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In Reply to: Re: Won't a simple lens help merge DDS-90 to larger woofer? posted by Bill Fitzmaurice on February 25, 2007 at 08:34:25:
Bill,I also have these DDS waveguides and the Altec 416a's.
If the waveguides were moved back from the front baffle and the crossover was set at 1700 hz with a 3rd order butterworth do you think it would work? I can adjust for driver alignment with the Behringer DCX2496.
On the other hand I can just leave the existing Altec 811b's.
These waveguides do offer a significant improvement over the stock 811b's however I can not estimate if this improvement would outweigh the directivity (beaming) issue.
Thanks,
Don
Follow Ups:
It's a double edged sword. The narrower the slot the less beaming, but at the same time the air mass within the chamber increases. That chamber acts as a low-pass filter, so you get wider dispersion but at the same time reduce HF extension. The way to get around that is to move the slot back, closer to the cone, to minimize the volume of the chamber between the cone and slot opening. I've incorporated just that feature into the horn throats of my two latest designs.
Hi,I'm not able to interpret your recommendation "The way to get around that is to move the slot back, closer to the cone, to minimize the volume of the chamber between the cone and slot opening."
Does this mean placing the waveguide closer to the woofer cone on the front baffle?
Thanks,
"Does this mean placing the waveguide closer to the woofer cone on the front baffle?"
Yes. Think of a cone shape that fills the volume between the baffle and driver cone, with the aperture going through it.
hi Bill - I think Don M is referring to "time alignment" of the DDS conical waveguide vs his Altec's 416 plane while you're discussing a phase-plug-like adaptation of a rectangular diffraction slot to cut down on cavity resonance and path errors:^)
best,
Freddy
I initially was commenting on your measured results with versus without the lens, assumed he was doing the same.
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