Can I do this?

[slipperyfingers]

I have two 2x12 cabs at 8 ohm per cab. Each cab has two parallel inputs. Using a normal speaker cable between the two cabs...putting them in parallel...I would have a 4 ohm load, but what if I wired the cable between the cabs from tip to ring (backwards) would that give me a serial connection at 16 ohm load, and would it still be in phase.

Thanks-in-advance,
Bill

 

[VaughnC]

Originally posted by slipperyfinger
I have two 2x12 cabs at 8 ohm per cab. Each cab has two parallel inputs. Using a normal speaker cable between the two cabs...putting them in parallel...I would have a 4 ohm load, but what if I wired the cable between the cabs from tip to ring (backwards) would that give me a serial connection at 16 ohm load, and would it still be in phase.

Thanks-in-advance,
Bill

You would still end up with a 4 ohm load but one cab would be out of phase with the other, resulting in a hollower sound.

 

[John Phillips]

You could rig this up so the two cabs are in series, but you would need to either rewire the sockets in one cab so that the second socket is a series output, or make up a special 'daisy chain' cable with three plugs on it. The first option is probably easier, but you'll need a switched jack if you ever want to run that cabinet on its own.

 

[slipperyfingers]

Thanks for the replies. I think what I want to do is put a switch on each cab that in one position the cab would be wired in in series,and with the switch in the other position, it would be wired in parallel. Type of switch needed, and a diagram would be much appreciated. (or other suggestions)

Best Regards,
Bill

 

[John Phillips]

You need a heavy-duty DPDT switch. Use the best, most reliable switch you can.

Here's how to wire it.

Series/Parallel switching

Strictly speaking you don't need both of the connections in the 'X' pattern at the bottom, but fitting both increases reliability by using both switch contacts in parallel - always a good idea especially for speaker connections.

This gives parallel when the switch contacts are in the 'up' position (with most toggle switches that's when the toggle is down) and series when the contacts are in the down position.

 

[slipperyfingers]

John,
Thank you so much for the trouble!

Best regards,
Bill

 

[John Phillips]

No trouble!

Make sure the two parts of the 'X' are not touching each other, BTW, if that's not clear from the drawing! I tend to use solid copper wire for them, and put a little bit of insulated sleeving on one.

Should be quite an easy mod - a standard heavy-duty DPDT should fit in a jack hole.

Reliability is very important BTW - if the switch makes an intermittent contact, the amp could end up with no load on it. That's why I like to use the 'X' wiring, it significantly reduces the chance of this happening.


Just as an aside, I use this wiring method for 'true' bypass switching in pedals too - the usual scheme is to connect both of the two lowest tags in that diagram to each other. This is bad, because then in bypass the signal has to pass through both switch contacts - a bad contact in either will break the signal path. With the 'X' wiring, it would take a failure in both at the same time to cause trouble.

 

[VaughnC]

If you happen not to want to modify the cabs themselves, hears a diagram of the daisy chain cable that John spoke of earlier.

 

[slipperyfingers]

VaughnC and John,
I decided to try the special serial cable, got it made up last night and will be trying it at rehearsal tonight (I'll make sure to check the load with an ohm meter before plugging in, but I did do a continuity check and seems like the cable is all set). I'm still a little confused about one thing, if I decide to use the toggle switch method (I purchased two switches last night) seeing as the individual speakers are 16 ohm each, if I put each cabinet into serial mode with the switch, it will make the load 32 ohms...now with a standard cable between the cabs...will I end up with 64 ohms, or as desired 16 ohms...it seems to me that putting a standard cable between the cabs would continue the serial connection...but obviously, I don't have a complete grasp of all of this.

Thanks,
Bill

 

[John Phillips]

Sorry, somewhere in the thread I lost track that you were talking about 8-ohm cabs - obviously with 16-ohm speakers. I think it was the series/parallel switch question... I somehow thought you were talking about 8-ohm speakers.

Yes, you are quite right. If you series-wire the cabs with the switch, they will be 32-ohm cabs. You will need to connect them in parallel to make a 16-ohm load. A normal speaker cable connected between the two cabs will achieve this, or alternatively just connect them both to the amp - assuming it has two speaker outputs.

The only way to get a series connection is to use the special daisy-chain cable (unless you were to rewire one of the cabs so the second socket was a series-out, but that's getting more complicated than you need).

Don't whatever you do run the amp with a 64-ohm load! That would be a serious risk to the OT, even if the amp was set to 16 ohms.

 

[slipperyfingers]

Thanks again John,
Bill