Crossover & 1x1 Filter Graph Issue

radcro

I am planning on using a DriveRack 260 as a crossover for 3 Apogee AE5 speaker cabinets as I have removed all of the original Apogee processing units that the AE5's came with.

As a test for the high frequency compression driver, I created a Driveware Program that uses input 1 (or "A" in the graphical PC software) and input a sine wave sweep that ranges from 75 Hz to 2000 Hz (2kHz).

I created a 1x1 filter to cut off the low frequencies that may harm the replacement high frequency compression driver (Eminence PSD: 2002 crossover spec @ 1.2kHz/18dB). The picture below depicts the graph I setup for the 1x1 filter on the Driverack 260.


HighPass 1.297kHz, High Slope BW 18 dB/Oct, Low Pass Out. Ultimately the Gain will change to -7.1 dB but for the purpose of this test I left it at 0.0 dB.

The next oscilloscope graph (oszilloscope audio frequency analyzer) is the 1x1 filter output that would ultimately go to my power amplifier. The yellow line is set around HighPass 1.297kHz


My question is why don't these graphs match and why when I plug the DriveRack 260 1x1 filtered output into my amplifier do I hear the frequencies that should be filtered out? Shouldn't any frequencies below 825 Hz be filtered / cut off to infinity by the DriveRack 260 1x1 filter? Is it that the graphical representation of the DriveRack 260 1x1 filter graph and any crossover settings are inaccurate?

Any help would be appreciated.

Dennis

The DR260 crossover window is just a visual aid for setting up filters....not intended as a measurement trace. If you feel you are getting to much low frequency from the horn, try LR24 or BW24 for a steeper "wall".

Gadget

The "usable" frequency response is 1200hz -20KHZ... you cross that driver that low and it won't last long unless your intention is easy listing..like Lawerence Welk...

The recommended frequency is 1600 hz @ 18dB/ octave filter (and I take that as a minimum...) you will be affecting the longevity of the driver diaphragm if you do...

JBL has a 4" diaphragm in the 2447 and typically specs 1100 - 1200hz for it...and its a HELL of a lot more driver than the PSD-2002...I'm a dealer for them and I have used them for years and even in monitors 1500hz is too low...and they broke down (the titanium cracked or the voice coil separated) prematurely...

Also, remember that the number you specify in the 260 is the ELECTRICAL crossover point, the acoustic point could well be lower...(or higher)

G

radcro

Thanks to both Gadget and Dennis for your replys. The info you both provided gives me a good direction to head in. The actual electrical output graph depicts, within a few dB, the correct BW 18dB/Oct slope. I will use your advice to set the crossover point higher and use a more drastic slope like L-R 36dB/Oct or L-R 48db/Oct. The cheap PSD:2002 was picked specifically so we can replace them frequently. I've been running 6 PSD:2002's for about 6 months at about 75 watts and they have performed better than I expected (all 6 still working well). I would love to buy the 2447 JBL's (or any JBL's for that matter) but the 6th largest venue in the nation supposedly can't afford them for replacements. Cheap %&#@'s.

Thanks again for all your help!

Gadget

I wouldn't use the JBL's anyway if it were my choice.. too harsh...The B&C 750 or the Neo P Audio's are far more desirable sonically. The later is less than 1/3 the price of the JBL as well...

Remember also that the deeper the numbers in the crossover slope the more complex the filter... and the more phase and other factors are affected... I picked the LR24 filter because it inverts the phase 180 degrees ... and not some other less manageable number. There are other considerations, but suffice it to say each crossover point has it's own drawbacks...and the desired effect here is simply to minimize the interaction between the drivers in the crossover region.

Of course it is also important to make sure to use similar crossover types adjacently...

G