Bass cab wattage

No, the 300 cab won't be louder, the amp is the limiting factor.

You can use a higher rated cab, but there's the risk of underpowering the cab.

Better plan for a new amp too.

 

The general rule of thumb is that, if anything, you want an amp that is more powerful than your cabs - the reason being that if you run your amp flat out, you generate a clipped signal that is far more damaging than a louder amp producing an unclipped signal at the same volume.

The only reason for buying a cab with a much higher rating is with a view to potential upgrades in future - for example, I run my Ashdown Mag 250 head (250W) into a mini 1x15 cab (rated 300W). My next upgrade (if I need one) would probably be a mini 4x8 cab (rated 600W!) but that would then let me get a more powerful amp as the next step. I'm very scrupulous about not clipping the sound - the input level is set so that the needle nudges the bottom of the red area on the 'speedometer' gauge only when I sent a really strong slap or pop, and if I found myself having to turn up the master volume to more than about 3/4, I'd start considering a new amp in the near future.

You may find that different cabs give you different volume levels - that's going to be partly down to design and partly down to resistance (Ohms). However, if you want to get maximum volume from your head, two cabs is probably a better way to go than a single, massively over-rated one.

Wulf

 

This has been dicussed a lot, and a search on clipping or underpowering will probably yield some useful stuff.

To be correct, there are no such risks because in the truest sense, there's no such thing as underpowering a cab*. You will never have a problem running a 150 W amp into a 250 W cab *provided that 150 W is enough power for you to play your gig properly* and you don't have to push the amp too hard. If 150 W is not enough and you have to push the amp too hard, then yes, you could damage the cab. But see--and here is where the underpowering-the-cab myth gets needlessly confusing--you would be even *more* likely to damage the cab in that situation if it were a 150 or 100 W cab (which would supposedly not be underpowered).

My suggestion is this: get an amp that's easily big enough to do your job with plenty of power to spare. Then get a cab that's capable of handling the level of power you normally use. The cab's rating can range from half of your amp's rated max power, or less, to twice your amp's rated power, or more. Once you easily have enough amp power for your gig, you gain no additional benefit from having your cab rated at less than your amp. At that point, the cab rating doesn't matter much (within reason).

You *can* use a bigger amp into a smaller cab. Often this is a good idea if you can afford it. But there's nothing at all wrong with using a smaller amp into a bigger cab *if you have enough power for your playing situation*. For instance, if you could easily do your gig with 200 W (let's say it's a coffeehouse or small jazz gig), but you have 600 W available and run it into an 800 W cab, you don't have a problem. Certainly you don't have *more* of a problem, in any sense, than if you were running that 600 W amp into a 300 W cab. If you have enough power for your gig, you're never underpowered, by definition, ragardless of the cab's rating.

 

If you want to use your current head, you just need to find a very efficient speaker system.
Unfortunately, this type is usually fairly large or lacks extended low end.

Other TBers can possibly point you in the right direction (I used to have a homemade cab with two JBL D-140F's that would kick with a 50W tube amp).

Alternatively, if the AH150 has a preamp output, you could also buy a power amp to use instead of the amp in your head.