The Terrible listening room discussion!

Our ears are very sophisticated measuring instruments. Better than anything else. Instruments can only measure what they can easily measure. And we don’t know how important what they measure is to our enjoyment of music.

I suggest you trust your ears. There are simple steps to set up speakers in any room by ear.

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Of course you are right, final sign off in our house will be my wife, who despite claiming to have no understanding of what i am ‘messing’ about with, is able to notice subtle changes, like new cables, without prompting. I tend not to tell her as various components are switched in and out of the system. If she cant tell the difference or doesn’t like it, that parts not stopping!

However i am an engineer so I get huge satisfaction applying myself to a new challenge For some its smoking or hard drugs, give me a strong coffee and a fascinating new subject, like room acoustics to study and I am happier than pepper pig in poop😀

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Would shelves of books be any use at scattering and/or absorbing some frequencies of sound-waves on the rear wall (opposite the speakers, behind the listener)?

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You would think it would have an effect. But how to quantify!

Ended up with this bass trap from GIK

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I have tried the same GFK monster bass trap at the same position. It gave nothing for me. So it’s very room and system depending.

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Totally agree and adding 1 panel is very subtle. General advice is many are required to achieve significant change in room response.

Encouraged by the affect of just one, i have 4 x 600x600 traps being delivered tomorrow to try on the opposite wall. 2 of them have built in diffusers

I will report back, with measurements of course!

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Tempted to just bite the bullet and get 2 AVAA active bass traps very expensive but at least my room will not end up looking like a padded cell. Also treats much lower frequency than any passive trap

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I don’t want to sound like a killjoy, but given its thickness, the panel you placed behind your sofa will have no effect on the low frequencies.

For the lower frequencies it’s as if it wasn’t there.

If the thickness of the panel is around 10 cm then you will absorb some of the lower mids and the highs.

If you want to hit below 100 Hz, i.e. the bass, you need a large panel surface and a minimum thickness of 30-35 cm (12-14 inch)

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Yep I know. And the measurements show that too.

The idea was to get some control over all of the frequencies bouncing of the flat wall behind my head. You will see from the measurements there are some timing issues to fix.

Mega bass traps will follow, perhaps the least acceptable for mrs SPB, they will need to be introduced very slowly and with great tact😁

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Yes, it’s always a good idea to absober there, especially if you’re forced to have your listening position against a wall, which isn’t ideal.

Regarding BassTraps, you could use an active system like the AVAA C20 which works between 15Hz and 150Hz. It’s expensive, but no more expensive than pistonic absorbers, and a lot less invasive, more pleasent for Mrs SPB.

In that respect I’m lucky, my wife pushes me to do things the radical way and once and for all.

I have thought about those AVAAs for my room, but given the amount of absorbing material I am placing, I don’t think it will be of much use.

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Another thing i love about this forum i didnt know there was such a thing as an active bass trap…i will investigate further

A nice Swiss product :switzerland: :smiley:


I found with GIK panels it was the sun of the parts - each individual panel didn’t seem to make a difference but when all deployed they made my room acceptable but even then the only speaker I could get to work was a sealed box speaker (ATC SCM40A). GIK were happy with sale or return - I did return a couple and it cost a few pounds in cost but end result was worth it.

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This is correct.

Sorry I can’t contribute much at the moment.

Yes and if you need to hit 40Hz you need 2.14 meters depth if I understand it correctly. 1/4 length of the wavelength. So 40Hz is 8,575m a quarter of that is approx. 2.14m.

If this is correct it seems impossible to treat deep bass with porous material, correct?

Damped membranes & tuned membranes do better.

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Low frequencies… difficult to create and once they’re there, difficult to get rid of. Great! :grinning:

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Indeed, if we want to absorb 100% of the energy at 40 Hz we need both a huge thickness and a huge surface.

Besides, the surface is something that is often overlooked. It is an illusion to try to solve a room mode problem with two 600mm X 600mm panels. We need really a lot of surface.

And there are not only these two parameters to take into consideration : thickness and surface.

There is also the flow resistivity which is crucial to choose well!.

But… we don’t necessarily want to absorb 100% of the energy. A few percent may suffice.

In my context, I chose a thickness of up to 52 cm, over a large surface (23 m2) and with a flow resistivity of 5000 Pa.s/m2. This allows me to absorb 60% of the energy at 40Hz.

But as @Xanthe mentioned, there are other much more efficient ways of absorbing low frequencies. But these are more delicate to implement.

I would say that for the 20-40Hz range the ideal is two or four AVAA C20, not much more expensive than other methods and much, much less bulky.

Unfortuanatly the best GIk absorber, the soffit shows performance as equivalent absorption area


As you say not much going on at 40 hz

That graph is interesting. I don’t understand it. Thomas talks about percentage and I get 0,6. What I don’t get is the 5-25. What does that stand for. What does it tell me?