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KLH 5 - Uneven Bass Balance and Speaker Impedance NEED HELP


thr33p4c

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Gentlemen,

-Model Fives - All new Caps and Resistors on Boards - Running fine for almost 9 months...

I have been noticing lately that my Model Fives have sounded a bit off. One of the speakers appeared to be lacking bass. At first I assumed it was related to a new preamp that I had put in. I swapped my pre and the problem persisted. I swapped the speaker wires between speakers and the problem did not follow. After this, I was convinced the problem was with the speakers themselves. I measured impedance on both speakers, disconnected. The one that sounded correct measured at about 4ohm, that is what I am used to seeing on my updated XO boards. The problem speaker measured at about 8ohm! They used to be identical.

I pulled the woofers. Both measured at 3.9 ish. The series mids both around 14ohm. The tweets also both around 4ohm. I measured all resistors and caps in circuit and they are reading the same on both boards. With the woofers out, I twisted the woofer positive with its negative to get that part of the circuit back to the terminals. I measured impedance again and found .3ohm on the good speaker and 5ohm on the problem speaker.

I think I have something going on in that crossover that is adding resistance to the circuit causing that speaker to sound noticeably less bassy. I cannot track it down. All I can think of is a bad, shorted inductor or something wrong with the switches. I tried the switches in all positions on my last test and the reading stayed at 5ohm...

Any ideas?

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  • 2 weeks later...

The boards are Identical. The one that failed had been working fine for months. I think a component may have failed during a spike. I recently changed my preamplifer and it has no power up delay relay. I turned it on out of order a couple times and it sent a nasty pop through the speakers. I am starting to think more and more that this was the root of my issue. When I get a moment I will disconnect the inductors and check for continuity at least. If I don't find an issue there I will start isolating other components.

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I did some testing on my trouble board today. I found something very strange and am looking for a second opinion. Basically what I have seen is an increase in overall crossover resistance. With my speaker leads shorted together (Tweeter + , mid +, and woofer + shorted to ground) I usually see about .3ohm. I confirmed this on an untouched board. My trouble board measures close to 4ohm. All things equal. I have discovered through trial and error that if I move my woofer (+) lead to an alternate grounding point the overall XO resistance drops to a normal range. I can touch on any other terminal strip ground point or anywhere on the chassis but as soon as I touch the wires to the terminal tie down point normally used for the woofer I see the jump in resistance. Is it possible that this piece of metal has somehow developed a resistance? It is so odd. NOTE - This point is normally shared with an inductor but I removed the inductor lead and did this test with that lead unattached and grounded to an alternate point on the chassis. I always see the same result. Added resistance on normal tie down point. Normal resistance on any other chassis ground.

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