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Unread 06-11-2008, 11:41 AM   #1 (permalink)
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Tsl602 -> Vs412?

Hi,

About 10 years ago I bought a Marshall Valvestate head and 4x12 cab.

Unfortunately the head was stolen, so I've had this VS412 cab knocking around for years.

A few months ago I bought myself a brand new JCM2000 TSL602 2x12 combo.

Is it possible to use the cab with the combo?

The cab says 140W @ 8 Ohms.
The combo says 60W RMS 8/16 Ohms (with a switch) and has 2 speaker outs - one with the internal speakers plugged into it and one vacant socket.

The switch is currently in the 16 Ohm position. If I change this to 8, does it change the send to the internal speaker to 8 Ohms too or is that socket always fixed at 8?

Has anyone done this before? How did it sound?

If it doesn't work as-is, has anyone successfully modded a VS cab to make it work with a JCM combo?

Thanks in advance.

Phil, 32, Stafford, England, UK.
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Unread 06-11-2008, 01:00 PM   #2 (permalink)
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Re: Tsl602 -> Vs412?

Since the internal speaker is 16 ohms, and the external cab is 8, you cannot use them together, as is.

The two speaker jacks on the amp are wired in parallel, so both speakers together would combine like this (*warning*math ahead):

1/Rtotal = 1/R1 + 1/R2
1/Rtotal = 1/16 + 1/8
1/Rtotal = 1/16 + 2/16
1/Rtotal = 3/16
Rtotal = 16/3
Rtotal = 5.33 ohms

Since your amp does not have a selection for 5.33 ohms on the impedance switch, you cannot use the cab and internal speaker together.
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Unread 06-11-2008, 03:13 PM   #3 (permalink)
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Re: Tsl602 -> Vs412?

Hi, and thanks for replying.

Is there a way of rewiring the speakers in the cab to make it 16 ohms?

If the cab was 16 ohms, does that mean I could plug it in to the combo with the switch on 8 ohms?
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Unread 06-11-2008, 03:20 PM   #4 (permalink)
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Re: Tsl602 -> Vs412?

Could I just solder in an 8 ohm resistor in the signal path?

How are the speakers wired in a VS412 cab? 2+2 or all in series?
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Unread 06-11-2008, 03:50 PM   #5 (permalink)
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Re: Tsl602 -> Vs412?

If the cab was 16 ohms, then you could use both, with the amp set for 8.

There is no way to re-wire it so that it is 16 ohms.

Do not wire in a resistor.

Why don't you just unplug the internal speaker, and use the cab by itself?
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Unread 06-11-2008, 06:10 PM   #6 (permalink)
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Re: Tsl602 -> Vs412?

Quote:
Originally Posted by Adwex View Post
If the cab was 16 ohms, then you could use both, with the amp set for 8.

There is no way to re-wire it so that it is 16 ohms.

Do not wire in a resistor.

Why don't you just unplug the internal speaker, and use the cab by itself?
Genius!

Good plan, I'll do that.

Still seems a shame to have 2 speakers doing nothing though.
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Unread 06-11-2008, 09:37 PM   #7 (permalink)
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Re: Tsl602 -> Vs412?

I also have that cab, and a DSL401 which like your TSL, has a 16Ohm internal speaker and options for switching 8 or 16 Ohm out. It worked fine just through the cab, but I really like the sound of the internal Vintage 30 that i put in the combo, and I also like the extra bass that the cab can provide.

My answer was to take out two drivers from the cab, and blank them off with plywood panels. The remaining two are wired in series to make a 16Ohm 2x12 cab, with lots of cab volume available. The now 16Ohm closed-back cab combines very well with the 16Ohm combo speaker, for a combined total of 8Ohms set on the amp.

It works great and sounds huge.

John
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Unread 06-12-2008, 06:12 AM   #8 (permalink)
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Re: Tsl602 -> Vs412?

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Originally Posted by JohnH View Post
I also have that cab, and a DSL401 which like your TSL, has a 16Ohm internal speaker and options for switching 8 or 16 Ohm out. It worked fine just through the cab, but I really like the sound of the internal Vintage 30 that i put in the combo, and I also like the extra bass that the cab can provide.

My answer was to take out two drivers from the cab, and blank them off with plywood panels. The remaining two are wired in series to make a 16Ohm 2x12 cab, with lots of cab volume available. The now 16Ohm closed-back cab combines very well with the 16Ohm combo speaker, for a combined total of 8Ohms set on the amp.

It works great and sounds huge.

John
Interesting.

Which speakers did you take out?

Did you experiment - taking out the top 2, the bottom 2, diagonals - and comparing the sound?
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Unread 06-12-2008, 06:14 AM   #9 (permalink)
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Re: Tsl602 -> Vs412?

Yep, I started with taking out a diagonal pair, but I found it a bit too boomy. Now I have the top two in and the bottom two blanked off, with a pillow in the base of the cab to make it sound tighter.

cheers

John
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Unread 06-12-2008, 07:14 AM   #10 (permalink)
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Re: Tsl602 -> Vs412?

Quote:
Originally Posted by JohnH View Post
Yep, I started with taking out a diagonal pair, but I found it a bit too boomy. Now I have the top two in and the bottom two blanked off, with a pillow in the base of the cab to make it sound tighter.

cheers

John
Cool, thanks mate, I'll give it a go.
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Unread 06-12-2008, 10:33 AM   #11 (permalink)
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Re: Tsl602 -> Vs412?

Removing/disconnecting speakers is a good solution to match impedance, but only if you don't mind losing the extra "oomph". Adding speakers is better, but not always in the budget.
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