Compression driver frequency response?

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Compression frequency response is given with specific horn.
I want to test horn with two different compression driver.
I want to see which compression driver is having better frequency response with available horn.
I have got LMS with me. But no anechoic chamber.
Guide me in the matter.
 
Testing them should be no big deal. I am assuming you have done measurements before as you have LMS. Do an inroom measurement and gate using MLS. I would also run a limited range sine sweep. They should both be the same. Don't know how large the horn is but above 800-1K you sould be fine depending on how large the room is. Do the measurements outside if you can.

Compression drivers roll off above their mass break point at about 6db per octave. Depending on the horn type you may need to do a compensation circuit to smooth the response and flatten things out.

On a CD type horn using passive components you would need to pad down the midrange response to give you a flat curve. Simple example would be a circuit that gives you the reverse of the 6db roll-off. Typically a series capacitor is used to do this.

With an exponential horn they self equalize so normally no compensation circuit is needed. They use the change in directivity to smooth the on axis response.

What you need to do is measure the impedance curves and on on axis response for each driver on the horn and then go from there. You could also do off axis measurements as well.

When you measure the compression drivers as a safety net you can use a large value capacitor in series to protect the driver from excessive excursion and fumbly hands. If you are not sure of the value use the manual from an active crossover and look up protection caps. You don't have to use them but it's an option if you don't feel comfortable without one.

http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/JBL-5235 manual.pdf

Depending on what you get you can decide if you need to build up a compensation circuit of not. If you have Crossover Shop you would load the FR and Imp into the Guide Curve library and then into the driver. Then you just go from there.

That should get you started have fun

Rob:)
 
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