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Critic's Corner

Here is what Geddes says:

196.3.50.254

In Reply to: RE: Sean Olive posted by KlausR. on January 31, 2008 at 08:08:27

"CD (constant directivity) is a well known design criteria for large venue systems, but it is almost nonexistent in home high-fidelity loudspeaker systems. There are two reasons for this; pistons and size. Piston sources can never be CD and CD simply cannot be done in a small area. It takes space and area to control sound radiation and there is simply no way around this fact. Hence, for sound systems in small rooms, bigger really is better. Somehow it just seems obvious that the larger speakers of the past sounded better than the multitude of mini-cubes and tower speakers of today. Small speakers do have their place, but not as sources for critical listening in a well designed room. Virturally all small speakers are omni-directional. It's easy and inexpensive, but completely wrong for a small room."

Your monitors would fall into this category I believe. So actually in a small room a large full range ribbon or electrostat (like a Soundlab) gives a more ideal radiation pattern (and CD over a very wide range) in a small room. Of course Geddes also says his horns are CD. He points out that omni-directional speakers (like nearly all smallish box speakers) have big problems in small rooms with early reflections and that damping them is not the solution. If you want to read his thoughts on this you can find the white paper on his website with the Summa loudspeaker. There is much more to speaker design, Klaus than on-axis FR.

Follow Ups:

RE: gives a more ideal radiation pattern - KlausR. 09:51:26 02/01/08 (0)
I think that to this day no one has actually determined what the ideal pattern is. The only statement in this context is from Toole says that FR on-axis should be flat (± 1.5 dB), FR off-axis smooth and well behaved. Geddes has his opinion Dave Moulton has the opposite opinion, there is not much research available, so it appears to be a matter of opinion at this stage.

> He [Geddes] points out that omni-directional speakers (like nearly all smallish box speakers) have big problems in small rooms with early reflections and that damping them is not the solution. <

In 2006 Floyd Toole has published a very interesting AES paper entitled "Loudspeakers and Rooms for Sound Reproduction—A Scientific Review" (where he reviews 75 technical/scientific papers). Also the issue of early reflections is addressed. Toole comes to the conclusion that early reflections are no problems.

I've read most of the papers he cites and did some digging in relevant technical journals and yes, there is no evidence that early reflections are a problem. So I wonder on what evidence Geddes bases his statement.

But that's an issue which is more at home in the Rives forum, where it actually is being discussed at the moment.

Klaus

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