Luthers Theory
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I have a Marshall 412 16 ohm bottom, a 212 8 ohm on top, and a dsl 100 head. Can I run both cabs at once being that the inpedence of the 2 cabs are different?
Cabinet conundrum
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RLW59
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JCM200 DSL100, no.
Current DSL100HR, yes. Plug the 16 ohm cab into one of the 8 ohm jacks and the 8 ohm cab into one of the 4 ohm jacks. "Two half loads equals a full load" -- it makes for an exact proper impedance load with equal power going to each cab.
Current DSL100HR, yes. Plug the 16 ohm cab into one of the 8 ohm jacks and the 8 ohm cab into one of the 4 ohm jacks. "Two half loads equals a full load" -- it makes for an exact proper impedance load with equal power going to each cab.
JohnH
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If you have that current model dsl100hr, with its set of 5 output jacks, then the idea as described by @RLW59 is a perfect solution. If its an older DSl with switches to set output ohms, then there are work-arounds:
If you just plug them both in then you have a 5.3 Ohm mismatched load. It's debatable if using the 4ohm amp setting, that causes any problem (I wouldn't do it). But maybe more significantly, 2/3 of the power will go to the 2×12, which may be enough to drown out the 4x12. So better options:
1. You could mod the amp to add a new output tap hardwired for 4 Ohms, then set the main output jacks for 8 Ohms and do as above , or;
2. Wire a 100W Aluminium power resistor in series with the 8 ohm 2x12. You could do this internally or as an external box. This will slightly reduce overall power to the speakers, slightly shift the tones but not much different. If that added resistor is 3.3 Ohm, then you get equal power to both cabs and an overall 6.6 Ohm load, close enough to use the 8 Ohm tap. Or if its an 8 Ohm resistor so the 2x12 now looks like 8+8=16, you get a good 8 Ohm overall load, with 2/3 going to the 4x12. This means each of your 6 drivers gets equal power. So somewhere 3.3 to 8 is good. Maybe 4?
3. Disconnect 2 of the 4x12 speakers and wire it for 8 Ohms. Use the 4 Ohm tap in combination with the 2x12. You can have the spare two drivers disconnected, disconnected but shunted by a wire (makes them move less, different tone), or remove them and leave the holes open (less bass) or blank them off with ply (more bass).
4. Get two new 8 Ohm speakers for the 2x12, wire them in series to make a 16 Ohm cab. Use the 8 ohm amp tap with both cabs together.
5. Just use the 4x12!
If you just plug them both in then you have a 5.3 Ohm mismatched load. It's debatable if using the 4ohm amp setting, that causes any problem (I wouldn't do it). But maybe more significantly, 2/3 of the power will go to the 2×12, which may be enough to drown out the 4x12. So better options:
1. You could mod the amp to add a new output tap hardwired for 4 Ohms, then set the main output jacks for 8 Ohms and do as above , or;
2. Wire a 100W Aluminium power resistor in series with the 8 ohm 2x12. You could do this internally or as an external box. This will slightly reduce overall power to the speakers, slightly shift the tones but not much different. If that added resistor is 3.3 Ohm, then you get equal power to both cabs and an overall 6.6 Ohm load, close enough to use the 8 Ohm tap. Or if its an 8 Ohm resistor so the 2x12 now looks like 8+8=16, you get a good 8 Ohm overall load, with 2/3 going to the 4x12. This means each of your 6 drivers gets equal power. So somewhere 3.3 to 8 is good. Maybe 4?
3. Disconnect 2 of the 4x12 speakers and wire it for 8 Ohms. Use the 4 Ohm tap in combination with the 2x12. You can have the spare two drivers disconnected, disconnected but shunted by a wire (makes them move less, different tone), or remove them and leave the holes open (less bass) or blank them off with ply (more bass).
4. Get two new 8 Ohm speakers for the 2x12, wire them in series to make a 16 Ohm cab. Use the 8 ohm amp tap with both cabs together.
5. Just use the 4x12!
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