Info & Answers
All Shook Up: Tactile Sound Transducers
There are lows and then there are bone-rattling lows. If you're looking to feel those LFEs (low-frequency-effects), check out these aptly-named "shakers."
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March 31, 2008 by Marshal Rosenthal

Call me naive, but I bet I’m not the only one who thought all a home theater needed in order to duplicate the sensation of explosions, bullets or ground-shaking special effects was to just turn up the subwoofer. But once we had the chance to sit on a chair where a LFE (low-frequency-effects) device was installed, we never went back. The difference was profound. Instead of just hearing these effects, you could feel their impact throughout your entire body.

Known as shakers, movers or to be more technical, tactile sound transducers, these devices can resemble a speaker (albeit without a cabinet). But rather than using a moving cone to send sound waves through the air, the LFE device creates low frequency sounds which get passed directly into the body of the person sitting on a chair or couch to which it has been attached.

Installation requires attaching the LFE to the chair’s underside. As can be imagined, this kind of placement can be rough on the furniture and so should be approached with care. Fortunately many LFE manufacturers provide detailed instructions and offer mounting brackets and other accessories to ease the process (and in some cases home theater furniture can even be procured with an LFE already installed). It’s also worth noting that it’s possible to place LFE’s within the floorboards and so eliminate the furniture from the equation altogether.

The LFE receives its audio signal from an amplifier and many of the LFE manufacturers make digital amplifiers for use here, although getting it from the company who makes your LFE is not a requirement. What is important however is to properly note at what point the frequencies should be set for the LFE being used. For this and other needed information, reading the materials provided with the LFE you purchased will help immensely.

Getting back to the setup - your main amplifier will be supplying the audio signal the LFE needs. At a basic level, the subwoofer output from the amp will need to be split using a male to double female “Y” adaptor. Then you run one RCA cable from the “Y” adaptor to the subwoofer and the other to the amplifier powering the LFE (multiple LFE’s can also be daisy-chained together). For calibrating, a good rule of thumb is to first take a DVD that has good LFE content; then adjust the volume on the receiver (or pre-amp) to the loudness level normally used for listening; then adjust the transducer amp to where the feeling it’s putting out seems good. Then you can forget about this amp since the volume control from the main amplifier will impact it when it’s raised or lowered.

The cost of an LFE ranges roughly from tens to hundred of dollars, depending upon brand. Add to that the cost of an amplifier along with accessories for mounting and even wireless kits to eliminate the wires running from the main amp to the one powering the LFE - and certainly it’s no cheap trip to a Radio Shack. Nor does that include the time spent on getting it all ready to rumble, or how your significant other might take to having the furniture altered. But the added realism this offers to your home theater can make the cost and trouble to install worth it.

So here’s a quick look at some of the companies who have LFE’s on the market. Which one will do the best job for you will depend upon your particular needs. Just remember that patience and pre-planning will serve you well here.

If you’re ready to test your new LFE, here a few specific movie scenes that have a lot of shakin’ going on:

  • The battle scenes (both war and robot on robot) from Transformers
  • The early chase scene across the buildings from Casino Royale (not the 60’s parody)
  • Superman going after the falling airplane in Superman Returns
  • The depth charges doing their thing in U-521
  • Anytime a Raptor shows up in Jurassic Park
  • Willis leaping off the roof as the helicopter explodes in Die Hard
  • Pearl Harbor Chapter 21/22 for sure
  • I,Robot with Smith during that maddening car chase scene or when he’s duking it out with the big bad CPU
  • Pretty much any action scene in Terminator 2
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