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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 half
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 pretty inexpensive.

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!