Building a listening room

[Emmett Scully]

Hello,



I want to have a go at making and selling boutique speakers, so I'm going to build a listening room. I wanted to ask the knowledgable people here for advice.



The goal is to have a room which will allow for the clearest evaluation of speakers. To this end I want the walls to be reflective, but for there not to be any issues with the sound which would mask the sound quality.



The internal dimensions in feet are 14x22.5x36.5

The walls and floor will be concrete.

I'm thinking the roof could just be galvanised sheets.



My question is; how can I get a good in room frequency response, i.e. not too rolled off at the top end.



This needs to be cost effective and non-resonant.



Maybe Plywood over the concrete would even the response, and then the right paint over that might improve matters further.



Any thoughts?

 

[Milan237]

Painted plywood will not change anything, for high frequencies it will be the same concrete wall, but the diffusers can help here, they do not absorb high frequencies, but scatter them, so the sound remains alive.

 

[Webninja]

The best listening rooms or studios usually are a box inside a box with the inner box (room) decoupled from the outer. Lots of info online about the drywall layers, stud construction and so on.

On the other hand this is not a typical living room, so maybe something closer to an average room would allow people to hear the speakers as they will sound in their rooms.

 

[Eetu]

Check out these recent Audioholics videos:

Grimani suggests covering ~15% room surface area with absorption and ~20% with diffusion.

Try to bring the reverberation time down to around 0.4 or 0.5 s.

If you fear that the room will end up sounding too dead use absorption/diffusion combo panels (absorption panels with diffusion/scattering plates on top).

Acoustics Insider and Acoustic Fields have a lot of good info as well.

 

[Emmett Scully]

Painted plywood will not change anything, for high frequencies it will be the same concrete wall, but the diffusers can help here, they do not absorb high frequencies, but scatter them, so the sound remains alive.

If Plywood doesn't do anything, maybe it's better not to have it over the wall, so it doesn't resonate.

Is there nothing that could be done to improve the sound in this way apart from diffusers?

What would a concrete room sound like?

 

[SimpleTheater]

Not sure where you live but a few audiophiles have built stunning rooms that, when they move, they will never get near the cost to build it. There’s a place about an hour south of me where the guy had a mini-concert hall built by acoustic experts he flew in from England and California. The room cost him almost 1/2 million but his home is in an area where the homes only go for about $400k. I was in that room a couple of times and it is not just acoustically perfect, but stunning design. When he moves or just passes away in the home, some unworthy soul is going to get that house for a song.

What I’m suggesting is to look around your area at every home for sale, you might find a move would be cheaper than building from scratch.

 

[Milan237]

If Plywood doesn't do anything, maybe it's better not to have it over the wall, so it doesn't resonate.

Is there nothing that could be done to improve the sound in this way apart from diffusers?

What would a concrete room sound like?

I honestly tell you that I am not a big expert in this industry, myself planning to build a studio, but before you start doing something, I prefer to study the question as much as possible forums can take you to very interesting articles that the usual queries on google you will not find yourself.
But in your case, you still have to do acoustic treatment, as I understand you have not studied acoustics and just came to the forum for an answer?

 

[Milan237]

If Plywood doesn't do anything, maybe it's better not to have it over the wall, so it doesn't resonate.

Is there nothing that could be done to improve the sound in this way apart from diffusers?

What would a concrete room sound like?

You do not need plywood, better make a decorative treatment, for example acoustic panels.
It is not as easy to overdrive a room, i.e. to remove high frequencies completely, as it seems, so you should not worry too much about it.
Concrete walls will sound terrible.

 

[youngho]

Hello,
The goal is to have a room which will allow for the clearest evaluation of speakers. To this end I want the walls to be reflective, but for there not to be any issues with the sound which would mask the sound quality.
...
The internal dimensions in feet are 14x22.5x36.5

The walls and floor will be concrete.
...
My question is; how can I get a good in room frequency response, i.e. not too rolled off at the top end.
...
This needs to be cost effective and non-resonant.
...
Maybe Plywood over the concrete would even the response, and then the right paint over that might improve matters further.
...
Any thoughts?

Hi, sounds like you might get more benefit if you provide more details (esp some idea of budget), but your questions as written aren't clear to me, so I'd recommend working with a professional.

Concrete walls and floor will be very reflective at lower frequencies, so will promote standing waves at modal frequencies. Depending on construction methods (stud spacing, use of multiple layers, use of viscoelastic "glue" between them, methods of mounting), drywall and plywood may be allowed "flex" a little, and so some of the standing waves may be damped to some extent. Membrane or diaphragmatic, plate or VPR, or active bass absorption may ultimately be required. Paint will have no significant effect.

 

[Emmett Scully]

Thanks youngho, so your saying stud spacing could be a tunning option. If I wen't with Plywood, what about do you think about thickness and stud spacing relating to resonance?

 

[youngho]

Thanks youngho, so your saying stud spacing could be a tunning option. If I wen't with Plywood, what about do you think about thickness and stud spacing relating to resonance?

I'm not really qualified to answer your questions. I'd suggest taking a look at Alton Everest's Master Handbook of Acoustics, which discusses plywood diaphragmatic or panel bass traps, but the formula for calculating resonant frequency (damped by the use of absorption like fiberglass behind it) only depends on surface density and depth of airspace, but it seems to me that there should be more to it than that, as I would assume that the spacing should have some effect, as well. These sorts of bass traps used to be commonly used in studios (see https://ethanwiner.com/basstrap.html), but they're limited in terms of the frequencies they absorb, so most commercially available products cover a wider range. You're really going to want to work with a professional here.

 

[Somafunk]

Being a new forum member I may be overstepping with the following remark but i can’t help but notice an elephant in your original post.

You say you “want to have a go at making and selling boutique speakers, so I'm going to build a listening room. I wanted to ask the knowledgable people here for advice.”

You then mention “The goal is to have a room which will allow for the clearest evaluation of speakers. To this end I want the walls to be reflective, but for there not to be any issues with the sound which would mask the sound quality.”

There’s not so much a solitary elephant in that statement of intent but rather a herd of elephants followed closely by a pack of cackling hyenas wandering through your reasoning.

Why do you wish to have reflective walls?, this is the antithesis of a correctly built listening room, unless of course you are planning to produce speakers that are actively designed to use reflections to enhance the sound quality, which I doubt you are, have you experience of electronics?, cabinet design?, relevant electrical safety codecs? etc....etc, then you mention galvanised sheeting for the roof, that’d certainly “sing” but for all the wrong reasons.

You have excellent dimensions in the room to begin with but being built entirely of concrete is not ideal, I’d frame the interior keeping the battens isolated from exterior walls and insulate between battens, single skin of foil backed plasterboard facing out onto battens then build another isolated and heavily insulated room inside that room and finish off with a 2ft height of plasterboard around the room for placement of sockets etc, finally a layer of suitable fire retardant and porous membrane material to fasten to the battens and cover that with a material of your choice (check out gik acoustics to see their choice/use of camira fabrics), I figure you’d only lose 20” overall width/depth. But then you have the concrete floor to deal with, so my abbreviated solution is isolated battens and suspended floor filled with tamped sand between battens then either hard flooring or carpet, and the roof?........dunno where to start with the roof if I’m honest.

All sounds a bit “pie in the sky“ to warrant further as there’s fundamental errors in your proposition but If you are genuinely serious then I wish you well, hope it works out but I’ll end with the phrase “I’m out”

 

[FeddyLost]

Is there nothing that could be done to improve the sound in this way apart from diffusers?

I'd recommend you to visit some working studios, the best you can access.
Studio control rooms are made for clear understanding what is going on in the mix. It's really close to your goal, if I understand you right.
Good control room redirect sound energy in specific way, so there's no smearing of audio signal. Like labyrinth for echoes, i'd say.

What would a concrete room sound like?

If you make standard room with parallel walls it will be incredibly bad without room treatment. Boomy with long echoes like in a cave.
If you can simulate symmetrical room with no parallel walls, it might work somehow.
It might look like giant half of egg with measurements in propotion of golden ratio. But I doubt that you'll really will ever build something like that.

Check out this article for example
http://arqen.com/acoustics-101/reflection-free-zone/

But I need to warn you about one thing. If this room must be used not only for your engineering needs (like listening test of different drivers/crossover points) but for testing and promoting your speakers with customers, you need to keep in mind that most of real life rooms are NOT perfect at all.

 

[tuga]

These chaps built a mixing/mastering suite from scratch:

https://www.audiosciencereview.com/...m-mastering-studio-construction-photos.14574/

 

[Emmett Scully]

Samafunk, the reson I want side wall reflections is that thay are important for the stereo phenomenon, they also are part of the total sound you hear in the room, so I need to be able to hear what's happening.
Most people think of side wall reflections as ruiners of sound, but this is only when the speakers are too close to the side walls. I will have mine 6 feet from the walls

 

[Milan237]

I will have mine 6 feet from the walls

What is the distance between the speaker and the listener?

 

[Emmett Scully]

What is the distance between the speaker and the listener?

It would be 10 feet (head would be in the center of the room).
This would be using the golden ratio setup, and would also be an equilateral triangle setup.

 

[Milan237]

It would be 10 feet (head would be in the center of the room).
This would be using the golden ratio setup, and would also be an equilateral triangle setup.

you say that the head will be in the center of the room.
I want to clarify, in the center of the room do you mean between the side walls or just in the center of the room?