L-100 Crossover design

[boputnam]

Originally posted by dgorshe
the L-100's are at home ... so they are being used in my dads room

Perfect! As we age, our hearing fades. Surely he loves the L100's - as it should be...

You, sir, got the best of the lot. Only go home on holiday, for brief periods...

[dgorshe]

lol

[GordonW]

Here's another alternative crossover that might work. This is from the JBL S-70 Alpha, which except for having an LE20-1 (instead of an LE25, which is functionally equivalent to my ears and measurements despite the cosmetic differences), is the EXACT same drivers (123A, LE5-2, LE20-1/LE25) as an L100 .

The only problem I see, is that the difference in box volume, and therefore the difference in the bottom-end bass "curve shape" of the 123A in the smaller L100 box compared to the much larger S-70 Alpha (2 cubic feet as opposed to nearly 6!) box, may result in the bass-to-midbass/midrange/treble balance, becoming, well, a bit unbalanced. This may be reperable by tweaking mid and tweeter level controls, maybe, maybe not. If the L100s are used near a wall or on the floor, then I'd think the problem would be exacerbated- conversely, if they're on proper stands (say, 12 to 18 inches tall stands), a couple feet from the nearest wall or corner, they may work out pretty well with the S-70 crossover...

Regards,
Gordon.

[GordonW]

Oops, I just noticed- center tapped inductor on the HF section, Giskard, shouldn't a pair of .125 mH inductors wired in series, with the junction between the inductors acting as the center tap, work as a substitute? Or is there a significant resistance in that inductor as well (as in, some resistors needed in series with both inductors)?

Regards,
Gordon.

[4313B]

That's the wrong LX30 - that newer LX30 is for the S21 system (124A/H, LE5-2/LE5H, 077)

I've posted the old LX30 schematic in this thread:

http://audioheritage.csdco.com/vbull...=c533#post6323

The old LX30 is the original network for the C533 custom loudspeaker system designed for Bob Fine. That system morphed into the L100 and 4310.


*****


http://www.audioheritage.org/vbullet...t=lx30#post705


http://audioheritage.csdco.com/vbull...=lx30#post5725

[GordonW]

I guess that JBL screwed up on the S70 Alpha III technical manual then... since the schematic I posted, came DIRECTLY from there. In that, they, specifically, specify the 123A-1, LE5-2 and LE20 as the active drivers...

Regards,
Gordon.

[4313B]

Yes, it is wrong. The LX30 shown on the tech sheet is the LCS component series LX30 designed for the 124A/124H, LE5-2/LE5H, and 077. The original LX30 should be the one on the tech sheet. Easy enough mistake. I show all the differences in the links posted above.

[Harvey Gerst]

Well, George Augspurger designed the x-over for the L-100, so go bitch at him. Ed did the x-over for the 4310, but in Ed's home system, he didn't use any inductors whatsoever in the x-overs - just some capacitors to roll off the bottom end on the mids and tweeters, and some L-pads. I still have that handbuilt system (out of Ed's house) when Edna insisted he "get rid of that monstrosity".

[4313B]

"Well, George Augspurger designed the x-over for the L-100, so go bitch at him."

Hmmm, I can't imagine anyone wanting to go bitch at G.A. about a system designed 33 years ago that ended up being pretty successful and spawned a whole series of follow-ups.

"Anyone want to help me design a crossver for an orginal set of L-100's. the orginals are kinda cheesy and the cut off frequencies dont get the full potential out of the LE5-2 midrange."

If a person has looked at an L100 network next to say an L112 network I can see where "cheesy" might come into play. JBL did get pretty fancy with their various network mounting schemes and purpose-built pcb network boards, "cans", etc. Even back then some people might say an L100 network looked "cheesy" compared with something like an LX4-2 "can" from the later versions of Lancer 77's.

"Ed did the x-over for the 4310, but in Ed's home system, he didn't use any inductors whatsoever in the x-overs - just some capacitors to roll off the bottom end on the mids and tweeters, and some L-pads."

So Ed's home system network became the basis for the network that was used in the later L100A, 4310 (late), 4311, etc. The "story" continues to fill in.

How does the C533 designed for Bob Fine fit in then? I was told the C533 started this whole thing but it apparently used the LX-30 filter (NOT the LCS version for the S21 system) which looks identical to the "newer" 3111 filter used in the 4310 (late).

Here's what I have on the L100/4310. Bo has since worked out all the "polarity" issues with the various LF drivers.

Thanks Harvey!

[Robh3606]

Hello Giskard

Great table but the Le-25's had to cut in there somewhere.

Rob

[4313B]

Yep, you're right. It was used in the later L100's. The chart needs to reflect what Bo has found with the polarity debacle as well.

[Harvey Gerst]

I can't fill in much beyond my previous post since I left JBL right around that time (i.e., the introduction of the 4310 and L100). As I recall, George's recommended settings for flat response out of the L100 or 4310 were about 3 (about 9:00 o'clock) on the midrange pot and 7 (about 2 or 3:00 o'clock) on the tweeter, but my memory ain't what it use to be, so those numbers ain't carved in stone.

I think Ed's mission was to get close to the sound of an Altec A7 with the knobs straight up (hyped mids and slightly lowered high end), while George's settings would get you into the flat ballpark.

Hope this helps a little.

[boputnam]

Originally posted by Giskard
The chart needs to reflect what Bo has found with the polarity debacle as well.

Yup.

I'm just too buried in research right now to Search for that particular post. I will do so, later...

[4313B]

Yeah, that's a problem with all this. Revisions get buried with originals and not in the same place. Someone could easily run across erroneous information. Oh well, kind of like reading genuine JBL literature right?

Anyway, I'm sorry I got happy with the ctrl-c and ctrl-v keys in the original Rob.