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Major Problem W/ Ampeg PR-410 Cab! HELP

Discussion in 'Amps and Cabs [BG]' started by patrickshofner, Sep 7, 2005.


  1. Ok guys/gals....
    Today i go to practice, assemble my rig as always, start to jam and i immediately knew it was a bad day. My cab is totally farting when i hit lower notes. on my top string (c#in my case), like all the way up to the 10th fret, the low end is just shot. I dont know whats caused it. I mean i only have a 350w amp and i believe these are rated at 1200 watts so i wouldnt believe a speaker to be blown. Any help/info you could give would be great. I'm going back to the practice spot to start a disassemble and explore a bit. Please help me out.....i'm in desperate need. haha TIA
     

  2. There ya go. One or more drivers are probably blown. Clipping a small amp into big cabs is a bad thing for speakers and all living creatures.
     
  3. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    Do you have an active bass, and if so have you changed the battery recently ?
     
  4. wow.....news to me. I was unaware of this. The person i bought it from (a touring musician) told me it would be fine. oh well

    if it is a driver, what are my options?

    and my bass is passive
     
  5. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    blah blah blah you're underpowered blah blah blah your cab was toast the minute you put a too small amp through it blah blah blah get a 4,000 watt power amp so you won't blow speakers even though it defies logic blah blah blah.





    :rolleyes:
     
  6. wow.....umm i'm sorry if i've offended anyone with my ignorance, but to be honest i've only been playing a short time and no one's ever notified me that this was a major no no. My purchases have been finance based, and i thought i was getting good deals on compatible gear. i guess not.

    so now that we've established that i'm a total noob and have screwed up my cab, how can i go about fixing it?
     
  7. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    If you've actually blown a driver and want to do it right, you'll contact Ampeg and get an original replacement speaker.

    If you listen carefully close up you may be able to determine which one is fried (but it may be more than one).

    It may have just died from previous abuse. You can destroy just about any speaker if you work at it hard enough. The bass EQ on an amp or bass that can be pretty mean to speakers when you deviate from flat setttings.
     
  8. thanks.....like i said, tomorrow is the real inspection time and i'm fearing the worse. I dont understand how there's been no indications of anything odd, and then today its totally shot. but oh well i guess things like this happen. thank you for your help
     
  9. BassIan

    BassIan Supporting Member

    Apr 27, 2003
    Cupertino, California
    Don't worry. You haven't offended anyone. There exist two camps on this board regarding matching of power between amplifiers and speaker cabinets. In very general terms, some believe that the power amplifier should have more power (double or more) than the cabinets, and others believe that the cabinets should be able to handle more RMS power than the amplifier can generate.

    Reality is, if your amplifier clips, it's bad for the amp. It can generate more power than its RMS rating, in some cases it can peak at double the RMS rating. What this means for your cabinet is that you *might* exceed its RMS power rating even if your amplifier is rated for slightly less power.

    Average music, including bass playing, will certainly not keep your amplifier generating its RMS rated power all the time. Even a LOUD mix or playing setup will average out to maybe 1/3 or 1/2 of the RMS power. That's if you're a BUSY player. For PA setups and often bass rigs, it is suggested to use more amplifier power than the cabinets are rated for to provide HEADROOM. This means your amplifier can provide a short burst of power, CLEANLY (no clipping), to adequately reproduce transients. This is very dependant on setup of your system, and is assuming your amplifier stays clean. A clean peak from a 1200W RMS amplifier will generate, at that instant, 1200W of instantaneous power at a maximum before clipping commences. I am disregarding the effects of short transients allowing slightly higher current from the power supply for simplicity. If your cabinet, the PR-410 HLF is rated at 600W RMS, and 1200W peak, it can certainly handle clean peaks from the amplifier. It cannot handle a clipped signal from that 1200W amp. The hope is that you'd never need to drive the amp into clipping, since anything powered by 1200W is REALLY LOUD!

    Regardless, it sounds more to me like your amp is clipping. You should perhaps rent or try a different (more powerful) head for your next practice and see if that solves anything. The PR-410 HLF is not a very sensitive cabinet, so it will require a lot of power to go as loud as you may like relative to other more sensitive cabinets.

    Hopefully this is helpful.
     
  10. Thank you VERY much for that helpful and very informative post. People like you are what keeps newbies like me coming here for great info and help. once again, thanks
     
  11. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA

    The reason you can blow a 500w cab with a 350w amp is because of the heat generated in the coil from the speaker trying to keep up with trying to recreate the distortion being put out by a 350w head being pushed too far (power amp distortion. good for guitars, bad for bass). You need to listen for the distortion. It is not like the distortion 'effect' which is basically preamp distortion. It is an ugly, raspy sound...alot like dry farts. If you hear it, turn down 'til you don't. If that is not loud enough it's time to get new gear.

    If you run 4000w through a 500w cab continuously you will fry the cab basically by making it work beyond it's means.

    However if you power a 500w cab with a 4000w amp but only use enough power to run the cab at the volume needed (up to max rms), providing that it is within spec of the amp, the extra power is used to keep any spikes clean and distortion free and will not hurt your cab as long as it is within the peak spec of the cab and keeps your tone squeaky clean. Just the way it should be.

    Simple and logical.

    :D

    Joe.

    p.s. If you contnuously clip a 100w power amp into a 1000w cab I doubt you will blow anything. But 350w clipped into a 1000w cab is approaching the danger zone, I am sure.
     
  12. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    I concur with all the above, but I would with a minor disclaimer.

    These days many basses, and almost all amps of much size have active EQ; that is, they cut AND boost signal as they deviate from the center position. It isn't very difficult to crank up an additional 10db of bass boost, which can suck your amp dry of any additional headroom you may have started with.

    It is indeed a great forum with lots of expertise for the asking.
     
  13. The Ox is just having one of his spells again. We just ignore him when he gets like this.

    There is indeed two "camps" as BassIan mentioned, those who believe that the power amplifier should have more power than the cabinets, and those who believe that the cabinets should be able to handle more RMS power than the amplifier can generate, but in the end it doesn't matter which camp you're in. The fact of the matter is that you need enough amp to do the job you're asking it to do or you're going to end up pushing it too hard, causing it to clip and you're going to take out some drivers in the process.

    A 350 watt head is a lot of power, but under certain circumstances it's not nearly enough. Hook it up to a power hungry cab like the PR-410, boost the low end on the EQ and you're going to run out of power very quickly. Anybody who has used a 96db@1w cab like the PR-410 will testify that 350 watts is only a fraction of the power you should have for a cab like that. You really should be hitting that cab with a 1 kilowatt amp or better.
     
  14. BassIan

    BassIan Supporting Member

    Apr 27, 2003
    Cupertino, California
    Glad I could help you out. Feel free of course if you come up with more questions.

    I hope you're enjoying that cabinet. I owned one for awhile and found it quite good. I'm a freak so I need new stuff every once in awhile, though. :help: :p
     
  15. well today i checked it out and luckily nothing is blown, but i'm on the way to hunt down a power amp already. haha all of you guys were very helpful and i'm psyched that its just a situation of under-power and not blown speakers.
     
  16. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    This is the same logic that dictates one cannot kill a 10,000 pound elephant unless one conks it over the noggin with a 10,001 pound rock. Personally I'll stick with a .458 Weatherby. Now, for a logical scientific explanation of how one may successfully toast a large speaker with a small amp read this:
    http://www.rane.com/note128.html
    Audio engineering isn't based on logic, it's based upon scientific principles that more often than not prove what seems logical is wrong.
     
  17. MrBonex

    MrBonex

    Jan 2, 2004
    New Hampshire
    I was just going to explain why clipping causes speaker failure when BFM posted that excellent Rane link.

    My explaination is pretty simple and a little less scientific (I think) --

    If a speaker has to generate a square wave (clipped waveform), the cone must HOLD in the "out" or "in" position for the duration of the flat top/bottom of that wave. The lower the frequency, the longer it needs to hold -- because of the length of the wave (low frequencies are larger waves than high frequencies). While the speaker is holding, it gets HOT because it's not moving. The more clipping, the more heat, etc., etc.
     
  18. TheChariot

    TheChariot

    Jul 6, 2004
    Boston, MA
    If you've noticed the peak LED lighting up a whole lot, or if you've heard previous distortion... then you may have clipped the amp and simply fried out a driver or two.

    How much have you cranked it and what kind of volume are you competing against in your band? I'm not saying that you purchased "bad" equipment.... in fact, I really like the PR-410 cab myself.... but you might be demanding too much from 350 Ampeg Watts.

    Hopefully there's nothing wrong with your cab and it was just a fluke. If you picked up both pieces used... I recommend reselling at LEAST the head and start looking for something with some more headroom. If you sell the head and cab, you'd probably have the money to get a pre-power rig used and an Avatar cab... and hopefully another one in the future. If pre-power isnt your thing, maybe look into a used GK or something of that nature.

    And remember this, if anything: Cone surface will give you much more volume than more power. So maybe if you kept your B2R, but switched your cabs to a 4x10 + 1x15 setup or something of that nature.... you'd be satisfied. However, you'd need 8ohm cabs for this.
     
  19. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    But if you read that Rane paper, you would see that it does not maintain that clipping, in and of itself, inevitably causes speaker damage. What it does is explain a mechanism by which an amp, in a state of clipping, can damage a cabinet whose rated power handling is higher than the amp's rated output. Actually, he's talking almost entirely about tweeters. This mechanism is a type of compression that results in delivery of too much power to the tweeter. In other words, the culprit is not the square wave per se; it's the higher average power, with the shape of the wave being irrelevant. You might burn out a tweeter with a high level of perfectly clean power. Or you could clip a tiny amp to death and be very unlikely to harm the tweeter.

    And the holding of the cone apparently is something that doesn't really happen that way, because interia doesn't allow it to. Mark Reccord has done some experiements on this.
     
  20. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Well, there's a third camp--those who believe that the point is not the relation between the amp power and the cab rating either way, but rather the relation between the power needed and the power available. The idea is that you want more than enough amp to get the volume and tone you need, and after that, whether the cab handles more power than the amp can deliver or less *doesn't matter, as long as the cab can handle at least the level of power that you're actually using* (which will be less than the amp's rated maximum, if you've bought an appropriately big amp).

    I think this is kind of what you're getting at in the last sentence, so welcome to the camp.;)