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  1. #1

    maching power amp with speaker

    How do I know if an amp does not have enough power for my speaker, or if it has to much?
    Regards,
    Ivan Fegundez. Recording Technician, live sound technician, and mastering technician.

  2. #2
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    Quote: ivan
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    How do I know if an amp does not have enough power for my speaker, or if it has to much?
    is ur talking about disco amps then wyou will have a clip light on it what amd are your speakers and what amp (watt ) is ur amp for ex i have a pair of peavy pro 15's (400w per side) on a 1000 wat amp and only need to turn it up half way but i also have a set of intimidation 215's 1000 watt x2 bin per speaker (as you guessed i do disco's lol)

  3. #3
    In general, the power amp should have a continuous output that's similar to the speaker's continuous power rating. Look 'em up.

    By the way, the knob setting on a power amp has no specific, direct correlation to power output. If you have a 100W amp and you turn the knob halfway up, that doesn't mean the maximum power will be 50W. A lot of speakers have been blown by people who think the amp can't put out full power if the knob isn't turned up.

    On the other hand, setting the knob too low has one very bad effect: the mixer will clip before the amp does.

  4. #4
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    Quote: karl eilers
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    In general, the power amp should have a continuous output that's similar to the speaker's continuous power rating. Look 'em up.

    By the way, the knob setting on a power amp has no specific, direct correlation to power output. If you have a 100W amp and you turn the knob halfway up, that doesn't mean the maximum power will be 50W. A lot of speakers have been blown by people who think the amp can't put out full power if the knob isn't turned up.

    On the other hand, setting the knob too low has one very bad effect: the mixer will clip before the amp does.
    So the amp has to have the same wattage as the speaker? What is it meshered in? Wats?
    Regards,
    Ivan Fegundez. Recording Technician, live sound technician, and mastering technician.

  5. #5
    Idealy you should double the power of the continuous rating of your speaker. Although this is not 100 percent correct and this is only a general rule to navigate the commercial non standardized ratings given to speakers in order to make them appear more powerful to the end user. An example would be, if you had a speaker with the rating of 250 continuous, 500 program, and 1000w peak, and it has an impedance of 8 ohms. you would be looking for an amp that has 500w per channel @ 8 ohms as a minimum power requirement. will a 250w amp be usable , yes it would but it would give you no headroom. Now also take into consideration the power handling of the passive crossover network as I assume we are talking about passive 2way and 3way speakers, that would be the deciding factor as to how much power over this minimum rating you would be able to use.

  6. #6
    and one other note, the controls on a pro poweramp are simply input sensitivity and not volumes per se. different amp makers have different input voltages some .7 volts up to 1.7 volts on average. The controls are used to set propper gain structure from unity gain on the mixer eq comp crossover and so on in your signal path. all should be adjusted correctly to unity.

  7. #7
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    Quote: peter miller
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    and one other note, the controls on a pro poweramp are simply input sensitivity and not volumes per se. different amp makers have different input voltages some .7 volts up to 1.7 volts on average. The controls are used to set propper gain structure from unity gain on the mixer eq comp crossover and so on in your signal path. all should be adjusted correctly to unity.
    Heres another question. What is a cross over and what is it used for?
    Sorry for all the stupidity, it's just in all my career, when I get to the place where the gig is, everythings set up for me. Would you trust a blind person to set up?
    Regards,
    Ivan Fegundez. Recording Technician, live sound technician, and mastering technician.

  8. #8
    Quote
    Quote: peter miller
    View Post
    Idealy you should double the power of the continuous rating of your speaker. Although this is not 100 percent correct and this is only a general rule to navigate the commercial non standardized ratings given to speakers in order to make them appear more powerful to the end user. An example would be, if you had a speaker with the rating of 250 continuous, 500 program, and 1000w peak, and it has an impedance of 8 ohms. you would be looking for an amp that has 500w per channel @ 8 ohms as a minimum power requirement. will a 250w amp be usable , yes it would but it would give you no headroom. Now also take into consideration the power handling of the passive crossover network as I assume we are talking about passive 2way and 3way speakers, that would be the deciding factor as to how much power over this minimum rating you would be able to use.
    Quote
    Quote: peter miller
    View Post
    and one other note, the controls on a pro poweramp are simply input sensitivity and not volumes per se. different amp makers have different input voltages some .7 volts up to 1.7 volts on average. The controls are used to set propper gain structure from unity gain on the mixer eq comp crossover and so on in your signal path. all should be adjusted correctly to unity.
    sort of.... Ideally with the proper limiters in use and a careful operator, this will give you a little more headroom, however, the actual gain by having twice the power is negligible... a few dB that won't even be detectable... when you account for the increased possibility of thermal damage..

    Safer to go with matching your amp to your speaker (this is more true in MI grade gear than pro gear due to the horribly over-inflated specs that MI folks put on their gear)... the speaker sensitivity also has a lot to do with it, a highly sensitive 100 watt 2-way box may outperform a less sensitive 250 watt box, etc.... again, these ratings are hardly ever quoted with proper numbers by the manufacturers.

    also remember, you cannot under-power a speaker... I know, I know, you've heard many 'real pro's' say that you can, but you can't... if you send a signal that is too hot into an amplifier it will clip the input of the amp, the signal loses it's integrity and forms a square wave when it is clipped, that square wave will actually send an immense amount of power out of the amp, often much more than the amp is rated at, because it is a peak, and that will in turn cause the speaker to be over-powered and experience thermal damage... besides physical damage (a screw-driver through the cone or a hard drop, etc) thermal damage (over powering) the speaker is the only way you will damage or destroy speakers.

    The fine folks at the store or online retailer may tell you to double it, but it is a marketing ploy and they rarely mention the caution that needs to be exercised when using an amp that is bigger than the box it's going push..

  9. #9
    ...or, for that matter, the care needed when the amp is too small.

    What the people who worry about "underpowering" are getting at is that if the amp is too small, you'll be tempted to push it into clipping (overload). Clipping generates a great deal of energy in the high frequencies.

    The horns/tweeters in a speaker are not designed to handle the full rated power of the system. Say you've got a speaker rated at 500 watts of continuous power. The mid/high horn may only be designed to handle 50 watts; if there's a tweeter it may only be designed to handle 5 watts. Normally, this is okay, because real-world sounds have most of their power in the bass.

    But the signal that comes out of an overdriven amplifier is not real-world. It's an artificial signal manufactured by an amp operating beyond its ratings, and it's very heavy in high-frequency power. So the horns go up in smoke.

    So, if you can avoid pushing the amps too far, then as Bassred says, you can't underpower a speaker. And if you have a limiter in the circuit, properly adjusted, that will take care of the problem.

    The whole amp/speaker power thing is full of guesses, conditions and caveats. That's one of the reasons the world is moving toward powered speakers. When amp and speaker are intelligently built to work with each other, this kind of problem goes away.

  10. #10
    Quote
    Quote: karl eilers
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    ...

    The whole amp/speaker power thing is full of guesses, conditions and caveats. That's one of the reasons the world is moving toward powered speakers. When amp and speaker are intelligently built to work with each other, this kind of problem goes away.
    Good example, but look at what the manufacturers are listing their speakers as being rated and then look at what amps they put with them for the powered counterpart, you rarely see a powered speaker that has an amp that is double the RMS rating of the non-powered speaker box.... that's good sign that the engineers from those companies know that it is best not to throw too much at your speakers, even if they've rated them as having a certain RMS power handling rating....

    Here is the non-powered JBL
    VRX932LA-1
    12 in. Two-Way
    Line Array
    Loudspeaker System 800 W / 1600 W / 3200 W

    and here is their powered version
    VRX932LAP
    12 in. Two-Way Powered
    Line Array
    Loudspeaker System 1750 Watts Peak 875 Watts Continuous

    this info was pulled directly from the JBL sight for these units.

    Amazingly, they've matched pretty much the 'RMS' power handling, not the 'continuous' or any variation around it... They know that with this configuration the user will get the performance they expect without the inherent risk of frying the speaker that running a bigger amp would bring, and if it were of a greater benefit to put a bigger amp in their, why wouldn't they? They want this product to sell and do well and be recognized as a good product/investment... if they put a bigger amp in it and people ran them like idiots and blew them up all the time, they'd have a pretty hard time selling this speaker, right?! so they know what amp to run it with, as for the care from the operators, that is out of their control, they've done the best they can to provide a product that should sound good, get loud and last a good while...

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