Actual output wattage, and not blowing speakers

[Onioner]

I've got a pp two 6v6 amp here, Blackface style, for about 25W that I'd like to play through a pair of Weber 15W AlNiCo speakers (Blue Dog / Silver Bell). So, yes, I realize that the amp is overpowered for the cab. If I understand things correctly, that 25W is what the amp puts out before it gets dirty (from the player perspective, not the THD perspective). So, from what I see, I should be able to use this amp with this cab as long as I don't push it much beyond that point. Yes, I realize it's a risk, as if I accidentally crank it, I will most likely blow a speaker or two. Still, from what I understand (see a recurring phrase here?), as long as I'm careful, I should be ok. First, I'm wondering how many folks think I'm a fool for even trying this. Second, a couple questions come up.

Wattage output is mostly a function of the power tubes, yeah? So, if I goose the input signal, and consequentially distort those preamp tubes a bit, I'm not really seeing much more wattage output than if I didn't goose it, yeah?

Similarly, if I plug straight in, with, say, averagish output pickups (8.8K or so), and have the guitar volume straight up, I can get an idea of where that 25W output is on the amp's volume knob by waiting until I get audible distortion. At that point I'm probably just over that 25W point.

How quickly does output wattage ramp up from there? I understand that most of the time cranked output will be a bit under twice rated wattage. In this case, with a fairly clean design, probably significantly less, for maybe, by my uneducated guess, around 40W, wide open.

Again, if I goose that input signal, but leave the volume at that point just before I got breakup with a straight signal, does the output wattage change significantly?

Fwiw, I'm both trying to understand this for this specific use, as well as just general knowledge. Any light shed is appreciated. I'm hoping I can get some nice, singing hairy cleans that will push these speakers into compression without blowing them. Just gotta make sure I don't cross that line...

[SeanF]

I can't generalize about distorted vs. clean power, there's just too much going on to say absolutely, but if I had that combination, I wouldn't hesitate to use it like you're describing; it should be fine.

I wouldn't recommend diming a RAT at full volume and slamming power chords for an hour, either, but I'd probably do it anyway.

[wall_of_sleep]

I would bounce the question off Weber. Experienced members here should also be able to let you know where to draw the line, but you're throwing 30 watts of speakers at a 25 watt amp.

Output wattage is really a function of the circuit. We look at power tube dissipation because it's easily measurable and is a good approximation, but the preamp signal and OT have a hand as well.

25 watts seems overly generous for 6v6 pp, so my opinion is go for it.

[RussB]

The old "rule of thumb" is to have twice the speaker power handling capacity than your amp is rated...so in other words, 50 watts worth of speakers minimum for your 25 watt amp.


Weber speakers are not as durable as Celestions regarding their ability to handle power. The Weber's can & will blow


The rest of your complicated math scenarios is just you trying to justify an under-powered speaker arrangement

[Onioner]

Originally Posted by RussB

The old "rule of thumb" is to have twice the speaker power handling capacity than your amp is rated...so in other words, 50 watts worth of speakers minimum for your 25 watt amp.

Yeah, but that's a lousy rule of thumb, aiming to "play it safe." I have no qualsm whatsoever about using this cab w/ the 18Wer I got it for.

Weber speakers are not as durable as Celestions regarding their ability to handle power. The Weber's can & will blow

True enough. Celestion ratings are roughly double most other companies. Weber's still a fairly conservative rating. They can handle a bit more than their rating, or so I've been led to believe, having never blown one. Weber describes them as 'robust,' but their handling is still fairly close to what they're rated (unlike the Celestion, which basically uses a different system than everyone else...).

The rest of your complicated math scenarios is just you trying to justify an under-powered speaker arrangement

More trying to understand. I kinda get what happens with a straight up scenario. I don't understand what happens when you tinker. But, yes, I am precisely trying to justify an under-powered speaker arrangement. I am trying to do so because it sounds glorious when I get it just right. Just a matter of finding how far I can go. Don't want to find out the hard way. Them AlNiCo webers aint cheap...

[Ruraltom]

Found this thread through a search and was hoping I could get someone else to chime in on this...

I was thinking of putting a either a 20 and 30 watt Blue pup in a cab or a 20W WGS Veteran and a 30W Blue pup in a cab for an Orange AD30... too 'dangerous'?

[Onioner]

Originally Posted by Ruraltom

Found this thread through a search and was hoping I could get someone else to chime in on this...

I was thinking of putting a either a 20 and 30 watt Blue pup in a cab or a 20W WGS Veteran and a 30W Blue pup in a cab for an Orange AD30... too 'dangerous'?

Naw, that sounds like regular "kinda pushing it" levels. That should be just fine. Maybe don't dime everything for hours on end, but I can't imagine that's the plan anyways with an AD30.

[Ruraltom]

Originally Posted by Onioner

Naw, that sounds like regular "kinda pushing it" levels. That should be just fine. Maybe don't dime everything for hours on end, but I can't imagine that's the plan anyways with an AD30.

Right on, thanks! Did the setup you posited on the original post work out for you?

[Onioner]

Originally Posted by Ruraltom

Right on, thanks! Did the setup you posited on the original post work out for you?

Workin' so far. Honestly, I bet I could push it a good bit more than I am, but I don't feel the need to, and with four hundred and something dollars worth of speakers in that cab, I'm gonna go ahead and run with what's workin', and not keep askin' for more. Sounds pretty lovely too. I just don't let it get past 'hairy' cleans.

Incidentally, I regularly use a similar ratio as you're suggesting with other cabs. A couple 18W amsp gets 30W cabs, a 35W amp gets a 60W cab, a 25W amp gets a 40W cab. My modified rule of thumb is double the wattage and round down. There's just always the question of how far down you can round, which is not a pleasant number to exactly discern for sure...

[Ruraltom]

Cool, I'll give that set-up a try this weekend. I just don't want to find anything out the hard way if I don't have to!