I hate cars

I have the new carpet but haven't trimmed it to go around the baffle yet. I'm hoping it fits better but I was kind of waiting to make sure I don't change the setup again. I also bought all new hardware from Acura to hold the carpet into place. Hopefully it's worth the expense.

Majofo

IHC, what about a single 12 IB setup? btw.. did you modify the rear deck at all? dynamat / particle board?

Majofo

eggyhustles

Means it's time for louder mids

Kidding.

I think mine could do the same..never tried it since it gets way too loud in the cabin.

I hate cars

A little dynamat. I filled the deck with expanding foam which most people aren't willing to do. I plan to keep the car until the wheels fall off and maybe give it to my niece when she turns 16 so I'm not worried about resale value but I can see why many people don't want to do that. No rattles at all.

I did a single 12, it sounded great. You're going to have the same output potential as sealed, just much less power required and a flatter response as well. I was extremely happy with it and it got plenty loud but I always have to go for overkill.

I hate cars

You figure it takes about 190w to hit xmax at 20hz, 120w is pretty loud. Yeah, I don't think I'll be adding to the front stage anytime soon. For once I'm power limited and not displacement limited at any reasonable crossover point. I upgraded the hardest working speakers, the midbasses, and now excursion is really low on all speakers even when it's loud.

eggyhustles

cone area>power

every day.

So yeah..win.

Majofo

niebur3

The one thing to remember is that you may have the same output potential as sealed in an IB and much less power required (not necessarily a flatter response, just the rolloff will begin lower in the frequency response over a sealed), but if the sub is not ideal for IB (having too high Fs or too low Qts and not enough Xmax), it could just as easily disappoint. If Fs is too high, the bottom end could sound exaggerated. A Qts that is too low could cause the woofer to suffer without the control (air spring) that the box gives.

rich20730

Majofo

fantastic.. damn IHC.. how many people have you influenced to do IB setups.. must be over a dozen and growing.

rich20730

Definitely where I got my inspiration

pohljm

^ add another!

xxx_busa

I'll show you the Junk in my Trunk !!!

eggyhustles

win win win

Trunk Monkey

iTrader: (1)

IB sucks

rich20730

Irritable bowels?

Trunk Monkey

iTrader: (1)

Yes.


Dammit those 2 IDmax's look good

rich20730

Your idmax is lonely. It needs a buddy.

niebur3

^^Man, you need to clean that half torn sticker off the passenger side sub magnet. That's just sad!!! I say it's Esotar2 abuse and I am confiscating your 2nd sub...lol!

I hate cars

It seems like a lot so far. We have to have one of the highest percentages of IB subs for a car community. I actually got the idea from member "Neel" from a long time ago with his old school IDQ15s. I heard his TL at a meet several years ago and was hooked. It was one of those humbling times when I showed up thinking mine sounded great and went home wanting to rip it out and start all over again. I started researching IB immediately when I got home.

The bad thing is everyone that did IB after me has a better looking system lol. I really like the dual IDMaxes and the single and dual Dyn 1200s.

My theory is anything that will sound good sealed will sound as good or better IB. I could be wrong though. So far I've found nothing that sounds worse in IB. I did so much reading early on trying to decide on Qts, Fs, and all of that stuff and the only conclusion I came to is just about everything will sound good in IB if it sounds good sealed and sometimes you just have to try it. I need to dig up that email from JL Audio saying you can't use the 12W6 IB lol.

As for the Qts, the lower the Qts the better damped the sub is. A small sealed box has the least damping. IB has the most damping. I think that's why a small box sub has a low Qts, it's very well damped because it's going into an enclosure with very poor damping. Maybe that's why you lose just a little efficiency with a low Qts sub in an IB setup, it's critically damped.

Small boxes reduce efficiency and they actually give less cone control. That's why I will never do a sealed setup if I'm able to do IB, ported, or BP. I will never see the point of mechanically reducing efficiency to control excursion instead of doing it electrically with a highpass filter and retaining efficiency.

I know everything I say is contrary to what's been taught since the beginning but I think IB is more forgiving of most specs. It's going to sound good with low or high Qts subs and you can shape the sound easily with EQ and still be much more efficient than sealed. I've found low Qts to dig deep and have a "tighter" and "quicker" sound at the cost of a slight loss in efficiency.

I think shooting for a critically damped Qtc of .5 is best in a lot of cases. The sub starts and stops as quickly as possible but without overhang so bass is quick and tight and you don't lose too much efficiency or low end. I think mine with the pair of .46 Qts subs give about a .6 in my trunk and I've removed the outside vent flaps to hopefully lower the Qtc even more by making the trunk look larger to the subs. I don't get the reasoning behind the whole .707 Qtc thing.


With IB and Sealed, SPL is determined solely by displacement assuming the sealed setup can hit full excursion before it hits it's thermal limits. So if there's not enough xmax in IB, there won't be enough when sealed either. That's assuming the highpass if properly setup. That's why I like a lot of cone area, I can do a really low highpass with a shallow slope for the really, really low stuff and still have decent SPL at all frequencies.

I'm guessing but if Fs is too high for IB, it's probably going to be exaggerated in sealed box, right?

Now after saying all of this I bet my next car is going to accept nothing but a sealed box.

It's fun looking back through the years with these setups. We've had a few good ones over the years like Chico OG and Death to Toasters but lately with Jerry's and just about everyone's IB install, I think it's been taken up a few notches over the old days.

I must be really bored tonight lol.

I hate cars

How happy are you with the overall sound and output of the dual IDMaxes? Those bad boys should give you the output of 3 "normal" 12s.

I hate cars

IB envy.

Come on, everyone else is doing it. You know you want to do it. Just try it once

Majofo

My next project, as soon as I figure out my 1st - 2nd issue. btw.. I posted a viz message on your page regarding the front mount. I'm thinking of going with a solid mount instead of OE. Thoughts?

I hate cars

Sorry, I check the messages on my phone but I can't reply and then I forget about them by the time I get in front of a computer. I apologize for that.

Are you talking urethane or an actual solid mount? Solids will give crazy vibration, not something I would do in a street car. What I've always done is replace the rubber mount with urethane on the side that lifts up and keep the stock rubber mount on the side that compresses on acceleration. So if the TL's engine rotates clockwise like most do the rear mount if it had an actual rear mount would be beneficial. That's just my opinion, I think it gives the best bang for the buck and comfort. I've never even looked at the Tl's mounts other than the front but we don't have an actual "rear" mount, do we?

As my other car got quicker and quicker, even with brand new mounts, since they were captive mounts meaning if they broke, there was a metal hook to keep the engine in place under power, it would still stretch the mount out to the point it went metal to metal. When it did that the first time I thought my engine was coming apart due to the vibration. Solid mounts really suck lol.

Of course, it will likely hurt nothing and some people are fine with the vibration. I get annoyed with vibration really easy, my age is really showing.

Majofo

no no no no...

I meant solid rubber over the "hydraulic" mount. I think it's the same style mount in the rear, MT owners have a damper. I expect a little more vibration over the OE mount, but hopefully nothing too drastic.

niebur3

Here is some good reading regarding a Critically Damped Vs Underdamped Vs Overdamped. Again, I think the driver still needs to be selected carefully for IB installation.

"Damping & Q
Before we define Q, let’s think about a car again. All automobiles have a suspension which prevents bumps and dips in the road from jarring the passengers. However, a car cannot use a spring suspension by itself because the car would continue to bounce (resonate) after each bump or dip. The bouncing needs to be suppressed and this is what the shock absorbers or dampers do. They suppress the unwanted bouncing after the springs have absorbed the initial impact of the bump or dip. In similar fashion, a speaker driver needs to be damped. Otherwise, its diaphragm will tend to vibrate excessively at its resonance frequency.

Several things serve to damp the driver. These include the suspension (surround and spider), motor (voice coil and magnet circuit) and amplifier output resistance. Achieving an optimal amount of damping can sometimes be a challenge and it almost always requires a consideration of the type of box in which the driver will be used. If the driver is not designed properly, it may be underdamped or overdamped. An underdamped driver will have ripples in its response and it will reproduce transient signals poorly. An overdamped driver will have a reduced low-frequency response.

"Q" is the term used by speaker designers and engineers to describe how well damped a driver is. However, Q is not damping. Instead, it is resonance magnification which is the exact opposite of damping. So a higher amount of damping results in a lower value of Q and visa versa. Let’s return to our earlier graph:



The driver which was used to create this graph has a total Q (Qts) that is super low at only 0.19. This low Q value results primarily from an extremely strong magnet and this driver by itself would be considered severely overdamped. To get a maximally flat response out of it we had to counteract some of the damping by stiffening the overall compliance. We did this by putting the driver in a relatively small box having an air volume with a much smaller compliance than the driver suspension. This caused the overall compliance to decrease considerably and the total Q (Qtc) to increase to 0.7 as shown in the green curve in the graph. A Q of 0.7 is considered by many to be the ideal value because it balances driver damping with a smooth low-frequency response and a reasonably good transient response.
The red curve was created with a huge box whose volume was over 100 times larger than the maximally flat box. As a result, the box has a very high compliance and so it could not stiffen the compliance of the driver much at all. In fact, the total Q was 0.2 which is just slightly greater than the driver, itself. Because the total Q is allowed to remain so low, the design is considered overdamped. Notice how it produces less low-frequency amplitude between 95 and 400 Hz. You might consider its greater output below 95 Hz to be an advantage but this is probably not the case because the driver would have to move a tremendous amount of air at these low frequencies and its maximum excursion (Xmax) may not be large enough to handle this. If it is not, it will at best have higher distortion and at worst become damaged.

The blue curve was created with an ultra small box whose volume was over 25 times smaller than the maximally flat box. As a result, the box has a very low compliance and so it stiffened the compliance of the driver by a very large amount. In fact, the total Q was 3.0 which is quite high and causes the box to be underdamped. Notice how it produces a 9 dB response peak that is centered at 580 Hz. The peak occurs at this frequency because the low compliance of the box has in effect shortened the spring, raising the resonance to 580 Hz. The peak is 9 dB high because the driver lacks sufficient damping to overcome its resonance. This means that the driver will ring like a bell at 580 Hz. Needless to say, it will also have poor transient response at this frequency.

Note: The compliance of the driver and box are in series with each other but they sum in parallel like capacitors so the sum is always less than the lowest of the driver or box compliance values. In other words, the lowest compliance dominates the system. With the red curve, the box had a compliance that was much higher than the driver and so the driver’s compliance was dominant. Therefore the total compliance was not influenced much by the box. However, the box of the blue curve had a compliance that was much lower than the driver, and being the lower value it became the dominant one and caused the total compliance to appear to be much lower."

This was an exert found here:http://www.ht-audio.com/pages/SpeakerBasics.html

rich20730

Good read! I think this stuff is finally starting to come together for me. Still seems to me like the red curve (IB) would be the ideal scenario. I would consider more low end capability to be an asset rather than a liability. Like IHC said, if you don't have a high xmax sub and are worried about over-excursion on the low end you can just set a high-pass/subsonic appropriately to match the response the speaker would have in an enclosure.

niebur3

I would honestly be real careful trying to implement a really low QTC woofer in IB (.4 or less). I like the .5 Matt talks about (not a huge fan of .707 either). That is a good number. The car itself will change that number some, but that is a good number to shoot for.

I hate cars

The main point I was trying to get at last night is that the air spring of a box actually decreases cone control and reduces efficiency on the low end. I see I stated all the time that the box helps with cone control when it does the opposite. This is mainly centered around what I read on diyma all the time but whenever someone challenges their opinions they will turn it into a religious and or political thread to stop the exchange of information. I guess it's pretty obvious I'm getting sick of that forum. Maybe if I'm feeling up for it I might post the cone control thing in the myths section and watch the chaos. Thanks for the link Jerry.

Would you agree the main/only disadvantage of critically damped is a slight loss of efficiency? One of the many reasons I like the Esoar 1200 is the low Qts in the .3 range.

rich20730

I'm confused. When you say you would be careful implementing a low QTC woofer in IB, is that for sound quality reasons or because of potential damage to the driver?

Wouldn't a low QTS/QTC woofer have more cone control due to a stronger motor/stiffer suspension? It doesn't seem like those characteristics would make it more susceptible to damage. I would think that Xmax/Xmech would be the only relevant specs in this respect.

As far as sound quality goes, if the air spring from a smaller enclosure increases the compliance of a driver then I can see how it would make sense that a high Q (underdamped) woofer might not be a good IB candidate due to lack of cone control, but it does not make sense to me the other way around.

niebur3

I have talked with several very well know "expert competitors" and from our conversations, air spring does control the cone. The size of the enclosure dictates how much control there is. Here is a great write-up from JL Audio:

http://www.jlaudio.com/header/Suppor...ristics/287536

I would say loss of output is only one of 2 disadvantages I have noticed with critically over-damped. Also, I notice the impact is lacking.

I would like to talk to you over the phone, Matt, about the Qts of .3 with the Esotar2 1200 and what I have noticed. I think you have my number still.

niebur3

I have noticed that critically over-damped sub have very little impact, that is the only sq reason. As far as damage, if you lose efficiency due to the low QTS/QTC, and you try to make up for that by adding power, you run the risk of running out of xmax and damaging the speaker.

I would say it depends on how many drivers you are using as well. 2 subs critically under-damped should still have enough output (making up for the loss of efficiency), reducing the need to push the sub to Xmax limits as well as potentially increase QTC due to having 2 Subs sharing the same trunk.

rich20730

Below what QTS would you consider critically over-damped? The IDmax has a QTS of .34 and it isn't lacking in impact.

Regarding efficiency, it seems like you would only be making it more inefficient by reducing the enclosure size. Wouldn't IB allow you to use less power to reach Xmax?

Majofo

I'm lost.. I can design you guys a filter though

niebur3

Well, technically anything below .707 is consider critically over-damped. It doesn't mean you won't like it under that number.

If you read that write-up that I posted again, you will see as it becomes more and more under-damped, efficiency starts to drop. Here is the modeling in WinISD of a sub with a QTS of .34 in IB vs Sealed at .707 QTC.


Remember, the QTS and QTC are virtually identical with IB, so if the sub (made specifically for IB) has a QTC of .5-.7 to start, it will more resemble the sealed enclosure I showed above in IB.

Also, the lower end is more extended with IB (according to WinISD) but you can still achieve a flat response with cabin gain.

niebur3

I think most people really like the sound of IB because they are used to the severely under-damped sound many manufacturers recommend (and subs are designed for). Many manufactures tell us to put their subs is boxes that are waaay to small in order for the sub to reach the power handling numbers the manufacturer claims. Most people are used to subwoofers that sound like the blue line:



In order to achieve something more flat, you would be required to build a much larger enclosure, which also reduces power handling (again, this all is dependent on the QTC of the driver). If the enclosure need to be too large, then IB is a great option. But I would look at each sub individually before assuming it will sound good IB.

rich20730

Okay, I need to make sure I have my terms straight:

Under-damped = High QTS
Over-damped = Low QTS

You said as it becomes more and more under-damped (high QTS) efficiency starts to drop. Did you mean over-damped?

In that chart, I'm assuming IB is green and sealed is yellow?
If so, I can see that there's a tradeoff. In IB you're getting a better low end response (Under 40hz), but you're not getting quite as much output between 40hz and 200hz.

Could you not just set a high pass filter on the IB to match the response of the sealed enclosure?

xxx_busa

getting picking on those micro fine details Jerry ! I'll clean it - Just for You !

niebur3

Sorry, you are correct about the under-damped, over-damped definitions. Made a typo and didn't proof read good enough.

Yes, Green is IB and Yellow is Sealed. You would have to eq the IB to match. Setting a filter only drops the bottom off, it won't raise anything.

Then it comes back to what effect does lack of air spring have on the woofer? You can set a filter and eq to match the projected frequency response, but the QTS of the speaker isn't changing and is still considered Over-damped and should follow the characteristics of an over-damped enclosure.

Again, multiple drivers would raise the QTS and would be the best way to go if using low QTC drivers IB (IMO).