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Musos - need some help with bass amp questions

Discussion in 'The Pub' started by edgelett, Oct 4, 2007.

  1. ok firstly I'm a guitarist & I use a Vox AC30 (combo amp) so I have no clue about bass gear...

    anyway on Friday night, while setting up for a gig, our bass player's amp fried. Now it's the 2nd time it's happened, all he did was turn it on. he's sent it off for repairs but he said he might have to buy a new head since his is starting to get unreliable.

    However we're not sure what amp he needs to get (in terms of wattage etc). he doesn't know about ohms & watts so he's not sure what he needs to pump his speakers.

    Currently, he runs a 4x10" 600 Watt 8ohm and a 15" 600 Watt 8ohm, at the same time, with his current amp. he said he 'bridges' his 2 speakers together.

    We can't work out though exactly what this means. Is the amp actually running at 1200 Watts, 4ohms? or 1200 Watts 8 ohms? or 600 Watts 8 ohms? or 300 watts 8 ohms? or some other possibility?

    We want to buy a replacement amp that's going to do the job, but can't see many for sale that are more than 750 watts.
  2. oh forgot - his current amp is a Carvin 600 Redeye
  3. i think you'd be able to find a Peavey MAX 2x600 head unit that'd do it perfectly. audioproducts.com.au
    i think they'd be able to help you
    eitehr that or ring the bass center in south melbourne, tell them exactly what you had, ask what went wrong, and what you need. when they suggest oh this little unit, say no no you misunderstood. i will choose the brand, just tell me what type of unit i need.
  4. Wattage will most likely be peak output, for a start. No, having multiple speakers in his cabinet does not combine the peak wattage capability. He needs to ensure that he doesn't overdrive his speakers, so he shouldn't get a larger wattage head then the speakers are rated to. As posted a 2x600 watt would do nicely. Just get something reliable :p

    Got rid of my bass amps years ago as I just never pick up the bass these days! My bass is even out on what appears to be a permanent loan :LOL: I use a nice Marshall head with a quad box for my guitar :grin:
  5. phew, i was pretty certain but i'm glad you said that. i thought, if i'm wrong a bass shop will tell them. at least i know with those speakers he's doing a crossover to send the lower frequencies to the 15" speaker for fullness and the low mids and up to the 4 x 10" for clarity and punch. so the 2x unit would be better so it gets rid of any crackle, as it allows the "2" sounds to eb sent seperately yeah?? (could be wrong that was a question more than staetment). as for the law of ohm's.... pfft. forget it i don't understand that mumbo jumbo even when put in laymans terms.
  6. ok cool so keep the head to 600w to be safe eh?
    he never drives it too hard, it's loud a fcuk so no need to drive it to full power.

    we had to share our gear with an interstate band recently, and the guitarist kindly turned my AC30 up to FULL VOLUME on TWO CHANNELS!!!!

    I never drive it above about 1/3 of it's full power. I was VERY pissed off.

    Will probably not get a Peavy to replace it, if he has to buy a new amp he'll be looking at around $2000+ on a head. currently looking at Eden, Ampeg, SWR and GK units.
  7. Believe it or not, underpowering speakers will do more harm than overpowering them. Without enough power in your amplifier, trying to get more volume will result in the amp distorting. (DC) The amp then sends a distorted signal to the speakers and guess what?? Speakers distort!! Then they burn the voice coils.

    2 x 600watts should be fine. But, you would want to run the 4x10" drivers off one channel and the 15" driver off the other. The 10s need to be wired in a series/parallel configuration. 2x10" wired in series to show a 16om load, same with the other 2. Then wire both sets together in parallel to show the amp 8ohms again.

    Audioworks sell some good stuff and if you find something you want from them, lemme know as they are one of our suppliers and Ill be able to get you a good price on what you want!
  8. bam - you lost me a bit there.
    He's running 2 boxes: one is a 4 ohm-4x10-600 Watts
    THe other is a 4 ohm-1x15-600 Watts

    so you suggest getting a BIGGER amp wouldn't be a problem?

    cause one of the ones we're looking at is a GK 1001, which is a 750w amp, bi channel.

    the current amp he has,t he Carvin 600 Red eye, has a convenient 'bridge' button which doesn 90% of this crap for us lol.

    according to the manual, it makes the amp run 600w at 4ohms bridged (it's here if you want to look https://www.carvin.com/manuals/R600-R1000-seriesIII.pdf )
  9. Running that existing amp at 4ohm bridged is gunna make it work alot harder. Any amp will when its bridged. Could be part of the reason for its failure.

    But yeah, the more power you have on tap, the better. The speakers will only use as much power as they can handle. So say your speakers are rated to 600w and your amp is rated to 800w. The amp wont consistently put out 800w. Infact, it will put out much much less than that. The fact that the amp is rated higher than the speakers means nothing.

    As i said earlier, a lower powered amp will blow speakers up much quicker than a higher powered one. By having more power, you have more headroom and you will get a much more dynamic sound.

    Basically, if youre replacing it, stick with a good brand and get as much power as you can afford.

    It may also be worth sticking a multimeter over the terminals of the speaker boxes to see if the problem isnt occuring there. Its easy to do. Cos if the speakers have a fault, you may run in to this problem with a new amp. :cry:
  10. ok Bam - so if we DON'T bridge the amp, and instead just run it straight into 2 speaker boxes, is it then putting out LESS power? i.e when not bridged yet still sending signal to 2 speaker boxes, is it only sending 300w to each speaker box?

    how do we get it to still give decent power to each speaker box?
  11. if it's 2 x 600, on 2 x 600w speakers, it will send a maximum of 600w to each speaker, depending on volume. if you put a 2x750w amp on there, the amp isn't putting 750w out as that's it's maximum output, it will just put the amount the volume and speakers ask for, which would be 600w full volume.
  12. thanks flex - checking the manual again it says that at 4 ohms it's only sending 250w.

    it's when it's bridged at 4ohms that it send the full 600.

    so, now I'm REALLY lost as to what unit we need to power the 2x 600 watt cabs
  13. with a 2x i don't think it'll be bridged as you'll hav 2 outputs and possibly seperate EQs or gains/volumes.
    don't quote me on that but i think that's what it will be.
  14. Given that every bass player I know feels that it is their god given right to be louder than everyone else in the band, I'd be careful about recommending an amp with a higher rated peak output than the peak output rating on the speakers :rofl:
  15. the manual for the amp he has, shows a BRIDGE button on the rear, and specifies that while bridged it runs 4 ohms and 600watts.
  16. well, i will build a BRIDGE and get over it. seeing as i was uncertain from the outset i'm just glad i got one thing right
  17. I wasn't having a go at you mate...i'm grateful for the help, as I said I use a combo amp so am not sure when it comes to running speaker boxes.

    i'll head into derringers in adelaide today & ask what 2x600 amps they have I think.
  18. tell the bass player to stop stuffing around buy a small combo with a line out through a cabinet simulater and go through the P.A. spend the rest on in ear monitors and then you wont have an issue with the bass being to loud in the crowd because they can't hear it on stage. with a 15" driver you will push the sound for miles. think of how many times you have walked toward a venue and heard the bass better outside?
    one important thing with wattage if you double the wattage e.g 100w to 200w you will only increase volume by 3db 200w to 400w only another 3db. speaker efficiancy will also play a part.
    having used a carvin many years ago when bigger was better it was sold for nothing as the new laws on noise ment that you wen't allowed to hear anything outside. the technology is better now and no need to get tinitus.
    I may have a SWR combo out on loan that i may be able to offer if you are interested.
  19. What bam said,

    but buy yourself a surge protector, my guitarist had his mesa head blown twice cause there were power surges.

    and the quad blew once as well.
  20. Geeeeezus you let your bass player run a 600 watt amp, and you're running an AC30..... can you ever hear yourself over the bass edgelett?:shock:

    OK lets get a few tech type things out of the way.

    -The rating (in Watts) of an amp tells you how much power it can deliver to your speaker/s.

    -The amp is designed to deliver its power to a speaker of a given impedance (or resistance) measured in ohms.

    -If your amp is designed to work with an 8 ohm speaker and you connect it to one 8 ohm speaker it will deliver its rated power happily.

    -If however, you plug the same amp into a 16 ohm speaker or two 8 ohm speakers in series, your amp will only be able to deliver about half of its rated power. But it WON'T hurt the amp.

    -Then if you plug your 8 ohm amp into a 4 ohm speaker or two 8 ohm speakers in parallel your amp will try to deliver roughly TWICE its rated output. It may well go BANG! Particularly if it's a transistor amp, tube amps are a bit more tolerant.

    -Loudspeakers power ratings are how much power they can have fed into them, and thats it. Lots of people seem to think that the higher the wattage the loudspeaker is, the greater the volume. Wrong. Usually the opposite is true.

    -What I suspect is happening is that when you bridge the amp is that the two 4ohm speakers are in parallel giving you a 2 ohm load and the amp is trying to deliver way over its rated output.... BANG!

    -When you take the amp to get fixed make sure you take the speakers too, and ask the tech what's going on. It may be your speakers blowing the amp.

    -Personally I'd loose the 15 inch and just use the 4x10 box, 15's tend to make the bass loose definition and just sound kinda woofy. Let the P.A. do the projecting, what you want on stage is a comfortable volume and no more. 600 watts should be s#*tloads of power.