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New to Separate Power amp

Discussion in 'Amps [BG]' started by Codydwagner, Jan 9, 2013.

  1. Codydwagner

    Codydwagner

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    Hey there,

    I know that there are probably many threads out there concerning this, but I didn't find any that really answered my question.

    Currently I'm running a crown xti 2002 (1600w at 8ohm) into a hartke hydrive 410 (1000w at 8ohm)

    My question is how can I know how hot my amp is running so I don't blow a speaker? this sounds stupid, but does is there a connection between the attenuation knob on the amp and the amount of watts being sent out? I've got some louder side gigs coming up soon and would prefer to not blow speakers.

    Thanks
  2. Gearhead17

    Gearhead17 Supporting Member

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    If the cab starts making farting sounds, speaker cones start to flap or it sounds awful, then you need to decrease the volume or the low end content. That's the only way to know.

    What are you using for a pre-amp?
  3. Codydwagner

    Codydwagner

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    well currently I am running the pre from my swr sm500, but only until my bank allows for a DB659
  4. 1958Bassman

    1958Bassman

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    Some amps use that control to alter the voltage threshold fro full power. Some, rarely, change the actual gain. If you have an iPhone, there's an app for an oscilloscope or you can download a tone generator/RTA/scope program called RoomEQ Wizard to do both. It's going to show you if the signal is clean, clipped, etc and you can play your bass through the amp, set up a mic and look for clipping. The program is free. It would also let you see your frequency response when you get the sound you're looking for and it would show you where the room has problems if you take a laptop to your gigs.
  5. Bassmec

    Bassmec

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    All I can say is that no great bass sound ever blew up a loudspeaker making it.
    That said you are pretty much asking for it, as one mistake could crease the root or edge of a cone, let alone the possibility of frying your voice coils to a turn.
    A big amp gives you headroom?, well only if you have the drivers to make use of it.
    I bet you can't use more than 25% of available power plucking a low b
    without the cab farting its arse off.:bassist:
  6. dukeisdog

    dukeisdog Supporting Member

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    I'm running 2000 watts into my 1200 watt 4X12 and don't feel as if I've ever reached the limits of my cab, but I can tell you that you'll know when you're giving too much power to your speakers.

    Might be worth picking up an identical HX410 for your bigger gigs if it's something you're really worried about.
  7. CL400Peavey

    CL400Peavey Supporting Member

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    Un bridge, and buy a second cab. You will still have more than enough power to drive both cabs to bits and you will be louder.
  8. Downunderwonder

    Downunderwonder

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    Use one channel, no need to bridge it! Like Bassmec says, the cab won't stand for anything like that power put into lows.

    Use the computer power of the XTI. You need to program it with a PC. It lets you cut the flabby lows right out. You can also limit the output voltage but on a single channel you shouldn't have to if you cut the lows out.

    The danger is you melt the voice coils with 475W of low midbass. I don't know where Hartke got the 1000W number but I bet it's not RMS at 80hz.

    Considering it is only slightly louder with 1000W you don't gain much by bridging and using the limiter to back it off to say 800W at -3dB, except then it's far more capable of smoking your cab.
  9. Codydwagner

    Codydwagner

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    So what is the danger of using a limiter, shouldn't that make things safer? Ive always heard its good to have the same power head as cab, so If I bought a 1000 watt head, would that be better?
  10. dukeisdog

    dukeisdog Supporting Member

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    You're safe how you are now, honestly. I'm pushing 2000 watts into my Mesa PH412 rated for 1200 watts and though I've never gotten up to those levels, I'm sure that the Crest could tear the Mesa cab up (and this thing is seriously a BEAST), but as long as you're smart about it, keep your lows down when playing at high volume and LISTEN to your cab.

    If it's struggling, cut some bass, or turn down. A good thing to do is get your speakers up closer to ear level (raise it with a stand, etc) so you'll be able to hear the speakers stressing more clearly.
  11. Bassmec

    Bassmec

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    If you drive a limiter with a signal level that reaches above the limiting threshold you are actually in a bass guitar signal increasing the average signal level so if you don't pull the output of the limiter down by at least the same number of dB as you are attenuating with the limiter.
    You are just increasing the voice coil temperature for a given peak level.
    You can just run 1 channel of that amp, instead of bridging till you get some more speakers to deal with the other channel.:bassist:
  12. B-string

    B-string Supporting Member

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    You have always heard wrong, and I am not surprised by that so no need for you to be surprised either. ;)
  13. Codydwagner

    Codydwagner

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    so what is a good rule of thumb? 80% of cab?
  14. Tuned

    Tuned

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    Anywhere between half and full power is acceptable, but as you get closer to full the danger starts to outweigh the benefits. Regardless, always be wary of how much power you're feeding your cab. In your case the clip light on the XTi2002 will light up at 800W, so it shouldn't light up much ever.
  15. B-string

    B-string Supporting Member

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    The problem is there is no rule of thumb. In my experience cab power input ratings are the least "standardized" thing you will find. A 410 cab rated at 1000 watts may fail at 1005 watts at 1 KHz and 300 watts at 80 Hz. Twice as much cab input power as amp might get you in a "safe" range but there is no guarantee.

    The input power is not as a general rule advertised at the frequencies bass players use all the time. Which will be much lower!
  16. Downunderwonder

    Downunderwonder

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    Not dangerous. Only if you throw all caution to the wind, exactly same as using a nominal 1000W amp hard out and not listening but the XTI filtering makes it very much the better power amp for the money than anything else.

    Equating a Mesa 4x12 to a Harkte 4x10 is dangerous stuff.

    You need to be clear that "1000W" is just a number someone made up, usually it's done with 1kHz test signal. It doesn't mean it's perfectly safe to open up on the cab 1000W of bass, not by a long shot.

    You've got an excellent amp there. Download the band manager software and experiment using this flow method:

    Start with 80 hz low filter and one channel, crank it up until it doesn't get any louder (or you run out of crank, I don't expect this but you never know).

    Wail on the bass but don't overdrive the XTI input into the red. I don't know where it clips in stereo but it won't sound nice if it's clipping.

    It should get louder all the way, so gradually drop the filter down until it starts to fart out or you get enough lows. 60hz should do for 4 string.

    I'd be surprised if the one channel isnt enough but if you can't max the amp gain with the one channel when you have enough lows and it isn't farting THEN bridge it and do over.

    If you bridge you absolutely must limit it to be somewhat safe from melting /and or flabbing if you are greedy with low end.

    Finding the heat limit is only as reliable as your ability to hear the drivers not getting any louder when you play harder. Pretty darn not reliable but way more reliable than going for 1000W and calling it good.

    So, you found a spot for the low filter that is pleasing and let you drive the one channel all way and doesn't stop getting louder. Now you want to play with the fire and you bridge it. Don't blame me if you get burned ok!

    Using the same low filter, crank it up gradually while wailing on the bass, at some point the cab will be not be getting louder or will start to flab. STOP, turn back down a nudge. Note where it is set. Next loud gig, LISTEN very carefully to see if it gets quieter. If it does turn it down, not up! Hopefully you haven't done any damage, you were warned! Sharpie that on the amp and never EVER go past it again.

    If you will be lending your rig to another bassist you must set up the limiter, similarly but with the amp control maxed and bring up the limiter from on low threshold. You want it on whatever its hardest attack setting is, release long so you hear it kick in and punish the stupid. You won't hit it too often with the attenuator set on your sharpie mark, if you do then you can up the limiter threshold.

    Earplugs are compulsory, not optional.

    There's another chapter on what to do when the soundman tells you to turn down.
  17. Downunderwonder

    Downunderwonder

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    Yeah, running into a limiter continuously sounds blech as well as making you run hotter without being dynamically louder.
  18. B-string

    B-string Supporting Member

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    I hate to be the wet blanket here........bridging without a large number of speakers attached is a not so good idea. Bridging doubles the voltage available to the speakers.
  19. Downunderwonder

    Downunderwonder

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    You got plenty of helpers with that wet blanket. One guy saying have at it and the rest saying woah there cowboy!
  20. B-string

    B-string Supporting Member

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    Okay fair enough :D

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