Repurpose Guitar Amp with new Speaker

[samtay6]

I hope this isn't the dumbest question ever posed on TB, but here goes.

I've got a SS Peavey guitar amp that I foolishly tried with my P-Bass and I'm not gonna lie it sounds surprisingly good.

I know from internet research that playing bass through guitar amps isn't bad for them per se but at higher volumes it can wreck the speaker.

My question is, would installing a bass speaker (the cabinet is big enough for a 1x15") that matched the impedance of the old speaker be all it takes to make the thing passable at rehearsal volumes?

It's a little 50 watt amp, so I'm not expecting to be able to gig with it and compete with the drummer or guitarist I just want to know if putting in a bass speaker will allow me to crank it louder safer.

Thanks and sorry again if it's a stupid question.

[will33]

Is it an openback cabinet? If so, your answer's no.

[DuraMorte]

If you like the amp, that's great, but I'd highly recommend you get a real bass cab; something like a 4x10 would probably work out quite well.

[samtay6]

Yeah I here you about the cab but this is mostly about my sheer curiosity and dogged thriftiness.

Why won't an open back cab work? I understand its not ideal for bass but neither is the guitar preamp.

my hope is that it can act as a stopgap for my gear until I finish school this year and can have some fee cash for a proper setup

[James Judson]

You are spot on dude. The different in amps is very little (tone stack/voicing). The difference in speakers is it. I use guitar amps all the time, usually into bass cabinets. I say blow that original speaker sky high (before you go out and purchase a replacement). I think you will be surprised at how long it will last.

40 yrs experience playing/building/fixing amps. 40 yrs experience blowing up speakers.

[christw]

The speaker won't have that cushion of air keeping it in check on low frequencies like it does in a closed cab so overexcusrion and speaker damage are just about imminent.

[samtay6]

Originally Posted by christw

The speaker won't have that cushion of air keeping it in check on low frequencies like it does in a closed cab so overexcusrion and speaker damage are just about imminent.

This confuses me. Quite a few vintage bass amplifiers had open backs (bassmans) and there are tons of rear-ported bass cabs.

How can such a small amount of air pressure really keep the magnet from overexcursion? It's designed to be pushed farther than a guitar speaker anyway isn't it?

Then again I'm new to the bass world and I have very limited technical sense.

[christw]

There's a huge difference between a ported cab and an open back cab where the driver moves freely in the air. As well, bass speakers are made to do more lows but in a specific environment. It's a mechanical thing and in an open back cab it's like letting an engine overrev (to destruction) because you haven't got it hooked up to a transmission or anything.

As for the Bassman, I'd bet it was cheaper to make that way or Leo didn't know any better.

Read up here, tons of good information that might challenge some of what you think you know on bass: AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

[Sartori]

Originally Posted by samtay6

This confuses me. Quite a few vintage bass amplifiers had open backs (bassmans) and there are tons of rear-ported bass cabs.

How can such a small amount of air pressure really keep the magnet from overexcursion? It's designed to be pushed farther than a guitar speaker anyway isn't it?

Then again I'm new to the bass world and I have very limited technical sense.

Old bassman cabs are also somewhat infamous for being rather limited in their capacity for bass.