QuestionI have a Crest Audio CPX900 amp (Power Ratings: 8 ohms Stereo:180W; 4 ohms stereo:300W; 2 ohms stereo:450W). I have been using 2 Yamaha S115V speakers (8 ohms) successfully. Will the amp be able to handle it if I add 2 more of these speakers? How can you tell by looking at ohms and watts? By the way, the speakers power capacity is listed as Noise - 250W; PGM - 500W; MAX - 1000W. What does all this mean? Thank you!!!
AnswerHi Brent,
Thanks for sending a question with lots of details! Makes my life so much easier!
That said, the first question is whether or not your amp has hookups for two pairs of speakers, and if so, then the instant answer is "yes", as they would not build an amp to handle four if it couldn't. If you're thinking of hooking up two pair to just one set of plugs, that should be AVOIDED at all costs - you will definitely mess up the impedance, which will probably go over 8 ohms and the amp will not be able to drive them, or worse, can short out with too much power drain. So it's really as simple, if you don't have the manual for the CPX900 amp, to see if it has connections for one or two pair of speaker. If it only has one, then you shouldn't hook up two pairs of speakers: as said, the best case would be that the speakers will barely work, but you will likely fry the speakers and possibly the amp. Under-driving speakers can be really bad for them even if it worked.
To explain, the power ratings list impedance, which is how much resistance that the wires and circuitry of a speaker provides, and the higher the number, listed in "ohms", a term from physics, the more power it takes to drive the speakers, and hence the lower the max. power rating. In general, almost all speakers are 8 ohms because you need a lot of power to run decent speakers and get good sound, as well as to handle transients in volume, e.g. changes from quiet/loud that happen quite quickly.
As for your second question (in the future, please submit them separately, that way people can find answer more easily, but no problem with this) here's what the power capacity specs mean:
1. Noise: this is when a test signal of white (completely random) or pink (random but within a certain bandwidth of a minimum and/or maximum frequencies) sound is generated: that creates the most transients and really pushes an amp to its hardest in raising/lowering the power output. Hence the lowest rating in output: only 250 watts. Mind you, that's still three times (3x) as much as you need to run good speaker loud enough to cause hearing loss!
2. PGM - PGM is basically testing the amp playing normal music and other test recordings which don't have the kind of transients and such as the noise input. As such, the amp can drive higher amounts of power because the levels are more consistant. That's 500 watts, and far more than enough (my home system is 120 watts, 200 peak/max. and is far loud enough to cause hearing loss.)
3. MAX - This is the maximum amount of power the amp can put out if it has to. So if a signal requires up to 1000 watts of power, you amp can provide it - as long as it's not for long. The circuitry, as well as any cooling features, aren't designed to handle the full 1000 watt output for more than usually very short bursts of time, and if driven at 1000 watts for more than anywhere from a few seconds to minutes (you'd have to check the manual) it would fry the power supply or circuitry, or simply get the amp so hot that wires would melt.
So the important number is the PGM, which is what the amp can drive constantly without risk of over-heating or burning anything out, which is 500 watts. If the music you're playing suddenly needs 1000 watts, it can handle up to that, but again, only for brief periods. A good amp like this will have a fuse that will click off/burn out before anything fries, I'm sure. So you really have 500 watts to work with, but a peak of 1000 watts in case there's a sudden, brief change from very quiet to loud, and 500 watts is plenty: as said, my system is 120 watts and I think anything over that is unnecessary.
I say this just to give a warning: if you have speakers that can handle 500 watts of output (I think those Yamahas are pretty loud) - you can do serious damage to your hearing. And if you're a music nutter like I am, that's the last thing you want to do. So keep it turned down, or if, like myself, you feel the urge to crank it up and rock out to really loud music, limit yourself to no more than 90 minutes at a time to avoid ear fatigue and potential permanent damage. The last thing you want is needing a hearing aid before you're 80 years old! Good luck and have fun! Cheers, Wink
