Cylindrical cardboard enclosures/ vibration/ diffraction

[rick57]

Has anyone built or heard cylindrical enclosures?
Sonotube cardboard has been used for subs, but my research on enclosures: Dickason Help! How does make "dead" cabinet? and especially the link to Art Luwig:
http://www.silcom.com/~aludwig/Louds...ng_experiments
indicates (if correct) “bracing helps only at the lowest frequencies, below 100 Hz”.

{BTW Art’s experiments showed that best for damping vibration was “2 layers of 30# roofing felt that costs $0.17 per square foot”
This must be a US term.
Is this bituminous felt? Thickness ??}

For a mid range, or a two-way without a lot of serious bass, cardboard tubes would be much easier to build, Dickason quotes tests (1951) showing smoother FR than a box, and that a cylinder is almost as good as a bevelled rectangle.

If they’re that good, why are cylindrical speakers almost non-existent - there must be drawbacks

Anyone know the diffraction on the front of a cylinder?
One way to minimise diffraction, apart from flush mounting, is to put a larger cylinder around the cylinder containing the driver, and mount a curve to join the two, like the curve often used on the front baffle to reduce diffraction.

[rick57]

When Dickason summarised Harry Olson's 1951 JAES article "Direct Radiator Loudspeaker Enclosures" on tests on 12 different shapes, he didn’t make the results clear.

Of the two cylinder shapes, one with the driver mounted on the curved surface, t’other with driver on an end, on re-reading the Cookbook, it’s not clear which one gave the good result.

Anyone know/ have Olson's article or a link to it?

I was going to try the 'cannon mount' - driver on an end.

BTW a sphere was best, but not by a huge margin, for a lot more work.

[roddyama]

Hi Rick,

Here is a link to a very nice design based on cardboard sonotubes:
Ouch! $100.00 for brass mounting hardware

It's a start. The discussion of baffle shape, speaker mounting, and defraction is pretty broad and has been covered many times on the forum. You might try some more pointed searches.

Rodd Yamashita

[rick57]

Thanks Rodd
Dynamat is probably more than $0.17 per square foot
So for cost effective damping
Anyone know a source of *US term* "roofing felt "
Is this bituminous felt??

TIA

[PaulyG]

You are correct, roofing felt is bitumen felt. Mostly used for flat roofs. However most of the "felt" these days is really fiberglass instead of natuaral fiber. Don't know if that will change the damping characteristics.