Geddes on Waveguides

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#3,482
GD,
It was a DIY ribbon. Here is a similar ribbon but without WG.

1"x45" ribbon, no EQ

WingsRibbonCSD.jpg


Since it didn't have WG, I don't want to clutter Earl's thread too much.
Paul
 
#3,484
Hi Paul,
if Ur own ribbon worked in the same fashion I can only join the exclamations and say: good work!
I do however seem to spot some possible 'grid or edge' diffractions in the mid to high mid? But the damping the waterfall shows to be remarkable.
Is there (or where) another thread where this is covered, since I aggree not to disturb Dr. Geddes unduly.
Regards
a1greatdane
 
#3,487
applehorn said:
alcons audio - evolutionary audio solutions ®

You might have missed this. Not available in the USA at the moment, and only in their finished product.

Iain.
UK
Click to expand...

The thing is, beyond what I said before, ribbons are the wrong shape for good directivity control - they are very hard to do a good waveguide for. And, as I said, the bottom line is that they end up working like a compression driver. I've know lots of people who try them, but nobody who has stayed with them. Theoretically I just don't see an advantage.
 
#3,488
gedlee said:
The thing is, beyond what I said before, ribbons are the wrong shape for good directivity control - they are very hard to do a good waveguide for. And, as I said, the bottom line is that they end up working like a compression driver. I've know lots of people who try them, but nobody who has stayed with them. Theoretically I just don't see an advantage.
Click to expand...
I actually have one design in the works using a driver that is called a ribbon, but is actually a modal radiator type.
 
#3,491
Ok we modeled Gaussian waveguides and with 1 meter mouth we've got 900Hz. Pretty high. Another equation for optimal throat area:

Code: 
S = ((Rg+Re)*(ro*c*Sm^2))/(Bl)^2

Rg - source resistance
Re - vc resistance
ro - air density (?)
Sm - membrane area
Bl - force factor

This means that membrane, suspension and rear chamber resonance must be at the middle of a horn bandwidth and Qtc low so that load resistance and (Bl)^2/(Rg+Re) as high as possible. That's old teaching right?
 
Last edited:
#3,492
jzagaja said:
Ok we modeled Gaussian waveguides and with 1 meter mouth we've got 900Hz. Pretty high. Another equation for optimal throat area:

Code: 
S = ((Rg+Re)*(ro*c*Sm^2))/(Bl)^2

Rg - source resistance
Re - vc resistance
ro - air density (?)
Sm - membrane area
Bl - force factor

This means that membrane, suspension and rear chamber resonance must be at the middle of a horn bandwidth and Qtc low so that load resistance and (Bl)^2/(Rg+Re) as high as possible. That's old teaching right?
Click to expand...

I think thats based on optimal impedance matching for maximum power transfer. Thats not how I would define "optimum".
 
#3,499
jzagaja said:
Earl, what do you mean by centroid location in:

Compression driver plug - Google Patent Search

0.199/0.345/0.446/0.528

it doesn't lead to the picture. What is missing?
Click to expand...

I believe that the picture is correct. The centroid, is a fancy word for the center, but not necessarily the geometrical center (as seen in some view), but in this case is the center as defined by splitting an area. For example when you find the centroid of an annulus, it is NOT the physical center of the two radi. If you don't understand that then you need to brush up on your geometry.
 
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