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In Reply to: RE: Setting up Magnepans posted by ceulrich@fastmail.us on September 27, 2016 at 07:53:34

Hello All,

Thanks again Satie for you comment. A subwoofer is on my list to consider.

Continuing on from my last post:
Attached is a figure showing the early reflections for the left and right speakers individually and for left plus right. The table in that figure presents the actual difference in time between the direct sound and the reflected sound. The sound travel-times were determined using a laser tape measure. Just point the laser at the speaker and read the distance, or point the laser at a mirror showing the reflection of a given speaker and the laser dot also reflects and can be seen on that speaker, and again, just read the distance. Very cool. The difference between the two distances divided by the speed of sound yields the time difference.

The burst of reflections around 1.0-1.8 ms are mostly due to reflections from the back of the listening chair. The listening chair is a classic Eames chair, where the back is solid and comes up a few inches above the listener's ears. These reflections disappear when a person is seated in the chair. The reflections around 2.5 ms are due to the left speaker, and are probably reflections off of the wall on the right of the listening position (as was suggested by BigguinATL a few days ago). The reflection at about 4 ms is due to the right speaker, but I am not sure of the travel path. Similarly, I am not sure of the travel paths for reflections at 5 and 7.2 ms. These reflections are somewhere between -6 to -9 dB down in amplitude from the direct sound.

The reverberation time as measured by the Topt parameter of the REW software was 0.346 seconds for this room.

Based on the work of Floyd Toole we know that reflections in the 0 - 10 ms range that are between -2 to -15 dB down add a sense of spaciousness to the perceived sound. One of the reasons I continue to enjoy this rather unusual arrangement of speakers and listening position is the great sense of depth, height and width of the sound field, which is probably primarily due to these reflections.

One last evaluation I conducted was with Stereophile's Concert CD using the last track titled "Mapping the Soundstage." For this track, John Atkinson walks around a recording venue (a church) clapping his hands. In the associated booklet he describes in great detail what the listener should hear in relation to the movement of the image of the clapping. I was not sure if a planar speaker would be able to generate as detailed an image as a cone-type speaker, and thus how useful such an evaluation would be. But I was pleasantly surprised to find that I could very easily follow the image just as described.

In conclusion, I would advise anyone setting up planar speakers not to be too constrained by the conventional wisdom on speaker and listening positions. In my case I was constrained by the need to share a living room with a listening room, and ended up with a good if not great listening space. I still need to work on my left channel problems, mid-bass suck out and the 400 Hz hump.

I will sign off for now, but I will be pleased to read any additional comments anyone would like to offer.

Cheers,

Chuck

Planar Speaker Asylum

Planar Speaker Asylum

RE: Setting up Magnepans

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