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In general what are the rules/ principles of selecting an amplifier for multi subs?

for example: lets say you have 3 4ohm dvc's that are rated at 500rms


if you run them at 2.67 ohms, would you then look for a compatible amplifier that will produce 500 rms @ or around 2.67ohms or would it require an amplifier that can produce 1500 watts @ or around 2.67 ohms?

you would want one that does 1500 at your ohm load, in this case if you have the room it might be more economical to run 4 subs as it will be cheaper to buy a 4th sub than it will be to buy an amp that does 1500 at almost 3 ohms....whereas one that does 2k at 1 ohm is going to be less expensive usually or you could try running at .67 ohms and see if the wire adds enough resistance to get the dc impedence up around 1 ohm and then the amp should be fine because the dc measurement will change while the speaker is playing...but then again there are a lot of amps out there like the audiopipe ap30001d that will do more than that for a decent price, i sell it for 500 and it is a dual mono block that does 3k rms at 2 ohms

If each sub is rated at 500rms, then to give them their rated rms, you will want something that does 1500rms at that load. However many subs you are running, at up the rated rms on all of them and that is the amount of power you will want to give the subs their rated rms.

3 subs one amp = badnews.

Not neccessarily Bill... I know that the Memphis Amps were completely capable of handling 3 subs at that configuration... In fact i know a friend of mine was running 3 Infinity Kappa Perfects 12" on a Memphis 1500w amp... Killer Sound System in that lil shit box he had lol

again i say 3 subs on one amp = trouble.

Bill, can you explain why, I"m curious? I had 3 4 ohm 12's running at 1.3 to my jbl 1201.1 for along time. Is it the uneven load it present to the amp??

its not that its an uneven load its just because all three of the subs have different DCR's so each gets slightly different power which can cause cancellations. and i guess thats just the spl guy in me trying to make everything perfect. but your better off just going with 2 subs or ideally one sub.

Thanks for all of the replies!!!

Well I do agree with the fact that 2 is better than 3 but... I dont have the SPL Knowledge to argue with that statement, even though im sure there are amps capable of creating even power distribution.