Infinite Baffle Question(s) - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 26 Old 02-15-2017, 08:34 AM - Thread Starter
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Infinite Baffle Question(s)

Hello fellow DIYers,

I have my mind set on doing an IB sub for my basement HT, reason being is I have electrostatics for mains and think that sealed or ported mix with their sound like oil and water.
The only bass solution I have heard that mates well with ESLs is a transmission line, but making a t-line for each of my SI 18s is an utter impossibility, so IB it's going to have to be...

Now onto the problem:
There's only one spot to place this ceiling/floor IB, and need to put all 4 drivers there.
Side note: I have done MLP listening test for response, and this spot works excellently, guess I lucked out.

What I want to do is place two 18's inside the manifold, and place the other two outside, facing in, reversing the phase on the one pair.
Does anyone see an issue doing it this way?

All help, further questions, and comments welcome..

Actually, I love tube amps..
I play guitars through them.
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post #2 of 26 Old 02-15-2017, 08:42 AM - Thread Starter
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I guess I could place all of the drivers facing inwards, but can the manifold be a mere 20.5" on each side? hmmm...

*edit* I'd actually prefer to go with my original idea, but this second one would work if I had to make it work

Actually, I love tube amps..
I play guitars through them.
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post #3 of 26 Old 02-15-2017, 09:43 AM
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Your original idea will work. Still probably better to do two manifolds, two drivers each if you can fit it.
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post #4 of 26 Old 02-15-2017, 09:44 AM
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Quote:
Originally Posted by wreckingball View Post
Hello fellow DIYers,

I have my mind set on doing an IB sub for my basement HT, reason being is I have electrostatics for mains and think that sealed or ported mix with their sound like oil and water.
IB is essentially just a large sealed box. So, if that is your only consideration then some sealed or ported boxes might be easier. Personally, I'd give ported more consideration but that's just me.

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Originally Posted by wreckingball View Post
I guess I could place all of the drivers facing inwards, but can the manifold be a mere 20.5" on each side? hmmm...
A 20.5x20.5 opening will be fine.

Quote:
Originally Posted by wreckingball View Post
*edit* I'd actually prefer to go with my original idea, but this second one would work if I had to make it work
Either should work fine. You can find examples of both. I would mount all drivers the same. Again, go with the least complicated one.
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post #5 of 26 Old 02-15-2017, 10:29 AM - Thread Starter
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Originally Posted by Jk7.2 View Post
Your original idea will work. Still probably better to do two manifolds, two drivers each if you can fit it.
Your first sentence is what I was interested in, will it work? ...you are saying yes, that's good.
Unfortunately I can't do two manifolds, there simply isn't the available (read;usable) space on the main floor, if I could I would, believe me.

Is there a preference on which pair to put out of phase? I'm assuming the pair on the outside, but would like a second opinion.

Actually, I love tube amps..
I play guitars through them.
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post #6 of 26 Old 02-15-2017, 10:44 AM - Thread Starter
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Quote:
Originally Posted by cmryan821 View Post
IB is essentially just a large sealed box. So, if that is your only consideration then some sealed or ported boxes might be easier. Personally, I'd give ported more consideration but that's just me.

A 20.5x20.5 opening will be fine.

Either should work fine. You can find examples of both. I would mount all drivers the same. Again, go with the least complicated one.
An IB may be just a large sealed, but there really is no 'spring' at work here, (other than the driver's suspension) which gives the characteristic sound of a sealed box imo... Ported sounds less like that, but still has a resonance that can be heard, unlike a t-line's sound, which has far less (and hopefully an IB)

On the manifold being fine that size, good to know, but putting all the drivers on the outside brings the whole thing another 20" out into the room. That's going to interfere with my ESLs, unfortunately..
I'm having to do a more complicated setup due to space restraints.

I really do appreciate the reply though...thanks..

Actually, I love tube amps..
I play guitars through them.
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post #7 of 26 Old 02-15-2017, 10:59 AM
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Where are you planning to install the sub, in the ceiling, in the floor, or through a wall?

I installed mine in the floor and it essentially took op no space in the room. Don't know if it matters, but I wired the woofer that was mounted facing away in reverse. I would have faced both towards the listening room, but there was a brick wall in the way. It hit hard, but had a terrible null at 50 Hz, so I would recommend doing a test sweep with REW before installing something permanent if you haven't already.


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post #8 of 26 Old 02-15-2017, 12:13 PM - Thread Starter
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Originally Posted by action_jackson View Post
Where are you planning to install the sub, in the ceiling, in the floor, or through a wall?

I installed mine in the floor and it essentially took op no space in the room. Don't know if it matters, but I wired the woofer that was mounted facing away in reverse. I would have faced both towards the listening room, but there was a brick wall in the way. It hit hard, but had a terrible null at 50 Hz, so I would recommend doing a test sweep with REW before installing something permanent if you haven't already.
It's being mounted in the basement ceiling, vented into main level through ML floor, and is for the basement HT. (an 'innie' as they call it over at the cult). I always laugh at that...

I didn't do a test with REW, just a dB meter. I can REW it before the actual install to double check, but that's the only place I have to work with, there is no other alternative.

Thankfully, both my ears and the dB meter told me the lowest two octaves (15-60Hz) are fairly even and good response in that spot.
I'm pretty certain I could utilize room treatment to even it out further, but it's really good as-is...

Actually, I love tube amps..
I play guitars through them.

Last edited by wreckingball; 02-15-2017 at 12:17 PM.
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post #9 of 26 Old 02-15-2017, 01:31 PM
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Okay, so an innie would appear to just be a hole in the ceiling of your basement theater and you will have a cube in the living room with massive speakers poking out? Or do I have that backwards?


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post #10 of 26 Old 02-15-2017, 01:35 PM - Thread Starter
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Lol, not sure if you or I have it backasswards, but no, the manifold will be in the basement, and it's for the basement.

Actually, I love tube amps..
I play guitars through them.
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post #11 of 26 Old 02-15-2017, 01:52 PM
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Infinite Baffle Question(s)

Lol, that makes more sense! Since it is going to be visible, I would try to have all the woofers facing into the basement. I think the SI 18 has a 10 inch mounting depth, so the box would need to be slightly larger to accommodate all the voice coils. Maybe a rectangular shape would work if you had a little more room one way but not the other. At least that way you would not see the baskets and wires hanging out of the box.


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post #12 of 26 Old 02-15-2017, 02:56 PM
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Quote:
Originally Posted by wreckingball View Post
Lol, not sure if you or I have it backasswards, but no, the manifold will be in the basement, and it's for the basement.
Actually I think that's called an "outie". This is a pic from the Cult, looks nice.



http://ibsubwoofers.x10host.com/page4IB-Gallery3.html
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post #13 of 26 Old 02-15-2017, 07:41 PM
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An open baffle woofer/subwoofer mates ideally with planar dipole speakers but are practical only down so low. What is the lowest frequency you want your ESL to cover, and how low is your target for subwoofer response?
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post #14 of 26 Old 02-16-2017, 06:17 AM - Thread Starter
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Originally Posted by Bigus View Post
An open baffle woofer/subwoofer mates ideally with planar dipole speakers but are practical only down so low. What is the lowest frequency you want your ESL to cover, and how low is your target for subwoofer response?
Understood. But I don't see the need for open baffle, as my ESL (DIY) plays down to 200 Hz.

What I am doing here with an IB, is the HT portion of bass in an HT/Music setup.
As said, ESLs play down to around 200Hz, and I have 2 10" drivers in two 8' folded t-lines that take over from there, that's what I use for music. (t-line exit faces wall, so pseudo dipole i suppose)

However, for movies and such, the t-lines are not quite enough, so I will x-over the t-lines @ 60Hz (HPF), and have the IB take over bass duties from 60Hz on down.

It's complicated I know, but it allows for this dual-duty setup I have.
If the sound of the IB is good enough, I just may keep this setup for both music and movies, but I doubt it, I like a more pure stereo setup for music, and the t-lines are fine for that.

Actually, I love tube amps..
I play guitars through them.
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post #15 of 26 Old 02-16-2017, 07:31 AM
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Originally Posted by wreckingball View Post
Understood. But I don't see the need for open baffle, as my ESL (DIY) plays down to 200 Hz.
Open baffle/dipole has benefits in both upper and lower frequency ranges. The primary potential benefits of using open baffle woofers below 200Hz are (1) better matching of the ESL polar response, and thus smoother system power response, which has been generally demonstrated to correlate well with increased subjective quality of the system, and (2) decreased excitement of room modes substantially increasing the likelihood of smooth bass at the main listening position and smoother average bass across multiple positions. Other claimed benefits like "no box sound, no backwave" etc I think aren't worth thinking about because even if there were some truth to that it is offset IMO, particularly at low frequencies, by the increased displacement and therefore distortion required to reach a certain SPL. This is best offset with multiple drivers, not longer stroke.

But dipole bass from 60Hz to 200Hz is quite doable. Results from a pair of 10's would probably be suitable for all but the most demanding content.
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post #16 of 26 Old 02-16-2017, 02:21 PM - Thread Starter
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So getting back to the IB, I did some more physical measurements in this spot, and must go with my original plan, I'm just going to get creative hiding wires etc.

As far as reversing the phase on one of the pairs, does it really matter which ones I do that to?
Something tells me it doesn't...

Actually, I love tube amps..
I play guitars through them.
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post #17 of 26 Old 02-17-2017, 05:00 AM
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I believe the woofers facing into the room should be in phase, and the ones facing out should be wired out of phase. Otherwise all the woofers would be out of phase with your main speakers.


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post #18 of 26 Old 02-17-2017, 05:52 AM - Thread Starter
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Quote:
Originally Posted by action_jackson View Post
I believe the woofers facing into the room should be in phase, and the ones facing out should be wired out of phase. Otherwise all the woofers would be out of phase with your main speakers.
Yes, of course. Doh!
You know, sometimes I get so wrapped up in a project or small details that I overlook the obvious, thanks for indulging me and thanks for the reply.
Sheez, wasn't even thinking about the rest of the system..lol...

Off to the workshop I go..

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Last edited by wreckingball; 02-17-2017 at 05:57 AM.
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post #19 of 26 Old 02-19-2017, 06:06 AM - Thread Starter
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OK I've got the enclosure nearly done, but I have a question about the wiring..
I'll be driving these with an iNuke DSP6000, which is pretty much 2 3000s bridged in one amp.

All 4 of these drivers are DVC (2 ohm per), and I want to get the most out of the setup, but have never dealt with DVC, especially of the 2 ohm variety.
The 6000 will do 4 ohm but not 2, and obviously 8. Given all this would you:
1) Jumper the voice coils, then series wiring to amp for 8 ohms?
2) Use the drivers in SVC mode, then series to amp for 4 ohms?
Diagrams of the wiring options attached:
*edit* not going to worry about wattage atm, I'll manage that with volume knob

Thanks
-Steve
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post #20 of 26 Old 02-19-2017, 08:18 AM
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I would do the 8 ohm load, you will have more than enough power to drive these beyond their limits.


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post #21 of 26 Old 03-14-2017, 07:09 PM - Thread Starter
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Thanks for all the help guys...

I finally got the manifold done, mounted the drivers and then the manifold to basement ceiling joists, and for the most part, I'm impressed...

Very low, natural, and uncolored sound ..transparent..and HUGE output...

Only thing I find undesirable is the way it radiates through the house framework..joists, etc.

Any known way to stop this? Shock absorbers of some sort?

Anyway, here's a pic of the beast, and yes, it's a beast! (2 DS4's and the HT18s)
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post #22 of 26 Old 03-15-2017, 02:26 AM
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No guarantees but try this.......

A heavy limp membrane spaced roughly 4'-6' away from the manifold will help attenuate the rearwave.

Try making an 'enclosure' from multiple layers of very thick heavy carpet (wool if possible) suspended from the floor joists . Space multiple layers each 3" or so apart, sort of like layers of an onion.

The material should be loose to move with the pressure created by the rearwave, I don't think you want it mounted in a rigid frame, but that might be something to try since this whole idea is an experiment.
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post #23 of 26 Old 03-15-2017, 04:26 AM - Thread Starter
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Hey, Thomas, thanks for the suggestions, will give those a shot.

Quick question: As long as the mounting 'gasket' material manages to sufficiently seal off and separate front and rear waves, does it matter how 'absorptive' it is?
Reason I ask is that right now, what I used is rather slim/undersized, and it compressed to almost nothing when I cranked the screws mounting the manifold up there.

I don't think I ever looked closely at this particular detail while over at your site.

I imagine if it's too much absorption, it will reduce output, but I'm not thinking along those lines, just a bit of vibration reduction would be sufficient..I've tons of headroom, dB-wise, to work with...

Thanks again for your comment and suggestion.

*Edit* Forgot to mention that this minor annoyance is not even audible in the basement/listening room, only on the main floor where you can't hear the main, L/R speakers.

Cheers
-Steve

Actually, I love tube amps..
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Last edited by wreckingball; 03-15-2017 at 04:48 AM.
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post #24 of 26 Old 03-15-2017, 06:45 AM
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The only requirement for gasketing the woofers is to create an air seal, any absorption of vibration would be insignificant.
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post #25 of 26 Old 03-15-2017, 07:05 AM
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I live seeing other people's IB installs. I sure love mine
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post #26 of 26 Old 03-15-2017, 06:34 PM - Thread Starter
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Quote:
Originally Posted by Thomas-W View Post
The only requirement for gasketing the woofers is to create an air seal, any absorption of vibration would be insignificant.
Yes! That's great to know, I'm putting this new gasket together out of closed cell foam as we speak.. BTW, It's not for the woofer itself, but the manifold-to-ceiling coupling..

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I love seeing other people's IB installs. I sure love mine
Yea, Mr. EW ...love the sound of mine already.. it's the quality, not the quantity of bass that matters to me, and IB is proving to be beyond excellent..
Like I told Thomas though, I've boatloads of quantity as well..no worries there..
Just need to do this modification over the weekend, I'll post pics of it when I'm done...

Actually, I love tube amps..
I play guitars through them.

Last edited by wreckingball; 03-15-2017 at 06:41 PM.
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