Overhung or underhung voice coils?

[Audist]

Hi,

Driver with Underhung voice coil can to be good for bass as Overhung voice coil?

Voice Coil Heigh - 16mm
HE Magnetic Gap Heigh - 6mm
give x-max of +/-5mm.


Or
Voice Coil Heigh - 5.5mm
HE Magnetic Gap Heigh - 16mm
give x-max of +/-5.25mm.


The drivers is 150W RMS power.

Anybody can help please?
Thanks.

[Andrew Eckhardt]

I think coil copper volume and surface area will be a significant determination of power capacity which will drive up the volume of the magnet structure for a given speaker with underhung motor. In woofers the increase in cost may not be offset by any meaningful increase in performance. It does have some neato factor.

[tinitus]

there is often a loss of sensitivity/efficiency with underhung
but not always
very long Xmax overhung aint too good either, in that respect
but I guess its possible make underhung with high sensitivity, keeping Xmax very low
many modern tweeters are underhung
all about compromises
no two people want the exact same driver, and part of the problem
so, many drivers are made more 'flexible' that they may actually need to be
many other good drivers are the opposite, with much too little safety margin
unfortunately probably some good ones, or would have been

[Andrew Eckhardt]

>keeping Xmax very low

or with a very big magnet and gap length!

[Audist]

Thanks,

The two driver is Morel Carbon:
https://www.madisound.com/store/prod...oducts_id=8485

https://www.madisound.com/store/prod...oducts_id=8474

The SCM634 is a "midrange" but with WinISD the bass is better from SCW636.

Idea?

[Bill F.]

Are you talking midbass or subwoofer?

The fact is, if two hypothetical drivers had identical T/S parameters and soft parts, except that one was overhung and one was underhung, they would perform largely the same.

The only difference might be that the underhung motor might have less distortion based on a more constant Le over excursion (Le/x), and often flatter BL over excursion (BL/x), too. Underhung drivers can also be made to have the least possible moving mass because the entire voice coil contributes motive force all the time, not just a fraction of winding as in an overhung driver.

These benefits accrue mostly in the midrange, which is why underhung subwoofers are so rare.

The main downside of underhung is the materials cost of the huge magnets and flux return circuits that can be required to hit BL and Xmax targets.

In the end, though, when making performance comparisons, it's not very useful to generalize. There are very well-made drivers in both topologies. You have to evaluate the performance if each on a case-by-case basis.

Edit--oops, others beat me to the post, and I see you're talking about specific drivers... Interesting how close their specs are! It almost looks like Morel used the same parts for both, except for the top plate and the voice coil.

[tinitus]

they really are underhung
not many of those around, interesting

well, the one you claim will have the better bass response
it also have the lower SPL sensitivity
often goes that way

bloddy hell, 3" voice coil for a 6" driver
typical Morel

[LineSource]

If I had my own speaker manufacturing company.

1) all woofers would use a NdFeB differential drive motors
- very linear
- very low distortion for bass
- low inductance without copper sleeve flux reduction
- acceptable Mms for bass
- cones would be carbon_fiber/kevlar loaded paper
- I believe the basic 1984 patent has expired, but new "extended" patents exist

http://www.jblpro.com/catalog/suppor...1253&doctype=3

2) all midrange would use a radial NdFeB underhung motor with full copper sleeve on the pole piece
- very linear and very low distortion
- very low Mms
- low inductance
- cones would be carbon_fiber/kevlar loaded paper

3) all tweeters would be NdFeB HEIL or advanced Ribbon designs
- Beyma TPL 150, RAAL 150-10, DIY ribbon.
- capable of both monopole and dipole radiation pattern
- waveguide can be added to HEIL, but not ribbon
- avoids the multiple distortion effects of compression driver on horns.
- superior SPL vs. freq, distortion, and polar response: wrt dome or horn
(you can DIY a $400 RAAL ribbon for about $70)

google "Measurements performed on 16 horns"
- reflected waves
- defracted waves
- high order modes

[Antripodean]

Originally Posted by LineSource

(you can DIY a $400 RAAL ribbon for about $70)

Sorry to go OT but how do I do this?

[Bill F.]

Originally Posted by LineSource

If I had my own speaker manufacturing company.

1) all woofers would use a NdFeB differential drive motors
- very linear
- very low distortion for bass
- low inductance without copper sleeve flux reduction
- acceptable Mms for bass
- cones would be carbon_fiber/kevlar loaded paper
- I believe the basic 1984 patent has expired, but new "extended" patents exist

http://www.jblpro.com/catalog/suppor...1253&doctype=3

I'm a fan of DD, too. (Currently have JBL LSR32's in my listening room.) DD can be thought of as two overhung motors working together. WRT the topic of this thread, it's fun to imagine how an UNDERHUNG DD motor might compare.