I recently found an Ampeg B25b cab on craigslist for sale. After talking with the seller I found out it was one of the ones without the impedance switch from 4 to 16 ohms and that it was only 16 ohms. I'm assuming that it has two 8 ohm speakers in it and can be rewired for 4 ohms. Am I assuming correctly? and is this a fairly easy and cheap thing for an amp tech to do? Also I'd be using this with an Ampeg V4 head. Anyone else ever use this setup?
Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
Ampeg B25b cab question...
- Thread starter justin_beerd
- Start date
I have one that I rewired to 4 ohms and it isn't hard to do but can take a bit of time as you have to remove the back. I'm not sure if the stock speakers would last long driven by a V4 - that's about 2x the power of a B25 head.
Thanks. I figured it was relatively easy. Crap I also meant to ask that about the speakers. I was hoping that wouldn't be the case but totally makes sense.
If they are 8 ohm speakers, you don't need to take it to an amp tech. It's just a simple matter of placing the speaker wires in the right places. There are many threads on here and in general on the net that tell you what to do. It's a simple job. As far as the V4B head and the B25B cab, let your ears guide you. With stock speakers, you'll obviously have more power than they were intended for, but that doesn't mean you can't do it and it work for you. Depends on your usage and loudness requirement. If you're very lucky and the cab has the optional Altec Lansing 421A speakers, so much the better. The B25B cab with the Altecs was listed as a cab match for use with the SVT 300 watt tube head of the time period in the Ampeg brochure. 
The stock square magnet CTS drivers were rated for 85wrms so the total is 170 - but I like to have at least 2x the rating of the amp when it has tubes (or mosfets). FlipTops.Net recommends the Eminence Beta 15A as the "best" replacement speaker and those are rated at 300wrms - maybe you'd be best to "upgrade" the drivers and sell the "vintage" originals?
