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Need help setting up amp and speakers

Z

zzr0ck3r

Mar 14, 2008
58
0
#1
Ok i understand lots of you are gonna say overkill but.... I just got new mesa boogie fathom and svt 8x10 i also have a swr big ben that i want to throw in the mix but dont know how to do so with my head. There is no biamp but can i still run it? If so how would i hook it up in the back? i dont know much about ohms and what not. ill add link to back of new head so you can see what im dealing with. ty in advance

http://mesaboogie.com/Product_Info/Bass_Amps/fathom/Fathom Rear-enlarged.htm
 
#2
Hmmm, the SVT cab is 4 ohms and the Big Ben is 8 ohms, correct? You should be able to hook them up, but the Big Ben is only going to get 1/3 of the power the SVT cab gets. However, that may be OK. You may end up liking the Big Ben not getting as much volume. Or you may find it a waste. Someone may want to spot me, but I think you should have the switch by the speaker jacks to 2 ohms if you do it.
 
#4
this thread was a big help for me for finding out about ohms and all that
http://www.talkbass.com/forum/showthread.php?t=144244 ...

And you'll like this part :p
"With a 4 ohm cabinet and an 8 ohm cabinet run in parallel the formula is 1/(¼+1/8). You can’t add ¼ to 1/8 without having the same denominator (I told you this was gonna sound like school), so you have to reduce ¼ to 2/8 so they match. Then adding 2/8 to 1/8 gives you 3/8, dividing 8 by 3 gives you 2.67. So, hooking up an 8 ohm cabinet and a 4 ohm cabinet in parallel to your amp gives the amp a load of 2.67 ohms to power. "
 
#9
Well, you may be OK. I don't know for sure. That's a new amp and I know nothing about it yet. From the looks of the description, it "optimizes" the amp for the impedance of your cab, whatever that means. It could be nothing or it could be something. It would have said it if had an output transformer, so that shouldn't be an issue, but you never know what new crap they're sticking in amps these days.
 
#10
yeah i think the dude is wrong at store. everything im reading says run it at 4.
the manual for the head even says at loud volumes at 2 ohms the head will auto shutoff itself to protect something.... so that dont sound like a good thing. Ok so just put the 4/8 ohm switch on and should i run 1 cord from each speaker out on head? or run one cord from head to 8x10 then another from 8x10 to 18?
 
#12
i dont know about the fathom, but for the 400+ i know the speaker outputs are a little funky.. there are two outputs that say 4 ohm above them, but they arent 4 ohm outputs, they are 8 ohm outputs... it means that to run the amp at 4 ohms, you should use both of the outputs under 4 ohms (which happen to each be 8 ohms).

i find that a stupid and confusing way to label the outputs.. they should just say what each output is.... but of course, this might not apply at all to the fathom.

if it DOES, then he may be running 4 ohms with his 8x10 even tho it says 2 ohms
 

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