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No continuity on 1993 Model K Horn


specauto

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Greetings:

 

This is my first post to the forum, although I've had my horns since 1998, this is the first problem I've ever had.

Here is my situation:

 

I have one horn that has lost all the low and seemingly some of the midrange. Stock 1993 with factory AK-3 crossover. The mid horn and tweeter horn are producing sound, but all upper range frequency.

 

Here's what I've done: 

 

Checked the fuses, swapped the fuses, no change

Checked all wiring, cabinet and speaker to amp, no visible issues

They are powered by monoblock amps, swapped those, no change, both amps work other horn fine

Pulled the side panel out to see if there was any visible issue inside the bass cabinet (like mouse nest) looks brand new inside

Put meter on both set of lugs. upper and lower, zero continuity on either set of lugs, but the upper horns are at least somewhat working. tried the same on the good speaker and both of my Cornwalls I have set up beside them. All three of the other speakers, including both set of lugs on the good horn, all all showing 4.2-4.5 ohms of resistance.

Put meter directly on the woofer, zero continuity.

 

I'm  not sure how the horns should sound with the bottom end completely non functional. But there must be something wrong with the upper crossover/horns as well, otherwise they should show that 4ohm resistance the good one shows?

 

Any help you folks could provide would be appreciated.

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In this order, isolate the problem:

 

Inspect the cabinets for defects or leaks.

 

Try reversing the speaker wires LR RL

If the problem moves, it's the amp, pre amp or source

 

Eliminate the crossovers

Disconnect and test OHMs  for each driver and write down the numbers

Driver numbers should be nearly identical by type, tweeter, woofer, mid horn

 

Remove and swap the crossovers, and see if the problem moves with the crossover

If the problem is in the crossovers, test each component and write down the numbers.

Or just throw new crossover in .........

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17 hours ago, specauto said:
17 hours ago, specauto said:

Put meter directly on the woofer, zero continuity.

 

Sounds like the woofer is blown to me.

 

17 hours ago, specauto said:
17 hours ago, specauto said:

But there must be something wrong with the upper crossover/horns as well, otherwise they should show that 4ohm resistance the good one shows?

 

 

Since the upper crossover passes through a 13uf capacitor, it will never show dc resistance, since a capacitor is by definition an open circuit.

 

The 4 - 5 ohm readings you are getting on the good speaker is the sum of the resistances of the woofer and series inductor, no matter which speaker terminals you are connected to.

 

Edit:  Forgot that the tweeter circuit is isolated in this crossover, so the 2uf capacitors also create an open circuit.

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On 8/7/2022 at 12:26 PM, Bubo said:

Remove and swap the crossovers, and see if the problem moves with the crossover

 

Good advice but no easy feat since every connection is soldered, both at the network end and the driver end.

 

All of these should be rewired using clean wire and disconnects.

 

 

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8 hours ago, DizRotus said:

I suggest getting both woofers re-coned or replaced.  On the recommendation of Claude, @ClaudeJ1, I had both EV woofers in my HIPs re-coned locally.  If you’re not lucky enough to get a similar recommendation, ask local professional guitar players for recommendations.

Excellent advice!

 

Make sure you insist on OEM parts from EV. The aluminum voice coil's lower mass coupled with a light cone and big magnet is what gives the driver that little bit of extra "resolution" that favors the midrange over the bass. The bass portion is provided by the box down to the point where you should be using a subwoofer to get full music bandwidth into the high 20's anyhow.

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