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Horn in Ampeg SVT-210HE cutting out for no obvious reason?

Discussion in 'Amps and Cabs [BG]' started by AlexanderB, Jan 18, 2012.


  1. AlexanderB

    AlexanderB

    Feb 25, 2007
    Sweden
    I occasionally use an Ampeg SVT-210HE on top of my SVT-410HLF to get speakers up closer to my ear and I have noticed that the horn sometimes goes quiet. Having checked a number of things I still have not found any obvious explanation to the problem...

    It does not take very high SPL for the cut out to happen, even if it has not yet happened at "living room level". Over 90-ish dB and all bets are off, though. When the horn is functional it sounds just as it is supposed to - no noises or distortion. I did take the horn and driver unit apart and the voice coil and its protective laquer looks fine to the naked eye. (So there should be no shorting aganst the magnet assembly.)

    The connectors on the crossover are OK and so are the wires. I also opened the Lpad and found no visible damage.
    No corrosion on the light bulb and holder. The lamp was labelled as 28V + a number that I do not remember.

    It could be worth mentioning that I run the horn padded down about 8-10 dB. (Basically only 25-30% up on the Lpad's range.) I do not know if the problem persists at higher horn settings.

    Any suggestions?
     
  2. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    It's either the tweeter or the crossover. Tweeters are cheap, though...you could easily get a replacement for it and try it and you wouldn't be out a buttload of scratch.
     
  3. RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    +1 and I'd just add, (though it may not matter), that the 410hlf is 4 ohms, and the 210he is 8 ohms, so your amp needs to be stable below 4 ohms, (2.67 ohms) Most are not.
     
  4. AlexanderB

    AlexanderB

    Feb 25, 2007
    Sweden
    Going back to post how it resolved:
    The 210 has not been used a lot. When used, I have often put it on top of the 410, running each box from a separate channel on my stereo power amp.
    Then it dawned on me, that when I used the 210 alone, powered by my LMII, there was no problem...

    It turned out the patch cable from my rack pre to rack power was gradually failing! The vibration at higher SPL would rattle the rack enough to cut all high frequencies out from the amp channel powering my 210. Funnily, it retained lows, now in hindsight, I think that there might have been a bit of SPL loss in the remaining lows, though?

    The problem has never manifested since I changed the patch cable.
     
    Last edited: Jul 4, 2014
  5. Steve Dallman

    Steve Dallman Supporting Member

    Is there a small component that looks like a small ceramic disc cap? It would likely be in parallel with the lamp, possibly in series with a 2 ohm resistor.

    Some crossovers use a poly switch. It will open up if hit too hard, and at that point the lamp takes over. If this crossover has the polyswitch, you may be hearing the switch open up and the lamp taking the horn much lower.
     
    AlexanderB likes this.
  6. AlexanderB

    AlexanderB

    Feb 25, 2007
    Sweden
    Thanks, Steve but as I wrote in the recent post, the issue definitely seems solved with the new patch cable.
    I still appreciate your clear and helpful reply!

    By the way, I had that type of protection in my Cerwin Vega home speakers I had as a teenager. It worked quite well...
     
  7. From the grave.
    How how about cutting In and out. When playing When it’s turned all the way down? Crossover or connection. I’m stumped.
     
  8. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    It appears to be an intermittent connection. The circuit is fairly simple. The first thing to check that all the connectors are tight, including the ones at the tweeter. It could be a failing horn. Then inspect the crossover. Check the lamp connection. Sometimes vibrations within the cab can cause things to break.


     
    dropbass likes this.
  9. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I’d replace the lamp. Sometimes the filament can fail but still touch enough to complete the circuit. Vibration would cause such a failure to open and close randomly.
     
    dropbass likes this.
  10. AlexanderB

    AlexanderB

    Feb 25, 2007
    Sweden
    The internal wiring is connected with Molex connectors on the crossover. There might be an intermittent problem due to oxide or a loose sleeve. These cabs might be approaching 20 years now...
     
    dropbass likes this.

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