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Amps, Watts And Ohms

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Hi all!!


Long time since I've been on here so I appologise!


I've got a question that I'm struggling to find an answer for and I'm hoping someone on here can help.


I've just upgraded my PA with 2 x 600W at 8 Ohm subs with built in crossovers (Passive), I want my amp to go straight into these then out into the tops (2x 400W at 8 Ohms). I understand this will change the resistance from 8 Ohms to 4 Ohms but what I need to know is what size amp (@ 4 Ohms) do I need?

My current amp is rated at 550W per channel at 4 Ohm so I assume this is underpowered?


I looked round the internet and it's not an easy find!! :wall:



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My current amp is rated at 550W per channel at 4 Ohm so I assume this is underpowered?


Yes, (2x) 8 ohm speakers connected to each channel in this manner, would present a total load of 4 ohms to each channel of your amplifier


There isn't really such a thing as 'underpowered' any more than it would damage a 180mph super car being driven at 40mph :D . Technically you could drive these speakers from a 200W @ 4 ohm amplifier if you wanted to, although it would severely lack 'ooomph' or any real bass depth, and you'd probably be thrashing it to within an inch of its life.


But suffice to say that you wouldn't be getting anywhere near to the full potential from your speaker capacity with your current 550WPCH amplifier.


Personally, i'd be looking for an amplifier rated at least 900w to 1000w RMS per channel @ 4 ohms - assuming your speakers are rated in RMS and not peak or maximum figures


Then again, it all depends on the venues and sizes of crowds which you play to, if you are adequately coping with the venues you get booked to play in, with your existing speaker and amplifier combination, then why fix what isn't broken?. However if you are often running your amplifier at close to full power, gig in - gig out, then yes, its time to increase the capacity and headroom from your amplifier.

Edited by McCardle

"The voice of the devil is heard in our land"


'War doesn't determine who is right, war determines who is left, and you wont win this war.'

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