50w Cab and 100w Head

Kais

New member
Just got a 100w Marshall tube head, didn't really want 100w but it was cheaper than the 50w. I'm running a 2x12 cab with greenbacks, should I be concerned about cranking up?
 
Re: 50w Cab and 100w Head

Yes. If you don't go too loud, it might be ok, but the rule of thumb is to use twice the amount of speaker wattage as your amp puts out. Be careful!!
 
Last edited:
Re: 50w Cab and 100w Head

yes.
two greenbacks is rated for 50 watts.
You will exceed their manufacturers specifications and run the risk of blowing them both.
 
Re: 50w Cab and 100w Head

I wouldn't risk it at more than bedroom volumes. WGS has some great options for very reasonable prices
 
Re: 50w Cab and 100w Head

Yeah, considering your Marshall head really runs closer to 200w at full volume, I wouldn't turn it up over a quarter of the way...
 
Re: 50w Cab and 100w Head

ah ok. I cranked it to 5/10 yesterday and it was sounding awesome, but then I noticed it was rattling a bit. Probably shouldn't do that again. I shall probably upgrade to creambacks
 
Re: 50w Cab and 100w Head

I would be very careful even running a 50-watt Marshall tube amp into a pair of Greenbacks. 100 watts is just asking for grinding noises,smoke, and reconing.
 
Re: 50w Cab and 100w Head

in case you are goin to keep that cab for that head only, you can go for series/parallel circuit with power resistors to cope up with the extra wattage
 
Re: 50w Cab and 100w Head

I just use one of my attenuators when I'm running a head rated at a higher-wattage than the speakers. I've done this with H30s and Greenbacks with no issue. But be careful... because these speakers are known for blowing when overloaded.
 
Re: 50w Cab and 100w Head

I wouldn't risk it at more than bedroom volumes. WGS has some great options for very reasonable prices

Yep agree here with both. What will happen is the speakers will over heat and the voice coils will start bubbling in the coating if you push it. Keep the volume down until you can get some higher wattage speakers.
I second looking at WGS as I absolutely love the tones I'm getting with the WGS ET 90 and Retro 30 I have in my Zinky Velvet and Blackstar 1/12 cab right now.
By themselves both sound really good and both replaced Celestians but together they are awesome! The ET 90 replaced a heritage in the Velvet and the Retro bested both the stock 70/eighty and a older Brit built Vintage 30 in a head to head tone shoot out tone in the Blackstar.
Here is the set up running live and unmiced in a larger room.
 
Last edited:
Re: 50w Cab and 100w Head

hmmm...please elaborate

i would love to, essentially it's about adding a DIY dummy load whilst having the cab in the mix allowing you to run the head at its full power. to do the elaboration i'll need to know how the 2x12 cab has its speakers wired. assuming its 8 ohmer greenbacks inside, is the cab impedance rated at 4 ohms or 16 ohms?
 
Re: 50w Cab and 100w Head

i would love to, essentially it's about adding a DIY dummy load whilst having the cab in the mix allowing you to run the head at its full power. to do the elaboration i'll need to know how the 2x12 cab has its speakers wired. assuming its 8 ohmer greenbacks inside, is the cab impedance rated at 4 ohms or 16 ohms?

yes the cab is at 16olms
 
Re: 50w Cab and 100w Head

yes the cab is at 16olms

meaning that the two 8 ohmer greenbacks are in series, making the total impedance 16 ohms.

solution (1);
if you can put a 16 ohm power resistor (with 100W rating) in parallel with the cab you endup having total impedance of 8 ohms and the whole thing capable of handling 100W.
DIYDummy.jpg

however heeding the aforementioned warnings;

but the rule of thumb is to use twice the amount of speaker wattage as your amp puts out. Be careful!!
Yeah, considering your Marshall head really runs closer to 200w at full volume

the second solution would be;
put a 8 ohm power resistor (with 150W rating) in parallel with the cab now having total impedance of 5.33 ohms.
DIYDummy2.jpg

the second solution will require the head to have 4 ohm speaker/cab out. if the output power of the head is at 100W the speakers will only get a 16.67 watt load (well below its power rating) each while the power resistor will get 66.67 watts of load, meaning there is that tolerance for the head to go over 100W and still not cook the speakers in the process.

BTW the powers resistors would require heat sinks, and hence would require some sort of enclosure to fix them in.
 
Re: 50w Cab and 100w Head

How do you go about attaching the heat sinks to the resistors? I'm imagining some thermal paste and cheap old CPU heat sinks would probably work OK.
 
Re: 50w Cab and 100w Head

How do you go about attaching the heat sinks to the resistors? I'm imagining some thermal paste and cheap old CPU heat sinks would probably work OK.
you'll need those heat sinks used for power transistors, as for attachment you can use gud ole nut & bolt with some thermal paste. these are power resistors not those tiny critters

8a00b10f9c5974e59cd95ab32d8eaa88.jpg

HS-420x240.png


Sent from my XT1033 using Tapatalk
 
Last edited:
Re: 50w Cab and 100w Head

meaning that the two 8 ohmer greenbacks are in series, making the total impedance 16 ohms.

solution (1);
if you can put a 16 ohm power resistor (with 100W rating) in parallel with the cab you endup having total impedance of 8 ohms and the whole thing capable of handling 100W.
View attachment 61959

however heeding the aforementioned warnings;




the second solution would be;
put a 8 ohm power resistor (with 150W rating) in parallel with the cab now having total impedance of 5.33 ohms.
View attachment 61960

the second solution will require the head to have 4 ohm speaker/cab out. if the output power of the head is at 100W the speakers will only get a 16.67 watt load (well below its power rating) each while the power resistor will get 66.67 watts of load, meaning there is that tolerance for the head to go over 100W and still not cook the speakers in the process.

BTW the powers resistors would require heat sinks, and hence would require some sort of enclosure to fix them in.

you'll need those heat sinks used for power transistors, as for attachment you can use gud ole nut & bolt with some thermal paste. these are power resistors not those tiny critters

8a00b10f9c5974e59cd95ab32d8eaa88.jpg

HS-420x240.png


Sent from my XT1033 using Tapatalk


oh awesome! so basically just create a dummy load with one of those golden resistors so the amp sends power there and just kinda vanishes, while a useable chunk of power goes to the actual speakers. Makes sense. Funny enough, I recently bought some of those resistors for my car's led system. Are you aware of any DIY guides for this? Very noob and obviously not familiar, step by step guide would be very helpful. Best part is this can be reversed right?
 
Re: 50w Cab and 100w Head

The resistors will work, but is that what you want to do, turn half your amps power into heat.?
If you are after the attenuation...no problem then.
good luck
 
Re: 50w Cab and 100w Head

How can I tell if I blew the greenback? I can't see thru the grill cloth, also tried taking apart the cab but it appears to be glued
 
Back
Top