View Full Version : The first real JBL 130 loudspeaker?
06-13-2003, 12:57 PM
I am doing a little research out of curiosity to answer some questions I always had… and found your most excellent site, dudes.
Well, what I have had all these years is one JIM LANSING Signature MODEL (L in the circle) 130A 15" loudspeaker. S/N 12807. The name and serial number seem to date it around 1950. It has a paper--not Duralumin dust cap. The cone is in very good condition and well aged by now. I have never reconed it. Don't know if it was reconed before I got it. Back side of cone has stamps 180 20 (twice). Wait a minute--there is another stamp 180 200 crossed out in pencil. Factory part number change? Or offbrand recone? And even a 6 written in pencil. The QC stamp on frame appears to be 1B1 with a faint 2 below it in the circle. It has a cork baffle gasket. Unfortunately, condition is not mint. Some of the frame gray finish has pitting. The magnet cover dust may clean up with a toothbrush. I will be getting photos soon if you would like to see. I have found it quite good for vintage tube to 80's transistor amps for hifi and think it would be fine for PA if not abused.
Am I on the right track? Is it the original cone? Is it the same design and specs of a 50's D130? What are the specs? What rigs was it used in? Is it a really good guitar or bass driver? What guitar amp cab would be best? I might use it for an extension cab unit if the right match came along. Is it more of collector interest vs. a player?
Is it for sale? Isn't everything? Any information would be greatly appreciated. Then I could factually represent it on eBay or your marketplace or ???
Thanx a bunch, Martin W.
If you care to know… I originally bought it at a flea market for a ridiculously low price. I was an audio tech in the 80's who knew of the D130 series but surmised this "L" model 130A was a bargain consumer series or some cheap OEM special. We didn't do speaker work at Western Radio Lab in Mountain View CA. Mostly Macintosh & B&O warranties, all Century Stereo service and walkins. I started as the Dual turntable specialist because their changer mechanisms drove the other techs nuts. (Does anybody know Henry Pollack? He was my boss/mentor/expert on magnetic tape recording.) It was in a homemade corner cabinet with a University mid horn/xover and Jensen high horn/xover as yet unidentified. That may be another question to post later.
Needless to say, I bought it anyway. This unit has been used in my home as a 3-way center channel stereo speaker for the last, oh, twenty something years. I have gotten newer sound equipment--which will not need such a monster. So I no longer have a use for it. No, I will not sell my 1984 Altec Lansing 312 stereo speakers relegated to the game room. They make my Pioneer SX-650 sound great. Best setup was in another house suspended from the gabled ceiling angled down to ear level. They rode out the Loma Prieta earthquake no problema on 4 600 lb. nylon straps clipped to the baffles with my custom engineering. (The cabin survived with only 1" shift of the post foundation.) They would fall off the garden pot stands now but should survive except for grill damage. Just not suited to digital recordings through a Marantz Dolby 5.1 AV amp. Am happy with the Boston 965s for that. They work well for my corner placement environment and don't mind the odd geometry and R/A room characteristics. Some people hate the pointed screwy feet--but they are perfect for leveling one on a rock hearth and other on carpet.
06-13-2003, 02:53 PM
I don't know the history the likes of Giskard, Earl K or Mr Widget are sure to, but here's the T-S parameters, and the link to their source:
06-13-2003, 08:34 PM
Thanx for answering the specs question, boputnam. One down and (too) many to go. And, of course, these answers raise new questions. This is fun to go down memory lane and back to school! My e/m theory never was that strong, and is rustier than ever, but let me venture into it anyway.
Cones are the same surface area. My 130A's magnet is a little weaker (Flux). This allows a lower res freq (Fs) from looser magnetic coupling maybe. Lower DC resistance and higher inductance... on the same diameter and length coil? Hmmmm. Coils must be wound much differently. Assuming the same throat gap and bobbin/coil clearances, I suppose Jim coulda put more turns of larger cross sectional area wire on. Would need a thinner bobbin (flimsy) or longer wrap to do that.
I'll take any extra efficiency I can get. Higher EFF tends to eliminate the longer-wrap coil theory as I think about it again... unless the throat is deeper. Too many factors involved to pick one efficiency contribution. No RMS power spec is OK. The least important one of the bunch until you put a system together.
WAY MORE DISPLACEMENT (Xmax) At first I thought "could the supension be that much softer?... because it's just the same CONE paper formed and not like foam or anything. I never trusted foamies when they first came out. Suspicions confirmed ten years later when friends' ARs started disintegrating! ... Aaaaaargh! My 312's finally cracked out their suspensions; boo hooooooo. Lasted longer than most, tho.) They just don't make 'em like they used to. Now I gotta start another thread. Anyway;
Duh! The displacement has to go into the magnet, too. So the 130A has much MUCH MORE THROAT DEPTH to allow for that... golf clap applause... LONGER WIRE WRAP on the coil. This is starting to make sense. That could account for the lower Qts I think (I could never understand "Q" until he appeared on Star Trek). I'll stick with this story for the moment.
Sounds like a D130 cone would be out of the question if the coil is that much unique. What are the chances Harmann (Kardboard, we used to call them back then) would still supply 130A cones? None to Huh? is what I would expect. I would buy a NOS 130A cone as a backup if somebody knows somebody who knows somebody.
The 130A as a bass guitar amp spikker seems like a marriage between Linda L. and J. Holmes, eh? Should have better transient attack vs. D130 as well. It will need to be ported much differently for any application. I'll guess a much thinner and longer reflex port path for bass guitar cab, like a slit extending back 3/4 of a typical cab depth? It's tempting to try closed back and front-- like my kickass Marshall 1912 guitar lead cab w/ a single 12" Celestion Sidewinder (150W!) ar, Ar, AR! That has awesome drive in the 200-500 Hz range. A JIM LANSING SIGNATURE on overdrive in the 60-200 Hz range would be truly unique. Vintage tone, Schmintage tone--I've got active pickups in my bass guitar. My low E string (42 Hz) is always too strong, anyway. Why fool around? Tune the cab to roar where the tones are most needed I say. Every musical instrument has a resonant hump somewhere. Even the earth is not flat, I've been told.
I KNOW YOU EXPERTS ARE OUT THERE! I have a little more knowledge and am even more dangerous now! Stop me (with design facts) before I go off the deep end! The 130A manufacturing curiosity started out strictly from a history buff. It now seems important for my cabinet design parameters if I can't go by the D130 book. BTW- Now you can see I'm not some pawn shop reseller who slaps a $$$ label on everything old and dusty. I find the ultimate app for good old stuff or sell to someone who does.
Thank you in advance,
06-13-2003, 10:44 PM
I was editing online, Giskard, and you may have not seen the latest rev. Sorry, I will compose offline from now on. Thanx for chiming in. I am sure you are correct on the net magnet characteristics. What seems most different in the specs and would affect transient response is that much bigger peak displacement. A longer throat depth and a coil with more turns of bigger wire x-sect and consequently tighter spacing is what I was picturing as of the last thread rev. Your 1/3-more 'turns in the gap' calculation confirms that mental image for me.
Why did Jim revise the 130A-- producing less transient response and displacement in the D130? Was the 130A too difficult to manufacture? I'm surmising 130A coils were wound with less spacing and easier to goof. Or was the 130A less reliable? It seems such a coil would either dissipate more heat and need more ventilation--hence the rear vent port. Was the 130A first to to have rear venting? Did the theatres ask for mellowness? Was the crowd not ready to be attacked? Which did Leo Fender prefer?
More questions answered and five more posed. I had better stop geometrically expanding the questions for now.
This is wonderful, people. Where have you been all my life?
06-13-2003, 11:00 PM
Sorry to interrupt but I had read a long time ago that the original D130 had a more narrow VC gap which gave better control and efficiency. This was changed on subsequent models because of the difficulty in maintaining the quality control necessary. Is this true?? Which is the original I thought it was the D130 w/o letter??
06-13-2003, 11:18 PM
Don't be sorry, Roland, this is a public discussion. The info I have now confirms the original driver is the 130A I have. It was apparently replaced a few years later by the D130. I suspect certain buyers like Fender continued ordering the 130A while they could but I have no production dates to confirm. All I have learned to date confirms that yes, the 130A had less gap which improves efficiency among other things.
Small VC gaps are harder to manufacture due to angular cone alignment during assembly plus coil winding tolerances= scrrrrrape. Reject. Smaller gap means less air flow to ventilate as well. This may have been a problem for the larger customer base of theatres and the like--purchasing a driver or two and trying to fill a large space with the "Jim Lansing Signature Sound" as advertised. I can imagine wonderful and loud sound until thermal expansion results in crackle, snap, pop! Warranty return. When you are just starting to sell, you can't always tell customers "I told you to buy more speakers and amps for that size room!"
06-14-2003, 12:39 AM
I was under the impression that the D130 was the woofer that put James Lansing Signature in business. If you haven't already checked this out, take a look:
Does your 130A have a cast magnet return pot or a welded pot? The welded ones are the earliest examples. They are rectangular in cross section, the cast ones have the familiar rounded corners.
06-14-2003, 01:18 AM
Back in the mid 70,s when we were first getting into big sound at my buisiness, we used to purchase our audio from AST in Manhattan. And we always had JBL 18,s and Altec 15,s. I used to ask Ritchie who owned AST if JBL 15,s would be better. he used to tell me that the JBL 15,s had a very narrow gap and because of the carbon dust, and the sustained high levels for 14 to 16 hours a day, that the JBL,s wouldnt hold up as well as the Altecs in my place!
So, its entirely possible that the gaps have been changed throughout the years! They always modify existing products and came up with new and improved products! the best thing that I can think of, is reliability. Im not sure, but reliability would seem to me to be the key issue.
Conversely, when you look at the basket of a JBL 2226 thats manufactured now, the gap doesnt seem very narrow at all!
And the original 130 is a 20 watt driver. So I could see JBL improving their design over the years to increase power handling and reliability issues.
06-14-2003, 09:58 AM
It's worth looking at JBLs' early TS parameters (http://www.lansingheritage.org/images/jbl/reference/tech1-3a/page08.jpg) to get a sense of what happened to the original late 1940s' 130A speaker. There was eventually a 130H ferrite magnet version by 1979. The TS parameters and catalogs pretty much tell the story that JBL evolved/merged the original 130a into the Pro version 2220a/h speaker.
If you want to try to date your speaker into any particular era , you might try to do it by its' net weight and overall depth. It is a bit of a pain but I've done some of the work below.
If you look at the 1971 Pro Catalogue (http://www.lansingheritage.org/images/jbl/catalogs/1971-pro/page07.jpg) you can compare the weights of the original era 2220a/130a and that of the early era 2205 to those same speakers as found at the 1974 Pro Catalog (http://www.lansingheritage.org/images/jbl/catalogs/1974-pro/page13.jpg) . You'll see JBL adding weight to the magnetic assemblies in the early 70s along with adding depth to a bunch of their woofers . Compare to the 130a as found in the 1976 Home catalog (http://www.lansingheritage.org/images/jbl/catalogs/1974-home/page15.jpg) to get a sense of where the alnico 130a (& D130) of the mid 70s was headed . Here you'll see the 130a was now a deeper speaker with greater magnetic assembly weight than the D130 ( or the 136a ) . Don't focus on the shipping weight . Everything seemed to have shipped out with a weight of 19 lbs. Net weights were 17 lbs or less .
There is a suggestion from these catalog specs that somewhere in the mid seventies JBL increased the top-plate depth ( gap depth ) from their standard 7.1 mm to 9 mm ( .28" to .35" ) as they evolved the 2220a/130a speakers. I believe the 130a specs evolved right along with the 2220 ( maybe with an implementation lag ) as JBL decided to make the 130a the home component version of its Pro Divisions' 2220. By the time one compares specs in the 1979 component catalog (http://www.lansingheritage.org/images/jbl/catalogs/1979-comp/page09.jpg) to a 2220H cut sheet ( found at 2220H (http://www.jblpro.com/pub/obsolete/2220hj.pdf) ) one sees that JBL has morphed the old 130a into the 2220H/130H type speaker . The D130H mentioned in that ( late fall ) 1979 component catalog would seem to be a moniker-tortured, home-component version of the E130 ( debuting in the summer of 1979 ) .
regards <. Earl K
06-14-2003, 11:25 AM
Many thanx to all for the info. Current conclusion: this 130A IS the HOME VERSION sibling to the D130. The "Jim Lansing" label definitely dates it to the early period before Altec put a stop to that trademark infringement. So late 40's would be about right fer shure. The Univerity TC-30 mid driver w/ 4409 6x7-1/2 horn and Jensen high driver (a small unimportant mystery) are reasonable mates for it.
Net weight is 15 +/- 0.5 lb. as measured on my digital bath scale. It is the rounded back (die-cast?) magnet and a frame similar to the 1974 catalog photo except for not having the impregnated suspension. It has a pretty gold ring between the magnet and frame.
Power rating remains unknown. Something like 60-100W program or 20-40W RMS by reasonable standards now. You can only compare wattage ratings within one manufacturer using consistent test specs for the period anyway.
This makes it totally unsuitable for my wild ideas about forcing it to blast bass guitar tones. Oh well... The neighbors will sleep better if they only knew. Look for an ebay item something to the tune of 'vintage 15" JBL University Jensen speaker set NR' in the next week or so. Unless I take up an offer in the meantime. I don't see much demand for this series on your marketplace. So
that's a rap for this topic... unless a Lansing collector needs one?
Thank you all again,
06-14-2003, 11:35 AM
Here's what I can add about history. The original 130A was introduced in 1948 at about the same time as the D130 and was called the D130A. This designation remained until 1950 when it was change to simply 130A. It used the identical magnet structure as the D130, and as far as I know, the substitution of a paper dustcap for a duraluminum one may have been the only difference. The magnet was a welded up pipe casing that was visually distinctive with its flat back as shown below:
In 1953, JBL introduced one piece sand castings for their magnetic pots that had a rounded shape as shown here:
After this point, my knowledge of the subtle design changes of the 130A becomes hazy. I do remember Greg Timbers stating, that in the 70's, there were numerous evolutionary changes to the bass drivers including gap depth, magnet size and gap width. Most were driven by the need for increased power handling. However, I have never been able to track down the specifics.
06-14-2003, 12:47 PM
Here are some links that may be of interest:
Early JBL history
06-14-2003, 04:20 PM
The 130 speaker, in all its variants, is a real favorite of mine. Endless hours can be spent searching the catalogs on this site to extract some history. To simplify, I think the earliest version (called D130 but with a paper dome) was used as a woofer in the "Iconic" monitor - a really seminal product.
From the period of your speaker, the 130A and 130B were woofers, made with copper voice coils and some excursion. I don't know but I think they were overhung coils. The larger copper coil is probably the reason for the extra 10 grams cone mass. These were usually crossed over at 1200Hz to the "potato masher" round horn lens. I believe the woofer application predates the fullrange version. It's not a home version of the D130; the D130 is more of a home version of the 130A I think.
The D130 (D for dome) used the aluminum dome for a dust cap, to provide more high frequencies so the speaker could be used full range. It had a shorter aluminum voice coil for better highs, and I believe the VC length was exactly equal to the magnetic gap height. I've always supposed the dome was derived from the 375 (2440) horn driver. They had more treble than the woofer version, but it was not all that great, it was often paired with the 075 bullet tweeter at a nominal 2500Hz crossover. (I have one of these crossovers, and the actual crossover frequency seems to be closer to 1600Hz.)
The 130A was specified at 16 ohms, and the 130B at 32 ohms - but the specs were eventually revised to 8 and 16 ohms respectively. The 130A eventually became the 2220. There are a large number of minor variations, including at least four different magnetic assemblies. I have a "pair" that were re-coned at different times, and the cone masses are 60 and 80 grams, so I know there were different cones! I have heard of several different voice coil lengths and magnetic gap dimensions, too. Sure wish there was a reliable source of information on such details.
06-14-2003, 09:38 PM
Again I was told by an old timer (50s-60s) guitar player that the best was the D130 without a letter because of the narrower gap. Once they went to a letter the gap had been widened and the speaker had lost it's magic and great response. Perhaps the only exception was the D130F model whose F just designated it was made for Fender Amp use? This is not hard data but he knew his stuff and was of that time. I actually have some D130 and letter variants around perhaps a micrometer will answer the dilema?
06-14-2003, 10:46 PM
Should have read his postings before above comments.
Basically from Harvey and Harry who worked for JBL during that time and were responsible for design and letter codes.
The D130 series all had similar cupper VC/frames etc but the A model was 8 ohms, the B model was 16 ohms. The F model made for Fender Amps had a wider VC gap at the top plate for less binding and only slightly reduced VC gauss and sensitivity but was more reliable and power tolerant. So the 130F is the only one that widened the VC gap to reliably play in the 100 Watt Fender Dual Showman. Some guitar players felt that change made the speaker lose some of it's "magic" although measured changes are minimal.
Thanks Giskard, we finally get the story right.
06-15-2003, 01:27 AM
I think I've got it now... The 130A rev1 came out at the same time as the D130 rev 1 with a welded magnet casing. Both models got the same sand cast magnet circa 1953. Altec's lawyers were as yet not griping about use of the Lansing name. Take a look at the Fender Bassman and Bandmaster photos and specs to see why rockers needed more than what was available;
I will take the designer Harvey Gerst's version over the Dick Dale story. No date for that but it's not my model anyway. Harvey widened the throat gap SPECIFICALLY for roadie mounting warpage allowance on all the F-suffix models. Other concurrent changes were mainly general updates.
The "goop" coated suspension originally for outdoor use became standard in other models. Thicker cone paper for stability under sound attack condition was applied to many high power designs. (Musicians are dangerous animals, you know. Roadies are just not to be trusted with anything delicate.)
The F-suffix models mixed & matched components for different music instrument apps and sizes. The aluminum coil D130F guitar model was probably the first to be introduced. 15" was really bigger than guitarists needed but it would stand the rockin' heat.
The D140F electric bass guitar model kept the 130A longer copper VC. All making it high power capacity, but a little less efficient, slower transient attack and less susceptible to mounting warpage.
My 130A sand cast magnet and frame is the same as the rev2 period D130. Its coil is rated 16 ohm on mine but is really 8 ohm if measured above its resonant frequency-- in its midband as later done. A more efficient, more responsive and more "musical" driver than all of the above as long as you don't torque or crank it toooo hard. My 130A rev2 would still work as is in a vintage Bassman or as a 2-way PA/home driver using a 1200-2400 Hz xover or 3-way using a 600-1200 Hz xover. The University N2A xover is wired in 700 Hz 16 ohm fashion.
It's reconable with a D kit, which would turn it into a D130 w/ Alum VC and Alum dust cap (adding some hertzes) for full range bass guitar or 2/3-way PA (or home) use.
Or a 2220 kit-equivalent to retain the sweeter copper voice coil sound and efficiency. The longer copper coil adds some moving mass. Paper weights may vary.
Now we know....
BTW-- I pulled the low driver out of that "Altec Lansing" 312. The flimsiest Harmann Kardboard 18 ga. frame they made (I hope) and a wimpy (10 oz. ?) ceramic magnet with "Super high-temperature pure copper voice coils". 22 ga. wire connecting "a multiple element dividing network to maintain precise frequency distribution" consisting of a hot-melt glued coil and a cap or two. I'd go for a Radio Shackish UPgrade, but even they don't sell a lightweight 12" woof woof any more. Tough to match efficient bargain drivers to suit these days. Can a shop glue a new surround on these?
06-17-2003, 11:32 AM
Hi group, interesting discussion. I'll add what I can.
Jim Lansing left Altec Lansing in late 1945 or early 1946. He intended to make a complete break from loudspeaker manufacturing, which he had done continuously since 1925. He bought an avocado ranch in San Marcos, CA and moved his family there. He had been interested in farming and breeding different types of avocados for some time.
Within weeks changes began to occur in the barn, as metal machining equipment began to arrive. Soon Jim had set up a full machine shop and was back into speaker manufacturing. It appears that he simply couldn't help himself, that he was driven to make speakers as an artist is driven to paint canvases.
His first product was the D-101 15" general purpose speaker. It looked much like the Altec 515 woofer that he had helped design and put into production only months before. It had a 3" voice coil and an aluminum dust dome to extend high frequency response.
Soon, while still building speakers in San Marcos, he introduced the D130 and D130A. These featured a shallow overall depth, shallow curved cone, 4" edgewound voice coils in a 12kilogauss flux field. He designed these for maximum sensitivity. The D130 had an aluminum dust dome and aluminum voice coil to extend highs. It could be used fullrange, or as a woofer in a two way system with crossover. The D130A used a copper voice coil and paper dustcap, and was intended for woofer duty.
Jim moved his "Lansing Sound Inc." operation to the Marquardt facility in Venice in 1947. He continued to produce the D-101, D130 and D130A (among others) in that location, but eventually stopped making the D-101. Next was a move along with Marquardt to Van Nuys in 1948. When Marquardt was sold in early 1949, the company was moved to Fletcher Drive in Los Angeles, where it remained for several years. So, these early JBL drivers can be dated pretty closely by the location mentioned on the decals. The earliest drivers will say "San Marcos, California" on their decals.
Jim Lansing stated his goals for his new company to Hal Cox sometime in the late 1940s, something to the effect that he had brought high quality sound to the movie theatre, now he wanted to bring it to people in the home." His new products did seem to be primarily intended for home use.
I have wondered about the similarity of Jim Lansing's products to the postwar Western Electric speakers such as the 728B and 756A. They do have much in common with the thin profiles, shallow ciurved cones, edgewound aluminum 4" voice coils. Whether there was some inspiration flowing in one direction or the other, or simply independent development along similar paths is hard to say at this point.
06-18-2003, 05:39 AM
I read about the D101. Was not considering that as the first "real" JBL since it was an Altec design copy. My Jim Lansing Signature 130A was made in LA and it is from 1953 on, based on the cast magnet, to whatever. The serial numbers were sequential across all models, I was told, and would need a known year of manufacture with a close number to pin it down.
The Altec lawyers would have clamped down within a few years--one would suppose. Had assumed mid to late 50's would be the last Lansing labels. I saw a photo of an original owner's D130, dated 1965, which did not have the Lansing name. There was a reference I read somewhere that mentioned the label vendor's name. I don't have that much curiosity or need to establish the minimum age that way.
She is a well preserved example--and have the photos to show off now.
Made a nice avatar, too.
Back, back, back.
The business end.
Hairline cracks on the surround if you use a magnifier.
The wrong stamp crossed out.
Got the right stamp now--do it twice to be sure.
Happy traaaaails to you, untiiiil we meet agaaaain,
06-22-2003, 07:20 AM
I see this discussion thread about your speaker is now being used as a reference tool to help sell your speaker on eBay at 130a for sale (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3031863518&category=3276) . I don't have a problem with that. Now a warning; In all fairness to potential buyers, there's a 50 - 50 chance this particular woofer will not be able to be reconed, should it ever need that service .
This is because your vintage of speaker is likely to have a narrower gap than the present day recone kits will fit into. Factory rebuilding of the magnetic assembly would be required to rectify this condition .
Here's a jpg of this JBL published "narrow gap" alert info .
I'd steer your sale towards audiophiles who are less likely to blowup the speaker than "Spinal-Tap" inspired musicians .
regards <> Earl K
06-22-2003, 09:06 AM
Thanks Earl! That's the old page I was looking for! Here's the new one... notice the differences?
06-22-2003, 10:05 AM
You're welcome !
Yes the differences,, well, the old page is more comprehensive. The new page with it's more streamlined info omits to mention that the older D131, D208, D216, D280, D123, & most importantly D130 (units) are all placed under suspicion of maybe having a narrow gapped top plate ( if the before mentioned conditions are present ) .
What I find the most intriguing to all this , is that as late as when JBL introduced the first 2205 and 2220 models, they still weren't committed to opening up those gaps for higher power handling. The time period of late 60's, early 70's shows them struggling to come to grips with the "new" market realities ( ie, letting the M.I. market drive some of the design ). Altec was slower to catch on to this mantra ( "Power to the People", etc. etc. etc. ), IME, and look what happened . As such, a real pivotal time period for both companies .
regards <> Earl K
06-22-2003, 11:51 AM
Ok sleuths, I've got one for you.
Since widening the gap will lower the magnetic force, to maintain the same performance as earlier designs, larger magnets would be required. Is this why the pro variants went to the deeper return pot casting with the chamfered taper?
If you look at that well known ad for the L-300 with the cut away showing how the L-300 is virtually identical to the 4333 you will see a fine example of truth in advertising. In that photo as with real life production units, the woofers are different. I have never found an explanation as to why JBL would use the older round style casting on the 136A and the newer JBL Pro casting on the 2231A.
If this casting change was to accommodate a larger magnet to allow for a wider gap and hence greater power handling, then I would have expected the paper that Earl posted would have called attention to it.... any ideas?
06-22-2003, 03:15 PM
Hi Mr Widget
Yes, more magnet weight was needed to maintain flux level in wider gaps. A study of all the 1970s' catalogs show JBL ( simplistically ) started the decade with 11 lb magnetic assemblies ( for the typical pro woofer ) and ended the decade with 13 lb assemblies .
It seems that with the 12 lb assemblies of the mid-seventies ( like the 136a and the K120/130/140 ) the older / shallower pot could still be used and energize the wider gap.
A 136a can be reconed/ fitted with a newer 2235H kit. Those 12 lb "K" assemblies were housed in the shallow pot and were rated as 12000 gauss. And we know they had the larger gap for power handling. The 2231 had a 13lb assembly that required the deeper pot structure to house it. It too was rated at 12000 gauss in a similar gap width.
I can't reconcile the discrepancy between the 12 & 13 lb assemblies being housed in different pot casings and yet still having identical gauss levels. I will speculate that the larger assembly was built to provide more reserve power - like using bigger capacitors in a power supply to stiffen its' "torque" curve .
So ,,, the shallower / older pot style can't be used as a narrow gap clue ..
That's what I get from the publications.
regards <> Earl K
06-23-2003, 12:53 PM
Hi guys. Remember me? the threadstarter. You have gone on ahead to reverse engineer magnetic design evolution of the early models by now without me, I see. You will need "hard evidence" to support your hypotheses. So why don't you break down a few examples to take a look? I can even suggest ways you should be able to put them back together for further electromagnetic/mechanical experimentation. This is a general guide...
0. remag to full strength; measure all the mechanical, electrical and free air acoustic parameters of the specimen for reference-- especially the maximum rear displacement & +/- unipolar transient step response while still intact.I want mechanical readings at many points across the cone +surround (foil targets and laser displacement meter plot here) and microphonic test results for this dynamic test
1. peel off the spider OD & remove the magnet assembly from the basket; measure gap gauss strength reading for reference
2. we must go where no (sane) person has gone before... we could:
a. cut it in half with a power saw-- but that would be too much work and was done before by 1975 marketing types, anyway, so...
b. I don't know how the magnet & pole piece are held together; probably press fitted because few good high-temp glues were made then; try heating outer & cooling inner pieces for removal; failing that...
c. score the section line on the return pot back flat side and break it open with a BIG cold chisel and sledgehammer while resting on an anvil-- repeat for top plate if necessary; leave magnet and pole piece intact
Don't laugh! This is basically how racing engine builders make precisely aligned crankshaft ends on their piston rods. The two halves will align perfectly upon reassembly. The leftover bits should not matter too much for your purposes and the weight loss can be measured and mathematically corrected unless it is in the gap area, right?
3. measure to profile the gap characteristics and component construction aspects in question
4. reassemble as appropriate-- hose clamp the return pot together at first; do not glue until later unless necessary
5. we should have demagged it substantially during disassembly. remagnetize in increments of gauss to plot the frequency and transient response as a function of gross gauss. You wanted to know that as a separate issue anyway.
6. present a paper with:
a. before & after shots
b. video of the disassembly process
c. video of the (fun) breaking process
d. video of critical reassembly process steps
e. CAD x-sect dwgs, tables & graphs of the measurements obtained and your experiment text with conclusions
7. submit the paper to this class for peer review of your work
We will award doctoral degrees in Lansingology for good work. I will expect credit as a co-author (or should that be co-conspirator?) as well and will volunteer for Creative Director for the video release. Royalties and distribution rights to be negotiated.
All we need are specimens, an A/V crew and Lansingology doctoral candidates. Who wants to volunteer?
06-23-2003, 01:48 PM
I see this discussion thread about your speaker is now being used as a reference tool to help sell your speaker on eBay. ... I don't have a problem with that.
Nice one, Earl!
But it would've been proper to have that disclosed in the first post, and maybe start the thread in "Marketplace".
Another eBay'er - sheeze! :mad:
The history and engineering contributions from the knowing have been worthwhile, indeed.
06-23-2003, 09:36 PM
From this and several other informative sites I have gained knowledge of speaker selection and tuning to use in my restoration and repair business. If you want to start another thread for the current discussions, OK. I can not change the ebay listing now. My intent for referencing this thread was for ebayers to see how and where the facts were derived. The Lansing Heritage site was the best place to gain the info on this little known model. All other relevant data links were included, too.
I have a genuine interest in the design, performance and history of audio gear, among other things. I do truly appreciate the information from this site and forum members. Anybody who feels I was not up front about the intentions for this piece was not reading carefully. The message was early and clear;
POST #2; "BTW- Now you can see I'm not some pawn shop reseller who slaps a $$$ label on everything old and dusty. I find the ultimate app for good old stuff or sell to someone who does."
We were still determining the real specs and applications at this point...
POST #5; "Look for an ebay item something to the tune of 'vintage 15" JBL University Jensen speaker set NR' in the next week or so. Unless I take up an offer in the meantime. I don't see much demand for this series on your marketplace. So
that's a rap for this topic... unless a Lansing collector needs one?"
That was a chance for forum members to buy before the rest of the world. And to look for it if interested. This is a personal item not connected with my vintage audio business. Another plug? Each reader can decide for themselves.
Was my ebay listing not factual and well researched? I like all buyers to understand what an item really is for a successful deal. I notice many here keep their eyes on the world's biggest marketplace. Maybe some of you buy and sell there, too.
The thread continued into later driver design evolutions and here we are. I have learned a lot more about speaker technology than expected. Thanks again for the insights.
06-24-2003, 08:04 AM
I thought it was pretty plain from your first posting that your speaker was headed to eBay. Obviously that didn't dampen my choice to talk about this class of woofer. As I said before , no problem here as far as conflicts go .
I like the idea of trying to get a fix ( to paraphrase ) on what the actual gap widths were - way back when . Most of your suggestions would be too difficult/costly for one person to implement but an internet group could accomplish similar results by collecting data over a period of time and creating an adhoc database. Understanding JBLs evolution of gap widths , cone weights and magnet strengths would benifit all users / resellers of these woofers. I'd love to know about when JBL started to add weight to the cone of this driver. As Paul Joppa reported in , it seems a certain era of this speaker had @ 60 gram cones vs 80. This is valuable info for those who place a premium on "quickness" in response vs LF extension . The tighter gap, with a lighter cone will create a woofer that should give good emphatic midbass performance ,,, see the E 145 discussion (http://www.audioheritage.org/vbulletin/showthread.php?s=&threadid=361) for more about this . This sort of sound can be very addicting for those who put a premium on midbass quickness.
So - If other readers would take note that for future recones of D-130(s) & 130a speakers to :
(1) take some pictures ( for the records ) of the appropriate distinguishing characteristics ( as mentioned in the 2 JBL notices that Giskard & I posted ) for these woofers
(2) have a reconer make & record actual gap widths before fitting or not fitting a replacement cone.
(3) record the serial number of unit.
(4) if the owner has a pair - make some notes about any apparent performance differences ( especially if the 2 units look to be of different vintages ).
(5) make some TS measuremnts. Off the top of my head I can't provide a link to a site that has sowtware one can download to help in this,,, apparently its out there. Maybe someoone else remembers where this site is .
regards <> Earl K
06-24-2003, 08:16 AM
I am doing a little research out of curiosity to answer some questions I always had… and found your most excellent site, dudes.
Hey, Martin Wizard Labs...
That quote starts your first posting. I nowhere in the first posting can find any reference to your intention to sell the mythical 130, and was interested in the query. Hell, I was one of the first out of the box to try and "solve the riddle" - you even got the post from rare ol' Don McRitchie tossed in. But I backed away after the confusions on whether this was research or promote. In the end, it appears mostly research - odd, since the item is being eBay'ed. I'm perplexed, but it seemed fruitless to offer much more at this point - wait for the buyer to surface and then give 'em all the dry powder.
My view is at the outset you should have posted in "Marketplace" clearly stating:
dudes, I found your most excellent site and am eBay'ing a seemingly rare 130 transducer that I'd like to know the history of. Can anyone help?
That is full disclosure. :)
And it would have gotten nearly the same attention from the knowledgable, for sure.
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