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Strange speaker configuration

Discussion in 'Recording' started by z_man, Jul 4, 2001.

  1. z_man

    z_man Guest

    I know this is somewhat off-topic for this forum, but I figured there are alot of knowledgeable people here so, here goes:

    I just got paid by someone in monitor speakers (JBL MR905 speakers, three of them to be precise) and I haven't ever had to set up a PA speaker situation before. The speakers are 350 watts at 8 ohms each.

    Since I'm only familiar with stereo speaker set ups does anyone have any suggestions for how best to use all three speakers? Series or parallel or a combination of both? Also, any suggestions for the power rating of the amplifier that I'll need?

    [on edit: My assumption is that I'm stuck with a 24 ohm (series) or 2.67 ohm (parallel) load in a bridged mode configuration

    or

    a 16 ohm (series)/4 ohm (parallel) on one channel and an 8 ohm load on the other channel of a stereo mode configuration (am I getting this correctly?) Also, to figure out the wattage necessary from the amp do I need to add up the watts of each speaker?]

    Any help would be greatly appreciated.

    Thanks,
    Z Man
     
  2. Jon Best

    Jon Best Active Member

    Joined:
    Mar 18, 2001
    Hm. It depends entirely on what you're doing with them- are you running a live PA? Are you using them in the studio? Do you need them all to push out the same mix, or do you need some sort of 'front of house/monitor mix' combination? What's playing through them, and to how many people?

    If you're looking to buy an amp, I'd say (totally blind) get a midlevel Crown or Crest or some such in the neighborhood of 5-800W a side into 4 ohms.

    Originally posted by Z Man:
    I know this is somewhat off-topic for this forum, but I figured there are alot of knowledgeable people here so, here goes:

    I just got paid by someone in monitor speakers (JBL MR905 speakers, three of them to be precise) and I haven't ever had to set up a PA speaker situation before. The speakers are 350 watts at 8 ohms each.

    Since I'm only familiar with stereo speaker set ups does anyone have any suggestions for how best to use all three speakers? Series or parallel or a combination of both? Also, any suggestions for the power rating of the amplifier that I'll need?

    [on edit: My assumption is that I'm stuck with a 24 ohm (series) or 2.67 ohm (parallel) load in a bridged mode configuration

    or

    a 16 ohm (series)/4 ohm (parallel) on one channel and an 8 ohm load on the other channel of a stereo mode configuration (am I getting this correctly?) Also, to figure out the wattage necessary from the amp do I need to add up the watts of each speaker?]

    Any help would be greatly appreciated.

    Thanks,
    Z Man
     
  3. z_man

    z_man Guest

    Thanks for the tips Jon,

    Sorry about the lack of relevant info on my first post. We plan on using this as a vocal monitor mostly for our band as we practice in our space. Not alot of power needed I know, but we would also like to use it for other stuff.

    We've played lots of shows (indoors & outdoors) where there was either no PA or no monitors or a combination of both. It would be nice to be able to use this to help out in those situations as well. So, the amp will probably need to have alot of power so that we're not distorting too much and it may or may not need to be pushing the same mix.

    Again, from what I've been able to deduce through as many questions as I've been able to ask is, I'll be running two of these wedge monitors (350w@8ohm each) through one channel at 4ohms and one wedge (same type) through the other at 8ohms. Meaning I'll need about 8-900 or so watts a channel at 4ohms and about 4-500 or so watts a channel at 8ohms.

    Now, I seem to remember that old rule about needing twice as much power in your amp as you have in your speakers, but 1400 watts a channel @4ohms seems like true overkill for any situation involving these speakers. Does anyone have any ideas where a safe level starts and ends and where unnecessary begins?

    Thanks again for everyone's help & patience...

    Z Man

    Originally posted by Jon Best:
    Hm. It depends entirely on what you're doing with them- are you running a live PA? Are you using them in the studio? Do you need them all to push out the same mix, or do you need some sort of 'front of house/monitor mix' combination? What's playing through them, and to how many people?

    If you're looking to buy an amp, I'd say (totally blind) get a midlevel Crown or Crest or some such in the neighborhood of 5-800W a side into 4 ohms.

     
  4. Jon Best

    Jon Best Active Member

    Joined:
    Mar 18, 2001
    Well, I'm not sure you're going to need quite that much... :)

    JBL's can be pretty inefficient, though, and you're definitely safer overpowering them at least a little. I'd say 1000@4 ohms is absolutely plenty- I'm sure you could do just find with less, but that's the ballpark I would shoot for.

    Other than that, you're probably fine- two as mains off of one side of the amp, and one off the other as a monitor. If you're going to do any EQing, stick a graphic on each mix. If you have only one EQ, or a mixture, put the one with the most bands on the monitor mix. No big deal if you don't have one, it'll just mean you can't get quite the monitor volume before feedback.

    I teach recording at a Mars Music (thank god I'm out of sales... :), and we just dropped Crest as a vendor, I think. If you're near a Mars, you can get a really good (below cost, I think) deal on a midlevel Crest about that size. Most stores should have a couple left.
     

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