optimum room size

[Andrew Pratt]

I have a 11.5 foot wide, 34 foot long and 7 feet tall basement room that am going to turn into a HT room in our new house. I am going to build a wall seperating this long narrow room into two parts...one being the media room and the other a small office. What I'm wondering is that according to how I have things set up now I need around 23-24 feet for the lenght of the HT room leaving 10 feet for the office...my question is is there a better distance to choose from an audio perspective? I know there's golden rules for speaker box's does that apply for rooms as well?

[David Meek]

Andrew,

Yes there are several "golden rules" for room ratios. The only one I remember off-hand is: 1.0 (width) x .61 (height) x 1.61 (depth). Using 11.5' as your width, the ceiling should be 7.015' (dead on!) and the depth should be 18.515'. Having the first two dimensions match up is a nice way to start. If you limit yourself to an ~19' depth, you'll have plenty of room for a dedicated HT room, media closet AND an office. That's too cool!

BTW, please don't ask me to document sources, at least for today, as a lot of my audio/video papers are boxed up somewhere after our move. Again, there are several suggested and I'll try to dig out my info this weekend. Hope this helps.




David - HTGuide flunky
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[Sonnie Parker]

That sounds kinda strange but I'm not doubting it. Think about a theater. Width/depth probably are on the mark for the most part. At the few theaters I've been to anyway. But the height is always tremendous in theaters. 12' to 20' or so. I suppose though if you had that many people in a 7' high room it would be dangerous. Not much circulation.






SONNIE

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[JonMarsh]

David's on the money, there.

Good sources regarding architectural and acoustics design include the back articles in SGHT for the HT home architect (they also have a nice little XL sheet for predicting room modes and response at seating positions), RPG Acoustics, (they have a very good $99 software package that can simulate boundary and modal response, with an optimizer for finding the best speaker and listner positions within constraints you provide), and our old body George Cardas, which if you really want to optimize the speaker setup for 2 ch as well as surround, you should listen to. He's also major, major into the golden mean thing, including his cable designs. Highly recommended.

http://www.guidetohometheater.com/

http://www.guidetohometheater.com/shownews.cgi?388

http://www.rpginc.com/

http://www.cardas.com/main.html

Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[AndrewM]

How about going high-tech on the problem, pick up some of the room acoustic software around like Cara or RPG (something that will let you sim the room). And then you can play around with the room size, placement of speakers and equipment, see the changes when you add some acoustic treatments, etc.

I've been playing around with Cara for the last couple of days, and I've found some eye opening stuff...it may end up being the best thing I've ever bought for my system...regardless of price.

Andrew

[Andrew Pratt]

thesim software sounds interesting. The 19' recomended depth is going to put my rears very close to the rear wall which when using maggies isn't ideal...how does one ballence giving the speakers room to breath vs the golden ratio's? As I'm lookin at it now I will need some 3 feet from the rear wall to the front of the TV to allow for the TV and little sound insulation behind it (all long the back wall). Adding ten feet to this I get to the first row of seats ...add another few feet and I'm at the back row so I should now only have four feet to the back wall if I have a depth of 19 feet. Thats why I was thinking of going with more like 22 or 23 feet to give me a little more room. thoughts?

As for the gear racks etc those will be built into the right side wall so they won't take up floor space and the sub will be an IB sub in that wall as well so it won't take up room there either.

[David Meek]

Andrew (Pratt),

Yes, like AndrewM suggested, pick up the CARA software package and model it out. I've done this on my room and have wound up turning the whole room layout 90 degrees based on the models. FWIW, the sound improvement is excellent! For a project of this magnitude, the $49 US for the application is money VERY well spent.

- David -




David - HTGuide flunky
Our "Theater"
Our DVDs on DVD Tracker

[Andrew Pratt]

how well does CARA model for bipoler speakers?

[Andrew Pratt]

Ok going through Cardas's golden forumla's I get a room of 19 feet deep by 11.5 feet wide by 7 feet tall (assuming I can change only the depth)

Using his side wall distance I get a position that places the middle of my speakers 3 feet out from the side walls. The mains should be 5 feet out from the front wall and the rears should be 4 feet out from the rear wall. They also suggest that the mains and the sweet spot form an equalateral triangle which would mean that the sweet spot would be approx 5 feet back from the front speakers. Now when I plot all of that according to my quick and dirty diagram above that would leave me about 5 feet behind the first chairs before I hit the rear speakers. This would be fine if I didn't want to have seats behind the sweet spot but given the rooms only 11.5 feet wide I figure I can only get three chairs on the first row which isn't enough when guest are over. Also even if the TV is placed back a foot or so from the main speakers it will still only be around 7 feet from the sweet spot. Right now I sit 10 feet back from my 50" RPTV and it seems about right...7 feet might be a little close?

I tried plugging in some numbers into the excel spread sheet from stereophile and it didn't produce any major issues ...a few single peaks but no double or tripples and no nulls...even if I increased the room depth to 23 or so....

I guess if I needed to I could cut down the distance from the back wall to the rear speakers since the SMG's are going to produce a good image back there anyway which would leave me another foot or so for the second row of seats...
So where do I go from here?

[David Meek]

Andrew, my mains are direct radiators (Boston Acoustics VR-35's). So I haven't looked into that portion of CARA.

- David -

[JonMarsh]

With the Maggies, the apparent source and positioning is a little different problem than with a box speaker, since you don't get the same type of rear wall re-inforcement.

Re the Cardas layout recommendations, many people are reluctant to try this positioning at first, because of the impact on room space and listening area.

BUT, I can't recommend enough, at least *try* the optimum recommended layout. Listen to it, on a variety of music and theater material. Then, if at times you need to compromise for additional seating, make those changes- maybe on a temporary basis?

At least, if you have to compromise more "permanently", you'll have a clear idea of what you're giving up - and what the compromise means.

Regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Andrew Pratt]

Jon I intend to try the cardas layout my only concern at the moment is the lenght of the room being limited to 19 feet which might be a little tight...in your oppinion how critical is the 19 feet? ie is there a slight fudge factor or is it pretty tight to 19? Also you said maggies are a little different to set up. On the Cardas site they provide a different value to use for distance from the side walls which is how I came up with the 3 feet from centre.

[Andrew Pratt]

I came across this link which I thought was well written

Optimum Room's Size

PDF of Optimal Seating positions