new speaker baffle design concept...good or not?

[thadman]

I was thinking today about wide OB and narrow OB and the benefits of both (wide=later rolloff, narrow=less baffle reflections) and realized an idea.

First off, for this to work at all, I need to know if quarter wavelength foam will absorb the entire frequency (it wont pass through the foam). If thats true then I could use a deep foam baffle (absorb all baffle reflections, but maintain width) and use a wood frame and then cover the whole speaker in grille cloth so the foam wouldnt be visible.

24" wide baffle with 7" deep foam across the entire baffle (the speaker will be suspended with a frame)

the 7" (1/4=28") foam would absorb all baffle reflections down to about 480hz where the dipole cancellation would take care of the rest.

[cam2Xrunner]

What is OB? I've never heard that term before?

[thadman]

open baffle (dipole)

[cam2Xrunner]

Ah ok thanks

[03blueSI]

Sounds like it should work in theory. The only thing to think of is that around the speaker you would probably want to make sure that there is enough room and that the material gradually increases thickness near the speaker because I would think that if the speaker was shrouded too much that it might reduce the width of the soundstage and also might make the speakers more susceptible to beaming.

[03blueSI]

I should have mentioned also good luck. I may play with some open baffles here in a minute until I get the rest of my system together. I bought a set of the scanspeaks on the group buy and I have some 8s and a pair of DLS tweeters that I am not using in my install so we will see, either an open baffle or a TL design may be in the works just to see what kind of sound these little buggers produce.

[demon2091tb]

Sounds very possible, but the baffle width would still need to be decently wide enough to get considereable info under 100hz i'd think. That is unless you have a push-pull type H frame config.

I may be wrong though but are you speaking on terms of midbass duty........could you try to explain this a tad better, not quite following fully, but it sounds very intriguing.

[thadman]

I would make a compound tower speaker, each section would be 24" tall

The top portion would house the tweeter (resting at ear level) and the midrange (right below the tweeter). It would be arranged in a sort of trapezoidal shape (for aesthetic purposes), being slightly narrower at the top. The frame of the speaker would be MDF (or some other very stiff material) and the speakers would be mounted on rings which would be connected to the frame. The frame would then be filled in with 7 to 8" deep foam to absorb all reflections.

The top portion of the tower would be covered in grille cloth, so the foam wouldnt be visible.

The midbass 15" would be placed on a solid MDF 24" x 24" (height may differ, I may experiment with different heights so as to limit lower vertical extension). It would be crossed over before 560hz (~24") so all frequencies will be subject to the dipole effect and will thus there will be no reflections on it.

I could experiment by shortening baffle height (placing midrange on super wide baffle, but short so dipole effect cancels upper and lower waves) to minimize vertical off-axis response (ceiling and floor reflections)

[thadman]

-or-

Here's another possibility

I could make a slanted lower baffle with wings that extended its depth to 8". I would then take a solid piece of MDF with 8" sides (front top and bottom, imagine an open-backed box that was filled with foam and flipped around) and mount it at the very back of this. I would then mount the drivers to this baffle and place the 8" deep foam in front of the baffle and carve a section out for the speakers to fire through (15* vertical and 30* wide), a sort of foam waveguide whose purpose isnt to make the drivers more efficient but instead to make them more directional.

[rollandburn]

excuse the nothing post... just need to get my post count to 1 to start a thread