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overkill or headroom?

Discussion in 'Amps and Cabs [BG]' started by soundoholic, Jun 12, 2003.

  1. Your safe, sane, and doing the right thing by adding some headroom.

    44 vote(s)
  2. So you like to play with fire?

    5 vote(s)
  1. I'm working on a rig right now and I haven't decided if I'm going to be using too much power.

    Pre- tech21
    power- stewart world 1.2 Bridge 8ohms700w 4Ohms1200w

    Cab- Swr 3 Jr 2x10 rated for 350 watts 8 ohms.

    I'm doing this because I'm thinking of adding another cab down the road.

    If you were wondering about the cabs down the line I was thinking another swr 2x10 and another stewart 1.2 and 2 acme low b2 2x10s. This way I can run a crossover.
  2. Get the 2.1 instead. More power, better cooling, better all around amp. jmho
  3. FunkySpoo

    FunkySpoo Supporting Member

    Feb 6, 2002
    Go for it. I'm puttig 1000 watts into a 500 watt cab. Just don't drive the cab to hard and you'll be fine.
  4. ZuluFunk

    ZuluFunk Supporting Member

    Apr 14, 2001
    Having power and using power are two different things.

    Like Rick said, just don't drive them too hard and you'll have a nice clean signal and run your cabs to their potential.

    I have a QSC RMX 2450 and I run it nowehere near peak.
  5. Boil


    May 27, 2003
    Sarasota, FL USA
    What about the opposite?

    A lower wattage amplifier paired up with a high wattage capable cabinet...

    Say, an Aguilar DB359 (200watts @ 4 or 8ohms/all tube) driving an AccuGroove Whappo Jr. (rated for 800watts @ 4ohms)...

    Would hate to damage either piece of equipment due to stupidity...

  6. NJL


    Apr 12, 2002
    San Antonio
    i use a QSC RMX1450 into an 8ohm Avatar 4x10, the amp is bridged - 900watts

    i don't come close to turning it up all the way, but if i wanted to - i could!!

    the bandleaders really like my sound, sometimes they think i need to turn it up.

    headroom is the way!
  7. FunkySpoo

    FunkySpoo Supporting Member

    Feb 6, 2002
    Well now you're talking about an all tube head and that's a new ballgame. If you put a 200 watt solid state head into an 800 watt cab then you'll have to crank that amp to get any volume out of it. Then you wind up clipping the amp which on a solid state amp sounds like butt, and you'll probably fry your cab. But an all tube head, when over driven, just gets all snarley and cool sounding and won't hurt the cab at all. Also a 200 all tube will probably be as loud as my 1000 watt solid state
  8. You should be fine as long as you don't run your amp flat out. Depending on the cab, you might be fine even then. If anything blows, it would probably be the tweeter. I doubt if you're much less likely to blow an 800 W cab with a 200 W tube amp than with a 200 W SS amp. First, tube amps clip just as much as SS, maybe more. Second, it isn't clipping that fries cabs, it's a state in which some component of the cab is getting more power than it can handle. This can happen with clipping, but it doesn't always (as guitarists know better than bassists), and it can happen without clipping. The most either 200 W amp will put out at max overdrive is 400 W, and you probably wouldn't get there unless you were being really dorky. Tweeters, however, usually are rated for less power than woofers, like maybe 75 or 100 W in a 600 to 800 W cab. But that's OK, 'cause the treble frequencies usually take up only around 10% of a musical signal. However, if you're cranking your amp so hard that you're putting out a couple hundred W into the trebles as wella s the lower freqs, you will probably fry that thing.

    Short answer: you should be just fine!
  9. NeedMoreBass

    NeedMoreBass unregistered

    Feb 14, 2003
    Sound like a nice rig but you might consider the Eden 2x10 XLT instead. 2 of those would be KILLER!!:bassist:
  10. Mcrelly


    Jun 16, 2003
    Minnesota, USA
    I've heard its easier to damage a speaker by UNDERPOWER than overpower. As far as I understand a speaker coil gets damaged by the movement of the coil not being in sync with the magnetic flux of a distorted or lower power signal. this lack of sync causes heat build up in the coil and can warp it. also a distorted signal could cause a speaker to move too far, but not have enough power to help the speaker remain within its excursion range and thus popping the coil out of the magnet or ripping the cone.

    can anyone else back me up here??

    conclusion: better to have more power than the speaker is rated for. just know what an overdriven speaker sounds like so you don't go too far! I've heard you should have twice as many watts as the total watts capacity of the cabs. I've got two 350w cabs, I should have 1400watts, but I have only 350! maybe thats why I have distortion before I get up to a volume thats reasonable??
  11. hr_bert


    Jun 5, 2003
    austria, linz
    how do you do the cabeling. i guess if you put 3 pieces of 8ohm cabinets "in a row" doesn't it result in 2ohm general impedance? as far as i know there are not so many amps which can run save in a "2 ohm" environment? i am not 100% sure but consider the whole impedance thing!!!
    so either buying a bigger amp which can easily operate in 2 ohm mode to run 3 or 4 cabinets "in a row"......
  12. No, in its common form this is basically a myth. Yes, an amp rated lower than a cab can in some settings damage a speaker, but by no means in all settings, and an amp rated higher than the speaker can definitely damage it as well, though again, not always. This subject has been discussed at great length numerous times in this forum. You could do a search on clipping and/or distortion, and note particularly the responses of Bob Lee, who is an engineer at QSC.

    My take is that the ratio of the amp output to the cab power handling, in and of itself, doesn't mean that much. The more important thing is the ratio of your amp's power to the volume requirement of your playing situation. The best piece of advice I ever got was first to get an amp that had more than enough power for my gig, so that I could always get the volume I needed without straining. If I could do the job with a 100 W amp, get at least a 300 W amp instead. Once you do that, it doesn't matter at all whether your cab is rated higher than your speaker or lower, as long as it can handle the level of power you customarily use. Once you have an amp big enough, you derive absolutely no additional benefit from having a cab with a power handling capacity less than the output of your amp--asuming equal efficiency, etc. If there's benefit to either side in that scenario, it's in having *more* power handling in the speaker--more protection if you get tempted to turn up the amp.

    Lower power, in and of itself, will never hurt a speaker.
  13. No, the reason you have distortion has nothing at all to do with the power ratings of your cabs. You would have it whether your cabs were 200 W or 400 W. You have distortion because you don't have a big enough amp for your playing situation. If you had 1400 W, and that was enough to get you the volume you needed, it wouldn't matter whether your cabs were rated at 700, 1400 or 2000 W.
  14. Mcrelly


    Jun 16, 2003
    Minnesota, USA
    Originally posted by Mcrelly

    I've got two 350w cabs, I should have 1400watts, but I have only 350! maybe thats why I have distortion before I get up to a volume thats reasonable??

    Sorry Richard, what I should have said was "I've got two 350w cabs, I should have a 1400watt AMPLIFIER, but I have only A 350 AMPLIFIER maybe thats why I have distortion before I get up to a volume/WATTAGE that I NEED??"

    sorry for the context problem.
  15. No problem, just trying to help. Nothing to be sorry for. The only point I was making was that the size amp you "should" have isn't really determined by the power handling of the cabs, at least not in the way it's often explained. IOW, if you need 1400 W, it's not at all because the 700 W worth of cabs are somehow demanding, "Give me twice my rating, dammit, or I'll clip your ass!" They're perfectly happy with 100 W if that's all the volume you need. There's really no such thing as underpowering a speaker; you can only be underpowered *for your gig*. If you need a 1400 W amp, it's because you want to play louder cleaner.
  16. Mcrelly


    Jun 16, 2003
    Minnesota, USA
    I also was not suggesting that 50 UNDISTORTED watts would ruin a 350w speaker, but I believe that someone who has say a 100w amp with a 100w 15" cab tries to get 150w or 200w out of the 100w amp and runs regularly ABOVE the amps UNDISTORTED capacity, THEN they will probably heat up the coils and warp them.

    the guy who only needs 20watts into a 100w speaker and has a 100w amp in NOT going to ruin their speakers.

    The "amp rated at twice your cabs capacity" is more a rule-of-thumb that I heard because usually young/new/loud/volume hungry players can't seem to get enough volume. I know I just revealed some of my tendencies, but I know, from time to time, I don't have enough volume/watts.

    I was just thinking of this the other day and I know this is not really simple to assess. I wish there was a meter, like a Db meter that I could attach to my amp outputs that tells me "you're using 143watts right now" I'm assuming this is not as easy as it would seem.
  17. 50 *distorted* watts aren't gonna ruin a 350 W speaker either, unless maybe it has a 15 W tweeter in there or something. You're not gonna get more than about 100 W out of that amp even if you drive it hard. But you're right about cranking a 100 W amp into a 100 W speaker, it can be dodgy. But this kinda illustrates why I think the "2x-the-cab-rule" *by itself* doesn't help much. By that rule, you should be using a 100 W cab with a *50 W* cab, but in the scenario you mention, that wouldn't solve the problem, it would worsen it. You'd actually be better off, if you had to use that amp, running it into a 400 W cab.
  18. Yeah, it's probably not all that simple. I've been told, though, by people who would know better than I, that we'd be surprised by how little power we're using at times. And of course speakers can handle more power on an intermittent basis than they can on a continuous basis.
  19. Boil


    May 27, 2003
    Sarasota, FL USA
    So the direct question:

    Will 200 all-tube watts @ 4ohms "be enough" to drive a 4-way cabinet rated as 800 watts @ 4ohms...?

    Stage volume, dive bars, maybe 150 watts from the two guitarists...

    Nothing into the mains but vocals & electric drums...

    I know the volume is enough, but how hard could I push the amp until it damages the cabinet because of clipping? Or is the type of clipping that damages cabinets reserved for solid state amps?
  20. Only you know if it's gonna be loud enough. Anything any of us would say would be a mere guess. How loud do the guitarists play? (Just because they have 150 W on hand, that doesn't mean they use 'em all.) How loud are the electric drums? What kind of music do you play? How efficient is the cab? (4-way?? What is it, AccuGroove?) Any chance you can borrow the amp to try it out? Myself, I wouldn't do any gig but an acoustic jazz or restaurant gig with less than 300 W or so, but that's just my thing. In a small bar, with a reasonably efficient cab, you'd probably be OK, is my guess. BTW, what's the head, Aguilar DB359?

    EDIT: Sorry, I'm an idiot, forgot you'd posted your gear above. Country, pop, jazz gig, I'd bet you'd be fine. Some rock gigs, too, metal or hard rock possibly not.

    Clipping per se doesn't damage speakers. Every time a guitarist cranks a Marshall, there's clipping, and the speakers don't fry every time. As for how far you can turn it up, it's hard to quantify that, because as mcrelly noted, you can't tell from the controls how many watts you're using at any given time. I've heard people say, if you have to turn up past 4 or 5, get a bigger amp, another cab, or both. It may not be scientific, but it's probably not a bad rule of thumb.

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