Discussion in 'OT Technology' started by notaniceperson, May 14, 2009.
Just wired up an amp in my car and need a quick tutorial on crossover vs gain.
go on. . .
what do you want to know? gain is the adjustment for input levels, crossover is used to limit frequencies in the range of the crossover's adjustability
Ok i just needdd it in plain english. Thanks.
gain: to you this might sound like how loud your system is, however do not use this as a volume knob. To adjust my gain I will turn up my deck (receiver in car w/ CD player and what not) to abou 80% of maximum volume and then put the gain just below the point to where it starts to sound distorted/bad.
crossover: this is not meant to be used as a volume knob either. the crossover essentially sets the threshold at which your amp will put sound to your speakers. for example high pitched noises have a higher frequency number than lower deeper sounds (usually observed in subwoofer with car audio). I would check your manufactuers website on the speakers you have for the correct crossover adjustments.
keep in mind I am not an audiophile, but just the guy who installs them occasionally in his garage. I might get yelled at in here for my recommendations. but at least they are in "plain english"
that's pretty much how it goes. However, many people still don't understand what sounds "clean" and what sounds "distorted". I've always set my gains using a digital multimeter. I set the volume to the highest I would possibly listen to it. Play a sine wave on repeat for the appropriate speakers you would like to set. for a sub, usually a 50 hz sine wave. disconnect the speakers you will be setting. Use ohms law.
sqrt(power * resistance) = voltage
in other words: sqrt (watts rms * impedance the amp is "seeing") = voltage. adjust the voltage until the number on the dmm matches whatever the voltage you get from this equation.
How would this even work? You don't know exactly what wattage your amp is putting out, a lot of amps on the market may claim 500watts rms for example but probably never reach it. So are you then assuming a gain of 50% on a 500 watt rms amp would be putting out 250 rms? This just doesn't sound like a very efficient way of doing this but I could be wrong.
many amps are pretty much in the ballpark of their rms wattage. don't ever pay attention to peak wattage. you may be getting the 2 mixed up.
as far as wattage ratings on an amp go, I look at the fusing in the amps and figure about 100 watts for every 10 amps of fusing. This isn't always accurate b/c some amps are pretty efficient in their power use and get better than 100w per 10a. But it's a decent rule of thumb.
For example: you have an amp with a 30 amp fuse, you can generally figure that amp will produce about 300 watts.
current X voltage can get you in the ballpark... though some amps are more efficient, some are less.
30amp fuse should make a 400watt amp... but it's not a sure thing.
we'll call it an ok ball-park power estimator
Avg Class D amp is in the 70% efficiency range. Avg A/B is in the 50-60% efficiency range. However, you have to know the amps. For instance, the JL slash series are about 50% efficient even though they are class D. Also, some companies use slow blow fuses. My USamps MD2D used a slow blow IIRC. A better ball park is to get a DMM with a clamp ammeter that can read RMS measurements and measure the current and voltage at around 60Hz. RMS Current * RMS Voltage = Apparent Power. As long as you dont have a lot of impedeance rise, apparent power is just a little larger than actual power.
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get the fuck out with that logic shit.
again someone steps in, and takes the fun out of things.