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Max Wattage

Discussion in 'Amps and Cabs [BG]' started by evan_phi, Mar 21, 2006.


  1. I have 2 Peavey Black Widows rated at 350W continuous and 700W peak, both running 8 Ohms. I am building these into a Cab with a horn.

    i'm thinking of making a power amp/preamp setup for the head.

    what is the highest-powered amp i should be looking to buy?
    also, is there a "best" way to wire the 3 drivers? (series/parallel)

    Thanks.
     
  2. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    You can buy as big as you want as long as you don't turn it up so loud the speakers catch fire. Buy the biggest/best power amp you can afford.


    Well, if 2 are identical, and 1 is a horn ... you'd probably wire the 2 8 ohm BW's in parallel for a 4 ohm load, and look for a crossover that matched the impedance of whatever horn you plan to use. You may have a problem finding a horn that will go low enough.


    Use the SEARCH feature; been discussed, and generally discounted as not very cost-effective. If you meant 'use' instead of 'make' that's perfectly reasonable.
     
  3. thats what I meant.

    building one would just be... silly.
     
  4. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    I'll keep this going ...

    Your 15's will start to 'beam' and be very directional by 2000hz, so you need to the high frequency elements to take over before that. Peavey sold BW 2x15's with no tweeter, so some would probably go without. BW's are very sensitive but don't do huge lows (at least the older modles I am familiar with; 1502's I think). You might take a look at what Peavey does with them and duplicate that. I believe they used to sell an SP4 PA speaker with 2 BW15's and a large horn; they would probably tell you the dimensions and tuning if you asked over at their forum.

    They also used to sell a '1516' which had a 15" BW with a pair of 8's crossed over at 250hz. The 8's were pretty unremarkable speakers and probably Eminence Alpha 8 MR's would do ok. You'd want to make sure you have enough so that the sensitivity of 1/2 the small speakers matched the sensitivity of a single BW. Same logic with a horn but I don't much care for them so I have never studied them much.
     
  5. I have two BW 1504's.

    the reason i am going with the horn is because it is simply easier to control, and it is cheaper.

    any suggestions on a pre-amp that costs like... 200-300$?
     
  6. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    Easier to control? I don't understand. You use a knob to control any of them.


    Cheap Preamps? Yamaha PB1- about $100 on ebay; built like a tank, clean and quiet, lots of patch points.

    Spendier- BassPodXT (about $300). Pushes a power amp fine, simulates lots of amps and cabs, easy to carry.
     
  7. which of those are rack-able?
     
  8. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Typical 15 inch drivers are beaming by around 1KHz - not 2KHz. In decent PA 2-way PA cabs they'll be crossed over as low as the horn size and compression driver allow. Only in bass cabs will you find them crossed over a lot higher - and a lot of that's because then it doesn't require a better compression driver or larger horn. Cheeepnezz.
     
  9. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Also, as I recall, the 1504 was designed for horn-loading. I don't know how well they'll work in a direct radiator cab of typical size. Best bet for lows in the earlier 350 RMS BW is the 1505.
     
  10. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    The Yamaha PB1 is a 1 space rack mount.
     
  11. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho

    So ... I guess that 'be very directional by 2000hz' is indeed an accurate statement.
     
  12. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    A useful number would be where beaming becomes prominent. A number above that - be that 2K or 10K is not so accurate if one is trying to actually understand what's going on.

    EDIT: just as saying a rack weighs 3-5 pounds isn't so accurate when it weighs around ten pounds more than that ; }
     
  13. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    You are absolutely correct. When I made my post I couldn't recall the precise frequency per diameter.

    You are also correct about the SKB cases, and that post has been updated.
     
  14. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Beaming becomes an issue about when the wavelength of a specific frequency becomes shorter than the speaker's actual working diameter. Formula for figuring wavelength from frequency (or vice versa):

    speed of sound / wavelength = frequency

    Rounding the speed of sound to 1130 feet per second - 13560 inches (temperature, altitude, and humidity dependent) - and assuming there's around 13" of speaking area on a 15" speaker:

    13560 / 13 = 1043 Hz

    There's some slop to play with but that's considered a pretty good way to determine where the beaming becomes an issue for a capable driver.
     
  15. i'm not really to concerned wiht the sounds of the speakers, i'm just using what I have.

    i will def. upgrade later though... don't know what to go to thoough.
     

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