Wednesday, November 30, 2011

Upgrading My Powered Subwoofer for Hi-Fi

I had been supplementing the low end on my ol' hi-fi with a crappy 30-watt powered subwoofer that came with some boxed surround sound set I purchased a number of years ago. It uses an 1/8" jack for input and drives a 4.5" (I think) woofer in a 4th order bandpass enclosure, like this:
However, the sound was pretty lackluster and failed to really produce anything much below 50 Hz, so I decided to kick it up a notch with some spare equipment I had laying around.

The stock woofer was highly inefficient when trying to play low frequencies, and was prone to "chuffing" (the sound air makes when it is quickly pushed out of the port hole) at higher volumes. The subwoofer's amplifier, however, is quiet (no humming, even with the volume cranked) and I like the simplicity of the 1/8" input (fewer wires jumbled up behind my setup), so I decided to bypass the crappy stock speaker and use the amp to drive a more capable bass speaker.

I had a spare Electro Voice EVM-15L driver with matching enclosure that I used for playing bass guitar, so I cut a 1/4" patch cable in half to get at the bare signal/ground connections without damaging the existing enclosure (in case I decide to use it for bass guitar again at some point) and disassembled my little subwoofer enclosure.

The subwoofer amplifier stage is mounted on a plate that came off easily after removing 8 little screws. A single wire connected the amplifier to the crappy stock speaker, so I cut that and pushed it to the outside of the enclosure to power my EV 15".

At this point, I could have removed the amplifier plate entirely from the old enclosure and woofer, but I didn't want to have a bunch of bare circuit boards laying around, so I routed the aforementioned cut-wire out through one of the screw holes and then screwed the plate back into place on the enclosure.

Unfortunately, when I connected the now-liberated amplifier to my EV 15", I experienced a lot of clipping, even at low volumes. I suspected that this might be a problem with the impedance of the driver not matching up with that of the stock driver, so I wired a spare 8-ohm resister in series with my EV, which fixed things right up. Now, it sounds great and has much more volume than I could ever want/need (the EV's SPL at lower frequencies is, unsurprisingly, far greater than the stock driver's).

The bass is smooth, punchy and you can feel it in your guts, unlike the piddly, flatulent sounds of the stock configuration. I've heard a lot of audiophiles say that "pro" audio gear is inappropriate for hi-fi use, but my experience demonstrates otherwise.

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