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View Full Version : Score! Obtaining the Unobtanium!



toddalin
05-07-2016, 12:00 PM
Today I scored what I think is a real 2420 diaphragm made of unobtanium!

The piece was removed from a working driver and placed in a 2421 box. The seller really has no idea what it is and had it listed as a "used 2412" transposing the box numbers.

My thought is that someone had a pair of Early LE85/2420s and blew out a diaphragm. When they couldn't get a replacement 2420, they replaced the pair with 2421s, and put the good one away in one of the 2421 boxes.

Who here would just change one of the pair of drivers to a different style without changing the other and not put the original away?

My L/R have the 2420s, but my center channel has a 2421. I've been looking for a 2420 since...

Cost was $65.55 + $12 S/H and I figured the chance of getting a holy grail at that price was worth the risk.

Note the raised pads and factory "shim notes" to get the alignment just so. I've seen that on only a few early 2421s. Now, no body even bothers with that.

https://ssli.ebayimg.com/00/s/MTIwMFgxNjAw/z/u68AAOSwYmZXINBI/$_1.JPG?set_id=880000500F

mech986
05-07-2016, 02:13 PM
Congrats Todd, looks exceptionally clean!

toddalin
05-07-2016, 04:20 PM
The pics of the other side showed no markings/dents/cracks, and just a bit of decomposed foam on the terminals from the internal foams.

I wish it would have happened two weeks ago before I redid the center port and added the tweeter jack/switch. Oh well.

toddalin
05-09-2016, 11:52 AM
Too Funny!

Today I got a note from the seller stating that "The diaphragm is not a 2412, but in fact it is a 2421 and did I still want it?"

I let him know what it really is (2420) and most probably how it came to be (i.e., left over from a replaced pair), and YES I still want it and treat it with care!

When he finds its true value/rarity, he'll probably sh--.

Ed Zeppeli
05-09-2016, 12:13 PM
What is the true value of something like this?

Tks,

Warren

toddalin
05-09-2016, 12:26 PM
Whatever the market will bare.

To the right buyer, could fetch >$500.

Ed Zeppeli
05-09-2016, 12:57 PM
Nice. And these are differentiated from the newer aluminum diaphragms by the tangential (rather than diamond) surrounds; is that correct?


Cheers and congrats on your find!

toddalin
05-09-2016, 01:26 PM
Yes,

The tangential surround has a warmer, more laid back sound than the diamond surrounds.

I had LE175s (with tangential surrounds) and resisted changing them to LE85/2420s for years because the LE175s have a warmer sound and more bottom at the crossover point. Granted, they don't go as high, or have quite the articulation, but I listened to lots of LE85/2420s and preferred the warmer sound of the LE175s.

Then I came across a pair of 2420 drivers in 4320 cabinets that sounded warmer than most, about like the LE175s, but with more highs and articulation. When I opened them up, I found they had the 2420 tangential surrounds, and these replaced the LE175s. But my center channel has a 2421 and it is a bit more "in your face" than the 2420s. Assuming proper operation of the 2420 diaphragm, this one will be replaced and the 2421 put away.

toddalin
05-09-2016, 07:33 PM
Seller contacted me and said that the listing had been mislabled and the diaphragm is "in fact a D16R2421" and if I don't want it, I can cancel the sale. I told him "YES I want it!" and what is really is and how I think it came to be, and treat it carefully. Ships tomorrow.

Hmmm, I need to get an aluminum screwdriver.

More pics.

http://i.ebayimg.com/images/g/6X4AAOSw1DtXINBQ/s-l1600.jpg

Seller had it listed as a 2412... Some of us look a bit closer and can put 2 and 2 together. ;)

http://i.ebayimg.com/images/g/dPIAAOSwM0FXINBn/s-l1600.jpg

martin_wu99
05-10-2016, 04:45 AM
Great found and big bargain,you smart guy:D

Steve Schell
05-11-2016, 08:32 PM
Just a tiny bit of trivia... this diaphragm is the lineal descendant of Jim Lansing's D175 diaphragm of 1947. Examples of the early ones all show a tiny flaw from the two part mold. There is a tiny chip near the apex of one of the triangular tangents, creating a small "caved in" spot. All D175 diaphragms I have seen through at least 1952 or so reveal this flaw, indicating that they were all pressed in Jim Lansing's original handmade tool for this diaphragm. I have several such pressings (never built into complete diaphragms) that were given to me by the Lansing family. Most are a little beat up as they used them for Christmas tree decorations in the 1950s!

toddalin
05-11-2016, 08:54 PM
Are you saying that this diaphragm is from the original tooling circa 1947-1952, or just a decendant of the same design, but using other tooling?

If the former, does this mean its worth more to a collector or in a museum than in my center channel?

Steve Schell
05-12-2016, 05:04 PM
Hi toddalin, no I didn't mean to imply that your diaphragm is an early one. Seeing it just put me in a historical mood.

More trivia: the D175 diaphragm is very similar to the Altec 802 diaphragm that Jim Lansing had done a couple of years earlier. One difference is that their tangential compliances spin in opposite directions.

I found an old thread where some of this stuff was discussed:

http://www.audioheritage.org/vbulletin/showthread.php?29273-Interchangability-of-1-75-quot-diaphragms-Altec-JBL

toddalin
05-12-2016, 06:09 PM
Just a tiny bit of trivia... this diaphragm is the lineal descendant of Jim Lansing's D175 diaphragm of 1947. Examples of the early ones all show a tiny flaw from the two part mold. There is a tiny chip near the apex of one of the triangular tangents, creating a small "caved in" spot. All D175 diaphragms I have seen through at least 1952 or so reveal this flaw, indicating that they were all pressed in Jim Lansing's original handmade tool for this diaphragm. I have several such pressings (never built into complete diaphragms) that were given to me by the Lansing family. Most are a little beat up as they used them for Christmas tree decorations in the 1950s!


Arrived today. Except for some corrosion on the screws and a bit discoloration in the aluminum, appears perfect. Doesn't appear to have the apex dent so I guess I'll use it in my center as planned. Thanks Steve.

toddalin
05-18-2016, 12:37 PM
Why the preference for the dated tangential technology?

I came across an interesting video that compares the JBL titanium/diamond diaphragm with quality aftermarket aluminum tangential and straight surrounds. TO ME even though my computer has a pair of Advent speakers of no where near the quality of these drivers, the attack and thinness of the titanium diaphragm sounds unnatural, cold, brittle, and sterile compared to the tangential and straight offerings. Granted the aluminum may roll off a bit sooner, but that's what the 2405/077 is for.

But you can judge for yourself.


https://youtu.be/WdNLDZQLga8

Earl K
05-18-2016, 01:04 PM
Hey Todd,

I can understand your attraction to these older approaches .

I'd suggest ( before it's too late ) that you try integrating some Altec 288-8K drivers into your system .

Every observation you make about the le85 applies to the Altec 288 ( but in spades ) .

Replacement diaphragms ( at only $100.00 new from GPA ) makes the investment ( mostly ) a no-brainer ( centering the 288 diaphragm can be a challenge ) .

Most new users of any Altec 288 ( coming from the JBL world ) will want to bring along their favourite tweeter ( because the 288 has such a calm, tenor-like, natural-quality to it's voice ).

cheers <> Earl

Steve Schell
05-18-2016, 04:11 PM
To me the diaphragm to beat is still the 1930s/40s Lansing 801. Aluminum (probably 2 mil) spun diaphragm, half roll compliance (no tangents) with round aluminum wire voice coil. Horribly rare now with little opportunity to audition. Probably not quite as extended as these modern jobs, but oh what a natural sound!