Repeat, my experience is limited by 4 cases. The very impressive case when SPL-peak was suppressed by 50 (!) dB. Basscleaner was equipped by round lid from wood (about 30 mm  thick) and maximum effect was when gap was about 3 mm. Very first time this effect was discovered under strange circumstances. Ten years later, something similar was described in the  conference article. I've got it on Russian, but there is no time to translate. If somebody wants, I can send it by E-mail. In particular, authors mention on additional Schlichting waves as additional peculiarity, connected with simple tube resonance and reinforcing sound absorption. I can not confirm or deny this.

You're the best Kieth, thanks for posting this stuff.

As I told you a while back (you may have forgotten) I'm a tradesman and I'm going to build a listening room (H/T) in my garage that I don't use. 

Internal measurements will be 6.4mtrs L x 4.27mtrs W x 2.79mtrs H.

AMROC spat out RT 60 = 0.6sec

Walls will be timber frame/plaster board (with acoustic insulation behind). Walls, concrete/timber floor and ceiling will all be separated and I'll be using isolating clips to hold the plasterboard fixing channels. The only treatment I'm going to build-in are deep bass traps (with a central air gap) in all vertical and upper horizontal corners. Coverings of these are yet to be determined (open to suggestions!)

As I said to you in PM's I'm keen to get the room right but I'm not confident with working the acoustic measuring tools so I will be approaching you again in the future! 

Love reading your work mate, much appreciated.

Tony

(Reminder that my speakers are ATC50's with Perlisten D12S subs)

Edited October 7, 2025Oct 7 by Toeknee

10 hours ago, Toeknee said:

Internal measurements will be 6.4mtrs L x 4.27mtrs W x 2.79mtrs H.

Hi Tony,

 

that will be a nice sized room!

 

Single layer Gyprock on isolating clips will provide pretty good compliance in the walls to absorb low bass energy to reduce it bouncing around within the room, but if you want to improve isolation also (ie prevent low bass leaking out), a double layer of Gyprock with Greenglue between, in conjunction with addressing flanking paths, will significantly reduce sound leakage into and out of the room.

 

I've likely linked it earlier in this thread, but anyone planning construction of a listening room should review all the great material on this site: https://www.soundproofingcompany.com/soundproofing-101

 

If you like to crank your music at unreasonable times and not upset others in the house or next door, improved isolation is a must.

 

I have a lightly constructed room where all the low bass leaks out, and a bunch of absorption cleaning up down to 250Hz or so.

My "in room" bass response is tight and dry with no overhang - gloriously visceral when cranked...

...fortunately I have a tolerant family and neighbours...

 

...but I don't crank it for long, and I never crank it at unreasonable hours.

 

Sound proofing/sound isolation can only be addressed at the construction phase.

My listening room was just the spare room downstairs when we moved in - the absorption I've added helps the "in room" sound, but doesn't change the sound isolation characteristics of the room at all.

 

Given you're about to construct your room, I would strongly recommend building in some isolation also, using the principles in the link I provided above.

Being able to crank the volume when you want is a good thing!

 

cheers,

Mike

Thanks @Toeknee I am glad you found it helpful. Of course I am happy to help you take measurements and interpret them, but I have to remind you that I am not a professional acoustician and I certainly don't know as much about acoustics as they do. I know enough to understand what they are talking about and to be an educated consumer. The aim of this thread is so that everyone can be an educated consumer. 

On 07/10/2025 at 9:20 AM, Toeknee said:

 

Internal measurements will be 6.4mtrs L x 4.27mtrs W x 2.79mtrs H.

 

 

As you are building from scratch, maybe build it to the 'Golden Ratio'?

 

In which case, as your length is 6.4m, make:

• the width 0.618 of this - so 3.95m
• and the height 0.618 of the width - so 2.44m

 

Is there such a thing as ideal room dimensions, or an ideal shape? 

 

Toole answered that question in his book. A number of studies have been published over the years trying to mathematically prove that there is such a thing as an ideal room ratio. All have failed because the authors made some assumptions that do not hold true in real life - that there are no openings, that the reflectivity from all surfaces is equal, that the position of listeners and speakers are fixed, that all rooms are rectangular, etc. 

 

With more modern ray tracing software, it may be possible to come up with an ideal room or room shape, but the position of speakers and listeners would have to be baked in to the design. @Grizaudio would know more. But for now, we can say that the golden ratio, or Cardas ratio, or any other ratio has not been proven to be any better than any other ratio. All we can say is that "bad" ratios (e.g. 1:1:1, or 2:1:1) certainly exist. 

Aah, ye of little faith, @Keith_W!  The ancient Greeks knew a thing or two.

 

I used the Golden ratio in the design of the 'music room' at the Prahran house.  (Although I didn't use it for ceiling height, as I thought a /\ ceiling would be better than flat.)  If you recall ... it 'sounded' pretty good.  😀

 

It sure did!

On 09/10/2025 at 12:06 PM, andyr said:

 

As you are building from scratch, maybe build it to the 'Golden Ratio'?

 

In which case, as your length is 6.4m, make:

• the width 0.618 of this - so 3.95m
• and the height 0.618 of the width - so 2.44m

 

Thanks Mike (will do) and Kieth.

Andy I've done a lot of research myself and I've learned that there is no perfect golden ratio.  Many golden ratio measurements you find on the internet are a basic formula and often different from one another, this is because all frequency waves work in different distances. So when you're designing a room you just have to make sure that none of the three room dimensions divide neatly into one another, that's basically what a golden ratio is, non divisible measurements.

A good way to find a great room is to punch in your preferred measurements into the AMROC website (start with one of the golden ratio nominations if you want) and then start adjusting the measurements until you see a good outcome. My measurements should be solid, the Bolt area is nicely placed. 

Edited October 11, 2025Oct 11 by Toeknee

1 hour ago, Toeknee said:

Andy I've done a lot of research myself and I've learned that there is no perfect golden ratio. 

 

The (classical Greek) 'Golden ratio', Tony can be expressed as either '0.618 : 1' or '1 : 1.618'.

 

So a 5m wide room that was based on the GR would have:

• a length of 8.09m
• and a height of 3.09m.

 

Edited October 11, 2025Oct 11 by andyr

Duplicate

Edited October 11, 2025Oct 11 by andyr

I agree with @Keith_W and @Toeknee - there are room dimension ratios to avoid (eg even multiples), but no golden ratios.

Build the biggest room you can, with the level of isolation/sound proofing you deem sufficient.

 

If you follow the guidelines in https://www.soundproofingcompany.com/soundproofing-101, you will achieve an appropriate level of sound isolation/proofing and a compliant room where the walls/ceiling absorb low bass (ie the walls/ceiling operate as a large membrane bass trap, soaking up bass), requiring significantly less "in room" treatment for bass frequencies, or maybe none at all...ie EQ may be sufficient to have the "in room" bass entirely under control 👍

 

Mike

2 hours ago, andyr said:

 

The (classical Greek) 'Golden ratio', Tony can be expressed as either '0.618 : 1' or '1 : 1.618'.

 

So a 5m wide room that was based on the GR would have:

• a length of 8.09m
• and a height of 3.09m.

 

As I said Andy, I've researched the topic and I'm fully aware of the golden ratio you have mentioned. The idea of the 1.618 is a patterned occurrence in nature and a good place to start when designing.

The leading guys in this field all agree that there is no set of 'golden ration' room measurements (and throw the trapagon in here as well) that will perform perfectly with all frequencies. As you would already know, room behaviour is a hard puzzle, its not just measurements, it's the building materials used, density, surfaces etc.

The thing is you will still get nodes, peaks and standing waves in a golden ratio room (obviously less that a square room but you still get them). Treating the room correctly is the only way and to do that, and to do that we need to take measurements and apply solutions.    

One thing that may work is to have the walls not square with each other ,

I work with the chaos theory , stuff everywhere ,within reason ,so 

sounds reflect on surfaces ,of uneven dimensions ,

I do have a kind of absorbing and reflecting areas , 

there was a Hi fi  shop that had two rooms virtually identical in size 

but the rooms sounded quite different , never worked out why ,

So only  so much can be done pre build ,

the fit out will be the major issue to work with 

 

12 minutes ago, colinm1 said:

One thing that may work is to have the walls not square with each other ,

 

Yes, that's a very good idea.

 

For that reason, I built the ceiling in my preious house with a '/\' ceiling running the length of the room.  The roof angle was 100 deg - chosen to diffuse slab-to-ceiling reflections.  As I said, it had GR dimensions for length & width - and it sounded very good.

 

The only 'room treatment' it had was a 1" cork 'art work' running along one of the long walls ... to stop 'slap echo'.

 

And in my current house, building regs for a multi-storey house mean that the long wall behind the spkrs is sloped; again, length & width (of the floor) are GR-related - and this room has no problems, either.

 

On 09/10/2025 at 3:47 PM, Keith_W said:

@Grizaudio would know more. 

 

Hi @Keith_W

 

My understanding...

The golden ratio is more concerned with modal behaviour from what I understand, its not a full spectrum strategy. 

The goal of the ratio is to limit bunching of modal activity, and even out bass response in room.  

 

...but.... factors like speaker selection, directivity, point source energy output, DSP, listening position, and in room acoustic treatments all have a board impact on the entire frequency spectrum. How can you design 'the ideal space' without considering all these elements. 

 

Furthermore, how do you model a residential speaker, in room with no GLL file? 

 

Anyone who has ever played with EASE, or other professional modelling packages, understands the speaker massively dictates the in room acoustic result.

 

In the world of commercial or pro speakers [speakers which have EASE data], modelling direct field energy, and/or ray tracing a space/setup is all possible, however this modelling becomes very inaccurate in modal bandwidth. So, I guess, using a golden ratio is better the nothing. At least modal activity is considered. 

 

edit. .....but perhaps you would be much better modelling the modal activity in REW, using actual subwoofer/speaker placement... and the golden ratio as a starting point. 

 

 

 

 

 

 

Edited October 11, 2025Oct 11 by Grizaudio

Hmm, if we are designing a room from scratch, it is worth remembering that long wavelengths and short wavelengths have different requirements. 

 

Long wavelengths will form room modes. They will always form modes, regardless of shape, ratio, and size (within reason). They will form fewer modes if the room has a large opening to another space, e.g. adjoining dining room. Regardless, we should accept that modes will form and we need another strategy to deal with them. The only time modes won't form is if a half wavelength is longer than the room - this is so-called pressure mode. For most listening rooms, this will occur very low, about 25-30Hz and higher for cars. But you still get room modes above this frequency. 

 

Short wavelengths have a completely different consideration. You want the reflections to arrive delayed, diffused, and attenuated. The only way to achieve the delay is to have a larger room. The minimum delay considered "ideal" is 5ms. Sound travels 0.34m in 1ms, so for a 5ms delay, the reflection has to travel an additional 1.72m compared to the direct sound. 

 

 

Most "decent sized" listening rooms I have been to are about 4m x 6m, which I have quickly drawn in Sketchup. You can see that if the speakers and listeners are placed in the locations indicated, the reflection path travels 4.35m in total. Since the direct sound travels 3.2m, this would give a delay of 1.15m, or about 3.35ms. It is still short of our 5ms threshold. You might be able to improve things by sitting a bit further away. 

 

Anyway, as can be seen, the priorities for speaker placement are completely different for high frequencies and low frequencies. For high frequencies, we want to position the speakers for best possible imaging - reflections need to be delayed for as long as possible, placement needs to be symmetrical, and so on. But for low frequencies, we want the speakers placed where there are as few dips in the FR as possible. It is rare that the two positions coincide. This is why we use subwoofers, it removes low frequency placement constraints on the main speakers. 

Oh yes @Grizaudio, some time ago you sent me a link to i-SIMPA ... freeware room modelling software. All you need is a CAD file, which you can generate with Fusion 360 (freeware CAD program). Unfortunately, my CAD skills are very limited. But it does look feasible for someone who knows how to CAD to be able to acoustically model their room. 

22 minutes ago, Keith_W said:

Long wavelengths will form room modes. They will always form modes, regardless of shape, ratio, and size (within reason). 

 

I think most people understand this. The golden ratio - is about minimising bunching of these modes. 

 

22 minutes ago, Keith_W said:

You want the reflections to arrive delayed, diffused, and attenuated. The only way to achieve the delay is to have a larger room.

 

This is not the only way. You can also use absorption/diffusion, or indeed controlled directivity speakers, to maximise the direct energy vs reflected energy ratio. 

 

22 minutes ago, Keith_W said:

Anyway, as can be seen, the priorities for speaker placement are completely different for high frequencies and low frequencies

 

100% 

Edited October 11, 2025Oct 11 by Grizaudio

11 minutes ago, Keith_W said:

Oh yes @Grizaudio, some time ago you sent me a link to i-SIMPA ... freeware room modelling software. All you need is a CAD file, which you can generate with Fusion 360 (freeware CAD program). Unfortunately, my CAD skills are very limited. But it does look feasible for someone who knows how to CAD to be able to acoustically model their room. 

 

I haven't played with this software -yet.

You'll still need some type of acoustic data for the point source. I.e. FRD, GLL, etc. 

28 minutes ago, Grizaudio said:

This is not the only way. You can also use absorption/diffusion, or indeed controlled directivity speakers, to maximise the direct energy vs reflected energy ratio. 

 

Respectfully disagree. 

 

Re: absorption. Attenuates but does not delay. 

 

Re: diffusion. See Toole Ch. 7.3.2: 

 

 

Not mentioned in Toole is that diffusers do not add additional delay, unless they are very large. For example, a large convex surface mounted on your wall will change the direction of the reflections and lengthen its flight path, which will increase the delay. But I don't think most people would want to do that. 

 

Re: controlled directivity speakers. This changes the ratio of direct sound power to total radiated sound power, i.e. the DRR (Direct to Reverberant Ratio). It determines if the critical distance is longer or shorter. Nothing to do with delay. 

30 minutes ago, Keith_W said:

 

Re: absorption. Attenuates but does not delay. 

That's kinda where I was going. 

If the potential reflections are suppressed 'enough', is delay needed? 

 

30 minutes ago, Keith_W said:

Not mentioned in Toole is that diffusers do not add additional delay, unless they are very large. For example, a large convex surface mounted on your wall will change the direction of the reflections and lengthen its flight path, which will increase the delay. But I don't think most people would want to do that. 

Diffusers do alter the perception of delay though, by scattering the reflected sound, and making some of the energy less noticeable/coherent. 

 

 

30 minutes ago, Keith_W said:

Re: controlled directivity speakers. This changes the ratio of direct sound power to total radiated sound power, i.e. the DRR (Direct to Reverberant Ratio). It determines if the critical distance is longer or shorter. Nothing to do with delay. 

I was purely thinking about keeping energy off surfaces - Keith. 

I.e. minimising reflected energy - to listener. 

Edited October 11, 2025Oct 11 by Grizaudio

53 minutes ago, Grizaudio said:

That's kinda where I was going. 

If the potential reflections are suppressed 'enough', is delay needed? 

 

Well, you and I both know the difference between an overtreated room and a lively room but with delayed reflections. From our discussions it does appear that you prefer a more damped room than I do. I think I mentioned somewhere in my first post that target RT60 is a matter of application and also taste. I tend to prefer about 450-500ms but with reflections delayed. Others may prefer less. 

 

 

 

All great reading on here.

I’d like to add some weight to the importance of reflection when it comes to sound stage. This is my living room, see the blind on the left, when it’s shut like that and you’re listening with your eyes closed a centrally recorded singer is often situated just right of the TV. Open the blind and the singer moves across into the tv area by about half an metre (and the voice appears to clear up a bit). 

Throw a shaggy blanket over the TV and the voice appears to clear up even more, but that may be a pseudo placebo because I was told it would. 

12 hours ago, colinm1 said:

One thing that may work is to have the walls not square with each other ,

I work with the chaos theory , stuff everywhere ,within reason ,so 

sounds reflect on surfaces ,of uneven dimensions ,

I do have a kind of absorbing and reflecting areas , 

there was a Hi fi  shop that had two rooms virtually identical in size 

but the rooms sounded quite different , never worked out why ,

So only  so much can be done pre build ,

the fit out will be the major issue to work with 

 

I’ve thought about this a lot, having non parallel walls is occasionally mentioned by the experts as a positive move. My fear however is that I can’t create a trapagon, they’re too extreme in space wastage and I don’t have that luxury anyway.
So it would be a mild narrowing of the side walls which is experimental and therefore could be an expensive failure. 
Has anyone done this?