4x12 Speaker Cabinet Wiring (Stereo/Mono)

[adam79]

Hi. I have a 4x12 Marshall 1960a Cab w/ four 15ohm Celestion G12-65s; I
currently have it wired for 15ohms mono. Why do companies make 15ohm
speakers when every output transformer only has 16ohm taps? Anyways,
onto my main question..

I want to rewire my Cab for Mono/Stereo use. I recently bought an Ampeg
V4; the OT taps only run at 2, 4 or 8ohms (I talked to the tech that has
my amp and he said that there isn't a 16ohm tap on the OT in the V4). Is
there a way to wire the 15ohm speakers so they are compatible with said
OT when running in Stereo and Mono? I assume it would be easier to
install a second input jack rather than use a DPDT switch.

Would it be a dumb idea to wire only two speakers at a time (i.e.
connect two speakers to their own jack, so it would be like running two
2x12s inside the 4x12 cab)?

My other amp is a Peavey VTM-120, which has speaker outputs for 2,4,8
and 16ohms. Are there any advantages or disadvantages when wiring 16ohm
speakers to run at 4ohms?

Thanks,
-Adam

[IUnknown]

Post by adam79
Hi. I have a 4x12 Marshall 1960a Cab w/ four 15ohm Celestion G12-65s; I
currently have it wired for 15ohms mono. Why do companies make 15ohm
speakers when every output transformer only has 16ohm taps? Anyways,
onto my main question..

FYI - Those speakers were discontinued in '82, I believe, and they
sound fantastic in that cabinet.

The reason for the 15ohms is that was the range celestion produced
them at around that period. Wire it up and treat is as a 16ohm cab....

[Bruce Morgen]

Post by IUnknown

Post by adam79
Hi. I have a 4x12 Marshall 1960a Cab w/ four 15ohm Celestion G12-65s; I
currently have it wired for 15ohms mono. Why do companies make 15ohm
speakers when every output transformer only has 16ohm taps? Anyways,
onto my main question..

FYI - Those speakers were discontinued in '82, I believe, and they
sound fantastic in that cabinet.
The reason for the 15ohms is that was the range celestion produced
them at around that period. Wire it up and treat is as a 16ohm cab....

The 15 ohm impedence spec
is a Britishism -- other
speakers from thereabouts,
e.g. Tannoy and Goodmans
on the hi-fi side of the
industry, also used it.
For all practical purposes
it's the same as 16 ohms
-- impedence varies with
frequency anyway, so
there's no way to spec it
accurately without
including the frequency
or frequencies at which it
was calculated and/or
measured.

[Miles Ahead]

On Tue, 10 Apr 2012 13:37:37 -0700 (PDT), IUnknown

Post by IUnknown
The reason for the 15ohms is that was the range celestion produced
them at around that period. Wire it up and treat is as a 16ohm cab....

At that time in the UK, it was anything to make a # change, and spkrs
were sometimes spec'd to a .00% level, and rubes bought it.

Yeah, treat it as a 16. 9 of 1, 1/76th of the other...

What ya gotta understand folks..it's all piss & ving..

Late 70's was even worse. 14.6 ohms - vs - 13.84 ohms..

People stoned onstage really believed that shit..

By the late 80's, it was gone. replaced by whatever.

..learn or be sold to is not just a cheap line I made up,
I tell any of ya, the same people today buying $800 1w (1w!)
amps gave a tinker's bum about .07463527485% ohm cabs.

I am amazed they lasted so long, and am sorry that today they
have so much $$$$$$$$$$$$$$$$$$$$$$$$$$ that could of been
milked when I had less whatevers. Yup..it's going be a long night..

Can't I make this flocking phone do some fluckuing app to filter out
my lack of finger size &/or want to re-word what I post off this well
protected hunk of shit?. What is wrong with this world..TWLL ME....

I bet ya James Marshall and Dave Reeves are LAUGHING right now...

As we leave, I see a brown breif case. I didn't give it any real big
notice, I knew it was there. M'Lady said: "Clean that gun case"..

No way. Last time I opened it was to oil it, it's set to be opened if
need be is SECONDS or less and it's covered in 9+ year old dust.

I mean covered in it, crap on top of dust, et etc etc.

And it's on topic.. 9 x 18 Mak sold to me by HP..

And it hit me..esp with such a rare item:

"..may your weapons collect dust.."



JJTj






2 night, I'm going to a bullfight, and a ballet..
..one.....after the other.....after the other.

.........remember....

..you don't know where I am...

[adam79]

Post by IUnknown

Post by adam79
Hi. I have a 4x12 Marshall 1960a Cab w/ four 15ohm Celestion G12-65s; I
currently have it wired for 15ohms mono. Why do companies make 15ohm
speakers when every output transformer only has 16ohm taps? Anyways,
onto my main question..

FYI - Those speakers were discontinued in '82, I believe, and they
sound fantastic in that cabinet.
The reason for the 15ohms is that was the range celestion produced
them at around that period. Wire it up and treat is as a 16ohm cab....

They do sound amazing. If I ever decide to buy another cab (for a full
stack), I'd go with a 1960b w/ Vintage 30s. I bet they'd compliment the
65s well.

[IUnknown]

Post by adam79
I want to rewire my Cab for Mono/Stereo use. I recently bought an Ampeg
V4; the OT taps only run at 2, 4 or 8ohms (I talked to the tech that has
my amp and he said that there isn't a 16ohm tap on the OT in the V4). Is
there a way to wire the 15ohm speakers so they are compatible with said
OT when running in Stereo and Mono? I assume it would be easier to
install a second input jack rather than use a DPDT switch.

If you wire all of the speakers in parallel, the net impedance of the
cabinet will be roughly 4ohms. That should work with the V4.

Post by adam79
Would it be a dumb idea to wire only two speakers at a time (i.e.
connect two speakers to their own jack, so it would be like running two
2x12s inside the 4x12 cab)?

If you wire each 'side' of the cabinet in parallel, each side/jack
will be 8ohms. The problem with this setup is that you will never be
able to drive all 4 speakers at once unless you have a head with dual
speaker jacks. The only benefit to this is if you have a stereo setup.

Post by adam79
My other amp is a Peavey VTM-120, which has speaker outputs for 2,4,8
and 16ohms. Are there any advantages or disadvantages when wiring 16ohm
speakers to run at 4ohms?

Do that at your own peril. Tube amps respond very differently to
impedance mismatches than solid state amps - hence the switches :)

Your degree of risk depends on the amp. Some guys will tell you that
small mismatches are no big deal.... However, there is a lot of
difference between 16ohms and 4ohms. I wouldn't try it.

All that being said, wire all the speakers in the cabinet in parallel.
That will give you an approximate load of 4ohms.... and that should
work with all your amps.

[adam79]

Post by IUnknown
If you wire each 'side' of the cabinet in parallel, each side/jack
will be 8ohms. The problem with this setup is that you will never be
able to drive all 4 speakers at once unless you have a head with dual
speaker jacks. The only benefit to this is if you have a stereo setup.

Is there a way to wire the cab in a Mono/Stereo setup where all 4
speakers are running whether I'm in either Mono or Stereo mode? In all
the 4x12 diagrams I've seen with this type of setup, the impedance
doubles when in Stereo mode (I have no use for the cab running at 32ohms).

Thanks,
-Adam

[adam79]

Post by IUnknown
If you wire each 'side' of the cabinet in parallel, each side/jack
will be 8ohms. The problem with this setup is that you will never be
able to drive all 4 speakers at once unless you have a head with dual
speaker jacks. The only benefit to this is if you have a stereo setup.

If I add two jacks and do the parallel setup on each side, can I leave
the existing mono wiring without any of the wires crossing?

Thanks,
-Adam

[Jim]

Post by adam79

Post by IUnknown
If you wire each 'side' of the cabinet in parallel, each side/jack
will be 8ohms. The problem with this setup is that you will never be
able to drive all 4 speakers at once unless you have a head with dual
speaker jacks. The only benefit to this is if you have a stereo setup.

If I add two jacks and do the parallel setup on each side, can I leave
the existing mono wiring without any of the wires crossing?
Thanks,
-Adam

I understand the wiring, schematics, etc. I could build my own jack
circuits to do pretty much any option I want. But I still found the
following much simpler and easier to install in my cab:

http://www.mojotone.com/amp-parts/amp-jacks/OEM-Stereo-Mono-Cabinet-4x12-Wired-Jack-Plate-Double-1-4

Why not use that? It'll give you stereo, plus mono at two impedances.

[adam79]

I understand the wiring, schematics, etc. I could build my own jack
circuits to do pretty much any option I want. But I still found the
http://www.mojotone.com/amp-parts/amp-jacks/OEM-Stereo-Mono-Cabinet-4x12-Wired-Jack-Plate-Double-1-4
Why not use that? It'll give you stereo, plus mono at two impedances.

That looks like something I might be interested in, but I still have to
wire the speakers. Like I was saying in my previous post, in all the
4x12 wiring schematics for Stereo/Mono setups (that use all 4 speakers
in each mode), the stereo setup doubles the impedance.. since my
speakers are 16ohms, the cab would be running at 32 ohms in stereo,
which isn't compatible with either of my amps.

Also, if I decide to add additional wiring in my cab, Can I wire the
speakers over my existing Mono wiring without worrying about the wires
crossing?

Thanks,
-Adam

[Jim]

Post by adam79

I understand the wiring, schematics, etc. I could build my own jack
circuits to do pretty much any option I want. But I still found the
http://www.mojotone.com/amp-parts/amp-jacks/OEM-Stereo-Mono-Cabinet-4x12-Wired-Jack-Plate-Double-1-4
Why not use that? It'll give you stereo, plus mono at two impedances.

That looks like something I might be interested in, but I still have to
wire the speakers. Like I was saying in my previous post, in all the
4x12 wiring schematics for Stereo/Mono setups (that use all 4 speakers
in each mode), the stereo setup doubles the impedance.. since my
speakers are 16ohms, the cab would be running at 32 ohms in stereo,
which isn't compatible with either of my amps.

If you have four 16 ohm speakers with the jack plate that I suggest, you
will have these options:

4 ohms mono
2x 8 ohms stereo
16 ohms mono

Post by adam79
Also, if I decide to add additional wiring in my cab, Can I wire the
speakers over my existing Mono wiring without worrying about the wires
crossing?
Thanks,
-Adam

Adam,

With all due respect, and not trying to offend...

I've answered many of your questions over the years. So have others.

I'm betting that if you spent 20 minutes searching the net and looking
at schematics of speakers, you'd be able to answer this question today,
and never have to ask this type of question again.

But like I said, I know this stuff, and it's still easier to use the
jack plate.

[jim]

Post by adam79

I understand the wiring, schematics, etc. I could build my own jack
circuits to do pretty much any option I want. But I still found the
http://www.mojotone.com/amp-parts/amp-jacks/OEM-Stereo-Mono-Cabinet-4x12-Wired-Jack-Plate-Double-1-4
Why not use that? It'll give you stereo, plus mono at two impedances.

That looks like something I might be interested in, but I still have to
wire the speakers.

The plate has speaker wires coming out of it, with push on connectors.

Post by adam79
Like I was saying in my previous post, in all the
4x12 wiring schematics for Stereo/Mono setups (that use all 4 speakers
in each mode), the stereo setup doubles the impedance.. since my
speakers are 16ohms, the cab would be running at 32 ohms in stereo,
which isn't compatible with either of my amps.
Also, if I decide to add additional wiring in my cab, Can I wire the
speakers over my existing Mono wiring without worrying about the wires
crossing?

Rather than guess as to what you are doing, to avoid miscommunication,
I'd like to see diagrams.

I also recall suggesting two jacks on the cab. Each wired to two
speakers parallel. Each jack 8 ohms.

For mono, simply run TWO speaker cables to the amp and set at 4 ohms.

Post by adam79
Thanks,
-Adam

[adam79]

Post by jim
Rather than guess as to what you are doing, to avoid miscommunication,
I'd like to see diagrams.

I found this diagram (check link below) for a 4x12 Stereo/Mono setup,
for 16ohm speakers, that runs at 8ohms in Stereo and 4ohms in Mono.

Loading Image...

I'm going to use a panel similar to the one that you posted, but w/o a
switch.. In the diagram it says to use one Switchcraft 14B Stereo Jack
for the "stereo" side and a Stereo Jack for the "mono" side.. I'm not
sure what jacks the panel uses that you referenced.

Ideally, I'd like to use this setup, but also keep my current wiring
that runs the cab @ 16ohms in Mono. I found a 3 jack panel just for this
purpose:
http://www.tubesandmore.com/scripts/foxweb.dll/***@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?item=S-H700.
I just have to figure out the wiring scheme for this.

Thanks for the help,
-Adam

[Jim]

Post by adam79

Post by jim
Rather than guess as to what you are doing, to avoid miscommunication,
I'd like to see diagrams.

I found this diagram (check link below) for a 4x12 Stereo/Mono setup,
for 16ohm speakers, that runs at 8ohms in Stereo and 4ohms in Mono.
http://www.colomar.com/Shavano/mono-stereo1.gif

Bigtime typo with that link. It should be use mono PLUGS only.

If you ever just want to use one pair of the speakers, it must be the left.

If you do this, clean jack contacts with DeoxIt every year or so.

If you amp has two speaker input jacks, my suggestion of two NORMAL open
1/4" jacks is better. Why? Because you don't have to worry about the
contacts on that 14B jack. And it's cheaper and easier.

Post by adam79
I'm going to use a panel similar to the one that you posted, but w/o a
switch.. In the diagram it says to use one Switchcraft 14B Stereo Jack
for the "stereo" side and a Stereo Jack for the "mono" side.. I'm not
sure what jacks the panel uses that you referenced.

The advantage to using switches is that you'd get 4 ohm OR 16 OHM mono
options.

Switch contacts are also generally superior to the contacts on the
jacks, and less likely to cause problems.

Post by adam79
Ideally, I'd like to use this setup, but also keep my current wiring
I just have to figure out the wiring scheme for this.

All you need to do is wire the left side PARALLEL, and the right side
PARALLEL. Each side feed is 8 ohms. Then connect the wires as per the
diagram. But this uses the same type of jacks that make me nervous,
unless they are cleaned regularly. I'd much rather trust switches!

Post by adam79
Thanks for the help,
-Adam

[adam79]

Bigtime typo with that link. It should be use mono PLUGS only.
If you ever just want to use one pair of the speakers, it must be the left.
If you do this, clean jack contacts with DeoxIt every year or so.
If you amp has two speaker input jacks, my suggestion of two NORMAL open
1/4" jacks is better. Why? Because you don't have to worry about the
contacts on that 14B jack. And it's cheaper and easier.

For this setup you need a stereo switching jack.

The advantage to using switches is that you'd get 4 ohm OR 16 OHM mono
options.
Switch contacts are also generally superior to the contacts on the
jacks, and less likely to cause problems.

If I want the go with the Stereo/Mono option I only have one choice in
wiring.. the scheme in the diagram. This setup wasn't configured to work
with a switch. If there's a way to alter the diagram for a switch setup,
I wouldn't know where to begin!

Also, when you say that I'll have both 4 or 16ohm mono options with the
switch, it would mean that I'd have to rule out the stereo option, right?

Thanks for all the help,
-Adam

[jim]

Post by adam79

Bigtime typo with that link. It should be use mono PLUGS only.
If you ever just want to use one pair of the speakers, it must be the left.
If you do this, clean jack contacts with DeoxIt every year or so.
If you amp has two speaker input jacks, my suggestion of two NORMAL open
1/4" jacks is better. Why? Because you don't have to worry about the
contacts on that 14B jack. And it's cheaper and easier.

For this setup you need a stereo switching jack.

Did you get this?: If you simply wire two pair of speakers to two
jacks, they don't need to be stereo or switching. But you would have to
run two cables to the amp to run 4 ohms mono. Most amps give you two
output jacks, so it's usually not a problem.

Post by adam79

The advantage to using switches is that you'd get 4 ohm OR 16 OHM mono
options.
Switch contacts are also generally superior to the contacts on the
jacks, and less likely to cause problems.

If I want the go with the Stereo/Mono option I only have one choice in
wiring.. the scheme in the diagram. This setup wasn't configured to work
with a switch. If there's a way to alter the diagram for a switch setup,
I wouldn't know where to begin!

That's why I recommend the plate at the link.

Post by adam79
Also, when you say that I'll have both 4 or 16ohm mono options with the
switch, it would mean that I'd have to rule out the stereo option, right?

No.

That jack plate gives you 4 or 16 ohms mono, *OR* two 8 ohm jacks for
stereo (with 16 ohm drivers).

Post by adam79
Thanks for all the help,
-Adam

[adam79]

Post by jim

Post by adam79
Also, when you say that I'll have both 4 or 16ohm mono options with the
switch, it would mean that I'd have to rule out the stereo option, right?

No.
That jack plate gives you 4 or 16 ohms mono, *OR* two 8 ohm jacks for
stereo (with 16 ohm drivers).

So If I installed the switch panel, and wired two speakers per jack,
would the switch do anything?

[Jim]

Post by adam79

Post by jim

Post by adam79
Also, when you say that I'll have both 4 or 16ohm mono options with the
switch, it would mean that I'd have to rule out the stereo option, right?

No.
That jack plate gives you 4 or 16 ohms mono, *OR* two 8 ohm jacks for
stereo (with 16 ohm drivers).

So If I installed the switch panel, and wired two speakers per jack,
would the switch do anything?

That would be a waste.

Use this plate:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-287

Yeah, it's plastic. But that avoids any problems with using two
separate amps, one on each pair.

And two of these jacks:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=093-104

CHEAP, easy and no switches or make/break jack contacts to worry about!
Simply run two speaker cables to your mono head, set to 4 ohms.

[adam79]

Post by Jim
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-287
Yeah, it's plastic. But that avoids any problems with using two separate
amps, one on each pair.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=093-104
CHEAP, easy and no switches or make/break jack contacts to worry about!
Simply run two speaker cables to your mono head, set to 4 ohms.

Thanks for the info. I have just one more question. I also have a 2x12
cab running at 8ohms. Someone told me that I could run my 4x12 cab
(16ohms) and 2x12 cab (8ohms) together and set the OT tap at 4ohms. Is
this true?

Thanks,
-Adam

[Jim]

Post by adam79

Post by Jim
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-287
Yeah, it's plastic. But that avoids any problems with using two separate
amps, one on each pair.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=093-104
CHEAP, easy and no switches or make/break jack contacts to worry about!
Simply run two speaker cables to your mono head, set to 4 ohms.

Thanks for the info. I have just one more question. I also have a 2x12
cab running at 8ohms. Someone told me that I could run my 4x12 cab
(16ohms) and 2x12 cab (8ohms) together and set the OT tap at 4ohms. Is
this true?
Thanks,
-Adam

I wouldn't worry about either 4 or 8 ohm taps with MOST amps.

16 and 8 parallel = 5.33 ohms

It's closer to 4 ohms than to 8 ohms. It's about 1/3 of a step high
(where an 8 ohm speaker would be a "one step" mismatch when plugged into
a 4 ohm output). It's about 2/3 step low for the 8 ohm output.

The "rule of thumb" is that you're better off running a lower than
expected load on a tube amp. Those people would plug the 5.3 load into
the 8 ohm jack. But honestly, 1/3 of a step high is not a reason to
worry in 99+% of all amps. I might not do it with a vintage Plexi, but
I wouldn't think twice with most other amps -- either 4 or 8 ohms!

BUT, here's the bad (?) news...

2/3 of your amp power is going to go to the 2x12. So each speaker sees
1/3 of the power.

1/3 of the amp power will go to the 4x12 (because of the higher
impedance). So each speaker in that cab??? Well, it only will see
1/12th amp power!

In other words, you're driving the speakers in the 2x12 FOUR TIMES
HARDER than each speaker in the 4x12.

That doesn't mean that you can't do it. But it does mean that the end
result will be closer to the tone of that 2x12 than the 4x12!

No reason not to try it, but expect the 2x12 to dominate.

[adam79]

Post by Jim
I wouldn't worry about either 4 or 8 ohm taps with MOST amps.
16 and 8 parallel = 5.33 ohms
It's closer to 4 ohms than to 8 ohms. It's about 1/3 of a step high
(where an 8 ohm speaker would be a "one step" mismatch when plugged into
a 4 ohm output). It's about 2/3 step low for the 8 ohm output.

The speakers in my 4x12 are rated at 15ohm each, so there's always gonna
be some kind of mismatch.

Post by Jim
In other words, you're driving the speakers in the 2x12 FOUR TIMES
HARDER than each speaker in the 4x12.
That doesn't mean that you can't do it. But it does mean that the end
result will be closer to the tone of that 2x12 than the 4x12!
No reason not to try it, but expect the 2x12 to dominate.

In that case, I might as well just plug it into the 2x12.

[jim]

Post by adam79

Post by Jim
I wouldn't worry about either 4 or 8 ohm taps with MOST amps.
16 and 8 parallel = 5.33 ohms
It's closer to 4 ohms than to 8 ohms. It's about 1/3 of a step high
(where an 8 ohm speaker would be a "one step" mismatch when plugged into
a 4 ohm output). It's about 2/3 step low for the 8 ohm output.

The speakers in my 4x12 are rated at 15ohm each, so there's always gonna
be some kind of mismatch.

Post by Jim
In other words, you're driving the speakers in the 2x12 FOUR TIMES
HARDER than each speaker in the 4x12.
That doesn't mean that you can't do it. But it does mean that the end
result will be closer to the tone of that 2x12 than the 4x12!
No reason not to try it, but expect the 2x12 to dominate.

In that case, I might as well just plug it into the 2x12.

Depends.

When I use my Vintage 30 2x12 (set to 16) and my 70's Hiwatt/Fane 4x12
(16) into my JMP 2204 (set to 8), the Vintage 30 cab is noticeably more
efficient (louder). HOWEVER, the Hiwatt cab compliments the tone of the
other cab, and the end result is better than V30 alone. In reality, I
prefer the Hiwatt cab on it's own over using both cabs. That's because
the Hiwatt cab is dark, and it "just works" with the Marshall head.

[RS]

Post by jim
In reality, I
prefer the Hiwatt cab on it's own over using both cabs. That's because
the Hiwatt cab is dark, and it "just works" with the Marshall head.

Do you know what speakers are in the Hiwatt cab?

[jim]

Post by RS

Post by jim
In reality, I
prefer the Hiwatt cab on it's own over using both cabs. That's because
the Hiwatt cab is dark, and it "just works" with the Marshall head.

Do you know what speakers are in the Hiwatt cab?

They are not the early cast frame. I believe that they are the first
steel stamped Fanes used by Hiwatt. They have purple Hiwatt stickers on
ceramic magnets. IIRC, it's circa 1975 or there abouts.

I also have an early/mid 80's Hiwatt/Fane cab. Those speakers are not
as dark, and more efficient.

Hiwatt has funny labeling. The newer cab is labeled 16 ohms, 100W. So
I bought it hoping for the 25W alnico Fanes. But I got EIGHT ohm 70W
Fanes. All speakers are correct time frame, so I don't know why it's an
8 ohm cab. Possible that an owner swapped when buying, possible that
Hiwatt mislabeled it. They definitely mislabel power handling, and I've
read they do it because it's designed to work with their 100W head!

[jim]

Post by RS

Post by jim
In reality, I
prefer the Hiwatt cab on it's own over using both cabs. That's because
the Hiwatt cab is dark, and it "just works" with the Marshall head.

Do you know what speakers are in the Hiwatt cab?

They are not the early cast frame. I believe that they are the first
steel stamped Fanes used by Hiwatt. They have purple Hiwatt stickers on
ceramic magnets. IIRC, it's circa 1975 or there abouts.

More info: The darker sounding Hiwatt cab is slotted back, but steel
handles in the side. The cabs with alnico 25W seem to have the cut out
slots for handles.

It's been a LONG time since I opened it, but from memory, they are 50W
steel frame with the purple Hiwatt label.

Funny story about the last time I had it open. I had my head against
the cab, looking in. The cab bumped me in the head, and I felt a jolt.
I immediately corrected my dog, thinking that he stood up on the cab
and knocked it into me. Nope. EARTHQUAKE!

I also have an early/mid 80's Hiwatt/Fane cab. Those speakers are not as
dark, and more efficient.
Hiwatt has funny labeling. The newer cab is labeled 16 ohms, 100W. So I
bought it hoping for the 25W alnico Fanes. But I got EIGHT ohm 70W
Fanes. All speakers are correct time frame, so I don't know why it's an
8 ohm cab. Possible that an owner swapped when buying, possible that
Hiwatt mislabeled it. They definitely mislabel power handling, and I've
read they do it because it's designed to work with their 100W head!

[adam79]

Post by jim
When I use my Vintage 30 2x12 (set to 16) and my 70's Hiwatt/Fane 4x12
(16) into my JMP 2204 (set to 8), the Vintage 30 cab is noticeably more
efficient (louder). HOWEVER, the Hiwatt cab compliments the tone of the
other cab, and the end result is better than V30 alone. In reality, I
prefer the Hiwatt cab on it's own over using both cabs. That's because
the Hiwatt cab is dark, and it "just works" with the Marshall head.

I almost bought a 4x12 Hiwatt cab last year, but only 3 of the 4
speakers were Fanes (I think the other one was a G12T-75).. Because of
this, I didn't think it was worth the $700 price tag. Plus, I don't
really need a Full Stack.

The 2x12 cab I have was built by a friend of mine and it's loaded w/
generic Eminence speakers that came with some old Fender cab.. it
doesn't come close to the sound my 4x12 puts out with the G12-65s. I
found a diagram with one jack that uses a 5 Amp DPDT Switch to select
between 4 or 16ohm, Mono (Loading Image...).
I'd rather wire it in a two jack setup, but can't find a diagram for
that. What do you think of the DPDT switches? If I do decide to go that
route, I've been looking online and besides all the different brands to
choose from, there are several different types (i.e. toggle, mini
toggle, rocker).

[Jim]

Post by adam79

Post by jim
When I use my Vintage 30 2x12 (set to 16) and my 70's Hiwatt/Fane 4x12
(16) into my JMP 2204 (set to 8), the Vintage 30 cab is noticeably more
efficient (louder). HOWEVER, the Hiwatt cab compliments the tone of the
other cab, and the end result is better than V30 alone. In reality, I
prefer the Hiwatt cab on it's own over using both cabs. That's because
the Hiwatt cab is dark, and it "just works" with the Marshall head.

I almost bought a 4x12 Hiwatt cab last year, but only 3 of the 4
speakers were Fanes (I think the other one was a G12T-75).. Because of
this, I didn't think it was worth the $700 price tag. Plus, I don't
really need a Full Stack.
The 2x12 cab I have was built by a friend of mine and it's loaded w/
generic Eminence speakers that came with some old Fender cab.. it
doesn't come close to the sound my 4x12 puts out with the G12-65s. I
found a diagram with one jack that uses a 5 Amp DPDT Switch to select
between 4 or 16ohm, Mono (http://www.colomar.com/Shavano/dual4imp1.gif).
I'd rather wire it in a two jack setup, but can't find a diagram for
that. What do you think of the DPDT switches? If I do decide to go that
route, I've been looking online and besides all the different brands to
choose from, there are several different types (i.e. toggle, mini
toggle, rocker).

Toggle switch contacts are far superior to the contacts that are built
into jacks. But not as good as hard wired jacks.

If you do this, pick a full size toggle in a quality brand (like Carling).

As far as current rating: 5A is good for 100W at 4 ohms, so it should
be okay. Nothing says that you can't use a higher current rating.

[Jim]

Post by Jim

Post by adam79

Post by jim
When I use my Vintage 30 2x12 (set to 16) and my 70's Hiwatt/Fane 4x12
(16) into my JMP 2204 (set to 8), the Vintage 30 cab is noticeably more
efficient (louder). HOWEVER, the Hiwatt cab compliments the tone of the
other cab, and the end result is better than V30 alone. In reality, I
prefer the Hiwatt cab on it's own over using both cabs. That's because
the Hiwatt cab is dark, and it "just works" with the Marshall head.

I almost bought a 4x12 Hiwatt cab last year, but only 3 of the 4
speakers were Fanes (I think the other one was a G12T-75).. Because of
this, I didn't think it was worth the $700 price tag. Plus, I don't
really need a Full Stack.
The 2x12 cab I have was built by a friend of mine and it's loaded w/
generic Eminence speakers that came with some old Fender cab.. it
doesn't come close to the sound my 4x12 puts out with the G12-65s. I
found a diagram with one jack that uses a 5 Amp DPDT Switch to select
between 4 or 16ohm, Mono (http://www.colomar.com/Shavano/dual4imp1.gif).
I'd rather wire it in a two jack setup, but can't find a diagram for
that. What do you think of the DPDT switches? If I do decide to go that
route, I've been looking online and besides all the different brands to
choose from, there are several different types (i.e. toggle, mini
toggle, rocker).

Toggle switch contacts are far superior to the contacts that are built
into jacks. But not as good as hard wired jacks.
If you do this, pick a full size toggle in a quality brand (like Carling).
As far as current rating: 5A is good for 100W at 4 ohms, so it should be
okay. Nothing says that you can't use a higher current rating.

I didn't consider CLEARANCE issues when suggesting full size toggle. If
you move your cabs around, you don't want to break the switch. Perhaps
a rocker or slide switch is better, but they are also harder to mount in
a standard jack plate.

[adam79]

I also have a 2x12 cab running at 8ohms. I could run my 4x12 cab
(16ohms) and 2x12 cab (8ohms) together and set the OT tap at 4ohms, right?

2/3 of your amp power is going to go to the 2x12. So each speaker sees
1/3 of the power.
1/3 of the amp power will go to the 4x12 (because of the higher
impedance). So each speaker in that cab??? Well, it only will see 1/12th
amp power!
In other words, you're driving the speakers in the 2x12 FOUR TIMES
HARDER than each speaker in the 4x12.
That doesn't mean that you can't do it. But it does mean that the end
result will be closer to the tone of that 2x12 than the 4x12!
No reason not to try it, but expect the 2x12 to dominate.

If I wired the 2x12 to run at 16ohms and connected it to the 4x12 (also
16ohms) will all the speakers be driven equally?

[jh]

Post by adam79

I also have a 2x12 cab running at 8ohms. I could run my 4x12 cab
(16ohms) and 2x12 cab (8ohms) together and set the OT tap at 4ohms, right?

2/3 of your amp power is going to go to the 2x12. So each speaker sees
1/3 of the power.
1/3 of the amp power will go to the 4x12 (because of the higher
impedance). So each speaker in that cab??? Well, it only will see 1/12th
amp power!
In other words, you're driving the speakers in the 2x12 FOUR TIMES
HARDER than each speaker in the 4x12.
That doesn't mean that you can't do it. But it does mean that the end
result will be closer to the tone of that 2x12 than the 4x12!
No reason not to try it, but expect the 2x12 to dominate.

If I wired the 2x12 to run at 16ohms and connected it to the 4x12 (also
16ohms) will all the speakers be driven equally?

???

new speakers?

I can't see one single way to convert a 2+12 woth 8ohms to 16ohms by
rewiring it?

If there is such a way - please tell me...


There is a way to "equal" the load on your speakers. I assume they are
16ohms in parallel.
Hook them up in series, so you got a 32ohm cab and operate them paralell
to the 16 ohm 4x12.
Now you got three 32ohm chains in parallel - for the ohms - do the math.


regards

Jochen

[Jim]

Post by adam79

I also have a 2x12 cab running at 8ohms. I could run my 4x12 cab
(16ohms) and 2x12 cab (8ohms) together and set the OT tap at 4ohms, right?

2/3 of your amp power is going to go to the 2x12. So each speaker sees
1/3 of the power.
1/3 of the amp power will go to the 4x12 (because of the higher
impedance). So each speaker in that cab??? Well, it only will see 1/12th
amp power!
In other words, you're driving the speakers in the 2x12 FOUR TIMES
HARDER than each speaker in the 4x12.
That doesn't mean that you can't do it. But it does mean that the end
result will be closer to the tone of that 2x12 than the 4x12!
No reason not to try it, but expect the 2x12 to dominate.

If I wired the 2x12 to run at 16ohms and connected it to the 4x12 (also
16ohms) will all the speakers be driven equally?

With a 2x12 and 4x12 of the SAME impedance:

Half of the amp power will go to each cab.

But one of our cabs has twice as many speakers, right? So that means
that each driver in the 2x12 gets 1/4 power, and each driver in the 4x12
gets 1/8 power.

The power/driver is most important when figuring power rating (you can
only use the above setup if the amp does not exceed 4x the power rating
of the driver in the 2x12.)

Actual loudness of the cabs depends on cab designs, and whether you're
using the same drivers in each cab (sensitivity, or sound output per
watt, varies between speakers).

Your original question was different because we were comparing a 16 ohm
cab to an 8 ohm cab.

[adam79]

Post by Jim

Post by adam79
If I wired the 2x12 to run at 16ohms and connected it to the 4x12 (also
16ohms) will all the speakers be driven equally?

Yes.

Post by Jim
Half of the amp power will go to each cab.
But one of our cabs has twice as many speakers, right? So that means
that each driver in the 2x12 gets 1/4 power, and each driver in the 4x12
gets 1/8 power.
The power/driver is most important when figuring power rating (you can
only use the above setup if the amp does not exceed 4x the power rating
of the driver in the 2x12.)
Actual loudness of the cabs depends on cab designs, and whether you're
using the same drivers in each cab (sensitivity, or sound output per
watt, varies between speakers).
Your original question was different because we were comparing a 16 ohm
cab to an 8 ohm cab.

Yeah. I was just curious about the power distribution. Thanks for the info.

[Jim]

Post by adam79
Hi. I have a 4x12 Marshall 1960a Cab w/ four 15ohm Celestion G12-65s; I
currently have it wired for 15ohms mono. Why do companies make 15ohm
speakers when every output transformer only has 16ohm taps?

If you tracked the impedance of that 15 ohm speaker in your cab, it
would be well over 50 ohms at the primary frequency of open low E, under
15 in a small band, and then high again in the upper harmonic range.

Impedance is a NOMINAL rating. There is no significant difference
between a 15 ohm and 16 ohm speaker.

Post by adam79
Anyways,
onto my main question..
I want to rewire my Cab for Mono/Stereo use. I recently bought an Ampeg
V4; the OT taps only run at 2, 4 or 8ohms (I talked to the tech that has
my amp and he said that there isn't a 16ohm tap on the OT in the V4). Is
there a way to wire the 15ohm speakers so they are compatible with said
OT when running in Stereo and Mono? I assume it would be easier to
install a second input jack rather than use a DPDT switch.

You could pick up the recent Marshall jack plate. That would give you 4
or 16 ohms mono, 2x 8 stereo.

Post by adam79
Would it be a dumb idea to wire only two speakers at a time (i.e.
connect two speakers to their own jack, so it would be like running two
2x12s inside the 4x12 cab)?

For your purpose, you could put two jacks on two sets of parallel
speakers. 8 ohms each (don't worry about it being 7.5, it really is NO
difference in practice). Then just run two cables to your amp with the
amp set at 4 ohms for mono! If your amp doesn't have two speaker jacks,
build a box or a Y cable. Don't trust the cheap Y adapters for speaker
use! There may be quality options, but make SURE that they are able to
handle high current.

Post by adam79
My other amp is a Peavey VTM-120, which has speaker outputs for 2,4,8
and 16ohms. Are there any advantages or disadvantages when wiring 16ohm
speakers to run at 4ohms?

ADVANTAGE: All speakers are in parallel. If one burns a voice coil,
there is less of an impedance mismatch, and less chance that a second
will burn out. There may be increased damping factor, but not
significant for tubes and guitar.

DISADVANTAGE: You're not using all of your output transformer
secondary, but that SHOULD be a non-issue for any properly designed
transformer.

Post by adam79
Thanks,
-Adam

[WB]

Post by Jim
it
would be well over 50 ohms at the primary frequency of open low E, under
15 in a small band, and then high again in the upper harmonic range.
Impedance is a NOMINAL rating. There is no significant difference
between a 15 ohm and 16 ohm speaker.

Nice note ! Impedance varies at the speaker because it is
a combination of inductance/resistance/capacitance based
on the frequency at any given instance.