Electro-Voice Sentry II Speaker Issues

[RSMRecording]

I recently purchased 3 early 1960's Electro-Voice model Sentry II monitor speakers and I am having issues with the tweeters cutting in and out. Each cabinet has a EV SP12B and EV T35B tweeter with a crossover. I originally figured the tweeters where blown, but after playing one of the speakers for an hour the tweeter kick in and the its sounded amazing and then it cut out again.

I am not sure what the issue is or how to fix it. Hope someone can help out and point me in the right direction

Thanks,

Robert

 

[dc270]

You are loosing BOTH tweeters at rhe same time correcy? I would hook up another amp and play them. If it happens again them look at the amp. If one of the tweeters die out look at your network and perhaps driver.....
DC

 

[GordonW]

Does the cabinet have a tweeter level control (knob)?

If so, that's the first suspect, IME. Probably needs to be cleaned internally.

Regards,
Gordon.

 

[RSMRecording]

Thanks for the responses,

The speaker cabinets don't have a level control for tweeters. I have now tried 3 different amps (Old Pioneer receive, Crown D-45, and old 45watt amp) all with the same issue. The tweeter comes in for a few minutes and then out again for several songs and then back again.

Each Cabinet has a Electro-Voice SP12B and T35B with a crossover. The crossover has several terminals on the back side (600 ohms, 150 ohms, 16 ohms, com), and I have them hookup to the 16 ohms and com terminals.

 

[RSMRecording]

 

[HyKlas]

Even looking at the schematic below, I'm not understanding what the unmarked terminal is for. Have you tried removing the strap going from the unmarked to 150Ω terminals?


https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.electrovoice.com/downloadfile.php?i=971893&ved=0ahUKEwj-y8GPxfXRAhVS_WMKHWRoAGAQFggiMAE&usg=AFQjCNHJNH7b-HZyeBlezIWvwcvbdZwCsA&sig2=ROkZVS9GWdfLqmNBWOQTlQ

 

[GordonW]

Check the tweeter terminals themselves. I've had those where they had bad/corroded/loose connections.

Regards,
Gordon.

 

[RSMRecording]

Alright, I am going to unstrapped those terminals and see what happens. And I will check out the solder joints on the tweeters and crossovers to make sure there isn't any corrosion.

Thanks for the help

 

[RSMRecording]

Would the Electro Voice X36 crossover work in these boxes ? I have a pair of them and figured that they might work.

 

[RSMRecording]

Here are photos of the inside (crossover and speakers)

 

[RSMRecording]

Check the tweeter terminals themselves. I've had those where they had bad/corroded/loose connections.

Regards,
Gordon.

The terminals do not appear to be bad on these speakers.

 

[RSMRecording]

Update,

I made up some temp wiring and bypassed the Sentry II crossover and connected a Electro-Voice X36 crossover. The result is a great sounding speaker and the tweeter is working perfectly at least in one of the cabinets. So, I think the original crossover probably has issues with caps or something, so I will just remove the Sentry II crossovers and the use the X36 crossover.

Thanks for the help

 

[RSMRecording]

Update #2:

Tweeter just cut out after about 40 minutes of playing with the X36 crossover, so probably a issue with the Tweeter?

 

[HyKlas]

Done the wiggle test?

While playing some music, wiggle each wire, one end at a time, and see if something acts up. This is the mechanic in me talking, hunting for an intermittent open or short...

 

[gdmoore28]

My guess: the voice coil on the tweeter diaphragm is giving out. When it heats up, the voice coil disconnects itself; once it cools down, the voice coil re-aligns itself and you have temporary connection again. Over the last fifty-plus years of fiddling with this stuff, I've had this happen at least four times with compression drivers and at least one woofer.

The T35 diaphragm replacements are rather cheap. I'd install one and see if that solves the problem. If not, you've spent little money, have a spare diaphragm, and the search goes on.