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Diffuser or absorber behind listening position....and is it worth doing??

I am a relatively new to serious two channel listening so I don't have a lot of experience to rely on. However, from what I have read on this site I do feel pretty confident that improving my room acoustics via absorber and defusers panels will be the best way to improve SQ at this point. Unfortunately, because my listening room doubles as my living room the only place I can only use panels ( no base traps) and only behind my listening position.... hence my title question. What say you.....will I benefit from adding diffusers? Or should it be absorbers? or forget it and be happy with what I have. (which I am.... )

Here are some room and placement specifics:
Room 12 ft by 18ft 
Speakers (ribbon tweeter) on Long wall with large window with wood blinds on right and drywall on the left
Speakers baffle are 32 inches off front wall and 48 inches off both side wall and are 10 ft apart with a 6x9 rug.
Sitting position can be either against the wall or 2ft off the wall (just slide couch forward....which I do because sound stage and imaging is better).

My main goal is to improve imaging and stage. If it is worth doing, would there be any other benefits? Also,
could you recommend how large a space should the panels cover..... how thick panels should be?

Thanks in advance



 
mrpsync
lemonhaze
409 posts
 
The advice to acquire a mic and download REW or HolmImpulse, as used by Earl Geddes and also free, is solid. Playing with this allows you to see the results of added treatment.

The basic problem all rooms have is the sound taking too long to decay and the use of EQ simply can not reduce the decay time, it needs to be absorbed and the OC703 you bought is great for the job.

tomic601 mentioned RT60. This is the time it takes for the sound bouncing chaotically around your room to decay by 60dB. and without looking up the figure for your size room would, I guess, be about 400ms. So if you see some frequencies with a T60 of 1 sec. these are the ones to be tamed. Then after introducing and/or moving some more treatment take another shot until you achieve an even smooth response across the full spectrum. Great fun.

By doing it this way you avoid any guesswork and will come to realise that the suggestions to hang a drape or install a thicker carpet is like trying to win the jackpot.

The thicker the absorber panel the greater the range of absorption. So 6" will be more broad-band than 4"  Move away from the back wall and use absorbers. You would be too close to a diffuser on the back wall.

Have a good read of this: https://ethanwiner.com/acoustics.html#bass%20traps
hilde45's avatar
hilde45
4,783 posts
 
@mrpsync  I'm glad my diary of attempts was helpful. I really fumbled a lot in the beginning, but earnestly. You did well buying 12 panels, by the way. That gives you sufficient quantity to actually do some very real experiments, especially, as Lemonhaze points out, using 6" panels. You can really affect bass peaks with that thickness if it's also some distance from the wall.

The other thing I'd add is that you should not get too hung up on building frames for these panels; fabric that is adequately transparent (burlap, muslin, etc.) will protect you and enable you to move things around. 

One other helpful hint I got early on was that if you're trying to troubleshoot a ceiling first reflection point and it's a pain to get a pad up there, try one on a spot below on the floor. That should help show some difference without all the ladders, staple guns, and cursing.
mrpsync OP
31 posts
 
Yeah, I think Tomic also mentioned that he did find a need to frame panels either. I definitely welcomed that bit of info. Actually not having a frame will probably have other benefits too. For example not dinking furniture and scratching walls due to regular movement when setting up and storing.

Ceiling reflections are a concern since I won't be able to address it with panels. So I'm hoping  that it won't be to significant since my tweeters are ribbon, which have a more limited vertical dispersion than a typical dome tweeter..(so I've been told). And the fact my ceiling is 10 ft, and my listening position is about about 6 1/2 feet from speaker plane. So between the tweeters angle of dispersion, ceiling height and the "somewhat" near field listening I keeping my fingers crossed that first reflection points won't be an issue. maybe, just wishful thinking:) 

Lemonhaze - Appreciate the link and explanation about how delay is an issue. Your position on measurement, along with others; is driving home the point that I will need to do this as some point. I'll cross that bridge when I get there. I'm sure that it will my second thread:)

Thanks
martinb0820
19 posts
 
My room is about the same size as yours, and due to the location of a fireplace there is no choice but to put the speakers on the long wall.

This is a long thread, so maybe I missed a relevant comment. If so, please excuse the repetition.

I wasn't sure whether to use absorption or diffusion behind the listening position. GIK recommended diffusion, but just in case, I ordered three large 4A Alpha panels, with the backs optionally covered with fabric ($12.00 per panel) instead of the default white muslin. That way they could be used for diffusion + absorption or turned around for absorption alone.

After experimenting, I ended up mounting them on the wall with the diffusion side out. That may or may not be the best approach for your room, but at least the reversible panels allow you to easily find out.
danvignau's avatar
danvignau
935 posts
 
My sister, who manages some bands, and owns one she put together, suggested experimenting with comforters on the wall behind me, but since it is 25' away, I did not bother.  My stereo listening room is literally 3/4 of my house and has high ceilings,  but this might be good for you to try.
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