Aurasound NS15-992-4A motor exposed

[jhaider]

I had something fall into the gap of one my Aurasound NS15-992-4A subwoofer drivers while it was in storage, so I had to take it apart and clean it out. I thought someone might like to see the innards of what might still be the finest bass driver design made. The motor easily unbolts from the top assembly (basket with cone/coil/suspension glued in).

Aurasound's claim to fame was their "neo radial technology," which used segmented neo magnets around on a massive hunk of steel that served as polepiece, top plate, and bottom plate. The voice coil is underhung, so the magnets are something like 2" long. Maybe a little less, but the point is they extend deep into the pole.

For perspective, a 99.2mm (~4") voicecoil moves in that gap. Note also the full copper sleeve on the polepiece, which is one reason why these things have the inductance of tweeters. (The other is the short voicecoil - remember underhung, so the whole coil is always in the magnetic gap.)

I should have taken a top assembly picture, but did not have the foresight. Here's how a pair of NS15s looks mounted though.

No grille because they face the wall. The Speakons on top are for output to front left (white gasket) and front left height (yellow gasket). Drivers are wired in series here.

 

[jhaider]

I found this cutaway online that may give you more insight into the pictures above. You can see the full copper sleeve on the pole, the underhung voice coil (magnetic gap longer than coil) and how much steel is in the thing.

 

[jhaider]

Some dead NS15 pics. The reason I cleaned out the woofer above is one of the woofers in the sub above died. I had forgotten I put it inside a different cabinet. I recently pulled that cabinet out because I realized it would fit perfectly in some wasted space under my desk (and who doesn't want a 15" sub in a desktop system, lol). Obviously when I fired it up...things weren't good. While the motor looked fine, the top spider had a dent on the last positive roll:

Due to the dual spider design, I could not get under it. No idea what could have caused that.

It also looks like there may be a burn on the voicecoil.

Unlike most high-powered sub drivers these Aurasound drivers had relatively short (underhung, remember) and single-layer coils. (Many subs today have 4-layer coils). So I guess they're more fragile than some. Still, this one had been in continuous use from at least from 2006-2021, so it gave good service. Ironically, I replaced it with a similarly old (albeit barely used) Oaudio/TC Sounds TC2+ 15 - see this thread for more on that old warhorse.