# HELP Using external speaker cab only while disconnecting stock combo speaker...OK?



## greco (Jul 15, 2007)

I have an old *Roland Super Cube 60 solid state combo* with an external speaker jack rated for 8 ohms.
When I plug in an external speaker cab, the speaker in the combo is also activated.

The stock speaker (also 8 ohms) is not something I am overwhelmed by. I have tried to replace it with 3 different speakers (all different brands) that I have on hand and none will fit due to the basket (specifically the rim) configuration of the stock speaker and the lack of space /depth inside the combo's cab. Also, there is the complicating fact that the speaker is front mounted and is held to the baffle with threaded plugs, so rear mounting is a pain to consider unless I want to get into some creative fastening concepts.

*If I disconnect the stock speaker, and use ONLY the external/aux speaker jack, will I be OK if I just tape the ends of the two wires going to the speaker and make sure they don't touch and cause a direct short? *
*OR *
*Do I need to wire a power resister between these 2 wires (as a load) ?
OR
Should I not attempt this (for whatever reason)?


*Thanks

Dave


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## Jean GODBOUT (Oct 31, 2009)

Yes Greco, disconect the stock speaker and connect your external cabinet into the external jack, your output transformer will ''see'' the impedance of the external cabinet that should be 8 Ohms in your case.

Jean


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## greco (Jul 15, 2007)

Thanks Jean....appreciate you responding.

Are you very sure that I cannot harm the amp in any way by doing this?

Cheers

Dave


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## keto (May 23, 2006)

correct, if the stock speaker is 8 ohms, and is disconnected, and the ends of both wires are isolated from each other and anything else (individually wrapped in electrical tape?), then running the amp to an 8 ohm cab can no way no how damage the amp.


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## nonreverb (Sep 19, 2006)

Solid state amps very rarely have output transformers and they work on a different principle than tube amps. Where impedance is concerned, it could be veiwed as being reversed. A solid state amp will happily drive a speaker of any impedance up to it's specified impedance. Anything lower, and the output will overstressed at it's trying to supply more current than the amp was designed for. Tube amps are a different story. Too high an impedance and all the power is reflected back into the transformer which can cause a transient spike effectively shorting the transformers winding.
If the amp that you're plugging into says it will accept an external 8OHM speaker and it doesn't break the contact with the internal one, then that means that the amp can actually drive 4OHMs total.



keto said:


> correct, if the stock speaker is 8 ohms, and is disconnected, and the ends of both wires are isolated from each other and anything else (individually wrapped in electrical tape?), then running the amp to an 8 ohm cab can no way no how damage the amp.


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## Gizmo (Aug 7, 2008)

The question has been answered, but what "taping them up" means of course is if you want to use the internal spkr again, you will have to untape and reconnect.
If it is possible, a good idea might be to put a switch in one of the lines to the internal spkr so you can disconnect and reconnect easily, or attach a switching jack in the line...


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## greco (Jul 15, 2007)

keto said:


> correct, if the stock speaker is 8 ohms, and is disconnected, and the ends of both wires are isolated from each other and anything else (individually wrapped in electrical tape?), then running the amp to an 8 ohm cab can no way no how damage the amp.


Thanks everyone. Keto's post (above) is exactly what I have in mind.

Cheers

Dave


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## nonreverb (Sep 19, 2006)

Actually, just leave one connected to the speaker and remove and tape off the other. 


greco said:


> Thanks everyone. Keto's post (above) is exactly what I have in mind.
> 
> Cheers
> 
> Dave


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## greco (Jul 15, 2007)

I took off the wires off of both terminals to the speaker and taped them separated.
(I didn't see nonreverb's post until just now). 

Now I have nothing coming from the extension cab.

Could it be that the speakers are wired in series and the amp thinks one speaker is blown?

Any (easy) approach that will allow me to accomplish my goal?..or best just to not bother trying anything further?

Cheers

Dave


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## starjag (Jan 30, 2008)

What about having long wires from the (disconnected) internal speaker going all the way to the external cab?


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## greco (Jul 15, 2007)

Hi starjag: I could make that with a jack (for the speaker cab wire) wired to 2 "spade" connectors (like the ones on the speaker terminals) in a small enclosure....as an easy to use interface. 
I was just hoping to have an easy way to approach this...but your suggestion might be the easiest solution, ultimately.

Thanks

Cheers

Dave


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## greco (Jul 15, 2007)

Starjag...I did as you suggested as I already had a temporary interface made up for testing speakers.

It worked fine, as one would expect. 

I'm now considering making a baffle to go over the hole for the 12 inch (stock) speaker and cutting out this (new) baffle for a 10 inch speaker...the (10 inch) L'il Buddy sounds nice.

Cheers

Dave


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## Gizmo (Aug 7, 2008)

The schematic for the Cube 60 shows that they are wired in parallel. So in theory, disconnecting the internal should have made no difference to the external.
(although not sure if the Super Cube and Cube are different amps or not)


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## greco (Jul 15, 2007)

They are different amps....but thanks for looking up the schem and letting me know.

Here is a pic of the same amp. I copied it from Kijiji. Cheers, Dave


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## Merlin (Feb 23, 2009)

greco said:


> They are different amps....but thanks for looking up the schem and letting me know. Here is a pic of the same amp. I copied it from Kijiji. Cheers, Dave


Looks familiar...


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