JBL D120 reproductions

[Harvey Gerst]

As far as I know, it stands for Direct Coil Resistance or Direct Current Resistance.

John

That's probably a "righter" definition than mine.

[horseshead]

From the large number of repairs we/I/JBL was getting back from these amp manufacturers, two things became apparent to me:


2. The standard D130 and D131 wouldn't hold up long-term as an OEM product for musical instument applications.

I approached Bill Thomas to let me design some speakers for this market that would:

1. work better without blowing up (due to mismounting, and surrounds
drying out and cracking),


Bill agreed, and I came up with the D110F, D120F, D130F, and the D140F.

While I would have liked to include the lower powered D123 in the MI line (for use in multiple 12" speaker systems), I decided that the popularity and power handling of the already well known D131 would probably give the D123 limited appeal. The D123's sound great in a Twin, for example, as long as you don't push them really hard. I had a D123 in an Ampeg Portaflex, and it was a wonderful sound.

The D110F in fact uses the D123 motor (magnet assembly and 3" voice coil).

So, the C39 with four D123's and an 075 was strictly a home hi-fi speaker, while the D130's and D131's did see early MI use, until the introduction of the "F" series.

That clear things up?[/quote]

Yes, mostly. Guitar amplifier speaker longevity doesn't appear to be something that I, for the most part, with my low volume and light touch type of playing/music would have to worry about.
It sounds to me that when you were saying that longevity of the D130 and D131 was a problem in musical instrument applications, you were refering to rock players and hacks. (not to say they're the same, I'm no snob nor am I a stranger to rock and a physically intense style of playing) they just happen to share a preference for loud volume and a heavy touch.
Therefore, the D131's might be something that I would like to buy as one of the possible varieties of JBL 12's for my guitar amp. But I'm still not sure which stereo systems came with the D131's - JBL stereo systems? Which ones?
Rick

[Harvey Gerst]

That clear things up?

Yes, mostly. Guitar amplifier speaker longevity doesn't appear to be something that I, for the most part, with my low volume and light touch type of playing/music would have to worry about.
It sounds to me that when you were saying that longevity of the D130 and D131 was a problem in musical instrument applications, you were refering to rock players and hacks. (not to say they're the same, I'm no snob nor am I a stranger to rock and a physically intense style of playing) they just happen to share a preference for loud volume and a heavy touch.
Therefore, the D131's might be something that I would like to buy as one of the possible varieties of JBL 12's for my guitar amp. But I'm still not sure which stereo systems came with the D131's - JBL stereo systems? Which ones?
Rick

The original D130's and D131's had two basic problems:
1. The speaker surrounds dried out, got brittle, and cracked.
2. The ham-fisted idiot installers at Fender used power tools to tighten down the speakers, warping the speaker frame, which wound up shorting out the voice coils. I talked to Dick Stout and Forrest White at Fender many times about this. My explanations of how to mount the speakers correctly were ignored.

If you installed the D131's correctly, and don't expose them to extreme temperature changes, the D131's should work fine. Leaving the speakers in a hot car for several hours, or playing outdoors a lot will wreck the surrounds.

As far as home hi-fi's that used the D131, it was usually used in a small system paired with the D175DLH, and later with the 075. The D131 was not a particularly popular speaker. It was basically just a D130 on a 12" frame, for people that wanted the D130 sound, but didn't have the room for a 15" speaker. The JBL catalogs from the 60's are on line here and show which JBL home hi-fi systems were available with the D131's.

As far as a "light touch and low volume", that's exactly why I recommended the D123's as the best 12" speaker choice for your playing.

[toddalin]

Are those the ones you already let go for $90? If not, then I would need to know if they are original cones before offering a price.

Rick

Gone. You snooze, you loose.

[horseshead]

The D131 is slightly more efficient than the D120F - because I opened the gap slightly on the D120F to prevent the voice coil from rubbing and burning out. The difference in efficiency between the two models is negligable. The D120F will keep working for a lot longer than the D131, under harsher conditions.

Thanks Harvey for taking the time to share your experience and knowledge.
Some speakers are marked D120 and some speakers are marked D120F. Is there any difference in the speaker itself? I've read your posts explaining the difference between the D130 and the D130F.

Rick

[Harvey Gerst]

Thanks Harvey for taking the time to share your experience and knowledge.
Some speakers are marked D120 and some speakers are marked D120F. Is there any difference in the speaker itself? I've read your posts explaining the difference between the D130 and the D130F.

Rick

Shortly after we introduced the MI line of speakers, Fender agreed to distribute these JBL MI speakers to musical instrument dealers since they already had most of the MI dealers in the country. (We only sold to hi-fi stores.) I don't remember changing the name of the D120 to the D120F.

(My recollection is that there was never a D120; it was always called the D120F. But enough people have told me that they've seen speakers marked D120 to make me believe it.)

I believe the first D120's had the "F" added as a punchmark; later, the F was printed directly on the foilcal. But, it was a very long time ago, so my memory may not be accurate.


Getting old really sucks!

[Rudy Kleimann]

I have an original pair of JBL 2130's which, according to the alpha-numeric model number listing descriptions is the professional series model number equivalent to a D120. If your memory is right, would this also mean the same as D120F?

My 2130's were used in a pair of '70's vintage custom-made stage floor monitors with the 077 "bullet" tweeter. Cabinet was well-made, and the crossover components were top-notch. The drivers are in good condition, just dusty, dirty, and minor oxidation of the aluminum dust cap and the bullet tweeter horns. No liquid damage. They play fine. Consecutive serial numbers on the drivers .

Story has it that these stage monitors and the road case they are in were part of Z*Z*TOP's touring system that was stolen after a concert in Phoenix, AZ in the '70's. A friend of mine was in a band during his College days in Phoenix and bought them a couple days after the theft incident. He never knew the origin of them, but after hearing of the theft, figured it out. Research I have done on the story and the cabinets themselves seems to bear this out as fact. Interesting trivia...

Harvey, my question has always been what to do with the woofers? How well would they perform as guitar speakers for studio use or occasional gigging. I have a vintage fender Bassman amp that works, but no guitar cabinet for the 2130's. Building one would be no problem for me though.

I'm reasonably certain that the 2130's would never be damaged by my Bassman, but how much "guitar playin' abuse" tube power (rated amplifier power in watts of a tube head) do you think these 2130's would tolerate?

Lastly, I'm interested to know anything more about the "other taps" of Fender amp output transformers. How could I identify these? would a DCR check from a common lead to the other taps accurately ID the other taps re: other output impedances compared to the DCR of the known one currently in use in my amp?

[Harvey Gerst]

I have an original pair of JBL 2130's which, according to the alpha-numeric model number listing descriptions is the professional series model number equivalent to a D120. If your memory is right, would this also mean the same as D120F?

My 2130's were used in a pair of '70's vintage custom-made stage floor monitors with the 077 "bullet" tweeter. Cabinet was well-made, and the crossover components were top-notch. The drivers are in good condition, just dusty, dirty, and minor oxidation of the aluminum dust cap and the bullet tweeter horns. No liquid damage. They play fine. Consecutive serial numbers on the drivers .

Story has it that these stage monitors and the road case they are in were part of Z*Z*TOP's touring system that was stolen after a concert in Phoenix, AZ in the '70's. A friend of mine was in a band during his College days in Phoenix and bought them a couple days after the theft incident. He never knew the origin of them, but after hearing of the theft, figured it out. Research I have done on the story and the cabinets themselves seems to bear this out as fact. Interesting trivia...

Harvey, my question has always been what to do with the woofers? How well would they perform as guitar speakers for studio use or occasional gigging. I have a vintage fender Bassman amp that works, but no guitar cabinet for the 2130's. Building one would be no problem for me though.

I'm reasonably certain that the 2130's would never be damaged by my Bassman, but how much "guitar playin' abuse" tube power (rated amplifier power in watts of a tube head) do you think these 2130's would tolerate?

Lastly, I'm interested to know anything more about the "other taps" of Fender amp output transformers. How could I identify these? would a DCR check from a common lead to the other taps accurately ID the other taps re: other output impedances compared to the DCR of the known one currently in use in my amp?

If it's the same as a D120, it should be the same as a D120F. It should handle the output of a Fender Bassman. Simple test: Try it. Keep turning it up till it sounds like it's starting to strain, then stop. I don't know anything about the 2130's so I can't be of much help.

As I recall, the unused taps on a Fender output transformer are just sitting there. I'd call Fender and ask for the output transformer color codes. DCR measurements would be pretty damn low so, knowing for sure would be better.

[moldyoldy]

........Lastly, I'm interested to know anything more about the "other taps" of Fender amp output transformers. How could I identify these? would a DCR check from a common lead to the other taps accurately ID the other taps re: other output impedances compared to the DCR of the known one currently in use in my amp?

Just in case you've not found it, The Fender Amp Field Guide may have the color code for your OPT (and a wealth of other Fender info);

http://www.ampwares.com/ffg/

IIRC, some models even had balanced output taps.

[horseshead]

Just in case you've not found it, The Fender Amp Field Guide may have the color code for your OPT (and a wealth of other Fender info);

http://www.ampwares.com/ffg/

IIRC, some models even had balanced output taps.

My amplifier tech said that in my fender quad reverb, for example, it is possible to connect either two speakers or four speakers - as long as the total impedence of the speakers equals 4 ohms in the case of my amp's output transformer requirement, or whatever the impedence in ohms of your amp's output transformer requires. As Harvey also said, make sure
all your speakers are rated the same impedence; for example, either each speaker rated at 8 ohms or each speaker rated at 16 ohms, etc.
Rick

[Rudy Kleimann]

Just in case you've not found it, The Fender Amp Field Guide may have the color code for your OPT (and a wealth of other Fender info);

http://www.ampwares.com/ffg/

IIRC, some models even had balanced output taps.

Thanks for the link. I'll check it out.

I've been told that the Bassman is an old favorite for lead guitar players. Brian Setzer's Sound was one example. I look at it as a modest-power vintage Fender tube amp to add to the arsenal. Modest power keeps the volume on stage (or studio) to a more manageable level- an important plus in my mind as a sound engineer.

What do you mean by 'balanced'? A center-tapped output?

I'm no tube guitar amp wizard, but AFAIK the only thing that would make a transformers' output unbalanced would be to ground one lead of the output. I have always understood that the lead marked "common" simply meant that it was the lead attached to the beginning of the output windings, with the other impedance taps being more or less number of turns in the windings from the "common" end.

The only thing I can think to do with a center-tapped output would be to attach the center-tap to the mid-point between two speakers connected in series to the "balanced" outputs. Perhaps this would provide better damping? Just a guess...:dont-know

Always interested to learn something new...

[moldyoldy]

No, I didn't mean center-tapped secondaries, just 'floating' (ungrounded) secondaries. Only mentioned it so you'd take notice when studying the schematic. Ungrounded secondaries should be kept ungrounded. If you were doing a custom job, and installed a grounded-shield TS jack for speaker outputs on the chassis, you could get in trouble.

(Added edit) More to the point. Your understanding is correct that unbalanced outputs (in this app) have one end of the secondary coil (labeled 'common') connected to ground, and the remaining taps are of varying turns from common, and all are far beyond center. Most tube guitar amps ARE 'unbalanced' as described, so I thought the mention that a few old Fenders were 'non-standard', in that they were balanced (ungrounded) might be important to mention if you're gonna be rewiring the OPT. Since there's no other channel to reference phase with, that issue's moot here (with the exception of effects on acoustic feedback). Tube amps mostly have unbalaced speaker outputs more for safety (grid HV on the primary) than for signal.

I've never seen a center-tapped secondary in a guitar amp OPT. It would take some creative winding to allow one to work as you described with two speakers. Since tube amps are impedance-matching devices, damping is strongly influenced by the driven impedance (speaker), and the JBLs mentioned (as well as Altec 417s and Jensen P12Ns) are a wonderful match, some feel, made in heaven. (End of added edit)

Yeah, the old Bassmans are a fave of mine as well. The low to medium powered old Fenders (mainly the 6V6 ones) are often too weak for stand-alones for gigging, but they can be cranked into clipping while still at modest levels, and mic'd to get any output level you desire. Makes them really more versatile than the big boys, where you're making ears bleed just to let your amp "sing" a little. Just leave 'em on 10 and control your tone at the guitar.

[Tom Loizeaux]

...Yeah, the old Bassmans are a fave of mine as well. The low to medium powered old models are often too weak for stand-alones for gigging, but they can be cranked into clipping while still at modest levels, and mic'd to get any output level you desire. Makes them really more versatile than the big boys. Just leave 'em on 10 and control your tone at the guitar.

I don't know about being too weak. My '62 blonde Bassman holds it's own in a variety of band set-ups. (Yeah, I play it on 8 to 10 in those situations)
Sure, 100 watt Marshalls can cover me up, but I don't play in "stupid loud" sessions anymore.

Tom

[moldyoldy]

I don't know about being too weak. My '62 blonde Bassman holds it's own in a variety of band set-ups. (Yeah, I play it on 8 to 10 in those situations)
Sure, 100 watt Marshalls can cover me up, but I don't play in "stupid loud" sessions anymore.

Tom

OOHHH YEAH! '62 Blonde! Best of the Best!

I should've elaborated, didn't mean to include the Bassman in my later reference, which was targeted at the smaller 6V6 models. Most of the 6L6 models are sufficient for small clubs by themselves. (I edited my previous post to clarify).

[Rudy Kleimann]

I appreciate the info. As I said I'm a Sound Man, equipment repairman, and a horn player (Commercial Electrical construction is my day job). Guitar amps and cabinet setup and tweaking is not my strong suit. But I know how to work on them, and a good speaker cabinet will be a breeze for me to build.

I don't know too much about my Bassman except that it is a vintage model, the high-gain input doesn't work right, and it's not a blond. But it does have the tube complement label inside it, so I should be able to ID it.

I look forward to hooking up the two 2130's in parallel to the 4ohm tap set on the XFMR, and inviting a couple of good guitar playin' friends over to put it through its moves. Time to dig it out of the shed, do my homework, and get to work. Soon as I get the 100 other projects caught up...

One thing I HATE:
Young kids (or old kids for that matter) on stage with 100 watt Marshall amps and Marshall 4x12 cabinets screaming at the one part of the audience the cabinet happens to be pointing straight at. A Mix Engineer's nemesis, to say the least...

I've done club gigs with guys like this that were so freakin' overpowering loud that the rest of the band (heavily mic'd drums, D.I.'d Keyboards, and DI'd Bass, 4 vocals) playing through a pair of JBL SR4733X (2-2226H's and a 2447J on a 2381 horn) powered by a QSC MX3000a (rated at 1250WPC@4ohms into each cab) or a pair of bridged Mackie 1400's could barely keep pace with the guitar amp. And the people in the audience up front could hardly stand it. I ran it from the back of the club on a 100ft. snake, and my ears were pretty tired by the end of the night. No amount of reasoning could get the guy to turn it down.

Next gig, I convinced him to turn the cabinet sideways on stage, hoping his fellow musicians might get tired of it and rein him in, but they just loved it. Even turned him up in the monitors hoping they would get the message, but they got pissed at me instead. "I just don't get the tone I like if I don't play loud..."

Smaller amps help two ways: lower volume, and still get that crunch and overdrive saturation tubes are good for. I can mic it if I need to.


Any suggestions on cabinet design? Open back, 1/2 open, or sealed? What cabinet volume? Insulation or no?