2x12 vertical metal grill halfback cab with Mark V

[Boogie Fan]

Hi all,

Got a dumb question regarding ohms in regard to one of those vintage Mesa 2x12 veritcal cabs with the metal grill that I am aquiring to use with my Mark V. Forgive me, but I'm clueless when it comes to ohms. The cab in question has the original 8 ohm Mesa (Celestion) Black Shadow on top and the original 8 ohm EVM 12L on bottom. With that being said, should I run this cab at 4 ohms with my Mark V or is it okay to run it at 8 ohms? Sorry for my ignorance. Thanks!

 

[edmiller9999]

The back of the cabinet should ALWAYS specify the ohm load of the total cabinet. Just match them up and remember this simple formula.

1/R = 1/R1 + 1/R2 +1/R3 ... +1/Rn

or

one over the inverse of total ohms (R) equals the inverse of the sum of the individual ohm loads.

Sorry if my frustration is coming through, but I've been a board member for a month or so and this question comes up so many times, I just had to vent.

Ed

 

[ixoye777]

That's one of the most confusing things I've ever read.

 

[Boogie Fan]

That's one of the most confusing things I've ever read.

Yeah, it didn't help me much either. I can't believe I've had over 30 views but only one response, with it being a scientific equation. I know there are others here who own this cab. I figured that I'd get a response from someone that has it. I even called Mesa and spoke to a tech, and he didn't sound like he was absolutely sure...even after I explained what I had. I just find it to be a bit confusing. I've learned a little more since I made my original post, but still don't totally understand it. It appears that both 8 ohm speakers are wired in parallel with a white wire going from one positive terminal of a speaker to the other positive terminal of a speaker to the jack, while a black wire does the opposite. (from one negative terminal to the other, to the jack) So, if I have this correct, the two 8 ohm speakers wired in parallel should equal out to a 4 ohm load from the MKV. Just like most current 2x12 mesa cabs seem to come with 16 ohm speakers which equal out to a 8 ohm load....right? What would happen if I had an 8 ohm load from my MKV going to the above described cab? (w/ two 8 ohm speakers)

 

[thunder100]

Hi

Look here

http://www.300guitars.com/articles/impedance-speaker-cabinet-wiring/

Roland

 

[edmiller9999]

Sorry for being a prick. I'm originally from NY and have a scientific/IT background and it gets in the way sometimes. But I'll give you a really quick/cheap solution. Got to a Radio Shack and buy a CHEAP multi-meter for ten bucks and have them show you how to read ohms. It will become invaluable over the years to help you diagnose individual and series/parallel speaker loads. Once you open that door, you'll realize just how simple this part of the process truly is.

Apologies, again..... Ed

 

[SBG200]

Hi all,

Got a dumb question regarding ohms in regard to one of those vintage Mesa 2x12 veritcal cabs with the metal grill that I am aquiring to use with my Mark V. Forgive me, but I'm clueless when it comes to ohms. The cab in question has the original 8 ohm Mesa (Celestion) Black Shadow on top and the original 8 ohm EVM 12L on bottom. With that being said, should I run this cab at 4 ohms with my Mark V or is it okay to run it at 8 ohms? Sorry for my ignorance. Thanks!

Well in any event, you definitely don't want to run it at 8 ohms unless you want to purposely run a mismatch. There's no way you can get 8 ohms out of a cab that has two 8-ohm speakers in it, unless you're running only one of the speakers.

There should be a plate on the back of the cab saying what the load is. If not, you can tell by the wiring. If there are four wires running off the input jack within the cab, two running to each speaker, then it's running in "parallel" so it's 4 ohms total. Think of it as the current going into the cab being split in half so 8 ohms / 2 = 4 ohms. If there are only two wires total coming off the jack, one going to one speaker and one going to the other, with the speakers themselves joined by a 3rd wire, then it's in "series" so you add the ohms of each speaker together, in your case 16 ohms. In this case the current is coming from the amp, running into one speaker first (seeing 8 ohms), then the other speaker (another 8 ohms) before running back out.

Without seeing it, I'm guessing it's probably in parallel (4 ohms) since I'm pretty sure Mesa doesn't usually offer 16 ohm taps on their amps (I may be wrong--I don't know about the older stuff).

Hope this helps.

 

[babow2]

I have one of those cabinets. If it is still stock, the mono input is 4 ohms, so you run the 4 ohm output from the MV into the 4 ohm single input.

 

[Boogie Fan]

I have one of those cabinets. If it is still stock, the mono input is 4 ohms, so you run the 4 ohm output from the MV into the 4 ohm single input.

Thank You!

 

[Neptical]

Wow--all that just to tell the dude "4ohms".

~Nep~

 

[edmiller9999]

That's a very helpful post Nep. Forgive me for trying to actually HELP someone. Geez.

 

[ixoye777]

I think he meant this whole thread in general. It took all these replies from various people just for the OP to get "4 Ohms" :lol:

 

[domct203]

That's a very helpful post Nep. Forgive me for trying to actually HELP someone. Geez.

Wow man, lighten up a bit and don't take things personally.

Dom

 

[igfraso]

That cab is a 4 ohm. Run it through the 4ohm jack in the Mark V.