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Why do planars have poor bass extension?

I've been wondering about this. Is it because the excursion is limited because of the tension of the diaphragm & low BL limits its excursion?

On a related note, what techniques do companies like Magnepan use to get more bass out of their low-frequency drivers? Do they put bigger magnets in the grid than would be feasible for the midrange? Heavier diaphragms?

Finally if anyone knows a good reference for learning about the TS parameters of planars and if/how such calculations differ from dynamic speakers, that would be awesome!

Thanks all!
sideshowgabe
jameswei
883 posts
 
I think you're right -- the diaphragm's tension limits its excursion so that it can't move enough air to generate adequate volume at lower frequencies.

Solutions seem to include bigger panels to move more air and augmenting lower frequency response with dynamic woofers. In the latter case, driver integration is a significant challenge, since the panels tend to be very fast while the dynamic woofers can be slow.
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mapman's avatar
mapman
22,311 posts
 
I've read accounts that make sense to me that often the support structure is the weak link in the bass of planars. The frames tend to not be very massive and there is little inertial foundation for the drivers to work against. Adding mass and/or rigidity to the frame helps. At least that's what I've read that seems to make sense.

Also, many do not realize that most planars like Magnepan forexample require lots of power (though not necessarily current) to be driven to the max. A 40-80 watt SS amp might sound OK, but does not hit the mark. 200W+ SS or a larger tube amp is usually what is needed to wake things up.
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