Doesn't the 'C' on a vintage Jensen C15N Speaker frame indicate that it's a ceramic magnet and not an alnico magnet?If you look at the picture, the label says it's an alnico magnet, but stamped on the frame is C15N which indicates it's ceramic.Is the frame stamp correct or is the label transplanted from another speaker? I'm not expert enough to determine which kind of magnet it is by appearance, although I know alnico magnets that are used on speakers are smaller in diameter than a ceramic magnet.The date code suggests it's was made in the 14 week of 1962. The seller said it was pulled form a B-15N. An earliest Ampeg B15 amps would have had an alnico Jensen P15N speaker in them. It had a smaller diameter but taller magnet than the one in your image. They switched to the ceramic C15N not long after the amp was introduced.The Jensen Concert speaker is consistent with what Ampeg was using in the B-15N in 63 perhaps 62 as well. My 63 B-15N has a ceramic Jensen Concert EM1500 which is essentially a C15N.
Jensen would then make subtypes of a general model with a particular cone or voice coil for specific applications. I know they made both a 16 Ohm and 4 Ohm C15L for Leslie. In my opinion, as someone who recones these speakers, the C15L is a decent speaker, probably not as nice as the Utah woofers you find in some Leslie cabinets of the same era.
The one in the image below is what the ceramic one looked like. With the cover over the magnet removed, it looks like a typical ceramic speaker. Very different than the one in your image.I've seen speakers like yours before with the Alnico label on, so this one is not unique. They had the three screws on the back holding on the back plate like old alnico speakers had. That makes me think that it is an alnico speaker rather than a labelling mistake.The Jensen Concert is a great sounding speaker and highly sought after in the Fender community for guitar amps. It also sounds great in my '63 B15N.Jensen Concert ceramic EM1500. Click to expand.The shape of the magnet and magnetic structure can reliably be used to distinguish between alnico and ceramic/ferrite magnets.
Those having a flat, large diameter magnetic structure and magnet (disc-like) are ceramic. The C15N is a good example.Some larger magnetic structures with an alnico magnet have a somewhat similar structure (magnet sandwiched between metal plates), but the magnet is thick rather than wide (cylindrical rather than disc-like).
Those with smaller alnico magnets usually had a thick metal plate bent into a box-like structure.The JBL D and K series drivers employed a cylindrical ring alnico magnet nested in a cast and precision machined magnetic structure. The magnet cannot be seen. These are among the most efficient magnetic structures ever produced, focussing nearly all of the magnetic flux into the gap. There is almost no stray field.A further check is to examine the magnet for chips. The chipped surface of a ceramic/ferrite magnet will have a conchoidal shape and a chalky texture, and will appear non-metallic. A chip in an alnico magnet will be rough (Alnico is coarsely crystalline) and will have a shiny, metallic appearance. Doesn't the 'C' on a vintage Jensen C15N Speaker frame indicate that it's a ceramic magnet and not an alnico magnet?If you look at the picture, the label says it's an alnico magnet, but stamped on the frame is C15N which indicates it's ceramic.Is the frame stamp correct or is the label transplanted from another speaker?
I'm not expert enough to determine which kind of magnet it is by appearance, although I know alnico magnets that are used on speakers are smaller in diameter than a ceramic magnet.The date code suggests it's was made in the 14 week of 1962. The seller said it was pulled form a B-15N. The speaker the OP is asking about was mine. It sold on Ebay today (it will be in the mail tomorrow).A few years back I pieced together a B15 combo using an orphaned '65 head and '62 cab that I had found independent of each other. I did the simple mods that Jess Oliver was suggesting to get more volume out of a vintage B15, including a solid state rectifier and a four ohm speaker.It was great having somewhat of a beater type B15 that I was not afraid to take out for rehearsals and small gigs - but I ended up selling it after a couple of years in favor of a PF500/115Ex2 combo when it was introduced. I regret this now as the PF rig has since moved on - but anyway, this cab is where the C15N in this discussion came from.
I had sold the B15N combo with the 4 ohm speaker installed. I never doubted the C15N's originality to the '62 Ampeg cab, as the speaker's date code and the cabinets serial number reflected the same time period.I have had that speaker hanging on a wall in my storage room for quite some time and I had never noticed the Alnico label until it was posted by someone else on the internet.
Pretty funny. The speaker the OP is asking about was mine. It sold on Ebay today (it will be in the mail tomorrow).A few years back I pieced together a B15 combo using an orphaned '65 head and '62 cab that I had found independent of each other. I did the simple mods that Jess Oliver was suggesting to get more volume out of a vintage B15, including a solid state rectifier and a four ohm speaker.It was great having somewhat of a beater type B15 that I was not afraid to take out for rehearsals and small gigs - but I ended up selling it after a couple of years in favor of a PF500/115Ex2 combo when it was introduced. I regret this now as the PF rig has since moved on - but anyway, this cab is where the C15N in this discussion came from.
I had sold the B15N combo with the 4 ohm speaker installed. I never doubted the C15N's originality to the '62 Ampeg cab, as the speaker's date code and the cabinets serial number reflected the same time period.I have had that speaker hanging on a wall in my storage room for quite some time and I had never noticed the Alnico label until it was posted by someone else on the internet. Pretty funny.
Doesn't the 'C' on a vintage Jensen C15N Speaker frame indicate that it's a ceramic magnet and not an alnico magnet?If you look at the picture, the label says it's an alnico magnet, but stamped on the frame is C15N which indicates it's ceramic.Is the frame stamp correct or is the label transplanted from another speaker? I'm not expert enough to determine which kind of magnet it is by appearance, although I know alnico magnets that are used on speakers are smaller in diameter than a ceramic magnet.The date code suggests it's was made in the 14 week of 1962. The seller said it was pulled form a B-15N. An earliest Ampeg B15 amps would have had an alnico Jensen P15N speaker in them. It had a smaller diameter but taller magnet than the one in your image.
They switched to the ceramic C15N not long after the amp was introduced.The Jensen Concert speaker is consistent with what Ampeg was using in the B-15N in 63 perhaps 62 as well. My 63 B-15N has a ceramic Jensen Concert EM1500 which is essentially a C15N. The one in the image below is what the ceramic one looked like.
With the cover over the magnet removed, it looks like a typical ceramic speaker. Very different than the one in your image.I've seen speakers like yours before with the Alnico label on, so this one is not unique.
They had the three screws on the back holding on the back plate like old alnico speakers had. That makes me think that it is an alnico speaker rather than a labelling mistake.The Jensen Concert is a great sounding speaker and highly sought after in the Fender community for guitar amps.
It also sounds great in my '63 B15N.Jensen Concert ceramic EM1500. Click to expand.The shape of the magnet and magnetic structure can reliably be used to distinguish between alnico and ceramic/ferrite magnets. Those having a flat, large diameter magnetic structure and magnet (disc-like) are ceramic.
The C15N is a good example.Some larger magnetic structures with an alnico magnet have a somewhat similar structure (magnet sandwiched between metal plates), but the magnet is thick rather than wide (cylindrical rather than disc-like). Those with smaller alnico magnets usually had a thick metal plate bent into a box-like structure.The JBL D and K series drivers employed a cylindrical ring alnico magnet nested in a cast and precision machined magnetic structure. The magnet cannot be seen. These are among the most efficient magnetic structures ever produced, focussing nearly all of the magnetic flux into the gap. There is almost no stray field.A further check is to examine the magnet for chips.
The chipped surface of a ceramic/ferrite magnet will have a conchoidal shape and a chalky texture, and will appear non-metallic. A chip in an alnico magnet will be rough (Alnico is coarsely crystalline) and will have a shiny, metallic appearance. Doesn't the 'C' on a vintage Jensen C15N Speaker frame indicate that it's a ceramic magnet and not an alnico magnet?If you look at the picture, the label says it's an alnico magnet, but stamped on the frame is C15N which indicates it's ceramic.Is the frame stamp correct or is the label transplanted from another speaker? I'm not expert enough to determine which kind of magnet it is by appearance, although I know alnico magnets that are used on speakers are smaller in diameter than a ceramic magnet.The date code suggests it's was made in the 14 week of 1962. The seller said it was pulled form a B-15N. The speaker the OP is asking about was mine.
It sold on Ebay today (it will be in the mail tomorrow).A few years back I pieced together a B15 combo using an orphaned '65 head and '62 cab that I had found independent of each other. I did the simple mods that Jess Oliver was suggesting to get more volume out of a vintage B15, including a solid state rectifier and a four ohm speaker.It was great having somewhat of a beater type B15 that I was not afraid to take out for rehearsals and small gigs - but I ended up selling it after a couple of years in favor of a PF500/115Ex2 combo when it was introduced. I regret this now as the PF rig has since moved on - but anyway, this cab is where the C15N in this discussion came from. I had sold the B15N combo with the 4 ohm speaker installed. I never doubted the C15N's originality to the '62 Ampeg cab, as the speaker's date code and the cabinets serial number reflected the same time period.I have had that speaker hanging on a wall in my storage room for quite some time and I had never noticed the Alnico label until it was posted by someone else on the internet. Pretty funny.
The speaker the OP is asking about was mine. It sold on Ebay today (it will be in the mail tomorrow).A few years back I pieced together a B15 combo using an orphaned '65 head and '62 cab that I had found independent of each other. I did the simple mods that Jess Oliver was suggesting to get more volume out of a vintage B15, including a solid state rectifier and a four ohm speaker.It was great having somewhat of a beater type B15 that I was not afraid to take out for rehearsals and small gigs - but I ended up selling it after a couple of years in favor of a PF500/115Ex2 combo when it was introduced. I regret this now as the PF rig has since moved on - but anyway, this cab is where the C15N in this discussion came from. I had sold the B15N combo with the 4 ohm speaker installed. I never doubted the C15N's originality to the '62 Ampeg cab, as the speaker's date code and the cabinets serial number reflected the same time period.I have had that speaker hanging on a wall in my storage room for quite some time and I had never noticed the Alnico label until it was posted by someone else on the internet.