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Just how is a speaker too big for a room?

I've always heard and read that it is important to match speaker size to room: not too big, not too small. And am interested to have the question posed as to why. I don't have the answer, but that isn't going to stop me from posting:

It's important to remember rooms exist in 3 dimentions (at least all the ones I've been in) and that what I think we are talking about here is room volume. I could tell you my room is about 14x17, but that's not the most useful figure. It's most helpful to know that it is about 1700 cubic feet.

All this to say, let's not forget about ceiling hight. Speakers are not going to perform as well from the same listening position if the room's ceiling is only 5 1/2 feet.

I'm sorry I don't have enough knowledge about acoustics to be clearer, but feel like this 3rd dimension is worth addressing.
 
I think the whole shebang is mostly about inherent room modes based on the L, W, and H dimension, plus acoustical properties contingent on room furnishings and treatments.

Bass issues primarily the room modes, IMO, higher frequencies more a combination of both room modes and furnishings/treatments. The speaker's dispersion as some have measured, may also be a factor.

While there isn't really any formula that guarantees good sound, there are calculators that will predict the room modes and give insight into speaker positioning and seating positions for very good starting points.
 
There are certain speakers that don't work well in small rooms because of placement issues. It's not so much about the physical size of the speakers in many cases, but the type and requirements of placement. Dipoles/Bipoles require a fair amount of space behind them, as do ported enclosures with rear firing ports. Take a line array for instance, you need to sit a fair distance (5 to 10x the length of the array) to avoid lobing effects. Line sources are similar in that they play the same frequencies over a large area, meaning your ears will be receiving the same sound from the same source at different times. If you back away far enough, you will reach a point where the differences are minimized to a point of being nearly inconsequential. A small room would not allow you to back up far enough to get out of the noticeable range.

Dipoles don't like small rooms only because they require some space between them and the back boundaries. You can work with them closer using diffusers and absorbers, but it's a bit of a compromise. This goes for all dipoles, planar magnetic, ribbons, electrostatics, or conventional drivers.

I'd say the biggest issue you are likely to run into is that larger speakers sometimes need more space to get to a point where the dispersion patterns match up well. If you get up nearfield to a tiny 2 way monitor, the tweeter/mid tend to still blend well together because of their proximity. Do that within a foot of two of a big speaker with a 15" woofer and you'll hear distinctly seperate sources of sound.

So, in affect, there are reasons why particular types of large speakers may be too big for a room. But more often than not, it's just a stereotype with no evidence to back up what's being said. Especially when it comes to bass response. Bass response in any reasonable size room that 99% of AKers will be dealing with will be dominated by the room. Moving around a room with a pair of mains that go down to 20hz could see 25-30dB nulls just by moving a few feet. So, if you have a pair of speakers that have to be in position A and B for best midrange performance and those positions happen to place a 30dB null at from 40-80hz at the listening position, that extension is pretty well useless to you, regardless of the speakers ability to produce it.

Small room modal behavior is precisely the reason why most of the acoustical experts agree on one thing, using multiple subwoofers allows you to optimize your bass performance. People have different ideas on placement of said multiple subwoofers, but there is no debate that multiple is better than singles or no subwoofer at all. It's part of the fundamental misunderstanding of room acoustics that is so prevelant.
 
As long as you leave room behind a dipole - electrostate and a foot or so from the sides to the walls.They don't create alot of relected noise. Put them up close to the rear wall and things get muddy sounding fast.
 
Well, my issue was that dipoles need a good bit of room behind them. if you are in a 10x12 room with electrostats sitting 4' from the wall, you aren't going to have much space to get into a prime position. At that point, the issue of different path lengths could become noticeable to people with especially sensitive hearing.
 
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