Acoustic panel room treatment question

#1

I’ve read in quite a few places that a big no-no acoustically is having the sofa (assuming that is the main listening seat) up against the back wall and my very basic experiment of leaning forward on my against-the-back-wall sofa does enhance the imaging a lot but without a dedicated listening room life is often a compromise and pulling the sofa forward isn’t really an option.

I’m assuming that the bad stuff is due to early and strong reflections coming off the back wall so I’m wondering whether a compromise might be to put some acoustic panel behind my sofa to reduce the wall reflections. My walls are white and it’s easy to get acoustic panelling in white, plus if the sofa is against the wall it would look unobtrusive and integrated if tucked behind it.

Does my idea have any merit?

Has anyone done anything similar?

Can anyone suggest any fairly accessible household item (blanket? duvet? cushions from other sofa? something else?) that might act as at least a somewhat effective proxy for a real acoustic panel that I might use to experiment before purchasing proper stuff?

(Kal Rubinson) #2

Cloth-covered (not leather or other reflective materials) sofa cushions would approximate a suitable acoustic panel. Mind you, the acoustic panel, like the cushion, needs to been several inches thick to have an effect into the low midrange.

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(Adam Goodfellow) #3

Correct - avoid sofa against back wall for reason given and agree with above.

Additionally even leather (real of fake) sofas can significantly impact what you hear if they have a high back resulting in the sofa being very close to your ears when lying back on it. Its easy to tell if this is the case as the sound will change quite obviously when you lean forward away from the back. It may become a little less honky.

Perfect critical listening needs your head in open space well away from reflective surfaces for those who need that extreme.

As for you - there are two ways of dealing with reflections:

  1. Absorb them
  2. Disperse them

An ideal room overall tend to have both. Some sound is absorbed by fabric like carpets sofas, curtains etc while some is dispersed by uneven surfaces, uneven books in a book case for example will both absorb and disperse, but of course not to the same extent as something designed for purpose.

The easiest initial test - move sofa a few feet from back wall and get used to how the music now sounds for a while. Now find some means of temporarily hanging a duvet and/or supporting some pillows behind you and see if you notice a difference. Maybe try a curtain or even a large towel just to get a sense of what does what in your specific room.

These kind of things will only impact mid and higher frequencies - remove some honkiness from mid range, reduce harshness of some vocals etc (which can often come from window reflections).

You may find that just moving the sofa changes the sound you are used to quite significantly on its own, especially bass with no further need to change anything. Often an ideal listening position can be 2/3 to 3/4 back into a room from the speakers, but of course that is not always practical.

These days you can often find acoustic panels that can be absorber or diffusors or maybe a combination of both or even lower/mid range traps with the option of selectable or custom prints on them, so once hung on a wall they look like art panels.

Sometimes even fabric art panels given a bit of extra wadding can do a good job. Ive known people who have filled them full of rockwool to make traps of sorts out of them to good effect. (I’m not talking about studio level of good job, just something easy and/or cheap to obtain that will help and wont upset the other half).

The simplest sound test I know of for a room is to stand in the middle and sharply clap your hands. You should hear a nice smooth and reasonably rapid decay with no sense of any frequencies obviously ringing relative to others. You certainly should not hear any flutter echos (very rapid echo - often with a harsh edge to them and probably discernable tones to them).

Of course this is not particularly scientific, but for me I find it pretty good starting point to figure out may be needed, but then I have done treatment for room intended for studio use so I and quite used to listening to clap tests :slight_smile:

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(Chris ) #4

I do that very thing with GIK acoustic panels.

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(Larry Post) #5

The higher frequency (500hz+) reflections are easy to absorb using panels, the real challenge with a sofa up against a wall are the frequencies below 500hz welling up and becoming very thick and congested.

Absorbing these frequencies in a normal sized living room would consume so much volume the room would no longer be usable for living.

My sofa is about 6" from my back wall. One 4’x8’x2" broadband absorber panel from GIK behind my head in the seated position dramatically improves imaging but of course does nothing for the bass. I use dual mono subwoofers to destructively combine and smooth the response in the room and specifically reduce as much as practical the buildup in my prime seating position.

2" thick heavy Rockwool or other is the minimum to get any useful impact. A bunch of thick blankets might give you some benefit but certainly isn’t practical other than to experiment.

A 3-pack of GIK panels is not that much money compared to their relative benefit and need not be permanently mounted. I store them easily in a coat closet in my listening/living room.

I should add, I also used REW to measure my response and had Thierry at HAF create convolution files I load into HQPe. I often listen without panels but music is more involving when I do but less living room friendly.

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(Chris ) #6

The room is always a compromise but this is what I have, there is no option to move the sofa forward but my Meridian DSP 5200 SEs sound glorious here.

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#7

Not all of us have the luxury or WAF to have acoustic treatment. My listening position is also with sofa again the wall, I have no choice the room is not suitable to have a sofa free standing due to door placements. I use DSP instead created by Home Audio Fidelity and this made a massive difference and for much less and attractive than any room treatment.

(Wim) #8

My acoustic panels are Dirac Live. :slightly_smiling_face:
Both in a NAD T 777 v3 receiver and in a miniDSP DDRC24 sitting between the PRE OUT and MAIN IN of my fully refurbished vintage Technics SU-8600 amp.

(Tom Keenan) #9

I’ve tried to identify problem spots using REW (the Room Equalization Wizard). After seeing a null in a specific frequency in the REW output from the right speaker, I looked up the wavelength for that frequency, measured that distance from the right speaker, and found it seemed to land at a big armoire. So I draped a queen sized latex mattress topper over the armoire and remeasured with REW. The null was gone (or reduced).

Well, I decided I could live with the null better than I could live with a mattress topper in my LR. Haven’t decided yet whether to invest in acoustic panels though. I’m not too confident I could repeat the effect after moving the speakers, and am wary of getting into a game of whack-a-mole with REW and foam panels.

(Martin Friberg) #10

Having absorption right behind the head always sound extremely unnatural to my ears, giving that horrible sucking void feeling. Absorb behind the speakers to lower the first wall reflection and disperse using some sort of reflectors directly behind your head is to my ears a much better approach.

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(danny2) #11

I’ve done exactly that and it makes a huge difference. I used to hear echo off the wall behind my head, now there isn’t any. No void or sucking feeling. It probably makes a difference which panels you buy. Some absorb, some disperse, some do both.

(Chris ) #12

When I contacted GIK they have a system to advise you based on room dimensions and pictures. Clearly not everything can be done in a living environment but anything helps.

The first advice I had was to move my speakers further into the room and kill reflections from the back wall. This I have done.
Effective Bass traps would have been impractical due to physical size, but the room sounds great anyway. Meridian DSP speakers have built in DSP and using the corner position and EBA means the bass is nicely controlled and very tuneful.

I am happy and it’s always good to watch people jaw drop on first listen…

#13

For me, there was a similar problem, plus I can not center my listening position in the room. So I built a simple shelf / table construction behind and to the side of the sofa to get away from the walls. This also serves as a table (I have no standing in front of my sofa). At the side and behind my listening position I have sound absorbers. Additional pillows on the shelf behind me. Also sideways wall shelves, plants (which are still crowing) and CDs as diffusers. This solution is not perfect, but I think a relatively simple and cost-effective solution.
I’ve just begun to get a little more involved with room correction, which I think can be tweaked a bit.

OK. Here are some pictures. Shaun (the sheep) is sitting in my main listening position.

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(Larry Post) #14

Tom, I’m afraid absorption nor diffusion can impact a null. The dimensional relationship between the speakers location(s) and walls determines where nulls and peaks will occur. Treatment can help deal with peaks, either using absorption and/or diffusion but short of changing the dimensions of the room or moving the speakers or listening position, there should be no measurable impact on a null.

(Kal Rubinson) #15

The wall behind his head is too much reflection already. He needs to either disperse or absorb some/much of those reflections and doing anything on the other wall won’t help that at all.

(Tom Keenan) #16

Larry, my understanding is that a null is caused when direct and reflecting waves of the same frequency collide 180 degrees out-of-phase. So, my thinking was that if you absorb/disperse sound where it is predicted to hit a wall/object at that frequency (and reflect from it), then you can prevent that null. No? My experiment seemed to corroborate that thinking.

Now, I haven’t repeated my measurement. Being new to REW (and no expert in acoustics), it’s quite possible I got the measurement wrong. Or maybe I’ve misunderstood some basic concept?

(Larry Post) #17

I think you might shift it a little bit but not really affect it much, it will still exist but not be quite as deep. Fortunately, nulls are less harmful in general than peaks.

I like to focus on the peaks and change my listening position to avoid any nulls as practical. Keep in mind, any reasonable sized living space will have peaks and nulls, it’s a matter of managing around them…

(danny2) #18

If you contact GIK they will give you advice on what to do. They are very good - they have an online form that asks you about your room and what you want to do. If you tell them you want a basic inexpensive solution, that’s what they give you. They won’t try to get you to buy what you don’t need.

#19

Thanks all. OP here. I really appreciate all the answers and useful photos. Multiple recommendations for GIK so that looks like the way to go.

Many questions left, mostly specific to my room for me to resolve but also - what music is Shaun the Sheep listening to in that photo?

I’ve heard such rave reviews about the benefits of using REW to set up Roon’s DSP room correction that I think I should get a suitable Mike and give that a go as well.

@florib - I do really like that boxing behind your sofas. I actually get frustrated with the lack of horizontal shelf space in my living room, only the top of a couple of relatively small cabinets that once a couple of table lamps are on them leaves very little extra space. I think boxing similar to yours might work well in my living room to make it look more natural and coordinated to have the sofa pushed 30cm or so into the room which is all I think I’ll get away with and which otherwise becomes annoying dead space because it’s not quite enough space to have any thoroughfare behind the sofa. It could also hide an electrical extension board and a bit of wiring near the floor so that my Roomba doesn’t run over it, give me more shelf space for a few extra bits and pieces, and serve as a mount for a bit of acoustic panel above it. That’s a really clever solution you have there and from the photos you’ve judged the wood finish rather well as well, it goes nicely with the sofas…

(Joshua Hill) #20

I’m in a similar situation and I used the remedy that’s usually recommended, absorption – in my case, three layers of 2" thick 703, which will absorb down to the midbass. But like Martin Friberg, I wasn’t wild about the results – absorption behind my head left an unnatural void without reverberation. So on a lark, I tried some GIK Gridfusors back there. I say on a lark, because the rule of thumb is that you need to be one foot away from a diffuser for every one inch of diffuser depth, and I was right on top of them.

The amazing thing is that it worked brilliantly! I could hear no artifacts from the diffuser, the ambiance was back, and it was a lot better than a bare wall. I do know that diffusers without fins, like the Gridfusors, are less likely to cause problems when you’re too close, but I’m still surprised.

Anyway, thought I’d pass that on. Another thing to consider might be bass traps with scatter plates, which will give you some combination of HF scattering and absorption. If bass is an issue, I’ve also found that the EPS Gridfusors work fine in front of a bass trap (which again can be two 2" pieces of 703 or rockwool). There’s no limitation on how close you can be to a scatter plate, or how many you can put side by side. I’ve debated buying one to try here, but I’m not sure how well it would work so I’m kind of reluctant to shell out the money.