7 x RE Audio XXX 18" subs, Infinite Baffle Sub, Ultimate IB build - Page 3

no consideration of a dual manifold-type install where the subs are opposite each other? Would help with box vibrations

Just be aware that the xxx has an absurd amount of moving mass and tons of excursion, would be hard to keep that wall from flexing. Im sure you are considering those things though.

Dave,

A couple things.

1. What are your plans for implementing the IB itself? I don't know anyone with a "concrete bunker" (i.e. - 6 concrete walls) that has implemented an IB. Unless your concrete bunker is sectioned off into multiple chambers?

2. Being in a "concrete bunker," others can attest that there is a difference in tacticle feel one can accomplish on a solid concrete floor vs. suspended wooden floor (or other than concrete). Might have a few differing opinions in the group, but just keep that in mind as being a possibility.

3. Remember that most people are very limited when it comes to room placement of their IB. And in most cases it's simply a roll of the dice as what the end result will produce.

+1. four of these all firing one way will produce a lot of force.








As far as what you can expect in a 3,000 cube room...Probably something similar to this. Note that I am amp limited. There's another 3 dB peak output that could be extracted from the drivers before they run into excursion trouble. I'm not in any hurry to upgrade for that.





You won't be using those types of output levels except for a random let's see what she'll do type demo to scare the occasional friend or yourself. You will be repairing some things around the place when you do. .
Edited by Ricci - 10/12/12 at 1:28pm

^^^^^^^^^
I want to know a LOT more about this.

Ricci is that only 4 or all 8 of yours?

I would re-think the way you are going to mount those subs. I had 4 IXL 18's built into my wall just like that pic. It was a disaster. I used 3" of ply, triple braced with 4x8's and beefed up as much as humanly possible and it still flexed the entire wall. It shook the entire house and rattled everything. You could actually see the entire wall flex. I used it like that for about a month and tore it all down and did a opposed box....... only about a million times better! the difference was beyond belief. The only way I do an array like that is if it was concreted.

Beast,
That's all 8 on 2 K10's on a 240v 50a line. I quit the burst testing after 31.5Hz because I'd already broken a few things like a big picture that is one of the missus favorites in the upstairs living room and my back door to the patio. I have a big peak near 45Hz which means that 40-50Hz would have been well over 140dB and my mic systems starts clipping the soundcard input at about 137-138dB anyway. It kind of irritates me that my electronics fall off of a cliff after 6Hz but hey I guess 5 to 6Hz extension with 120dB+ at the seats capability will have to suffice.

Anyway Dave you should be looking at headroom similar to this. REF level playback and most anything else really, will be a walk in the park. Please give serious thought to Nate's post as well. I've never done an IB but he has direct experience with it and I know how bad these drivers can shake something. I would strongly suggest mounting them dual opposed to help cancel out vibration.

I'm pretty sure there was some discussion on this fairly recently over at the cult. Dave, you might be interested in looking for it if you haven't already. It was within the last few months in the project section if I recall.

Dave. Is building an external manifold a viable option?

I can't remember where I saw it but one guy had an IB system that looked just like a cube shaped sealed sub but the bottom of it was attached to a large airspace and it was indeed a real IB system. It just looked like a regular subwoofer.

Its called an outie! I contemplated that before going under my house with mine. There are benefits to that design.

Ah... if JapanDave can fit an external box like that where he wanted to vent out for IB anyway, then that would definitely cure the problem he would get with 4x XXX18's. Yikes I totally would not even try that!

"Like this"

Eh? You mean where the Teraform XL's would be? If so... you totally have room..... I think. Looks like it to me.

I think this is the idea you guys are referring to:

http://www.jonathanfoulkes.com/Home_Theater/Speakers/IBSub.htm

Chris

A couple of steel I-beams would really take care of business for this install... Rigidity is key, for IB or for a box.

Here is a link to a thread based on that IB setup on "Whats Best Forum"

http://www.whatsbestforum.com/showthread.php?5402-Infinite-Baffle-and-the-Audiophile

I thought those pictures looked familiar.



Forin

Now that I see you pic and you plan, you should be good to go. I though it was going to be built into a wall.

Dave forget about the whole VAS thing. Seriously. If the IB guys want to say that it's not a true IB because it doesn't meet some prescribed vas multiplied by how much amount of air volume who cares. It's not like you will hear some huge audible difference between 15 cubes per driver and 150 cubes per driver.

How much space you got anyway?

+1. IB means Infinite Baffle, which is defined as a speaker where the front and rear waves do not meet. Said definition applies equally to a 1/2 cu ft sealed box and a 10,000 cu ft attic. Vas only enters the equation in determining the minimum rear chamber size required for a desired F3, the same as with any alignment.

+2

While I acknowledge there is a difference between the technical definition of IB and the commonly used meaning, I don't find it necessary to meet a certain volume requirement before the attempt becomes worthwhile. If you have the space, bigger is better. If you have the money, shoving more drivers into that space even if falling well short of some IB guideline may be beneficial. In any case, my personal definition of IB is a sealed box big enough to substantially reduce power requirements and minimize effects of box on final q. A couple or so times VAS is a big danced box, and the difference between small sealed and that point is much greater than between 3x VAS and 300x VAS.

+3

Ignore the 10x Vas requirement.

Wow, great discussion, great thread. I haven't had a chance to keep up with this thread.

I've followed Japan Dave's room/system build, and the complex and perplexing hearing issues he's encountered upon first firing up his previous rig. So it's great seeing things moving along again. I really dig the room specifics and details on choices made thus far in his build.

Regarding VAS guidelines, there are none.

I'm not sure if Josh, Bill, Bigus or Scott have built an IB for HT use, but they do offer good advice. Typically, there's other factors to consider when discussing the theoretical standards for IB construction. Yes, the VAS question seems to come up first, and the answer would be typically about 4-10 is the goal when pursuing those theoretical benefits. More importantly would be the overall implementation of the build, and subsequent optimization with the mains and room.

This case, it is what it is, the backspace is predetermined (and maximized via fluffy stuff too IIRC). The theoretical ideal VAS element to IBs is really a design from ground up question. In builds with less than theoretical ideal, I'd only be concerned with IB only drivers, like Dave's fist choice the Fi IB3-18, and it's modest motor. So driver choice is a factor to how significant the backspace characteristics are.

It's also been empirically determined the space immediately around the drivers is impactful, and ideally can benefit from being free from acoustic obstruction. Again that doesn't apply here (can't be altered significantly), just like the VAS parameter.

The use of the RE XXX 18" drivers is fantastic. Robust bottoming tolerance is hugely important for IB use, sounds like it's the ideal driver for such. I wish I didn't have to be concerned with amp power with my quad 18 IB. I've been considering a retrofit,...another conversation.


Also, you're approaching the IB implementation to a HT spot on correct IMO. Like other approaches, an IB has some wonderful benefits otherwise unattainable in other subwoofer alignments/approaches. The planar wave launch close coupled acoustically to the mains, combined with the response smoothing effects of the additional small sealed balancing subs. I too am utilizing te IB/small sealed balancing sub approach. Dave, good lookin' out, great approach for sure.

The Datasat processor is a piece of work. I attended the private party roll-out last year while attending Cedia. The demo had issues, but none related to the processor. That thing is absolutely amazing. When optimizing, I think you'll benefit most from varying phase and low-pass settings on the small sealed 5400s. I'm guessing the automated optimizing has this covered, but some tweaks manually after the fact may help as well. That, is down the road.


Best of luck Dave

Another thing Dave,..others, are you saying the back of the mighty Quested's are fully exposed to the acoustic back-pressure of the IB?

If so, I'd contact your rep/dealer, or ever Quested themselves,... and inquire with them. Surely, with all the similar installs in baffle walls in studios, various concerns and questions has come up. I don't know if it'd be problematic or not. I know they're robust boxes, I've seen them. I'd not want any of the critical midband, HF energy being modulated by the subs back-wave, if that's possible.

Good luck

Does anyone have a link, or the actual driver before them to give me some dimensions?


I've been entertaining the idea of retrofitting my 4x18 dual opposed attic IB manifold, for more system experimentation ever since I completed it. I'm interested in the precise OD of the surround, the precise OD of the entire driver frame.

Also, what would be the general consensus on ideal maximum recommended amplification per driver, in an IB alignment, w/no high-pass? As I re-read the powering discussion, dual 2ohm XXX, and about 2kw per 4ohm (2+2) driver, .....is this it, series the coils and feed them ~2kw?

IIRC, there's been a couple IBs with these, and a small amount of small-sealed. Wrt the IBs, what have been the actual choices made, 2kw into the 4ohm load? Without the paranoia of the hard bottoming, the powering can have a lot more latitude, and I've always wanted to employ some big, robust drivers in the IB. Like Dave, I considered LMS 5400s, but I liked the re-coning capability of the Fi drivers. I strongly considered Kevin Haskin's Maelstrom 21"s, again there was some factors pulling me toward the Fi offerings.


My application was ideal for the Fi IB3-18s, with a huge attic backspace, but the inherent roll-off could be better. Believe me, the quality and bang for the buck for the Fi 18s is superb. For ~$1300, material, four of those and an EP4K,... yields 127.5dB@1m@20hz@225w/driver). I'm getting a clean 117dB@20hz at the LP. But still I was constantly re-visting the IB powering conundrum I mentioned on page one in this thread. Despite what a small minority claim, the bottom octaves add realism, .... regardless whether one hears them, feels them or a blend of the two,....high passing isn't an approach I'm interested in. As Josh mentioned, the inherent electronics roll off is bad enough. There's a bottom octave component that oftentimes accompanies percussive explosive type effects. Encountering this effect is fabulous, ...sure it's exaggerated a bit perhaps but that component of the big deep effects is something I don't want to do without. So no hi-pass for me if I can help it.

Dave, which amplification route are you taking/considering?

Also, have you examined the LF decay characteristics of the space yet? The construction method of the bunker is killer for PVG, but sharpens the Q of any modal interactions, and doesn't dissipate the LF in the time domain as well as a stick built residential room. I know you've got bass traps, etc, and I believe Dennis helped on the design to, right? Anyway, it would be of interest to see.

You're certainly going to possess some LF fire-power.

All the best
Kevin

FOH

18"
Mounting Depth - 14.75 inch
Mounting Hole Diameter - 17.375 inch
Overall Diameter - 19 inch
Bolt Hole Circle - 18.25 inch
Motor Width - 10.5 inch
Motor Depth - 5 inch
Basket Depth - 9.75 inch
Displacement - 0.30 cu. ft.


1000-2000w per driver is fine. 1500 is probably "right". If you are worried about clanking watch the xxx excursion vid I posted in the free air driver excursion thread in the forum at Databass. Id link but Im on my phone. That is a 1400w amp channel clipping on it by the end and remember that is an 18" driver.
Edited by Ricci - 10/14/12 at 1:23pm