JBL D120 reproductions

[Rudy Kleimann]

edgewound, AFAIK this absolutely confirms your statement that my 2130 is equivalent to the K120:
http://cgi.ebay.com/ws/eBayISAPI.dll...=7413313412&id=

ebay seller says he removed this original K120 from his Fender cabinet.

The K120 surround is identical to my 2130 surround.

The K120 cone number is the same as my 2130, with the additional "16" penciled on it in white, indicating a 16ohm voice coil. My 2130 cone has "K" penciled on it in yellow.

[horseshead]

I think "doping" is probably a misleading term. The "goop" we used was a super high viscosity oil. It worked well to damp out any ringing from the edge of the cone. It was basically used on the D123 to seal the cloth surround without stiffening the surround.

And the Waldom #AA-75 doping compound is only closer to what was actually used at the time by you and JBL in the factory? In your opinion, would there be a noticeable difference in the sound of the speaker if I coated the surround with the Waldom versus what was originally used at the time on this model speaker in the JBL factory?


No, that's not correct. The "F" series had the top plate opened slightly, to prevent rubbing and shorting in the coil from frame warpage.

Then, wouldn't that mean that the D131F is identical to the D120 which is also identical to the D120F? Only the names are different?


The gentleman from Standel is incorrect. Coating the surround (correctly) neither increases the power handling nor does it stiffen the surround. The D120F is almost absolutely identical to the D131; the D130F is almost absolutely identical to the D130.

I don't want to misquote anyone and I'm suppossed to call him back to finnish our conversation. I'll get back on what he says about JBL guitar speakers later on.

Rick

[horseshead]

Rick,
I understand your frustration, but I can't give the answer you seek, because I don't know it. I posted the reference to Airflex 510 because I knew it to be a preferred doping compound for a long time, though I doubt that it was available in '57-58, or that it was the compound originally used at that time. I also doubt that whatever dope was originally used (if known) is still available today. It's kind of like trying to match paint used back then, in that there's none of the original product around anymore, so the best we can do is get a close match.

Doping a surround does not increase power handling, as that is a function of the heat tolerance and breakdown temperature of the voice coil. Nor does doping a surround stiffen the cone, as it only alters the area it's applied to (the surround). It could however, alter the tone of a speaker by damping edge or rim resonances, in which case it would produce less distortion, or a 'cleaner' sound. Doping is also a permanent modification, once applied, there's no going back.

The characteristics we often find desireable in many classic instrument speakers ARE their distortion products, whether from cone breakup, rim resonances, or otherwise. Personally, I think it's highly unlikely that anyone can EXACTLY duplicate the sound of any 50 year old speaker when it was new. If you're a musician, find a tone you're happy with and go with it. If you're a collector.....well....they don't care what it sounds like anyway, as long as it's 'original'.

I have a couple of questions about edge resonances as I've never heard of them before.

A little background before I ask the questions:

I only buy guitar equipment to play through it, I'm not a collector. But, I have been playing mostly classical guitar lately and IF I play electric, it's been in my house. It's great that I have a goal to first buy the equipment that is as close as possible to that which was used with the Gibson ES345 guitar on the Yessongs album as a reference point to understand what I would need to play through in order to obtain this, my favorite electric guitar sound (since the '70's). That is a fender dual showman reverb with the 2x15" D130F cabinet for the bass pickup and a fender quad reverb for the treble pickup on the stereo guitar.

Getting back to edge resonances, I had heard that the sound of a fender dual showman reverb amp with it's two JBL D130F cabinet with the volume cranked up to 7 or higher actually takes on a freaky, synth-like sound. Is this true, and if it is, does it have anything to do with edge resosnances? And if this freaky sound does happen with this amp/speakers at high volume, given the modest, low power requirements of my playing environment, would it still be possible to obtain that sound with a lower power fender amp driving the same two JBL D130F's or even just one D130F?

BTW, I don't think the quad reverb was used for the Yessongs tour. It was a fender pro, but I saw Yes many times during the '70's - the first time with the dual showman and the pro, and subsequently with the dual showman and the quad and even possibly two dual showmans, and the sound was about the same quality, all great. So I'm thinking that the sound quality is not dependent on which fender amp is used - the sound quality is in the JBL's. Rather, which fender amp used has to do with the size of the power of the amp, how loud you want to turn it up, your volume requirements, and whether you need to have it turned up high for a little distortion or you won't be doing that and you want it totally clean. Myself, I would like to have that ability to turn it up to break up when I feel like switching to that sound and then maybe to clean. But, I think I'm more into the turned up sound.


Rick

[Hamilton]

I saw Yes in the mid 70's and unfortunately we were sitting straight off stage left, I could barely see the backline. I was mostly curious to what Chris Squire was playing but I could indeed see Howe's Dual Showman Reverb.

Other than that I can't tell ya much, except the mix that night was overly bright and thin.

[edgewound]

edgewound, AFAIK this absolutely confirms your statement that my 2130 is equivalent to the K120:
http://cgi.ebay.com/ws/eBayISAPI.dll...=7413313412&id=

ebay seller says he removed this original K120 from his Fender cabinet.

The K120 surround is identical to my 2130 surround.

The K120 cone number is the same as my 2130, with the additional "16" penciled on it in white, indicating a 16ohm voice coil. My 2130 cone has "K" penciled on it in yellow.

Thanks, Rudy.

I'm glad you found proof to substantiate my factory...and experience... supplied info.
It's good to be a detective and confirm the facts for yourself.

[edgewound]

This thread is getting to the point where the ridiculousness of legendary speakers' inflated legends gets bigger than the speaker themselves.

The amount of disinformation is legendary....mythical.

The D120F is a D131 with a coated paper surround and the gap top plate machined out .002" to yield a larger gap from .053" to .057"....as Harvey stated numerous times before to remedy the warping from installers that like to tighten screws too tight...and short out voice coils as a result. Most likely the D131 will have to be machined out to .057" once it needs to be reconed....with a JBL kit, which BTW, is an E120 recone kit

The same story with the D130 and D130F.

The K-series 120 and 130 are indentical structures to their D-series counterparts. The surrounds are m-roll cloth for less cone distortion and lower bass response...and the voice coils are wound on aluminum formers for higher power handling.

The tone one gets out of an amp/speaker/guitar system is mostly dependent on the players ability. Two guitar players will get two different tones based on what comes through your hands and fingers first.

Forty, fifty year old speakers are living on borrowed time. A D120F reconed with an E120 recone kit is a much better and versatile speaker in most cases.

Let's forget about the mythical status of these things and just recognize them for what they are....great speakers....great tools to make music with. Every Artisan uses tools in a different way to make his/her own art with an individual flavor and statement.

[Harvey Gerst]

I have a couple of questions about edge resonances as I've never heard of them before.

Damn, you sure ask a lot of questions!!!

There's no simple answer, so lemme try and make it as non technical as I can:

Guitars, violins, stringed instruments, in fact, all instruments (including loudspeakers) radiate notes differently at different frequencies!! Read that again: Guitars, violins, stringed instruments, in fact, all instruments (including loudspeakers) radiate notes differently at different frequencies!!

What does that mean exactly? It means that different parts of the instrument's body are used to produce different notes! Here is a link that show how the guitar top changes with each note:

Chladni guitar top radiation patterns:http://www.phys.unsw.edu.au/music/gu...erns_engl.html

As you can see, different notes come from different places on a guitar, which brings us to the same condition in loudspeakers. A "perfect" cone loudspeaker should be absolutely rigid, have no mass, and move like a piston at all frequencies.

But perfection is seldom reached in the real world. Speaker cones aren't absolutely rigid, or without any mass, and they don't move like pistons all that well. They can flex, depending on what frequency is involved. Just as when people get angry about something, when a loudspeaker gets hit with a note it doesn't like, it sets it off, and the speaker can howl, producing a note all its own.

They're called resonances, wolf tones, breakup, and a lot of other things, but the result is the same: distortion of the original signal. Sometimes, it can be pleasant; not all distortions are always bad-sounding.

Remember I said earlier that a perfect speaker would "move like a piston"? The part of the speaker that drives the cone is the voice coil. So the thing that makes the whole cone move is that little 4" circle of wire underneath the shiny dome in the center of the speaker. It moves in and out, and the cone moves with it.

But, since the cone can flex (it's not absolutely rigid), sometimes the cone will move like a guitar string, or a wave, with the note spreading out from the center of the speaker, hitting the rim, and reflecting back. That's an edge resonance. Putting goop on the surround is like adding fly paper to the edge of the speaker, or the "Hotel California" treatment (the wave can check in, but it can't check out).

The goop on the surround can solve or reduce some of the problems with edge resonances and reflections, but it can't eliminate the cone flexing problem - nothing can. When you start making the cone more rigid, you increase the mass. Ain't no free lunch.

Designing speakers is all about trade-offs and compromises: pick up a little bit here, lose a little bit there. Want a lot of efficency? It's gonna cost you low end. Want low end? It's gonna cost you efficency.

Does this kinda make things a little clearer, Rick?

[Rudy Kleimann]

Thanks, Rudy.

I'm glad you found proof to substantiate my factory...and experience... supplied info.
It's good to be a detective and confirm the facts for yourself.

I knew you knew what you were talking about, just as I knew Harvey knew what he was talking about. Factory training and experience can't be denied, hehe.

My only mistake was being misled by the errors on the JBLPRO Alphanumeric part number listing prior to reading this thread. You and Harvey set things straight in short order.

I just put these pics up as proof to others. I found 'em by accident on ebay, and couldn't resist.

It seems some of these posters keep going around in circles, and I knew the pictures were proof positive for them -or at least they should be. I was already convinced. If these other guys could "get it"... damn, I'm starting to sound like Giskard...

[Rudy Kleimann]

Excellent post Harvey. How many more questions will this post create?

Maybe you can start an on-line course in loudspeaker driver design theory and application for extra income? That'd make it worth your while, at least

[Harvey Gerst]

Excellent post Harvey. How many more questions will this post create?

Maybe you can start an on-line course in loudspeaker driver design theory and application for extra income? That'd make it worth your while, at least

Naw, this is my way of paying back people like Ed May, Bart Locanthi, Bill Burton, and George Augspurger, who taught me a lotta stuff for free.

I did something similar to this at home recording, explaining how mics work. Some of it is an interesting read. You can find it at: http://www.homerecording.com/bbs/showthread.php?t=27030

I'm really getting too damn old for some of this stuff.

[Rudy Kleimann]

Naw, this is my way of paying back people like Ed May, Bart Locathi, Bill Burton, and George Augspurger, who taught me a lotta stuff for free.

I did something similar to this at home recording, explaining how mics work. Some of it is an interesting read. You can find it at: http://www.homerecording.com/bbs/showthread.php?t=27030

I'm really getting too damn old for some of this stuff.

I was just being facetious...

The world needs more kind folks like you in it. Lord knows I've learned from you in the short time since I first ran across you here, and I, for one, really appreciate you sharing your knowledge.

The home recording forum looks mighty interesting too. Thanks for posting that link!

[Hamilton]

I'm really getting too damn old for some of this stuff.

I can't believe how much I used to worship my D140Fs when I was a kid, and now here's the guy that built them!! But now I'm gettin' too old to be excited.

[BillScintilla]

The D123 will handle a lot more than 15 watts. It should handle as much as a D110F. It should work fine with a 50 or 60 watt amp, as long as you don't push it really hard.

This is my first post and I would like to say a very sincere 'thank you' to Harvey for making my life a better place to live. I have used D120's for close to 40 years and they are a wonderful piece of art and science. I still use one today and would use more of them if I could find them. Also, many thanks to Harvey to being so thoughtful and generous to put his knowledge out there to those of us who truly value it. In other cultures you would likely be thought of and treated with great respect as an 'Elder'.

So, my questions to Harvey please (I hope you still read this thread!) ... why is the the D123 your favorite guitar speaker of all, especially compared to the D140? Is it true there is less bass and, if so, if I use four D123 in a cabinet to move more air will I get the 'missing bass' back compared to a couple of D120's?

And, if you don't mind, what are your musical tastes especially as they relate to guitar playing? I'm just trying to get some insight into what you like to hear.

I have a'63 blonde bassman head (50 watts that I no longer turn up to 10) that I use for rock 'n' roll, country, blues and jazz. Will I be safe in the 5-7 range with two D123's do you think, please?

[Rudy Kleimann]

Welcome to the site! Good to see a man like Harvey get the respect due him. But that's nothing unusual around here- lots of true experts, seniors, and current as well as former JBL employees come here and post from time to time. Even Greg Timbers himself has posted a few.

Do a search for Harvey Gerst on the 'net and you'll find he runs a recording studio in North-Central Texas. Well worth a visit...

Enjoy!

Rudy

[Harvey Gerst]

So, my questions to Harvey please (I hope you still read this thread!) ... why is the the D123 your favorite guitar speaker of all, especially compared to the D140? Is it true there is less bass and, if so, if I use four D123 in a cabinet to move more air will I get the 'missing bass' back compared to a couple of D120's?

And, if you don't mind, what are your musical tastes especially as they relate to guitar playing? I'm just trying to get some insight into what you like to hear.

I have a'63 blonde bassman head (50 watts that I no longer turn up to 10) that I use for rock 'n' roll, country, blues and jazz. Will I be safe in the 5-7 range with two D123's do you think, please?

The D140 was designed for bass, not guitar. But, why do I like the D123 for guitar?

It's one of the smoothest speakers JBL ever made, no ear fatigue. It has a surprising amount of bass because of its cone excursion. A pair of D123's should work well with a 50 watt amp.

As far as my tastes in guitar playing, my first teacher was Barney Kessel, but my influences range from Albert King and Brownie McGee to Merle Travis to Jimi Hendrix. I've played blues, country, folk, jazz, and rock for most of my life.