Hello JBL Lovers,
since one month my youth dream comes true: I´m an owner of a pair of 250Ti Jubilee. I love them. No WAF needle at all. At school days in my youth I heard the Original 250Ti in an HIFI exhibition in Düsseldorf (Germany) amplified with the extraorinary Harman Kardon Citation XX monster. They played fine songs and when listening to the climax drum solo from Saga ("a brief case") I got tears in my eyes. I swore myself that one day I will get these huge babies.
Well, I read in this forum quite a lot but still have some questions, perhaps Giskard is the right guru to answer but I´m happy for any answers/suggestions/infos etc.
In my 250Ti Jubilee a (expensive! bought by my predecessor) network is used made completely by Mundorf (unbiased)wich gaves too little heights and middle, that I would like to compare once against the biased original (which I also get had of the salesman). There is a -4dB reduction for UHF and -2dB reduction for the HF, which I (hopefully) will change to +- 0 dB this weekend. And another failure was made in taking the wrong value for Resistor R6 (1Ohm instead of 9.1Ohm, how does this result "in the ear", giskard?)
I have read already almost all threads in the forum belonging to this and have some points in the original network schematics that perhaps are false? (e.g. the LE14H-1 with pos. (+) marking in the network schematic stands for "outward cone movement with pos. voltage to red input terminal". My LE14H-1 moves inward in this scenario!
I also read the JBL convention on polarity (for the old chassis), where black in JBL sense is always plus instead of black in the rest of the world. But at some time this was changed to agree with other manufacturers. But when?
The cabling for MidFrequency Chassis (MF) and woofer (Low frequency, LF) are made of "strip and tin" while the others uses male/female connectors to make sure not plugging wrong.
I know simply not certainly which cabling poles to chassis obtains the best results. A/B hearings are not easy but possibly (Phases switch to single chassis like Dr. Electron has told). Sometimes it´s the willing of the designer (G.T.) that single Chassis are plugged in reverse in order to minimize the joint area of frequency through phases rotation.
Who knows which cable connects to which port of any chassis connection originally?
Other hints/success moments? Assembly hint experiences? Questions?
All is wellcome. All listeners are wellcome to hear here...
Hope this text is not too long/too bad english or boring too much.
Pictures can be send if some wanted.
Thank you very much in advance and sincere greetings out of Ebringen (in Freiburg, D)