underhung motor designs - Buy & Sell Car Audio Equipment

GWEE · 05-20-2007, 09:12 PM

i was trying to think which subwoofers theses days use the underhung design instead of the overhung. but my mind comes to a blank....

so do you guys know of some. its n big deal just was thinking out loud.

thanks
THE GWEE

dragnix · 05-21-2007, 08:01 AM

I can really help u as I don't know anything about the two. But I am wondering on what's the difference between the designs, would be great if u can tell me

**photocrazy8** · 05-21-2007, 08:40 AM

all i know is it has to do with where the coil sits when the sub is not being played...

giantgloworm · 05-21-2007, 10:44 AM

some great older subs used that design. Audiomobile Mass subs, PPI's Pro flat piston subs. I think DD had a model with one too?

GWEE · 05-21-2007, 07:14 PM

Underhung means that it has a very short voice coil in a large magnetic field gap. The voice coils are very narrow and always move in a linear manner within a magnetic field regardless of excursion. Additionally, a traditional long voice coil (overhung) moving in a short magnetic gap presents a high variable impedance to the amplifier.

With a short voice coil in a long magnetic gap, as the music signal flows through the voice coil, the coil and the cone moving together produce the sound wave. A long magnetic gap structure offers a much wider linear magnetic flux density, alternately pushing and pulling the short voice coil back and forth. Since the magnetic force on the coil is constant and completely symmetrical with the motion of the piston assembly, the result is a sound wave with extremely low distortion and coloration, allowing it to respond much faster to a transient signal and to stop faster after the drive signal has ceased.

Compare that with the large signal behavior of high-excursion overhung transducers. Because the coil extends beyond the control of the magnetic flux field, it causes very high harmonic and transient distortion that can reach 5 - 20% whereas the underhung driver maxes out at 1%. Because of the very complex magnetic structure and complications involved in voice coil placement and fabrication, the underhung voice coil is difficult and expensive to fabricate.