Dedicated listening room measures

[Matias]

I am about to start building a dedicated listening room from scratch, so I can somewhat choose which measures to build. The architects are drawing the CAD plans these weeks, so I must decide soon.

The area I want is ideally close to 25 m2, and the largest wall can be only 5.0 m. That would leave the other wall only having up to 5.0 m too, but I know that a square shape is terrible for modal ressonances. Height is free up to a reasonable measure.

I have here with me the Master Handbook of Acoustics (5th edition) by Everest & Pohlmann. Chapter 13 deals specifically with room proportions and cites many authors and their recommendations.

And this is where I am stuck. I cannot decide which ratio to choose and apply to my case. Any suggestions?

 

[alex-z]

The biggest limitation in most rooms is the ceiling height.

With absorption panels + multi-sub, you can easily conquer the length+width room modes, but height is a challenge.

I would go something like 16.4ft length x 13ft width x 10ft height, and then build absorption targeted at 140-250Hz where most of the room modes occur.

12ft ceiling would be slightly worse from a room mode perspective, but if you have any intentions towards home theatre, good Atmos implementations need height.

 

[Matias]

@alex-z this would be 1.00 x 1.30 x 1.64 ratio (H x W x L), in meters 3.05 x 3.96 x 5.00 (19.8 m2, 60.4 m3). I think it is possible.

Or using the Sepmeyer B example in the book, 1.00 x 1.28 x 1.54 and applied to my case, 3.25 x 4.16 x 5.00 meters (20.8 m2, 67.5 m3). A little larger as I would prefer. Would it be a good option too?

Or maybe Boner, 1.00 x 1.26 x 1.59 applies as 3.14 x 3.96 x 5.00 meters (19.8 m2, 62.3 m3), a more reasonable ceiling but slightly lower area?

 

[alex-z]

Any of those choices should be fine. Are you doing a double wall structure for better sound isolation? I would take a slightly smaller room with double wall over larger with single wall.

 

[Frgirard]

https://www.whatsbestforum.com/threads/the-myth-of-generic-optimum-room-dimension-ratios.9752/

 

[alex-z]

https://www.whatsbestforum.com/threads/the-myth-of-generic-optimum-room-dimension-ratios.9752/

The OP of that thread said this 5 pages later:

I don't have any measurement gear or software, and never saw the need to get some, because my ears tell me that in my room at listening position things are ok: no modes beating each other, only the 2nd order width mode excited when playing those 3 particular tracks that contain that frequency, I then move the head and it's gone.

The point of optimizing room dimensions isn't some magic that creates good sound automatically. The point is to distribute room modes uniformly so that you don't have overlap magnifying the peaks and nulls. You can make a perfect cube sound nice if you throw corect acoustic treatment at it, that doesn't make it a good idea.

 

[Absolute]

I'd pick room dimensions based on what I would use the room for, not hypothetical golden ratios that become obsolete once you start solving problems directly through absorbers, diffusion, distributed subs etc.

For me the most important aspects in a room is height and width - but it's also important to have space to the back wall. Ceiling height is a free lunch, only benefits to come from that.

Single bass array at the front wall and a fake wall with massive passive absorption behind some well-placed diffusors at the back will solve the bass problems and make for an incredible experience, is this an option?

 

[Frgirard]

The OP of that thread said this 5 pages later:



The point of optimizing room dimensions isn't some magic that creates good sound automatically. The point is to distribute room modes uniformly so that you don't have overlap magnifying the peaks and nulls. You can make a perfect cube sound nice if you throw corect acoustic treatment at it, that doesn't make it a good idea.

In French
http://lespierresquichantent.over-b...portions-acoustiques-ideales-d-une-piece.html

https://sites.google.com/site/francisaudio69/3-la-piece-d-ecoute/3-1-quelles-dimensions-de-la-piece

 

[Matias]

This keeps getting worst. Now I have more than 40 ratios listed and applied to my case in a spreadsheet, apparently no researcher agrees with one another, and some even advise to forget it all as myth or unpractical... I think only a ceiling taller than the standard 2.4 m (8 feet) is unanimous.

I think I will throw everything away and just use something like 5.0 x 4.8 x 3.15 m (24.0 m2, 75.6 m3) and measure and treat the room afterwards.

 

[NTK]

Floyd Toole debunked the idea of the 'ideal room ratio'. His explanation is in the link below (start at page 6).
https://www.harman.com/documents/LoudspeakersandRoomsPt3_0.pdf

A quick summary of his reasons:

 

[Music1969]

I think I will throw everything away and just use something like 5.0 x 4.8 x 3.15 m (24.0 m2, 75.6 m3) and measure and treat the room afterwards.

Meet your future enemies !

https://amcoustics.com/tools/amroc?l=500&w=480&h=315&r60=0.6

 

[617]

I'd focus more on construction with floating gyp and so on than proportions.

 

[Matias]

Meet your future enemies !

https://amcoustics.com/tools/amroc?l=500&w=480&h=315&r60=0.6

View attachment 125656

OMG will I be able to sleep at night knowing I am out of the bolt area "cool kids club"??

 

[Absolute]

This keeps getting worst. Now I have more than 40 ratios listed and applied to my case in a spreadsheet, apparently no researcher agrees with one another, and some even advise to forget it all as myth or unpractical... I think only a ceiling taller than the standard 2.4 m (8 feet) is unanimous.

I think I will just throw everything away and just use something like 5.0 x 4.8 x 3.15 m and measure and treat the room afterwards.

Think about audio and room related issues as problems that needs to be solved one way or another.
You can try to minimize issues by finding exact ratios that spread out modes enough that none becomes too problematic, praying to the acoustic gods that the numbers in theory and the real life reflection ratios from boundaries are the same.
Or you can design a room that will suit your need and just attack each problem in a dedicated way afterwards.

This is one of those audiophile things that just doesn't make sense if very good audio quality is the goal because you'll absolutely need bass absorption, first reflection deflection/absorption/diffusion and distributed subs one way or another if superior sound quality is to be achieved.
Then the golden ratios is a moot point.

In my mind the main benefit of a dedicated room is that one get to plan for those invasive problem-solvers just mentioned. If not planned and executed, why bother with a dedicated room? Shit sounds comes for free in the living room

 

[Wes]

I agree with the above comments on construction of the walls (AND floor) being very important.

And to toss one more fly into the ointment, what about a sloping ceiling?

IF affordable, an acoustic consultant, esp. one who builds small concert halls, can be very helpful. Can be an architect or not.

Also, cable runs in the walls and floor can be helpful - AC flooring runs can be used to simply plug your active speakers directly into the floor outlet so cables are not seen.

 

[Frgirard]

OMG will I be able to sleep at night knowing I am out of the bolt area "cool kids club"??

Don't be afraid. All simulators works with 6 infinitely rigid walls, no doors, no windows.
The real life is other.
Avoid two same dimensions by the use two unparallele partitions.
If you can, do same thing for the ceiling.
10 degrees is enough.

 

[Music1969]

OMG will I be able to sleep at night knowing I am out of the bolt area "cool kids club"??

I would think the best answer is largest that you can do which would then allow you to do the "room within a room" thing, like studios do.

You can have serious absorption built into walls and ceiling and it would hardly be seen...

Best to consult a professional room acoustics expert for this design.

 

[Marmus]

Some thoughts, and I have all the same references. Built 3 sound rooms with no restrictions, well almost. Sloped ceiling and 2 wall sloped were too dead. Very wide 20+ft to 40 ft no big help. Finally went for reduced modes WITH highest sound PL. HxWxD was 11x17x19ft. BUT on the back 17ft wall had a 1ft step in halfway down the wall (floor-ceiling step) and one side wall has 1 foot step. Concrete floor n tile, two concrete walls with 1" wood stop and hard foam behind 5/8 drywall. THEN 20 feet bookshelves floor to ceiling on 2 walls and you adjust your books and kids stuffed toy as need for some great diffusion. Used square foam wedge panels at first reflections, all of them. LG speakers 3' from wall, 8' apart center room. A couple of bass traps (dispersers) (pile of bamboo poles) in corners. VERY best room I have ever had or heard. Used same equipment in all 3 custom rooms and 3 other std ones. 3D sound like the band was there, and the and singer right in front of you breathing on you (horrible I know). One other IMPT thing, power from its own box, one 10ga run for each amp, HD sockets, one run for low power stuff all run to ground star and clean certified ground outside house. All mid fidelity stuff except turntable and CD player. BIG attention to dressing wires and damping all eqpt ( could hit 120decible in there,clean flat best I have heard anywhere. The plans are in a moving box somewhere

 

[Ingenieur]

Page 11 has some good basic proportioning guidelines.
Start with the height and work from there:
Allow h = 2.4 m
w/h < 3, let w be 4, 4/2.4 < 3 is met
That leaves l = 5 and 5/2.4 < 3 is met

Does it comply with this?
1.1 w/h < l/h < 4.5 w/h - 4
1.83 < 2.08 < 3.5

It fits, you may be able to bump the ceiling up a bit, h = 2.5 works with w = 4.5
1.8 < 3 AND 2 < 3
1.98 < 2 < 4.1
Barely

https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1116-1-199710-S!!PDF-E.pdf

 

[Colonel7]

Suggest you take the 90 minutes and watch this. It's worth the time because so much is about the design and wall construction of the room, whether home theater or listening. Dispels some myths too.