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In Reply to: RE: Treatment for rear wall behing speakers posted by Vinyljunkie100 on November 05, 2007 at 13:43:15
Those doors are not going to make things easy to improve over what you have already done.
Is it possible to use the other end of the room for the speakers, or is there a large window there?
Barring that approach, and a more conventional arrangement of sound absorbers, there are a few things you could do.
Use the other two sound panels in the rug area, and use them to cover as much of the still bare wall (not covered by the rug) as possible.
Make some DIY corner tunes (do a search) for the front corners, and move the sound panels along the top rear wall toward the middle to make room for the DIY corner tunes.
It looks like you have a window on the left of the left speaker, and a wall on the right of the right speaker, this can be a problem for imaging, and the best way to try and 'equalize' the two side walls acoustically, would be to use some DIY room lens at each location.
Treating the whole rear wall, while it may do some good, should not be done with a too thin layer all over, which is what it sounds like you are proposing. The spot approach with thicker panel's or absorbers is better. In your case, there is so much 'door' on the rear wall, that it just makes it harder to do some good. The doors are unbalanced too, and this is also a problem for the remaining space and where to place the absorbers,
Symmetry is best, and even if it means less total absorbing material.
Removing drywall to install fiberglass can work, it is a 'brute-force' approach, but it's effectivenes is much less than that of the Tube Traps, unless you make the amount (depth) of fiberglass as deep as 6-8", instead of the 2-3" that a 2X4 depth allows. Thus, in order for it to be very effective, you would need to "lose" some room volume, by bringing the surface of the fiberglass covering out into ther room.
Yeah, I know, nothing really good is ever easy.
Try replacing the rug with an nearly equal area of thick fiberglass (at least 6") temporarily, center it with respect to the speakers and the room, and see if that does it for you acoustically.
Good luck!
Jon Risch
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I could flip it around to opposite wall. That would mean that I would have components no longer in closet, which would in turn mean that my stand (Arcici Suspense walnut replica)would have to jet out from back wall between speakers (28 inches or so). Other reason is open on one wall (see pic), don't know whether this also would be bad.Other wall is bank of windows covered in gel things and a heavy curtain that is closed when I listen. I give it a try if you want, but understand that to move this would involve moving records to another room (1000 records are heavy), loss of records as acoustic help, and subjecting my tube equipment (Art Audio Vinyl One, AR LS-17, and Sota turntable with SME 5 arm and Koetsu cartridge)to the blows of the Vandersteen rear firing woofer. But if the sound will be better, I'll give it a go.
I will definately build the DIY corner traps as suggested by you and unclestu.
I will also experiment with a fiberglass sheet as you suggested. I agree about the symmertrical as the sound, to me, always seems to chase the acoustic panels. It is very noticable when the center panel is off, even a couple of inches, how the center image will shift with treatment.
I really dont want to stuff 6-8 inches of drywall in rear wall so I'll take that option off the table. Should I just build one of your panels and hang it in center for more absorption that ASC planks. I guess I'm also stuck with the tube traps in the corners.
I will also check out the diffussors. I havwe some extra walnut, and I bet I could make them pretty.
Thanks for your time and help,
James Locke
Maybe I can help here. I've got a L-shaped room and the toe of the L is behind me and to my left, like the space through your open archway. My right speaker faces a wall to my right just behind the plane of the listening space and the left speaker faces a wall 3 metres further back than that.
Pretty much everyone here has been very strong on symmetry for very good reason. The soundstage tends to become unbalanced when things are asymmetrical. In my room, if I remove the acoustic treatments the soundstage pulls strongly to the left where there is a stronger reflection from the wall since I also have an open arch to the hallway on the right of my right speaker. Those problems can be dealt with but they can sometimes be difficult and it's often hard to predict what will work best in advance. Dealing with asymmetric rooms can be a real puzzle.
If you rotate the room 90 degrees to the left, which I think would have some advantages, these are my suggestions:
1-rotate the bass traps on the wall behind the speakers 90 degrees as well;
2-cover the windows with heavier drapes than the sheers already there. It is also possible to get noise absorbing curtain liners intended to block outside noise by absorption. They absorb internal sound as well. Use them if possible. You won't see them, they're a second curtain hidden behind the first one, so people won't notice and that's a good thing with acoustic treatments in many ways. You can open the curtains when you aren't listening so that the room is more light but the room will be dim if you do a fair amount of daytime listening.
3- the right side (the wall currently behind the speakers) may need some treatment and you've got some there already. It may be enough so start off leaving things how they currently are and spend some time—I mean a couple of days—just listening to things with the speakers and bass traps moved 90 degrees to the left and some absorption on the windows behind the speakers. In the short term before you get heavier curtains there, you can simply try some gel thingies on those windows and just hanging a blanket or two from the existing curtain rail to get an idea of what things are going to be like. That also allows you to shift things back to where they are now without having made any big expenditures if you don't like it.
4-if you find the soundstage pulling to the right, then there's too much reflection from the right side. Locate the early reflection point (location will depend on where the sofa or chairs end up) and treat the area there along the lines Jon Risch suggested. If the reflection point falls on one of the doors (I think that's unlikely), use a free standing acoustic panel in front of the door.
5-leave the discs where they are on the left. You may need to put some absorption there if the soundstage pulls to the left but if you do simply use a free-standing panel placed in front of the discs at the site of the early reflection point. You're going to have to juggle what you do on the left and right at the same time because one will affect the other but the trick is to use absorption to balance things. You won't succeed very easily if you try increasing the reflectivity of the side that's lower in reflectivity but simply using absorption on both sides will balance things and it also helps produce a stronger soundstage into the bargain.
6-that leaves the wall behind you, currently the right wall. There's going to be a bit of experimentation here and it may take some time to get things right. I'm going to assume that you aren't going to want acoustic treatments in the adjoining space. The options that I would be trying, based on guesses of how things will sound, are:
a) play with speaker toe-in;
b) bass traps in those 2 room corners also;
c) absorption on the wall area next to the archway;
d) a free standing panel behind you to block some of the reflected sound from the other room. It would need to be a fair sized panel, the full width of your sofa if you keep the sofa, but otherwise around 3' or so wide at least, the size Jon Risch recommends as a minimum for his DIY panels.
You may or may not end up having to use one or more of those suggestions but I would bet on having to use one or two. Speaker toe-in will make a difference and I have my speakers pointed directly at the listening position because that puts me on axis and ensures any reflections from behind me or from the wall to my right that the right speaker faces are going to weaker because they're coming from further off axis than the direct sound. That fact helps a lot and actually lets me get away without having to treat the wall my right speaker faces. Playing with toe in is simple, free, and easily reversible. The only down side is that it can be time consuming.
It's hard to predict what that room that will end up behind you will do to the sound. It will create a problem of some kind, but it also gives you a longer dimension for one speaker to fire into and that will provide a lower standing wave frequency which, while it sounds problematic, need not be and it can actually help since the lower the lowest standing wave frequencies, the earlier the room's sound starts to smooth out. The problem with standing waves really isn't that they exist, it's that there's only two or three per octave at low frequencies. When the number builds to 5 or 6 per octave there's enough overlap to start smoothing out the dips and peaks in room response and this happens earlier (ie at a lower frequency) when the lowest standing wave frequencies are lower in frequency.
So there's some suggestions. The 90 degree rotation may actually end up being relatively simple with the exception of what you do with the open entrance that you end up with behind you. Even that may not be too much of a problem but that's impossible to predict and it is going to be a matter of trying the rotation to find out.
Hope the above ideas help somewhat.
David Aiken
Now that I have seen a photo of the other end of the room, Dave's suggestions have merit, and would be at least as effective as totally reversing the room, etc.
For a quick taste of what it might sound like, adn without moving all of your gear, etc., use some long temporary speaker cables (even 12 ga. zip cord would be good enough for a taste of the soundstage and overall presentation), and experiment with the speaker placement, toe-in, and the placement of the acoustic treatments.
Then, once you find a set-up you like, decide what to do permanantly in terms of the location of the gear.
Jon Risch
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