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impedance question

Hi I'm trying to understand ohm's and power. My b&k 200.5 is rated at 200 watts per channel at 8 ohms and 375 at 4 ohms. Now some of my speakers are rated 4 ohms and some are rated at 6 ohms. My question is does the amp just feed the power differently to each speaker accordingly? ie, 4 ohm speaker will receive 375 watts and the 6 ohm somewhere between 200-375?

2nd question is i had my sub woofer wired parrellel to my mains, everything seems to be working fine but I just read that I really put a load on my amp by dropping it to 2 ohm? is this correct? Is this a bad thing to do? I don't know how else to wire my sub because for some reason my rca sub output on my receiver doesn't seem to work. any suggestions?
monterey
monterey OP
31 posts
 
Hi it is a self powered sub. In fact 1500 watts!
monterey OP
31 posts
 
I don't know why my sub output on my pre amp doesn't work. I just tried again and get nothing. Next question is there's a switch on the sub, since I'm feeding it from my mains do i select the LF filter "active" or "off"?
tpreaves's avatar
tpreaves
2,687 posts
 
Read your manual. If you don't have one, do a Google search, I'm sure you can it somewhere. Good luck.
blkadr
739 posts
 
I once upgraded from a 200wpc amp to a 100wpc amp. The lower powered amp had much better bass. I have two pairs of speakers both rated 86db/6ohm. My 12wpc t-amp makes nice music with one, sounds shut in and anemic with the other. My buddy's Bedini 25/25 sounds awesome with Totem Ones, a speaker that can make many more powerful amps (wpc) sound constrained.
There is so much more going on beyond wpc and impedance ratings. They can only give you a limited idea about how an amp will power a speaker.
magfan
1,583 posts
 
The speaker level inputs on your sub should have very high input impedance and will not draw power from the amp OR effect it's ability to drive low impedance loads.
You could, if you wanted to run the mains full range, just wire them as normal and a 2nd set of speaker wire...and it could even be magnet wire, to the inputs on the sub.
You'd know if you were loading your amp to 2 ohms or less. It'd get real hot, pretty quickly and/or simply would not be able to play very loudly.

Speakers ONLY draw what power they need, to the electrical limits of the amp. Power 'ratings' on speakers? Sort of a weird science thing. Better watts....are better.

Adjust the phase knob after getting the main speakers running and at maximum perceived bass. Just swap +- lead on ONE speaker and if bass disappears / diminishes put it back and forget it. Than add the sub to the equation, adjusting the phase knob until you get max bass again. It's lowest level should be 180 degrees from the maximum level.

If you are dealing with a HT receiver, you are doing something wrong in the 'setup' menu. Set speakers to 'large' or 'small'.....that sort of thing. I'm not an HT guy.
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