412 x pattern wiring - help!

moz91 · September 2013

Alright! Has anyone got a diagram of the correct/best way to wire up a 412 cab to run at
16 ohms with 2 v30s and two t75s (both 16ohms) in an X-Pattern. I'm not all that clued up on cab wiring, could do with some help!
Also what sort of wire should I be using for this? Got some 2.5mm maplins speaker wire if that's any good...
Thanks in advance!

ecc83 · September 2013

I presume you mean a V30 (say) top right and bottom left, other way for the 75's?

This does not affect the wiring, just wire two units in parallel, + to + , - to - and put the pairs in series.

Tip of jack + then - to + linked, - to jack sleeve.

Some say putting the speakers in series first THEN in p'llel sounds different. I would argue against that (as indeed I am sure would Mr Ohm!) since I have never seen any objective evidence that this is the case.

Wire? (fergot!) That Maplin wire will be fine if overkill for rock'n'roll! 5amp mains cable is perfectly adequate here. Make sure you cable tie the wires to together and to the chassis to prevent it rattling. DON'T use lekkies PVC tape as it goes all sticky with age.

Personally I would use crimp receptacles for the speakers. If you can't beg a crimp tool you can use pliers and if you like then solder the wire on (the crimp NOT the speaker!)

N.B. Celestion speaker terms' are not the obvious and common 6mm/1/4" jobbies but 5mm. Maplin have them.

Dave.

ICBM · September 2013

moz91 said:

Alright! Has anyone got a diagram of the correct/best way to wire up a 412 cab to run at
16 ohms with 2 v30s and two t75s (both 16ohms) in an X-Pattern. I'm not all that clued up on cab wiring, could do with some help!
Also what sort of wire should I be using for this? Got some 2.5mm maplins speaker wire if that's any good...
Thanks in advance!

Normally you either want to wire it parallel-series (two series pairs in parallel) which is the standard vintage Marshall way, or series-parallel (two parallel pairs in series) which is the modern way on the cabs with the switching panel.

Wiring:

From the tip terminal of the jack to the positive terminals of both upper speakers.

From the sleeve terminal of the jack to the negative terminals of both lower speakers.

From the positive terminals of both lower speakers to the negative terminals of both upper speakers - this is the one that decides whether it's series-parallel or parallel-series: two vertical wires, separately on each side - parallel-series; three wires, two horizontal and one vertical - series-parallel.

If you're going for a more modern sound - which I'm guessing you are from the speaker choice - then I would go for series-parallel; it's also slightly simpler to wire for an x-pattern while avoiding putting dissimilar speakers in series, which is generally thought to be less desirable than in parallel. If you do want to do parallel-series then the two vertical wires now become an X, which is probably where the name comes from...

ecc83 said:
Some say putting the speakers in series first THEN in p'llel sounds different. I would argue against that (as indeed I am sure would Mr Ohm!) since I have never seen any objective evidence that this is the case.

There is a difference. It's not Mr Ohm you need to think about, it's Mr Speaker Damping

.

Obviously it's true that the total impedance is the same in both cases, but the series and parallel impedances that each speaker sees are totally different. You can test it very simply with a switch to make or break the 'third wire' in the middle.

I'd guess it makes more of a difference with mixed combinations than four identical speakers too, although that's not easy to test without two cabs.

moz91 · September 2013

Never did like physics....

https://www.google.co.uk/search?q=4x12+series+parallel+x+pattern&hl=en-GB&source=lnms&tbm=isch&sa=X&ei=Tsc9UpGjIKfX0QWuu4GoAw&ved=0CAcQ_AUoAQ&biw=1366&bih=643&dpr=1#facrc=_&imgdii=_&imgrc=TnXHjRsu1pdFQM%3A%3Bbd4mqE_ziKqNLM%3Bhttp%253A%252F%252Fi5.photobucket.com%252Falbums%252Fy190%252Fvintagekiki%252Fdownload%252FS-Pwircab.jpg%253Ft%253D1209149997%3Bhttp%253A%252F%252Fvintageamps.com%252Fplexiboard%252Fviewtopic.php%253Ff%253D1%2526t%253D72913%3B1161%3B810

Series Parallel seems the way to go, am I right in thinking the above link is right? The Series Parallel X-Pattern Option on the right of the photo?

I'm not going for a mega heavy sound. Cab is to be used with a JCM900 so its pretty hi gain but not modern metal. Just thought i'd give this a try - 4x75's lacks mid range, 4xv30's has too much mid and sounds really 'boxy'... This seems like a feasible solution!

Didn't realise the difference between Series/Parallel and Parallel/Series made a difference tonally? I get that I should have a pair of v30's and a pair of 75's wired together, but how does it make that much difference whether they're in parallel or series when ultimately the end result is the same?
Don't doubt you (ICBM - fountain of all amp knowledge as far as i'm concerned!), just intrigued more than anything!

ICBM · September 2013

moz91 said:
Series Parallel seems the way to go, am I right in thinking the above link is right? The Series Parallel X-Pattern Option on the right of the photo?

It's basically correct but unnecessarily complicated. Just use the left-hand diagram - which is the same as I described except turned on its side.

If anything their diagram for x-pattern might be counterproductive because it then puts mismatching pairs (of matching speakers) in series, which is sometimes thought to be a bad thing. The simpler method gives two mismatching parallel pairs (not a bad thing) wired in series.

moz91 said:
Didn't realise the difference between Series/Parallel and Parallel/Series made a difference tonally? I get that I should have a pair of v30's and a pair of 75's wired together, but how does it make that much difference whether they're in parallel or series when ultimately the end result is the same?

It does, but far less than the difference between the speaker types.

If four 75s is 1, four V30s is 10, the difference between series-parallel and parallel-series is probably in the 5 vs 6 region... if that makes sense.

moz91 · September 2013

Right I think I'm getting it (really do hate wiring)

So basically (if I put the speakers in an X Pattern - V30 top left and bottom right, T75 opposite), I'm wiring two series pairs consisting of 1 v30 and 1 t75, then wiring the 2 pairs together in parallel?

ICBM · September 2013

moz91 said:

Right I think I'm getting it (really do hate wiring)
So basically (if I put the speakers in an X Pattern - V30 top left and bottom right, T75 opposite), I'm wiring two series pairs consisting of 1 v30 and 1 t75, then wiring the 2 pairs together in parallel?

No, other way round

. You're wiring two parallel pairs of a V30 and a 75, then putting the pairs in series.

moz91 · September 2013

ICBM said:

moz91 said:

Right I think I'm getting it (really do hate wiring)
So basically (if I put the speakers in an X Pattern - V30 top left and bottom right, T75 opposite), I'm wiring two series pairs consisting of 1 v30 and 1 t75, then wiring the 2 pairs together in parallel?

No, other way round . You're wiring two parallel pairs of a V30 and a 75, then putting the pairs in series.

Right, and that's Series Parallel or Parallel Series? This is where I get confused, you see!

ICBM · September 2013

moz91 said:
Right, and that's Series Parallel or Parallel Series? This is where I get confused, you see!

Series parallel.

It's not hard to get confused, most people call *both* schemes "series-parallel" (probably because it sounds more natural, two syllables followed by three), but is usually wrong since most vintage cabinets are wired parallel series (one less wire, saves money and time!).

moz91 · September 2013

Right, I think i'm starting to get it now...

Don't suppose you've got a diagram or anything? There are millions online, all ever so slightly different.... If I've got a picture, I almost certainly wont 'feck it up... If I follow instructions then I probably will!

ICBM · September 2013

The one on the left in the link you posted is the one you need.

http://i5.photobucket.com/albums/y190/vintagekiki/download/S-Pwircab.jpg

Don't worry about it being an x-pattern, the physical location of the speakers in a parallel pair doesn't matter, so if you're using series parallel the wiring is exactly the same as for four identical speakers.

moz91 · September 2013

I'll give it a go, thanks again

moz91 · September 2013

So it doesn't matter that each (parallel) pair has one of each speaker? I'm slowly starting to get this now!

ICBM · September 2013

moz91 said:

So it doesn't matter that each (parallel) pair has one of each speaker? I'm slowly starting to get this now!

It doesn't matter - it's series wiring where it does (or might).

The theory is that in a series connection, if the resonant frequencies (where the impedance rises to a high value) of the two speakers are different, the resonance of each one will 'block' the other at that frequency. I'm not sure I've ever seen any proof that it's a genuine problem though - possibly because most guitar speakers have very similar resonant frequencies.

But by putting the mismatching speakers in parallel, the problem is avoided since the current will simply bypass the speaker which is at its resonant frequency by going through the other one. So in your mixed four, you want each pair to be two mismatching speakers in parallel, not in series, and then connect what is effectively two of the *same* pairs in series.

Confused? I don't blame you

.

moz91 · September 2013

See that makes sense; basically running two of the same in series!

Really appreciate your help... Who needs music radar

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412 x pattern wiring - help!

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