My Striplam SR71 Notions...

[raypalmer]

I'm curious as to whether what I've done here has any real merit acoustically...

Basically a striplam assembly is the plan. But I've seen pics of enclosures (I think they were back-loaded horns though) where the chamber was dimpled, in effect, rather than damped in any traditional sense. Now I'm aware that an irregular surface will cause sound to diffract accordingly. And I'm also aware of the golden ratio being something to be mindful of. So the next thought was to combine the two notions and make golden ratio dimples.

What I did was design the inside of the enclosure with radiuses alternating from .6, to 1, to 1.618. Which I figure in my non-engineering little mind would create the least reflection issues in a totally un-damped enclosure. To further this each ply of 3/4" in the striplam will have a diometrically alternating set of radii. As shown in the photo where I have one smooth-edged ply, one with one set of radii, and one with the opposite. Result is a sort of dimpled-to-the-golden-ratio enclosure no?


I guess part of what I'm trying to do is make a speaker with no felt or batting, Totem's are like this (unpadded) and are quite good sounding commercial speakers IMO. Although how (or whether) they defeat the backwave I don't know. My only other thought was applying a product I've come across that's used for small jewelry boxes and whathaveyou. It's basically a dust of little fragments of some textile, one applies a brush-on adhesive to a surface and then presses the dust on to the glue and, after blowing away the excess you've got a kind of ultra-thin felt like surface. Interests me as a kind of half-way approach to damping without really substantive felt.

Anyway, I know someone somewhere's thought of this already... still..

[Andy G]

I suspect that the dimpling you have indicated might have some minor effect, but the same could probably be accomplished with using the right wadding on the inside.
One thing you can be pretty darn sure of, is that the translam type construction will go a long way to reducing panel vibrations that might occur in a rectangular box if it had insufficient bracing.

Here is my interpretation of the ER18+ TDFC, translam with real timber.. (not an SR71, since it uses a very different x-o)

[raypalmer]

Beautiful speakers there andy. And yeah if I'm going to make a bookshelf I'm going striplam...

As for the wadding... the idea is to get away from it. I know it's the easiest way around the backwave but I'm just keen to build a speaker without batting or felt all together. Just as an exercise. Worst comes to worst I'll end up stuffing them anyway right?

[Andy G]

Originally Posted by raypalmer

but I'm just keen to build a speaker without batting or felt all together. Just as an exercise.

If that's the reason.. then I say.. GO FOR IT !!!

Let us know the outcome..

ps, I do suspect, however, that no matter what you do, it may sound a tad echoey if wadding is not used, I hope you prove me wrong

pps.. the easiest way to avoid reflections from the back of the cabinet, is to not have a cabinet..

[s7horton]

I recently did a cabinet for the SR 71 very much like what you are describing but without the dimpling... I did end up stuffng the cabinet.. Here are some quick photos:

[raypalmer]

Exquisite Horton,

What type of veneer is that? And where'd you get that lovely binding post plate? Make it yourself?

[tsmith1315]

My only other thought was applying a product I've come across that's used for small jewelry boxes and whathaveyou. It's basically a dust of little fragments of some textile, one applies a brush-on adhesive to a surface and then presses the dust on to the glue and, after blowing away the excess you've got a kind of ultra-thin felt like surface.

AKA "flock or flocking."

Looks like loose velour fibers, and makes anything fuzzy. Could also be used for baffles, but it doesn't hold up well on surfaces that get much traffic, and it catches dust.

[badman]

That's extremely impressive work. The matched stands are sexy too!

It's a shame, though, to go through all that work and ignore the performance aspect available to you in utilizing a large-diameter roundover on the baffle, especially since you're veneering rounds anyway.

[GM]

Originally Posted by raypalmer

As for the wadding... the idea is to get away from it.

Then instead of 'dimpling' the curved walls which are already decaying away the eignmodes to the flat rear panel, 'kill two birds with one stone' by adding a proper diffuser system to it to further decay them and the ones between it and the driver, which will have far more impact on its perceived performance. Ditto the top and bottom.

GM

[s7horton]

Originally Posted by raypalmer

Exquisite Horton,

What type of veneer is that? And where'd you get that lovely binding post plate? Make it yourself?

Yes, they were custom made by my local metal working guy. The veneer is block mottle anigre.