Roadster and 2 marshall cabs

[scruffydoo]

I know cab connecting seems to have been done to death but I still couldn't find a definate answer to how to connect 2 marshall cabs to a roadster, the cabs have 16 or 4 ohm mono jacks and 2 x 8 ohm stereo, the amp has 16, 8 and 2 x 4 ohm jacks.


I would have thought this would be a pretty common setup but there's nothing in the manual about this (other than using an 8ohm series box which I'd rather not) and nothing came up in a search either, any advice ? :?

 

[jdurso]

I know cab connecting seems to have been done to death but I still couldn't find a definate answer to how to connect 2 marshall cabs to a roadster, the cabs have 16 or 4 ohm mono jacks and 2 x 8 ohm stereo, the amp has 16, 8 and 2 x 4 ohm jacks.


I would have thought this would be a pretty common setup but there's nothing in the manual about this (other than using an 8ohm series box which I'd rather not) and nothing came up in a search either, any advice ? :?

set your cabs to 4 ohms and connect the (2) 4 ohm outs from the roadster and send one to one cab and one to the other

 

[scruffydoo]

thanks, I thought so myself as its the most obvious but the manual suggests either

or

option 2 is no good as the marshalls only have the 8 ohm stereo option which leaves option 1 which means using a series box. Any ideas ?

 

[Geiri]

Trade the marshalls for mesa

 

[MrMarkIII]

The jacks labeled "4 ohm" DO NOT mean you plug a 4 ohm cab into them. If you do so the total load will be 2 ohms, dangerously low. They still want an 8 ohm load (in each 4 ohm jack). Thank Mesa for the confusion.
Daisy-chain the Marshall 16 ohm cabs (2 x 16 paralleled = 8 ohms), then plug them into the 8 ohm jack.

AMP > CAB > CAB.

Here's a calculator for speaker impedance matching:

http://colomar.com/Shavano/impedance_proc.php

Values entered horizontally are for series connections.
Parallel connections are entered vertically.
Be sure to show all your work. This will be on the final.

 

[willie]

I have a triple rec and 2 marshall cabs. A year ago I looked in the mesa manual and found that you have to use the two 4 ohm jacks out of the head and then plug them into the 16 ohm jacks on the cabs. Going out two 4 ohm jacks into two 4ohm jacks will make 2 ohms and be bad for the transformers. If only these heads had two 8 ohm jacks instead of 1 so we could do a perfect match instead of a safe mismatch.

 

[Jay22]

Man, this **** is goofy. I was meddling around with this too.
I have one marshall cab. I run it mono @ 4ohms into the 4ohm jack on the back of my triple rec.

At practice we have like six cabs and everyone uses them. So I usually hook an additional 4x12 marshall cab up to my head as well. In order to follow the instructions, I have both cabs switched to stereo 8 ohms. I plug one cab into its left 8 ohm jack to the mesa's 4 ohm jack. I do the same with the second cab. If im not mistaken, the head sees this as one 4 ohm load, which is safe since Im connecting to the two 4 ohm jacks. WTF....

I've never seen anything like this on a head before. It gets confusing and im still not 100% sure im doing it right. I really wish I could run both cabs mono without getting a **** breakout box. Apparently I cannot.

And btw, doesnt setting a switch on the back of a marshall to stereo only allow two of the speakers to operate inside the cab instead of all four?

 

[MrMarkIII]

Man, this sh!t is goofy. I was meddling around with this too.
I have one marshall cab. I run it mono @ 4ohms into the 4ohm jack on the back of my triple rec.

At practice we have like six cabs and everyone uses them. So I usually hook an additional 4x12 marshall cab up to my head as well. In order to follow the instructions, I have both cabs switched to stereo 8 ohms. I plug one cab into its left 8 ohm jack to the mesa's 4 ohm jack. I do the same with the second cab. If im not mistaken, the head sees this as one 4 ohm load, which is safe since Im connecting to the two 4 ohm jacks. WTF....

I've never seen anything like this on a head before. It gets confusing and im still not 100% sure im doing it right. I really wish I could run both cabs mono without getting a **** breakout box. Apparently I cannot.

And btw, doesnt setting a switch on the back of a marshall to stereo only allow two of the speakers to operate inside the cab instead of all four?

Yes, switching to "stereo" only utilizes two of the speakers. Remove the back of your cab and take a look. All four speakers are 16 ohms each.
Series-parallel gives you a 16 ohm cab. (16 ohms + 16 ohms in series = 32 ohms. Two 32 ohm loads in parallel equals 16 ohms.)
All parallel gives you a 4 ohm cab.
Stereo (split) gives you an 8 ohm half-a-cab (two 16 ohm speakers in parallel = 8 ohms).
Not to repeat myself, but daisy chain the two cabs like this: 16 ohms --->16 ohms.
Then plug this combination into the 8 ohm jack. 16 ohms + 16 ohms parallel equals 8 ohms.
Or, plug one each 16 ohm cab into each one of the 4 ohm jacks.
This also equals 8 ohms total.

The two jacks labeled "4 ohms" are meant to be used with TWO 8 ohm cabs, although ONE 4 ohm cab plugged into ONE "4 ohm" jack is a safe mismatch.
A 4 ohm cab plugged into EACH "4 ohm" jack will be 2 ohms total, which is too low.

 

[Jay22]

Man, this sh!t is goofy. I was meddling around with this too.
I have one marshall cab. I run it mono @ 4ohms into the 4ohm jack on the back of my triple rec.

At practice we have like six cabs and everyone uses them. So I usually hook an additional 4x12 marshall cab up to my head as well. In order to follow the instructions, I have both cabs switched to stereo 8 ohms. I plug one cab into its left 8 ohm jack to the mesa's 4 ohm jack. I do the same with the second cab. If im not mistaken, the head sees this as one 4 ohm load, which is safe since Im connecting to the two 4 ohm jacks. WTF....

I've never seen anything like this on a head before. It gets confusing and im still not 100% sure im doing it right. I really wish I could run both cabs mono without getting a **** breakout box. Apparently I cannot.

And btw, doesnt setting a switch on the back of a marshall to stereo only allow two of the speakers to operate inside the cab instead of all four?

Yes, switching to "stereo" only utilizes two of the speakers. Remove the back of your cab and take a look. All four speakers are 16 ohms each.
Series-parallel gives you a 16 ohm cab. (16 ohms + 16 ohms in series = 32 ohms. Two 32 ohm loads in parallel equals 16 ohms.)
All parallel gives you a 4 ohm cab.
Stereo (split) gives you an 8 ohm half-a-cab (two 16 ohm speakers in parallel = 8 ohms).
Not to repeat myself, but daisy chain the two cabs like this: 16 ohms --->16 ohms.
Then plug this combination into the 8 ohm jack. 16 ohms + 16 ohms parallel equals 8 ohms.
Or, plug one each 16 ohm cab into each one of the 4 ohm jacks.
This also equals 8 ohms total.

The two jacks labeled "4 ohms" are meant to be used with TWO 8 ohm cabs, although ONE 4 ohm cab plugged into ONE "4 ohm" jack is a safe mismatch.
A 4 ohm cab plugged into EACH "4 ohm" jack will be 2 ohms total, which is too low.

Well, these cabs do not have an "out" jack, so I dont think you can daisy chain them. Also that would still have the same result. Four speakers total.

Im going to check into a breakout box because I would like to run two full cabs. Anyone know where I can get one of the parallel boxes that are in the manual? I searched for a bit and cannot find it. I dont even know what its really called.

 

[jerseydrew]

Correct me if I'm wrong, but I think this would be a perfectly safe mismatch. Plug your speaker cables into the 16ohm jacks of both your Marshall cabs. Plug the other end into each 4 ohm jack on your Boogie.

Your amp will see the cabs running at 8 ohms because you're using two 16ohm cabs. Your amp will be running at 4 ohms. This should work. Much safer than running your amp at 2 ohms if you plugged into the 4 ohm jacks of your cabs.

Anyone?

 

[Jay22]

My head actually has two 8 ohm jacks as well so if I ran it that way, I could do a perfect match and run the head at 8 ohms while running both cabs at 16 ohms each, equaling an 8 ohm load. Im silly. I didnt even realize I could run the cab mono @ 16 ohms.