Product Review

Earthquake XJ-300 Switching Amplifier for Earthquake Shakers

July, 2007

John E. Johnson, Jr.



● Class J (Switching)
● Power Output: 225 Watts RMS
● Dimensions: 2" H x 6" W x 8" D
● Weight: 5 Pounds
● MSRP: $299 USA

Earthquake Sound


Hot on the heels of the Earthquake "Quake" shaker and XJ-600R power amplifier that we reviewed, Earthquake Sound is getting ready to release the XJ-300 power amplifier.

The XJ-300 has a 225 watt output, and does not have Room Correction, a remote control, XLR input, or some of the other features that the XJ-600R has. It is also much less expensive ($299 compared to $1,399).

The XJ series are Class J, which is a quasi-linear design, with some AB bias, but also some switching characteristics. It is a new type of amplifier design said to be extremely (99%) efficient. This means that a lot of power can be packaged into a small chassis, and that is important for a shaker amplifier that might end up under the couch, as it has in my situation, where space and heat dissipation are at a premium.

The photo below shows the XJ-300 sitting on top of the XJ-600R. The XJ-300 is about half the size of the XJ-600R. It's very light in weight, and comes with either a standard rack mount sized front plate, or a narrower plate that is the width of the amplifier itself.

Unlike the XJ-600R which has controls that make it suitable for driving a subwoofer, the XJ-300 is minimalistic. There is just an On/Off toggle (it is also Auto/On), Volume, Crossover Frequency, and Phase. To me, the XJ-300 is the best choice for use with the shaker, because it is simple, and I don't think the advanced features of the XJ-600 are necessary with this device.

Shakers are low impedance and usually require high power if the shaker mechanism has a lot of mass. So, I was a bit worried that 225 watts might not be enough to give me the tactile sensations I want when I watch such movies as Battle of the Bulge, which just came in for review in Blu-ray High Definition.

Below is a photo showing how one of the Quake shakers is mounted on my reclining chair. You can see two aluminum arms that are bolted to the side baseboards on the chair, and the other ends of the arms are bolted to the Quake. So, when the shaker vibrates up and down, this transfers energy to the chair by means of a lever.

I cranked this baby up with a bunch of movies, with the latest one being the Battle of the Bulge film I mentioned above.

This particular movie was made a long time ago, way back in the 1960's, but it had a powerful multi-channel sound track because it was produced for Cinerama by Warner Brothers. However, even though it was a big budget film, the sound shows its age, but the picture - having been shot in UltraPanavision (70mm) -  is spectacular.

The Quake and the XJ-300 were more than adequate to practically raise my chair off the floor when the Tiger tanks stormed across the Ardennes forest of Belgium in December of 1944. This made a huge difference in the experience of the story because when I was seeing a 57 ton tank on my 6 foot screen, my chair should darn well shake.

Of course, more modern films have deep sound effects all over the place, and in fact, I had to turn the XJ-300 volume down a bit just so my eyeballs would stop rattling in their sockets. Regardless of the volume, the XJ-300 barely got warm.

The XJ-300 will be offered with the Quake in a package deal, competitive with other shakers out there.


The bottom line on the XJ-300 is that it has all the power you will need to drive a Quake chair shaker. It is very affordable, about as easy to use as any amplifier I have ever tested, and stays cool enough to keep under the couch with Auto/On engaged. I now use one amplifier to drive a shaker on the couch where my wife sits, at a more respectable volume setting, and one amplifier to drive a second shaker on my chair, set to a much more disrespectable volume level that borders on the sinful.

- John E. Johnson, Jr. -

Copyright 2007 Secrets of Home Theater & High Fidelity

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