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post #1 of 40 Old 12-20-2012, 02:03 PM - Thread Starter
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With the recent discussion about the importance of room treatment and how loud we listen, I thought I'd seek our peer help on this. I don't listen very loud, but I do demand high fidelity. And having a quite room is part of that.

This is a new room to me, I'm still setting up. So this thread may evolve. I haven't even taken any measurements yet. Those will come, maybe even over the Christmas break.

For starters, here is a layout with what I'm working with.



It's fairly to scale, but not exact. Floor is laminet over concrete slab. I've thrown down some rugs, but it was laminet when we bought the place or I'd have gone with carpet.

Speakers are SEOS design and have controlled directivity. They're flush with the wall. As you can see, sidewall reflection should not be an issue at all. So I'm thinking my main areas of concern are: Floor. Ceiling. Rear wall. The large window behind me can't help either.

What are peoples opinions and what would you do to make this room better.

Thanks in advance.
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post #2 of 40 Old 12-20-2012, 02:58 PM
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I know,the last thing you want to hear, however any chance to rotate the entire set-up? Merely inquiring ....

The sidewall distances are great, but the 11.5 foot dimension is prohibitive.

Ideally you need some space behind the LP and maybe the mains could benefit from spacing off the wall.

That's ideally thinking, .. clearly many of our rooms are anything but....

edit, .... man, I need to work on my comprehension skills ... the flush detail I missed, my mistake

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post #3 of 40 Old 12-20-2012, 03:21 PM
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My apologies for the rotation query ....


Any pics? What's the ceiling height and is it finished?

What type of wall materials, drywall/wood stud?

Is there a table or anything between you and the mains? Anything in the proximity of mains?(ie, how is your display back/side, wrt encountering energy off the mains)

With that layout....
I'd space the seating off the wall somewhat and make a big, deep broadband black hole behind the LP. (3lb or equivalent,... min, 4" spaced 4", or thicker,...as much as you can sacrifice up to a foot)

With the rear wall addressed, I'd examine the ceiling/floor, between the mains and LP. Depending on how your ceiling is made, would dictate what I'd do. Small spaces such as typical residential rooms, need a great deal of bass trapping. As much as you care to install. No need to worry about over deadening, as steps are easily taken to mitigate a loss of MF/HF energy.

When you say flush mounted, that's great, but how is the front wall surface currently? Any additional steps for diffraction control/deadening etc.? Are your mains toed in? Angled down?

Thanks

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post #4 of 40 Old 12-20-2012, 03:25 PM
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Originally Posted by FOH View Post

The sidewall distances are great, but the 11.5 foot dimension is prohibitive.
With the seating against the rear wall I don't see a problem, he won't be dealing with quarter wavelength distances from the seats to the wall. I'd start with heavy drapes on the rear window and glass door, and play with the sub placement. The two flanking the screen are too symmetric, the third would be better toward the rear of the room. perhaps the corner next to the fireplace.

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post #5 of 40 Old 12-20-2012, 04:08 PM - Thread Starter
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My apologies for the rotation query ....

No need to apologies. That's what I originally wanted to do, but it can't be done. I'm stuck oriented like this.
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Any pics? What's the ceiling height and is it finished?
What type of wall materials, drywall/wood stud?
Is there a table or anything between you and the mains? Anything in the proximity of mains?(ie, how is your display back/side, wrt encountering energy off the mains)

I'll get some pictures. Good idea.

The ceiling height is 8', and it's ceiling tile, dense fiber board stuff I've never seen before. Open joists above the tiles. Then plywood under hardwood flooring. The walls are conventional wood framed drywall. No table or anything between the LP and the screen/mains.
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With that layout....
I'd space the seating off the wall somewhat and make a big, deep broadband black hole behind the LP. (3lb or equivalent,... min, 4" spaced 4", or thicker,...as much as you can sacrifice up to a foot)
With the rear wall addressed, I'd examine the ceiling/floor, between the mains and LP. Depending on how your ceiling is made, would dictate what I'd do. Small spaces such as typical residential rooms, need a great deal of bass trapping. As much as you care to install. No need to worry about over deadening, as steps are easily taken to mitigate a loss of MF/HF energy.

Hmm, well, I'm not sure what I can do about the rear wall. I'll get drapes over the glass like Bill suggests. That was planned. I could maybe spare 6" without WAF becoming an issue. How important do you feel this wall is.

I could insulate the ceiling to trap bass. Wouldn't come cheap and wouldn't achieve much. I dunno, maybe it would. It's would be very easy to do though. There's a 10" cavity between all the joists.
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When you say flush mounted, that's great, but how is the front wall surface currently? Any additional steps for diffraction control/deadening etc.? Are your mains toed in? Angled down?
Thanks

They are like this



There will be some diffraction off the edge of the "baffle" and the AT screen goes over it. So the frame of the screen will diffract as well. But that's over a foot away from the drivers. No angle or toe in though. I can do things to improve the diffraction, but can't angle these. They're stuck this way.

Thanks so much for taking the time. Really appreciate it. Room treatment isn't something I'm experienced with.
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post #6 of 40 Old 12-20-2012, 04:08 PM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post

and play with the sub placement. The two flanking the screen are too symmetric, the third would be better toward the rear of the room. perhaps the corner next to the fireplace.

Great suggestions Bill, thank you.
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post #7 of 40 Old 12-20-2012, 04:13 PM
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Good idea about sub experimentation. I too noticed things I'd try with the subs, but was thinking this was primarily acoustic treatment.

Respectively, I couldn't disagree more about drapes. In my opinion, the only application for drapes would be in front of thick absorption. When utilizing absorption (with the typical porous approaches like fiberglass etc.), you either absorb i all or none at all. Using thin inadequate absorbers like drapes, you just filter the reflected energy. That removes the MF/HF, leaving a bass heavy, lifeless result.

I like drapes for "fronting" other thick absorbers, for both aesthetic reasons, and more importantly, it can be more effective grazing angles than some treatment panels faced with other material.

If you're going to sit in close proximity to a rear boundary wall, you're too close for diffusion (which is preferable to the rear) so you absorb it all, ..as much as possible. As stated, minimum of 4" spaced 4" off, or even thicker.

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post #8 of 40 Old 12-20-2012, 04:19 PM - Thread Starter
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As stated, minimum of 4" spaced 4" off, or even thicker.

Like a 4" wad of insulation spaced 4" away from the wall. Can I put it closer to the wall, or will that just ruin the effect?
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post #9 of 40 Old 12-20-2012, 04:37 PM
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It's about the distance off the boundary, that's critical.

4" of 703 fiberglass, is nearly as effective as an 8" thick absorber of the same material.

You're trying to catch as much of the maximum velocity element of the waveform. The max effectiveness of absorption occurs when the air gap is 1/4 the wavelength for that frequency. The waveform velocity is greatest as it transitions through the zero point. Conversely, at both the top or bottom of the cycle, the velocity is minimum (the pressure is maximum), and when the velocity is greatest,..there's more heat disapated through the absorbent material. So, placing the fiberglass or whatever right up by the wall does very little but suck out the highs.

This is a great tutorial on some basics. It really is.

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post #10 of 40 Old 12-20-2012, 07:49 PM
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There will be some diffraction off the edge of the "baffle" .
Nothing to speak of, and the flush mounting eliminates baffle step and Allison Effect, so the midbass should be much smoother than otherwise.
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Respectively, I couldn't disagree more about drapes. In my opinion, the only application for drapes would be in front of thick absorption.
Glass doesn't need thick absorption, it flexes enough to be less reflective of low frequencies than a wall. OTOH it's much more reflective of mids and highs, but all it takes to control them is closed drapes.
As for using 4 inches of glass, I'd make sure things are broken before I went about fixing them.
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You're trying to catch as much of the maximum velocity element of the waveform. The max effectiveness of absorption occurs when the air gap is 1/4 the wavelength for that frequency.
Technically true, but as 1/4 wavelength ranges from 1.8 feet at 160Hz to 3.6 feet at 80Hz it's seldom, if ever, practical to employ an air gap.
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So, placing the fiberglass or whatever right up by the wall does very little but suck out the highs.
It's less effective than with 1/4 wavelength spacing but that doesn't mean it's ineffective by any means.
I don't have any visible treatment in my living room, and it's nearly as good acoustically as my recording studio in the basement. I have wall to wall carpet over 1/2" felt padding, two large upholstered couches, acoustical tiled ceiling, drapes, a large bookcase full of books and thick textured wallpaper. I'd add more if it needed it, but it doesn't.

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post #11 of 40 Old 12-21-2012, 08:55 AM - Thread Starter
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Ok, I'm going to get drapes. Experiment with sub placement (hopefully get some baseline measurements over the Christmas break). And try and pick up some OC703 to start experimenting with. I don't think I can give up 12" behind my couch, but 4 or 5" might be acceptable to get good >250hz absorption.

Do you think it would be worth it to insulate my ceiling? I'll check to make sure it's broken before I do that, but I'm wondering if I should be gearing up for that a bit.

Anyone think my steel fireplace is an issue? I'll take some photos of the room, that might help answer that question.
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post #12 of 40 Old 12-21-2012, 09:24 AM
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Ok, I'm going to get drapes. Experiment with sub placement (hopefully get some baseline measurements over the Christmas break). And try and pick up some OC703 to start experimenting with. I don't think I can give up 12" behind my couch, but 4 or 5" might be acceptable to get good >250hz absorption.
Just make sure it's broke before you fix it. That's where measurements are key.
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Do you think it would be worth it to insulate my ceiling?
Being fiberboard (probably Homasote) it may not be too bad as it is, better than sheetrock for sure.
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Anyone think my steel fireplace is an issue?
Probably. If it rings a ceramic wood stove is a non-resonant option.

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post #13 of 40 Old 12-21-2012, 03:11 PM
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First, the drapes combo with a window is fine, I mistakenly thought the drapes were intended for for wall covering. No reason to think that either, my mistake Bill*.


Above a drop ceiling, is ideally suited as a highly effective bass trap when filled with fluffy batts, or equivalent insulation. For starters, I've seen just the effect of a one inch tile covering a 16" open space, ... and it's a very nice and effective bass trap that absorbs pretty deep due to the physical distance of the fiber board away from the boundary. Throwing some inexpensive insulation up there makes it nearly ideal.
It's ideal for two reasons, it works so well so cheaply, and it occupies no space in the room. I've seen several before and after measurements that clearly illustrate the benefits in both time (ringing) and freq (smoothing) domain.


Oftentimes, the grazing angles off the ceiling preclude it from addressing reflected energy in the MF/HF, so perhaps a small ceiling hung cloud would both maximize the room's bass damping, and absorb the critical reflected bands within the first dozen or so millisecs. You've go the makings of a nice ITDG, which means a nice separation between the direct and reflected energy. Initial Time Delay Gap, is the gap right after the direct sound, and until the first reflected energy encounters the LP. With the sidewalls spaced nicely apart, it leaves the area directly behind your head, ceiling between you and the mains, and of course the floor reflections.


In your case, with the sidewalls so distant, the debate on absorbin or diffusion for lateral sidewall energy isn't as significant as in typical orientations that are longer than they are wide. That said, the remaining early reflected (from above, below, and behind) energy can be soaked up with absorption with no ill effects on spaciousness. Sidewall reflections are fine as long as they are reduced in level, or delayed in time. Our ears lateral spacing dictates there's little good that comes from the ceiling and floor early reflections. So fully attenuating them is no problem and often clears up other details via lowering the smeared in time early reflections.


Bill's right, big windows, sliding glass doors are lossy diaphrammatically in the LF. I've got one to my right, it's quite effective really at bass transmitting out. That wasn't my initial concern, and drapes are fine there. It's the area directly behind your listening position, and it's critical. Total absorption at that spot (if it's 4" that's fine), then as much bass trapping as aesthetically possible, then measurements, ray tracing, ETC determinations, those results would dictate further moves.


Subwoofer optimization aside, a properly damped bass trapped room will likely be a revelation. Rooms can easily possess 20-30dB swings in response, modal issues, ringing extending way too long,...cleaning that up will help clarity, and tonality. The great thing about bass trapping, the cheap, loose fluffy variety is found to be more effective with thick traps than the rigid stuff previously believed to be best. If you consider fiberglass, rock wool, polyester, or cotton, your options are plenty.


As far as effectiveness; If you're using 4" of space, you use a rigid product, so you're cool there. But if you've the space for very thick traps like elsewhere in the room, utilizing fluffy insulation config'd in a manner so as to not compress much, they're most effective and least expensive. You can certainly use rigid 703 style, or the eco denim cotton stuff too, ... in a stacked superchunk method, which countless examples are out there. It too is effective.


Be mindful that porous insulation, like the items I've mentioned, is a velocity-based absorber. So it needs to benefits greatly from being spaced away from a boundary. This puts it into position for it to be most effective. The problem is,as you go thicker and thicker (for lower and lower freq damping) you need to transition to a material with a lower flow resistance, like the pink fluffy etc. Next, the issue becomes assuring the insulation doesn't become too compressed via implementing various techniques, supports etc. Methods include stacking chunks in the corner with bird netting supports lessening compression of lower layers. Another is hanging vertical sections fluffy from above, allowing them to hang freely and never compress.


Despite it's measured superiority, in many cases individuals prefer using the more rigid super chunk approach which is as I stated above, still an effective approach.


Loose rule of thumb to maximize effectiveness;
If you have 4" to use, 4" of 703, having 8" of space, use 2" 703, 6" fluffy (or 8" of Roxul SafeN-Sound), 9"-12" or more, utilize fluffy insulation.



Another item, what I've found (that's consistent with much other work/whitepapers etc), the front wall can be entirely absorptive with little to no negative side effects. This is lower on the order of importance, but I certainly like it.


Recap; the first two are a win-win, no downside scenarios
1.) I'd put a 4" (or as thick as possible) directly behind the LP
2.) Install loose fluffy above the drop ceiling
3.) Measurements, become adept at them and everything should be based on them
4.) Find and treat detrimental first/early reflections
5.) Find and treat modal and boundary related problems


My 2 cents, my opinions/experiments and findings. Much coincides with that of the smart guys/acousticians. *I hope my mistakes haven't found their way into this post too! I'm undergoing some serious, life changing health issues, and unfortunately I've taken a hit intellectually,..a pharmacological cesspool if you will.

Best of luck


Some interesting reads;
Here
Here

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post #14 of 40 Old 12-21-2012, 07:18 PM
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Another item, what I've found (that's consistent with much other work/whitepapers etc), the front wall can be entirely absorptive with little to no negative side effects.
With as shallow a room as this I'd lean towards concentrating more on the front wall than the rear wall, should it prove necessary.

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post #15 of 40 Old 12-22-2012, 06:57 AM
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The rear wall treatment I'm suggesting, would be quite small. No more than a single 2'x4' panel.

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post #16 of 40 Old 12-22-2012, 02:52 PM - Thread Starter
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Thanks guys. I'll get baseline measurements soon and start from there.
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post #17 of 40 Old 12-22-2012, 03:23 PM
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I did some measurements today to compare the low frequency reflectivity of glass versus walls, with surprising results. I grabbed my handheld RTA and switched my HT source to pink noise, then measured SPL a few inches from the walls and also the windows, one of which measures 5x5 feet. From 20 to 80Hz there was no discernible difference.
I took a 40Hz reading at the 2 inch solid oak front door, then opened it, revealing the glass storm door. The level didn't change. Then I opened the glass storm door, and the level dropped by 6dB. I went onto the porch and took a reading with the storm door open, then closed it. The level went down by 6dB. I then closed the inner solid oak door, the level went down another 6dB. So inside the room the reflectivity difference between walls and glass was negligible, that between glass and air significant. To tell the truth I'd expected the reflectivity of the glass would be at least a couple of dB less than the wall, but it wasn't. Glass does allow a lot more transmission of low frequencies than walls and doors, but that transmission doesn't mean that no energy is reflected back into the room. On the contrary, in this test glass and walls were the same.
This indicates that windows not only don't act as bass traps, they probably need damping just as much as walls do. But since windows tend to be a small percentage of the total wall area, and seldom are in the room corners, I wouldn't be all that concerned about them. The main issue they'll present is environmental leakage.

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post #18 of 40 Old 12-23-2012, 09:15 AM - Thread Starter
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Surprising but great info Bill. I did some measuring yesterday but not the room. I meant to but ran out of time. My setup isn't conducive to measurement anymore. I'll find time and hopefully see if I can replicate your findings.
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post #19 of 40 Old 01-16-2013, 07:01 PM - Thread Starter
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I moved my left sub out to the end of that wall and got this



I think my 2 subs on the right are a bit co-located.

They summed like this



Need to hook up my minidsp and get rid of that peak at 50hz.
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post #20 of 40 Old 01-16-2013, 07:24 PM
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That looks quite decent. Are the subs running a little hot?
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post #21 of 40 Old 01-16-2013, 07:57 PM - Thread Starter
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No actually. That was crossed at 200hz for measurement purposes. Being down firing may have tapered the top end down. I did cross them at 90hz and they blended well. I did have to lower their level to get a blend though. I think once I take out that mound around 50hz with eq it'll be all good.

These things died below 13hz though. I'm using an old old amp though. I should try a different amp.
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post #22 of 40 Old 01-16-2013, 08:42 PM
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Nice space. I like the flush mount and AT screen idea. Drapes and a few diy panels is definitely the quickest way to get very good results. DIY bass traps are a little extra work but well worth it for corners also.

Ignore if I'm repeating something already well known but the easiest method of sub placement I found is old school. Just use one sub placed at the LP even if you have to move the couch some to place it there. Crank it up playing something with heavy bass and go walk around to check where the bass is loudest. Make notes of which locations and those are the most gain placements. This sounds like something basic 101 simple to do but helps where you have large subs you don't want to keep moving around for "testing". Since you have three it should be easy to get full room smooth response. Not each one has to be placed at the most gain positions but least you'll know where those are.

If your fireplace or other side areas become a problem, you could have drapes that go all the way across closing off that area when you need them for watching. Like an entire run mounted on the ceiling that stays pulled and tucked to one side when not in use. If you go that route and could use something heavier there is always accordion doors. We have a very small one that tucks into the side wall and when pulled closes off our hallway part of the house that also hides the rack room. They are made of heavy hard wood or veneered mdf which provides an excellent noise killing option. Yes they still sell those ugly ones some of us remember in school for a divider wall. There are much nicer ones these days biggrin.gif

Our LP is against the wall also. An idea we used for a back panel is a large picture that is printed on cloth or porous canvas with the back stuffed as a diy sound panel. Works great and people don't even know it's dubbed as an acoustic panel.

"I should really see what dB levels I'm pushing. Long as it can't foam my beer during a movie we are ok "
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post #23 of 40 Old 01-17-2013, 08:49 AM - Thread Starter
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Originally Posted by autox320 View Post


Our LP is against the wall also. An idea we used for a back panel is a large picture that is printed on cloth or porous canvas with the back stuffed as a diy sound panel. Works great and people don't even know it's dubbed as an acoustic panel.

I really like this idea. My wife is crafty/artsy. I think she'll have an idea that could work. A fun pattern or something. Even my subs she's going to paint the tops with art. I don't care what they look like so I told her go for it. It helps her be ok with 3 massive subs.
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post #24 of 40 Old 01-21-2013, 07:42 AM
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Articles on this suggest fron wall is nearly useless. Only maybe diffusers are needed up front is what I'm reading
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post #25 of 40 Old 01-21-2013, 07:49 AM
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Originally Posted by goonstopher View Post

Articles on this suggest fron wall is nearly useless.
I can't imagine why. Reflections off the rear wall don't magically vaporize before hitting the front wall, to be reflected again, while the omni-directional output of subs will be equally reflected off the front and rear walls, and every other large surface for that matter. Depending on the LP the front wall may have quite a bit less effect than the rear wall, but that doesn't make treating the front wall useless, especially where Allison Effect is concerned.

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post #26 of 40 Old 01-21-2013, 02:14 PM
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Thought I saved the article. It was written by a wall treatment vendor I think. Over at hometheater shack
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post #27 of 40 Old 01-21-2013, 02:24 PM - Thread Starter
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In my situation I'm ignoring the front wall cause:

a) I want the front wall to be just a screen for visual reasons. I have some subs sitting against the wall, but even that is frustrating. And will soon be moved around.
b) with the speakers flush in the wall, I'm not worried about allison effect and any reflections coming from the rear wall need to be treated at the rear wall before I get carried away. Right now there isn't anything. Although I don't find them that bad (at all).

Is it possible because of how our ear is shaped, the rear sound is mostly not bothersome? The rear wall hasn't bothered me yet.
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post #28 of 40 Old 01-21-2013, 03:41 PM
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Quote:
Originally Posted by tuxedocivic View Post

In my situation I'm ignoring the front wall cause:

a) I want the front wall to be just a screen for visual reasons. I have some subs sitting against the wall, but even that is frustrating. And will soon be moved around.
b) with the speakers flush in the wall, I'm not worried about allison effect and any reflections coming from the rear wall need to be treated at the rear wall before I get carried away. Right now there isn't anything. Although I don't find them that bad (at all).

Is it possible because of how our ear is shaped, the rear sound is mostly not bothersome? The rear wall hasn't bothered me yet.

I believe it's the integration/fusion time. The energy off the rear boundary is all within the period whereby it causes measurable issues (comb filtering), psycho-acoustically, the ear/mind can't delineate these closely spaced events in time. Yet, the acoustic distortion remains.

The area directly behind a near boundary LP, is important to absorb as effectively as possible. Only needs to be big enough to affect the LP,...bigger, no problem though.

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post #29 of 40 Old 03-30-2013, 03:52 PM - Thread Starter
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Oh so this is why you don't trust unibox and winisd

Blue is nearfield
Red is ground plan fast sweep
Green is ground plane slow sweep



Box model says q = 0.65. mad.gif

I'm gonna take an impedance sweep and see if there's anything wonky.
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post #30 of 40 Old 03-30-2013, 05:04 PM
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Originally Posted by tuxedocivic View Post

Oh so this is why you don't trust unibox and winisd

Blue is nearfield
Red is ground plan fast sweep
Green is ground plane slow sweep
Outdoors?

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