those values add an additional rolloff up at 10Khz in case you still find the sound to be a bit sibilant and hissy. Use the resistor to give you the volume that you want out of the tweeter, and use the cap to give yourself just a little added freq response adjustment coming out of it at the very top end. BE SURE TO USE NON POLARIZED ELECTROLYTIC CAPS RATED AT 5O VOLTS OR HIGHER! NTE stocks all of these as well... Radio shlock has a 4.7uF and a 10uF at 50volts in stock, I believe. The 10uf cap would roll off too much highs unless you have chosen a resistor value down around 2.2 ohms.

Again, it's a matter or combinations and your ears. BUT REMEMBER MY FIRST ENGINEERING RULE...

Rule #1. "The enemy of good... is better!"

So If your happy, quit while you're ahead and leave well enough alone... In any case, I'd advise that you listen to your new setup for a week or two before deciding if you think some more minor tweaking is in order.

CONGRATS! and Good luck!
Southbound

 

I went to Radio Shack and picked uo 10watt/10 ohm resistors. I have them parallel running on the postive wire. The guy at the store told me that if I ranned them parallel that would cut the ohm in half to make them 20 watt/ 5 ohm. But from what you are telling me, I guess is it really 20watt/20ohm. What does this mean? This is a stupid question, but with the resistors I have (10watt/10ohm) , could I do anything to take away a little more of the tweeter's brightness or power? Also, what is in sequence?. Is it just not parallel togther, but one in front of the other? Or is it one on the negative and the other on the positive?

thanks for your help....

 

The guy at Radio Shack was correct.

Here's a brief synopsis of parallel and series, courtesy of ASCII graphics (/\/\/\/\/\ represents a resistor):

|----/\/\/\/\/\----|
PARALLEL ---| |---------
|----/\/\/\/\/\----|

SERIES ----/\/\/\/\/\-----/\/\/\/\/\-----

In your case, using 10 ohm/10 watt resistors would yield 5 ohm/20 watts in parallel and 20 ohms/20 watts in series.

 

Electronis 101...

stampsosu,
As egilsrud has explained BOTH MY DESCRIPTION and the RADIO SHACK guy gave you the SAME information.

TWO 10ohm/10WATT RESISTORS IN "PARALLEL" WOULD EQUAL 5ohms AT 20WATTS.

TWO 10ohm/10WATT RESISTORS IN "SERIES" WOULD EQUAL 20ohms/ at 20WATTS.

Read carefully again my post and what you have stated from the Radio Shack guy... WE ARE BOTH TELLING YOU THE SAME THING...

I think your confusion is in understanding what truly constitutes a "parallel" connection and a "series" connection...

1. Two resistors in "parallel" means that the two leads of BOTH resistors are tied together "side by side". (Physically place the resistors side by side and tie the leads of each end of each resistor together). Then one side of a single broken (cut) speaker wire connects to the junction of one side of the parallel resistor network, and the other cut speaker wire connects to the other side of the parallel resistor network junction. This total configuration now gives you TWO RESISTORS IN PARALLEL installed in series with the tweeter.

2. Two resistors in "SERIES" means that they are cascaded together end to end. Meaning that they join together at ONLY one point. Solder one lead of one resistor to one lead of the other resistor, leaving TWO OPEN ENDS. This results in two resistors connected in a "series" configuration. Now connect one side of the broken (cut) speaker wire to one open end of the resistor network and the other speaker wire to the other end of the open resistor network and you now have a total configuration that has two resistors connected in series that are also connected in series with the tweeter.

As for your question as to "what is in sequence"? I'm sure that they were referring to some form of a "series" connection. When it comes to putting a a series resistor combination in series with the tweeter... You could go about it in two ways... You could put one resitor in series with the positive side of the tweeter and another resistor in series with the negative side of the tweeter. This would result in both resistors being in series with the tweeter.... HOWEVER, since speaker connections are not balanced, the best way to do things is to put both resistors together in series first, and then install them in series with the POSITIVE lead of the tweeter. This allows you the option to add an additional rolloff filter cap as described below.

As far as ways to further cut down the tweeters brightness... read again the rest of my previous post. BUT, You now have the opportunity to add a "ROLLOFF" cap. It sounds like you have properly connected the two 10ohm/10watt resistors in parallel... (side by side, with each lead of both resistors soldered to each other and then a speaker lead soldered to each side of this parallel resistor combination.) This DOES give you a 5ohm/20watt network. With that value of resistor, I would go with the rest of my DX6 tweeter rolloff mod. USE A 4.7UF/50VOLT (OR HIGHER VOLTAGE) NON POLARIZED ELECTROLYTIC CAPACITOR. Take this cap and put it directly across the tweeter itself AFTER THE RESISTOR HAS BEEN INSTALLED. Without the resistor, you would short out the speaker at high frequencies and the amplifier would NOT like to see that load!

If you don't have physical space to mount the cap directly across the tweeter... then you can mount it anywhere that is convenient AFTER the resistor. By AFTER the resistor, I mean connect one side of the cap to the side of the resistor that is feeding the tweeter. NOT on the side of the resistor that comes from the amp. Once you have connected one side of the cap to the tweeter side of your series resistor, connect the other side of the cap to the wiring ANYWHERE on the negative side of the tweeter. You can do this at the tweeter itself, or at the amplifier, or at the crossover, or at some point where you splice into the negative wiring of the tweeter anywhere along its run.

This will additionally roll high frequencies off at around another 3db at 8khz and continue at 6db/octave on up past 20khz. The resistor "CUTS" the signal to the tweeter evenly at all frequencies... the cap will "rolloff" signals above a certain frequency and continue to rolloff at a higher rate, the higher the frequency. The stock EQ has a high frequency boost that is NOT linear... meaning it starts to boost high frequencies at a certain point and continues to boost them at a higher rate the higher the frequency. Therefore you need some kind of "reactive" component (capacitor) to effectively compensate for this pre-emphasis curve. You could simply keep adding a higher value of resistor to the tweeter until it's output is knocked further down... but this would most likely produce a midrange "hole" in the signal to the tweeter before you have the extreme highs tamed down to where you want them.

Therefore, the best way to do things is to use the resistor/capacitor (RC) rolloff combination. This more closely follows the contour of the factory EQ and produces a much flatter overall response. Idealy, you would want to counteract the effect of the EQ completely... but in practice, that's really hard to do. You could certainly experiment with SEVERAL values of resistors and caps... (and drive yourself nuts) but I think that you should be in the ball park if you add a 4.7uF cap to your 5ohm/20watt resistor cutdown circuit.

Give that a try and give us a report back... I believe Radio Shack has 4.7uF/50volt NON POLARIZED caps in stock. They are common for crossover networks... Other values will have to be obtained from an NTE distributor.

You could also just use ONE of the 10 ohm resistors in series with the tweeter. This would cut it down a bit more... but again, I think that would also cut down too much on its upper midrange reponse. There are a myriad of combinations available with this technique. BUT TRUST ME... I've spent a LOT of time listening to values and I belive that the 3.9ohm/4.7Uf cap is the best compromise for the DX6 speaker. But in your case, with the tweeter mounted higher in the door, closer to your ears... the larger 5ohm resistor with the same 4.7uf cap should be about right. This will start the rolloff a bit sooner than with the DX6 mods due to the slightly larger resistor, but It should be about right considering the posistion of your tweeters.

As a summary...

1. This total mod will leave you with TWO 10ohm/10watt resistors tied in parallel to create a 5ohm/20watt resistor combo.

2. This 5ohm/20watt resistor combo will be installed "in series" with the POSITIVE tweeter wire.

3. Then an additional 4.7uf/50volt (or higher voltage) NON POLARIZED ELECTROLYTIC capacitor will be installed AFTER THE RESISTOR and "in parallel" with the tweeter. This means one side of the cap is connected to the tweeter side of the parallel resistor combo, and the other side of the cap is connected to the NEGATIVE side of the tweeter or its wiring.

4. This will give you a series/parallel RC single pole 6db/octave lowpass filter rolloff circuit. Simple, but effective.

Hope I haven't further confused you... I always type too much crap to make sure that there are no misunderstandings, only to find that most people get bored and don't read it thoroughly.

Good luck! and THANKS EGILSRUD! something tells me that I'm going to need your ongoing concise help on this one???

Southbound

 

P.S. Your current configuration of using two 10ohm/10watt resistors to create a 5ohm/20WATT resistor should be PLENTY OF POWER. A 20WATT resistor combo shouldn't get hot no matter what aftermarket amp you have. If it does... the DX6s will be distorting long before that. Not knowing the REAL RMS power of your amp, I'd be a bit leary of only moving up to a 10watt resistor... BUT 20 WATTS should have you covered with overkill...

Again, add the cap, and give us a report. I think you'll be really dialed in then!

SB

 

Sorry about that Southbound, I did read your post wrong.... I decided to run two 10watt/10ohm resistors in series on each tweeter. I had them parallel and decided to try the series combo, and it seemed to take away a little more of the tweeters power. It sounds better. I went to Radio Shack and picked up your 4.7uf capacitors. I have not tried them yet. I think they are the right ones. They look like a small "jelly bean" with a wire sticking out of both ends. Is this right? If I am now running two 10watt/10ohm in series on one tweeter, instead of in parallel on one tweeter, would I still need the capacitors? Another question for you....what determines the amount of power that is taken away from the tweeter,,,,the watt# or the ohm #


and again, thanks for you help.

 

stampsosu,
If you now have the two 10ohm resistors in "series"... that means that you have 20 ohms in series with your 4ohm tweeter. (I assume that your tweeter is 4ohms). THIS SHOULD CUT THE TWEETER WAAAAAY DOWN. The tweeter output should now be cut down on the order of 15db! If it's still too bright... I'm amazed at how you tolerated it WITHOUT any resistor?

TO ANSWER YOUR QUESTION...

It is the "ohms" that determines how much resistance the "resistor" has to the flow of electrons. The larger the number of ohms, the more it resists the flow of electons by cutting down the current.

The "wattage" determines how much POWER that the particular resistor can limit before burning up. When a resisor is placed in a circuit to limit current, it dissipates this current as heat. So the amount of power that you are dissipating will determine the amount of wattage that the resistor needs to be.

Example... (I'll make this simple and express it in DC terms... so those of you who understand the difference between ohms law for DC and ohms law for AC, please don't flame me.... I'm just trying to get a simple point across here)

For explanation sake, Say you have a "10ohm" speaker and a "10ohm" resistor being fed by a signal of "10volts"...

In DC terms... If you place the 10ohm resistor IN SERIES with the 10ohm speaker, you will drop the signal voltage to the speaker by half... So ONLY 5volts will now be feeding the speaker and the other 5volts will be dissipated across the series resistor as heat. If you had 20ohms in series with the 10ohm speaker, then you would cut the signal voltage being fed to the speaker down to one/third. So ONLY 3.333volts will now be fed to the speaker and 6.666volts will now be dissipated across the the series resistor as heat.

I'm sure you now get the idea... The LARGER the OHMS the more you cut down the speaker voltage.

In the examples above with ONLY "10 VOLTS" as a signal source, a 5watt resistor would be sufficient to handle the heat that is dissipated across it. This heat is power that would otherwise be feeding the speaker to make its output louder.

Now where does the "Wattage" come into play?

Suppose in the same example above that you now have an aftermarket power amp that puts out a "100Volt" signal instead of only "10Volts"... In this case, putting a 10ohm resistor in series with the 10ohm speaker would still cut down the tweeter output by half. The DIFFERENCE in this case, is that now 50volts is seen by the speaker and 50volts is being dissipated as heat by the series resistor. Power is logarithmic... while the voltage output or relative sound level will drop by half in each example... the example with 50volts across the resistor would now take a MUCH LARGER "WATTAGE" to handle the heat produced by 50volts instead of just 5volts. In fact if you dropped 50volts across a 10ohm resistor, you would need a 250WATT resistor! Where as at 5volts you only need a 2.5Watt resistor... Then double this rating for a margin of safety.

So.... ohms are chosen to attenuate the signal....
and watts are chosen based upon the maximum amplitude of the signal to be attenuated.

So now that you understand how the resistor "CUTS" power to the speaker, you can begin to understand what the cap does.

The resistor cuts ALL frequencies by the same amount. A capacitor has a resistive value that changes depending upon the frequency. So we now have a resistor in series with the tweeter. Now if we "shunt" a cap in parallel with the tweeter, (after the resistor) we accomplish additional signal rolloff to the tweeter. The "farad or microfarad" value of the cap will determine how much more the signal is attentuated. It will also determine at what frequency this extra attenuation begins. The "voltage" of the cap is like the wattage on the resistor... it determines how large of a signal that it can pass before exploding.

In this case... we want to roll off the highs by an additional amount starting at a SPECIFIED frequency. Idealy, we would like this frequency to be exactly where the EQ starts to boost the frequency. However, that information is unkown, and everybody prefers different amounts of EQ, so we are doing this by the trial and error method.

I would think that you would want the additional rolloff to begin somewhere between 5khz and 10khz. THE FREQUENCY AT WHICH A CAP BEGINS TO BECOME RESISTIVE, DEPENDS UPON TWO THINGS...

1. The value in farads or typically microfarads of the capacitor itself.

2. The value of the resistance that it is working in conjunction with.

SOOOOOO.... If you want a rolloff to begin at say 5khz... the capacitance value that you choose will depend upon the resistor that is in series before it. The two components together that form the single order RC low pass filter are a series resistor with a parallel "shunt" capacitor connected to ground (or the negative side of the tweeter) This single order filter will roll off at 6db per octave. Meaning that the voltage will be attenuated by 6db at 10khz, another 6db or a total of 12db down at 20khz, another 6db or a total of 18db down at 40khz...etc.

This RC circuit acts like a simple voltage divider that is determined by frequency.

1. The higher the frequency, the lower the resistance of the capacitor.

2. The higher the value of the capacitance in microfarads, the lower the resistance of the capacitor.

SOOOOO if you NOW put a 4.7uf cap across the tweeter after your 20ohm series resistor... YOU WILL START TO ROLL OFF AT 1.69Khz. This is most likely waaaay too soon. So you need a lower value of capacitor to increase the frequency at which it comes into play. OR else you need to lower the resistor value... AND THIS IS WHAT I RECOMMEND... It's a combination game that you have to play... Also, the LARGER the resistor, the more heat it will dissipate and the larger wattage it will need to be. (FYI,RESISTORS DO NOT CHANGE THEIR RESISTANCE WITH FREQUENCY... they remain constant.)

Therefore, I don't recommend that you stay with the 20ohm combination. This just seems way too excessive. I would go back to your parallel combination of a 5ohm resistor and then put a cap across the tweeter after the resistor. The value of cap you choose will depend upon what frequency the rolloff occurs and will more closely follow the contour of the original boost. this will result in a much flatter overall response, then by simply cutting the tweeter down itself by way too much.

The point at which the resistive "reactance" of a capacitor equals the resistance of the resistor is called the "break frequency". This will give you a signal drop of 3db at that point and then follow a 6db/octave curve from that point onward.

If you go back to the 5ohm/20watt resistor combo and put the 4.7uF cap across the tweeter, you will have a break frequency of 6.8Khz. This means that the tweeter output will be down by an additional 3db from what the resistor alone provides at 6.8khz. One octave above that, or 13.6Khz, you will be down another 6db or a total of 9db from what the resistor alone provides. One more octave above that, or 27.2Khz, (which is way above your hearing range that drops off somewhere between 15khz and 20khz, depending upon your age) you will be down another 6db or a total of 15db from what the resistor alone provides. This "slope" should more closely follow the slope of the original EQ that you are trying to counteract.

You don't want to "suck-out" too much of the DESIRED upper midrange (lower portion of the tweeter's output) in order to tame the extreme high frequencies caused by the overactive EQ.

SOOOOOOOOO.... try the 5ohm/4.7uf mod. This should sound fairly nice. If not... you can adjust the capacitor... A larger cap will roll off the high end sooner and a lesser cap will roll it off later.

Capacitors (unlike resistors) do NOT dissipate heat... that is because the voltage and current are out of phase with each other across the component. BUT THAT IS ANOTHER LESSON... reserved for ELECTRONICS 201.

Also capacitors (unlike resistors) add value by being put in parallel instead of in series...

Two 4.7uf Caps in parallel equals 9.4uf of capacitance. So if you find that the 5ohm resistor combo along with the 4.7uf cap is still not enough rolloff and things are still too bright... You can add two 4.7uf caps in parallel to create 9.4uf. This value will begin to roll things off at HALF THE FREQUENCY of the example in my mod above. So you would be down 3db at around 3.5khz, 9db at 7khz, 15db at 14khz, 21db at 28khz, etc. So you can see that you can come up with many combinations of rolloff curves here.

I would stick with the 5ohm/20watt resistor... This will ensure that things don't get TOO HOT. IF you still want more rolloff, (and it sounds like you do), then add the 4.7uf cap across the tweeter after the resistor. THIS WILL NOT CAUSE ANY MORE HEAT... If that still isn't enough... instead of adding a bigger resistor which will cause more heat... add a larger cap which will start the rolloff sooner.

You can easily parallel two 4.7uf caps to obtain 9.4uf... but I found this to be too much of a rolloff on my DX6s... Your ears may be more sensitive to the highs... or your tweeters may be more efficient... or it may just be the placement of them that makes things overly bright. If the 4.7uf value is not enough with the 5ohm resistor, and the 9.4uf cap is too much.... then you will have to find a NTE distributer near you to buy values in between those two. Some combination will finally hit that "sweet spot" for you...

Whew! Hope things are now more clear for you?

HAPPY HOLIDAYS ALL!
Southbound

 

P.S.
yes, the "jellybean" looking jobs should be the right caps. They should say 4.7uf on them somewhere... they should also have a voltage rating on them as well it will be 50v or 50wv (50volts or 50 working volts) ALSO THIS IS IMPORTANT!!!! THEY SHOULD HAVE A "NP" printed on them somewhere... This stands for NON POLARIZED... You definitely need that or they could short out and blow up!

SB

 

Also, the jellybean should actually be a "CYLINDER" If it's not a true cylinder in shape, then you may have some "teardrop" tantalum caps? Tantalum caps are OK to use, but they are hard to find NON POLARIZED...

The package had to read something. If it read like my post above... you are GOOD TO GO FOR IT!!!
SB