What would be the perfect size and shape of a new HT room?

[Sonnie]

I may soon be building a new HT room... can't explain right now and it may not come to life, but I'd still be curious as to how would you figure, calculate the perfect size and shape room... or something close.

I don't want it too big but maybe 24' to 26' deep so that I could have 2 rows of seating with reasonable space behind the last row.

Would you make the front width narrower than the back... say 14' wide in front and 16' wide in back.... how wide and where and how high?

[Tommy]

Sonnie, your re-doing your room? I cant believe it, did you move or something?

Specially after all the work you did yourself on the last one and use itself, you autta know best what would be the ideal room for yourself.

But since your asking i'd say what room do you have to work with?

You want two rows of seating, isn't that what you have now with a room, it think it was 18' or something close?

Was that not enough room for you currently or do you just want to push things further back from the screen or do you actually need almost 10' of space behind your last row.

And me personally, I'd never angle the walls like that. Military in me but everything would have to be uniform. As long as it not boxed you should be good for sound. If you need more angles I would build the walls straight and then build extensions/dividers/etc to break it up.

If you defintely want and are staying with 2 rows, what size screen do you want to use. Figuring the screen size should judge your distance to your first row, adding your spacing for your second row and riser, and the clearance behind the row.

[Tommy]

Since your re-doing your room, can I have your old one?

[Sonnie]

HAHA... this is all speculation right now.

If I redo it, it will be in another area (add on) of the house or another house all together and there will be no space limitations.

I know there is some formula or some way of figuring the appropriate size so that that standing waves, etc., are minimized.

I'll probably stick with pretty close to the same screen size... maybe go from 97" to 106".

Two rows of seating, but I'd kinda like to have it wider so I could get 4 seats on the back row... only 3 in front so that the center seat is still dead center.

[JCD]

I wonder if room design could mimic speaker design. If so, I'd say a trapezoidal design would work best, probably the greater the angle, the better.

Unless you can make it circular (globes are supposed to be the best for speakers).

JCD

[hardman]

Do you have a copy of Everest’s book “The Master Handbook of Acoustics”? The topic of room shape and the effects it has on room modes is covered in detail. Glancing quickly at pages 229 – 234 (revision three), suggest the following room ratios for a rectangular room:

Height Width Length
1 1.28 1.54
1 1.26 1.59
1 1.6 2.33
1 1.4 1.9

Of the above ratios, it appears to me that 1 X 1.28 X 1.54 has the best LF room response, but the others should fair well too.

[Sonnie]

Uggghhh..... that would be extremely tall for the width I'd want then.

But 1 X 1.6 X 2.33 would be pretty good.

10H X 16W X 23.3D

That's probably the worst of the bunch huh? lol


Btw... welcome to the Shack!

[reed.hannebaum]

This doesn't directly answer your question but I have used the Computer Aided Room Acoustic program (CARA) from a German company called ELAC Technische Software GmbH, to analyze my listening room. This program is in 2 parts. First you use the CAD program to model your room including all the dimensions, doorways, windows, wall floor and ceiling treatment, size and shape of furniture, seating positions, plus the type and location of your speakers.

The second program analyzes the acoustics of your room and moves your speakers around (within limits you set up in the first program) to optimize the sound at the listening positions. Depending on the speed of your computer this can take a long time.

You have to be prepared to spend time learning how to use the CAD program and entering all the information, but for me it was worth it. My room is less than ideal and with a large opening into an adjoining room it certainly is not symmetrical. CARA located my speakers in a slightly un-symmetrical fashion and located the ideal listening position to make up for this problem; something I wouldn't have been able to figure out on my own.

[hardman]

Actually, the ratio you pick isn’t that bad. Regardless of what ratio you pick, most likely the space will still be too small to achieve proper axial-mode spacing. The goal is to design for as uniform mode spacing as possible (modes not spaced too far apart or too close together) and to try and avoid mode coincidences (mode resonances piled up at the same frequency). Now with that said, ratio 1 X 1.6 X 2.33 with a height of 10’ has the following problem areas:

Two modes resonances occur very close together at about 65 Hz, then again at about 140 Hz, and last somewhere around 240 Hz. There are two mode coincidence (two mode resonances pile up); one at about 165 Hz and another at about 280 Hz (but this is pretty high and most likely could be addressed fairly easy).

Hope this help… For what it’s worth, the ratio you picked is most likely the ratio I will shoot for some day when I am able to build a dedicated theater space.

[Sonnie]

That software sounds interesting Reed.


Hardman... I'm not quite savvy enough to follow you. When you elude to two modes resonances at 65hz.... and so forth... what exactly is happening there? Are you getting more boost there or standing waves... what's going on, or how is it effecting the sound... in elementary terms for a hillbilly to understand.

[JCD]

Bump.. or nudge as the case may be..

I remembered this thread and ran across the following article online that references the same dimensions above. It may also have some other pointers that may help in the design.

JCD

[Ayreonaut]

The B&W website says that The IEC recommends some specific room dimensions for domestic listening based on three different heights:

8' high x 12.8' wide x 19.2' long
9' high x 13.5' wide x 21.5' long
10' high x 16.0' wide x 24.0' long

[hardman]

Sonny,

Sorry for the delayed response. I have been so busy lately. The simple answer to your question is yes, you are getting a boost where modes combine.

A simple test that one can do to understand what I am talking about is to play test tones lower than say 200 Hz and walk around your room while the tone is playing. You will notice that in some spots it is louder and at others it gets softer. Room size and the ratios will help lend to a lessening of this effect, but will never replace the need to adequately trap the lower frequencies within your space. I have been able to measure the effects of placing bass trap in the corners of my room and the effect it had on the room as a whole. As a result the low frequency tone was more even throughout the room.

To be honest, I too am a “hillbilly” when it comes to acoustics. All I have learned has been the result of my reading Alton Everest’s book http://www.amazon.com/gp/product/B00...lance&n=551440 . The link is a downloadable version for $22.

If you would like, I can try to elaborate more on these topics but it is all covered in the book.

Chris

[Sonnie]

Thanks Chris... I think I understand what you are saying now.... hillbilly to hillbilly.

I have this problem at 30hz against my back wall and it's really bad. I suppose the modes are combining there. I can come out about 4-5' from the wall and it's no longer a problem.... it will level off properly. But it's a terrible boost when sitting down and your ears are within 2' of the wall. I guess I need about another 4 feet in my room length.

I looked into bass trapping this but I think it would be nearly impossible unless I could somehow build something strategic and huge... and then it would a lot of trial and error. I haven't seen too many bass traps that work below about 80hz.

[mobilelawyer]

Sonnie wrote:

I may soon be building a new HT room... can't explain right now and it may not come to life, but I'd still be curious as to how would you figure, calculate the perfect size and shape room... or something close.

A new home theater room already. I don't even have my first one yet! I am jealous.

[Sonnie]

Well let's just say we'll literally have to strike oil on our property for it to happen.

[RodN]

You could always go for fibonacci's golden mean which is vary Davinci Code but apparently a very good listening room ratio.

Which just involves multiplying each dimension by 1.618.
Hx1.618 = W
Wx1.618 = L

This site at rives is great for trialling dimensions and speakers and room treatments: http://www.rivesaudio.com/CARAquick/CARAframe.html

[Sonnie]

Hey Rod and welcome to the Shack!

Now that's one cool program... other than having to convert feet to meters... I like it and that might just come in handy for some folks. Thanks!

[RodN]

I guess I didn't read the above posts that well as 1x1.6x2.33 is extremely close to a golden ratio.