Quad 989 vs Martin Logan CLS IIz?

Larryh - I used to own Quad 63's, then 57's, and listened extensively to many Martin Logans (of which the CLS was my favorite). I ended up with Sound Lab electrostats - and I loved them so much I became a dealer. Check out Sound Labs at www.soundlab-speakers.com; my site is www.audiokinesis.com. I liked the 57's better than the 63's, and the 63's better than the Martins, and the Sound Labs best - though they are a bit more expensive. The Quads are a fairly easy speaker to drive; the CLS's are difficult and won't play much louder than 93 dB no matter how much power you put into them; the Sound Labs are a difficult load but will play loud given sufficient power.

Hello Dannylw,

My source is a phone call to the Martin Logan factory. I had a customer inquiring if he could get 100+ dB peaks with the InnerSound amp driving his CLS's, so I called the factory. They told me the CLS's wouldn't do much over 93 dB no matter how much power you put into them. I assume that's for a single speaker.

I did not attempt to verify the figure for myself.

Based on your experiences and measurements, I now have to wonder if what the Martin people told me is accurate. I suppose I should have given the source of my information in my post, but it never occurred to me that it might be inaccurate.

Thanks for posting your findings!

Dannylw - you made a very astute observation - "that unlike a lot of speakers I've heard the volume does not drop appreciably with distance [with the CLS's]."

The reason for this phenomenon is, the CLS's approximate a line source, and sound pressure falls off differently with distance from a line source than from a point source.

Radiation falls off with the square of distance from a point source, but linearly with distance from a line source. Let me put this into numbers - suppose in an anechoic environment a point source speaker is doing 80 dB at one meter. At ten meters, this speaker will be doing 60 dB. Okay, now let's say a line source speaker is doing 80 dB at one meter. Back off to ten meters, and the line source speaker is doing 70 dB. Note this leaves out the reverberant field's contribution, but the trends are still there in the real world.

Actual measurements in my living room, using the pink noise track on a Stereophile test disc, Sound Lab line-source approximating speakers, and homebrew point source approximating speakers:

With a single line source speaker doing 80 dB at one meter, I measure 76 dB at 8 meters (about two feet off the rear wall). With a single point source speaker doing 80 dB at one meter, I get 69 dB at 8 meters. So in an real living room, the sound pressure falls off much more slowly with the distance from line source speakers (down 4 dB versus 11 dB at 8 meters).

And by the way Danny, you did not come across as harsh at all - very gentlemanly in fact. I appreciate the correction!

Best wishes.

Duke