Funky sub cone shapes?

What a great topic of discussion.

I personally think it is more a sales gimic, especially with the pentagon and octagon drivers.  Kicker released the square sub to offer more cone area for a given speaker "diameter".  They rate them horrizontally rather than diagonally, so they have an advantage in competitions who decides class by speaker size.  But I see it more as perspective.  If you measure diagonally, then a round speaker of the same size will have the most cone area.

I can see some issues with possible noises in the surround from these wierd shapes.  So this could effect the SQ of the driver without some creative engineering.  I'm sure it would be an issue with higher frequency drivers if they utilized this design because cone modes can effect the frequency response.  It may be an issue with these subs as well, but I haven't seen any testing on it.

But you are right.  A cone shaped driver has the most uniformly rigid cone structure for a given weight.

Steven Kephart

Adire Audio

mode shapes... now you got me thinking.  The mode shapes of a round relatively uniform cone would be for the most part concentric.  But a square cone cone would behave like a losely fixed plate.  It would have torsional mode shapes about various axis and so forth, the pentagon would be a vibrational mess.  This can't be good.  I don't how much this would affect the sound, but I would venture it is noticeable.

Not to mention the surround, a round surround is uniform throughout, but what happens at corners, it cross section enlarges so it would tend to be stiffer, etc.  There is just alot of considerations for a non circular cone.

I'm of course guessing, but I have a feeling it isn't too much of an issue with subs.  As I said, the advantage of a square driver would be from an SPL application, and someone else made a good point that they are easier to mount together (they fit tighter together).  But from an SQ standpoint, there just isn't any need. 

Steven Kephart

Adire Audio

I've only done some real informal testing for my own personal curiosity, but I agree with Steven.  It doesn't seem to have much measurable effect in low bass frequencies as far as output.  The main thing that makes me nervous about non-round subs is the undoubtedly strange forces being placed on their surround.  There have to be some real non-uniform stresses in the corners that round speakers are not subject to.  Some formal testing would be interesting.

One obvious thing to point ut is that all the non-round speaker cones I know about are from low to mid-quality manufacturers and are designed for looks and SPL, not SQ.

What about Xtants pentagon subs? Woudl you count them as mid-quality, because I have heard that have good SQ.