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Front wall sound treatment?

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output555

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I know one of things that makes Martin Logans sound great is their dipole design (rear reflecting panels). Unfortunately, due to the constraints of my listening room I have my large CD cabinet directly behind my left Ascent i speaker (the open-faced CD cabinet is 48" wide x 72" high and 11" deep). There is about 35" distance between the front of the cabinet and the back of the speaker. The right speaker has nothing behind it except the wall itself. Each speaker is placed 46" into the room.

Despite this asymetrical set-up, I don't notice a great deal of imaging difference or unequal balance between the two speakers. That said, when I play loud or complicated musical passages there seems to be some smearing and high frequency ringing/echo. The right speaker tends to sound slightly more dominant and with a bit better resolution.

So, I wonder if this current configuration is signficantly compromising the sound. Would there be great benefit hanging sound absorption panels on the front of the CD cabinet (never mind the aesthetics) and on the right-side wall? Maybe the panels will neutralize the difference of reflections between the two sides?
 

DTB300

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output555 said:
Would there be great benefit hanging sound absorption panels on the front of the CD cabinet (never mind the aesthetics) and on the right-side wall? Maybe the panels will neutralize the difference of reflections between the two sides?
Hard to say until some absorption is placed there.

You can do a trial with some blankets and see how the sound changes. Remember the blankets may really deaden the sound, but may give you an idea on how some absorption may work.

You can also pick up some Auralex pretty cheap to try out. The 2" wedge (2'x4' panel) runs $20 or less at place like Guitar Center.

Dan
 

kach22i

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DTB300 has given you some good suggestions, try what is free and cheap first.

My situation was even more complex than yours, I ended up building a movable wall on casters. You may end up with a second CD rack perhaps?

See the link in my signature, system 42.
 

robertawillisjr

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I say move the CD's if you can. I put mine in a different room. Those hard surfaces can't help at all.
 

kach22i

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robertawillisjr said:
I say move the CD's if you can. I put mine in a different room. Those hard surfaces can't help at all.
For the original Aerius speakers which were not bright at all, they like hard surfaces behind them, and soft surfaces between them.

I don't know about the Ascent i speakers.
 

attyonline

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robertawillisjr said:
I say move the CD's if you can. I put mine in a different room. Those hard surfaces can't help at all.
Don't see how this would affect the sound adversely. CD's on a shelf behind the speaker tend to diffuse the sound somewhat. This is esp true for the backwave which is out of phase and time with the primary sound you hear from the speakers. The point to try is to see if you can move the rack and make the area at the back of each speaker as similar as possible, and check the sound quality then. If the sound improves, find another location for your CD rack. If it sounds the same, look for other causes.
 

robertawillisjr

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attyonline said:
Don't see how this would affect the sound adversely. CD's on a shelf behind the speaker tend to diffuse the sound somewhat. This is esp true for the backwave which is out of phase and time with the primary sound you hear from the speakers. The point to try is to see if you can move the rack and make the area at the back of each speaker as similar as possible, and check the sound quality then. If the sound improves, find another location for your CD rack. If it sounds the same, look for other causes.

In general, hard plastic isn't the type of surface you want reflecting sound. It is akin to glass in that it tends to exagerate high freqencies. A shelf of LP's yes, CD's no.

I do agree that if they have to be there, try and equalize the position between the speakers. Usually it's easier to just move them to a different room. Since the room is the most difficult component in our systems to control, I tend to try and keep things as simple and clean as possible. Sometimes we have no choice (in my room I have a rather large glass topped "coffee" table and other furniture. :eek:
 

kach22i

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SugarMedia said:
I think this guy did an excellent job on his DIY panels. I'm probably going to copy it since it's such a clean look.
That's a very nice clean and built-in look. However you should be aware that because of the 2 inch depth you will only be absorbing the higher frequencies.

If you want to capture mid-range frequencies do it like we do for churches. In a church we try to get the mid-range for voice and speech to reverberate correctly. This typically consist of a 3-1/2" deep batt insulation filled assembly (2 x 4's) furred out from the wall (near the roof to ceiling intersection - back wall for sure, sometimes side walls too). Cover with tempered peg board and then fabric covered with Whisper-wall or equal type fabric fastening system.

If you have bass issues you need even a deeper acoustic trap, maybe building a vented false wall a foot or two from the real wall, and or tube traps. Abandoned closets and false ceilings may also be used as bass traps when treated properly.
 

output555

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Solutions for treating front wall reflection

Thanks for the many helpful suggestions.

Moving the CD cabinet isn't an option, that's why I'm looking for workarounds or ways to mitigate the possible reflections off the CDs and cabinet.

I especially like the idea of hanging a blanket on the wall behind each speaker. This seems like an easy, no cost way to test for the differences/improvements of acoustical treatments. If things improve with the blankets, I'll hang some ASC fiberglass panels. Granted, they're only 2" thick so the midrange frequency issues probably won't disappear--I may have to live with them. (A 4" thick panel is way heavy.)

Other, additional suggestions are greatly appreciated.
 

SteveInNC

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I just bought four panels of 2x4x2" wedge Auralex. I'm going to try moving it around to see what effects it gives. It has a NRC of .80, with values of 1.0+ in the mid to high frequencies which is what I'm trying to tame.

I tried looking for Owens Corning 703/705 rigid fiberglass, but it tends to be available only through insulation dealers. I haven't tried that route yet.

OC 703 has a similar NRC rating, and has the advantage of Class A fire rating, as opposed to typical treated acoustic foam like Auralex which is Class B.

Here's a site that goes into the general principles of sound treatments:

http://www.ethanwiner.com/acoustics.html

My room has laminate floors and drywall walls, so it is bright and does have some reflection issues. I'm going to start by treating the primary reflections from the sidewalls. I'm also considering building standing panels to put behind my Ascents. I have bookcases back there now, which tends to diffuse things somewhat. It's my living room, so I don't really want to do grossly apparent treatments. I intend to cover the Auralex at some point (it's purple!).

FWIW, i got my Auralex locally from a Guitar Center store. They sell it mainly for treating studios and sound control rooms.
 

SugarMedia

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kach22i said:
That's a very nice clean and built-in look. However you should be aware that because of the 2 inch depth you will only be absorbing the higher frequencies.
Kach22i,

My main problem is with slap echo, echo, echo and (((Ringing))). I have it big time.

I also have a large & thick lamb skin rug that I place on the floor when I'm listening, but don't find it to be of any great improvement.

I think, at least from everything I've read in the past 6-8 mo, is that I need corner traps and something on the side wall, though I can only do it on One side wall since there is a window on the other. :(

Any thought on what I should use if I want to follow this guys lead on making my own panels?
 
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output555

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OC 703 Source

SteveInNC said:
I just bought four panels of 2x4x2" wedge Auralex. I'm going to try moving it around to see what effects it gives. It has a NRC of .80, with values of 1.0+ in the mid to high frequencies which is what I'm trying to tame.

I tried looking for Owens Corning 703/705 rigid fiberglass, but it tends to be available only through insulation dealers. I haven't tried that route yet.

OC 703 has a similar NRC rating, and has the advantage of Class A fire rating, as opposed to typical treated acoustic foam like Auralex which is Class B.

Here's a site that goes into the general principles of sound treatments:

http://www.ethanwiner.com/acoustics.html

My room has laminate floors and drywall walls, so it is bright and does have some reflection issues. I'm going to start by treating the primary reflections from the sidewalls. I'm also considering building standing panels to put behind my Ascents. I have bookcases back there now, which tends to diffuse things somewhat. It's my living room, so I don't really want to do grossly apparent treatments. I intend to cover the Auralex at some point (it's purple!).

FWIW, i got my Auralex locally from a Guitar Center store. They sell it mainly for treating studios and sound control rooms.
There's a guy on Ebay selling OC 703 at a reasonable price:

http://cgi.ebay.com/CASE-OF-12-ACOU...5561350QQihZ005QQcategoryZ20594QQcmdZViewItem

Also, check out www.insulationworld.com, they have both fiberglass and mineral wool (less $$$) for reasonable prices, but shipping can be expensive.
 

SugarMedia

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output555 said:
There's a guy on Ebay selling OC 703 at a reasonable price:
they have both fiberglass and mineral wool (less $$$) for reasonable prices, but shipping can be expensive.
Yes....quite reasonable prices. :)

What do you guys reckon would be the best. The e-bay site claims it's "acoustic" paneling, whereas the other just calls it fiberglass and mineral wool. Is that just maketing jargon and they are the same?
 

kach22i

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SugarMedia said:
Kach22i,My main problem is with slap echo, echo, echo and (((Ringing))). I have it big time.
What is on the wall behind and above your head?

I have a mirror over the fireplace mantel in that location which is the worse possible thing to have. I have been unable to get the wife to agree to removing the mirror. I did cover it once, that made an enormous difference - positive.

I should say that the back of my head is less than four feet from the back wall. That is just far enough for rear reflections to start their havoc.
 

kach22i

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SteveInNC said:
I just bought four panels of 2x4x2" wedge Auralex. I'm going to try moving it around to see what effects it gives. It has a NRC of .80, with values of 1.0+ in the mid to high frequencies which is what I'm trying to tame.
Not bad, but going off memory isn't speech (midrange) at 500 hz?

NRC of .50 at 500 hz is floating in my head, gotta check out that article, looks very involving and good.

Most small rooms have issues in the bass because of standing wave reinforcement and because of room proportions.
 

SugarMedia

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kach22i said:
What is on the wall behind and above your head?
12 feet deep behind me is an open kitchen. 4 meters above me is a flat ceiling, to my right is a double wide window. To my left is a large flat wall. The floors are wood with solid cement underneath. Like most homes in the EU the walls are solid brick with some cement plaster on them.
 

kach22i

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SugarMedia said:
12 feet deep behind me is an open kitchen. 4 meters above me is a flat ceiling
Unless there are kitchen cabinets hung from the ceiling right behind your head, and it's the back wall of the kitchen which is 12 feet behind your head, I don't think rear reflection is any problem for you. Which is what you were indicating, right?

You have a large place for the EU, are you rich or something? :D
 

SugarMedia

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kach22i said:
I don't think rear reflection is any problem for you. Which is what you were indicating, right?
Ummm... I don't think rear reflection is the problem either. It ssems to come from the front wall, the corners and the sides. Again i do have a clipped wall on my left which leads outdoors.

I get a little confused when you all speak about flatening certain frequencies as I have no idea where and how much should be corrected. I think I need to get soemthing to measure it and post my findings and go from there. Maybe.
 

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