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post #1 of 18 Old 02-19-2019, 12:21 AM - Thread Starter
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Basement Acoustic Treatment

I've recently been able to set up a new 2 channel system in the basement of a 100+ year old home. The basement itself was renovated and finished about 6 years ago. At this point, I'm at my wits end when it comes to acoustically treating this space. All measurements are rough but I have included pictures to help explain. I have a pair of Heil ESS AMT1a's being pushed by a McIntosh MC2105 2-channel amp. One important thing I should mention is that these speakers have a driver on the front AND the back. I plan on adding a subwoofer in the near future (separately amped) and my main sources for music are vinyl and streaming. For streaming I use a Chromcast Audio running to preamp through an optical cable. I also use this setup with a projector for TV and PS4 but I am not overly concerned with having the best sound quality for viewing, more concerned for good listening sessions. I am running all video sources through an HDMI switcher with a built-in DAC going to the preamp through RCA's.


--First off, the front and back walls are recessed roughly 16.5" at 3' from the floor, and then recessed again 7.5" one foot higher up the wall, creating two "shelves." It is hard to explain and I may not have done a good job of it, but the pictures should show what I mean.


--The front wall is 21'4.5" long, the speakers are 5'6" from the side walls and 1' away from the front wall. I have a little bit of room to move them around if necessary. I originally had them toed in a bit, but got a better sound and bigger soundstage after facing them straight forward. The projector screen is not acoustically transparent but can be rolled up. There is a 2'X3' window behind the projector screen.



--There is another recess to the left of the front wall, 18" deep and 3'11" long at 3' from the floor. Directly to the left of that is a countertop with sink that is 6' long and 2'9" deep. To the left of that, a small hallway leading to the bathroom and laundry room doors. To the left of the hallway is another protruding wall that houses part of the hvac unit. It is 3'9.5" long and 3'6.5" deep.


--The back wall is 24'3" has an 8'8" long section protruding out one foot from the wall where it was framed out to cover an old, no longer functioning fireplace. If facing the back wall, the protrusion starts two feet from the left. There is also a 2'X3" window to the left of the protrusion


--The wall to the right of the listening position is basically flat except for drywall framed out to cover a support beam. The framing and drywall is 10" long and protrudes out 1'10.5".





My main objective here is to not get extremely scientific and technical, I'm just looking to deal with the echo and make my system sound as best as possible. The bed and bookshelf will be removed and there will be a pool table placed in the space behind the couch. My plan is to add shelving for books and records in the recess to the left of the front wall, but this would just be a preference it would not be for any acoustic treatment effect. I am open to doing something else to that space if it helps with the sound. I am also open to moving around the rugs (there are two in the room) and placing absorption and diffusion panels wherever they should go. Acoustic treatment is already somewhat over my head and on top of that the room is laid out so strange.
Also, I would like to hang the mirrors that are leaning against the back wall, but I realize more glass in the room would be detrimental so those aren't necessarily a must. There is no need to worry about sound leakage from the room, but I would like whatever treatment needed to at least be somewhat aesthetically pleasing.
Any advice and input is much appreciated, HELP HELP HELP!
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post #2 of 18 Old 02-19-2019, 07:47 AM
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I have a pair of Heil ESS AMT1a's being pushed by a McIntosh MC2105 2-channel amp. I plan on adding a subwoofer in the near future (separately amped) and my main sources for music are vinyl and streaming.

My main objective here is to not get extremely scientific and technical, I'm just looking to deal with the echo and make my system sound as best as possible. The bed and bookshelf will be removed and there will be a pool table placed in the space behind the couch. My plan is to add shelving for books and records in the recess to the left of the front wall, but this would just be a preference it would not be for any acoustic treatment effect. I am open to doing something else to that space if it helps with the sound. I am also open to moving around the rugs (there are two in the room) and placing absorption and diffusion panels wherever they should go. Acoustic treatment is already somewhat over my head and on top of that the room is laid out so strange.
Any advice and input is much appreciated, HELP HELP HELP!
Very interesting pair of speakers you have... I have not heard of them.
Your room is large and that is a good thing. The first thing I would do is forget about bass performance until you can get a sub.

Second, nothing wrong with Echo's as long as they are not too close together. So the first thing you can try is getting your speakers at least 3 feet from the wall, I have mine 5 1/2 feet away from the back wall. Our brains can handle long echo's as it will process it as an echo (not distortion) and cancel it out in our brain.

Third, First reflections is what everyone needs to work on and your closest ones are going to be the floor and ceiling.

Forth, get a Umik-1 mic and download some free software called REW (if you have access to a computer or laptop that is in or close to your room. And then read up on Impulse response
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post #3 of 18 Old 02-19-2019, 08:12 AM
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I would cover as much of the front wall as possible (especially between the speakers) with broadband absorption. This will minimize reflections coming from the same direction as the speakers that would muddy the front soundstage. Do the same with the middle half of the back wall. Reflections coming from outside the front soundstage (e.g, side wall reflections) enhance spaciousness and envelopment. Absorbing these is optional.

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post #4 of 18 Old 02-19-2019, 09:07 AM
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I would cover as much of the front wall as possible (especially between the speakers) with broadband absorption. This will minimize reflections coming from the same direction as the speakers that would muddy the front soundstage.
Really... even with open back speakers? I would agree with you with regular speakers but the OP speakers are of a different design.
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post #5 of 18 Old 02-19-2019, 09:22 AM
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Really... even with open back speakers? I would agree with you with regular speakers but the OP speakers are of a different design.
IF the OP wants reflections coming from the same direction as the direct sound, then he can ignore my suggestion.

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post #6 of 18 Old 02-19-2019, 11:00 AM
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Really... even with open back speakers? I would agree with you with regular speakers but the OP speakers are of a different design.
Speakers that deliberately radiate in directions other than directly at the listener are meant to reflect off surfaces in an uncontrolled way. The result is usually a very huge, but completely unfocussed and indistinct soundstage. That sort of works for large orchestral recordings, but is a mess for smaller group recordings or anything produced using contemporary methods, which demand a clear and focussed location for individual elements. If the OP wants huge/blurry/smeary where you can't pick out the location of any one element of a mix, then he should ignore sdurani's advice.

People get confused with what "soundstage" and "imaging" actually means. I had a client with speakers that radiated a toroidal pattern in a space with brick walls. He called that image "fantastic", I called it an amalgamated mess. We differed. And he didn't sit on the mid-line either.

What non/bi/omni directional speakers try to solve is the problem of poor off-axis response. You do want smooth off-axis response to make speakers sound good in rooms. But the do it by deliberately radiating lots of energy off axis. It's a cheat. And it doesn't work if you want a palpable image in a very reflective room. Controlled off-axis response is much harder to engineer, but works far better in more different rooms with less treatment.

Personally, I find huge/blurry/smeary interesting and fun for about 18 seconds, then disturbing and disorienting. If I play anything I've mixed on a system like that it makes me loose my will to live. If you're stuck with non-directional speakers, you're going to need a ton of fuzz, at least, IMHO.
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post #7 of 18 Old 02-19-2019, 12:28 PM - Thread Starter
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Thanks for all the quick posts and advice from everyone, it really helps alot.

Blacklightning, I could move the speakers a bit more away from the wall, but if I go too far that means the couch has to be pushed back which also means I lose the space for the pool table coming in the near future, so I am trying to avoid that if possible but I know at the end of the day it may be necessary. I looked into REW and it looks awesome, I will spend some more time studying it and learning how to read the graphs it produces.

Sdurani, my initial thought was to cover the entire front wall with absorption panels as well since I get ALOT of echo off of that wall. However like I said, I am a rookie when it comes to this stuff so I was concerned how the recesses would effect it. Do you know if it would? Essentially I was thinking 4" thick panels measuring 2'X4' along the whole upper recess and some smaller 12"X12" panels along the length of the lower recess (as seen in the pictures). Any thoughts on that idea? Do you think I would need additional panels on the lower 3' of the wall behind the speakers?

Jaddie, my sound stage is pretty big with the way I have the speakers oriented now but I do get alot of issues with muddy and indestinct imaging from the reflections. I'm guessing by "fuzz" you mean absorption panels? If so do you think I would only need them on the front wall leaving the side walls bare or should I also put a panel at the first reflection point on the side walls? Doing so would be easy on the right side wall, but the left does have the sink counter so the panel would have to be a little shorter. At this point the side walls don't seem to be doing much harm but it is hard to tell just based on listening alone and not using any scientific measurements. Iwas also considering doing diffuser panels on the back wall instead of absorption, any thoughts on this?
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post #8 of 18 Old 02-19-2019, 01:28 PM
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Do you think I would need additional panels on the lower 3' of the wall behind the speakers?
That's the first place I'd start: the wall space between your speakers. For that section of wall, I would use 6" thick panels, so that they absorb as full range as possible. Panels are usually 2' x 4'. Get 3 of those, rotate them horizontally, place them end to end so that you end up with coverage 12' wide and 2' tall. Mount this on the front wall, a foot above the floor, so that it tops out the same height as the bottom "shelf" in the wall.

You can work your way outward and upward from there using 4" thick panels, depending on whether you continue hear improvements in the sound. The only concern with too-thin panels is that they will absorb the upper mids & highs, acting like a tone control rather than broadband absorption.

The only absorption I like on the side walls is at the contra-lateral first reflection points: left speaker's reflection off the right wall and vice versa. This way, sounds from one side of the soundstage don't come at me (however subtly) from the opposite side of the room.

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post #9 of 18 Old 02-19-2019, 01:50 PM
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That's the first place I'd start: the wall space between your speakers. For that section of wall, I would use 6" thick panels, so that they absorb as full range as possible. Panels are usually 2' x 4'. Get 3 of those, rotate them horizontally, place them end to end so that you end up with coverage 12' wide and 2' tall. Mount this on the front wall, a foot above the floor, so that it tops out the same height as the bottom "shelf" in the wall.

You can work your way outward and upward from there using 4" thick panels, depending on whether you continue hear improvements in the sound. The only concern with too-thin panels is that they will absorb the upper mids & highs, acting like a tone control rather than broadband absorption.

The only absorption I like on the side walls is at the contra-lateral first reflection points: left speaker's reflection off the right wall and vice versa. This way, sounds from one side of the soundstage don't come at me (however subtly) from the opposite side of the room.
What he said. ^^

I'll add that if you can mount any panel off the wall you significantly lower it's lowest effective frequency. Great way to get more absorption without paying for thickness.

From Master Handbook of Acoustics, 5th ed., pg. 191. "Airspace" is the distance off the wall of the absorber panel.

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post #10 of 18 Old 02-19-2019, 01:53 PM
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Jaddie, my sound stage is pretty big with the way I have the speakers oriented now but I do get alot of issues with muddy and indestinct imaging from the reflections.
No doubt.
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I'm guessing by "fuzz" you mean absorption panels?
"Fuzz" is easier to type than "acoustic absorption panel". ;-)
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If so do you think I would only need them on the front wall leaving the side walls bare or should I also put a panel at the first reflection point on the side walls? Doing so would be easy on the right side wall, but the left does have the sink counter so the panel would have to be a little shorter. At this point the side walls don't seem to be doing much harm but it is hard to tell just based on listening alone and not using any scientific measurements. Iwas also considering doing diffuser panels on the back wall instead of absorption, any thoughts on this?
Ideally you'd do front, sides, ceiling and floor. If you can't do that, do front and sides. It's better to do both sides symmetrically. Unequal side wall fuzz will mess up your soundstage. Like if one side wall is fuzzed and the other isn't. Yeah, don't do that.
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post #11 of 18 Old 02-19-2019, 02:01 PM
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I'll add that if you can mount any panel off the wall you significantly lower it's lowest effective frequency. Great way to get more absorption without paying for thickness.
Dang, how did I forget about the air gap? @MD916 , you can get broadband absorption by mounting a 6" thick panel on the wall OR a 4" thick panel 4" from the wall (and save some $).

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post #12 of 18 Old 02-19-2019, 02:20 PM - Thread Starter
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@sdurani , thank you so much I would have screwed this up royally if I hadn't posted on here first. @jaddie , I was also concerned about whether or not they should have a large airspace or not so thanks for letting me know.

My plan was to make the panels myself out of mdf board and roxul insulation, so I have full freedom when it comes to designing the size and mounting position of the panels. I was going to use this video as my guide because it was one of the better ones I came across and it's not above my skill level to costruct.



Does anyone know if these would be inadequate? I can't justify spending $1000+ on panels that are this simple so buying from a fuzz company would not be an option...

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post #13 of 18 Old 02-19-2019, 02:31 PM - Thread Starter
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Link removed from previous post, but it is essentially mdf board frame, roxul insulation, fiberglass screen and fabric.
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post #14 of 18 Old 02-19-2019, 05:20 PM
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@sdurani , thank you so much I would have screwed this up royally if I hadn't posted on here first. @jaddie , I was also concerned about whether or not they should have a large airspace or not so thanks for letting me know.

My plan was to make the panels myself out of mdf board and roxul insulation, so I have full freedom when it comes to designing the size and mounting position of the panels. I was going to use this video as my guide because it was one of the better ones I came across and it's not above my skill level to costruct.



Does anyone know if these would be inadequate? I can't justify spending $1000+ on panels that are this simple so buying from a fuzz company would not be an option...
I've done that project. Waaaaay too much trouble. Owens Corning 703, cover it with a nice decorative (open weave) cloth, hang it. Fabric can be glued on the back, tacks and stables are just OK, but also work. You can leave the back unfaced if you like, stand it off the wall. The stuff in the link is a bit thin, but it's available thicker, you'll have to look around. Cut it with an electric knife or hack saw. Wear a mask (for safe breathing, not to imitate a political figure).

You'll have to cover any and all reflective surfaces that can bounce sound at you. Angle of incidence equal angle of reflection...+20% in this case. You can find the really bad spots using a mirror stuck on the wall temporarily, then looking for reflections of the speaker from your LP. Cover more than you see, and there's nothing wrong with drying up all the early reflecting surfaces. Kind of using a sledgehammer, but you can't really over-do it. You can under-do it, though.
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post #15 of 18 Old 02-19-2019, 09:16 PM - Thread Starter
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@jaddie thanks for the tips, much appreciated. Sometimes a sledgehammer is needed...
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post #16 of 18 Old 02-21-2019, 07:42 PM
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Check out @bluer101 for his theater build. He has some really neat and clean wall panels he’s built (I don’t fully understand how; perhaps he can explain). If think it could be a really nice solution for your front wall, and possibly some other spots.

“The Daydream” Dedicated Theater Build
https://r.tapatalk.com/shareLink?sha...0&share_type=t


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post #17 of 18 Old 02-22-2019, 01:02 PM - Thread Starter
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@Superman07 That's a really nice build. I don't think I have the tools or skills to build the frames the way he did haha. My biggest problem right now is finding a decent price on some 703 panels.
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post #18 of 18 Old 02-22-2019, 01:39 PM
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@Superman07 That's a really nice build. I don't think I have the tools or skills to build the frames the way he did haha. My biggest problem right now is finding a decent price on some 703 panels.


I *think* he has it set up so they stay in place simply through tension. Seems like a small frame routed and then wrapped in fabric. I’m sure you could PM him for details!


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