JBL D120 reproductions

[moldyoldy]

Your layout tag will have a model, such as 5E3 (sounds like a tube #, but it's not), which is the number to use to select a schematic.

If it's been in the shed or otherwise unused for a couple years or more, I'd recommend a slow, Variac start-up to reform the electrolytic caps.

For your 100W Man, you've got 2 options; find out if he's using a master volume model, and, if so, show him how to get the tone he wants at the pre, and turn the master down, or.....if all else fails, insert a quality AC controller in his line V. supply, and brown him down to 90-100VAC or so..... won't hurt a thing. The rest of the band will likely cooperate, too....... (Edit: my latter suggestion was a poor attempt at humor, do NOT mess with a musicians' power source!)

For the cab, why not clone the real thing? Dimensions, pictures, schematics, and details for most models are at the site I linked to earlier. Naturally, they also sell tolex, cloth, pts, etc.

[horseshead]

Harvey - when purchasing JBL's online, my lack of experience and knowledge, especially not physically being there to check out the speaker, I am at a loss to know what to do about it. What would be your recommendation regarding such defects as a pinhole or small tear in the surround and/or cone edge? What would be compromised by buying a speaker such as that? Rick

[edgewound]

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?

We've discussed this before about stage volume and it's OT in this thread, but here ya go.

Plexiglass in front of the speaker cabinet will appease everyone. Then mic it to taste for front-of-house. It's a cheap alternative before trying to fool anyone electrically....which could be called vandalism.

[moldyoldy]

Good points Edge. To clarify my brown power suggestion (plus wink) for others, it was a joke that I thought Rudy, as an electrician, would get a grin at, and I hadn't considered that some might take it seriously. I'll add an edit to clarify the post. Enough OT for me.

[Hamilton]

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...

Do guys really do that?

[edgewound]

Good points Edge. To clarify my brown power suggestion (plus wink) for others, it was a joke that I thought Rudy, as an electrician, would get a grin at, and I hadn't considered that some might take it seriously. I'll add an edit to clarify the post. Enough OT for me.

I knew a few guys that would use a variac with their Marshalls and turn down the AC to about 90 volts to get a cool tone. Don't know how that affects the amp, though....effects work like crap and so do PA amps.

Eddie Van Halen went the other way and cranked his AC to 140 volts to get that gnarly tone on his early records. Kinda hard on the tubes...and everything else for that matter.

[moldyoldy]

Yeah, I've left several tube amps on the bench at 90VAC on the Variac overnight with no apparent ill effects, and many will actually play down to 60VAC. Still, it would be a dirty trick to play on anyone, even though it might help prepare them for the inevitable screwin's they'll get at the hands of producers and record labels......

Ooops! said I was done OT...

[spkrman57]

Yeah, I've left several tube amps on the bench at 90VAC on the Variac overnight with no apparent ill effects, and many will actually play down to 60VAC.

With 90 volts to the amp the rectifier(usually 5U4 or 5AR4) would be running at less than the 5 volts on filament and probably less than the required current to properly cause the electrons to leave the cathode.

While it will work(not blow up or shut down), I would say it will probably reduce the lifespan of the tubes!

Ron

[Rudy Kleimann]

Do guys really do that?

ROFLMAO!

Hamilton, you and your Avatar are living proof!

It's fine in the right Venue, but a 100-200 seat club is not it.

I'm as guilty as the next guy, but I use a Trumpet to do it instead of a guitar and amp. I don't think it ever offended ANYONE

I could be wrong, though

[toddalin]

I knew a few guys that would use a variac with their Marshalls and turn down the AC to about 90 volts to get a cool tone. Don't know how that affects the amp, though....effects work like crap and so do PA amps.

Eddie Van Halen went the other way and cranked his AC to 140 volts to get that gnarly tone on his early records. Kinda hard on the tubes...and everything else for that matter.

Ever try to play a Hammond on a LARGE portable generator! The Hammond works by locking onto the 60 cycle a/c and in this case it wouldn't! The tone wheels were all over the place! Neigher my Moog nor my Electrocomp synthesizers would hold tone either.

Also burned out all of our Acoustic amp power transistors (Acoustic Model 270).

[Rudy Kleimann]

Your layout tag will have a model, such as 5E3 (sounds like a tube #, but it's not), which is the number to use to select a schematic.

If it's been in the shed or otherwise unused for a couple years or more, I'd recommend a slow, Variac start-up to reform the electrolytic caps.

For your 100W Man, you've got 2 options; find out if he's using a master volume model, and, if so, show him how to get the tone he wants at the pre, and turn the master down, or.....if all else fails, insert a quality AC controller in his line V. supply, and brown him down to 90-100VAC or so..... won't hurt a thing. The rest of the band will likely cooperate, too....... (Edit: my latter suggestion was a poor attempt at humor, do NOT mess with a musicians' power source!)

For the cab, why not clone the real thing? Dimensions, pictures, schematics, and details for most models are at the site I linked to earlier. Naturally, they also sell tolex, cloth, pts, etc.

Thanks for all the tips, Moldy! I'll check out the site, armed with your ID information. The cab clone sounds like the right plan. Lord knows I can find enough ebayers selling the TOLEX and grille cloth. Penn Fab makes almost everybody's (including JBL's) metal or plastic cabinet and road case hdwe, and one of their three worldwide offices is only a few miles away from me.

Anybody need any hardware for their JBL or any other Pro cabs or road cases?
Just drop me a line... everything except the "JBL" logo, that is. Corners, handles, butterfly catches, input connection plates, wheels, grilles, carpet, fans, rack rails, drawers, faceplates, you name it.

My Bassman has been used only 3-4 times in the four years I've owned it and I have no history on it, so the variac is a good idea for when I get into reviving it.

Got to admit though, you had me going on the 90V AC to the Marshal JCMxxxx 100W head thing! I'm glad you included the reality check... I'm sure it would bring about some distortion at a much earlier point, but may have been disastrous!

Edgewound: We tried the plexiglass trick with an SM57 (his choice) in front of it, but had the most awful feedback problem that we took it down after the 2nd set and never tried it again. No matter, I don't do sound for that Band anymore. He's the only one I ever had a bad problem with anyway. Garage bands, they come and they go...

[Hamilton]

I agree with Moldy, running a Marshall down to 90-100 vac won't damage a thing, but as spkrman57 says, that might cause some cathode stripping....maybe. I sure wouldn't worry about it, there's guys out there that play that way and nothing goes up in smoke. If anything, the amp runs cooler.

The best and most logical way to calm one of those brutes down is with an attenutor, but they're near $300 :

[Rudy Kleimann]

Looks like the "Power Soak" from the late '70's invented by Tom Scholz of the rock band "Boston" fame. Nothing more than load resistors with high power capacity: Use most of the amp's output to heat up the load resistors and divert the remaining available power to the actual speaker(s).

If you want cone breakup for micing , use the power soak with 1 or 2 drivers instead of 4 or 8. Make those tubes cry or scream at modest spl's.

[Hamilton]

Rudy, your night to mix, would this make you a little nervous?

[Rudy Kleimann]

NICE!

Your rig? (or rather, rigs?) That's for the medium to large nightclub Venues, right?

No problem, although I'd need a little more $$$ for this one, since it's evident that I'll have to bring my own AC Distribution panel and more FOH and monitor gear to keep up. Does the place have a 200 Amp D/S I can hook into? Is the building structurally sound?

Looking at the picture, the Chet Atkins Fender Acoustic Electric looks a little out of place .

Nice drum kit too. Are those SM 81's overhead?