tejaus Messages: 6 Registered: August 2012 Location: United States
Esquire
Hello,
I have an older pair of Klipsch Professional KP-3002 cabs that I'm trying to mod the crossovers. They're a two way with a 15" 4ohm woofer and Eminence PSD-2002 8ohm mounted on a 60 x 40 Tractix horn. I emailed Klipsch tech support and posted at their forum and haven't heard back.
The pair I have is a very early version with a hand wired crossover board crossed over at 800hz. That makes for a pretty harsh and loud horn to say the least. They both have new diaphragms installed.
Klipsch later revised the xover to around 1250hz by lowering the HF 1.5mH inductor like mine has to the 0.7mH as shown on the schematic. (I scribbled padding mods on it. I think the 15uF should be drawn in before the coil instead looking at in now)
Here are some pics of a PCB version I found that looks to have a 15uF paralleled across the existing LF cap.
I've already swapped out the 1.5mH for the 0.7mH and that made a big difference for the better but it's still hot on the high end.
According to the spec sheet for the woofer it's around 94.40 db efficient vs the PSD-2002 at 106.1db
Tue 12:22PM LEAP Loudspeaker Enclosure Analysis Program V 4.60 May 19,2009 |
| |
| ? TSL Operations Menu (Transducer Speaker Library) |
| |
| TSL Entry Num= 7 SPLo= 95.83 dB|SPLi= 94.51 dB|SPLi= 94.40 dB
| TSL File Name=KLIPSCH1 | no= 2.40 % | ni= 1.77 % |@ Eg= 2.00 V
| Name = K 1548/K 48 K 15" Woofer Rem= 0.00 O, Lem= 1.000 mH @ 1KHz
| Model= Speaker Woofer/ Midrange Rem= 0.00 O, Lem= 1.000 mH @ 20KHz
|
| Znom= 4.000 O Sd= 0.0890 M5 Fi= 34.968 Hz Hvc= 20.477 mM
| Revc= 4.100 O BL= 14.0656 TM Fo= 37.701 Hz Hag= 9.525 mM
| Krm= 0.000 mO Vas= 213.2900 Litr Qms= 4.535 Xmx= 5.476 mM
| Kxm= 1.000 mH Cms= 189.6236 μM/N Qes= 0.461 Cmx= 5.476 mM
| Erm= 0.000 Mms= 93.9800 Gram Qts= 0.419 Cmo= 1.000
| Exm= 1.000 Mmd= 78.7131 Gram Pmx= 400.00 W Tvc= 0.625 C/W |
|
| User2=8/5/92 Klipsch
My question could I use the same component values for the tweeter compensation circuit even if the crossover for the HF is a little lower than Waynes schematic? And what would happen adding that extra 15uF cap in the LF side?
Wayne Parham Messages: 18792 Registered: January 2001
Illuminati (33rd Degree)
If it's a tractrix horn, it won't need as much top-octave compensation for mass-rolloff because the horn provides acoustic equalization by way of collapsing directivity. Add to this the fact that many modern compression drivers have some diaphragm surface resonances that increase the top-octave and you probably don't want C1 to bypass R1 in my schematic. In fact, you'll probably like the sound better if that 0.47uF cap is put in parallel across the tweeter instead.
tejaus Messages: 6 Registered: August 2012 Location: United States
Esquire
Well I added a 24 ohm attenuation resistor using the 15 ohm damper resistor and 0.7mh coil. It's in the right direction but maybe a little too much attenuation. What is the ratio to figure between R1 and R2?
Wayne Parham Messages: 18792 Registered: January 2001
Illuminati (33rd Degree)
It's not as simple as setting an L-Pad, because we're looking not only for attenuation but also a specific load on the splitter filter to set its Q. You'll really need to run a program like Spice to plot the transfer function and attenuation. But I've published a set of values that give 6dB to 20dB attenuation and the (mass-rolloff compensation) transfer function I prefer for my crossovers here:
tejaus Messages: 6 Registered: August 2012 Location: United States
Esquire
Thanks Wayne. I've been educating myself about horns by reading all of your white papers before I order the parts. Lot's to learn for sure.
BTW, what type of horn is yours? And what does putting the 0.47 cap across the HF terminals do instead of in series with it and paralleled with the resistor?
Wayne Parham Messages: 18792 Registered: January 2001
Illuminati (33rd Degree)
The H290C horn I use has an oblate spheroidal flare profile, something often called a waveguide these days. It provides constant beamwidth, smooth response and minimum wavefront distortion.
The R1/R2/C1 network is used to tailor response for compression drivers on constant directivity horns. See the following links for more information:
tejaus Messages: 6 Registered: August 2012 Location: United States
Esquire
Well, I tried the 16ohm x 16ohm combo with a 0.47uF bypass across R1. Sounded OK but still didn't sound great although less output and less harshness on vocals.
I then tried just placing the 0.47uF cap across the tweeter as shown in red in the stock schematic below without using a R1 resistor. Just used the stock 15 ohm dampner.
What a huge difference that made to the midrange. The vocals are some much clearer now. What exactly does this do?
I have to get some more resistors to try the attenuation at -6db and -3 db. Any harm running it as is without R1 in circuit?
Wayne Parham Messages: 18792 Registered: January 2001
Illuminati (33rd Degree)
If I understand what you're saying, you now just have a 15Ω resistor and 0.47uF capacitor across the tweeter. If that's what you have, it will slightly reduce the load impedance, causing the circuit to be slightly overdamped. This will reduce output around the crossover frequency, but just slightly. A 15Ω resistor across an 8Ω tweeter doesn't make a huge difference. The 0.47uF capacitor will shunt some of the top octave, and reduce the output above 10kHz just a smidge.
tejaus Messages: 6 Registered: August 2012 Location: United States
Esquire
Yes, you're correct about the wiring.
With that cap across the tweeter it reminds me of how a aural exciter changes the sound. It seems more then just a change in frequency response. I'll know more later after I fix the power supply caps in my Behringer DSP-8024. I'll run the RTA on it.
I wonder what effect would a smaller or larger cap have? Say up to
1.0uf down to 0.22uf.
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