Monitor cab power: how much power?

Discussion in 'Miscellaneous [BG]' started by Rockin John, Nov 27, 2003.

  1. I'll begin by saying that I fully appreciate the true answer is probably, 'Well, it depends.....'

    Thing is, the average small-band monitor seems to be fitted with a 100WRMS speaker: the powered version, therefore, has a corresponding onboard amp. Such a unit would cost me about £200 + - a few quid. That's money I don't have.

    As a Techie I can build something. I've got enough kit to knock-up a 25 Watt version; perhaps 50 Watts if I used both 10" drivers. But I've no idea whether or not that'd be loud enough.

    We're a typical small pub type band: 100W PA with 2, 2x12, guitarist with 2, 50 Watt combos, me with 200 Watts. None of the kit is ever flat out, nowhere near.

    Is there any wisdom that would guide me on this. I don't want to spend ages building something only to find it's too quiet!!


  2. put it to you this way ... if you hit your low string (4, 5, 6 ... whatever) and your colon lets go ... it's too much power. :D

  3. miccheck1516

    miccheck1516 Guest

    Feb 15, 2003
    id say youd be ok with 50w if your only doing small gigs

    Do you use PA at gigs??

    EDIT:Oops, i gotta learn to read, Seeing as you are seemingly using your amp as a monitor(because the pa does the work) why dont you just turn it up?
  4. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA
    I assume you are talking about a stage wedge?

    If so, 50 will probably be ok if you aren't trying to cover the whole stage and every instrument. If you just want to hear the vocals, you'll be ok probably.

    100 if of course, a much prefered option.
  5. I concur that 50W is probably enough, especially when you have a high efficiency midbass speaker. Every 3 dB of efficiency gain equated to double the amplifier power.

    So, a 97dB speaker on a 100W amp will be about as loud as a 100dB speaker on a 50W amp.

    If it's only meant for vocals, be sure to engage a low cut on the mic signal(s) around 70 Hz to avoid booming, which wastes a lot of power. If you do this, maybe even 25W would cut it. But that's a bit of a guess. Use as much power as you can.
  6. Hello folks, and thanks for the input.

    Yes. The wedge would be purely so that I can hear myself singing (I'm bassist and lead vocals): I'm the only singer so the wedge is just for me. Currently I've no monitoring at all so seem to be straining all the time listening to our PA cabs (= 1, 2x12 either side the band).

    That straining to listen is a strain on the concentration, and I'm convinced it shows in both the singing and playing.

    Joris, I can't say about the efficiency of the 10s I've got because I was given the drivers, and I now seem to have lost the datasheet that took me so much trouble to aquire in the first place.

    [MENTAL NOTE: must remember to get more organised :meh: ]

    However, I appreciate your comment about rolling of the f. I'd never have thought of that. BTW, there must be a prefered method of setting up a mic in relation to the position of a stage wedge to minimise the poss of feedback? Any thoughts please?


  7. Skorzen


    Mar 15, 2002
    Springfield MA
    IME the best way to avoid feesback is lots of power(ie 50w cab fed with 200w of power) and a good eq.
  8. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Fifty watts ought to do it. Position the monitor directly in front of you, pointing right at your head. Assuming you're using a cardiod pattern mic, the best rejection is on-axis 180 degrees from the element. I don't know what the heck that comment re: power is about. If you turn the monitor up too loud, you'll probably get feedback. Maybe he's thinking about distortion. Good EQ is always good.
  9. Skorzen


    Mar 15, 2002
    Springfield MA
    It's about headroom. if you are running an amp that puts out 50w in general your only running about 12-15w through the speaker. As is often discussed over in the amps forum more headroom means more clarity. I can't explain why this also helps with feedback, but I can say from expirience that it does.
  10. Munji, I have a Shure SM58.

    Do you mean that I should align the mic on the axis of the monitor? Such that, if the monitor's at 45 Deg. to the floor, then the mic should also be at that angle? IOW, with the mic's XLR pointing directly at the speaker but separated by as much disctace as possible?

    No. I can't be right there. Many setups use the mic at roughly parallel to the floor with the monitor at 45 Deg.