Speaker and output wattage question on 2 EL84 Rocket

[johndandry]

I built a loud 2xEL84 rocket. 385v on the plates due to the trannies I'm using. It sounds great! Right now I have a single 12" old Vox Silver bulldog with a TT hemp recone I play it through, also sounds wonderful but I think I need to get a little bit higher power rated speaker for this amp. I also kinda wanna reduce the highs a but. I was thinking a 65watt Scumback M75. But its an open back cabinet, so that may be an issue with a greenback type speaker. Any suggestions? Maybe a Gold Alnico, V30 or G12H but I'm afraid those may have too much high end extension. Kinda like the idea of a bit more mid/woody speaker. Also, I am using Seimen E84L right now with the bias at about 13watts dissipation. Can that be calculated to output wattage? Is the total output 13+13 for two tubes?

[ampgeek]

Congrats! Sounds like you have a winner.
What is the rating of the current speaker?
Only 1 tube conducts at a time in a push-pull output section so it isn't the combination of the tubes. It is a bit more than a single tube if it is biased in Class A/B but not much more.

If you assume 18 watts and have a speaker rated at ~ 2X (35W is close enough) that you will be way, way safe.

Good luck,
Dave O.

[johndandry]

I'm guessing its no more than 20watt tops..and that's probably pushing it!

[martin manning]

Power output goes almost like plate voltage squared (with the same load), since the current and voltage go up together. So if e.g. you can get 18W out of two EL84's at 300V, then at 385V it'll be something like 30W, unless you hold the screen voltage down.

[lions den]

Not sure what speaker to recommend but I can tell you that Jim at Scumback has some great clips up that show what each speaker can do.

I was looking for a single speaker to use with an express and the M75 65 watter seemed to fit what I was looking for. But I also wasn't sure if the M75 with the large dust cap would be the ticket. After listening to the sound clips I decided on the M75 but also got the M75-LHDC for a D style amp since its modeled after the G12-65 that works with that amp.

I have been very pleased with both speakers, they sound great and fit exactly what I was looking for. Checkout his site and the various models offered.


You can always drop Jim an email as well to ask for any suggestions.
Good luck.
Sean

[johndandry]

Anyone have the M75 in a open back? I can believe that this thing is close to 30w, its loud. SS recto. I did e-mail Scumback and told them what I am using and going for and they suggested the M75 65watt.