I picked up a pair of JBL JRX115's as a project. One is good, the other has blown drivers. Looking to learn, I bought a UMM-6 microphone, a Dayton Audio Odeum 15N woofer, and a JBL Selenium D220Ti compression driver. Installed REW and measured the new drivers individually, installed in the enclosure.
My measurements, especially with the CD, seem to roll off much faster than the curve in the specs of the Selenium D220Ti. This is even more evident when putting my measured readings into an FRD file and load it into VituixCAD to work on the crossover. I can get the response graph looking pretty flat, but I am concerned that this is without a resistor on the CD. Should I still add a resistor and let the high frequencies taper off, or run it without a resistor?
I also measured the working box with the stock drivers and found that the curve is not flat and tapers off in the high frequencies. I dont want the highs to get out of hand in a PA setting, so maybe adding a resistor to taper it off is the way to go? Looking for suggestions. Thanks!
PS: While gathering the factory response graphs for the D220Ti, I realized that the flat response is the one in an Anechoic chamber. The plane wave tube graph looks a lot more like mine. Maybe that is the difference.
My measurements, especially with the CD, seem to roll off much faster than the curve in the specs of the Selenium D220Ti. This is even more evident when putting my measured readings into an FRD file and load it into VituixCAD to work on the crossover. I can get the response graph looking pretty flat, but I am concerned that this is without a resistor on the CD. Should I still add a resistor and let the high frequencies taper off, or run it without a resistor?
I also measured the working box with the stock drivers and found that the curve is not flat and tapers off in the high frequencies. I dont want the highs to get out of hand in a PA setting, so maybe adding a resistor to taper it off is the way to go? Looking for suggestions. Thanks!
PS: While gathering the factory response graphs for the D220Ti, I realized that the flat response is the one in an Anechoic chamber. The plane wave tube graph looks a lot more like mine. Maybe that is the difference.
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Every horn a CD is mounted on will produce a different magnitude response, but all of them will requrie some EQ to flatten the high end. In this case the driver combo may require upwards of 10dB of L-pad to match woofer-tweeter levels so there is also that much HF boost available in the passive crossover, you just have to add a capacitor to bypass the series resistor at 6dB/oct starting somewhere around 4-8khz.. measure and experiment to find a setting you like.
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That response looks better than the stock driver.
The reason the factory response graphs for the D220Ti show a rising response upper is because the beamy exponential HL14-25 polar response drops from ~90 degrees at 2kHz to under 30 degrees at 8kHz:
Zingy!
Art
Thanks for the input guys. That HL14-25 certainly does narrow as the frequency goes up. Once the weather warms up I am going to do some further testing outside. Maybe I will leave the factory crossover in it. These new drivers with stock crossover sound a lot better than the factory speaker, maybe I will be happy with that. Maybe I'll replace the drivers in the other one... who knows.
Yes, these should do much better than the original parts M115-8A and 2412 compression driver. Actually the D220Ti has been a popular modification for the JRX series speakers for quite some time.