deville 410 and 1960a ohms

G

gitrokr

New member
i have a deville 410 which is 8 ohms, and a 1960a, either 4 or 16 ohm mono

i woud like to have the internal speakers of the deville plugged in and the 1960a plugged in to the extension cab of the deville? on the 1960a cabinet, do i need to have it on 4 or 16 ohms so as to not blow out my amp.

if worst comes to worst, i can unplug the fender speakers. and i think for this i would use 16 ohm on the cab right? kuz 4 would be too much.

add any comments that would help me, thanks alot
 
Does the DeVille have an extension speaker output? If it does, its probably parallel to the output for its speakers. Just calculate the total impedance of both sets of speakers.

Speakers in series:

R = R1 + R2 + R3 +....

Speakers in parallel:

1/R = 1/R1 + 1/R2 + 1/R3 +...
 
yes it is parallel, but i dont know how to calculate the impedances

for hte deville it is 8 ohm, but when a second cab is added it goes to 4 ohm since its parallel...but the question is, doexs it only go to 4 ohm when another 8 ohm cab is added? or can it be of a different ohm?

like, would it work if i kept i the internal speakers, and as the extension either 8 ohm stereo on the 1960a hooked up with a y cable, or the 16ohm on the 1960a?

thanks alot, please tell me what i need ot do to get thsi to work
 
Well, if you use the 16 ohm selection, you have:

1/R = 1/16 + 1/8
=
1/R = 3/16
=
R = 5.333 ohms

With the 4 ohm selection, you get:

1/R = 1/4 + 1/8
=
1/R = 3/8
=
R = 2.667 ohms

If your amp is looking for a 4 ohm load, then I believe you would be better off running the cab at the 16 ohm selection. Remember that a speaker's impedance is constantly changing...you're just given its nominal impedance.

Running the cab in 8 ohm stereo with a Y cable into both would be the same thing as running it in 16 ohm mono, I believe.

I've never opened up a Marshall with the impedance selection switch, but from what I've gathered/deduced, the cab has two sets of speakers, all 16 ohm, wired in parallel (IE: the left speakers are wired in parallel, and the right speakers are wired in parallel). This would give you the 8 ohms stereo. When you select the 4 ohms mono, the two parallel circuits are placed parallel to eachother, IE you have four 16 ohm speakers wired in parallel, giving a total impedance of 4 ohms). When you select 16 ohms mono, the parallel circuits are placed in series. The impedance of a series/parallel circuit where all resistances are equal is equal to the resistance of any of the speakers, so you would have a 16 ohm load.

I hope this makes sense, and someone who is more "in the know" please feel free to correct me if I'm wrong, because this is all supposition on my part.
 
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