A musician friend of mine is a bit of a vintage collector. He has in his possession a D131F, which has the O-ring groove on the back of the mounting flange. Something the early D131's didn't have. He also has a few speakers labeled, D120. This isn't a case of a letter being rubbed off, he has owned dozens of the model D120 over the years.
Could these drivers have been made during the transitional period when JBL was developing the musical instrument speaker line for Fender?
Wow really. There no reason to use an o ring on a cone driver. There's no way they could create anywhere near the pressure to warrant it. True o ring grooves do not have straight sides. The groove is wide at the top then at the bottom. It keeps the o ring pushing against the sealing surface as its energized. But this happens at thousands of psi unless the o ring has an unheard of low durometer.
Most of the fender stuff was rear mounted on the baffle. Maybe it was done at a later date. Is there paint in the grove? I can't speak for the history of the drive but driver mystery especially jbl mystery is very interesting.
Good luck
Nick
I don't know exactly when JBL began machining baskets with the O-ring groove. Perhaps the practice began when JBL hooked up with Fender, but I can assure you, the company has been doing it for many decades. I have a pair of 2235H in my shop at the moment with the O-rings in place. Every JBL musical instrument speaker I purchased in the 70's came with mounting hardware, and an O-ring, which was an off-white color, then later black. The O-ring was a front mount option, the other front mount option was the gasket that was supplied with the MA15 mounting kit. Even the LE5/2105 had an O-ring groove machined into the basket. You will also find O-rings supplied with the 2300 series conical horns, and the ring radiator series tweeters, including the 2404.Originally Posted by NickH
BTW - I know what the purpose of O-rings are , and what the profile of an O-ring groove looks like. In some industries, O-ring groves have a straight sided channel profile.
"There no reason to use an o ring on a cone driver"
Apparently no one told that to the engineers who design JBL speaker baskets. It's obvious the O-ring was offered to maintain a seal for non-vented enclosures.
"...but driver mystery especially jbl mystery is very interesting"
Apparently, you are the only one who finds the O-ring groove a mystery.
What lukewarm response? Until I came across my friends drivers I have never heard of a D120, nor have I ever seen it offered in any catalog. In my 45+ years of associating with musicians, I have never heard anyone talk about a D120. As I stated, this isn't a case of the 'F' being rubbed off. My understanding from good authority, is that the D120F was the product of a modified D131.Well, the D120 is a 12-inch driver with the same motor as the D130. I always thought it must make an awesome 12-inch but the response to it seems a bit lukewarm.
Sorry about that, I just gave an explenation since its not usual knowledge for most people. Didn't mean to offend.
I've no doubt they did it. It just seems insane overkill. I'd be curious if anyone know why they did that over just a flat seal.
Nick
No harm, no foul.
If you have the opportunity to look at the rear surface of the early D131 basket, and perhaps the early 130A and early D130, you'll notice they weren't machined smooth, as at the time they were in production they were rear mounted in HiFi cabinets save for the rear loaded horn enclosures. Having a nice machined under those circumstances obviously wasn't a consideration.
You're right, I was thinking of the D131, but there seems to be both a D120 and D120F. Don't know if this will help: http://www.audioheritage.org/vbullet...-reproductions
and a Google Advanced search of this site will offer several more links: https://www.google.com/search?hl=en&...pe=&as_rights=
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
Thanks. Typically, when musicians speak of D120's, they're really speaking of D120F's. The 'F' is a detail they usually leave out because for the most part, they think the F series was the only series JBL manufactured. Still, the D120's my friend has owned puzzles me.
I have seen that Heritage forum page before. I had to chuckle when some folks on there talked about the D123 as being a guitar speaker. It was not designed as a guitar speaker any more than the D130 was. Granted they sound great at low volumes, but they weren't meant for rugged duty. That's why the D131 was modified to create the D120F, and the D130 was modified to create the D130F. Neither of them are as efficient as their predecessors.
In case you didn't realize it, the guy here who recommends the D123 as a guitar speaker is the same guy who created the F-series speakers for Fender while working at JBL. Most of us here know that the "F" really meant it had a larger vc gap so the ham-fisted assembly line guys at Fender could tighten as much as they wanted or as badly as they would without distorting the frame so much that it bound the voice-coil. We got that explanation directly from Harvey.
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
I've known a few guitar players in the past who loaded their Fender Twins with the D123 because of how good they sounded. Every one of those chaps blew them up. I'm not suggesting the D123 isn't a great sounding guitar speaker, I am stating the D123 was not originally designed for electric guitar. I think it makes for an awesome recording speaker, but used as a live speaker in a loud bar band? I think not. As a bass player I have used a D120 in a very small vented enclosure for recording. Would I ever take it on a gig? No. And on the Twin note, I've known those same guitar players to blow up K & E 120's as well. As they provide minimal acoustic loading, JBL's were not meant to be loaded into amp combo enclosures. I suppose the proof of that would lie in the warranty records at JBL. In all fairness, I've known guitar players who blew up ALTEC 417's loaded into Twins also.
"We got that explanation directly from Harvey"
I was given the history of the F series by Everett Watts, who no doubt learned it from Harvey. I was hoping when I posted the thread Harvey would be able to explain the D131F, and the D120 speakers my friend has.
BTW - The D123 is one of my favorite JBL speakers. It sounds awesome in a C38 with a bullet.
I doubt any JBL was originally intended for music instrument amplifier use, but they were adopted to it and adapted for it. I remember shopping for Standel amps as a kid and there was an upgrade option for JBL D130.
My recollection from the JBL catalogs at the time was the D123 was designed for in-wall installations where it would fit between studs 16-inches-on-center in a wood-framed wall with limited depth.
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
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