Can I Safely Run These Simultaneously???

Jethro Rocker said:
I did mantion that a couple times that an extra cab would have to be added as per your posts! I am so sorry to hear about your friend. No snippiness seen on my end. I was trying to make it work without adding yet more speakers. I heve never seen that Radial cab box, it is cool!

4x12 speakers have to be either 16 or 4ohms. Lamentably!
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I do have two cabs that are anomalies then: the Marshall Mode Four MF400s. They are Celestion G12-K100s and are in fact, 8ohms believe it or or not lol the cabs are factory wired into series-parallel and are single input rated at 8ohm.

There is a model of the Celestion G12T-75s that are 8ohm rated as well but very uncommon as most are 16ohm.
 
smitty_p said:
Well, there is a way to do that...sorta...

A high wattage resistor could be soldered in parallel with the speaker terminals. A 16 ohm resistor soldered across the terminals of a 16 ohm speaker will "look like" 8 ohms to the amplifier.

However, this is not a perfect solution and has some caveats:

First, the energy flowing through the resistor will be dissipated as heat. It will not actually do anything.

Second, the speaker will be quieter as less energy will actually flow through the speaker, being dissipated across the resistor instead.

Third, a really high wattage resistor is necessary, like one of the big, ceramic, power resistors.

Fourth, a resistor is not reactive like a speaker, so it will not behave exactly the same as two speakers in parallel.

Fifth, wiring a resistor in this fashion essentially creates a parallel RL (resistive - inductive) circuit consisting of the resistor, itself, and the speaker coil. Consequently, this may affect the tone somewhat as the resistor may introduce some damping effects.

So, yeah....
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So possible but pretty difficult and complex, right? Lol pretty awesome you know about this though!
 
Clockworkmike said:
I do have two cabs that are anomalies then: the Marshall Mode Four MF400s. They are Celestion G12-K100s and are in fact, 8ohms believe it or or not lol the cabs are factory wired into series-parallel and are single input rated at 8ohm.

There is a model of the Celestion G12T-75s that are 8ohm rated as well but very uncommon as most are 16ohm.
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Oh sorry i worded that wrong. The speakees in said Jackson cab have to be 4 or 16, not in general. There are far more 8 ohm speakers available than 4 ohms.
I have 2x8 ohm speakers in my TSL
 
Jethro Rocker said:
Oh sorry i worded that wrong. The speakees in said Jackson cab have to be 4 or 16, not in general. There are far more 8 ohm speakers available than 4 ohms.
I have 2x8 ohm speakers in my TSL
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Hey man no worries lol i honestly dont know how many speakers out there are this impedance or that, just what ive played through and its really only ever been 3 different speaker types.

You clearly know your stuff and got your act together on this sorta thing!
 
Clockworkmike said:
Hey man no worries lol i honestly dont know how many speakers out there are this impedance or that, just what ive played through and its really only ever been 3 different speaker types.

You clearly know your stuff and got your act together on this sorta thing!
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Screwed up an old SS PA amp in about 1980 by not knowing impedances. Learned it then and always check impedances before hooking up equipment! I have fiddled around with changjng oiy speakers heren there too.
Cheers!
 
ivan H said:
Sorry to hear of your loss BDon, deepest condolences.

BDon is onto it here, there is no way this can be done without adding another 8 ohm cab into the equation.

This is just what I have found when Ive tried using more than a single 4x12 with a 50 watt head Robert. Two 4x12's paralleled (8 ohm total load & selected at amp) does not give the same amount of "grind" as I get using a single 4x12 (16 ohm load & 16 ohms selected at amp). The 4x12 (Marshall) cabs are a 1960AV & a 1960BV, both 16 ohm Greenback loaded. I'm only guessing on why, but Im thinking it's because the speakers aren't distorting as much with 8 speakers used as when only 4 are used. I could be wrong on that though & it may have something to do with how the amps OT works in conjunction with the speakers at different impedance settings, ie;
16 ohm = highest voltage & lowest current output.
8 ohm = lower voltage & higher current output.
4 ohm = lowest voltage & highest current output.
Again, I'm only guessing at the reason behind the difference in how it sounds, but I have found the same when I tried this with a couple of 50 watt heads. Cheers
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Interesting!!!

Thanks to all of you who took time out to contribute to this thread.
 
Robert, you could consider hooking the cabinets to the amp through your Weber attenuator. Weber attenuators have what Weber claim to be a "swamped" output impedance, allowing any impedance cab to be used. You wouldn't need to attenuate (turn the attenuator's speaker volume right up). Maybe contact Weber to ask their advice before trying it though. Just a thought. Cheers
 
Jethro Rocker said:
Screwed up an old SS PA amp in about 1980 by not knowing impedances. Learned it then and always check impedances before hooking up equipment! I have fiddled around with changjng oiy speakers heren there too.
Cheers!
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I did the same damn thing to not one but two Marshall Mode Fours! I posted about it at #27. Embarrassing now when i look back but i didnt know any better then. Live and learn
 
Clockworkmike said:
I did the same damn thing to not one but two Marshall Mode Fours! I posted about it at #27. Embarrassing now when i look back but i didnt know any better then. Live and learn
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Geez, Man...I accidentally hooked up my 8 ohm cab to my 16ohm output (on a dark stage) and played 4 hours at master volume 7-8, so now I am just expecting it to blow up any minute..

Funny thing, I saw a guy (another band whom we know) playing with an Origin 50H and running two cabinets.

He had an 8 ohm 4x12 plugged into the 8 ohm output and a 16 ohm 1x12 plugged into the 16 ohm amp output of the head!!!!!

The cabinets were not connected, he was powering each can with a separate output on the head.

This is where I got the idea to try and run my cabinets together.
 
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Robert Herndon said:
How long did it take to cause the damage???
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First head? 15mins after i got it home lol bought a full stack Marshall Mode Four 350w head with two MF400B cabs brand new ( those cabs cant be used in a full stack due to impedances, DESPITE being made specifically for that amp, smart move huh?). Cranked it up to about 7 and POP! Freaked out and called the store, they laughed and said bring it back and grab another. Got the second one, it lasted about 3 months and happened again.

That time, it ended up at an authorized repair center and the dude called me and said " WHAT THE F$!K DID YOU DO THIS AMP?!?" I genuinely didnt know, thought it was meant to play both of those cabs. He fixed it and shipped it back and it worked in that SAME configuration for a few years until i realised it wasnt supposed to work like that. I got in a half stack now, which is how its supposed to work with a MF400 cab. The other MF400 cab is underneath a 1960A Cab into a JCM2000 which is the correct impedance.

Apparently, in order to run that head into a full stack? You need two 16ohm cabs. Marshall made another matching cabinet for it called the MF240 which had Vintage 30s and you could use two of those. The amp is weird because if you plug a single 16ohm cab, it switches power down to 235w. If you use a single 8ohm, it delivers the full 350w or can deliver the full 350w if it has two 16 ohm cabs.

Weird thing lol
 
Clockworkmike said:
First head? 15mins after i got it home lol bought a full stack Marshall Mode Four 350w head with two MF400B cabs brand new ( those cabs cant be used in a full stack due to impedances, DESPITE being made specifically for that amp, smart move huh?). Cranked it up to about 7 and POP! Freaked out and called the store, they laughed and said bring it back and grab another. Got the second one, it lasted about 3 months and happened again.

That time, it ended up at an authorized repair center and the dude called me and said " WHAT THE F$!K DID YOU DO THIS AMP?!?" I genuinely didnt know, thought it was meant to play both of those cabs. He fixed it and shipped it back and it worked in that SAME configuration for a few years until i realised it wasnt supposed to work like that. I got in a half stack now, which is how its supposed to work with a MF400 cab. The other MF400 cab is underneath a 1960A Cab into a JCM2000 which is the correct impedance.

Apparently, in order to run that head into a full stack? You need two 16ohm cabs. Marshall made another matching cabinet for it called the MF240 which had Vintage 30s and you could use two of those. The amp is weird because if you plug a single 16ohm cab, it switches power down to 235w. If you use a single 8ohm, it delivers the full 350w or can deliver the full 350w if it has two 16 ohm cabs.

Weird thing lol
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Hopefully, the Origin series are made for dummies like me...
 
Clockworkmike said:
First head? 15mins after i got it home lol bought a full stack Marshall Mode Four 350w head with two MF400B cabs brand new ( those cabs cant be used in a full stack due to impedances, DESPITE being made specifically for that amp, smart move huh?). Cranked it up to about 7 and POP! Freaked out and called the store, they laughed and said bring it back and grab another. Got the second one, it lasted about 3 months and happened again.

That time, it ended up at an authorized repair center and the dude called me and said " WHAT THE F$!K DID YOU DO THIS AMP?!?" I genuinely didnt know, thought it was meant to play both of those cabs. He fixed it and shipped it back and it worked in that SAME configuration for a few years until i realised it wasnt supposed to work like that. I got in a half stack now, which is how its supposed to work with a MF400 cab. The other MF400 cab is underneath a 1960A Cab into a JCM2000 which is the correct impedance.

Apparently, in order to run that head into a full stack? You need two 16ohm cabs. Marshall made another matching cabinet for it called the MF240 which had Vintage 30s and you could use two of those. The amp is weird because if you plug a single 16ohm cab, it switches power down to 235w. If you use a single 8ohm, it delivers the full 350w or can deliver the full 350w if it has two 16 ohm cabs.

Weird thing lol
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The different outputs at different impedances are because the Mode Four is a Solid State amp.
 
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