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underpowering cabs

Discussion in 'Amps and Cabs [BG]' started by MCBTunes, Oct 21, 2005.

  1. people have mentioned underpowering cabs here a lot or overpowering the amp.

    does that mean running a 8ohm 1x10 rated at 250RMS and a 8ohm 1x12 rated at 600 rms from a 400 watt @4ohm head is a bad thing?

    SHould I be looking for 2 cabs rated at approx 250 instead? What if they were both 600 RMS, Then does it become bad?
  2. Its a question loaded with controversy.

    If your power amp can't put out as much power as the speakers can handle, with a healthy reserve for transient loud notes, accents, the speakers won't be as loud as they could have been. That's about it.

    That leads to some potentially bad things. You push the amp too hard, to its max, to get the volume you want, which drives the amp into clipping, and that can potentially damage the tweeters, and rarely the main speakers.

    But 100w amps don't blow 600W speakers. Blowing speakers requires putting more power into them than they can handle.

    You CAN do that with an "underpowered" amp, its not easy. Clipping puts more power out than the amp is rated for, and vastly more energy into the tweeters range. So clipping is something you should avoid. But again, a 100w amp clipping won't put out enough power to blow a 600w cab most likely. More likely a 500w amp blows a 600w speaker's tweeter.

    And if you don't hear distortion, most likely you cannot blow a speaker by under or overpowering it.

    Trying to play too loud for the equipment you have is what blows speakers. Either running the amp to the limit resulting in clipping that trashes the tweeters, or having an amp way more powerful than the cab, and driving the cab too hard.

    Many people run twice the amp power compared to speakers rating with no problems. As long as they avoid the cab farting and distorting, its fine.

  3. Thor

    Thor Moderator Staff Member Gold Supporting Member

    Nicely put, Randy.

    Well, you have 3 questions, so here goes:

    A) The cabs in parallel will each receive that same amount
    of power. You will overdrive the 1x10 @ 250 before the
    other cab, and possibly before the amp begins to clip. Once
    you are up to that level, that is as far as you should go.

    B) Similar to A, but now both cabs will
    be overdriven at 250 W instead of one. Probably you won't
    reach 500w @ 4 ohms, depends on the amp and driver specs, which are notoriusly inaccurate.

    C) Now the limiting factor is the amp. You will run out
    of headroom and the amp begins to clip the signal.

    Most driver damage in speaker cabinets is caused by
    loud clipped input. You are better off with plan A or B.
    If you go with C, you have to be careful to watch the
    clip indicator if you have one.

    I'll bet that 12 sounds nice and fat with the 10 though,
    so I would leave it alone.

    You will find a lot of people here have multiple rigs,
    the 'Big rig' and the little rig for smaller rooms, jams and

    Than there is the 'Force', the 'Deathstar Rig', and
    'Earthquake Central'. TB's largest rig designation,
    'The Rig of Doom', is also called 'The Tombowlus'. ;)

    I hope that clarifies it a little for you.
  4. People aren't concerned about underpowering cabs, they're concerned about being underpowered for a given situation.

    If your 400 watt amp is capable of producing the volume you need without excessive clipping it won't matter one bit if your speakers are rated to handle more.

    If the amp isn't enough the solution is to get a more powerful amp, not lower handling cabs. That is what is meant by underpowering.
  5. All that and I never answered your question....

    the 250W cab mated with a 600w cab and a 400w head is probably fine. Both cabs will get 200w.

    If you had 2 600w cabs instead, they'd still get 200w apiece.

    If you want to plan for the future, I'd go with the 2 600w cabs, you can eventually get something like a 2000w amp to drive them if you later need more volume/headroom.

    The 250w cab would limit you, you'd have to get a new cab to significantly upgrade power later.

  6. so basically
    2 cabs rated at 200 watts each to make a 400 total(assuming sensetivity yadda yadda) would be LOUDER? than if i had 2 600 watt rms or whatever off the same head?


    having 600 watt heads I wont be as worried about blowing speakers therefor I will turn the amp to 11 and wreck it?
  7. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    No, wattage rating doesn't mean anything for efficiency.
  8. chaosMK


    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    If you want a 1x10 + 1x12 rig, that head and power handling of the cabinets are probably just fine.
  9. Thor

    Thor Moderator Staff Member Gold Supporting Member

    A: Assuming the same sensitivities, the cabs will only get
    200w each, that's where you run out of amp. With that
    assumption, it would be the same, but the assumption is rarely valid.

    B: You wont ruin the Amp, you will clip the signal and damage
    the drivers in the cabs.
  10. Wattage rating has nothing to do with loudness... sensitivity determines loudness for a given amp.

    the 250w speaker could be louder or quieter than the 600w speaker with your 400w amp.

    3dB higher sensitivity in the speaker adds up to equivalent to twice the power. So if the 250W speaker is listed at 103dB/m and the 600w speaker is listed at 100dB/m, then 200w into the 250w speaker would be just as loud as 400w into the 600w speaker.

    I like to keep things well matched. Why run 2 cabs, a 250w, and then pay way more for a 600w cab to run together? The 250w cab will be breaking up and force me to stop increasing power. So might as well get another cheaper 250w cab instead of the 600w and save the money.

    Or plan for future and get a pair of 600w cabs now.

    On the other hand, you can use the 250 and 600 together now, you won't overpower them with a 400w amp, and upgrade the 250w speaker later when you get more power.

    Just keep track of what your weakest link is now, and how that limits your choices going forward.

  11. NJL


    Apr 12, 2002
    San Antonio
    Bunch of geeks...

  12. Thor

    Thor Moderator Staff Member Gold Supporting Member

    You need sensitivity training ... :smug:

    Pay attention and learn, dogbreath! :eek: :D
  13. yeah I'm gonna search sensetivity now...

    the 250 cab i was thinking of was an aguilar S210.... 250 watts RMS 8 ohms but it was only 99db/m.... now if 103db/m.... which I see a lot of online is more than TWICE as loud... the 99db/m sounds like a piece of crap deal. I imagin it would sound good though ;)
  14. NJL


    Apr 12, 2002
    San Antonio

  15. 12bass


    Jan 2, 2003
    Victoria, Canada
    Although 103 dB is 4 dB louder than 99 dB, we don't hear it as twice as loud. For something to sound twice as loud requires a 10 dB increase in volume.

    That said, a cabinet that has a sensitivity of 99 dB will take over twice as much power to create the same volume as a cabinet rated at 103 dB SPL.

    You might want to check out my thread on the NL-210 and D210XST to see how little manufacturer's SPL specifications actually tell us.

    By the way, I think that the GS112 is a pretty sweet sounding cabinet. How loud do you plan to play? Your needs will be quite different if you are just jamming, or if you are playing big stages. Playing around Saskatoon clubs, I can get by with 250W into a 2x10", but I don't play that loud. IMO finding the right pieces for your rig is a balancing act between finances, tone, and overall volume required.
  16. Some of the inefficient cabs sound great, you just need a powerful amp to drive them... and need to know that going in...

  17. 12bass, yeah my buddies in Tickle Trunk, not sure if you know them or not, but they simply have a yorkvill 200 1x15 combo on bass. But then a PA system. Thats why I assukmed I'd never need more than 400 watts, and even 200 is nice....

    I'm thinking of picking up an aguilar S210 and later down the road a mesa powerhouse 1x12.to go with a head/pre/power whatever i end up with.

    Let me know when you play some gigs in s'toon, I'll stop by and check it out.
  18. Jazzin'

    Jazzin' ...Bluesin' and Funkin'

    My cabs are very underpowered. I have a 300W @ 4ohms amp parallel with an 8ohm 1000W handling cab and an 8ohm 600W handling cab.
  19. Thor

    Thor Moderator Staff Member Gold Supporting Member

    This post makes a great point, and one that bears repeating,
    particularly this part (kindly forgive the minor edits that are mine):

  20. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    The Yorkville XM200 is a VERY loud 200 watts.