# HF Acoustic panel placement questions



## bigbwb (Jan 7, 2009)

Hello fellow HTS members.

I have decided to treat my living room soon now that I have some new tower speakers on their way soon (Ascend Towers). I plan to order several sheets of the OC703 in 2'x4' (2 inch thick) pieces and make wooden frames wrapped in GOM fabric. I am pretty familiar with building the frames and etc since I constructed a theater room a while back using the same materials.

I do need some suggestions on size, placement, etc. First off, after doing some research, I assume the OC703 2" material will be sufficient for treating the 1st and rear reflection points (which are my priorities)?

Secondly, I will post pics of my room and need suggestions on placement and what size panels I can utilize (smaller the better). I am thinking of also making some double (4") bass traps to place behind each speaker under the two windows by the TV since the Towers will be rear ported at the bottom of the speaker, thoughts?

I imagine I need to do the mirror trick and sit in my listening position and slide the mirror along the side walls. How do I determine the rear wall reflections? By looking at my room pics, you will see the back wall is a good 15ft behind my LP(couch) but there are two half walls that cut into the room on each side of the couch just behind me. Suggestions?

Also, ignore the Christmas tree, normally that is gone and the couch next to it is slid closer to the fireplace.
Rear of room looking towards the LP
















Front of room standing between the speakers looking back








Looking to rear again at right corner (same side christmas tree is on)








Looking to rear corner, left side this time.










Thanks,
Brandon


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## eugovector (Sep 4, 2006)

You have a similar setup to mine, though my fireplace is in another room, and I have the whole setup rotated 90 degrees counterclockwise to keep the reflective surfaces as symmetrical as possible.

That really the goal with absorption in an asymmetrical setup, to keep your reflections a little more symmetrical. For instance, to the left of your main position, you have a wall, but to the right you have an opening into another large room. Reflections off that left wall will arrive faster and in stronger intensity than the right.

Leaving your setup as is, I'd put heavy curtains over the windows, a panel above the TV behind your center speaker, and some panels on that left wall to cut back on reflections. You could look to do some basstrapping in the corners, but beyond that, the room architecture makes it difficult to treat.


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## bigbwb (Jan 7, 2009)

eugovector said:


> You have a similar setup to mine, though my fireplace is in another room, and I have the whole setup rotated 90 degrees counterclockwise to keep the reflective surfaces as symmetrical as possible.
> 
> That really the goal with absorption in an asymmetrical setup, to keep your reflections a little more symmetrical. For instance, to the left of your main position, you have a wall, but to the right you have an opening into another large room. Reflections off that left wall will arrive faster and in stronger intensity than the right.
> 
> Leaving your setup as is, I'd put heavy curtains over the windows, a panel above the TV behind your center speaker, and some panels on that left wall to cut back on reflections. You could look to do some basstrapping in the corners, but beyond that, the room architecture makes it difficult to treat.


Eugo,
Thanks for the feedback. After using a mirror to determine my first reflection points, both are just a few feet down each side wall meaning the couch with pillows and blankets might be sufficient to the left while I plan to mount a 2" acoustic panel on the right wall just before the snack bar starts. These first reflection points occur well before the opening on the right wall. How do you feel about that idea?

Also,
How do you feel some 4" bass traps below the front windows behind each speaker would work? Ignore the temporary speakers in the photo, but they will placed in front of each window.
As for window treatments, I do pull down the shades when listening. the shades are the honeycomb type but not room darkening meaning they are just a few layers of material and space in between. Would you recommend the thick room darkening ones for better absorption being my speakers will be directly in front of them?

Thanks for the help!
Brandon


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## eugovector (Sep 4, 2006)

Everything on the front wall should be as broad band as possible, so 4" would be great, but leave them unfaced to adsorb HF also. 

I did recommend the curtains as a way to provide a little absorption on the front wall (goal is a 100% dead front wall for most applications).

1st reflections are a point of contention as some research points to 1st reflections being valuable. My experience has been that, in my smaller rooms, I prefer my 1st reflections absorbed.


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## bigbwb (Jan 7, 2009)

eugovector said:


> Everything on the front wall should be as broad band as possible, so 4" would be great, but leave them unfaced to adsorb HF also.
> 
> I did recommend the curtains as a way to provide a little absorption on the front wall (goal is a 100% dead front wall for most applications).
> 
> 1st reflections are a point of contention as some research points to 1st reflections being valuable. My experience has been that, in my smaller rooms, I prefer my 1st reflections absorbed.


In regard to placing a panel behind the TV and center speaker, should this be a larger panel(for reference the TV is a 61") to cover as much sq footage as possible or just the reflections behind the center channel? Also, would a panel here help with 2ch listening (imaging etc) or just center ch material?

Thanks again!


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## eugovector (Sep 4, 2006)

Ideally, the entire front wall would be covered, but unless you're doing a dedicated room, aesthetics often preclude that. Bigger is better, but if you can't cover the front wall, you should have a 2-4" panel that will absorb lower frequencies behind the speaker to minimize SBIR.

The idea for damping the entire front wall is that the only info you want coming from the front is directly off the recording. Any reflections should be coming from yours sides/behind. This is true for multichannel and stereo.


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## Theresa (Aug 23, 2010)

My living room is almost totally open to the dining room. I've thought of putting curtains between them. I bought three 2'x4' acoustic panels and put one behind the monitor below the center where there was a cavity resonance, and two on the side wall that doesn't have a couch against it. It really helped center the image and reduce the over emphasized highs on the one side. It did make a BIG difference making my L/Rs sound much more like my center. Its an entirely different sounding room. I could use a couple more panels though and some carpeting on the hardwood floor.


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## DanTheMan (Oct 12, 2009)

I actually find leaving the first contralateral reflections intact or diffused perhaps while attenuating/absorbing, damping, etc... the first ipsilateral. I agree with Mr. Vector that killing the front wall reflections is a good idea. The TV may get in the way however. Essentially I'd think a cocoon of absorption around the speakers only open to the room. Like a projector of sound but not too deep as to destroy the ambiance.

Also trying to make the amount and timing of reflections as equal as possible would seem like a good idea. I've tried hard to get it, but have never quite done it.

Dan


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## fractile (Mar 15, 2009)

From here the room doesn't look so asymmetric. The partitions look equal length from interior side walls. There is that obstruction from the door in what looks like an entry, outside the space. You mention high frequency treatment. Window glass will reflect a lot of HF. There are options. A thin 'shade' of translucent foam sheet of 1/8" thick. Open-cell, if found, would probably be best. Many opaque options.

From the shape of the ceiling you might wanna look at that; unless you like the sound. The room is one thing. I think how the room can smear the upper frequencies is important. You could hang some drapes on the front walls to make it look like a theatre.


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## eugovector (Sep 4, 2006)

The front half of the room, the most important part, has a fireplace in one corner and a variety of cutouts on the side walls. That's the very definition of asymmetrical.

That isn't to say that it's bad, just that it's a real-world room, many of us have them, and many of us make them sound great.


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## bigbwb (Jan 7, 2009)

fractile said:


> From here the room doesn't look so asymmetric. The partitions look equal length from interior side walls. There is that obstruction from the door in what looks like an entry, outside the space. You mention high frequency treatment. Window glass will reflect a lot of HF. There are options. A thin 'shade' of translucent foam sheet of 1/8" thick. Open-cell, if found, would probably be best. Many opaque options.
> 
> From the shape of the ceiling you might wanna look at that; unless you like the sound. The room is one thing. I think how the room can smear the upper frequencies is important. You could hang some drapes on the front walls to make it look like a theatre.


The front wall windows do have honeycomb fabric type shades that roll down. I can put them down for serious listening. The room itself is basically rectangular with those small 2' partitions mid way and of course the opening to the kitchen etc.

Drapes are probably out of the question financially and esthetically at the moment. So far I have added a large 2" 36"x36" panel on the right wall just before the snack bar for the right speakers first reflection. I also added a 4" panel below each front window each is the same length as the window is wide for mini bass traps being my soon to be towers will be rear bottom ported.


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