Looking for info on early Jensen field coil speakers

[tom1356]

I was wondering if anyone here might know of a late 1930's Jensen speaker catalogue either on line or available for sale or to copy?

There doesn't seem to be alot of info out there on these early Jensen speakers.

Any and all help is appreciated.

[tom1356]

Maybe a couple of pictures will help.
The woofer is the L18.
The tweeter is the XF-101 Model 1.
From the date codes it appears to be from 1938.

[Earl K]

Hi ( Tom ? )

- Nice pics ! I wouldn't mind seeing more of your individual drivers ( out of the enclosure ) . I'd especially like to see a pic of the diaphragm in the compression driver.

- Here are 3 that I have of a similar Jensen/IPC ( 40s' & 50s' era, permanent magnet driver with horn ). From what you've displayed so far / some evolution is quite obvious. These pics were pulled from eBay.

- Believe it or not , 4 years ago, these 2 pieces sold for only $ 103.00 .

- I don't have any printed material ( nor have I seen any online catalogues relating to this stuff ).

- Steve Schell ( look him up using the "Members List" directory ) knows a lot of info on field coil designs , such as what you are displaying .

:)

[Earl K]

Also ;

Contact Kerry Brown at his Vintage Audio Trader Website (http://homepage.mac.com/ikecarumba/Menu4.html) . He has a picture of your cabinet type / plus more of the same sort of driver/horn combo ( like I've shown ).

:)

EDIT :Here's 2 small pics of the 18" PLJ-18 , as shown by Kerry B. ( I hope he won't mind me posting these here ) . Again, this seems to be the permanent magnet version of what you've displayed .

[scott fitlin]

Heres a website with some Jensen catalogs and info.

www.hifilit.com (http://www.hifilit.com)

:)

[tom1356]

Earl,
Thanks for you post. The tweeter you have is obviously very similar to the on in this speaker and almost exactly the one Kerry B. has on his site. I did email him but he didn't have any furter info on it either. I am surprised you were able to buy the tweeter for such a good price. I'm guessing that the rarity of pre war speakers must keep most people's interest down. How does your tweeter sound?
I will try to get in touch with Steve Schell.
I have not removed the drivers from the cabinet yet. I can see through the screen that the woofer is perfect and the tweeter is segmented with a square throat. Iw ill take some pictures when I remove the drivers.
Thanks
Tom

[tom1356]

Heres a website with some Jensen catalogs and info.

www.hifilit.com (http://www.hifilit.com)

:)

Hi Scott,
Thanks for the link. I've checked it out but it doesn't go far enough back.
thanks
Tom

[scott fitlin]

Hi Scott,
Thanks for the link. I've checked it out but it doesn't go far enough back.
thanks
TomI saw that after I posted the link, but its some more info about a few brands as well.

Wish I had more to give.

How do your speakers sound? You listen to them? They interest me. All old stuff interests me!

:)

[tom1356]

How do your speakers sound? You listen to them? They interest me. All old stuff interests me!

:)
I only have the one. This is from the days of mono.
The power supply needs some caps replaced before it can be used. I may have to hollow out and refill the old ones for authenticity sake.

[tom1356]

Hi ( Tom ? )

- Nice pics ! I wouldn't mind seeing more of your individual drivers ( out of the enclosure ) . I'd especially like to see a pic of the diaphragm in the compression driver.

:)

I'm not sure I'm ready to remove the tweeter diaphragm just yet, but here are some pis of the woofer.

[Steve Schell]

Hi Tom,

You have a very rare and historically significant speaker. The components are all from Jensen's top line of components at the time. I was not aware that Jensen built a two way speaker such as this.

The Auditorium Series woofers were used in a variety of applications, including special OEM versions provided to ERPI for the Western Electric theatre sound systems. They routinely sell for huge money on ebay, in part due to the ERPI connection.

The high frequency driver is a really interesting design- a ring radiator, similar in a way to the JBL 075 which it may have inspired. The funny thing is that it is a reentrant design, where the output from the ring diaphragm reverses direction as it is concentrated into a single path which travels through the center of the driver to the exit. That machined rear cap functions as a waveguide on its inner surface, with a beautifully sculpted sharp point in the center. I'm struggling for words to describe the design... imagine a UU shape, where the two arms in the center join into one and continue to travel up. This is the path inside the driver, from the ring diaphragm to the exit. These drivers generally had a large egg-shaped rear cover in the theatre versions; looks like they left it off in the monitor version to save space.

Anyway, this driver in both field coil and permanent magnet versions was used in all the Jensen theatre systems from the late '30s through perhaps 1950 or so. The really odd design and the square exit may be explained by the fact that Western Electric was being contentious about patent infringement in the late 1930s. Companies like Jensen and RCA evidently took extreme measures to avoid building anything similar to the W.E. products.

I have a beat up permanent magnet version of this driver out in my shed. As soon as I get a new digital camera I'll photograph it and post the pictures here. I'd much rather do this than see you disassemble an ultra rare working field coil example.

What does the high frequency horn look like? I'd love to see a picture of it out of the cabinet. The dividing network, with its inverted bathtub chassis, looks typical of the Jensen theatre gear of the period.

The Lansing Iconic, which was introduced in the fall of 1937, is generally credited with being the first two way studio monitor. Your speaker appears to have been hot on its heels if it was built in 1938. You will probably be amazed at its sound quality when you fire it up- it may be the best speaker you've ever heard! Just to mention my usual caution to those new to field coils... don't apply any audio signal before making absolutely sure the field coils are receiving their DC current. In a field coil driver there is practically no flux when the field is not energized, and the voice coil can be burned out easily as all of the power applied is dissipated in the coil.

[tom1356]

Steve,
Thank you for your reply and the wonderful information. I was worried I was never going to find out anything about it.
Any idea why it would be painted "Jensen blue" by the factory? This seems a strange choice unless it might have been for a public display or show???
I bought it from the original owner. He was well into his nineties and suffering from Alzhimers disease. His son said that he (the son) had last used the speaker thirty years ago when it just stopped working. Recently the teenage grandson took the back off it to salvage some magnets when his brother noticed the tubes in the power supply and suggested he find out if it was worth something to someone.
It came dangerously close to being canibalized after surviving seventy years intact.
As far as I can see the two bad 24-40 uf electrolytics are the only problem with the whole speaker.
I will take some pictures of the tweeter horn and post them tommorow. It is made of sheet metal and not cast as the others appear to be.
I will not be disassembling the drivers as they both check out fine on the DVM.
Here are some pics of the crossover and power supply.

[andywin]

http://cgi.ebay.com/JENSEN-RED-CONCERT-SERIES-F15LL-15-FIELD-COIL-SPEAKER_W0QQitemZ5854832177QQcategoryZ50597QQrdZ1Q QcmdZViewItem

Not exactly the same but very similar

[tom1356]

http://cgi.ebay.com/JENSEN-RED-CONCERT-SERIES-F15LL-15-FIELD-COIL-SPEAKER_W0QQitemZ5854832177QQcategoryZ50597QQrdZ1Q QcmdZViewItem

Not exactly the same but very similar
Andywin,
I did catch that. It looks like a really nice driver.
Thanks
Tom

[tom1356]

Steve,
Here are some pictures of the tweeter horn. If you would like any other photos, ie:a specific angle or detail, just let me know.
Would you know of a supplier for the powersupply caps?
I'm amazed at the condition of the underside of the dividing network.
Thanks
Tom

[dnostereo]

What does the high frequency horn look like? I'd love to see a picture of it out of the cabinet. .I have a horn from the same (xf-101) driver. Here are some pics.708877088870889