Do you turn your drive units through 180 degrees to counteract the effects of gravity on the suspension over time? If so, how often? I did it on some old KEF bass drivers when the voice coil started rubbing. It did the trick, for a while 
. I wonder whether this is good idea to do with all drivers periodically, intuitively it seems so.
. I wonder whether this is good idea to do with all drivers periodically, intuitively it seems so.
The speakers in a Leslie are mounted horizontally. I don't think this represents Scottjoplin's point
.Btw, some older models feature a Rotosonic TM drum which is a vertically mounted speaker, usually 6"x9", that rotates around a vertical axis.
Best regards!
If the manufacturer thought it necessary I would imagine they would have a mention about it in the speaker info that came with the speaker. Large systems....never seen or heard a mention on it. I would think if you have a problem with coil drag its probably time to do something with the driver like a recone or diaphram replacement.
Good idea, I hadn't thought of less than 180 degrees, but that makes sense, evens out the wear more.
Sorry, can't follow the logic here
I can think of a couple of reasons off the top of my head why they wouldn't mention it 
It's a great question...one I've thought about a lot since building a PPSL sub that puts the drivers in horiz position, because I was warned about cone sag doing so.
I contacted the driver manufacturer (BMS) and was told, "yes be concerned with sag...the voice coil weighs over half a pound."
After thinking about sag situations and doing bit of research, I've come to the conclusion that any larger drivers with heavy-ish coils, or lighter-ish cone/suspension structures, probably need periodic rotation, especially when they leave vertical alignment. But that many (most) home audio drivers probably don't.
On the PPSL subs, I run a small DC voltage, 0.7v, on the drivers when subs aren't in use.
This lifts the coil the right amount to offset the gravitational sag.
I contacted the driver manufacturer (BMS) and was told, "yes be concerned with sag...the voice coil weighs over half a pound."
After thinking about sag situations and doing bit of research, I've come to the conclusion that any larger drivers with heavy-ish coils, or lighter-ish cone/suspension structures, probably need periodic rotation, especially when they leave vertical alignment. But that many (most) home audio drivers probably don't.
On the PPSL subs, I run a small DC voltage, 0.7v, on the drivers when subs aren't in use.
This lifts the coil the right amount to offset the gravitational sag.
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