Is this a bad idea or will I blow up my head?

[SRD]

Can I run a 50 watt speaker cab with my 100 watt JCM Slash head on low power?

 

[SmokeyDopey]

You'll risk blowing the speakers, not sure about the head. If he speakers are blown, that changes the impedance of the cab right? So if that happens, you'll have a mis-match, and the PT will be "working extra", risking to fuck up your PT, and that is NOT cheap.

So I would recommend NOT doing that, sorry man

 

[tm0099]

I'm gomna go with 'blow your head'.

If you think you have enough discipline not to crank your Slash head, sure go for it.......but don't say Smokey didn't warn you.

 

[SRD]

well, the purpose of me asking is because it would be for smaller rooms that I wouldn't be able to crank it in the first place, to the room size would be my limiter.

 

[SmokeyDopey]

Well, it is POSSIBLE I guess, but risky. I wouldn't do it personally.

It's recommended not to crank if you have a 50w head into a 50w cab, for example. But having a cab that's HALF the watts? I woulnd't even do it.
But anyway, I'm not a tech, so I can't really say much. Hopefully others that have more knowledge on the subject can pitch in.

 

[tm0099]

A 100watt Tube amp is not really 100 watts, it's more like one hundred and something. So even if you're at half power you're still way over the ability of the speakers, which kinda ties in with what Smokey was saying previously, but i'm also not a tech so maybe wait for a de facto answer from one of them but i would't risk it either.

 

[chuckelator]

That 100w is measured CLEAN. When you overdrive those power tubes, the key word is "over", your pushing it past what it's rated at. So, in essence, your pushing more than 50, well before your amp starts to break up. I'd advise against this.

I have a 50w head going into 2 35w speakers, and even that starts to get farty when I blast it.

 

[GIBSON67]

Low power - should be fine as long as it's really low, don't kid yourself

Slightly cranked - probably need new speakers afterwards

Completely cranked - burning smell, and it's not coming from kitchen

 

[keef1367]

If ya blow ya speakers then your O/T is sure to follow and 100w of valve power can peak at more like 140w! is it worth the risk to either your precious Slash head or your cab?
Ultimately it's up to you as it's your gear but personally I wouldn't risk it as there's always the temptation to turn up a bit or even forget to drop the power on the head
Just my 2p's worth
Good luck

 

[argoncloud]

The low output setting on the 2555SL is 50W because it runs the tubes as triodes, so you'd have 50W into 50W (not 100W into 50W). As others said, the typical output can be about 50% more than the rated value, so more like 75W into 50W. However, speakers are usually rated conservatively, depending on the speaker model you may have some slack.

I never tried doing anything like you say - take this with a grain of salt - but if you keep the volume before noon I think you should be fine. Definitely don't use the high output mode though.

 

[Ken]

I ran a 100 watt head through a 4x10 cabinet rated at 60 watts in the early 80's. Thinking if I "kept the volume down" I would be fine, so I plugged in. Less than 5 minutes later, 2 speakers were gone, the 3rd made farting sounds at best and the 4th was okay. Lesson learned.

Ken

 

[SRD]

ok guys, thanks for all the info

 

[Reckless_Life]

50W is not enough in your case.
It may not get destroyed immediately, but it will. Especially when you play loud, crank the gain, use channel boosters, etc...

If you want to play your 100W tube amp without worries you'll need a 300W speaker configuration.

imo, if your amp is 100W, your speaker wattage should be -at least- twice as much or more.

Marshall sells 4x75W (=300W) cabs with their 50/100W tube heads.
There's a reason why they didn't opt for 50W cabs with their 50W heads