New Amp and New Cab Day

[DrNewcenstein]

Picked these up from a guy at work:

Fender Rumble 25 bass amp:

And something a bit odd, IMO.

Mesa/Boogie 4x12, but with a square shell and slanted insides. All I've seen are square shells with square insides, never slanted unless the shell was slanted.

And the back is even more confusing......

Granted speakers are held in with screws and can be changed willy-nilly, but the Peavey 412MS jackplate? And the original plate seems to be missing from the bottom of the cab, where those jacks are.

I haven't taken it apart yet, so I don't know what's going on inside it.

 

[CTN]

Re: New Amp and New Cab Day

I've seen those mesa cabs with full slant construction (cab and inside baffle too).

They used to pack a real wallop.

Crappy about the "modifications" though. I'd get a nice baffle made for the back and re-wire the whole thing. Also, I'd get better speakers. The Sheffields aren't all that great.

 

[astrozombie]

Re: New Amp and New Cab Day

id put some vintage 30s in there.

 

[Ayrton]

Re: New Amp and New Cab Day

id put some vintage 30s in there.

Ding!

 

[DrNewcenstein]

Re: New Amp and New Cab Day

Ok, why V30s and not the originals?

 

[That90'sGuy]

Re: New Amp and New Cab Day

Ok, why V30s and not the originals?

Well, FWIW some Mesa cabinets do come with nothing, but Vintage 30s.

 

[DrNewcenstein]

Re: New Amp and New Cab Day

So I finally got a chance to dig this thing out of the closet and take a look. I also Googled them, and the speakers are reportedly comparable to Celestion M70s.

I'm concerned about the wiring though; the left top and bottom are connected, and the right top and bottom are connected. Haven't checked out the panel with the switch, so I'm not sure if it's set up for the mono/stereo like it reads, or if it was rewired as always stereo or what. Also not sure of it's wired series or parallel.

Each speaker says 16ohm, so if they're series I'd set my amp to 16ohm? Or is that for parallel, with series being 8ohm?

 

[CTN]

Re: New Amp and New Cab Day

series:
R total = R1 + R2 + .... + Rn

parallel:
1/R total = 1/R1 + 1/R2 + .... + 1/Rn

ie. if two 16 ohm speakers are in series, the total impedance is gonna be 32 ohms.
in parallel, it'd be 8 ohms.


You should probably check out the wiring and figure out exactly what's going on before plugging your amp in and potentially burning up transformers...

 

[Ascension]

Re: New Amp and New Cab Day

May be wired series parallel and if so would be 16 ohms. That would be ether 2 wired in series for 32 ohms and then the pairs wired parallel which would be a common way to wire a mono 4/12 with 16 ohm speakers. The other way would be to wire the 2 16 ohm speaker in parallel for 8 ohms then run the pairs in series to bring it back up to 16 ohms. This is the way a mono stereo 4/12 will normally be wired and a simple on off switch would be used to break the series link and split the jacks.
Yes by all means check the wiring on that cab as if it's wired wrong it could nuke your amp.
With that closed bottom open top I would bet a set of WGS's using a pair of Vet or Retro 30's on the bottom and a pair of ET's on top would absolutely be earth shaking in that cab. I'm running the little Zinky out many times with the ET 90 in the combo on top of a 1/12 cab with a Retro 30 and the tones are absolutely jaw dropping from that speaker combo!

 

[DrNewcenstein]

Re: New Amp and New Cab Day

Thanks. Gonna give it a closer look this weekend.

I should be able to stick a cable in the cab jack (no amp) and read the impedance with a meter on the tip & sleeve, right?