Jensen Alnico 5 Speaker

[Chris Bauer]

Stumbled onto a fifteen inch Jensen Alnico 5 speaker . Besides what seems to be a serial number, it’s marked P15N C5786 2.

Because I’m an electronics moron, I have no idea what I have here. I’d love to know how it sounds with pedal steel but have no idea what its power handling is or its impedance and I don’t want to blow it or an amp transformer up.

Who’s got some knowledge or even educated guesses?

[Mike Auman]

From the Jensen website:

One of the first speakers ever used in a guitar amplifier was a Jensen® Alnico speaker - the P15N. The first Fender® Bassman® and Bandmaster® amplifiers were loaded with Jensen® P15N Alnico speakers.

All Jensen® Alnico speaker model numbers begin with the letter P, and are therefore often referred to as the P series. Next in the model number is the diameter of the speaker. Alnicos are available in the following diameters: 8”, 10”, 12” and 15”. Following the size is a letter which traditionally is used to designate the speaker power rating. For example, R (25 watts), Q (40 watts) and N (50 watts).

So yours is 50 watts. It should be marked either 8 ohms or 16 ohms on the outer rim. Failing that, you can measure the resistance between the speaker terminals with an ohmmeter, an 8 ohm speaker will measure roughly 6-7 ohms, and a 16 ohm speaker roughly 12-14 ohms. Specs can be found at https://www.jensentone.com/vintage-alnico/p15n-no-bell

[Dave Grafe]

Okay for guitar but somewhat inferior for PSG.

[Noah Miller]

The later ones are rated for 50W. Earlier ones are rated for quite a bit less. Is this an Italian or US-made speaker? There should be a date code starting with "220" on the rim.

[Chris Bauer]

On another forum it was identified as having been made in 1955.

[Noah Miller]

I believe the P15N entered the 1950s rated at 20W. I have old documentation showing that, but I don't have a firm date for it. By the 1960s I believe it was up to 50W, and I think there was also an intermediate rating of 30W or 35W at some point. But I admit I can't be terribly helpful without knowing when these changes occurred - and honestly, I'm not clear on what structural changes were made to change the ratings. Age has probably lowered its power handling capacity by a little as well.

To be on the safe side, I'd probably not run more than a 20W amp through it, maybe 30W if you're not going to crank it up.

[Dave Grafe]

The later ones are rated for 50W. Earlier ones are rated for quite a bit less. Is this an Italian or US-made speaker? There should be a date code starting with "220" on the rim.

As explained above the N series was always rated at 50 watts RMS, other power ratings had their own designations.

"Following the size is a letter which traditionally is used to designate the speaker power rating. For example, R (25 watts), Q (40 watts) and N (50 watts)"

[Noah Miller]

The later ones are rated for 50W. Earlier ones are rated for quite a bit less. Is this an Italian or US-made speaker? There should be a date code starting with "220" on the rim.

As explained above the N series was always rated at 50 watts RMS,

As explained below, that is not correct.

[Dave Grafe]

https://www.jensentone.com/vintage-alnico

Same design, same materials, just a different power rating paradigm. Note that the listed "Music Power" rating is considerably more than the current industry-standard RMS value. In any case it's the same speaker with a cap over the magnet.

[Noah Miller]

It's made by a different company in a different factory in a different country from what OP has. It's not the same design, and it's not the same speaker, even if they do happen to have the same power rating (which has not been established).

[Dave Grafe]

According to SICA the "Vintage" series duplicates the original design and materials precisely and uses the original tooling to form the cones. Their testing of these recreated classics yielded the listed power handling figures. That's all I've got to go on.


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