Serial Number registry?

[Harvey Gerst]

Two JBL factory C34 cabinets with th early "cut corner" decals
currently up for auction on ebay:

http://cgi.ebay.com/VINTAGE-JBL-C34-...QQcmdZViewItem


001 systems in two JBL C34 cabinets

from the redder cabinet
130A Woofer serial number: 405169
1217-1290 Horn serial number 404153
N-1200 Crossover serial number: 404170


from the blonder cabinet
175-34 Driver serial number: 40374

The C34 on the right is factory. The C34 on the left looks like a home-made cabinet.

[glen]

The C34 on the right is factory. The C34 on the left looks like a home-made cabinet.

Hi Harvey,

Thanks a lot for for your responses here, and catching this mistake in particular.

I called both cabinets factory because the auction included two pictures of the "JIM LANSING" decal on the front of the cabinet(s). Looking more closely I can see that there is two pictures of the same decal. One appearing "redder" than the other, I assumed they were two different decals. The left speaker's grille cloth didn't look right, but I thought it might have been replaced. But the wood grain around the decal is the same in both pictures, and the picture with the "less red" coloring shows the grill cloth of the right hand speaker, same decal in both.

I've asked the seller if both cabinets have decals.

[Harvey Gerst]

Hi Harvey,

Thanks a lot for for your responses here, and catching this mistake in particular.

I called both cabinets factory because the auction included two pictures of the "JIM LANSING" decal on the front of the cabinet(s). Looking more closely I can see that there is two pictures of the same decal. One appearing "redder" than the other, I assumed they were two different decals. The left speaker's grille cloth didn't look right, but I thought it might have been replaced. But the wood grain around the decal is the same in both pictures, and the picture with the "less red" coloring shows the grill cloth of the right hand speaker, same decal in both.

I've asked the seller if both cabinets have decals.

The stain on the back of the home built job is way too light.The other tipoffs were the wire coloring; factory wiring would have been black/green for the woofer, and black/red for the HF driver. We would never have used all black lamp cord to wire the HF driver.

The grill spreader bar is also at the wrong point in the cabinet, and at a weird angle, indicating a home built job. We never used metal angle iron as grille speader bars. The spreader bar was wood, and looked like this from the side (kinda):

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Pictures 10, 12, and 22 also point out more differences; no T-nuts on the woofer in the home-built job, the 175 outside holes are not even, the N1200 network cutout was hand-cut, not jig-routed, and the wiring holes from the network are spaced wrong and not jig-drilled.

[glen]

The stain on the back of the home built job is way too light.The other tipoffs were the wire coloring; factory wiring would have been black/green for the woofer, and black/red for the HF driver. We would never have used all black lamp cord to wire the HF driver.

The grill spreader bar is also at the wrong point in the cabinet, and at a weird angle, indicating a home built job. We never used metal angle iron as grille speader bars. The spreader bar was wood, and looked like this from the side (kinda):

|\
|. \
|__|

Pictures 10, 12, and 22 also point out more differences; no T-nuts on the woofer in the home-built job, the 175 outside holes are not even, the N1200 network cutout was hand-cut, not jig-routed, and the wiring holes from the network are spaced wrong and not jig-drilled.

Thanks again Harvey!

The detail of your knowledge is great!

I am always surprised by the quality of these homebuilt cabinets, they are often quite well made and match very closely the construction of the factory cabinets even to the internal bracing (I gues from following JBL plans).

It's really nice that you can gives us a handle on the details that would distinguish a well built copy from a JBL original.

Thanks for your invaluable input!

[Harvey Gerst]

Thanks again Harvey!

The detail of your knowledge is great!

Nah, it ain't knowledge; just a lotta years spent looking inside these damn things.

I am always surprised by the quality of these homebuilt cabinets, they are often quite well made and match very closely the construction of the factory cabinets even to the internal bracing (I guess from following JBL plans).

It's really nice that you can gives us a handle on the details that would distinguish a well built copy from a JBL original.

Thanks for your invaluable input!

The plans we sold to customers were quite accurate and would result in a perfect cabinet - if they used the lockmitered joints we used (most often they didn't - a dead giveaway at an exposed back edge). The dark mahogany stain would also be difficult to duplicate, as would the stain on the back panels and inside pieces.

[glen]

Quoting Steve Schell from a different thread:

[quote Steve Schell]I have noticed the odd serial numbers on all of the early (pre late 1950s) JBL products. I asked John Edwards, who ran the office for Jim Lansing from the Venice days onward and typed most of the "cut corner" type labels, about this. He said that the "serial" number actually represented some sort of batch number and possibly dating scheme, though he couldn't remember the details.
The serial numbers seem to make more sense after they began using the oval metal ID plates. Maybe they used a more normal scheme from that point on.[quote]

And I think it was Steve Schell who guessed that the first three numbers represent the year and month of origin (shipping date) in the format:

YMMxx (for 5 digit numbers)
YMMxxx (for 6 digit numbers)

Y being the last digit of the year as in "1" representing 1951
MM being the two digit month as in 06 representing June.

(I haven't yet found an early serial number starting with "2")

This fits well with the range of the early component serial numbers I have been able to find in that the first digit has a range of 1-6 (1951 to 1956) and the second and third numbers range from 01-12 conforming to twelve months.
And on the few original systems that I have found with components assembled at the same time and using these type of serial numbers the system components did have the same first three numbers.

Some support for this date interpretation is also found in serial numbers for the D-130-E, one of the shortest production runs during the "date-code" era. The E designated a field coil driver that was produced in anticipation of a possible alnico shortage because of the Korean war.
See an LH article on this driver here:
http://audioheritage.org/html/readers-photos/d130e.htm

As far as I can tell the D-130E was only ever listed for sale on JBL's August 1951 price list.
The second and third labels pictured below are from D-130Es and the first three numbers "106" would be interpreted as a June, 1951 production date which would seem to corrrelate well with their August 1951 appearance on the price list. The pair of matching serial numbers point to a single production run.

Other identical serial numbers have been found, a couple of N1200s I will post pictures of later, and some pairs of 130Bs removed from cabinets that were originally equipped with a pair of woofers which naturally enough would have been made and shipped at the same time.

But I'm not so sure that the remaining digits following the first three represent a "production batch" because in some cases the "number suffix" doesn't change for units that were shipped over a span of a couple of years:
175: N_30474, 40374, N-41074, N-41174, No50274
(from April, 1953 to Feb, 1955)

1217-1290: 404153, 410153, 502-153
(from April, 1954 to Feb, 1955)

N1200: 404170, 406170, 502170, 603170
(from April, 1954 to March, 1956)

130A & 130B: 405169, 412169, 505169, 601169
(from May, 1954 to Jan, 1956)

But in other cases the numbers increment up faster than might be expected for production runs:
The D130 "suffix numbers" increased from 169 in July, 1954 (407169)
to 511 by Oct, 1955 (510511) an increase of 342
to 713 by Aug, 1956 (608713) an increase of 202

150-4 "suffix numbers" increased from 342 and 347 in Nov, 1953 (311-342 & 311-347)
to 711 in Nov. 1954 (411-711) an increase of 364
to 825 in Feb, 1955 (502-825) an increase of 114

This shows an almost daily incrementing up of the numbers on D130s and 150-4s while other components were not incrementing up at all, or only occasionally

Anyway, here are some pics of these "early labels" that might help get this sorted out.
Some early D130 serial numbers:
D-130 serial number 5010 *
D-130-E serial number 10613
D-130-E serial number 10613
D-130 serial number 10615
D-130 serial number 407169
D-130 serial number 510511
D-130 serial number 608713

*note that the 5010 label does not show JBL name or address, and is probably not part of the "date-code" nubering scheme, there was also an intermediate "cut-corners" label that displayed the "James B. Lansing Sound" name without the address.

[glen]

Actually most N-1000 crossovers that I'm aware of don't have serial numbers on them!

The earliest had only a square "Lansing Signature" logo, not even a model number. Which was in a system that also had only a logo with no serial number.

The next earliest N-1000 I have seen had a label with the "James B.Lansing Sound" tag, but the serial number space was left blank.
This is the first picture shown below.

In my own D-1002 speaker system with serial number 1049 the internal components have similar label that omit the serial number. So it may be that JBL didn't bother to assign serial numbers to components that were installed in one of their speaker units, at least at this time.

The latest N-1000 crossover I've seen bears serial number 499, it's the second picture below. It matches the serial number of the D-175 driver (also shown) that it was paired with in the D-1004 system (serial number 1142) they came out of.
It makes sense that the driver and crossover serial numbers would match at this early period. When these guys were built they were the only hi-frequency driver and crossover that JBL made.