nakamichi vs threshold

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.

Thanks a lot for the comments.

I am indeed looking at upgrading the cross overs of my L112s but I do not find the spare parts. Do you know were I can find them?
What shall I replace in priority? Lpads?

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.

Nakamichi stuff tended to sound great but SOME products had reliability issues. DO not know about that particular one.

I had a later day Nakamichi CD changer and head unit for my car. The CD changer had issues. The head unit which included the amp worked fine for years. Best sounding car stereo I ever had! I wish it still worked and I still had it.

Myself I'd be sure to confirm the history of any particular Nakamichi item from a reliability perspective with the seller if possible before dropping a lot of cash.

Older gear is always subject to more issues. Nak is no exception. The market tends to reflect that. Items like CD players, record players and tape units that have moving parts are usually the highest risk.

When Nak amps work, its generally good sounding stuff. Its worth consideration if the price and history is right, or if the seller will offer a money back guarantee perhaps, but be careful and protect yourself whenever buying used, especially with vintage gear!

I've heard a good number of technicians comment about that design- as I understand it, it is one of Nelson's earlier designs but due to construction or other factors did indeed have a reputation in the service industry (I ran a service shop for 15 years before going into the manufacturing sector) for stability issues.

These days if one has survived I would expect that filter caps should also be serviced out, but there are a lot of amps that are more deserving.

I owned JBL Olympus speakers in the 70s and 80s but I'm not that familiar with the newer models. At 89db, you should not have any trouble driving them with either the
PA5 or PA7. As I'm sure you realize, the 5 is simply a junior version of the PA7. For the extra couple hundred dollars, I would get the PA7 so that you'll have enough power down the road if you should get any of the newer, power-hungry designs that are being offered today.

A buddy of mine had the PA-5 I think it was. Great sounding amp. I remarked over and over how good I thought the amp was. If it had reliability issues I know for a fact he never would have purchased it.

Thanks for the answers.
Tonykay, what do you think about the differences between PA5 and PA7?
I am asking myself : Maybe PA7 is a bit over dimensionned for me, too much heat, too much weight... ?
Will the additional power improve the sound on JBL L112 ? (89db efficiency)
My listening room leasures 25 square meters.

Sorry to disagree, but Nakamichi amplifiers have not had a "reputation for being unstable." Do some research on the internet and I doubt that you will hear many negative comments from current or past Nakamichi owners. Nakamichi amps still sell for a high percentage of their original cost relative to their vintage. I just don't want the OP to take the above comment as the last word on Nak amps. They are a Nelson Pass design and still well-respected today.

FWIW the Nakamichi amplifiers had/have a reputation for being unstable that they had from the very beginning. Its one thing for an amplifier to sound nice, another for it to run reliably from day to day.

Buy the Nakamichi and you will never look back with disappointment.