I know shit all about speakers but I do know that you have to run your cab at the same ohm level as your power amp. I was thinking about buying a Marshall 8008 and saw that the impedance is 4 ohms. Went to look at 4x12 cabs on ebay and saw that most of them are 8 and 16 ohms. Is there a switch or something that lets me run the 8008 at different impedances or is there a way to switch the impedance on a cab?

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If the cab has an impedance selector, you can select the impedance. Sounds simple, I know, but its not a common feature. I know Crate Blue Voodoo cabs have these. If you get two 8 OHM cabs and link them together, I think you'll be running at 4 ohms total ( read up on this and know for sure ). Some amplifier heads are meant to push two cabs, and some cabs are meant to be used in a duo, and it seems like many manufactures just want you to buy a full stack ( not surprisingly ). Like my Crate Shockwave head : its really meant to push two 4 ohm cabs for a total of 2 ohms ( 350 watts at two ohms = intended impedance for the Crate ). It comes as no surprise that the corresponding speakers that Crate recommends are two BV cabs that run at 4 ohms apiece.

However if you get one 8 ohm cab you just have 8 ohms, and a decrease in volume. Avatar makes single 4x12 cabs in four ohms, Line 6 does too ( although they are'nt known for their cabs ). Ask around about cabs that run 4 ohms, if you are intent on just having one cab.

Alright let me get this straight I didnt/don't know shit about ohms and impedence, but ive been reading this basic electronics book and learned that ohms=resistance, one basic thing about ohms is 1-volt going through a 1-ohm cable will come out 1-amp (i think thats how it is) or 1-volt and 2-ohms will be .5-amp. About the whole cabs and head thing tell me if i got this right.

To use 1 4ohm cab you have to have a head of exactly 4 ohms.
To use 2 4ohm cabs you have to have a head of 2 ohms.
To use 1 8ohm cab you have to have a head of 8 ohms.
to use 2 8ohm cabs you have to have a head of 4 ohms.

Is this correct?

By the way is impedence the same things as ohms?

EDIT I fucked up, I switched volts and amps, I got it mixed up.

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Note to self: check with you guys before plugging my quarter stack in when I purchase it...

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You are correct, but also everyone remember that I'm running my Crate head, which runs either 2 or 4 ohms, through a Genz Benz 2x12 that runs 8 ohms mono, and it works. Granted it does'nt hold it together at higher volumes, but nothing exploded. I think what it is, if you have an 8 ohm head, you can't plug it into a 4 ohm cab or you'll blow something. Don't quote me on that.

Don't know if impedance is the same thing as ohms .... there I go not knowing things

if a 4x12 cab is stereo does it run the left channel on 2 speakers and the R channel on the other? Also, is it the higher the ohms is the louder it gets? Ohms is the amount of resistance, so 8 ohms would have more resistance meaning less amps will get through. So 4 ohms would have less resistance making more amps go through making it louder.

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Ohms is the measument of resistance, impedance is the term used to describe how much resistance something has, 'the amp had an output impedance of 4 ohms'. Amplifiers also have an input impedence, which depending on the impedance (resistance) of your pickups, will alter how loud you guitar sounds, just as a cab of different resistance will be of a different volume

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Think of the resistance as a large box, the heavier it is (more ohms, ie 16) the more energy you have to use to push it, whereas a low resistance would be easy to push. Same with amps, if the impedance of the cab is low, it'll be louder, but you run the risk of damaging the amp if you take it too low

With the stereo cab, it is usually split into 2 left speakers and 2 right, there'd be no point on top/bottom

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Thats correct although in an ideal situation, you'd match the impedances, either 8/8 or 4/4 ohm, cause then the amp will run at a nice level without being pushed too much

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So lets all just agree matching ohms is the best way to do it. Screw mixing ohms and all that confusing nonsence.

just found this http://guitargeek.com/chat/showthre...&threadid=46544

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My goal is still to have an Avatar 4x12 and a Vader 2x15, both at four ohms.

And a BBE Sonic Maximizer with subwoofer control