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Help with rules on impedance....


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Ok, I came into a peavey pa-400. The wattage is 700 and the outgoing ohms are 2 ohms....as far as I know, no one makes 2 ohm speaker cabs. So, can I push 2 ohms into 8 ohm speakers. It just won't be as loud as it could be right? Also, what impedance do I use if I Daisey chain speakers? This pa will be for home use not public so getting as loud as possible is not a concern. Thanx for the help. Justin

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Wow, first of all, your PA-400 is rated at 200 watts into a 2 ohm load, about 125 watts into a 4 ohm load and about 80 watts into an 8 ohm load.

 

The speakers you have and how they are connected determine the load (impedance) that your amp sees.

 

If you have 2 x 8 ohm speakers, the standard connection when connecting together via the jacks provided is parallel, the total impedance would be 4 ohms and your amp will deliver 125 watts into 4 ohms, which will be split equally between the two speakers.

 

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The impedance rating on an amp is the LOWEST that it will drive (this is a figure some lo-ball manufacturers sometimes push to the edge for marketing purposes :-). Peavey is NOT generally one of the "spec cheaters BTW. That said, yes of course you can run an 8 ohm box from this amp. if you daisy chained two of those speakers (normal parallel connection) you get a 4 ohm load (conversely 4 x 8 ohm speakers = 2 ohms). The lower the impedance the more current you allow to pass through the amp (so yes - 1 speaker won't give you the full 700 watts). OTOH since we don't perceive acoustic power (wattage) in a linear fashion (twice the power only makes for 3 db more volume), the difference isn't huge (noticeable but not huge).

 

That's the basic idea of it. There are really a lot of small factors that don't make this an absolute rule (a lot more theory than is easily put into 1 post) but as a rule of thumb it's a simple way to look at it. Another rule of thumb is to be careful when you are approaching that lowest rated impedance number if you're going to push your amplifier near it's limits.

 

There's probably more info about this subject in one of the "sticky" posts at the top of the forum if you want to research it further.

 

Hope this helps

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