nakamichi vs threshold

I thought at one time back in the late 70's early 80's that Threshold designers designed the high end Nak stuff...
Not sure about the power amps but the Nak CA-7 and CA-7 preamps were designed by Threshold because Threshold was purchased by Nakamichi at the time. So there may less of a difference between the Nak and the Threshold than you might think, depending on when both were manufactured.

I owned a JBL L212 system (and have just restored it) purchased in the late 70's. Your system has the same midrange and tweeter, but a separate bass driver. The L212 has two monolythic L/R driver cabinets with a powered sub, and efficiency is about the same as your L112s at about 90 dB/watt.

I can tell you from my experience you can drive those to very high levels with a power amp of under 100 watts. They are highly inductive, however, so the power amp must be designed to tolerate wide swings in driver impedances.

BTW, I would look into upgrading the cross overs in a JBL that old before I spent mega bucks on a power amp. They were the major weakpoints in those 80's JBL systems IMHO.

Lionelplouf

Janzen makes a "kit" for Horizons (L110s) but I don't think those are correct for the L112.

If you can find a schematic, I would build my own. Thats what I did for the L212. The advantage to building your own is you can upgrade the components. JBL used iron core inductors which you can replace with air core Janzen or Erse. JBL used wire wound resistors which can be replaced by newer non-inductive types. JBL used mylar (polyester) film caps which be upgraded to polypropelene film. The "pots" for presence and brilliance are standard 8 ohm L-pads available though a number of speaker building parts sources.

For the schematic, you may be able to get one from JBL customer service (Harman CS) at

hcgcustomersupport3@harman.com
http://www.harman.com/

The guys at Lansing Heritage Forum can also be quite helpful is getting historic JBL info.

As far as getting the upgraded components, these are commonly available through a number of sources. I get mine parts from Parts Expess online.

If you email me, I can send you photos of my upgraded crossovers.