Altering my listening room - size, shape & construction?

I’ve just moved everything into a new room, which will be a dedicated listening room. Early days but encouraging, but it’s clear that it’ll need some acoustic treatment as bass is only apparent when standing up for some reason, and I’ve joined in another thread about panels and such recently. This topic is a little different so I’m very interested in opinions. (Everything is CDX2/XPS2/Hi-line/202/200/Hi-cap2/NAPSC/PMC20.23 plus a Systemdek when I get properly organised).

The new room is relatively small at 4m x 3m (4.05 by 2.96). The rear wall (ie the one the speakers fire against), however, is S-shaped as there are two 70cm deep alcoves, one either side, each half the length of the wall. It is a hollow stud wall and I’m considering altering it to make it straight as this is pretty easy. I’ve two questions about this.

  1. If this is a good idea, what size should I aim at for best results? I could knock out the adjacent room’s alcove entirely which would maximise the listening room at 4.75x3, or extend the adjacent room which would leave the listening room at 4x3 but with an even rear wall. Although a lot smaller than the room I was using, 4x3 is a nice shape. Or I could have it any length in between (perhaps leaving a small alcove to be filled with CDs and LPs). What would you do? Is there an optimum shape?

  2. The rear wall is hollow and if I modify it there is the opportunity to fill it. Having been exploring acoustic panels and bass traps, it occurred to me that if I filled it with the appropriate Rockwool, perhaps I wouldn’t have to consider expensive bass traps and panels on the rear wall. Or, if it was filled, would it become a barrier, thus increasing the need for bass traps? As it is currently hollow, presumably sound just passes straight through it, so would it be best to leave it hollow?

I’m really interested to hear what you think.

@Thomas, @PeterR will have some answers very probably.
If you can place your speakers far from windows, it’s better.

Dsp is probably cheaper and easier. First measure your room using for example REW and a decent microphone.

If your goal is to improve your speakers based system (as opposed to headphones based system) than the first step is acknowledging that your listening room is the weakest element of your audio system.

Unless it is at least 10-12 meters long, 7-8 meters wide and 3,5 meters high, the room is always a problem.

The second step is learning some the basics about acoustics.

But in wrap, there are three steps to improve your listening experience.

  • 1 : listening position is key (sitting against the walls or in middle of the room will always be a problem).

  • 2 : careful speakers positioning

  • 3 : acoustic treatment

Avoid any kind of DSP “tweakery”, at least not if you haven’t gone through the above steps. Even so, playing with a DSP isn’t easy. In fact it isn’t easy at all…

In order to go through the above steps I’d suggest to browse the following thread. I posted some useful links. You’ll find there all the needed info.

–> Don’t buy new speakers – The listening room reality

If your goal is to improve your listening experience, room treatment is, in my opinion, the best way to reach it.

I would never buy a system like the one I have now if my listening room wasn’t treated. It’s like buying a nice Porsche GT Pro and using it in a logging road or forest trail.

Yes, as I say I will be undertaking room treatment, but I also want to optimise its shape, given the peculiar back wall, hence the question about length. By the way, what is DSP?

Digital Signal Processing. The idea is to compensate your room’s frequency response issues by altering the signal your feeding to your DAC.

It sounds simple, but it isn’t.

One might think it is something like:
Oh, I have a peak at 102,3 Hz…
No problem I’ll reduce that by 7dB and I’ll be fine.
Well it isn’t that simple :sweat_smile:

I would recommend that you look at the fabric of the existing room before spending potentially large sums of money on acoustic treatments to fill the room, some of which have to be quite large to be useful, which isn’t ideal in a small room.
First, I would consider the condition of any suspended floor and plaster walls or ceilings. In older houses it’s very common for fixings to work loose, allowing floorboards and plaster to vibrate with the music. Loose debris, badly fixed pipes or wires etc. hidden behind can also be an issue. In newer houses, you would like to think this wouldn’t be a problem, but flimsy, badly constructed stud walls and floors are not unusual. If you don’t fix these underlying problems, acoustic panels will not remedy them.

Next I would look at the room dimensions. The worst possible shape would be a perfect cube, but if any one dimension is a multiple of another, it will still cause trouble. As you are contemplating changes, you should look at the dimensions of the finished room.
Also consider the materials to be used. Make sure that any stud wall uses really sturdy timbers, maybe over-engineer it a bit compared to the bare minimum a builder would use. Then use a double layer of plasterboard.

Once your room is ready, I would get a calibrated microphone and run REW to measure your room acoustics. If the results are confusing, maybe get them analysed by a professional, then you will be in a position to use superficial room treatments to target actual issues if there are any.

Good luck!

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I went through your message a little briefly.

If you’re lucky enough to able to choose your listening room dimensions, do it carefully.

I believe the following tool could be of some help:

As for the shape, a parallelepipedic room is probably the best choice. Room modes are predictable and therefore the type of treatment.

If you’re considering going through the room treatment yourself, here is an online store were you may find the needed materials or at least take some ideas:


Be careful with your choices in terms of materials.
You don’t want to overkilling medium and high frequencies.

Foam panels, curtains are generally not the best option (unless you know what you’re doing).

Foam and fabric absorb mids/and. They do not absorb bass (low frequencies), not at all.

What you want is an even decay time throughout the frequency range (the waterfall plot, in case you use REW).

To be honest, this is almost impossible to achieve in a small room. But you can better things a lot!

In the context of your room (small), do not use diffusion, or be careful with it.

And remember : there is no such thing as too much bass traps! :wink:
The more you add, the more you’ll flatten the low mids and lows frequency response. And this is exactly what you want (what we all would want!).

Nice project, have fun! :smiley:

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