View Full Version : CD horn eq curve
07-30-2003, 11:29 AM
Haven't seen this come up yet. Just wondered what kind of upper frequency boost are being used with 2446 drivers and 2380 horns. I need a starting point to make up some eq boost using BSS FDS 360 crossovers and EQ card.
Centred at what frequency,Q and boost? Or is it really just 3db per octave high pass filter,doesn't seem enough.
Who's using CD horns on this forum as well. I quite like these, really good coverage. How much horn distortion they cause is unknown!
07-30-2003, 02:53 PM
This is the comp curve JBL uses with the M552/553 crossovers.
2380 familly is -4db @ 2Khz unity at 5Khz and + 6 @ 20Khz.
I am using 2344's and they are just great. JBL has a new horn type out and there is a technical paper comparing the new to the old. The numbers are in there.
07-31-2003, 02:43 PM
Thanks guys, that is exactly what I need to get started.
08-06-2003, 01:12 PM
My current test system utilizes a 2421/2344 combination for the top end. I plan to compare (a) the 2421/2344 with passive EQ (ala 4430/4435) to (b) the 2421/2344 with a 2405 crossed over at 9KHz/3rd-order. Itís my understanding that the disadvantage of option A is that itís down a few dB in the last octave (which I may not be able to hear), while the disadvantage to option B is the phase misalignment. Any comments?
08-06-2003, 10:18 PM
Depends on whether you wanna take the 2405 out of its current mount, and put it in some sort of sepaerate, movable small enclosure (ie, like the Angelus C41 tweeter enclosure from the 1957 catalog), and simply move the 2405 BACK from the front baffle, until the throat of it lines up with the throat on the big horn. If you REALLY wanna do it right, test the small and big horn out of phase, and adjust the distance back until you get the BIGGEST NULL (ie most cancellation) with the drivers playing together...
This is something Altec used to recommend doing, with the VOTT systems, in initial setup... it can definitely make things more coherent, as long as you can deal with the tweeter being "way back there"...
08-07-2003, 05:20 AM
Why would you adjust for the "biggest null"? Wouldn't you want the two drivers on each side of the crossover frequency to be IN PHASE? Please enlighten me.
08-07-2003, 09:03 PM
Oops, further clarification needed...
What I meant, was to INVERT polarity, temporarily, of one of the two drivers (either the horn or the 2405), and play 1/3 octave pink noise at as close as possible in frequency center, to the crossover frequency between the horn and 2405. Adjust the distance back-and -front, until you get the biggest null (ie, most cancellation) between the two. Then, when you put them back IN phase with each other, they'll "help" each other the most... and be the most time-coherent possible, in the process.
Of course, it's possible, within usually a good degree of effectiveness, to just line up the diaphragms of the drivers, front to back. Usually, that'll get you so close, that a little tweaking back-and-forth, front-to-back, until you like the sound the best, should do it...
08-08-2003, 02:30 PM
The BSS 360 crossover has phase controls which work at crossover bands 0-180degrees and invert,hence the 360 name tag I suspose. I can do the invert the phase trick and work down the bands for maximum cancelation and then flip it in with the band invert switch, or vice versa.
Top down 2404, 2380 horn with 2446 driver, 2206 mid cone, 2226 bass.
I tried it and it works, even 2206 to 2226 transition sounded much more coherent even with a low crossover point of 80hz!
Despite conflicting paterns of ring radiators and bigger horns I think they can be made to merge in a pleasing sound.:cool:
I am now on a 24db and 18 db on 2404 combination research drive. I should have much tech info not in the PDF manual on these crossovers by next week.
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