450 watt amp into a 300 watt cab - Yes or no?

[xgsjx]

[quote name='FinnDave' timestamp='1499025942' post='3328709']
To be honest, Bill. I've never even heard of the 'myth of under powering', though as you describe it as a myth, I won't bother looking it up! I started playing in the 70s, when the accepted standard was a cab rated at double the potential output of the amp. I have learnt to accept a smaller safely margin than that over the years, but would never plug a cab into an amp capable of delivering more power than the cab could handle.
[/quote]
That could potentially rule out the majority of amps.

[FinnDave]

[quote name='xgsjx' timestamp='1499026243' post='3328711']
That could potentially rule out the majority of amps.
[/quote]

I'd have thought it was the majority of cabs, at least if they're used alone.

[xgsjx]

[quote name='FinnDave' timestamp='1499026388' post='3328713']
I'd have thought it was the majority of cabs, at least if they're used alone.
[/quote]
Now you've got me worried! Think I'll go IEM as my cab is rated at 500w & I've no clue what my amp is (probably 200w as it has 4 KT88's in it).

[Bill Fitzmaurice]

[quote name='FinnDave' timestamp='1499025942' post='3328709']
I started playing in the 70s, when the accepted standard was a cab rated at double the potential output of the amp.
[/quote]In those days real bass drivers were few and far in between, most being generic 'musical instrument' drivers, ie., guitar drivers. They had very short excursion, so you needed lots of them to run clean in the lows. The first rig I had that was capable of running a clean low E with my 50w Fender Bassman was a pair of 4x12 Kustom columns, which had a thermal rating of 150w each.

Much has changed since then, mostly with respect to the excursion capability of drivers. For instance, the 50 watt Jensen P12 was often loaded in 2x12 Bassman cabs. Its excursion (xmax) was 1mm. In real world terms that limited it to perhaps 10 watts in the lows before running out of excursion. The xmax of the average twelve inch bass driver today is 5mm. That translates to over four times the power handling before running out of excursion.

[FinnDave]

I'll be sticking to my Barefaced cabs with amps outputting approx 50% of their theoretical power handling. I haven't been aware of any problems with that approach.

[xgsjx]

The only problem with that approach, is that you're potentially limiting the amps that you can use & may miss out on the one with the killer tone.

[FinnDave]

[quote name='xgsjx' timestamp='1499032964' post='3328769']
The only problem with that approach, is that you're potentially limiting the amps that you can use & may miss out on the one with the killer tone.
[/quote]

Why? Just make sure your cab(s) are up to the job.

[Bill Fitzmaurice]

[quote name='FinnDave' timestamp='1499027158' post='3328724']
I'll be sticking to my Barefaced cabs with amps outputting approx 50% of their theoretical power handling. I haven't been aware of any problems with that approach.
[/quote]This ointment also has a fly in it. Amps are rated at a low THD figure. Pushed to high THD it's the rare amp that won't put out far higher in short bursts, if not long term. I've personally only cooked one driver, ever. It was a 200 watt EVM 15B, and I wasn't even playing through it. I was testing it in a new cab, with a 50 watt amp. I somehow crossed a wire and in less than a heartbeat, so fast that I didn't even hear anything, the voice coil was toast.
In the end it boils down to using your ears, along with common sense. If the speakers complain it's too loud, no matter what the amp rating is. If they sound clean you're OK. It's very unusual for any speaker not to distort well below its thermal power rating. FWIW, Barefaced is one brand that uses very high excursion drivers that probably won't distort well below their thermal limit.

[xgsjx]

[quote name='FinnDave' timestamp='1499033766' post='3328773']
Why? Just make sure your cab(s) are up to the job.
[/quote]
& the OP's Mesa is probably more than up to the job.