1200S for a bass rig

[rick.heil]

as long as you wired them right, yes, they'd be 16 ohms.  If they're two 8 ohm speakers, then 16 ohms in series; if two 16 ohm speakers in parallel, then you've got 8 ohms.  so maybe a nice pair of heavy magnet 8 ohms (if they exist, i dont know bass speakers)?  or one really big-arse 16 ohm speaker.  Get, say, two 21" woofers from this sub (http://catalogs.infocommiq.com/AVCAT/CTL3120/index.cfm?mlc_id=3120&SID=16904268&pin_id=2128&ProdID=344102&T3=137) and put them in series...that'd give you 16 ohms and more thump than anything on earth!


heehee. the whole concept of a 21" speaker is kinda nuts, isn't it?

[rp]

The only 16 ohm bass replacements I can find are the eminence delta 15 b's. They look good though...
so uh, every time I replaced a speaker I just plug it into the jacks....what's this series parallel stuff?

I look so dumb I'm sure.

How would I wire two of those 16 ohm speakers to give a 16 ohm load?? I don't want to wire parallel if it's going
to make an 8 ohm load, because that defeats the purpose...I already have a 1x15 at 8 ohms.
But if wired series, from what I understand, would double the load to ...32 ohm??
Maybe I should get two 8 ohm 15's and wire them series.. for 16? Is that really safe though??
Is having one 16 ohm speaker the only way to get the 16 ohm load from 16 ohm speakers?
Ow, my head hurts. ...also if I do get two 8 ohm speakers to wire series for the 16 ohm load..can anyone tell me how to do it...
it would be my first time.


thanks.

[Isaac]

Doesn't matter, Robin. Remember what I wrote about how the jacks are wired? Once you plug into the 8 ohm jack, you no longer have a 16 ohm jack. The internal wiring has put it in parallel with the 8 ohm jack, so you now have two 8 ohm jacks, in parallel. That's two jacks  in parallel, which can accept a total load of 8 ohms, not 8 ohms per jack. Even if you could separate out the jacks, it still wouldn't work, because an 8 ohm load on the 8 ohm tap will take the full output of the amp. Same with a 16 ohm load on the 16 ohm tap. There being no magic in this world, the amp would not be able to supply its full output to two different loads. At best, each would get half. At worst, foul smelling smoke would emanate from the amp.

On the plus side, placing an 8 ohm load in parallel with a 16 ohm load results in a total load of 5.3 ohms, which would probably not destroy the amp.

[rp]

Doesn't matter, Robin. Remember what I wrote about how the jacks are wired? Once you plug into the 8 ohm jack, you no longer have a 16 ohm jack. The internal wiring has put it in parallel with the 8 ohm jack, so you now have two 8 ohm jacks, in parallel. That's two jacks  in parallel, which can accept a total load of 8 ohms, not 8 ohms per jack. Even if you could separate out the jacks, it still wouldn't work, because an 8 ohm load on the 8 ohm tap will take the full output of the amp. Same with a 16 ohm load on the 16 ohm tap. There being no magic in this world, the amp would not be able to supply its full output to two different loads. At best, each would get half. At worst, foul smelling smoke would emanate from the amp.

On the plus side, placing an 8 ohm load in parallel with a 16 ohm load results in a total load of 5.3 ohms, which would probably not destroy the amp.

Ok, so one plugged in the 16 ohm jack can only be a 16 ohm cab, and one plugged into the 8 ohm jack has to be an 8 ohm cab, but if I plug two cabs into it they must be 4 ohm cabs?? So...the way I understand it if the tap was changed to 8/4, it would be a 8ohm cab in the left, or a 4ohm on the right, and if you plug in two they only get 2 ohms between the two cabs??
I don't see how that will help as I don't have a 4ohm cab or 2 ohm cab, and would still only be able to use one 8 ohm cab and lose the ability to ever use a 16 ohm cab.

Also this kinda confuses me...

If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.

If you can use two 16 ohm cabs together with an 8 ohm load....why can't two 8 ohm cabs be used safely at a 4 ohm load?
Wouldn't those 16 ohms cabs also be operating at 4 ohms together...isn't that alot different than the two 8 ohm cabs??
totally confused now..

[Isaac]

Doesn't matter, Robin. Remember what I wrote about how the jacks are wired? Once you plug into the 8 ohm jack, you no longer have a 16 ohm jack. The internal wiring has put it in parallel with the 8 ohm jack, so you now have two 8 ohm jacks, in parallel. That's two jacks  in parallel, which can accept a total load of 8 ohms, not 8 ohms per jack. Even if you could separate out the jacks, it still wouldn't work, because an 8 ohm load on the 8 ohm tap will take the full output of the amp. Same with a 16 ohm load on the 16 ohm tap. There being no magic in this world, the amp would not be able to supply its full output to two different loads. At best, each would get half. At worst, foul smelling smoke would emanate from the amp.

On the plus side, placing an 8 ohm load in parallel with a 16 ohm load results in a total load of 5.3 ohms, which would probably not destroy the amp.

Ok, so one plugged in the 16 ohm jack can only be a 16 ohm cab, and one plugged into the 8 ohm jack has to be an 8 ohm cab, but if I plug two cabs into it they must be 4 ohm cabs??

No. the total load should equal the transformer tap it is connected to. So, if you're connected to the 8 ohm tap, the total load should be 8 ohms. How you get there doesn't matter. One 8 ohm cabinet, two 16 ohm cabinets, four 32 ohm cabinets, whatever.

So...the way I understand it if the tap was changed to 8/4, it would be a 8ohm cab in the left, or a 4ohm on the right, and if you plug in two they only get 2 ohms between the two cabs??

I have no idea what you're trying to say here.

If the amp was changed to 8/4, then the main output jack, the one currently labeled 16 ohms, would be an 8 ohm jack. The one labeled 8 ohms would be a 4 ohm jack. If you plug into the 4 ohm jack, the 8 ohm jack also becomes a 4 ohm jack, and the total load - not any individual cabinet - should equal 4 ohms.

I don't see how that will help as I don't have a 4ohm cab or 2 ohm cab, and would still only be able to use one 8 ohm cab and lose the ability to ever use a 16 ohm cab.

I don't think I said anything about 4 or 2 ohm cabinets. Where did you get this? You don't lose the ability to use a 16 ohm cabinet, you just have to make sure that the total impedance load on the amp is compatible with the transformer tap you're using. If you're using the 8 ohm tap, two 16 ohm cabinets are fine.

Also this kinda confuses me...

If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.

If you can use two 16 ohm cabs together with an 8 ohm load....why can't two 8 ohm cabs be used safely at a 4 ohm load?
Wouldn't those 16 ohms cabs also be operating at 4 ohms together...isn't that alot different than the two 8 ohm cabs??
totally confused now..

Now I'm confused. Of course two 8 ohm cabinets can be safely used as a 4 ohm load. Who said otherwise? But two 16 ohm cabinets make an 8 ohm load not a 4 ohm load, as you seem to be saying.

Two 16 ohm cabinets in parallel=8 ohms.
Two 8 ohm cabinets in parallel=4 ohms.
Two 4 ohm cabinets in parallel-2 ohms, which your amp is not designed for.

[EdBass]

The only 16 ohm bass replacements I can find are the eminence delta 15 b's. They look good though...
so uh, every time I replaced a speaker I just plug it into the jacks....what's this series parallel stuff?

I look so dumb I'm sure.

 

You really need to educate yourself on the difference between series and parallel circuits. Do a little internet research (it's all out there) on basic circuits and this whole thread will become a lot clearer. Reading back through this thread, it doesn't seem to me that you are going to get the answer you are looking for unless you get a handle on the series/parallel issue.

For now, get your amp to somebody who knows and have them switch your output taps to 4 & 8 ohms, plug your 410 into one and your 115 into the other and let her rip! Let us know how it sounds.
The tap switch is completely and easily reversable, it won't hack up your classic amp, the hardest part of the operation is pulling and replacing the chassis in the box. It's a 10 minute job for a rookie tech, and a veteran solder jockey could do the work in a coma!

You don't look dumb, you just look "new". Hang in there, it's as clear as mud now but soon you'll be able to look back and laugh about when you "didn't even understand impedance!"

[rp]

I think I see now...let me know if I'm wrong. I wasn't splitting the load when I was talking about two cabs.
That's why two 8ohm cabs would be at 4ohms rather than 8ohms even though both plugs were used and the 16ohm was cancelled.
Even though the output was 8ohms, since it was two cabs the impedence is 4ohms for the two.
However since the output is 16/8 ohm split....the 4ohm output is unnatural and that's why you guys suggested
having the tap altered to 8/4....to match the cabs I want to use. I think I was getting what the cabs do and head do confused.

God I hope I'm right.

So really with this head you would want two 16ohm cabs running at 8ohms because of the two cab split. Right?
I mean you could run just one 16ohm cab in the 16 output, but it would probably be louder(fuller) with the two cabs at 8ohms.
I'm guessing though if I make the change to the 8/4 output that I won't be able to use two 16ohm cabs because when
you plug in the second cab the output will switch to 4 ohms rather than 8ohms.

The only problem now is finding a tech around where I live...which is nowhere, louisiana.

thanks guys, robin

[EdBass]

I think I see now...let me know if I'm wrong. I wasn't splitting the load when I was talking about two cabs.
That's why two 8ohm cabs would be at 4ohms rather than 8ohms even though both plugs were used and the 16ohm was cancelled.
Even though the output was 8ohms, since it was two cabs the impedance is 4ohms for the two.

Two 8 ohm cabs wired in parallel make a total load of 4 ohms, the same two cabs in series would have a 16 ohm load.
Sunn amps like yours connect the two output jacks in parallel when both are used, which in effect connects the two cabinets in a parallel circuit for a total of load of 4 ohms.

However since the output is 16/8 ohm split....the 4ohm output is unnatural and that's why you guys suggested
having the tap altered to 8/4....to match the cabs I want to use. I think I was getting what the cabs do and head do confused.

If you look at the back of your amp, you will see a huge chunk of iron on the far right side. That's the output transformer. It is actually a huge coil (winding) of copper wire wound around an iron core, and it's primary function is to match speaker impedance with the output stage of the amp. On all of the old Sunn amps, there are three wires referred to as "taps" that "tap" into this winding at different places (one is for 4 ohm loads, one for 8 ohm loads, and one for 16 ohm loads) but only two of the three are used for the two output jacks, the third one is still there, but unused.
The "S" series Sunn tube amplifiers were never sold without a matching speaker cabinet, you couldn't buy just the head you had to buy the package, but they always had the option of an additional, or extention, cabinet. If the matching cabinet for the amp was 16 ohms, they used the transformers 16 and 8 ohm taps (like your 1200S) and if the matching cab was 8 ohms they used the 8 and 4 ohm taps so that if and when you used another matching cabinet, the impedance would be correct. Two 16's would be 8, two 8's would be 4 because of the parallel wired jacks in the amp.
As I said above, the third tap is still there, to make your output jacks 8 and 4 ohms you only switch ONE wire. No major surgery, and just as easy to restore back to original.

So really with this head you would want two 16ohm cabs running at 8ohms because of the two cab split. Right?
I mean you could run just one 16ohm cab in the 16 output, but it would probably be louder(fuller) with the two cabs at 8ohms.

Absolutely, but not probably louder(fuller); most definitely louder(fuller)!

The only problem now is finding a tech around where I live...which is nowhere, louisiana.

thanks guys, robin

Can't help you much with that one. You don't really need a guitar amp tech, just about any electrical tech (stereo,TV, radio, etc.) should be able to fix you up.

[rp]

I think I see now...let me know if I'm wrong. I wasn't splitting the load when I was talking about two cabs.
That's why two 8ohm cabs would be at 4ohms rather than 8ohms even though both plugs were used and the 16ohm was cancelled.
Even though the output was 8ohms, since it was two cabs the impedance is 4ohms for the two.

Two 8 ohm cabs wired in parallel make a total load of 4 ohms, the same two cabs in series would have a 16 ohm load.
Sunn amps like yours connect the two output jacks in parallel when both are used, which in effect connects the two cabinets in a parallel circuit for a total of load of 4 ohms.

However since the output is 16/8 ohm split....the 4ohm output is unnatural and that's why you guys suggested
having the tap altered to 8/4....to match the cabs I want to use. I think I was getting what the cabs do and head do confused.

If you look at the back of your amp, you will see a huge chunk of iron on the far right side. That's the output transformer. It is actually a huge coil (winding) of copper wire wound around an iron core, and it's primary function is to match speaker impedance with the output stage of the amp. On all of the old Sunn amps, there are three wires referred to as "taps" that "tap" into this winding at different places (one is for 4 ohm loads, one for 8 ohm loads, and one for 16 ohm loads) but only two of the three are used for the two output jacks, the third one is still there, but unused.
The "S" series Sunn tube amplifiers were never sold without a matching speaker cabinet, you couldn't buy just the head you had to buy the package, but they always had the option of an additional, or extention, cabinet. If the matching cabinet for the amp was 16 ohms, they used the transformers 16 and 8 ohm taps (like your 1200S) and if the matching cab was 8 ohms they used the 8 and 4 ohm taps so that if and when you used another matching cabinet, the impedance would be correct. Two 16's would be 8, two 8's would be 4 because of the parallel wired jacks in the amp.
As I said above, the third tap is still there, to make your output jacks 8 and 4 ohms you only switch ONE wire. No major surgery, and just as easy to restore back to original.

So really with this head you would want two 16ohm cabs running at 8ohms because of the two cab split. Right?
I mean you could run just one 16ohm cab in the 16 output, but it would probably be louder(fuller) with the two cabs at 8ohms.

Absolutely, but not probably louder(fuller); most definitely louder(fuller)!

The only problem now is finding a tech around where I live...which is nowhere, louisiana.

thanks guys, robin

Can't help you much with that one. You don't really need a guitar amp tech, just about any electrical tech (stereo,TV, radio, etc.) should be able to fix you up.

Thank you so much....I think I've got it now. Hmmm now I just need some more cabs...lol

[rp]

How about this? I can't really rewire the 1x15xl because it's a single 8ohm speaker...you can't wire any other way than parallel..right?
But what about the 4x10xl? It has 4, 8 ohm speakers wired for an 8ohm load and 400watts (series/parallel wiring I think). Is there anyway to wire those 4, 8 ohm speakers to 16 0hms??

[Isaac]

No.

Four 8 ohm drivers can be wired as 2, 8, or 32 ohms, but not 4 or 16.

All in series=32ohms.
Series/parallel=8 ohms.
All in parallel=2 ohms.

[rp]

No.

Four 8 ohm drivers can be wired as 2, 8, or 32 ohms, but not 4 or 16.

All in series=32ohms.
Series/parallel=8 ohms.
All in parallel=2 ohms.

Yeh, no weaseling out of it that way, lol. I had figured that as I found a neat little
wiring chart on the net at a replacement speaker website.
If it's ok I can post the link for others who are new to the whole wiring/ohm process.

[Isaac]

heehee. the whole concept of a 21" speaker is kinda nuts, isn't it?

Why? I mean, 18" isn't nuts, so why would 21" be? As far as I'm concerned, it's all in the execution.

Oh, and EV used to make a 30" driver!

Electro-Voice 30W

[rick.heil]

holy mother of my lord and saviour, that is CRAZY.   


I've been coveting a 21" for my dorm room stereo setup for a while...maybe I should look into one of these (I'm currently running a pair of Bose 301s with an Alesis RA-100 on one outlet, and my beta lead on the other).