How to wire a powerful amp with two speakers to avoid damage

Just one more tidbit: why do underpowered amps potentially damage speakers? The reason, as previous posters pointed out, is that they are more likely to go into clipping in the listener's quest for louder sound. Nearly all of the power in a music signal is in the bass and low midrange. When the signal is clipped, this distortion generates an abnormally high proportion of power at high frequencies. So even though the total signal power can't increase (the amp is clipping because it's reached maximum output power), more and more of the power is appearing in the high end of the frequency spectrum. That's part of why it sounds so bad. Plus, it's this abnormally high power in the upper midrange and treble pouring into the tweeter that burns it out. The voice coil in the tweeter is sized for "normal" amounts of power in the treble range. Clipping causes abnormally high levels of power in the treble range, overheating the tweeter voice coil and causing it to fail. Next to go is the midrange speaker's voice coil. It's beefier than the tweeter, but still relatively wimpy compared to a woofer voice coil.

Bottom line: I agree with previous posters and would not worry about hooking up 75 W amps to speakers with a labeled rating of 25 W. I would be cautious, though, and start with the volume turned ALL the way down, and cautiously raise it, listening to see how the speakers react. At the first hint of distortion, back the volume down IMMEDIATELY.

Thank you, 1439bhr, for the excellent explnation as to the damage caused by under powered amps. I like to see posts that explain why things happen so that everyone can better understand what is happening inside their 'black' boxes. I hope to see many more posts from you. Chris

Angela touches upon an interesting point, although the issue, I believe, is not the danger of the amps working really hard at not delivering the current, but rather, the amps not being allowed to work hard enough to be in a confortable, never mind ideal operating range.

Every component has an ideal operating range, and while I agree with everything that has been said already as concerns the issue of potential damage, the matching of components with concern to this issue is IMHO one of the keys to really musical sound from a system. It's kind of like my SAAB Turbo; at 25 mph it's great, but at 50 mph+ you just sense that the motor is happier and performing at closer to full potential.

Most amplifiers supply voltage to the load (speakers) and the impedance of the speakers at the frequency being reproduced determines the amount of current flowing. A battery is also a supplier of voltage to a load. The bulb of a flashlight uses less current than a headlight of a car. An amplifier is like a battery and is happy to deliver whatever current is needed up to the point of its max output current.

The only other factor that effects both the battery and an amplifier is heat. Automotive batteries can supply much more current at 25 deg C than at 0. An audio amplifier usually sounds better after it is warmed up and is probably the main concern in an over powered "class AB" amp. A high bias amplifier should not have any problems driving even a pair of headphones because the high bias will keep the amp warm even with no signal applied.

The analogy of an amplifier and a car is not correct because an audio amplifiers voltage and current are a linear relationship while the RPM and torque curve of an engine is not.