what to look for when buying an amp?
 

Going through all the specs on different amps I get a little lost. So I am asking what in important . I see thd**% alot and high/low crossover, and different frequencys alot. What does it all mean.

THD is total harmonic distortion. Basically, the lower the better. But realize that harmonic distortion is much less of an issue in subs than in mids and highs. 1% THD is the generally accepted standard for good quality. It takes more than that to damage speakers through distortion, and even more to damage a sub. Most amps are right around the 1% mark.

Crossovers - your best bet is to get an amp with a variable crossover, IMO. If this is a sub amp, you'll use the low pass to cut out all the upper frequencies, and if it's for mids and highs, you'll use the high-pass to cut the bass. Again, a general rule of thumb is 80Hz cutoff. But because every sub, speaker, enclosure, car, and system is different, a variable crossover gives you the ability to tune your system to fit your needs. If you don't pump the volume like mad, your sub might be able to take being crossed at 100 or even 120 Hz for some extra mid-bass. Conversely, if you like to blast your shit, your interior speakers might need to be crossed higher than 80Hz to remove more bass and allow higher volumes without distortion. Variable crossovers give you this flexibility.

Other than that, sticking with good name brands is the best bet from a power and value aspect. Quality amps can put out MORE than the power they advertise, meaning that if your amps says it'll do 500 watts, you don't need to crank it all the way up (which is when horrible distortion sets in) to get that power. Good amps will put out the rated power with low distortion, because the actual max output is more than it's rated power.

Hope this helps some.

~HH

rms power output at 12 and 14 volts
highest rms power output impedance, to match the subs
adjustable crossover range and flexablility
bandpass crossover
crossover db/octive
damping factor
power at less than 1% THD