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What causes "cupped hands"?

I've been dealing with this puzzling phenomenon for several months. I can't seem to rid my system of the "cupped hands" or megaphone effect. Acoustic treatments seem to help but haven't diminished it to an acceptable point. I've been told that cables can cause it but haven't been able to confirm this. The system consists of:

Mark Levinson 390S CD Player
Antique Sound Lab KMP-60 Fox DT Amps
Aerial Acoustics 7B Speakers
1.5 Meter ZCable LIVE v4 Interconnects
4' ZCable PASSION v3 Speaker Cables

Any ideas?
skipperrik

Showing 2 responses by audioengr

audioengr
3,282 posts
 
May be non-linear phase response or cable reflections/electrical resonance. This can be caused by cables, particularly long ones. Lossy cables can cause general musical soup as well, particularly in the high-frequencies. This effect was obvious in my system when I immersed some IC's in LNO2 as an experiment. It damaged the surface finish of the wire, I believe. Sounded like the music was coming through a tunnel. The correct way to do this is to lower the temp and raise the temp slowly. It was just an experiment, but yielded useful information.

You can learn more about electrical resonance at he Audio FAQ page of:
http://www.empiricalaudio.com
including the results of the cryo immersion experiment.
audioengr
3,282 posts
 
Your placement sounds unusual. Usually in a rectangular room, the (box) speakers are about 2 feet from the back wall, with the listening position around mid-room, which would be around 10 feet away from the speakers. In order to get the optimum image from most speakers, an equilateral triangle is usually used. This would make the triangle 12 feet on each side. I would measure this. Then play with aiming the speakers in and out fo rhte best dispersion, sweetspot and image. Now the ceiling, being shorter at the front, will cause a horn-effect, which should not impact the image, but may cause some boominess in the bass.

The other thing to do is treat the sidewalls and backwall. Sit in the listening position and have another person put a hand-mirror against the side wall and move it until you can see the tweeter from the listening position. This is where you will need absorbing materials on the side walls. I use 4" thick Sonex myself. It can be wrapped in cloth to address the spouse factor. Wall hangings can work reasonably well too. As for the back wall, this is often better treated with a dispersive reflector. If you have vertical blinds, these can be half-opened. Heavy curtains work well too. There are several examples of different room treatments on the Audio FAQ of my website:
http://www.empiricalaudio.com
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