Oh oh,,, you've opened Pandoras' box
Hi
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Has anyone got a copy of the cross over network diagram of the JBL 250Ti jubilee or where I can download one from.
Well I haven't come across one. You might have to reverse engineer that circuit board backwards from the accompanying internal wires .
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What improvement can I expect?
If you swap out all those big blue electrolytic caps for the "Film & Foil" types that Giskard has recommended - you'll significantly increase the ability of your speakers to produce a deeper , more defined sound-stage. Of course, there are a lot of other parts to your system that contribute to this area - as well as the acoustics of your listening area .
I've never seen the inside of one of those crossovers before and I must say that I'm somewhat shocked at the quantity of electrolytics populating that pictured circuit. I've played with DC biasing electrolytics as well as DC biasing great quality Polystyrene bypass caps. I've found that for my sonic purposes ( & with the electrolytics I've used ) that I need to use at least 50% of the final value from higher quality type caps when blending sounds into the base caps'( electrolytic ) signature sound, This ratio ( for me ) is the amount necessary to submerge the sonic signature of the electrolytic. IMHO, at a 50% ratio , there's just no economic advantage in maintaining any electrolytic caps within the series portion of the circuit .
So:
Start with replacing the caps found in the four circuits that are in series with the drivers. If the cost of film & foil types is prohibitive then buy some decent metallized polypropylene types ( Solen 250 volt types can work ). You'll want to do as Giskard has suggested and "Bypass" these Solens with small value Polypropylene film & foil types . If using Solens I prefer to multiply Greg Timbers suggested "Bypass Formulas" by a factor of 10. That means instead of .01uf I'd use a .1uf film & foil Polypropylene. I also bypass all bypass caps with Polystyrenes. As Giskard has stated numerous times - these put the "air" back into the soundstage. This air can be squeezed out by all caps. I use polystyrenes to "taste" - meaning that they can have so much "air" that they can be used to effectively "blunt" the knife-like edge that a lot of cheaper metallized polypropylene carry as a sonic signature . Effective values end up being equal to or greater than the .1uf mentioned for film & foil Polypropylene bypass caps .
- What are the markings found on those large blue "Elna" caps ?
- Also, the small blue bypass caps - Are they marked as MKP or MKT or something else ?
<> Earl K
Re: Re: 250TI Jubilee spikes
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Originally posted by dieterj
thanks for that dieterj.
I have noticed there is another platform underneath the speakers in the same diemention and colour to the piano black. Please tell me how did you achieve that and are the spikes screwed into the bottom platform?.
thanks
Re: Re: 250TI Jubilee spikes
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Originally posted by dieterj
Hello Class A,
I've put 1 inch MDF Board under my 250ti for better sitting.
Can you post, what's the difference in Sound, when you change
some Capacitors?
Regards
Dieter
Dieter
Do you own the jubilee?. the cross over network are different on the jubilee compare to all the rest of the 250ti. There is a 9V battery connection in the jubilee network for the capacitors. How did you get the piano black finish on the 1 inch MDF board?.
Cheers
Re: Re: 250TI Jubilee spikes
Quote:
Originally posted by dieterj
Hello ClassA,
I've also the 250ti jubilee with the 9Volt Batterie.
The MDF Board is not in the same Piano Lack.
It's a normal black glance Lack.
The Spikes're sitting in T-Nuts.
Now, i'm little bit confused about the Crossover, because i can't understand,
why Jbl put this cheap capacitors into?!
The Jubilee was not a cheap Box.
But i think the Sound now with the original crossoverparts isn't realy bad.
Dieter :confused:
I had a shock too when I took out the cross over to find very cheap capacitors used. They can be improved dramatically as I have proven when I changed high grade capacitors into my kef R105/3. I will keep you informed which capacitors used and end result of it all.
I must admit that the sound from the jubilees are great in stadard form.
What front end and ampification are you using to drive the jubilees?. I m using Sony SCD-1, Plinius M8 pre and Plinius SA250IV power ( 250w x2 in class A ).
Cheers