Did the C38 use aluminum grille frames?

[Wardsweb]

Here is a pic of my C38's that use aluminum grille frames. Is this original?

[Harvey Gerst]

Yup, it's an original. When we moved from Fletcher Drive to Casitas, we started to make the cabinets one-piece construction and the new design had a slot in the front edge of the cabinet for this new window screen grille. As a matter of fact, that looks like one I did. They made me the tester for using the new grill assembly system. Iguess they figured if I could do it, anybody could do it.

[John Y.]

Harvey,

My Hartsfield, made after the move to Casitas, has aluminum frames for the grilles similar to what you describe. The frames slid down into slots (just like the wooden ones did on the drawings). At the time, I thought this quite clever. I replaced the original grille cloth with pure white when I had the cabinet refinished to piano black and it certainly was easy to do.

John Y.

[John Y.]

Originally posted by Wardsweb
Here is a pic of my C38's that use aluminum grille frames. Is this original?

Wardsweb and Harvey,

In this configuration of the C38, did the back panel come off to mount the speakers from the inside? I don't know that they ever made a front loader of these cabinets. My C-37, built from JBL plans in 1957, has a rear panel that removed to access not only the speakers, but the entire front baffle for replacement of the grille cloth.

John Y.

[Harvey Gerst]

After we moved from Fletcher Drive to Casitas Ave., we switched over to the solid construction, using front loading components and sealed backs. That's when they put the aluminum grill frame slot in the bottom of the cabinets.

[Wardsweb]

John if you're ever in San Antonio let me know and you are welcome to come see and hear these.

The backs on mine do come off.

[GordonW]

Harvey,

C36 question... what year, approximately, did JBL stop using a wood "pedestal" base on the C36, and change over to the aluminum legs? I've got a pair of C36 cabinets here, that have the wood bases...

Regards,
Gordon.

[Harvey Gerst]

I'm pretty sure it was around 1954 or 55.

[John Y.]

Wardsweb,

I haven't been to San Antonio for several years. If I do get over that way, would love to hear and see your C38's. Give me a call if you are in Houston near the Johnson Space Center and I'll demo my Hartsfield and new home theater equip.

An interesting thing caught my eye in your picture. Apparently JBL was using panels to mirror their 075 (or 175?) for stereo with a panel in the other corner having a circular cutout to serve as the reflex port. Very clever!

John Y.

[Harvey Gerst]

Originally posted by John Y.
Wardsweb,
An interesting thing caught my eye in your picture. Apparently JBL was using panels to mirror their 075 (or 175?) for stereo with a panel in the other corner having a circular cutout to serve as the reflex port. Very clever!

John Y.

I found that "reflex Port" to be the most curious part of the picture.

I remember the C36 and C38 as having a rectangular port near the bottom of the baffle board, and two cutouts for proper positioning of the tweeters. The second circular opening at the top was usually covered over with a blank piece of wood.

The cutouts were big enough to also handle a 175DLH horn, and the second opening could be used for an 075 for a 3-way system.

[GordonW]

Originally posted by Harvey Gerst
I found that "reflex Port" to be the most curious part of the picture.

I remember the C36 and C38 as having a rectangular port near the bottom of the baffle board, and two cutouts for proper positioning of the tweeters. The second circular opening at the top was usually covered over with a blank piece of wood.

The cutouts were big enough to also handle a 175DLH horn, and the second opening could be used for an 075 for a 3-way system.

I've seen both ways.

My first pair of C36s I asked you about a couple years ago, Harvey... they were slightly different ages. One of them had a rectangular port near the bottom, the other one had a round vent (no pipe, just a round cutout in the plate) in an adapter plate, like the picture above. Did the calculations on port Fb, they came out the same, though... functionally, the same thing, on paper. Couldn't tell any difference by listening to them, either.

My current pair of C36 cabinets (the ones with the wood pedestals, apparently from 1955 or older) have ports in adapter plates like above, only with a port tube mounted in the adapter plate... a tuning of like, 39-40 Hz or so, as opposed to the 50-something Hz tuning that seemed to be common for the D130 or 130A. I think these were probably originally loaded with D123s... in the C36 cabinet, the D123 simulates (on computer box-tuning programs) better than any other period JBL 12" in this box, with that tuning...

Regards,
Gordon.