L166 Info

[audiomaniac]

Greetings-

I am new to this forum as a registered member, but have greatly enjoyed the website and the reading the forums for quite a while.

I grew up in the 70s enjoying the JBL sound from friends L100s and my own L88s (couldn't afford the monitors), which got ripped off in transit with UPS in the mid 80s. I've now purchased a pair of L166s and I'm trying to find out as much as I can about their history, design, lineage, etc. Did the 122A and 122A-1 woofers both use Alinco magnets? What were the physical and sonic differences between the 166 and 166-A? Any other information would be greatly appreciated. Thanks in advance!

[4313B]

Here's the tech sheet.

[audiomaniac]

Hey thanks! I also found the L66 Horizon Instruction manual in a thread. It's great how everybody contributes here. Really nice.

[4313B]

Originally posted by audiomaniac
Hey thanks! I also found the L66 Horizon Instruction manual in a thread. It's great how everybody contributes here. Really nice.

You're welcome.

That reminds me - if anyone has to recone a 122A or 122A-1 please send the old mass ring to me.

The 3" rings I'm looking for are 55687 out of the 122A and 52261-0001 out of the 122A-1 and 126A.

JBL no longer seems to have any of these 3" mass rings and I really would like to know their mass. TIA

[Oldmics]

Hi Giskard,I have only one ring out of those speakers.If you really need it for a personal project I will pass it on but prefer to hang onto it for my stock.The weight is 10 grams.Best regards,Oldmics

[4313B]

Thanks Oldmics!

How accurate is your gram scale? 0.1 is sufficient.

The 10 gram mass ring is from which transducer?

[Oldmics]

Hi Giskard
"How accurate is your gram scale? 0.1 is sufficient. "
Its an old "Triple Beam" scale and I have the calibration weights.So its a matter of lining up the arrows.I would say that 0.1 is correct.
"The 10 gram mass ring is from which transducer?"
Now unfortunatly that is a question that I can"t answer with any certainty-sorry.I would hazard a guess and think a 126A since I don"t recall any versions of the 122 ever going thru the shop,but one of the guys may have done one while I was away on a road gig.
Oldmics

[GordonW]

Sounds like the 10 gram ring could READILY be from a 122A. That's about the difference between the 122A/126A moving mass (100g) and the 128H/129H moving mass (90 grams)...

Giskard, I'd help, but the 122A cone assembly I have here, doesn't HAVE a mass ring... just extra-thick Aquaplas on the back of the cone...

Regards,
Gordon.

[4313B]

Thanks guys!

I do know that JBL moved from the mass ring to aquaplas at some point. It's strange that BOTH the 122A and 122A-1 are listed as having either the mass ring or aquaplas. Could be a typo though I suppose.

I would have thought the 122A-1 had a lighter moving mass, hence the addition of the choke in the L166A filter to control any resulting increase in midrange/high frequency misbehavior. I could be wrong.

[Rudy Kleimann]

I have a pair of these I'm reviving. I had the woofers refoamed years ago, before I knew about "JBL reverse polarity convention" I noticed the woofer behaved opposite of my expectations, so I applied a "D" cell battery to the cabinet inputs to get what I thought at the time was "correct" polarity inside to the woofers. This means I connected the woofer to the crossover with the green wire to black terminal, black wire to red terminal. Shortly thereafter, one tweeter died, and the speakers have been stored until this month, when I found a tweeter for it.

I have learned a lot about sound, speaker crossovers, and JBL since then, and am concerned that I don't have the woofer connected correctly in relation to the midrange. It seems I have read on this forum that some JBL cabinets have the woofers wired in reverse polarity to be in phase with the midrange at the crossover frequency, and the tweeter sometimes wired out of phase too for the same reason. It's been 15 years since I last was in these cabinets, so I can't rely on my memory and I don't trust what I see. I smply can't remember how the woofers were wired before I removed them to refoam them way back when...

I have the JBL crossover schematic .pdf (thanks to this forum!), but it is no help when it comes to driver polarity markings. Anybody have some info?

Cabinet marked: L166 Serial #'s 39895 A and 39896 A
Cabinet input terminals are the rare "Twist-lock" type
Woofers are 122A Alnico, with white backside of cone
Crossover includes large E-core choke inline to woofer

[johnaec]

Just reverse the wires from the crossovers to the woofers. Even though polarity was reversed on many JBL speakers themselves, they always specified "black to black" as far as wiring between crossover and speaker.

John

[Rudy Kleimann]

Thanks, John.

I did some digging, and another thread on "JBL polarity conventions" confirmed this. The all-knowing wizard known as Giskard set it all straight there . He apparently owns (owned?) several pairs of L166's. Had it all there for me.

Turns out the whole system ends up opposite to normal convention, and the woofer is connected so that positive voltage applied to the CABINET's Red terminal sucks the woofer in. Tweeter is reverse polarity as well, but gets the xover HF red wire connected to the tweeters' red terminal, and xover HF black wire to tweeter black terminal. this apparently keeps the woofer and mid in-phase at crossover; mid and tweeter in-phase at crossover.

I'm switching them now and give 'em another listen. It's been years since I used these things. Can't wait to crank 'em up! My JBL/Urei 6290 is warming up beside 'em...