Author Topic: 69 1200s with mismatched cabs question  (Read 4797 times)

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Offline paco)))

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69 1200s with mismatched cabs question
« on: January 25, 2011, 09:32:49 am »
Hello, what would be the best configuration with running my 69 1200s into a 4x12L (8ohm) & a 4x12 Sunn/Fender (16ohm)?

Thanks!

Offline sunn-tanned

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Re: 69 1200s with mismatched cabs question
« Reply #1 on: January 25, 2011, 04:11:04 pm »
Well.... :| you're going to need to rewire a cab, more than likely the 8ohm to 16ohm. What type speakers/ohm are in the cabs?

Hello, what would be the best configuration with running my 69 1200s into a 4x12L (8ohm) & a 4x12 Sunn/Fender (16ohm)?

Thanks!

Offline EdBass

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Re: 69 1200s with mismatched cabs question
« Reply #2 on: January 25, 2011, 07:24:26 pm »
Well.... :| you're going to need to rewire a cab, more than likely the 8ohm to 16ohm. What type speakers/ohm are in the cabs?

Hello, what would be the best configuration with running my 69 1200s into a 4x12L (8ohm) & a 4x12 Sunn/Fender (16ohm)?

Thanks!

How do you rewire an 8 ohm, 4 speaker cab to 16 ohms? I don't know a way. If you ran the cabs parallel the amp might be OK, with the 5.3 ohm load on the 8 ohm tap, but two thirds of the power would be going to the 8 ohm cab.
You probably need some different drivers to do it right.

Offline sunn-tanned

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Re: 69 1200s with mismatched cabs question
« Reply #3 on: January 25, 2011, 09:40:04 pm »
 :lol:...yup my bad ...worked the math you can't.

Yes I was thinking of a couple of ways if you wanted to connect cabs or exchange two speakers.
Now if 5.3ohm load wouldn't you want to tap into a 4ohm?
Load should be less (more resistance) than the tap?

Well.... :| you're going to need to rewire a cab, more than likely the 8ohm to 16ohm. What type speakers/ohm are in the cabs?

Hello, what would be the best configuration with running my 69 1200s into a 4x12L (8ohm) & a 4x12 Sunn/Fender (16ohm)?

Thanks!

How do you rewire an 8 ohm, 4 speaker cab to 16 ohms? I don't know a way. If you ran the cabs parallel the amp might be OK, with the 5.3 ohm load on the 8 ohm tap, but two thirds of the power would be going to the 8 ohm cab.
You probably need some different drivers to do it right.
« Last Edit: January 25, 2011, 09:49:45 pm by sunn-tanned »

Offline paco)))

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Re: 69 1200s with mismatched cabs question
« Reply #4 on: January 26, 2011, 08:06:05 am »
Yeah, I've been thinking of re-wiring the newer (16ohm) sunn cab to an 8 or 4ohm anyway if it can be done. 8 ohm would be fine with me but I'm just not sure how to do it. Also, if I run 2 4ohm cabs off a beta bass amp, if I want to retain the 4ohm load do I run series or parallel? I guess I can google that. I ALWAYS get confused with this stuff :-P

Offline paco)))

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Re: 69 1200s with mismatched cabs question
« Reply #5 on: January 26, 2011, 08:28:27 am »
Okay, I have the 2 4ohm cabs figured out (running in series from the 4ohm amp output) but if I run the 1200s (the back has an 8ohm speaker & a 4ohm external speaker output) how would I go about it? Should I run both cabs in series (5.33ohm) from the 4ohm output?

Offline EdBass

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Re: 69 1200s with mismatched cabs question
« Reply #6 on: January 26, 2011, 09:37:28 am »
Now if 5.3ohm load wouldn't you want to tap into a 4ohm?
Load should be less (more resistance) than the tap?

With a SS amp you are safer with higher impedance, but with a transformer coupled tube amp I think a little under is better than a little over.

Yeah, I've been thinking of re-wiring the newer (16ohm) sunn cab to an 8 or 4ohm anyway if it can be done. 8 ohm would be fine with me but I'm just not sure how to do it.

What is the impedance of the individual drivers? That's important to know, because with a 4 speaker cab you have 3 nominal impedance options; the same as the individual drivers, 4 X the individual drivers, or .25 X the individual drivers.
Usually a 4 speaker cab is  factory wired series/parallel, which would indicate 16 ohm drivers in your 16 ohm cab and 8 ohm drivers in your 8 ohm cab.
This would make your options 32, 8, or 2 ohms for your 8 ohm cab and 64, 16, or 4 ohms for your 16 ohm cab. I don’t see a match there, do you?
Of course this is all speculation until you see what’s actually inside.

Also, if I run 2 4ohm cabs off a beta bass amp, if I want to retain the 4ohm load do I run series or parallel?

It can’t be done, period. If you run two 4 ohm cabs you either get 8 ohms or 2 ohms, 4 ohms is not an option.

Okay, I have the 2 4ohm cabs figured out (running in series from the 4ohm amp output) but if I run the 1200s (the back has an 8ohm speaker & a 4ohm external speaker output) how would I go about it? Should I run both cabs in series (5.33ohm) from the 4ohm output?

Two 4 ohm cabs in series would be an 8 ohm load, not a 4 ohm load.
For one thing, if you run your 16 and 8 ohm cabs in series you will end up with a 24 ohm load, which in a best case scenario would be slow death for your 1200S, it might even reach critical mass in short order.
If you run parallel you will get you 5.33 ohms, but I would run it from the 8 ohm tap. I don’t think the tap matters too much with a mismatch that close, but I think it’s safer to err on the low side as I mentioned above.

HOWEVER… If you run a 16 ohm cab with an 8 ohm cab you will get a huge disparity in power distribution, as I mentioned in a previous post. With a 120 watt 1200S, at full power about 80 of those watts will go to the 8 ohm cab and only 40 will go to the 16 ohm cab.

Before you ask for more advice you need to open up the cabs and determine what they are loaded with. You might get lucky and find that someone has already swapped out the speakers for ones you can use in your application!

Offline paco)))

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Re: 69 1200s with mismatched cabs question
« Reply #7 on: January 26, 2011, 10:21:35 am »
Thanks for all the info! I'm going to get in those cabs asap. I know the 4x12L has had the speakers replaced by Marshall speakers according to the guy I bought it from. The newer Sunn/Fender 4x12 is all original.

Offline paco)))

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Re: 69 1200s with mismatched cabs question
« Reply #8 on: January 26, 2011, 10:49:13 am »
The Sunn 412L is loaded with these...

Offline EdBass

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Re: 69 1200s with mismatched cabs question
« Reply #9 on: January 26, 2011, 11:29:55 am »
So that cab can do 16, 4, or 1 ohms. Which regretfully won't really help you out in your quest for running both cabs properly, unless... The other cab is mis-marked.
Of course there's only one way to really accurately determine that, and that is to measure.

I suggest anyone doing speaker wiring; for that matter any wiring, or even anyone using tube amps, get a DMM.
What the hell, anyone using amps and cabs at all, regardless of tube or SS should have one. They are easy to use, and so freekin' cheap there is really no excuse for not having one handy.

Here's one for 4 bucks.
http://www.harborfreight.com/7-function-digital-multimeter-90899.html

Although your speakers are probably exactly what they are marked, you never know for sure unless you check; I for one have reconed speakers marked "8 ohms" with 16 ohm kits in order to get an 8 ohm 215 cab, so it does happen. For a couple of bucks you can be sure:wink:

Offline paco)))

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Re: 69 1200s with mismatched cabs question
« Reply #10 on: January 27, 2011, 09:16:24 am »
Thanks a lot Ed! I really like this 412L cab & it works great with my guitarist's concert lead so I might sell it to him or try to find someone with a newer Sunn/Fender 4x12 16ohm cab which is what I've really been looking for to make a full matching stack. I just can't pass up a good deal though on great old Sunn cab :-D

Offline EdBass

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Re: 69 1200s with mismatched cabs question
« Reply #11 on: January 27, 2011, 10:58:45 am »
I just can't pass up a good deal though on great old Sunn cab :-D

You're preaching to the choir there, brother! Just ask my wife...