“I recently upgraded my PA from a pair of speakers rated at 150 watts to a pair rated at 350 watts. I intended to upgrade my 150 watt power amp as well, but in the meantime I’ve done a couple of gigs and not only do the new speakers sound better, but they seem to be louder using the same 150 watt amp. I was told once that I should match the amp to the speakers, but with this improvement I’m not sure I need to do anything. What do you think?”
There are several reasons why the new speaker my seem louder. The two most likely are some combination of lower impedance and higher sensitivity. There seems to be a lot of confusion about speakers and amps in our business. It’s not really necessary to have speakers rated at the same wattage as your amp. Our general rule is not to mess with what works; however, you may still find more improvement by getting a bigger/better amp. The amount of wattage you need/use depends a lot on how loud you play, the dynamic range of your material, the frequency range that must be amplified, the size of the room, the sensitivity of the speakers, and probably several other things I can’t think of off the top of my head: suffice to say there are many variables. So it’s not an exact science. The general rule of thumb is that an amp should be rated at about double the power of the speaker it must drive. This mostly comes from the knowledge that it’s actually more risky to the speaker to underpower it than to overpower it. A clipping amplifier produces square waves, which to a speaker are like a DC voltage, and this is not good for a speaker. In fact, more speakers are blown each year from this than from being sent too much clean power. So the idea is that if you use a larger power amp than you really need you get a couple of great benefits: 1) You reduce the risk of clipping and hurting your speakers, and 2) you end up with a lot more headroom and dynamic range available, which enables your system to reproduce transients much more effectively and with less distortion, which in turn just makes things sound better and reduces ear fatigue in the audience. Do you NEED a bigger amp? Hard to say for your specific situation, but I speculate it would be a good idea based on the above. Now is the time to call your Sweetwater Sales Engineer and let he or she probe deeper into your exact circumstances.