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run a 4x12 off my spider IV 120?


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HI all,

So long story short, I have the line 6 spider IV 120 combo amp, I blew the speakers.

I decided to use a 4x12 instead and keep the combo amp as a head.

on the back of the combo amp there are no speaker outputs, only 4 wires, two to each speaker.

I want to disconnect the speakers and install 1/4 jacks so I can now run  2 speaker cables out to a 4x12 stereo cab.

I am not a tech but I believe all that needs to be done is add the input jacks to these speaker wires.

Any info?


I would just go buy the $300 150 hd head and be done with it  thing is I just spent all my cash on a brand new mesa 4x12 road king cab expecting to just plug it in, lol oops.

So since I can not buy a head right now, and I have gigs to play can I make this work or not?


The cabinet is 8 ohms stereo set to work with the line 6, I checked with both line 6 and then Mesa before having this cab built.

thanks for any help with this, I really appreciate it.


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  • 2 weeks later...

Thanks Mike, I have now bought the switchcraft jacks, and I am going tomorrow to solder them to the speaker wires.

I have identified the hot and ground on the switches, I know the tip is hot and the sleeve is ground and those are easily identified on the switches.

The only thing I am not positive about and I am searching for right now are the speaker wires.



I have a black wire and a white wire running to one of the speakers, and a black wire and a red wire running to the other.

Common sense tells me that the white and the red are the positive or hot wires on each speaker and the blacks are ground, but I want to be sure and I dont have a tester.


They might be dark green, I dont have it in front of me at the moment so I am going by memory, all I know is they both have a wire that is the same color and then they each have a different color with it, red/white. 


Usually, red is hot and green is ground, I have also seen black as ground, but I dont understand why they would use a red wire on one speaker and a white wire on the other, unless it was a matter of not mixing up left and right, but identifying them both as "hot wires".


If you have any thoughts on the wires colors and -/+ let me know what you think, I am still looking on the site for a schematic.


Also, I had a Mesa Boogie Road King Rectifier built for this amp so I can run 2, 8 ohm inputs from the head for a stereo cab, the cab is 300 watts where the head is 120 so I have lots of headroom, I am thinking this is going to sound great, the Road King is a half open back, mis match of speakers, so the sound should be very interesting and warm I hope, I will let you know after tomorrow night when I get this all together and test it.


Thanks again Mike


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Attached is a pic of my new rig after I cut it down, removed speakers, wired it, etc.. and then tested it with the Mesa


A Line 6 Spider IV 120 head/footswitch, running to a 300 watt Mesa Road King Rectifier 4x12 cabinet.

All tested and ready to go.


The 120 watt and 75 watt models I have been using cant handle being cranked up at band practice, to overcome the drums, the amp really suffers.


I blew one, or both speakers in my 120, and the 75 watt I am borrowing, sounds like it is gonna blow at any minute.


The 75 watt while plugged in at level 4 or up bleeds all kinds of feedback and distortion etc.. so you simply can not get it to silence.


This new rig, my old 120 watt chassis and this 300 watt Mesa, are silent, even cranked way way up, quiet as a mouse until I want it to scream, then it screams, warm and proud with no fear of blowing,  you can not get that quiet with the stock set up turned up past level 4, at least not in my experience.


Basically I took a combo amp not suited for live performances and made it suitable for live performances.


The difference between the 150hd and the 120 combo besides 30 watts and maybe some pre sets, is the speaker configuration, the 120 runs through two, 10" speakers that are barely rated to handle the 120 watts, there is no headroom and so the amp sounds great at medium volumes but not turned up, I need it to sound clear and crisp at any level, by pairing these up, I have now got that.


I suppose like the 150hd and line 6 cab are probably the equivalent to this set up for those who want to buy line 6 gear for either practice or gigging, I didnt have the time or money to buy a new head and so decided to put this together, it cost me $8.00 and took me a few hours all together between researching, and actually taking the amp apart and then modify and put it back together.





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