There have been some questions about amp power and speaker power ratings and how to match them up lately... I answered a PM about the topic and the person had no problem with me posting the answer to see if anyone else found it interesting...


No problem. Glad to help.

1) No, you do not need to power them with exactly that much power. Theoretically, that is the maximum you should power them with if they are playing "full range" - that is, without a crossover taking out all the lowest sub-bass notes. If you put such a high-pass crossover on any cone-type speaker, its power handling ability goes way up. The lower a bass note, the farther a speaker cone has to travel - so if you limit the lowest bass, you limit the amount of travel, and thus, voila! Higher power handling!

2) Infinity Kappas have a history of being relatively inefficient speakers. Ignore the efficiency ratings on the side of the box - they are all marketing-department lies nowadays. Inefficiency is not bad - it's common in high-end speakers - it just means that your speaker has a heavy cone material (common in stiff cones) and a stiff suspension (common in high-power-handling speakers). This is why better speakers (MB Quart, Focal, Dynaudio, SEAS, Scan, etc.) require amps to sound good, while cheaper speakers sound OK with deck power.

3) It is always easier to "blow" a speaker with a small amp than with a big amp. Why? Because when you turn up the volume to a point that requires more amp power than you have, your amp starts "clipping" - that is, generating lots of distortion during the musical signal peaks that it can't reach due to its power ceiling.

If you select a volume that with a particular song has moments requiring 40W, and you only have 30W, your amp will generate tons of additional distortion (with lots of DC in it) when asked to exceed its 30W power ceiling. Distortion and DC blow up speakers.

Ever use a 9V DC battery to "pop" a speaker? It pushes as far away from the magnet as it can, and stays there. That's what DC bursts do to speakers - and that's what eventually blows the voice coil motors inside. The DC can even cause the speaker suspension to rip apart in extreme cases.

So if you connect your Infinity Kappa 6x9s to a big amp, even one bigger than the power rating, you should be fine IF you turn on the crossover and high-pass the speakers at 50 Hz or so.