Discussion in 'Amps and Cabs [BG]' started by DougP, Jun 22, 2004.

  1. DougP


    Sep 4, 2001
    i was at a show the other night and the bassist was running through an Eden 2x10 combo. he was setting up with his back to the amp and he was plugging in his pedals. while doing this there came some horrible line noise/feedback from his amp...yeah it was on while he was plugging everything up. but anyways, as i was watching and all this noise was occuring, his speakers lit up. the fabric ring portion around the speakers ( i dont know the technical term for it) lit up like there was a fire inside of the cabinet.

    what causes this? i have never seen it before. i assume it is detrimental to the speakers that this happened...
  2. heat + fuel + oxygen = fire

    in this case there must have been enough heat inside his speakers to light up whatever coating there was on the surrounds (glossary word of the day, kids) of his speakers.

    he serves as a visual reminder to always plug your signal chain into the amp last.

  3. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    It's the bulb that acts (depending on how much power it's seeing) as a compressor/limiter/fuse to protect the high frequency horn from excess power. If the bulb didn't blow then the cab will be fine and sound the same. If it did blow, then the bassist will have had not output from the tweeter (i.e. a lack of highs) for that gig, but afterwards it's easy to replace the bulb and then all will be back to normal.

    It does look cool doesn't it?!!

    The bulbs used to light up and often blow in my Acme B2s. Since going from giving each 425W (Mackie M1400) to 900W (QSC PLX 3002) they've never even lit up, let alone blown. Just shows how much extra high end amps put out when they're clipping/riding the limiters.

  4. Some speaker cabinets have horns or tweeters that have a crossover. These crossovers have protection circuits. The protection circuits are sometimes small lightbulbs - mostly automotive lamp bulbs...fairly common. When the crossover is being overtaxed, the bulb will light, indicating it's doing its job. If the bulb fails, the crossover is protected and you don't blow your tweeter or horn. All you have to do is replace the bulb and your back in business.

    No fire, just a cool light show.
  5. Stinsok

    Stinsok Supporting Member

    Dec 16, 2002
    Central Alabama
    At one of my kid's PTA meetings the A/V geeks were setting up the PA. I didn't see what they did but there was a huge noise that I can't describe. I just happen to be looking at the speakers when it happened and saw the things light up through the ports. After that 2000db noise I was certain the speakers where toast. To my suprise they worked just fine.
  6. Damn, Alex, beat me by 2 minutes.
  7. DougP


    Sep 4, 2001
    indeed it looked cool. makes me think it would be cool to put a light in there that reacts to your playing and shines through the surround (see, i'm learning here LOL). of course this has probably already been done.

    he did indeed play the show with his amp but i noticed he was also looking at it strangely shortly afterwards and tweaking knobs like a madman.

    thanks for the info everyone