Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by 6Tones, Jun 5, 2019.
Is a 2x12 cab with one 50 watt one 35 watt speaker safe enough for a 50 watt head?
Assuming both speakers are of the same nominal impedance, the cab power rating is twice that of the lower rated speaker, so 70 watts in this case.
In theory, if the amp really is capable of putting out 50 clean watts, then overdriven you can expect in excess of 70. Hence the 35 watt speaker would be at risk.
In practice, as long as you don’t push things too far then it may be fine. The problem being that the rig will tend to sound better the harder you push it, and it may get too tempting to turn it up.
The rule of thumb I've always heard is that you want twice the power-handling in your speakers as you have in output.
Depends on the speakers too. Celestions can take the beans, Jensens not so much. I wouldn't sweat 50w into 70w worth of Celestions.
I wouldn't. As stated. For me general rule is 2x amps rated clean output. But I like even more than that. 3x is even better. 4x? 8x??
I use 4 x 12 x 25w Pulsonic G12H (100w ) with a 38w Metro GMP45 head. Or 2 x 1 x 12 90w Celestion Creams. 180w. Or 2 x 1 x 12 Hemp Coned JBL E120s. 300w. All for a 38w head. I hate speaker funny business, and like to know my amp will blow, before the speakers give out.
Original Hiwatt DR103 with 8x 75w Fanes is 300w per cabinet, 600 total watts for a 100w amp. Marshalls of the day only had 240w capacity max..120w each cabinet for their 2 x 4 x 12 cabinets/amps
I'm running a 30 watt head into a pair of cabinets. 1 cab has a pair of Celestion Greenbacks at 25 watts each, while the other has a single Celestion Blue at 15 watts. Total of 65 watts between the cabs.
Currently only playing at home. Sometimes turn it up, but never reaching gig or club volumes.
Is the Blue at any significant risk?
It depends on the characteristics of the amp, its intended load impedance, and the impedances of your cabs.
Amp is Bad Cat Cub III 30r (4 x EL84). Both cabs are 8 ohm and the head has 4/8/16 ohms selector. Currently set at 4 ohms, per John at BC.
Playing clean up through overdriven classic rock. No metal, heavy distortion or fuzz. Turn it up to garage jam volume when I have the house to myself, which isn't often enough.
The amp looks to be tube rectified and cathode biased (assume that's what is actually meant by 'class A'). Both of those act to limit how much greater the overdriven power output is over the rated clean output, so the full overdriven power may be 40 watts or less.
Modern Blues are reputed to be good for 20 watts, same as the late 60s silver alnicos.
It will be taking half the amp's power output, ie up to 20 watts.
So your Blue may well have a reasonable working life, especially if you use a long speaker cable to it
Thanks for the research. Blue is only a couple months old, so definitely a newer model. I'll replace with a higher power 50w gold or 90w cream, if I decide to gig. Was using a 15 watt BC until a couple weeks ago, so wasn't concerned about it.