#1

I have a JCM2000 DSL401. I am currently running it into a 4x12 cab. It is labelled 8 ohms mono or 6 ohms stereo. What's the difference?

Right now I am running my amp into the mono input of the cab. Do I switch the impedance switch to 8 ohms or 16 ohms? Logic tells me 8 ohms but one speaker output is going to the speaker already in the combo and the other is going into the mono input of the amp. Do I still use 8 ohms? What would happen if I switched it to 16 ohms on the cab but kept it in the 8 ohm mono input?

Right now I am running my amp into the mono input of the cab. Do I switch the impedance switch to 8 ohms or 16 ohms? Logic tells me 8 ohms but one speaker output is going to the speaker already in the combo and the other is going into the mono input of the amp. Do I still use 8 ohms? What would happen if I switched it to 16 ohms on the cab but kept it in the 8 ohm mono input?

#2

You would need to switch the amp to 4Ohms. 2-8Ohm loads equals 4 ohms. What kind of cab are you using that is 6 Ohms stereo? Did you mean 16 by chance?

Also the difference between Stereo and mono is Stereo is using 2 speakers in the cab. And mono is using all 4 speakers in the cab. The reason for stereo is so you can use 2 Heads into one cab or use a Stereo head into one cab. (For use with various stereo effects)

Also the difference between Stereo and mono is Stereo is using 2 speakers in the cab. And mono is using all 4 speakers in the cab. The reason for stereo is so you can use 2 Heads into one cab or use a Stereo head into one cab. (For use with various stereo effects)

#3

You would need to switch the amp to 4Ohms. 2-8Ohm loads equals 4 ohms. What kind of cab are you using that is 6 Ohms stereo? Did you mean 16 by chance?

Also the difference between Stereo and mono is Stereo is using 2 speakers in the cab. And mono is using all 4 speakers in the cab. The reason for stereo is so you can use 2 Heads into one cab or use a Stereo head into one cab. (For use with various stereo effects)

If he's running two 8 ohm outs in parallel then each of them should be run into a 16 ohm cab.

#4

If he's running two 8 ohm outs in parallel then each of them should be run into a 16 ohm cab.

And if you read his post He's using the speaker in the combo with the 4x12 Cab. Again 2-8Ohm loads = 4 Ohms.

#5

And if you read his post He's using the speaker in the combo with the 4x12 Cab. Again 2-8Ohm loads = 4 Ohms.

How do you figure?

#6

Read page 28 on this Linky.

It explains speaker Impedance's pretty well. With pics and text.

Edit: Page 31 has the pics of correctly hooking up different cabs.

It explains speaker Impedance's pretty well. With pics and text.

Edit: Page 31 has the pics of correctly hooking up different cabs.

*Last edited by boxcarmonument at Oct 31, 2009,*

#7

Read page 28 on this Linky.

It explains speaker Impedance's pretty well. With pics and text.

Edit: Page 31 has the pics of correctly hooking up different cabs.

I think you need to re-read that.

Any time you're running an amp in parallel you hook it into a cab with double the impedance rating of the output (because you actually cut the impedance in half when you run in parallel - i.e. a 2 ohm out needs to be plugged into a 4 ohm cab, 4 ohm into an 8 ohm cab, etc).

If the combo in question has the speaker wired directly into the amp and then he connects it to a cab, he needs a cab with matching impedance (say its a 8 ohm output he'd connect it to an 8 ohm cab).

However, if the speaker in the combo is connected via a speaker cable and he wants to run a cab in the other output, the amp is now run in parallel and the cab AND the speaker in the combo need to be twice the impedance as the labeled outputs (say both speaker outputs on the amp say 8 ohm, then the cab and the internal speaker both need to be rated at 16 ohms.)

*Last edited by i_am_metalhead at Oct 31, 2009,*

#8

I think you need to re-read that.

Any time you're running an amp in parallel you hook it into a cab with double the impedance rating of the output (because you actually cut the impedance in half when you run in parallel - i.e. a 2 ohm out needs to be plugged into a 4 ohm cab, 4 ohm into an 8 ohm cab, etc).

If the combo in question has the speaker wired directly into the amp and then he connects it to a cab with the matching impedance (say its a 8 ohm output he'd connect it to an 8 ohm cab).

However, if the speaker in the combo is connected via a speaker cable and he wants to run a cab in the other output, the amp is now run in parallel and the cab AND the speaker in the combo need to be twice the impedance as the labeled outputs (say both speaker outputs on the amp say 8 ohm, then the cab and the internal speaker both need to be rated at 16 ohms.)

It's the 2nd one.. the combo's internal speaker is connected to the back panel with a speaker cable. The other output jack is currently hooked to the cab. The switch on the back of the amp can be toggled between 8 ohms and 16 ohms. I don't know the impedance of the speaker because the setup is at my band's practice place. The cab is either 8 ohms mono or 16 ohms stereo.

Can I safely run this setup with the switch in the 8 ohm position?

#9

It's the 2nd one.. the combo's internal speaker is connected to the back panel with a speaker cable. The other output jack is currently hooked to the cab. The switch on the back of the amp can be toggled between 8 ohms and 16 ohms. I don't know the impedance of the speaker because the setup is at my band's practice place. The cab is either 8 ohms mono or 16 ohms stereo.

Can I safely run this setup with the switch in the 8 ohm position?

I'd have to see the amp - can you get pictures?

The reason I say this is there are one of two possibilities.

1) The switch turns both output jacks from 8 to 16 ohms. If this is the case you'd want it in the "8 ohm" position running into a 16 ohm cab and a 16 ohm internal speaker.

2) The switch controls the TOTAL output (i.e. when it is switched to "8 ohms" a single output jack is 8 ohms, but when both are being used they are only 4 ohms each). If this is the case then you would want it switched to "16 ohms" running into a 16 ohm cab and a 16 ohm internal speaker (Each output jack would essentially become an 8 ohm out ran in parallel so the rules for running cabs in parallel still apply).

#10

Ok if you have 2-16Ohm cabs And you plug them both into the amp. You need to plug the amp Them into the amp in and the amp needs to be set to 8Ohms. Because 2-16Ohm loads equals 8Ohms. Now assuming he is not running the cab in the stereo position. It's a 8Ohm cab. Right If it's 8Ohms mono and 16Ohms stereo. And if the Combo speaker is 8Ohms than (assuming) He never said what impedance the combo speaker was. That's 2-8Ohm loads combined Which equals a 4Ohm load on the amp.

And whats to reread when the picture clearly shows 2-8Ohm cabs plugged into the 4Ohms sockets. If he's daisy chaining the combo speaker and the cab we are into something different all together. But I highly doubt he's doing that.

And your last paragraph Basically says what I have been saying.. But I will put it in your words 2-16Ohms loads(cabs)combined = 8Ohms(what the amp needs to be set at)

And whats to reread when the picture clearly shows 2-8Ohm cabs plugged into the 4Ohms sockets. If he's daisy chaining the combo speaker and the cab we are into something different all together. But I highly doubt he's doing that.

However, if the speaker in the combo is connected via a speaker cable and he wants to run a cab in the other output, the amp is now run in parallel and the cab AND the speaker in the combo need to be twice the impedance as the labeled outputs (say both speaker outputs on the amp say 8 ohm, then the cab and the internal speaker both need to be rated at 16 ohms.)

And your last paragraph Basically says what I have been saying.. But I will put it in your words 2-16Ohms loads(cabs)combined = 8Ohms(what the amp needs to be set at)

#11

Ok if you have 2-16Ohm cabs And you plug them both into the amp. You need to plug the amp Them into the amp in and the amp needs to be set to 8Ohms. Because 2-16Ohm loads equals 8Ohms. Now assuming he is not running the cab in the stereo position. It's a 8Ohm cab. Right If it's 8Ohms mono and 16Ohms stereo. And if the Combo speaker is 8Ohms than (assuming) He never said what impedance the combo speaker was. That's 2-8Ohm loads combined Which equals a 4Ohm load on the amp.

And whats to reread when the picture clearly shows 2-8Ohm cabs plugged into the 4Ohms sockets. If he's daisy chaining the combo speaker and the cab we are into something different all together. But I highly doubt he's doing that.

And your last paragraph Basically says what I have been saying.. But I will put it in your words 2-16Ohms loads(cabs)combined = 8Ohms(what the amp needs to be set at)

It has nothing to do with stereo or mono. Any time you plug something into BOTH output jacks you are running them in parallel.

And no - two 16 ohm loads ran in parallel equals 16 ohms. So you would need to have a 16 ohm output running from the head (two 8 ohm outputs).

*Last edited by i_am_metalhead at Oct 31, 2009,*

#12

It has nothing to do with stereo or mono. Any time you plug something into BOTH output jacks you are running them in parallel.

And no - two 16 ohm loads ran in parallel equals 16 ohms. So you would need to have a 16 ohm output running from the head (two 8 ohm outputs).

Again This is what I've been saying Two 16Ohm cabs combined equals 16Ohms But you half to halve the impedance you plug into per cab. You are proving me wrong by giving the same answer that I have been giving. And you again gave the same answer I did. You need to plug into the 8Ohm outs. Therefore 2-16Ohm cabs combined equal 8Ohms a cab thats why your plugging into the 8Ohm outs on the amp. So again how are you proving me wrong? I don't understand how your not getting this. Your halving the impedance when run in parallel. That's why 2-16Ohm cabs = 16 Ohms or 8Ohms a cab. Therefore you are plugging into the 8Ohm outs. I not saying your wrong. I'm just saying you keep trying to prove me wrong by giving same answer I have been giving.

And the Stereo or mono comes into play depending on where he has the switch on the cab set to. Than the impedance changes on the cab.

#13

you guys are both coming at this from different sides.

and i am metal head, yes/no. 2 16 ohm cabs run in parallel is an effective 16 impedance load from each cabinet but a total circuit load of 8 ohms.

1/R=1/R1+1/R2

1/R = (1/16) + (1/16)

1/R = 2/16

1/R = 1/8

R= 8

8 ohm out = single 8 ohm load

(2) 8 ohm outs = (2) 16 ohm loads in parallel

16 ohm out = single 16 ohm load

period, no matter how you look at it, both of you are somewhat right/wrong. congrats

and i am metal head, yes/no. 2 16 ohm cabs run in parallel is an effective 16 impedance load from each cabinet but a total circuit load of 8 ohms.

1/R=1/R1+1/R2

1/R = (1/16) + (1/16)

1/R = 2/16

1/R = 1/8

R= 8

8 ohm out = single 8 ohm load

(2) 8 ohm outs = (2) 16 ohm loads in parallel

16 ohm out = single 16 ohm load

period, no matter how you look at it, both of you are somewhat right/wrong. congrats

*Last edited by gumbilicious at Oct 31, 2009,*

#14

you guys are both coming at this from different sides.

and i am metal head, yes/no. 2 16 ohm cabs run in parallel is an effective 16 impedance load from each cabinet but a total circuit load of 8 ohms.

1/R=1/R1+1/R2

1/R = (1/16) + (1/16)

1/R = 2/16

1/R = 1/8

R= 8

8 ohm out = single 8 ohm load

(2) 8 ohm outs = (2) 16 ohm loads in parallel

16 ohm out = single 16 ohm load

period, no matter how you look at it, both of you are somewhat right/wrong. congrats

No its still a total circuit load of 16 ohms because one 8 ohm out + one 8 ohm out = 16 ohm circuit load.

And everything else you just said was

**EXACTLY**what I just said, only you broke everything down individually whereas I had it all clumped together.

The other guy keeps changing what he says every time I point out something that he says that's wrong.

#15

i am sorry to say this again, but the math proof above proves the circuit load for 2 x 16 ohms speakers run in parallel is 8 ohms... this is assuming that my math is correct. i am telling you that i did not come up with that formula, it was taught to me in 5 different physics classes i have taken...

http://www.soundcitysite.com/sc_webpages/parallel_2x12.pdf

FROM:

http://www.legendarytones.com/ohms.html

http://www.soundcitysite.com/sc_webpages/parallel_2x12.pdf

Remember again that a series connection needs to have all connections present to work and this would apply to an amplifier’s output jacks as well. So as a result of knowing that an amplifier’s speaker outputs are wired in parallel, running two 16 ohm cabinets in a standard Marshall amplifier head would result in an 8 ohm load and therefore the amplifier should be set at 8 ohms accordingly

FROM:

http://www.legendarytones.com/ohms.html

#16

I got it figured out.

One output jack is running 16 ohms at all times and is connected to the internal 16ohm speaker. The other output jack is switchable between 16 ohms and 8 ohms.

Turns out that the cab runs 16 ohms mono and 8 ohms stereo. I plugged the cab straight into the amp and set the amp to 16 ohms and everything works just fine.

One output jack is running 16 ohms at all times and is connected to the internal 16ohm speaker. The other output jack is switchable between 16 ohms and 8 ohms.

Turns out that the cab runs 16 ohms mono and 8 ohms stereo. I plugged the cab straight into the amp and set the amp to 16 ohms and everything works just fine.

#17

That aint right. Direct from the manual:

So what you have is a 16 ohm speaker in parallel with a 16 ohm cabinet. That equals an 8 ohm load. So you need to select 8 ohms on the back of the amp.

PS: I even had a look at the circuit diagram to double check and both output jacks are indeed running standard, straight-forward parallel connections off the same winding, nothing tricky about it.

The DSL401 is fitted with twoparallel wiredloudspeaker jack sockets and a selector to switch between the normal 16 ohms (to suit the internal speaker) or 8 ohms. This makes the choice of extension cabinets even wider. For instance, not only could you use a Marshall 1960 4x12” cab, with or without the internal speaker (set amp to 8 ohms if using both, keep on 16 ohms if using without internal speaker), but you could also make the choice of various Marshall 1x12” or 2x12” extension cabs. But always make sure that the output selector is set correctly !

i.e.

1 x 16 ohm speaker = 16 ohm output

2 x 16 ohm speaker = 8 ohm output

1 x 8 ohm speaker = 8 ohm output

So what you have is a 16 ohm speaker in parallel with a 16 ohm cabinet. That equals an 8 ohm load. So you need to select 8 ohms on the back of the amp.

PS: I even had a look at the circuit diagram to double check and both output jacks are indeed running standard, straight-forward parallel connections off the same winding, nothing tricky about it.

*Last edited by Cathbard at Nov 4, 2009,*

#18

I've been running it 16 ohms.. is there anything wrong with that?

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