Elliptical enclosure - reflection/diffraction issues?

[novec]

I'm toying with different enclosure designs and came up with an elliptical enclosure with a minimal protruding baffle. Are there any inherent reflection/diffraction issues with an ellipse when the voice coils are outside the actual ellipse?

It's a CNC cut sandwich design, so I've got a lot of freedom regarding bracing and just about anything else. I have a feeling the alternating "spikes" will help even if their size is random, but it'd be a lot easier to leave them out.

I'll be running digital crossovers and room correction/equalizing on a dedicated PC, so it'll be relatively simple to correct for baffle step an all that, but internal reflections are still a bad thing...

Comments?

[sreten]

Hi,

FWIW a driver mounted centrally on the end of a cylinder is not good
for diffraction induced ripple, so not that good for the tweeter or bass.
Varying path lengths smooths the ripple.

rgds, sreten.

[novec]

By varying path lenghts do you mean ellipse vs circle, the "spikes" I've added, or something else?

The enclosure will be divided between bass and mid, so they'll have separate enclosures.

[SunRa]

Also, the baffle you are mounting the drivers on will not help control diffraction. If you go the trouble of making those nice elliptical baffles, try to mount them directly on them, by flattening a part of the elliptical baffle. Those nice round edges (in fact no edges at all) will do miracles.

[novec]

D'oh! I was afraid of something like that... The problem is that flattening the ellipse will more or less remove the elliptic shape all together, unless it's wide as a small country. But the basic concept of having a huge baffle radius can be exploited in different ways. I'll be back!

[MJL21193]

Your design looks good to me. I see no problem with the baffle as you have drawn it.

[novec]

In order to get the ellipse baffle advantage it'd have to be something like this, but it's too big and quite frankly too ugly... But there might be other ways to get that benefit. I'll be back again!

[novec]

Uhm - no, I won't... I was working on variable blends from the baffle to the main ellipse, but I don't have the skills in 3D curves to do that. So I think I'll choose to listen to the comment that suits me best

But back on topic - any comments on internal design?

[MJL21193]

Originally Posted by novec

any comments on internal design?

The offset triangular pattern on the walls should dissipate mid-high to high frequency back waves but I'm sure that stuffing would do this just as well and some lower frequency too.
As for bracing, it should need more than a cylindrical chamber, as there is an unequal distance from the centre to the 'sides' - the flatter sides will be more susceptible to a lower frequency resonance.

[novec]

How about this one? The flattened front and back are just wide enough for the mid and a 30 mm blend, so bulges for the woofer seem like a decent tradeoff. The flats should be good for standing waves, too, so I can skip the triangles. It's far more volume efficient, too.

It's not quite as flashy as the original design, and looks a lot like designs I've seen before, but neither of those are necessarily bad...