Rectilinear Woofer Varieties: Information Sought

[Njord Noatun]

Those of you that follow the brand may be aware that the Rectilinear III (Lowboy and “Highboy”) were assembled with a variety of woofer varieties. I believe these varieties include:

• Manufacturer: CTS and Jensen (EIA codes 137 and 220, resp.)
• Basket Color: Black, Blue or Bronze
• Magnet: Ferrite or AlNiCo (I think!)
• Magnet: Silver or black colored
• Surrounds: Accordion style woven orange doped cloth or black butyl
• Sticker: With or without Rectilinear sticker
• Manufacturing code: Rear flange or magnet

Suggested timeline for Rectilinear woofers:

1. Square magnet/enclosure (AlNiCo), accordion surround:
2. Round magnet/enclosure (ferrite), accordion surround
3. Round magnet/enclosure (ferrite), butyl surround

I have been able to document five varieties by photos, and one more variety without EIA code. The presumption is that Jensen stamped the codes on the inside basked flange whereas CTS stamped the magnet.

Variety 1:
Black basket, black ferrite magnet, cloth surround, manufacturer Jensen


Variety 2:
Blue basket, silver ferrite magnet, cloth surround, manufacturer Jensen, Rectilinear sticker


Variety 3:
Black basket, black ferrite magnet, cloth surround, manufacturer CTS


Variety 4:
Bronze basket, black or bronze ferrite magnet, cloth surround, manufacturer CTS


Variety 5:
Bronze basket, silver alnico magnet, butyl, unknown manufacturer (Jensen or CTS; likely the latter):



Variety 6:
Black basket, black ferrite magnet, butyl, manufacturer CTS




If you have easy access to a pair of Rectilinear III woofers, please send me a photo (or post them here), showing both the front and rear, and taking extra care to clearly display (use "macro" mode) the manufacturing codes that are stamped either on the rear flange or on the magnet. If you are unable to post photos, a description of your with reference to the above variables would be helpful.

PS! Does anyone know how to read manufacturing dates off of EIC codes? If you study some of the photos above (1, 3, 4 and 5), you can discern the EIA codes: Dating the various woofer varieties would be interesting in order to document Rectilinear’s production. The current presumption is that the orange cloth surround (Jensen and CTS) woofers predates the black butyl surround (CTS - or?) ones.

Thanks!:thmbsp:

 

[Saint Johnny]

Njord,
I just checked the pics I posted a couple of years ago, in a different Rec. III thread.
My pair have bronze baskets, black ferrite magnets, and orange accordion surrounds.
See post #35 in this thread for my pics.

http://www.audiokarma.org/forums/showthread.php?t=124686

 

[Njord Noatun]

My pair have bronze baskets, black ferrite magnets, and orange accordion surrounds.

So that revealed a sixth variety, SJ! The OP has been edited accordingly. If you ever have them out, it would be interesting to find out if they are Jensen (EIA 220) or CTS (EIA 137).

Thanks!:thmbsp:

 

[SiCo Amp]

Hi guys. I just bought a pair of Rectilinear III (my second pair) and they have yet another version of the 12" woofer! Orange accordion surround, silver basket, silver magnet, connections made on a single stand-off (like examples 3,4 & 5, above). There is yet one feature that really makes these look different from the others. The round magnet structure (similar to type 2) is glued to a square 1/4" thick metal plate - the plate and the top "silver" piece sandwich the magnet. The plate is bolted to the basket on 1/8" (approximately) standoffs and the space between the basket and plate is filled with what looks to ne a gasket of either dense foam rubber or neoprene. There are no codes or any type at all on any part of the driver - cone, basket or magnet structure.

My other set of woofers are type 5 - and they are excellent woofers. BTW, it isn't a butyl surround. Those are cloth surrounds that are doped. Butyl may possibly be in the dope mixture, but the foundation of the surround is a rolled cloth.

Thanks!

 

[Freds.Bands]

I hope Rectilinear engineers checked out all these varieties and blessed them. That would be a lot of work, every time the driver mfgrs decided to make a change for their own reasons.

 

[N8Nagel]

I just pulled one out of RIII lowboy S/N 19317. It appears to be the "bronze basket, silver Alnico magnet" type ("type 5" above), although the basket isn't nearly as "bronze" as the pic posted the driver looks otherwise similar. On the magnet is printed

12L300A
137 7318M

on the cone, it is printed 6331234-4

So assuming above info is correct, I would assume that this is a CTS made driver. It does have what appear to be black butyl treated cloth surrounds, although it is not sticky like KLH surrounds.

 

[ra.ra]

R-III's are great speakers, low or high. I have smaller 10" CTS alnico woofers in some Rectilinear XI's, and they are impressive. The stamp on your magnet suggests they were assembled in the 18th week of 1973.

 

[drbiggles]

Yuppers, CTS. I don't know 100% for sure, but I don't believe the lowboys came with Jensen drivers. My early version III's (late 60's) are fitted with Jensen's. When I had my 2 III pairs up and going at the same time, I liked the bass from the later version more.

Biggles