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Go back to your speaker design. What is your crossover circuit? I've reviewed your build thread without seeing anything but a request for your XO simulation (post 3). I'm looking for a schematic with all connections back to the amp. You mention a PR shelf filter, a useful component but not something that would act as a crossover.

What you describe sounds a lot like a tweeter running full range, making tons of harmonic distortion below where it should reasonably cross. Being harmonics, distortion ends up as highs; 2K HD occurs at 4K, 6K, 8K,10K, etc. and the odd harmonics are typically judged to be grating on the ear.

Have fun,
Frank
 

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My apologies, I misread your build thread; no mention of a shelf filter, just the 3.5KHz PE XO. Pre-built XO's have significant performance issues (not rational to design the peg before you've seen the hole), but not as severe as the problems you describe.

Any chance there's a level mismatch between your Mac output and the APA's input levels? Are you using a line-level output from you Mac? Headphone jacks are not low-level outputs; you could be overdriving the amp inputs.

Hang on... shelf filter comments are in this thread, post 1:
"PE shelf 3500hz crossover between the amp and tweets/mids." or should this read PE "off the shelf" 3500Hz XO?

Do you know what driver impendence this XO assumes? If it's for 8 ohm and you're using 4 ohm, your XO frequency is half what you think it is and the tweets are screaming with HD like I thought they might. How are your multiple drivers wired together? Drivers have a DC resistance you can measure with am ohm-meter. The XO sees a highly variable load with frequency (4-50 ohms) that's only grossly related to the DCR. How you arrange them is critical to the final impendence seen by the XO, and thus critical to the XO frequency.

Let me ask again, please show us a circuit diagram for your connections. I don't care if you scan a pencil sketch, give us a picture so the words aren't in the way.

Have fun,
Frank
 
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