My IB Sub

**toecheese** · **05-16-06, 10:39 AM**

I still haven't balanced it yet, but the IB sub is blowing me away.

The clarity is simply amazing.

For those that don't know- the term IB sub is 'infinitely baffled'.

The design premise is that since a speaker cone moves both forward and backwards, two sound waves are created. For a sub, that's a lot of air volume. To get around this, subwoofers are either 'sealed', which means they end up fighting against a low-pressure zone (lower efficiency and non-linear response) or 'ported', which tries to tune the back wave to something that will enhance a certain frequency range, or push it into a different range.

The reason you can't buy one is that they are all custom built.

An IB sub has its forward wave toward the listening area- and the back of the wave to an area that you don't care about the sound (in my case- my attic). Crawlspaces, storage rooms, large closets, etc. can all be used. There's some formula for determining how large a volume you actually need if you want to use a closet or something, but in general, most people have been able to use unused space.

**toecheese** · **05-16-06, 10:51 AM**

Here's a link to my blog as I was in the middle of installing the manifold:http://farzanegan.org/ht/2006/04/ib-sub.html

(oh, it is pretty much a requirement that you post some kind of picture with heads sticking through a manifold when you build an IB sub)

**toecheese** · **05-16-06, 12:22 PM**

Oh- forgot to mention the other IB advantage- more floor space- no box(es) on the floor.

**JCD** · **05-16-06, 12:38 PM**

Very exciting!

Some general questions:

How did you decide on the spot for the manifold?
Why did you pick the drivers that you did?
What amp did you eventually get?
What size room is it in?

JCD

**toecheese** · **05-16-06, 02:33 PM**

1. How did you decide on the spot for the manifold?
2. Why did you pick the drivers that you did?
3. What amp did you eventually get?
4. What size room is it in?

The ideal spot for any sub (from what I've read; I'm no expert) is centered and equidistant from from the mains. In my case, it is centered right above my center channel, and maybe 18" closer to my listening position.

IB Sub drivers have to be high excursion and need a lot of other parameters to be good. High excursion because there's no resistance on their back-side to keep it from hitting the stops every time. The IB cult has statistics of which ones to use. The ones I picked were cult-approved, and... came out of a buddy's HT he was tearing down

I may need to add two more.

I'm using a Behringer EP2500- a very flexible amp that can be set to stereo, parallel (one input, two outs), or bridged mono (one/one). It can also drive down to 2 ohms, which was important to me as I was considering various ways to wire two or more drivers. Oh, this amp is cheap, too. (got it and the DSP for $400).

The room is about 18x23 with a 10' ceiling. I still don't know if I have enough subwoofer to cover- I'm scouring the cult site to figure out how to calculate how much is enough. I'd simply ask, but I think the cult answer is always 'you need more'.

**JCD** · **05-16-06, 02:44 PM**

Quote:

toecheese wrote:

The room is about 18x23 with a 10' ceiling. I still don't know if I have enough subwoofer to cover- I'm scouring the cult site to figure out how to calculate how much is enough. I'd simply ask, but I think the cult answer is always 'you need more'.

Yeah, I've been there too.. I think the standard answer would be a minimum of four drivers. I think you said you had two, so, I'd look into getting two more at some point. I've got a room that is a bit smaller that I plan on installing an IB in -- I'm goint to start with 2 and maybe move to 4 depending on the sound.

Congrats again.. I've drunk to the KoolAid too, so I should be joining the Cult soon myself -- or at least I hope to.

JCD

**toecheese** · **05-16-06, 04:18 PM**

Yeah, I saw some posting about you need a minimum of 4x12s, but I think 2x15s is the starting point.

I really need to figure out what is proper- just how much SPL do I need at certain frequencies? I think THX has a standard for what is required.

**kingkip** · **05-16-06, 04:27 PM**

Hey guys, I found Unibox and WinISD to be pretty good at guesstimating number of drivers and SPL. Of course add a few DBs for room gain as they simulate an anecholic chamber. The end result is you can never have too many as more drivers will be more efficient and have better sound quality/pressure.

As always, if you are happy with the results then you have enough drivers.

I listend to a friend's IB in a room about your size, and he was running 4 15's. Sound was awesome. Take that for what it is worth to you.

**Derek** · **05-16-06, 10:48 PM**

Hey TC, Ain't IB's the way to go?

I know it's hard to believe, but if you add 2 more 15's the sound will be even cleaner, quicker and more effortless.

I have dual IB's (2x15 each) behind my mains and it rocks!

Word of warning though. I was watching War of the Worlds CRANKED and I got nervous that I'd bottom out the 4 15's (I was also wondering "at what point does drywall crack?"). I'm sure two drivers would have bottomed out. I highly recommend getting two more.

**toecheese** · **05-17-06, 12:34 PM**

Yes, IB is the shiz.

I'm now actively looking for two more. Unfortunately, my manifold will have to be re-done because I didn't plan for it (the cult strongly cautions about this, and I didn't follow their advice).

**toecheese** · **05-17-06, 12:38 PM**

Quote:

kingkip wrote:

Hey guys, I found Unibox and WinISD to be pretty good at guesstimating number of drivers and SPL. .

Where can I find these programs?

**JCD** · **05-17-06, 01:20 PM**

Quote:

toecheese wrote:

Where can I find these programs?

WinISD

Unibox

JCD

**FlashJim** · **05-18-06, 07:28 AM**

IB sounds like the way to go. I wonder if I can hide it from the wife.

Do you have a pic of the grille you used?

**toecheese** · **05-18-06, 08:52 AM**

Grill?! We don't need no....

Actually, working on it right now (put up a frame for it last night). The grill cover is a speaker-cloth coated frame that I'll attach with velcro to the one around the hole. On the cult forum, there are lots of nice examples.

But, yes, IB subs do have a high WAF if you can do the cutting and stuff without them seeing. Because once installed, crisp bass without tripping over anything.

**FlashJim** · **05-18-06, 10:53 AM**

High WAF is needed at my house. I'm sneaking a bunch of new equipment in while she's gone this summer.

If I can hide something, all the better. lol

**hardman** · **05-18-06, 12:17 PM**

Some time back I purchased 2 Dayton IB 12” speakers from Parts Express (these driver are no longer in production) for a dipole bass project that eventually got scraped. I recently bought an LCD TV for my bedroom and am beginning to think a small bedroom theater setup is in order. My room is small, about 8’ X 12’ X 14’, so do you really think I need a 4 driver sub or could I get by with only two?

**JCD** · **05-18-06, 12:23 PM**

Do you know what the xmax is for those drivers?

In any case, I think the general answer is, yeah, you'd need at least 4. I'm sure if you were to ask over at the Cult, they'd tell you you'd need even more probably. This assumes that the drivers are even appropriate for an IB.

Sorry, wish I had better news for you.

JCD

**toecheese** · **05-18-06, 02:18 PM**

Quote:

hardman wrote:

Some time back I purchased 2 Dayton IB 12” speakers from Parts Express (these driver are no longer in production) for a dipole bass project that eventually got scraped. I recently bought an LCD TV for my bedroom and am beginning to think a small bedroom theater setup is in order. My room is small, about 8’ X 12’ X 14’, so do you really think I need a 4 driver sub or could I get by with only two?

I'm assuming since they're IB subs, they'll have decent xmax. But, that is a decent sized space- I think you'll be happy with the clarity, but it won't rattle fillings.

**JCD** · **05-18-06, 03:25 PM**

Quote:

toecheese wrote:

I'm assuming since they're IB subs, they'll have decent xmax. But, that is a decent sized space- I think you'll be happy with the clarity, but it won't rattle fillings.

Duh..

Missed that "IB" thing on the first read.

JCD

**Ayreonaut** · **05-18-06, 05:24 PM**

Boy, you guys are a bad influence.

Someday in the not too distant future I just know I'll end up building an IB sub.

**FlashJim** · **05-19-06, 07:53 AM**

Quote:

Ayreonaut wrote:

Boy, you guys are a bad influence.

Someday in the not too distant future I just know I'll end up building an IB sub.

I feel your pain. I was originally looking at a 12" powered sub. I just bought a pro amp and I'm planning out an IB with 4 15's.

God help us all. lol

**toecheese** · **05-19-06, 10:55 AM**

In honor of this thread- and showing pictures of my IB sub covering, I've updated my blog:

http://farzanegan.org/ht/2006/05/ib-sub-and-waf.html

**JCD** · **05-19-06, 12:28 PM**

Quote:

From The Blog wrote:

In my case, the whole WAF thing is false. Stefanie wanted *bigger* speakers in the living room. I was going to move the speakers that were there into the home theater, but they weren't big enough so we had to get new ones.

Toecheese, that is a mighty fine woman you have there.

And great blog BTW.

JCD

**ctbennett** · **09-01-06, 03:49 AM**

My room is similar size and I am using a single Soundsplinter RL-s15, 22 cu ft enclosure, Behringer 2500 and DSP1124. I was concerned if one 15" was enough. That was a wasted worry. It is basically flat to 22Hz and output has no limit and incredibly low distortion even at 120 db.

**Chrisbee** · **09-01-06, 06:31 AM**

Quote:

ctbennett wrote:

My room is similar size and I am using a single Soundsplinter RL-s15, 22 cu ft enclosure, Behringer 2500 and DSP1124. I was concerned if one 15" was enough. That was a wasted worry. It is basically flat to 22Hz and output has no limit and incredibly low distortion even at 120 db.

That is an incredible perfomance for one driver in an IB!

From my own experience muting two of my four 15" really takes the wind out of it. The Soundsplinter drivers have around 50% more Xmax than my AE-IB15s though.

I can easily get 120dB (uncorrected RS meter) in the audible range with virtually no cone movement at all in my 30 foot room open on two floors.

Recent changes mean my IB perfomance has finally gone into overdrive. The EP2500 needs enough signal to reach its full output capability. It needs at least another 6dB over a typical streo preamp output (and preferably more) just to thrive and develop real muscles.

The lightening speed and low distortion is unbelievable on films like LOTR. The floor literally feels as if its been smashed with a very large hammer in scenes where castle gates are being destroyed. I am well used to floor effects from my SVS but they were always soft vibrations and completely unlike the vicious impacts I'm getting now!

The Mount Doom (ROTK) scenes with lots of heavy bass effects are almost unbearably powerful. I keep asking myself if I dare to continue or should I grab the remote before the house literally collapses around me! My wife told me the boarded ceiling was vibrating madly in the kitchen downstairs! Luckily she is usually amused by these things.

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