#1
Ok, so, first time actually using a head and speaker cab in a while since I've been practicing with my combo for about 6 months now, but, how would I hook up my Krank Krankenstein head out into a Mesa 4x12 and a Krankenstein 4x12 as far as the OHM rating goes?

Thanks for the help, I feel like an idiot for not remembering haha
#2
Quote by sdmf5150
Ok, so, first time actually using a head and speaker cab in a while since I've been practicing with my combo for about 6 months now, but, how would I hook up my Krank Krankenstein head out into a Mesa 4x12 and a Krankenstein 4x12 as far as the OHM rating goes?

Thanks for the help, I feel like an idiot for not remembering haha



Its always best to match impedance. So 4 ohm out -> 4 ohm input, 8 ohm out -> 8 ohm input, 16 ohm out -> 16 ohm input.

There's debate about mismatching impedance. Some people will tell you that you can safely match an amp to a load that is twice the impedance of the head's output - they call this a "safe mismatch". Other's will say that you can't because of factors such as arcing and something called flyback voltage or something like that.

I've talked to people who have been modding and building amps for 30 and 40 years (Dan Boul, president of 65 amps is one of them) and have been told that mismatching with both higher and lower loads than the heads output is perfectly safe, it just decrease the life of the tubes and the OT.

Best bet is to always match impedance - just keep that in mind.
#3
Alright, thanks a lot for that reply. Now, would it be best to run in parallell or series? And then if so how should I do the impendance, that's where my real question comes in.
#6
Quote by sdmf5150
Alright, thanks a lot for that reply. Now, would it be best to run in parallell or series? And then if so how should I do the impendance, that's where my real question comes in.


Parallel and series come into play when you're running multiple cabinets. If you're running parallel you want the cabs inputs to be twice of the output because the cab's rating gets cut in half - there's a nice math formula that explains it but I don't know it off the top of my head.

So two 8 ohm outs in parallel need to go into two 16 ohm cabs, two 4 ohm outs in parallel need to go into two 8 ohm cabs.


I have no experience running cabs in series. I know that when wiring speakers in series you add the ohms of the speakers together (i.e. two 4 ohm speakers in series equals an 8 ohm load) but I don't know how it applies to running cabs.
#7
Quote by i_am_metalhead
Parallel and series come into play when you're running multiple cabinets. If you're running parallel you want the cabs inputs to be twice of the output because the cab's rating gets cut in half - there's a nice math formula that explains it but I don't know it off the top of my head.

So two 8 ohm outs in parallel need to go into two 16 ohm cabs, two 4 ohm outs in parallel need to go into two 8 ohm cabs.


I have no experience running cabs in series. I know that when wiring speakers in series you add the ohms of the speakers together (i.e. two 4 ohm speakers in series equals an 8 ohm load) but I don't know how it applies to running cabs.


I think it doesn't matter, two 8 ohm cabs running in series will still be 8 ohms, because the overall load of both cabs is still 8 ohms.

Or it could add, I have no idea anymore either.
#8
@ ethan: they do add:

Rtot = R1 + R2 +...+ Rn

real quick, series/parallel. if you are connecting cabs to the head or daisy chaining cabs together then manufacturers exclusively use parallel wiring (no exceptions if know of) for a number of reasons, let me know if you care else i am not going into it. mind you, i am not including wiring speakers together in the cabinet, i am only talking about connecting cabinets in a circuit with a head.

@ TS: your mesa is 8 ohms, you krankenstein is 16 ohms. if you connect them, it will be in parallel, it will be a total load of 5.3 ohms.

1/8 + 1/16 = 3/16 = 1/Rtot

take reciprocal and you get: 16/3 = 5.333 ohms

now, the reason tube amps have a transformer is to maximize the power coming from the power section of the amp by changing the impedance from the power section to match the speaker cabinet. if you aren't matching impedance, then you are stressing the transformer...

but that is not even the real story, cuz speakers don't actually provide a single fixed 'impedance'. the very nature of impedance is variable (to many factors, including frequency of the input signal fed to the speaker). a speaker's impedance is more like:



that is a 4 ohm speaker's impedance curve btw. looks like when you play a low E on your guitar the speaker is actually providing a ~6 ohm load. when you play your high E it is only providing a 3.5 ohm load. (this is also not the whole story, because a guitar's signal is not just the fundamental, it is a more complex signal, but i am not going into that either).

this is a great article for a more complete story

http://en.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers

what would i do? i would make sure the speaker or cab i use covers the min nominal impedance expected by the head as speakers tend to provide impedance that is higher than normal and a head deals with it quite fine (as long as it isn't substantially larger than the nominal rating)

i_am_metalhead wrote a bunch of stuff i don't need to write now, he outlines the consequences well enough for casual conversation, small impedance mismatch isn't great but at worst will just stress the trannie or power section a bit. also, tone will suffer a bit for reason mentioned in the article i posted

one thing not mentioned is that a lower impedance cab will provide more volume than a higher impedance cab. so, basically, the mesa will sound louder than the krank; just because of how current flows.
punk isn't dead, it's always smelled that way.

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-ae
Last edited by gumbilicious at Jul 10, 2011,