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Author Topic: Good room ratio for live room?  (Read 6431 times)

Chris Griffith

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Good room ratio for live room?
« on: March 01, 2008, 10:47:12 pm »

I have a long space I want to put a new live room in.  

The space is only 15 ft wide and 12 feet high but around 80 ft long.  

What would a good ratio be for a room somewhere between 20 to 30 ft long?  I can go longer if its going to make a noticeable difference but would prefer something in that size range.  

Also should I build the room with parallel walls and add some smaller saw tooth shaped walls (like in Mr Manzella's design of John Kilgore's studio) to break up parallel surfaces or build the entire room with angled walls?  

Soundwise I just want something that sounds open and natural.  I'm not looking for much of a sonic signature, but don't want it sounding dead or muffled.  

Thanks so much in advance!

Chris


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Ethan Winer

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Re: Good room ratio for live room?
« Reply #1 on: March 02, 2008, 12:26:33 pm »

19 feet long is pretty good, but you could certainly go longer. In many cases, larger trumps having a good ratio. IMO. This page explains ratios in more detail, and also has a Windows program you can download for free:

http://www.realtraps.com/modecalc.htm

--Ethan

Chris Griffith

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Re: Good room ratio for live room?
« Reply #2 on: March 02, 2008, 02:01:40 pm »

Does larger always sound better?  Size wise I'd prefer something around 25x15x12 but want to make sure its going to sound the best possible.

Is there any similar software I can download for a mac?
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avare

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Re: Good room ratio for live room?
« Reply #3 on: March 02, 2008, 04:54:16 pm »

Chris Griffith wrote on Sun, 02 March 2008 14:01

Does larger always sound better?  Size wise I'd prefer something around 25x15x12 but want to make sure its going to sound the best possible.

Is there any similar software I can download for a mac?


You can always use Bob Gold's
http://www.bobgolds.com/Mode/RoomModes.htm room mode calculator.  No slight intended, it goes into several steps of depth after Ethan's calculator.


Andre
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Chris Griffith

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Re: Good room ratio for live room?
« Reply #4 on: March 02, 2008, 05:47:08 pm »

From playing around with the numbers it looks like 25x15x10 would be the best looking ratio for what I'd like.  

Is it better to bring the ceiling height down lower for a better ratio?  Seems like loosing that 2 feet would bring the cubic volume of the room down a lot.  

A ten foot ceiling would be much easier and cheaper to build though.  

If I build the room without parallel walls are the ratios as important?  

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gullfo

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Re: Good room ratio for live room?
« Reply #5 on: March 03, 2008, 11:20:17 am »

i would try to keep the 12ft ceiling if possible and just use a scattering of broadband absorption and diffusers to create a nice space - and perhaps some reversible treatments to permit changes in the overall room characteristics.

altered to 11' ceiling (updated - i had goofed...)
   ratio   size   m   sqrt(2)   even   ok   h   1.00   11.00   3.35   0.61   FALSE   TRUE   h-ww   1.32   14.50   4.42   0.07   FALSE   TRUE   l-hl   2.27   25.00   7.62   0.22   FALSE   TRUE   l-w (h)   bolt   ebu   iec   >5%   walker         TRUE   TRUE   TRUE   TRUE   TRUE                              ax 1st   ~note   ax 2nd   ~note   ax 3rd   ~note   ax 4thh   51.18   G1   102.36   G2   153.55   D3   204.73w   38.83   D1   77.66   D2   116.48   A2   155.31l   22.52   F0   45.04   F1   67.56   C2   90.08                        vol   surf   edge   area   T(ms)   r(ms)   Dcft   3988   1594   202   363   8.89   515.52   7.01m   112.91   148.09   61.57   33.68                                 rt60   eyring   millington   Fc   Fs   Fc2   davis   1.61   1.40   1.24   168.79   238.89   251.08   307.09            ~note   ~note   ~note   ~note            E3   A#3/Bb3   B3   D4                        ratios   diatonic   phidev   modes   df      h-w   1.32   
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Glenn Stanton

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Ethan Winer

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Re: Good room ratio for live room?
« Reply #6 on: March 03, 2008, 02:06:50 pm »

avare wrote on Sun, 02 March 2008 16:54

No slight intended, it goes into several steps of depth after Ethan's calculator.

No problem, and no slight taken. This brings up an important point. Every time I see Bob Golds post a list of 90-odd modes for someone's room I always expect the recipient ask "What the hell am I supposed to do with all those numbers?" But they never do. I guess they're too intimidated.

I've never been convinced that non-axial modes account for much, and when you include those you end up with so many modes only a few Hz apart that it's impossible to see the forest for the trees. However, some day I may add non-axials to my ModeCalc program, but shown as lighter colored lines with lower heights to reflect their lesser impact.

--Ethan

avare

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Re: Good room ratio for live room?
« Reply #7 on: March 03, 2008, 03:40:28 pm »

My bad.  I didn't do the volume calculations from your dimensions.  It took Glenn's post to open my eyes that your can almost 100 m^3.  Trevor Cox has done leading research on modes and has an Excel that shows the best ratios for a room that big.  Just pick and choose from the list.

The link to the file is about 2/3 down on:
http://www.acoustics.salford.ac.uk/acoustics_info/room_sizin g/?content=best

Enjoy!
Andre
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Chris Griffith

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Re: Good room ratio for live room?
« Reply #8 on: March 03, 2008, 07:15:37 pm »

Ok so I think I'm going to go for 25X14.5x11.  Seems perfect and the slightly lower ceiling will be a lot easier to fit in the room.


Should I just build a rectangle or will a couple angled walls that average out to the above ratio end up sounding better?  

I always seem to like the sound of irregular shaped rooms, but dont want to end up making bigger problems for myself then a properly treated rectangular room.  

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jimmyjazz

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Re: Good room ratio for live room?
« Reply #9 on: March 03, 2008, 11:17:26 pm »

Most acousticians would agree that normal modes should be weighted more heavily than tangential & oblique modes.  I've seen different suggestions on HOW to weight them, but in the end, it's a bit of a crap shoot.

I'll say this:  relying exclusively on normal mode distribution is oversimplifying things, but so is weighting everything equally.  There are some pretty interesting "goodness" functions out there in the literature that are worth exploring.
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avare

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Re: Good room ratio for live room?
« Reply #10 on: March 04, 2008, 01:39:21 am »

Quote:

Should I just build a rectangle or will a couple angled walls that average out to the above ratio end up sounding better?

I always seem to like the sound of irregular shaped rooms, but dont want to end up making bigger problems for myself then a properly treated rectangular room.


The answer is in your second sentence. If you like hte sound, use angled walls, and the average dimension for mode calculations.

Andre

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Chris Griffith

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Re: Good room ratio for live room?
« Reply #11 on: March 04, 2008, 10:56:00 am »

I would just hate to build random angles and end up with some weird sounding reflections.  

Is there anywhere I can read about the principles behind angling walls?  Is there any science to it?

Sorry to be asking so many questions, I just want to make sure I get everything right before construction starts.  
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avare

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Re: Good room ratio for live room?
« Reply #12 on: March 04, 2008, 02:36:26 pm »

Chris Griffith wrote on Tue, 04 March 2008 10:56

I would just hate to build random angles and end up with some weird sounding reflections.  

Is there anywhere I can read about the principles behind angling walls?  Is there any science to it?

Sorry to be asking so many questions, I just want to make sure I get everything right before construction starts.  


It is difficult to answer generalities.  Yes there is science behind splayed (another word for angled) walls.  Remember that a ceiling is just a wall turned on it's side.  It comes down specifics of any room. This thread provides an example of how frustrating it is to give a specific answer.  In case you can not figure it out, the answer was "it depends."

Another thread that may help you is this one.

There is no simple answer to your first question.  The requirements have gone beyond science (to know) to engineering (to use).

Keep the questions coming!

Andre
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Ethan Winer

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Re: Good room ratio for live room?
« Reply #13 on: March 04, 2008, 04:51:55 pm »

Chris Griffith wrote on Tue, 04 March 2008 10:56

Is there anywhere I can read about the principles behind angling walls? Is there any science to it?


There are two reasons to angle walls, possibly three:

1) Angles of 6 percent on both opposing walls is enough to avoid flutter echo between those surfaces.

2) Angles of 30 to 35 percent are needed to direct first reflections around the listening position to the rear of the room, to avoid needing absorption at those places.

2-1/2) Angles might make room modes slightly less resonant, though I never tested this and can't say for sure.

--Ethan

Chris Griffith

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Re: Good room ratio for live room?
« Reply #14 on: March 08, 2008, 04:51:23 pm »

I still havent decided as to how I want to build the room.  I'm pretty sure I'm going to build it 11x14.5x25 in size.  

Part of me is thinking I'll just build it with parallel walls but build some 4 ft wide splayed walls inside the room faced with thin plywood and stuffed with fiberglass that can serve as bass traps/reflectors.   I know I want part of the room very dry and other part very live.  That way I can keep drums on the dead side and get a little natural predelay before the sound hits the more lively side with the angled walls.  Does this sound like a decent idea?

Ultimately I want a bright tight sounding room but still with a little bit of size.    
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