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Amplifiers...How big,and what is input sensitivity anyway?
When selecting an amp for a speaker how big an amp should I get? First off lets dispel a rumor... \"I have a 500 watt speaker, and a 100 watt amp... I shouldn't be able to blow the speakers!\" ABSOLUTE RUBBISH! when an amp runs out of power the power supply begins to sag...the normal ~sign wave swing that moves the cone in and out is replaced by a ____ flat line which is DC voltage where the power supply runs out of power. This DC voltage is dissipated in the form of heat.. heat that the voice coil cannot get rid of, if done for too long, the voice coil starts to distort, and de-laminate... then the SMOKE comes out.... :shock: and once that happens... it's impossible to get it back in... the smoke that is... :roll:
Here is what JBL says about this:
JBL Technical Note - Danger: Low Power
Here's The Killer: Distortion Generally Affects High Frequency Drivers.
The additional power generated by overdriving the amplifier is rich in harmonics (distortion). These harmonics can be particularly dangerous to high frequency drivers. Harmonics are higher frequency multiples of the original signal; therefore, the high frequency component of a loudspeaker system must bear the brunt of the distortion - even though the original signal may have been generated by a bass guitar.
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When an amplifier is overdriven, the contours are "clipped" off, producing a near square wave, having flat areas at the top and bottom limits, in which the average power approaches the peak power. When this occurs, up to twice the amplifier's rated output can be delivered to the high frequency driver, which may not be capable of handling the abnormal load. A higher powered amplifier, however can generate the required power levels without clipping, allowing the loudspeaker system to receive program material containing a normal distribution of energy levels. Under these conditions, damage to the high frequency driver is most unlikely.
Ok so my speakers are rated at 500 watts...how much power should I have? Well I'm a proponent of too much power is never enough!...but realistically... you ask? well, Crown specifies 2 to 4 times the rating of the speaker...that means 2X500 watts = 1000 watts (that is a minimum figure... remember that if there are 2 woofers in your speaker EACH will get only 1/2 the power you feed the speaker) further 4 times the power 4 X500 = 2000 watts... and that is EACH speaker, so, if you had 8, 500 watt speakers, running 4 per side off an amp that has 2X2000 watts (or 4000 watts bridged mono) that is still only 500 watts per speaker... and we know now that we should have 1-2000 watts for each...Realistic? doesn't seem to be but it is...The one thing too much power if unleashed on your speaker will do is drive it up against it's mechanical stops (the magnet plate) and or tear the surround from over excursion...BUT you have a car with 200 horsepower... does that mean you HAVE TO USE IT...ALL THE TIME... no, thats silly, but it's there if you need it isn't it?
If you find yourself under powered as most of us find ourselves (who have the cash to fork out for an amp capable of producing 4800 watts per driver ..as in the case of the Peavey QW subs... thats 9600 watts of capability on a single cabinet 2X18!!!! So, the gain structure will show us where the limits are, and when we see the mixer meters nearing clip we know that the amps are also near clip and thats all the systems got...there is also limiting but that is for another post...
Now what is that pesky input sensitivity anyway, and why do I need to know it? well, if you perform a Gain structure, it becomes kind of a mute point because the amps input attenuators will be set during the gain structure.
But for those of you discerning types, the input sensitivity is the point at which ...with a specified voltage input... say 1.44volts, the amp will put out it's maximum rated output... So why isn't fully clockwise on the amp gain control full output? It has to do with a lack of standardization... some equipment puts out more voltage than others, and we have even got different standards from \"consumer\" to \"pro level\" gear. So the variable nature of the input on amps allows for different equipment to function on most amps...
As for the burning question, why not set the amp sensitivity and use the gain controls on the Driverack to set the level the amps get... and the simple answer is \"thats probably the better way of doing things, BUT the level of experience here is generally \"newbie\" or at least new to Digital system processors... So it's easier, and less likely to create problems if we simplify and just let the gain structure set the amp levels. Another determining factor as we have already specified.. is that the amps we use are generally under powering the speakers we have.
Here is what JBL says about this:
JBL Technical Note - Danger: Low Power
Here's The Killer: Distortion Generally Affects High Frequency Drivers.
The additional power generated by overdriving the amplifier is rich in harmonics (distortion). These harmonics can be particularly dangerous to high frequency drivers. Harmonics are higher frequency multiples of the original signal; therefore, the high frequency component of a loudspeaker system must bear the brunt of the distortion - even though the original signal may have been generated by a bass guitar.
...
When an amplifier is overdriven, the contours are "clipped" off, producing a near square wave, having flat areas at the top and bottom limits, in which the average power approaches the peak power. When this occurs, up to twice the amplifier's rated output can be delivered to the high frequency driver, which may not be capable of handling the abnormal load. A higher powered amplifier, however can generate the required power levels without clipping, allowing the loudspeaker system to receive program material containing a normal distribution of energy levels. Under these conditions, damage to the high frequency driver is most unlikely.
Ok so my speakers are rated at 500 watts...how much power should I have? Well I'm a proponent of too much power is never enough!...but realistically... you ask? well, Crown specifies 2 to 4 times the rating of the speaker...that means 2X500 watts = 1000 watts (that is a minimum figure... remember that if there are 2 woofers in your speaker EACH will get only 1/2 the power you feed the speaker) further 4 times the power 4 X500 = 2000 watts... and that is EACH speaker, so, if you had 8, 500 watt speakers, running 4 per side off an amp that has 2X2000 watts (or 4000 watts bridged mono) that is still only 500 watts per speaker... and we know now that we should have 1-2000 watts for each...Realistic? doesn't seem to be but it is...The one thing too much power if unleashed on your speaker will do is drive it up against it's mechanical stops (the magnet plate) and or tear the surround from over excursion...BUT you have a car with 200 horsepower... does that mean you HAVE TO USE IT...ALL THE TIME... no, thats silly, but it's there if you need it isn't it?
If you find yourself under powered as most of us find ourselves (who have the cash to fork out for an amp capable of producing 4800 watts per driver ..as in the case of the Peavey QW subs... thats 9600 watts of capability on a single cabinet 2X18!!!! So, the gain structure will show us where the limits are, and when we see the mixer meters nearing clip we know that the amps are also near clip and thats all the systems got...there is also limiting but that is for another post...
Now what is that pesky input sensitivity anyway, and why do I need to know it? well, if you perform a Gain structure, it becomes kind of a mute point because the amps input attenuators will be set during the gain structure.
But for those of you discerning types, the input sensitivity is the point at which ...with a specified voltage input... say 1.44volts, the amp will put out it's maximum rated output... So why isn't fully clockwise on the amp gain control full output? It has to do with a lack of standardization... some equipment puts out more voltage than others, and we have even got different standards from \"consumer\" to \"pro level\" gear. So the variable nature of the input on amps allows for different equipment to function on most amps...
As for the burning question, why not set the amp sensitivity and use the gain controls on the Driverack to set the level the amps get... and the simple answer is \"thats probably the better way of doing things, BUT the level of experience here is generally \"newbie\" or at least new to Digital system processors... So it's easier, and less likely to create problems if we simplify and just let the gain structure set the amp levels. Another determining factor as we have already specified.. is that the amps we use are generally under powering the speakers we have.
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