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Thread: 250TI Jubilee spikes

  1. #16
    CLASS A
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    Originally posted by Giskard
    The bypass caps are the little blue doohickies. Try AUDIOCAP PPT THETA .010uF-600V FILM/FOIL CAPACITOR in their place. These caps sound fantastic biased (charge-coupled) or un-biased. Buy a few and try them before buying a whole bunch.
    Thanks for that. Are the blue doohickies you are refering to are the tiny blue capacitors on pic 2 underneath side between the bigger blue capacitors?. What improvement can I expect?.

  2. #17
    CLASS A
    Guest
    Has anyone got a copy of the cross over network diagram of the JBL 250Ti jubilee or where I can download one from.
    Thanks

  3. #18
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    Talking Oh oh,,, you've opened Pandoras' box

    Hi
    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 .

    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
    Last edited by Earl K; 09-27-2004 at 05:35 PM.

  4. #19
    CLASS A
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    EARL k
    Thanks for all that info, I will have to take the network out again tomorrow to find out the values of the capacitors for you.
    I have owned a pair of Kef R105/3 before the jubilee and exchanged all of the capacitors to supersounds and hoveland musicap ( treble) and the result was outstanding.
    One concern about tackerling the jubilee is that the cross over network board is small and I might run into space problems if fitting the large in size capacitors.
    Thanks

  5. #20
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    Thumbs up You're Welcome

    Hi CLASS A,

    Before deciding on what brand of Film & Foil polypropylene to buy, give the info gathering/opinion process a bit of time to see if anyone weighs in with an experience about DC biasing "Hovlands".

    My intuition is that they are already "too long" physically & more importantly too long electrically - placed "end to end" to meet an as yet " inarticulated" criteria for "DC Biasing" .

    ***One reason capacitors can sound different is the physical ratio of length to width ( among many, many other factors ) .***

    <> Earl K

  6. #21
    dieterj
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    Re: 250TI Jubilee spikes

    Originally posted by CLASS A
    Dear all
    I have recieved my pair of 250 ti jubilee last week and absolutly over the moon with them. My concern is regarding the stability of the speakers. I have concret floor with carpet and as the speakers only have round metal feets, they rock about when I gently push them. I m sure there must be a better solution to get them sitting firm. Unfortuneatly, there is no way to remove the round feets, I have taken out the cross over to look inside and there are no screws attaching the feets within. Have any of you got a better solution to stabilize the speakers.
    I have also noticed with I took the cross over out to realise the capacitors used are of low grade quality ( elna ) blue in color. Has anyone used better quality capacitors and of what make.
    Thanks in advance.
    Attached Images Attached Images  

  7. #22
    CLASS A
    Guest

    Re: Re: 250TI Jubilee spikes

    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

  8. #23
    dieterj
    Guest

    Re: 250TI Jubilee spikes

    Originally posted by CLASS A
    Dear all
    I have recieved my pair of 250 ti jubilee last week and absolutly over the moon with them. My concern is regarding the stability of the speakers. I have concret floor with carpet and as the speakers only have round metal feets, they rock about when I gently push them. I m sure there must be a better solution to get them sitting firm.
    Thanks in advance.
    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

  9. #24
    CLASS A
    Guest

    Re: Re: 250TI Jubilee spikes

    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

  10. #25
    dieterj
    Guest

    Re: 250TI Jubilee spikes

    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

  11. #26
    CLASS A
    Guest

    Re: Re: 250TI Jubilee spikes

    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
    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

  12. #27
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    "Now, i'm little bit confused about the Crossover, because i can't understand, why Jbl put this cheap capacitors into?!"

    Size and cost constraints. The bypass capacitors improve the performance of the cheap main capacitors.

    "But i think the Sound now with the original crossoverparts isn't realy bad."

    Nope, it shouldn't be.

  13. #28
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    "I will keep you informed which capacitors used and end result of it all."

    Yes, the various types of capacitors can have dramatic effects on the stock systems. Sometimes the effects are less than desirable and sometimes they are significantly better.

  14. #29
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    0.01 uF RelCap Polystyrene and Foil - excellent depth
    0.01 uF AudioCap Polypropylene and Foil - excellent attack and decay
    24 uF SoniCap
    stock 32 uF NPE as used in a "typical" JBL network

    SoniCaps don't require bypass capacitors or biasing and they are very expensive.

    The stock NPE and Mylar (Polyester) JBL capacitors benefit from both bypassing and biasing.
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  15. #30
    RIP 2011 Zilch's Avatar
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    You know,

    I'd take one look at those crossovers having what appears to be about 20 nonpolar electrolytics each on them, bypass capacitors already in place, and 9V biasing as well, and my subjective assessment that the systems sound damn fine just as they are, and assume that JBL knew plenty well what they were doing there.

    Another project for another day, I might build my own hot-rodded crossovers separately and keep the originals intact so that my ill-conceived blunders are reversible. A premium limited-edition system like that is not gonna resell as well with the disclosure that the owner has "customized" the stock crossovers.

    Maybe I'd concentrate on figuring out how the feet are attached, instead, though there's a contradiction inherent between spikes and concrete floors. There seems little point in merely snagging the carpet backing.

    Your mileage may vary....
    Last edited by Zilch; 09-28-2004 at 10:33 AM.

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