You can check for voice coil rub by placing your fingertips around the dust cap and gently pressing the cone in and out. You can usually feel if anything is rubbing.
The C12N isn't what you'd spec for new bass amp design, but Ampeg originally built these using Jensen Concert Series speakers without model numbers, so it's unlikely the originals had lower resonant frequencies (there weren't really any good bass speakers back then). Maybe that's why Ampeg used closed cabinets.
Interestingly, I noticed a difference between Joe Piazza's tone stack and the actual Ampeg one. In Ampeg's, the junction of the .001, the .01 and the bass pot wiper has a 270K to ground thats missing on the redrawn one. Some kind of added high pass filter, so maybe Ampeg was correcting something.
Ampeg SB-12 Finished Build - New Problems
Moderators: pompeiisneaks, Colossal
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Ampeg SB-12 Finished Build - New Problems
The 15" CTS driver that is stock in my B15NF is a Bass driver with a thick cone and big roll off from 3K on up!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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dawsonaudio
- Posts: 110
- Joined: Mon Jun 30, 2014 6:43 pm
Re: Ampeg SB-12 Finished Build - New Problems
I did go ahead and return the speaker back to Antique Supply to have them test it out. I will more than likely get a different speaker...probably the Eminence Beta 12A-2. The top end was a little much for me with the Jensen at least for bass recording.
While I was at it, I plugged an old 15 inch Rola/Alnico speaker I have into the amp and that sounded pretty cool. No buzzing or distortion heard. Pretty cool mid tones. I'm now thinking of building a 15 inch cabinet to go along with the 12 I just finished...
While I was at it, I plugged an old 15 inch Rola/Alnico speaker I have into the amp and that sounded pretty cool. No buzzing or distortion heard. Pretty cool mid tones. I'm now thinking of building a 15 inch cabinet to go along with the 12 I just finished...
Peanuts Anyone?
Perhaps there is a shipping peanut piece or other junk that is jammed in the frame of the speaker against the cone. A small inspection mirror may let you see further into the back of the fame where the cone connects to the coil.
If the problem follows the speaker though I don't know how much more I'd mess with it before returning it to the distributor.
silverfox.
If the problem follows the speaker though I don't know how much more I'd mess with it before returning it to the distributor.
silverfox.