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Looking for recommendation on ceiling height

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Posted on October 12, 2009 at 10:12:55
jim94025
Audiophile

Posts: 71
Location: SF Bay Area
Joined: February 7, 2001
 I'm getting bids on raising the ceiling/roof height in my HT/music room.Currently it has a flat 8 ft ceiling and the room is 17ft wide with the length between 22 and 25 ft(uneven- about half of each).It will probably need to be a cathedral ceiling, but that will depend upon cost.
What numbers should I use for ratio's to get the best reduction in nodes?
Thanks, Jim

RE: Looking for recommendation on ceiling height, posted on October 14, 2009 at 10:15:02
Ethan Winer
Manufacturer

Posts: 1554
Location: New Milford, CT USA
Joined: December 3, 2003
 Room modes and ratios do matter in domestic size rooms, but I rarely suggest paying big bucks for serious construction just to improve a room's ratio. You can achieve similar results with lots of bass traps. Even rooms having "good" ratios need lots of bass traps.

If the look of many panels is not acceptable, get a bunch of bass traps anyway then cover them with stretch-fabric walls etc. That's still a lot cheaper than literally raising the roof. Also, there are commercial bass traps that do not look like panels, and blend into a room, so that's another option.

--Ethan

RE: Looking for recommendation on ceiling height, posted on October 14, 2009 at 13:01:58
jim94025
Audiophile

Posts: 71
Location: SF Bay Area
Joined: February 7, 2001
 I would agree, just to change ratios, however my purpose was to gain more space above the speakers as well, for better image height and adding to room volume. As I have stated in earlier posts, my prior room had a 13' cathedral ceiling which provided much better image height and a very clear, transparent soundstage. Jim

RE: Looking for recommendation on ceiling height, posted on October 15, 2009 at 12:30:57
Ethan Winer
Manufacturer

Posts: 1554
Location: New Milford, CT USA
Joined: December 3, 2003
 I can't say for sure, but I imagine that differences in imaging in the other room were not only due to the height. I'm not trying to talk you about of raising the ceiling! I like high ceilings too.

--Ethan

RE: Looking for recommendation on ceiling height, posted on October 18, 2009 at 17:11:25
jim94025
Audiophile

Posts: 71
Location: SF Bay Area
Joined: February 7, 2001
 It seems I will have two choices of ceiling: a classic cathedral ceiling, with the front wall going straight up to the point were it meets the highest part of the ceiling,(around 11 ft.,going from front to back), or.... a cathedral ceiling were the front wall is also vaulted twards the middle of the room, starting at 8 ft and meets the highist point (11 ft.) at around 6 ft into the room.
Any comments which would serve me best acoustically? It seems that the simple classic cathedral ceiling would allow the highest image height and largest room volume, but maybe it dosn't make that much of a difference? Or the vaulted front wall is especially benificial?
RE: Looking for recommendation on ceiling height, posted on October 19, 2009 at 10:35:13
Ethan Winer
Manufacturer

Posts: 1554
Location: New Milford, CT USA
Joined: December 3, 2003
 A ceiling that goes higher toward the rear and doesn't come back down is best. The ceiling in my living room home theater peaks at 11 feet in the middle and goes down to 8 feet in the front and rear. The sound and acoustics are fine! But I have absorbers under the center peak which avoids focusing any reflections to a point under the peak. Photo below.

--Ethan
The myth of "optimum room dimension ratios", posted on October 12, 2009 at 10:53:10
KlausR.
Audiophile

Posts: 1867
Joined: November 17, 2004
 Optimum ratios were initially developed for reverberation rooms, where measurements of sound fields of machines etc. were to be made. Machines produce noise, i.e. the whole audible frequency spectrum, or major arts thereof, simultaneously and all the time. For measuring the sound field microphones are placed all around the machine. Since the whole spectrum is constantly emitted, all of the possible room modes are excited all the time. In order to obtain useful readings from all microphones the mode frequencies had to be spaced evenly on the frequency scale. Somehow this approach had found its way into home audio.

However, what are you doing by selecting "optimum room dimension ratios" ?

You are spacing all of the possible room modes according to some particular criterion on the frequeny scale, the emphasis being on ALL.
In order to take full advantage of the optimization you'd have to excite all of the room modes and what is more, you'd also have to perceive all of those excited modes. If you excite only some of the modes and you then perceive only some of these excited modes, why use a criterion that optimizes ALL modes?

The only place where you are able to excite AND perceive all modes are room corners, which means that loudspeakers and listening position have to be right there, in a corner. You'd further have to take care that you excite all modes at any given moment, which is simply not possible when playing normal music.

Since all of those optimization methods are, inherently, designed to obtain optimum conditions for room corners only, my advice is to just forget about this optimum room dimension issue. If possible, avoid ratios where one dimension is a multiple of another, but even in this case, the result is not necessarily worse:

Fazenda et al., “Perception of modal distribution metrics in critical listening spaces - Dependence on room aspect ratios”, J. of Audio Engineering Society 2005, p.1128

In the case of a cathedral ceiling you are leaving the area of rectangular rooms anyway since there won't be any axial and tangential vertical modes, and the pressure lines of the horizontal modes are probably no longer parallel to the room boundaries but curved instead.

Klaus

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