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Heresy Crossover Mod - Less Bright


JohnA

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I made this mod years ago. Recently, I swap out the K22 and put in a pair of JBL 123a with the same modded crossover. Been listening over 2 weeks with very positive impression. Faster, punchier, better transcient. If you have a pair of spare 123a, I would strongly suggest to try them on your Heresies. Just my 2 cents :-)

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Interesting switch... I don't believe the 123As will handle as much power. I still have mine in my 4311s and have plugged the ports, but I'm going to undo that and have a listen again.

 

Bruce

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JBL recommended using an amp no larger than 150W on the L-100 (123A).

 

Puking a 123A was usually done with an amp lacking an infrasonic filter and playing records, not excessive power per se.

 

I designed and sold a $30 30hz filter (for the tape loop)  that virtually eliminated such failures (and made things sound better, and allowed you to play louder too).

 

JBL sent their vice-president out to visit our store to see what we were doing. We were also the world largest Harman Kardon ST-7 turntable dealer, in addition to having the lowest driver failure rates on JBL speakers (due to the filter and using fuses).

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"Would love to protect these. Got any of the filters left? "

 

A key part in the filter (17.5H inductor) was obtained on a surplus basis, and is no longer available. IIRC, about 100 were all that was built. They were about 5KΩ impedance, I built some 600Ω versions but they sounded opaque (as Crown preamps couldn't really drive 600Ω and still sound good).

 

P500?

 

Should be OK, we sold the P300 (back in the day).

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