Speaker question for Ampeg B25 2x15

godofthunder · April 10, 2013, 11:03:47 AM

Well I blew the speakers in my B25 2x15

I have no idea whats in there, could be original CTS or Altecs but I'm guessing neither. If they are Altecs I might have them re-coned. I was considering using Eminence Alpha 15A 200 Watt 15" 8 Ohms Speaker wired in series. Thinks these will be able to handle the head? I think B25 are around 55w.

godofthunder · April 10, 2013, 11:19:26 AM

There is also a 300w version of the Alpha 15 should I go for that ?

drbassman · April 10, 2013, 11:40:54 AM

Bummer! Those darn TBs are treacherous!

godofthunder · April 10, 2013, 11:44:58 AM

I knew they were on borrowed time when I bought the cab, I didn't really drive it that hard but I'm sure the Big Muff Pi did them in.

dadagoboi · April 10, 2013, 01:09:14 PM

IIRC the cab is wired in series, 16 ohm. More than likely only one speaker is blown.

Head is rated at 55 watts. The original speakers were probably 50 watts each. The optional Altec 421As were only 100 w. A speaker rated at 300 watts is most likely not going to sound like either if that's important.

godofthunder · April 10, 2013, 01:27:56 PM

Thanks Carlo. It does sound like only the top one is blown but I have not really checked things out yet.

Psycho Bass Guy · April 10, 2013, 09:58:42 PM

Quote from: godofthunder on April 10, 2013, 01:27:56 PM
It does sound like only the top one is blown but I have not really checked things out yet.

With the speakers in series, if one is blown, neither will work. If the other speaker is working, your cab was wired incorrectly to start with and the cab was 4 ohms if they were both 8 ohm drivers (and a fine example of how "too low" of a load is not as harmful as too high with output transfromer coupled amps- ie tube type). A CTS speaker will have a manufacturer code of "137". Altec is "391." Here's a reference for the EIA codes:

http://www.triodeel.com/eiacode.htm#speakers

8 ohm CTS 15's aren't that hard to find, are not typically expensive, and will sound much better in that cab than a modern high-powered, high-excursion driver.

gearHed289 · April 11, 2013, 08:44:29 AM

I had a really old (chrome metal tag) Ampeg 2x15 for a long time. I'm pretty sure it was a V-6B. Not as wide as a B25 cab. It was loaded with JBL D140 speakers.

Psycho Bass Guy · April 11, 2013, 03:59:31 PM

Quote from: gearHed289 on April 11, 2013, 08:44:29 AM
I had a really old (chrome metal tag) Ampeg 2x15 for a long time. I'm pretty sure it was a V-6B. Not as wide as a B25 cab. It was loaded with JBL D140 speakers.

How'd it sound?

stiles72 · April 11, 2013, 04:11:15 PM

I really like the sound of the old CTS drivers with my vintage Ampegs. To me they just sound "right". For the price, I'd go with an Eminence driver as a replacement.

Aussie Mark · April 11, 2013, 05:15:47 PM

The ceramic coil Jensens go nicely in vintage Ampegs too. I have a C12N in my SB-12, and sounds beautiful when driven hard

FrankieTbird · April 11, 2013, 05:22:53 PM

Whatever you end up doing, try to get a very efficient speaker. That low power amp really needs it. The old 421A's have a sensitivity rating of over 100dB if I remember right. Most newer hi-power speakers are not nearly as efficient.

gearHed289 · April 12, 2013, 08:52:14 AM

Quote from: Psycho Bass Guy on April 11, 2013, 03:59:31 PM
How'd it sound?

Sounded good when it wasn't rattling. There were these curved pieces of sheet metal making up the slot port between the two speakers that were prone to rattling. Those JBLs are the only speakers I've ever blown. Eventually switched to EVM-15L. Love those.