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Acme B4 emitting smoke??

Discussion in 'Amps and Cabs [BG]' started by MacheteJames, Aug 5, 2004.

  1. OK so here's the situation. I just got an Acme B4 2 nights ago. I go it used, off of a fellow Talkbass member. I used it tonight for the first time... it sounded fantastic... that is, until I engaged the "bright" switch on my BBE Bmax preamp, which promptly caused the tweeter protection bulb to burn out. OK, no big deal, right? This happened halfway through a song, so I finished the song with no tweeter. I'm getting ready to take off the grille and speaker, and someone says "I smell smoke"... the smoke odor is coming out of the Acme! After taking the grille off and a speaker out, I see that everything inside of the Acme is fine, the bulb is just burnt out.

    Is it normal for this to happen? I'll be more careful in the amount of highs I send into the Acme from now on, but I don't want to freak out the rest of my band by playing a cabinet that smells like it's about to go up in flames. Is there any way to keep this from happening again? I'm sending about 1800 watts into it, through a QSC RMX 1850HD, but I don't have the gain cranked at all. It really does sound good, but this has me concerned..

    One last thing.. do I need to replace the gasket on the speaker that I removed?

  2. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    It's never good to let the smoke out of a B4. It voids your warranty.
  3. embellisher

    embellisher Holy Ghost filled Bass Player Supporting Member

    I've always heard that those were smokin' cabs. Never had the pleasure of meeting one in real life.
  4. martens-koop


    Oct 10, 2002
    I've had my speakers out a bunch of times and have not replaced the gasket. (low b2) I'd assume that the only reason you would have to replace the gasket is if it got squished TOO flat and was no longer spongy enough to fulfill the teleological function, thereby failing in its "gasketness".

    never heard of smoke coming out of cabinets... it sounds fishy though.... get a flashlight and have a good look inside for burnspots on your crossover channel... those bulbs are sealed up, so smoke shouldn't (couldn't?) come out of them..

    someone on a similar thread mentioned going to a motorcycle (harley) dealership and buying one of their bulbs. He figured that the Harley motorcycle bulbs stood up to the vibration better...

    sounds like a great idea to me, but the dealership wasn't open the night I needed a bulb, so I just got a regular pack for about $2.00

  5. That's a lot of watts into a single cab. Most folks think double the rated watts is enough headroom and some say even 50% over is enough. Note that the "volume" knob on modern power amps simply attenuates the input from the preamp, it does not limit the power of the amp. So, when you hit the bright switch on your pre you are overcoming this attenuation for whatever frequencies the bright switch boosts. BAM! Waaay too much power.

    Couple of things to try. I suspect the smell was the pad heating up before the bulb blew. The balanced (flat) setting of the cab's pads are at approx. 3 o'clock. Try putting your mid and tweeter controls on the cab are all the way up (clockwise, no attenuation). This may sound a little bright initially, but may keep you from having to hit that "bright switch". You can always roll off a little treble on your bass.

    To be absoulutely safe, you could run just one channel of the amp into the cab (600 watts, the cab's rated capability), or put a limiter in the signal chain before the amp. I run a 1,000 watts into my B-2, but always have a limiter or compressor in line.

  6. I should have had the BMax's compressor on, but I didn't. I bet that's what triggered it. It's a pretty hot preamp to begin with, so I should have been more careful, especially with the amount of wattage I'm dumping in to the Acme. I'll make sure I run compression from now on. Thanx everyone, for your advice :)
  7. r379


    Jul 28, 2004
    Dallas, Texas
    Have you called Andy Lewis (I think that's his name) at Acme? He's supposed to be a pretty nice guy. I'd call him and see what he has to say.
  8. It's a Series One. It looks like it's kind of old.. it's the only Acme that I've seen that has only 1/4" inputs, no Speakon input.
  9. bigbajo60


    Nov 7, 2003
    Laredo, Texas
    Yeah... I sold my original Acme Series I B4 to a "youngster" who proceeded to turn down the Hi & Mid attenuators down all the way, but then crank the highs and mids on his 1,000 watt amp... burned out the attenuators and got the fiberglass batting to smoke a bit as well from the heat.

    Best thing to do with a Series I Acme is to keep the attenuators wide open and then control your highs and mids from the amp. At least that's the way I seem to remember Andy Lewis suggesting it. :D
  10. martens-koop


    Oct 10, 2002
    I second the opinion of wide open on the attenuators... why send all of that good tone to ground? you've generally got a lot better tone options and control at the amp anyways...

    (occassionally when I hook my B2 up to the Sub out on my DVD player, I will put the attenuators up a little (just to emphasize the "bassiness" during real big explosions...

    !!! jmk
  11. I want 4 Low B-1's as surround sound, a Low B-2 as my center channel, and a Low B-2W as my sub. Power it with a PLX 3402 and I believe I'd have the best sounding home theater ever. Bose, Boston, and Polk would have NOTHING on me.
  12. ster


    Oct 18, 2003
    New Jersey
  13. martens-koop


    Oct 10, 2002
    I'm not certain about your PLX power amp, but wouldn't you need three 2 channel power amps to run the setup you describe?

    I agree though... that would be one awesome sounding home theatre system.
  14. I just replaced the bulb, I'll find out tomorrow if everything is okay, since my rack is at our practice space.. I'm a little worried about the attenuators, I'm gonna run them wide open from now on...
    *fingers crossed*
  15. notanaggie

    notanaggie Guest

    Sep 30, 2003
    Could be attenuator, of course.

    I have also seen the bulb cook and even light the sound insulation inside the cab, if it can touch the bulb. Not all is fiberglass.

    If there is any nearby, see if its charred, and tear away any that is too close. you don't want a fire.
  16. Good news.. used it today with the new bulb in, it works perfectly.
    My band is recording its first album this weekend, and what's interesting is that the Acme sounds exactly like the DI signal... there was no reason to mic the Acme because the tone isn't really any different. The engineer who we are working with simply could not believe that such a gigantic sound came out of a 4x10... it really does sound like its got an invisible 2x18 cab hidden in it somewhere. :)
  17. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL
    dunno if this even compares, but i've used my B-1 pair as a PA for several gigs, and they've been great each time. for a recent BBQ, we had the Roots, Bob Marley, and a little Chingy slammin' thru 'em, and WOAH NELLY!

    course, in hindsight, dunno why i didnt bring my crossover and truck out my B4 as a sub! :rolleyes: :D

    but jimmy,

    glad to know it all worked out in the end. :cool:
  18. I seem to have blown the bulb again :meh:

    While it is easy enough to replace, I hope this isn't a sign of things to come. I wonder what could be causing it? I have the gain cranked on my BMax's semiparametric EQ... I have the gain knob at around 5 o'clock and the frequency set to 800hz. Could this cause it? It sounds soooo good that I'm almost willing to put up with it, as long as it doesn't happen in the middle of a gig. :(
  19. BruceWane


    Oct 31, 2002
    Houston, TX
    Yeah, heavy use of EQ could do it. You want to have your EQ as close to zero overall gain as possible. For example, let's say your current settings are bass +3, mids +7, highs -1......instead, you should set things at bass -2, mids +2, highs -6. You keep the same overall curve, but you keep the level as close to zero as possible.

    Most everyone using Acmes, myself included, find that setting eveything flat, then cutting frequencies to taste works very well. Rather than boosting your mids to overcome the low end of the cabinet, just cut some lows. You'll get the tone you want, plus you'll get a lot more headroom out of your power amp. And we all know that headroom is a very good thing, especially with Acmes.

    Also.......where did you get the replacement bulb for the protection circuit? A lot of people use automotive bulbs, since you can get them easily, but those bulbs really aren't the right voltage to use for this application. Auto bulbs are generally 12-14 volts; in an 8 ohm circuit, that translates to about 25 watts. In a 4 ohm circuit, 50 watts. So they will fit in the holder and get you by, but they're probably going to blow again very easily. I don't know for sure the voltage of the bulbs that Acme uses and recommends, but I'll bet it's more like 24 or 30 volts.
  20. bigbajo60


    Nov 7, 2003
    Laredo, Texas
    Just took delivery of a brand new B2 with all of its attendant manuals and documentation... Andy Lewis specifies an 1156 automotive bulb.

    I believe that someone mentioned a more rugged version of this bulb is available at Harley-Davidson (or similar) dealerships.