Double Bass Array (DBA) - The modern bass concept! - Page 11 - AVS Forum
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post #301 of 321 Old 03-24-2014, 09:28 AM
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Quote:
Originally Posted by markus767 View Post

^
"Single Bass Array" doesn't say anything about aborption wink.gif

Haha! Fair point. Maybe we should start referring to it as SBAWSAORW

Single Bass Array With Substantial Absorption On Rear Wall

biggrin.gif

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post #302 of 321 Old 03-24-2014, 12:01 PM
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Before reading your second line I was thinking Single Bass Array With Substantial Array Of Rock Wool.
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post #303 of 321 Old 03-24-2014, 12:05 PM
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Although most all of our rooms could benefit from additional low frequency absorption/damping, I'd suggest typical wood-stud w/drywall construction offers some positive acoustic attributes wrt such absorption.

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post #304 of 321 Old 03-24-2014, 01:33 PM
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^
It does! When comparing measurements from typical constructions in Europe and the US there's a night and day difference.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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post #305 of 321 Old 03-25-2014, 03:40 AM
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Guys,

I really like the new Room Simulation. I did use it to initially find the best location for the sub. Wanted to ask about surface absorption factors. How does one cater for a window + concrete wall? What I'm asking for is where best to find a list of materials for floor, wall, ceilings then how to work out the various mixed use arrangement in a structure.

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post #306 of 321 Old 03-25-2014, 08:12 PM
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Quote:
Originally Posted by FOH View Post

Although most all of our rooms could benefit from additional low frequency absorption/damping, I'd suggest typical wood-stud w/drywall construction offers some positive acoustic attributes wrt such absorption.

Indeed and thank you for the "Everest" quote a few days ago, with the absorption factors. I had forgotten I had the book.

I would dearly love to do an SBA but I don't have foot of depth at the back of the room for an absorber, due to a side window near the back wall on one side and an opening into a hallway on the other.

Do you think its at all feasible to do the absorber with multiple layers of gypsum separated by GreenGlue? That is where I was going when I asked about GG earlier. What would be the target absorption factor for an SBA? At the lowest longitudinal mode frequency, right?

Thanks,
Jack
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post #307 of 321 Old 03-26-2014, 05:16 AM
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I am itching to get started on my dedicated theater build, but, I must restrain myself so that I can have the time to make a good plan, and do plenty of more research with regards to the actual design, (ie: stage, baffle wall, screen, projector install, absorbing panel locations, ect...) I have an idea that I would like to run past you guys.

I have two full sized MartySubs each with a Dayton HO18, , and two additional HO18's waiting for a box. Would it be possible to do four front firing full sized MartySubs placed along the front wall with them standing up and two stacked on top of each other at 1/4 distance from the ceiling, floor, and each side wall? Then do some massive absorbing material such as two layers of Safe-n-Sound, on top of double drywall with clips & green glue for the rear wall? Would this constitute a SBA? If this would work, it would give me 4 full sized MartySubs each with a HO18 on the front wall, which should have some excellent output, and extension while also having reduced room modes due to the 1/4 placement.

The other option that I have, (OT), is an IB design, but, if I went that way I would have to buy all new drivers, and to be honest, I am limited on my knowledge with regards to IB subwoofer designs, so unless I would stand to gain considerable SQ by going with an IB setup over 4 MartySubs in a SBA, I will likely stick to the later, although, I am open to all options!
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post #308 of 321 Old 03-26-2014, 10:35 AM
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Don't know if your rear wall damping strategy will work perfectly, but it is likely better than nothing.

I also don't know the MartySub, but flush mounting anything in a smooth baffle wall will pay dividends on the top end if the LCRs are also flush mounted. Lower diffraction and eliminating destructive/constructive bounce off the front wall yields smoother response.

Doubt you need to change drivers to do an IB SBA. The HO18s may have a stronger motor than you need for an IB (resulting in lower Q & increased output at higher frequencies) but that is easily adjusted with EQ...maybe only room gain. Assuming there is enough headroom in the single digits, I'd cut top end response for a slower rolloff on the bottom vs EQ boost. (I use only hi-cut and my drivers are slightly lower Q than the HO18.)

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post #309 of 321 Old 03-26-2014, 11:25 AM
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Quote:
Originally Posted by JackNC View Post

Do you think its at all feasible to do the absorber with multiple layers of gypsum separated by GreenGlue? ........... What would be the target absorption factor for an SBA? At the lowest longitudinal mode frequency, right?

Thanks,
Jack

Quote:
Originally Posted by pnw View Post

Don't know if your rear wall damping strategy will work perfectly, but it is likely better than nothing.

I also don't know the MartySub, but flush mounting anything in a smooth baffle wall will pay dividends on the top end if the LCRs are also flush mounted. Lower diffraction and eliminating destructive/constructive bounce off the front wall yields smoother response.


Jack,
As pnw stated the GG multi-rock approach would help, but ideally you'd still need broadband absorption through the modal range. Somebody with more experience w/GG may be able to help with specific Fs, but a amply effective treatment in front of the wall would be needed to fully execute the technique. Be mindful, flush mounting upfront increases the rear wall's absorption needs, as all modal excitation is maximized in that axis ... with flush mains or subs.

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------------------------------------
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(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
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post #310 of 321 Old 03-27-2014, 08:20 AM
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Quote:
Originally Posted by FOH View Post


Jack,
As pnw stated the GG multi-rock approach would help, but ideally you'd still need broadband absorption through the modal range. Somebody with more experience w/GG may be able to help with specific Fs, but a amply effective treatment in front of the wall would be needed to fully execute the technique. Be mindful, flush mounting upfront increases the rear wall's absorption needs, as all modal excitation is maximized in that axis ... with flush mains or subs.

I am actually getting ready to start my dedicated theater construction, and plan to build a baffle wall with either using four ported enclosures stacked to make each driver 1/4 distance from the floor, ceiling, and side walls, or an IB of the same orientation.

I have never done a baffle wall before, and right now I am trying to get the design down, and figure out how, and out if what, I will use to construct it with, but, my question is can you give us an ideal method/amount of absorbing the rear wall in a SBA design? What about the baffle wall it self? Would 3" to 6" of Safe-n-Sound work for the baffle wall? What about 9" of the same Safe-n-Sound for the rear wall?
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post #311 of 321 Old 03-27-2014, 09:45 AM
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Quote:
Originally Posted by Martycool007 View Post

I am actually getting ready to start my dedicated theater construction, and plan to build a baffle wall with either using four ported enclosures stacked to make each driver 1/4 distance from the floor, ceiling, and side walls, or an IB of the same orientation.

Whether or not you're employing an IB, or ported, is a huge difference. I guess it'd depend on how suitable the backspace is, how low/loud the design target is.

IMO, if you can achieve your low distortion, SPL objectives and the backspace is suitable, I'd go IB. If you wish to benefit from the reflex SPL at tune, then go there.

Your room's total cubes and personal listening habits are huge too.
Quote:
Originally Posted by Martycool007 View Post

I have never done a baffle wall before, and right now I am trying to get the design down, and figure out how, and out if what, I will use to construct it with, but, my question is can you give us an ideal method/amount of absorbing the rear wall in a SBA design? What about the baffle wall it self? Would 3" to 6" of Safe-n-Sound work for the baffle wall? What about 9" of the same Safe-n-Sound for the rear wall?

In a flush mounted baffle wall scenario, the need for massive thick absorption up front is lessened, and shifted to the rear wall. Yes, one can still employ absorption on the baffle face, but it's more icing on the cake. For a more contiguous surface a thinner layer, like 2" of 703 rigid would be one way to go. However, I would go thicker and more effective than 9" of Safe-n-Sound at the rear wall, around twice that or more... depends on what material...typically, material depends on how much space you can allocate for said treatment thickness.

So, first, what's the rear wall like? What size? Any interruptions? Anything at the rear wall? How much thickness can you allocate?

As you likely know, in a SBA, the rear wall's performance characteristics are monumentally important.

------------------------------------
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------------------------------------
Active 16.8kw, 7.3 system
(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
(2)Seaton SubM-HP, (4)18" IB
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post #312 of 321 Old 03-27-2014, 01:50 PM
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I would definitely check out Nil's build http://www.avsforum.com/t/1507428/follgotts-build-18-x-peerless-xxls12 in case you haven't seen it. I am planning on doing something very similar to it and will likely include a styrofoam diffuser in front of the rock wool.
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post #313 of 321 Old 03-27-2014, 07:12 PM
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Quote:
Originally Posted by FOH View Post

Whether or not you're employing an IB, or ported, is a huge difference. I guess it'd depend on how suitable the backspace is, how low/loud the design target is.

IMO, if you can achieve your low distortion, SPL objectives and the backspace is suitable, I'd go IB. If you wish to benefit from the reflex SPL at tune, then go there.

Your room's total cubes and personal listening habits are huge too.
In a flush mounted baffle wall scenario, the need for massive thick absorption up front is lessened, and shifted to the rear wall. Yes, one can still employ absorption on the baffle face, but it's more icing on the cake. For a more contiguous surface a thinner layer, like 2" of 703 rigid would be one way to go. However, I would go thicker and more effective than 9" of Safe-n-Sound at the rear wall, around twice that or more... depends on what material...typically, material depends on how much space you can allocate for said treatment thickness.

So, first, what's the rear wall like? What size? Any interruptions? Anything at the rear wall? How much thickness can you allocate?

As you likely know, in a SBA, the rear wall's performance characteristics are monumentally important.

Thanks for the reply FOH! I am still undecided whether I want to go IB or not. I have the room, but, my drivers, Dayton HO18's may be better suited to ported enclosures from what I have read, although I must admit that I know little to nothing about IB subwoofer design as I never expected to actually have the space to do that, so I just never bothered reading anything about them.

The rear wall is 14' by 8' and has no doors or windows. I can definitely add as much absorption as is necessary.

If I decide to go IB, and build the subs into the front baffle wall with the area behind the baffle wall used for the subwoofers space, how much room is ideal for this situation in an integrated IB/Baffle wall behind the actual baffle wall itself? Assuming that I go IB, would this change the construction materials used for the baffle wall? I am assuming that for an IB to work, the space behind it needs to be air tight, right?
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post #314 of 321 Old 03-28-2014, 04:39 AM
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marty, since you aren't going to have a ton of folks in your theater room (just mostly you and your wife, right?), you might want to experiment with one sub in each corner and just see how that response looks. adjust your listening position around a little and even try adjusting the subs to point into the corners or have their back in the corners. some combination of that should give you absolutely crushing spl in your small room with little or no eq. just say'n....

Listen. It's All Good.
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post #315 of 321 Old 03-28-2014, 05:51 AM
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Originally Posted by LTD02 View Post

marty, since you aren't going to have a ton of folks in your theater room (just mostly you and your wife, right?), you might want to experiment with one sub in each corner and just see how that response looks. adjust your listening position around a little and even try adjusting the subs to point into the corners or have their back in the corners. some combination of that should give you absolutely crushing spl in your small room with little or no eq. just say'n....

LTD02- this is for a different room than what I have now, this will be a much nicer dedicated theater room, probably 14' by 17' by 8', complete with baffle wall, screen, and two rows of seating on a riser. My current room is 10' by 10', and in this room the subs are in the corners and sound amazing, but, I want this new room to look really nice, and am not so sure that I want subs in all four corners. Most likely will go with either an IB, or SBA, or possibly keep quad full size MartySubs, with two behind the screen, and two in the back, with each enclosure being 1/4 distance along the front & back walls. Right now I am leaning towards SBA, IB.
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post #316 of 321 Old 03-31-2014, 11:37 AM
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I've been running my SBA with absorbing back wall setup for some weeks now.
8 12" Dayton reference HO in sealed enclosures and 30 cm rockwool with10 cm airgap on back wall.
I'm very satisfied with the results so far. The systems digs deep, the frequency response after some EQ on the crown XTI amps are excellent and the seat to seat variance are very low. It's by far the best sub system I've ever experienced in a home setting(Thanks to follgott for starting this thread and inspiring the build), but there is one thing I'm missing from my old setup......

The old setup used 4 subs. 2 up front between the fronts and the center speaker and 2 subs in near field behind the listening position. The extra sensation of the near field subs firing into the back of the seating is something i miss for big blockbuster action movies. Even on lower listening levels this sensation gave the movies an extra dimension.

The questions now is "How should I proceed to combine the excellent frequency response from the SBA system and the feeling of near field subs?"
I've been playing around with idea of placing my old subwoofer system(4 Rythmik F12 which I never got around to sell) behind the seating in two stack at 1/4 and 3/4 room width. The idea is that if I send the full sub signal and apply a low pass filter with a cut off frequency below the lowest room node(31Hz in my room) on the near field subs and adjust the gain and delay/phase carefully and do some small EQ work on the SBA, the near field subs will not mess up the response from the SBA and I'll get some added low frequency sensation blasting into my back without increasing the overall SPL(AKA. Annoy the wife and wake up the kids). What do you guys think of this approach? Do you so any potential pit falls that I've not thought about?
The tools I got for calibration are Omnimic, XTZ RA, Radioshack SPL meeter and I use an Anthem AVM50V with ARC for the final touch.
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post #317 of 321 Old 03-31-2014, 12:49 PM
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Maybe this might work https://www.crowsontech.com/go/crowsontech/3475/en-US/DesktopDefault.aspx instead...just a thought.
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post #318 of 321 Old 04-01-2014, 10:24 AM
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Quote:
Originally Posted by mos6581 View Post

The questions now is "How should I proceed to combine the excellent frequency response from the SBA system and the feeling of near field subs?"
If you're up for a little more construction, you might take a look at what Nils (FoLLgoTT) did to get tactile response in his room. He did some pretty impressive work. He took it beyond a quest for "more" and went for even frequency response. This approach runs minimal risk of messing up the planar wave and doesn't add any more energy (SPL) to the room. And best of all, it didn't look terribly expensive. It could probably be funded with the money from selling off those spare subs you already have.

That's just a thought. The other, simpler thought is to just hook them up, recalibrate, and see if it gave you what you're looking for.

I'm not into "thumbs upping" or "liking". Don't take it personally. Just assume that I found your post helpful. Unless it wasn't.
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post #319 of 321 Old 04-02-2014, 07:01 AM
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Quote:
Originally Posted by mikela View Post

Maybe this might work https://www.crowsontech.com/go/crowsontech/3475/en-US/DesktopDefault.aspx instead...just a thought.
I've been considering some sort of tactile transducer, but all I've seen so far are designed to bolt onto the chair. Since I'm using cinema chairs I've not found someone that would fit my chairs. I've never seen the crowson system before, but I might find a way to use them in the system. Thanks a lot for the tip
Quote:
Originally Posted by pitviper33 View Post

If you're up for a little more construction, you might take a look at what Nils (FoLLgoTT) did to get tactile response in his room. He did some pretty impressive work. He took it beyond a quest for "more" and went for even frequency response. This approach runs minimal risk of messing up the planar wave and doesn't add any more energy (SPL) to the room. And best of all, it didn't look terribly expensive. It could probably be funded with the money from selling off those spare subs you already have.

That's just a thought. The other, simpler thought is to just hook them up, recalibrate, and see if it gave you what you're looking for.
Follgotts build are very impressive, and his solution to get tactile response is interesting. I'm also not on the hunt for more bass(I got more than enough for the SPL i listen to), but I miss the tactile feeling of near field subs.
At the moment I don't have much time for more construction work, but I might in the future consider this solution or the Crowson transducers which will also need some construction work since I use cinema chairs.

Hopefully I'll get some spare time during the next few weeks to drag the old rythmik subs back into the HT and do some calibration and measurements smile.gif
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post #320 of 321 Old 04-08-2014, 01:31 PM
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Hi All,

 

For an AV setup, we want the rear of the room to be largely diffuse and reflective for the rear and side effects channels to give the best effect, a feature which the single bass array would not conventionally allow.  How about having the sub array on the rear wall and the absorption at the screen end, or would this sound totally disjointed, even with large left, centre, right speakers and a low sub crossover frequency, say 35-40Hz?

 

Cheers, Carl.

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post #321 of 321 Old 04-08-2014, 01:52 PM
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Placing a styrofoam diffuser on the rear wall in front of the absorption will allow it to diffuse the frequencies of interest while still absorbing the bass frequencies.
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