Aura Bass Shaker Modification
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Guy Kuo, of Ovation Software, decided to improve the
bass shaker performance by lowering their resonant frequency. The tip below applies
to the 20W, 25W, and 50W pro shakers:
"I have a pair of Aura Pro Bass Shakers attached to my couch (day bed actually).
The shaking they produce is always a hit with visitors and vital since my wife hates loud
noises and I love LF effects. I can't crank up my subwoofer, but the shakers keep us both
happy. Anyway, they normally have a peak effect in the low 60's, just a tad too high for
best effect. Some people use bass equalization to tame this peak, I decided to lower the
resonant frequency of the shakers themselves.
The Aura Pro Shakers are easily opened with a #20 torx driver. Once opened one sees a
three legged, plastic, spiral spider which supports the moving magnet/mass. The voice coil
is fixed and on the periphery. The choice was to either increase the mass or make the
spider more compliant. The legs of the spider are quite stiff, more than actually needed
to support the mass. Since there was little room to add more mass, I trimmed the spiders
thinner, narrower and slightly longer using a Dremel tool and cutter bit. Took off nearly
the thickness of the spiders and also cut into the periphery to slightly lengthen them.
Obviously this may shorten the shaker life if too much plastic were taken off, but they
are cheap enough to replace if one goofed. By the way, don't cut too far peripheral or you
might damage the voice coil! The spiders still firmly support the magnet. Checking with
the LFE low frequency sweep in AVIA the shakers now peak at just under 45 Hz instead of
about 60. They also now produce output down to high 20's instead of giving up in the 40's.
I needed to turn down my Shaker amplifier down slightly as they are now more efficient.
The effect is definitely deeper and fuller bodied. After going through the opening scene
in Lost in Space and the helicopter scene in Matrix, I am convinced my hour of work paid
off. Usual caveats apply. This definitely voids any warranty on the shakers, but they're
Just don't take off too much plastic. How much is too much has yet to be discovered. I
probably took off just over 1/2 of the spiders' plastic mostly in their thickness and was
careful to smoothly contour all my trimming. Maybe they'll break a bit sooner, but I
suspect they'll do fine. In the mean time, they ARE more fun.
A side effect of lowering the resonant peak to the 40's is that less high frequency
audio leaks through. The shakers get a low pass signal, but their former peak just over 60
Hz made them respond to things which shouldn't be felt. Now they intensify low bass
effects but have little "voice in your butt" effect.
Don't forget to double check your phasing when you wire them back together. They easily
cancel each other out.
I decided to further deepen the response of one of my Aura Pros by taking off even more
of the spider and adding a bit of mass. After extra trimming of the spider and careful
epoxying of heavy gauge solder to the magnet, the resonant frequency dropped to about 33
Hz. With the two shakers are differing resonances, shaking effect begins to intensify at
55 Hz and stays strong down to 28 Hz. There is now palpable effect down to 22 Hz.
Trimming the spider even more does decrease the maximum intensity of shaking which
avoids chatter since the mass can move further. It's still maxes out at much more effect
than I'd ever want, but this is an issue which should be considered if one trims the
spiders down to 1/4 of their normal size.
Well, the modified shakers are still going strong. I think they are much better now at
avoiding the upper end of low bass from leaking into the seating. The new found depth of
"bass" extension blends well with my subwoofer's fall off. Before the
modification they didn't extend much below the sub. Now they definitely do.
Feeling the water rushing around in Titanic or the Apollo 13 launch sequence is really
impressive AND we don't go deaf going after the effect.
Get those Dremel tools out!