Hello, hope you can help with this one... Ive been to several shops recently and ive had different answers to the same question. I have a 200w per channel in to 4 ohm amplifier. I have two sets of speakers both 8 ohm. Put them in parallel you get 4 ohms. I accept this. But if one pair is 100w max and the other 200w max, Will the amp blow the 100w pair of speakers? One shop said... No, cos you've linked them together your ohmage goes down so that means the total power rating of the speaker as a system is 300 so the amp is too small. Second shop said that you halve the power of both speakers put together and that gives you your rating so 150w. He said keep the amp at about 3/4 output. But i'm not sure about either and im not about to blow some speakers to prove them right/wrong. I believe that it will blow the 100w speaker, am i right or is one of the shops right? Can anyone definitively explain what happens to power ratings when speakers are linked together?

You need to be looking at the RMS wattage that the speakers can handle.

If they are 100w max and 200w max then they are most likely around 50w and 100w RMS.

Assuming they are both full range, the power would be share equally between the speakers, i.e. they would get 100w each which could damage the smaller speaker.

It does depend on various factors though such as the make of the speakers and amp. More expensive speakers may be able to handle the extra power without a problem. Likewise a cheaper amp may not give out the full claimed power whereas a more expensive one will so its a bit of a lottery.

Setting the gain on the amp at 3/4 won't make any difference. You can still get the amp to output the full power by inputting a stronger signal into it from the mixer.

It also depends what you are using them for. As a vocal system they may well be fine but if being used for a disco, I suspect that you would end up pushing them pretty hard. Chances are the 50w (100w) speakers wouldn't be able to handle the load required.

That's spot on.

The other thing is, as has been mentioned by me and a couple of others, an amp driven to clipping in an attempt to get the most out of the speakers will be more likely to blow said speakers (both of them), than an amp of, say, double the power not stressing.

I wouldn't worry about blowing the speakers as long as you make sure you don't clip any part of the signal chain. If you notice that, without clipping, you can turn the signal up and the speakers don't get any louder, then turn the signal down until it makes a difference. Speakers will only go so loud before the power you're putting into them just gets turned to heat.