In Reply to: Wayne and crossover guys; a little help? posted by Till E. on January 16, 2003 at 16:21:00:
For 811's, I would use the 1K6a008dB crossover, exactly as shown on the π crossover schematic, because this is the response curve you can expect to get with a PSD2002:Altec 811 with Eminence PSD2002 using π 1K6a008dB crossover
As you can see from the chart, on-axis response is nearly perfect. Probably as perfect as you can get from a 1" compression device on a horn, really. You can also see that 6kHz to 14kHz is up 2dB from the 1kHz to 6kHz level, so you could use a 1K6a006dB crossover and expect excellent results. If you must use more attenuation, such as is provided by the 10, 12 or 14dB units, then you will probably want to use a slightly smaller value for C1. I expect that 0.22uF or 0.33uF will be better than 0.47uF on the Altec horns using the PSD2002. Then again, with other compresison horns, you might want to leave capacitor C1 as it is.
When moving to the 800Hz crossover, compensation begins earlier. I see that you're using an Altec compression driver, so we can discuss this frequency for them. But I want to remind everyone that I wouldn't recommend an 800Hz crossover point with the Eminence PSD2002.
The 800Hz π crossover is optimized for horns designed to mount 2" compresion devices and tuned a little differently. I understand that you don't want to use Spice, but it would really be great - Just a little bit of "tweaking" on the drawing board would put you right in the driver's seat. But if you want to do a "seat of the pants" thing, my gut feel is that you'll want to use the 800a009db or 800a012db crossover for the 806 on 811, and I think you can expect acceptable results using a C1 value that's 1/3rd to 1/4th the size of what's shown on the chart for the 800a009db or 800a012db crossover schematics. I also think that I'd leave all the other component values and their configuration in the circuit as shown on the schematic and value charts.
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