How to choose a subwoofer?

**ElectroKinetic** · **01-29-09, 12:11 AM**

I can't seem to find a definitive answer about what parameters to look for when choosing a subwoofer for an IB system. So far this is forum has the most info I've ever seen on the subject.

While expect the results to far from ideal, I would like to try and build an IB system in my car using the trunk as the box.

**Mike P.** · **01-29-09, 01:09 AM**

There are IB specific subs. Fi Car Audio has a line of IB3 Series and Exodus Audio has the DLP-10 and DLP-15. Links to both sites are at the top of the page and the WinISD files for all of them can be found here:

http://www.hometheatershack.com/foru...pro-files.html

**ElectroKinetic** · **01-29-09, 09:31 AM**

Thanks for the info!

**ripcard** · **01-30-09, 03:51 PM**

The Exodus Audio link on this board brings you to the DIYCable site, which itself seems to be stale. There is still a notice about Holiday hours on its front page. Anybody know what's happening?

**Mike P.** · **01-30-09, 04:33 PM**

Kevin from Exodus Audio is a one man operation and lately he has been swamped. I'm sure he'll update his site soon.

**ripcard** · **01-30-09, 04:45 PM**

So, is that to say Exodus Audio and DIYCable are one and the same?

**Mike P.** · **01-30-09, 05:19 PM**

**Kevin Haskins** · **01-30-09, 05:22 PM**

Hey... everyday is a holiday around here.

Kevin Haskins
Exodus Audio

**Bent** · **01-30-09, 07:02 PM**

as a business, it is good to be swamped.

**ripcard** · **02-01-09, 05:26 PM**

Thanks, for the replies folks. Hi Kevin. I'm doing a little research into the IB sub thing and being in Canada I would prefer purchasing here if I can. I noticed over at Cult of the Infinitely Baffled that the FiAudio units are very popular. Can you folks point me to some example IB builds using the Exodus drivers?

**ripcard** · **02-03-09, 08:41 PM**

Quote:

ripcard wrote:

Can you folks point me to some example IB builds using the Exodus drivers?

Anyone?

**salvasol** · **02-03-09, 09:26 PM**

Quote:

ripcard wrote:

Can you folks point me to some example IB builds using the Exodus drivers?

Did you check here

**ripcard** · **02-04-09, 07:10 AM**

Yes, all listings under the Exodus heading are box subs.

**ElectroKinetic** · **02-09-09, 10:21 AM**

I found the answer I was looking for on this page: http://www.caraudiomag.com/specialfe...box/index.html

"When purchasing IB speakers, keep in mind the following parameters to assure that the speaker is right for the application. The first is the Qts (the total resistance of the driver at its resonance). Speakers with a Qts greater than 0.6 typically work well in an IB environment. The second is the Vas (the volume of air having the same compliance as the driver's suspension). The Vas should be smaller than the total volume of the environment the speaker(s) are being placed in."

The page also states that a IB setup is only about 50% efficient. Is this true?

**Darren** · **03-14-09, 10:52 AM**

I have 4 RL-P 15" drivers in my IB subwoofer... nothing I've ever heard can touch it. 120db at 10Hz fifteen feet away says it all

http://www.soundsplinter.com/rlp15_s...formation.html

See my build here: http://www.garagehobbies.com/ib.aspx

Darren

**ripcard** · **03-14-09, 11:59 AM**

Very nice, Darren. I like the fact that you rounded over the edges of the manifold, even though it can only be seen in the attic. I imagine it was much nicer to handle while wrestling it into place on the supports.

**aNomad** · **03-20-09, 12:50 PM**

To answer the original question, think of an IB as a "boxless" loudspeaker. The "enclosure" basically is nothing more than something to hold the driver in place, and block immediate sound waves from the rear of the driver so they don't cancel with the front. For this reason, the bigger the box (or baffle), the better.

To determine the best parameters for an IB speaker, it's helpful to look at what a sealed box does for / against the response. Putting an enclosure on a driver raises the Q of the system. The smaller the box, the higher the Q. This has the effect of raising the output response at F3 (a good thing) but raising it and causing a steeper rolloff below that (a bad thing). An ideal speaker response will have a Q of around 0.707 (butterworth response). Since the enclosure raises the Q, and hopefully approaches 0.707, the closer to that Q you can get with the driver alone, the better for an IB system.

Also, since the idea is to get deep bass, a low Fc is helpful. The most efficient way to get that is to have a large Vas (equivalent volume); that means a soft suspension. Since it will have to move a LOT to get deep bass, a long Xmax is needed, as is a large Sd (diameter), or multiple drivers (or both). Unfortunately, a long Xmax and a large Vas is a recipe for voice coil rub, so it's difficult to find that combination. Go for a large Vas (and correspondingly low Fc), and large piston over large Xmax.

Oddly, these parameters are the same as a sealed box driver, except for the Q. The motor will reduce the Q, so a strong motor is antiproductive for a good response in an IB system, where it is a boon in a sealed box system; so yes, it pays to get drivers made specifically for IB systems. They are rare, so will cost a pretty penny. Good luck!

**looneybomber** · **03-21-09, 04:53 PM**

Quote:

aNomad wrote:

Oddly, these parameters are the same as a sealed box driver, except for the Q. The motor will reduce the Q, so a strong motor is antiproductive for a good response in an IB system, where it is a boon in a sealed box system; so yes, it pays to get drivers made specifically for IB systems. They are rare, so will cost a pretty penny. Good luck!

Not necessarily. The AE IB15, has a .7Qts with an fs of 16hz and a VAS in the mid 400L's, however an xmax of 18mm I think. Real nice option and is 125/ea if you buy 4.

**dgilme** · **04-14-09, 10:01 PM**

Quote:

looneybomber wrote:

Not necessarily. The AE IB15, has a .7Qts with an fs of 16hz and a VAS in the mid 400L's, however an xmax of 18mm I think. Real nice option and is 125/ea if you buy 4.

Plus they are pretty efficient so you can lots of them easily

**ripcard** · **04-15-09, 07:49 AM**

Quote:

dgilme wrote:

Plus they are pretty efficient so you can lots of them easily

What ???

**dgilme** · **04-15-09, 08:21 AM**

Quote:

ripcard wrote:

What ???

That is what I get for posting and talking to my wife at the same time.

I meant they are pretty efficient and low power requirements. So you can run quite a few of them off a modest amp.

**ripcard** · **04-15-09, 08:59 AM**

Ok, thanks. Still trying to get my head around the IB thing and couldn't fill in the blank myself. Do you think an EP1500 could power 4 of these or would you need an EP2500?

**dgilme** · **04-15-09, 09:18 AM**

Quote:

ripcard wrote:

Ok, thanks. Still trying to get my head around the IB thing and couldn't fill in the blank myself. Do you think an EP1500 could power 4 of these or would you need an EP2500?

I modeled 4 IB15s in WinISD. Using an 18hz high pass and they reach max excursion at 20hz with 563 watts using a 16hz high pass they need 430 watts. Pretty sure an ep1500 would be over kill. But it gives you room to grow. You can power all 4 of them from one channel, and if you want to add 4 more later the other channel of the ep1500 can handle them

You could probably power all 4 of them from an O-audio or pe 500w plate amp.

Depending on how tight your budget is will determine what amp you want. Don't forget with a pro amp like that you'll need something to act as a high pass filter. The plus side of the AE IB15s is for a pretty good response you don't really seem to need an eq, although I'm sure it would help alot to make up for in room dips. That is the nice thing about the plate amps, they usually have a high pass built in. But the negatvie is alot of them have low end boost that can change the cone excursion down there. You could buy my o-audio 500w bash amp, wanting to upgrade to an ep1500

You can also post over in the AE forums, Simon5 and John are pretty helpful. You can give them your specific goals, room layout, budget etc and they can give all sorts of details about how the IB15 will perform and what gear will bring the most out in it for you.

**ripcard** · **04-15-09, 12:00 PM**

Hey, thanks alot for the detailed info. I'm just starting my build to complete my HT system (Dynamic 2CC and a pair of 1Ss to complement my mains). The IB will come after that but I'd like to try and sort out what my best solution might be for LFE, so all advice is greatly appreciated. I realize a lot more detail will have to be provided about my specifics for anyone to go into detail, but just understanding the general concepts around a good IB setup will help me make a few choices as well as satisfying my curiosity.

I'll continue to lurk and learn and once I have more of my goals and budget nailed down, hopefully, I can ask the right questions.

**dgilme** · **04-15-09, 12:32 PM**

If you haven't checked out the Cult yet, head over to http://ibsubwoofers.proboards.com/index.cgi.

LOTS of IB information.

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