Proper speaker quad wiring?

[Leo_Gnardo]

That is what high-fiber bran muffins are for, to provide extra reading time.

While consuming, or, ahem, the "final act" of digestion?

I keep my attention on an entirely different variety of muffin...

[The Dude]

Yes but be careful.

According to the Mayo Clinic regarding hemorrhoids:

Avoid long periods of sitting. Sitting too long, particularly on the toilet, can increase the pressure on the veins in the anus.

[Enzo]

That is what high-fiber bran muffins are for, to provide extra reading time.

[J M Fahey]

Not such a bad place to catch up with delayed reading.
I'm rereading "The Maltese Falcon" bit by bit , just by leaving a copy there on a shelf
Only problem is that it's hard to put the book down in the middle of a mystery or action part.

Oh well

[cbarrow7625]

Ah, the example given uses 4 ohm drivers, not 8 ohm. when 1 speaker in a parallel pair goes out you get 4 ohms, the other parallel pair is 2 4 ohm speakers in parallel so that's 2 ohms, 2 ohms plus 4 ohms in series is 6 ohms... providing I got my math right.

Well, that's what I get for reading and replying while on the porcelain throne. Let's just say I was distracted.....also, not a great place to work out math in your head. J M is completely correct.

[imaradiostar]

Appearances can be deceiving. Eric is very open about his equipment and it's been well documented at this point. His "lead" marshall sits atop the stacked 4x12 cabinets. There is another marshall set up with 6l6 tubes that sits on a chair behind the amps. One head per cab, each for a dedicated sound.

Jamir

[J M Fahey]

Probably, plus there's an added factor: he may be using a couple heads with old tubes there; not that he "bought worn used tubes for Mojo", quite the contrary, he's *adding* Mojo to them by playing

I very much doubt he reads My Gear Page or My LesPaul Forums to follow the latest trend, rather I feel he´ll stick to his faithful workhorses the way we love an old comfortable pair of shoes .

What's the point? : old (good) tubes don't die a violent death but simply loose emission along years (as if you were adding an attenuator) but still sounding good, even smoother like good wine.

I often find 100W Marshalls imported in the 90's still working, but putting out *nowhere* near 100W .... which by the way is fine

I have seen some down to only 50W RMS (real power on the bench) , a Fender Twin Reverb with original Sylvanias bought in '83 putting out clean 40W, and so on.

Eric Johnson might be in that league.

FWIW Eddie Van Halen said he *loved* an old worn Marshall head he had used in his youth, it belonged to a Club where he played often when he was in High School.
When he became rich and famous, he went back and bought it from the now ageing owner, and used it "as is":
His Tech tried to retube it, it was impossible because tube pins and sockets had become a sigle piece of rust.
No way to pull them except by destruction.

A couple years later he has sockets replaced, so he could plug new tubes in ....... and boy, was he disappointed !!!! It had lost all of the smooth as thick coffee and cream sound it had before.

So maybe there's your answer.

EDIT: just watched:
http://youtu.be/oY4onujPitc
At 4:33 minutes you can clearly see his Marshall head driving *two* vintage (lighter cloth) Marshall cabinets, which of course is the Factory approved way.
There's also 2 "Twins" on the floor which are used at the end for some clean reverb drenched riffs.
He either has a footswitch controlling a relay to switch amps or he always plays into all 3 all the time and the Soundman chooses which one to send to the Public.
And a lot of fine playing.

[bob p]

I don't think he runs his amp at 11, does he?

[imaradiostar]

have 4 "Grenbacks", 20W RMS if original; 25W RMS each if reedition.
As they print in the label "25W .... period" because they use old technology untreated brown Kraft paper coils , glued with nitro lacquer.
If you use one of these cabinets with a 100W head, full tilt (specially the non master volume ones), *definitely* you won't finish your show , not even a rehearsal.

I wonder how Eric Johnson gets through a show? Last I checked he uses 4 old low power speakers with a 100 watter all the time. I'm not saying that to be a smartass, I'm just wondering what the difference is.

Jamie

[bob p]

Open drivers? I see blown greenbacks in half-stacks all the time. It tends to happen when people pull the OEM speakers out of their 1960 cabs and put greenbacks in their place ... especially if they drive them with a 4-tube head.

Lately the problem has been one of idiot bass players blowing up their vintage drivers/cabs. They like to blow up Mesa / EV cabinets by going out and buying a kilowatt Class-D amp and driving the shit out of them.

Doug must have a kinder, gentler clientèle up there in Grand Rapids.

[The Dude]

One thing that hasn't been discussed yet is phasing. When a speaker blows does not the cone movement become opposite of the working speakers in a sealed enclosure- i.e. passive radiator? I would think this effect would be less noticeable with only one nonworking driver as opposed to two. An argument for not using two series loads wired in parallel.

Edit: After further reading, I see this HAS been discussed/pointed out already......My bad. (Sorry Leo!)

[J M Fahey]

I have never considered one of the drivers in a 4x12 going open to be a major concern. I can't say I have seen it happen very often in my career.

Maybe I work with wilder musicians, because I have, many times.
*Specially* when they couple a "vintage" cabinets (80W RMS) with a 100W head and drive it through the roof with distortion, dropped tunings, etc.
These are my customers "La Renga" playing in Buenos aires "River Plate" Football (soccer) Stadium for 48000 people.

You see 4 x 100/120W heads (a Marshall, a Mesa Boogie and 2 Matchless) and 4 stacks.
Second and third, "Modern" , black front cloth, have 4xG12T75 each, total 300W RMS, you'll *hardly* see one of them blown, but cabinets 1 and 4, "vintage", "salt and pepper" checkered cloth (appears grey from a distance), have 4 "Grenbacks", 20W RMS if original; 25W RMS each if reedition.
As they print in the label "25W .... period" because they use old technology untreated brown Kraft paper coils , glued with nitro lacquer.
If you use one of these cabinets with a 100W head, full tilt (specially the non master volume ones), *definitely* you won't finish your show , not even a rehearsal.

[Enzo]

I have never considered one of the drivers in a 4x12 going open to be a major concern. I can't say I have seen it happen very often in my career.

[J M Fahey]

Wait a second. If one of a parallel pair of drivers dies, the impedance of that pair changes to that ofbhe single remaining driver; 8 ohms. You are left with 8 ohms in series with 4 ohms. That is 12 ohms, not 6.

The example used 4 ohms speakers.

The voltage across the 8 ohm speaker will increase, but since the impedance of that driver, and the system, also increase

Why would the impedance of each driver increase?

there should be no significant change in power dissapation in that driver.

But its dissipation *will* increase, please check the Math above.

The other pair of drivers would receive less voltage and have lower dissapation as well.

True, and Math confirms that.

3 cones moving air at a lower power draw vs. 2 cones moving air becomes somewhat of a statistical dead heat. One will be slightly more than the other, but shouldn't be enough to easily detect with thebhunan ear.

In the ecample, 2 working cones will receive 100W and movehalf the air as before.
To understand this better, consider the original cabinet as made out of 2 "half cabinets", each dooing 50% of the work.
Disabling one of them will leave the other still doing its 50%.

While connected the other way, the power loss would be somewhat less but power gets concentrated in a single speaker which will soon collapse.

The fundamental mistake here is assuming one configuration changes to 8 ohms and the other to 6 ohms. The series pairs paralleled does change to 8 ohms but if one driver goes out in the parallels put in series, the I mprdance goes up to 12 ohns, not down to 6 ohms.

Sorry but your fundamental mistake is erring the impedance value .

Long story made short, they are both equally acceptable and safe under the condition described.

Sorry but they are definitely not equally safe.
In fact the connection you suggest is inherently unsafe.

Please recheck the Math above.
It's not a matter of opinion.

[Sowhat]

Good to see you posting Sowhat, you're too rarely seen around here.

I only chime in when I got something to say, be it something stupid or just mindlessly ignorant. I get real busy most of the time with all the busted gear out here in SoCal. Only once in a great while does something dawn on me to be worthy of sharing in such a respected, trusted and esteemed forum... and I really mean that. MEF is the best no nonsense repository of music gear wisdom anywhere on the planet. It's bailed me out countless times.