The "75" family of JBL compression drivers/tweeters

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10-06-2009, 05:39 PM
mhardy6647

The "75" family of JBL compression drivers/tweeters

OK, so I guess there was an 075, 175, 275, and 375. I know about the 075 of course, and I've read a little here and there on the 175 and 375... but there just doesn't seem to be much chatter on the 275.

This is basically what I've got (which, no surprise, comes from this site!)

http://www.lansingheritage.org/image...-275/page2.jpg

As I mentioned here a while back, I found a pair of 275 drivers with H5040 horns at the "Yankee Swap" pile at our town dump (on the 4th of July). I am still really curious to hear any modern opinion of these, e.g., as they relate to their cousins (or brothers).

Thanks!

http://img.photobucket.com/albums/v2...s/P1030534.jpg
10-07-2009, 05:20 AM
Beowulf57

Here's another reference to the 275: http://www.lansingheritage.org/html/...5-metregon.htm

It looks to me like an early version of the LE85/2420.
10-07-2009, 05:56 AM
mhardy6647

Quote:

Originally Posted by Beowulf57

Here's another reference to the 275: http://www.lansingheritage.org/html/...5-metregon.htm

It looks to me like an early version of the LE85/2420.

That's a helpful quantum of info, thanks. I was thinking about asking what might be a "more modern" version of this driver.

I am really a babe in the woods with JBL hardware; thus the newbie-flavored posts.

The driver and horn (in quick functional tests with a fairly high 1st order XO) sounded pretty good. I assume they're "wicked efficent" drivers -- as we tend to say in New England.

EDIT: oh, jeez... the N600 XO went was used in the Metregon too... These were found with N600s (though not connected to them). I hope someone in my little town didn't gut a Metregon...
10-07-2009, 07:48 AM
Beowulf57

Quote:

Originally Posted by mhardy6647

That's a helpful quantum of info, thanks. I was thinking about asking what might be a "more modern" version of this driver.

I am really a babe in the woods with JBL hardware; thus the newbie-flavored posts.

The driver and horn (in quick functional tests with a fairly high 1st order XO) sounded pretty good. I assume they're "wicked efficent" drivers -- as we tend to say in New England.

EDIT: oh, jeez... the N600 XO went was used in the Metregon too... These were found with N600s (though not connected to them). I hope someone in my little town didn't gut a Metregon...

You're welcome. Yes, very sensitive compression drivers: http://www.lansingheritage.org/image...omp/page10.jpg

The world is full of unknowing people.
10-07-2009, 08:09 AM
Earl K

History of the 275 ?

- It would appear that the 275 was first offered in the 1958 Dealers' Price List. .
- The 275 is absent from the previous years 1957 Dealers' Price List.
- It also appears that ( as a separate line item ) it was gone by the 1964 catalogue.

- I'm guessing it's development was driven by Bart Locanthi, based on designs he implemented with the developmet of the 375 a few years earlier .
- I don't think it's a coincidence that the 275 is shaped liked a baby 375 ( ie ; shape matters ) . ( ie; Someone decided to rework James Lansings' original 175 driver )

- There's some good anectdotal evidence on LHF (ie; photos from subwoof, all initiated by a question from JimD ) showing that the alnico magnet slug of the 275 ( le85 / 2420 ) is the same size as what is found within the 175 ( 1.2 lbs I think ) .
- The increase in the 275s' gap strength ( leading to greater HF extension & a greater sensitivety ) was the result of implimenting a more efficient magnetic return circuit when compared to the 175s' more cylindrical shape ( ie; the cast pot holding the magnetic slug ) .

- The 275 & the le85 both appear in the 1962 Dealers' Price List .

- This is a period ( according to the printed info on this site ) when JBL was creating a second pricing column and evolving the concept of selling ( differentiating the sale of their ) "loudspeaker components" .

- FWIW, the 175 during this period was also marketed as the "le75" . This marketing separation was maintained to at least this 1964 catalogue reference .
- Carefully read what JBL marketing has to say about the difference between their "maximum efficiency" line of transducers and their linear-efficiency ( LE ) line . Read it here .

- When it comes to an actual mechanical or design difference between the compression drivers' marketed throughout the two lines, I'm very skeptical that it's nothing more that marketing hubris .

- The 275/le85 driver was eventually marketed as the 2420 when JBL decided it needed another differentiation in their product lines / this time finally ( successfully ) creating the "PROFFESSIONAL LINE" .

>< cheers :)
10-07-2009, 08:13 AM
4313B

Quote:

Originally Posted by Earl K

- Carefully read what JBL marketing has to say about the difference between their "maximum efficiency" line of transducers and their linear-efficiency ( LE ) line .

Yeah, increased moving mass to extend low frequency bandwidth at the expense of efficiency. Woo Hoo! :rotfl:

Hey! At least they went with heavier moving mass instead of gutting the motor structure much to the chagrin of the rest of the industry. :p
10-07-2009, 08:30 AM
jcrobso

I hope you realize what find you have by now.

The 275 will bolt to any JBL 3 bolt horns! I have a set of LE175 drivers that are over 40 years old and still sound great!
The H5040 horn was designed for the Metregon and as such it is somewhat difficult to put into a speaker box, but it could be done.
Now you need to a pair of 15" JBL woofers and start on your systems.:)
10-07-2009, 08:37 AM
Earl K

Quote:

Originally Posted by 4313b

Quote:

Originally Posted by Earl K

- Carefully read what JBL marketing has to say about the difference between their "maximum efficiency" line of transducers and their linear-efficiency ( LE ) line .

Yeah, increased moving mass to extend low frequency bandwidth at the expense of efficiency. Woo Hoo! :rotfl:

Hey! At least they went with heavier moving mass instead of gutting the motor structure much to the chagrin of the rest of the industry. :p
__________________

-Just so the OP doesn't get confused by this ( since the topic was/is about compression drivers ) / Giskards' comment about added cone weight ( for increased MMS & therefore greater LF bandwidth ) relates only to the woofers in the LE line ( not the HF diaphragms found in the compression drivers ) .

>< cheers :)
10-08-2009, 06:18 PM
mhardy6647

Quote:

Originally Posted by Earl K

- It would appear that the 275 was first offered in the 1958 Dealers' Price List. .
- The 275 is absent from the previous years 1957 Dealers' Price List.
- It also appears that ( as a separate line item ) it was gone by the 1964 catalogue...

- The 275/le85 driver was eventually marketed as the 2420 when JBL decided it needed another differentiation in their product lines / this time finally ( successfully ) creating the "PROFFESSIONAL LINE" .

>< cheers :)

This is great; just the kind of stuff I sought. Thanks!