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  1. #1
    Join Date
    Nov 2006
    Location
    Baltimore, MD
    Posts
    117

    HELP! I'm confused. watts, ohms, speakers....uggg

    This has got to be the one thing about being a mobile DJ that I just still don't get. I'm still confused. First of all, is there any place on the net that explains this really well, for a dummy like me to understand?

    Here's what I have, and you may begin to understand why I am confused.

    I own 2 PVDJ speakers. When I bought them, they were in the store next to 2 other PVDJ speakers. It was kinda like the 3 little pigs. A little pig, the mamma pig, and the daddy pig. I chose the mamma pig, cuz I thought the smaller PVDJ speaker was a little to wimpy sounding. The big one was just too much $$ at the time. OK. I've looked SEVERAL TIMES. The back of the speaker says PVDJ 112i. It then says 8Ohms Max Power: 300watts Program.

    That's got to be a typo. First of all, the speakers look bigger than 12 inches. Second, after I blew something in my Crest Audio amp by pluggin it into these speakers, I got another amp from the store where I bought these speakers. I asked the guy for a amp that matches up to these speakers, so he sold me a Mackie M1400i amp. Mackie's web reports these specs:

    1400 watts @ 4 ohms bridged
    1000 watts @ 8 ohms bridged
    700 + 700 watts @ 2 ohms stereo
    500 + 500 watts @ 4 ohms stereo
    300 + 300 watts @ 8 ohms stereo

    So, I'm assuming that Peavey screwed up on the label. I also am pretty sure I have the user manual around here somewhere and it says PVDJ 115i. If that's the case, I can see that I match up perfectly at 300watts per channel at 8ohms. I think I understand that. That's easy when the numbers MATCH. Its when they don't match that gets me confused.

    Apparently this amp can go up to 1400 watts. How would I do that, and what type/size of speakers would I need? And do you get a speaker that is rated for more watts then the amp (say, a 400w speaker plugged into a 200w amp), or the other way around?

    I'm so lost....

  2. #2
    Join Date
    Apr 2008
    Location
    Northeastern Mass
    Posts
    56
    The rule of thumb when powering speakers is to get an amp that provides 1.5 - 2 times the RMS (continuous) power rating of the speaker (NOT program power, that's already RMS doubled). To get that Mackie power amp to 1400 watts, you'd have to bridge it (basically it combines both channels to work as one big one) and hook it up to a 4 ohm load (1 4 ohm speaker or two 8 ohm speakers "daisy chained", or wired in parallel), but 4 ohms bridged isn't highly recommended.


    By the way...how in the world did you fry a Crest amp?

  3. #3
    Join Date
    Nov 2006
    Location
    Baltimore, MD
    Posts
    117
    I wish I knew the answer to that question. It was a CA6:

    8 Ohm Stereo - 400 W
    4 Ohm Stereo - 600 W
    2 Ohm Stereo - 750 W
    8 Ohm Bridged - 1200 W
    4 Ohm Bridged - 1500 W

    I'm not really sure how I had it set in the back. I should have looked first. I'm a noob. Let me also mention that I previously had this same amp plugged into some old Community speaker and it worked great. Also had plugged in a pair of Peavey SP-2's and they worked great. Didn't change anything on the amp, and plugged them into the PVDJ speakers.

    Because the crest only had bananna plugs in the back, I had this adapter that went from 2 bananna plugs to the 1/4 inch plug, to standard 1/4 inch speaker cable. I plugged it in, didn't get much sound. I could barely hear it. Clipping light started going nutz, and protect light started blinking. I then smelled some burning. Now channel A is shot! Channel B still works. I'm thinking I had it bridged and sent 1200 watts to a speaker that can only handle 300 and it fried something on the amp.

  4. #4
    Join Date
    Sep 1998
    Location
    About 10 miles South of Disneyland
    Posts
    10,365
    John,

    First of all...avoid using adapters whenever possible...you never know when what seems like the proper adapter might be shorting out or reversing your phase, or such stuff.

    They use many different ways to rate speaker handling power...numbers can always be manipulated to make a product seem better, faster, more desireable...

    RMS
    The term "RMS power" is sometimes used in the audio industry as a synonym for "mean power" or "average power". For a discussion of audio power measurements and their shortcomings, see Audio Power.

    RMS and Program are similar...Peak is about double those.

    Reputable companies will use a full-range signal when determining these numbers, knowing that it takes more power to produce more bandwidth at a certain volume...less-than-reputable companies will use a test-tone signal, (usually 1kz or 1000 herz aka cycles per second) so that the drivers work very little to produce staggeringly high output levels. You've seen cheap car stereos that claim 5000 watts for $39.95? That's why. Actual music power with a full-range signal might top out at 5 watts!!!

    It would be my guess that something in the adapter chain shorted out the outputs of the Crest amp...even with the right adapters, if one came loose or wasn't plugged in all the way, you're done!

    Here's a little something to help you visualize the different impedence loads and how they are achieved:



    Keep on Rockin',

    Ken

    http://www.djken.com

    (714) 686-8397
    USMC '82-'85, 5711/0811
    A Budhist walks up to a hotdog vendor and says "Make me one with everything!!! Robin Williams

    "Peace is that brief glorious moment in history when everybody stands around reloading". --Thomas Jefferson

    "An amateur trains until he gets it right; a professional trains until he cannot get it wrong!" unknown

  5. #5
    Join Date
    Nov 2002
    Posts
    5,377
    Can't add much to what has been said except if you do not know, never plug speakers in while the amp is turned on. That is one way to cook an amp.

    Oh, and concerning the size of the woofer, I suppose Peavey could make a mistake on the tag. It's sure easy enough to lay a ruler across and measure the woofer to find out exactly what you have.

  6. #6
    Join Date
    Oct 2002
    Location
    Central Illinois
    Posts
    5,606
    The CA6 was a better match than the M1400 IMHO. Ideally, a 500 to 600 wpc amp would be about perfect. However, if the M1400 is allowing you to play as loudly as you wish without clipping and or compressing the sound then it's good enough.

    I'm not really sure what your question is...I suspect you shorted out your Crest amp and it failed...rare for a Crest as they generally have a quite good protection circuit.
    Copyright 1995 - 2013 Bob Dietrich AD&L
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    Bob Dietrich
    Acoustic Dreams & Lightbeams
    Peoria's Finest Disc Jockey Entertainment


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