Music thing: The Sixty Inch Subwoofer

Each week Tom Whitwell of Music Thing highlights the best of the new music gear that's coming out, as well as noteworthy vintage equipment:

Yes. It's a Sixty Inch Subwoofer. No, it's not new, and it's certainly not coming to a car near you soon (not even the new Renault with three iPod docks). This is a one-off custom unit built in 1997 with the help of a physicist from Georgia Tech: "The cone moves 6 inches peak to peak under full-tilt output... Unfortunately, Tim and his crew didn't realize just how much acoustical power the sub could generate, and didn't build the vehicle to contain it appropriately. Even at less than 1/2 output, the doors were blown off the tracks, and the entire vehicle ballooned in and out several inches."

For car audio freaks, bass is a weapon. Search YouTube for 'subwoofer' and you'll enter the slightly alarming world of extreme bass - clips of girls' hair blown up by the bass, and speakers catching fire under the load.

For audiophiles, bass is expensive. The biggest subwoofer in the world is an underground chamber containing 16 eighteen-inch speakers, built underneath what they call "the greatest audio room for private listening in the world". Incredibly, the sixteen speakers are all driven by one eleven-watt tube amp. That's eleven watts, not eleven kilowatts. Awesome.

[crescentdave @ Oct 13th 2006 5:42PM]

Always interesting in a disappointing way to confirm my opinion there's a large number of dimwits who use their buzzsaw rather than their brains to respond to posts in their phobic and superstitious ways. Devolution at it's finest.

Meanwhile ... two great examples of the power of sound and the level of refinement possible with the tuned rooms.

[Daniel Heller @ Oct 13th 2006 5:47PM]

Great to see the idocy and homophobia from the normaly enlightened engadget readers.

[CharlieX @ Oct 13th 2006 5:04PM]

You know you're too old when the music's too loud.

[Enzo @ Oct 13th 2006 5:33PM]

Man, my SVS is only a couple of feet long. I feel so inadequate.

[Mike @ Oct 13th 2006 5:37PM]

It isn't how many WATTS are produced, but how many AMPS are behind it. A little something Ipicked up when I talked to a professor that taught electronics. He had an 8 watt dual channel amplifier that came out of an old movie theater. I couldn't believe how huge the capaciters were on that thing...

I forget how many AMPS were behind it, but the number was pretty high.

My Onkyo 6.1 receiver (I forget it's model now) is only 85 watts per channel but has a higher amperage output than most (if not all) "100w per channel" receivers...

[evo @ Oct 13th 2006 11:47PM]

Mike--

Huh? 8 watts in a movie theater doesn't make any sense. Are you sure he didn't show you 8 *ohm* speakers?

In any case, I think you misunderstood. Power (watts) = amperage * voltage. The loudness of what you hear is measured in units of power (energy per unit time, i.e. watt), not amperes. The same power can be produced by high amperage and low voltage, or low amperage and high voltage. A paltry 8 watts is a paltry 8 watts in either case. If you can't get a high voltage (for example, in a car's power system), then to increase power you must increase amperage to increase the power. This might explain why those speakers had large capacitors.

There's no inherent benefit I know in having a high amperage system, and it's actually more dangerous and lossy to have a high amperage electrical system--power lines send electrical power at many thousands of volts but relatively low amperage to reduce losses due to resistance. For humans, high voltage can be painful, but high amperage is deadly. It only takes a few milliamps across the heart to stop it.

[Rick @ Oct 13th 2006 5:42PM]

A submarine would probably mistake that thing as a VLF transmission, then shoot a nuke at Norway or somewhere.

[Scott @ Oct 13th 2006 5:45PM]

That's something I've been learning as I've been researching high end audio. It doesn't take much to drive the right kind of speakers. You can clear a room with a 5-10 watt tube amp and the right speakers on it.

[Lloyd Medley @ Oct 13th 2006 5:45PM]

WoW, that must be LOUD

[John @ Oct 13th 2006 5:49PM]

They made a 50-60" subwoofer on mythbusters once. It didn't last long though.

[Corey @ Sep 8th 2007 3:32PM]

i remember that

[computer.dude.28 @ Jun 26th 2008 10:52AM]

lol it was IN the car, driven by the car's engine :D

[Tony @ Oct 13th 2006 6:37PM]

It's called Ohm's law guys.

[ED @ Oct 13th 2006 10:44PM]

1.21 GW?

[Enzo @ Oct 14th 2006 1:03AM]

One thing you don't seem to take into account is high efficiency speakers. Wattage isn't the only thing that determines actual volume, so like others have said in this post, paired with the right speakers you wouldn't wanna be anywhere near 8 cranked watts.

[caleb @ Oct 13th 2006 11:56PM]

It's just like the one Marty McFly blew himself across the room with!!!

[Matt @ Oct 14th 2006 12:59AM]

Looks like Mythbusters was wrong... they busted the "blowing the doors off" story, IIRC.

[evo @ Oct 14th 2006 1:18AM]

Excellent point; the efficiency of a speaker determines how well it converts power into sound. But, a given pair of speakers driven at 8 watts, whether of high or low efficiency, will sound the same regardless of whether the power comes from high voltage or high amperage, or both. Watts is watts.

[tim @ Oct 14th 2006 1:35AM]

Thanks for setting Mike Straight Evo. If your professor doesn't know V=IR, I am not sure what kind of "professor" of electronics he is. Voltage and current maintain a fixed ratio with a given Resitance (R=V/I). Power can be calculated from voltage or current (P=V*I, P=V^2/R, P=I^2/R). You can't send more amps into a load without increasing the power.

To Evo's point above, the disadvantage of current is that is generates heat while voltage doesn't. It is true that the motion of the voice coil is driven by current through a loop of wire, but a speaker has a fixed impedance, which if you push current into a loudspeaker of fixed impedance, you generate a voltage and power.

Electrical watts are only partially related to SPL (Sound Pressure Level) goes. What matters is how effecient the driver with it's accoustical loads is at turning electrical power into Sound Pressure Level, or efficiency. Generally though it's easier to build a less effecient speaker and just drive more power into the load.

[radd @ Oct 14th 2006 3:35AM]

the brown noise...heheheheh...

[craig @ Oct 14th 2006 12:19PM]

The "biggest subwoofer in the world" may be the largest physically (who knows?) but it sure isn't the loudest or most capable. The designers are clearly horn loading and no-feedback bigots. Sure the system can develop 110dB from 11 watts and that's impressive, but 110dB in and of itself is nothing special.

When I built my house I also provided a pit under the floor. In it I placed 12 18" BagEnd subs (yeah, not 16 I know) and powered them with 250 watts each. I also didn't waste my time filling the space with curved surfaces only to ruin the effect by putting a trapset next to the listening position! For anyone who doesn't know BagEnd, look thby viewing attempts at buildinem up. They make a remarkable product that works and sounds like no other.

I'm confident that my system will easily outplay the one described in that article and I'm sure there are many others the equal or better of mine. There are businesses dedicated to these sorts of installations but regrettably no international registry of "biggest subwoofers" to counter their claim. I always enjoy reading about enormous folded horn subs and teensy amplifiers but most for the giggles aspect of it.

The 60" sub though, that's more my speed. It looks like it has a voice coil actuator though. That's too bad.

[baalpeteor @ Oct 27th 2007 9:22PM]

im trying to put 2 of deez in mah kaw now...