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Thread: 250TI Jubilee spikes

  1. #31
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    Originally posted by Giskard
    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.
    Thanks Giskard, very interesting.
    Would you change only the Bypasscaps?

    You're always the Men for Jbl

  2. #32
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    "I'd take one look at those crossovers having what appears to be about 20 bipolar electrolytics each on them, bypass capacitors already in place, and 9V biasing, 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."

    Yes... what we do at home stays at home.
    There is quite a difference in what we run at home versus what ends up in production...

  3. #33
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    Originally posted by Giskard
    "I'd take one look at those crossovers having what appears to be about 20 bipolar electrolytics each on them, bypass capacitors already in place, and 9V biasing, 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."

    Yes... what we do at home stays at home.
    There is quite a difference in what we run at home versus what ends up in production...
    you are absolutly right. should I stay with the same values as the standard on the bypass capacitors. I live in the uk and I cant find or source the audiocaps, can you recommend a different make. i believe I m the only 2nd proud owner of the jubilee in whole of UK.
    Thanks

  4. #34
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    Originally posted by dieterj
    Thanks Giskard, very interesting.
    Would you change only the Bypasscaps?
    Tough call.

    Changing the stock metallized polystyrene and metallized polypropylene capacitors to film and foil types can make a pleasant difference. It is the "cheapest" way to go and the least invasive. If one is careful they can easily reverse the procedure should they wish to do so.

    Normally I don't mess with any of the larger networks such as the 250Ti or XPL200A. I just take them out, put them in a box, and start from scratch.

    For instance, when G.T. first modified an original stock 250Ti with all biased Solen capacitors he ended up with a massive headache trying to work the extra, and physically larger, capacitors into the stock boards. Starting from scratch ends up being the way to go.

    Biasing the NPE capacitors, which JBL has already done for you in the Jubilee, goes a long way in improving their performance. In the case of the new SK2-1000, which is meant to mount behind a perforated screen, JBL used all high quality, non-biased, capacitors because of the problems associated with battery changes. This system is designed and voiced to be the center channel for a pair of K2-S9800 loudspeakers. The non-biased high quality capacitors had to have very similar sonic character to the biased mylar and NPE capacitors which are bypassed with metalized polystyrene capacitors in the K2-S9800. Not a small feat.

    Again, I have to warn anyone who wants to start modifying stock filters that JBL does extensive listening evaluations of their systems and changing capacitor dielectrics or inductor DCR values from stock can yield really good results as well as really bad results.

  5. #35
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    Re: You know,

    Originally posted by Zilch
    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.

    Thanks mate
    What other solution would you recommend instead of spikes?. I planning to attach 25mm wide spikes to the original feets as I have tried again to figure out how the feets are attached ( no luck. Cheers

    Your mileage may vary....

  6. #36
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    Re: Re: Re: 250TI Jubilee spikes

    Originally posted by CLASS A
    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
    My Electronic :
    Linn Karik/Numerik - Cd
    Audio Research SP16 - Pre
    Crown Studio Reference 2 - Power

  7. #37
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    Re: You know,

    [QUOTE]Originally posted by Zilch
    [B]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.

    Thanks mate
    What other solution would you recommend instead of spikes?. I planning to attach 25mm wide spikes to the original feets as I have tried again to figure out how the feets are attached ( no luck. Cheers

  8. #38
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    Re: Oh oh,,, you've opened Pandoras' box

    "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 ."

    "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 ."

    Good points Earl! Interesting that you've found the order of magnitude necessary to blunt the metallized polypropylenes! I'll pass that along.

  9. #39
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    Originally posted by Giskard
    Tough call.

    Changing the stock metallized polystyrene and metallized polypropylene capacitors to film and foil types can make a pleasant difference. It is the "cheapest" way to go and the least invasive. If one is careful they can easily reverse the procedure should they wish to do so.

    Normally I don't mess with any of the larger networks such as the 250Ti or XPL200A. I just take them out, put them in a box, and start from scratch.

    For instance, when G.T. first modified an original stock 250Ti with all biased Solen capacitors he ended up with a massive headache trying to work the extra, and physically larger, capacitors into the stock boards. Starting from scratch ends up being the way to go.

    Biasing the NPE capacitors, which JBL has already done for you in the Jubilee, goes a long way in improving their performance. In the case of the new SK2-1000, which is meant to mount behind a perforated screen, JBL used all high quality, non-biased, capacitors because of the problems associated with battery changes. This system is designed and voiced to be the center channel for a pair of K2-S9800 loudspeakers. The non-biased high quality capacitors had to have very similar sonic character to the biased mylar and NPE capacitors which are bypassed with metalized polystyrene capacitors in the K2-S9800. Not a small feat.

    Again, I have to warn anyone who wants to start modifying stock filters that JBL does extensive listening evaluations of their systems and changing capacitor dielectrics or inductor DCR values from stock can yield really good results as well as really bad results.
    Thanks Giskard,
    Now i think, that i stay with the original Crossover

  10. #40
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    Re: Re: You know,

    Originally posted by CLASS A

    What other solution would you recommend instead of spikes?. I planning to attach 25mm wide spikes to the original feets as I have tried again to figure out how the feets are attached ( no luck. Cheers
    If the pic that dieterj posted here is what you have, with screw-in adjustable feet, I'd simply unscrew them completely to remove them, leaving the threaded inserts in place, and see if setting the cabinets directly on the carpet improved the stability. They appear to be mounted near the edges already, so supplemental feet aren't going to help.

    If that doesn't do it, consider two other options which come to mind:

    a) Have much broader "pad" feet made to screw in where the originals came out, say, 4" diameter. They'll stick out beyond the base of the speakers, but may look good anyway, depending on the design. Think "moon pod."

    b) Have machined supplemental sub-base plates of say, 1/2" to 1" heavy material such as stainless steel (expensive), or even thicker stone (cheaper) as a plinth under each speaker. Attach by through-bolting to where the original feet unscrewed, using the same bolt and thread size. If a thinner plate will do the job, attach using the original feet, even. These could be a very handsome modification. The purpose is to lower the center of gravity of the speakers by adding mass to the base, stabilizing them.

    A significant feature of either of these approaches is that they may be removed and the original feet reinstalled later, if desired. No changes are made to the cabinets themselves....
    Last edited by Zilch; 09-28-2004 at 11:50 AM.

  11. #41
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    Re: Re: Re: You know,

    Originally posted by Zilch
    If the pic that dieterj posted here is what you have, with screw-in adjustable feet, I'd simply unscrew them completely to remove them, leaving the threaded inserts in place, and see if setting the cabinets directly on the carpet improved the stability. They appear to be mounted near the edges already, so supplemental feet aren't going to help.

    If that didn't do it, consider two options which come to mind:

    a) Have much broader "pad" feet made to screw in where the originals came out, say, 4" diameter. They'll stick out beyond the base of the speakers, but may look good anyway, depending on the design. Think "moon pod."

    b) Have machined supplemental sub-base plates of say, 3/4" or 1" heavy material such as stainless steel (expensive), or even thicker stone (cheaper) as a plinth under each speaker. Attach by through-bolting to where the original feet unscrewed. These could be a very handsome modification. The purpose is to lower the center of gravity of the speakers by adding mass to the base, stabilizing them.

    A significant feature of either of these approaches is that they may be removed and the original feet reinstalled later, if desired. No changes are made to the cabinets themselves....
    Thanks for that...
    I dont have the set up as dieterj. At the moment, the speakers are standing on their original feets and because it is on carpet, hence they are not stable. The original feets can be turned both ways but they dont extract from the base. I had a good look and feel inside of the base and do not notice anything attaching them from within. if only I can extract the original feets, then I may be able to attach heavy duty spike kits directly to it.
    Cheers

  12. #42
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    Do we have an exploded view of this or similar product showing how the stupid feet come off? Anybody have some 250Ti's?

    In my exerience, what screws in usually screws out, as well.

    Also, again, I don't understand what spike kits are going to do to help the situation on concrete, unless they are REALLY heavy spikes.

    I'm just not getting this, apparently.
    Last edited by Zilch; 09-28-2004 at 12:07 PM.

  13. #43
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    Originally posted by Zilch
    Do we have an exploded view of this or similar product showing how the stupid feet come off? Anybody have some 250Ti's?

    In my exerience, what screws in usually screws out, as well.

    Also, again, I don't understand what spike kits are going to do to help the situation on concrete, unless they are REALLY heavy spikes.

    I'm just not getting this, apparently.
    sorry mate ( head fxxx)
    I suppose I might have to use pliers to extract them if they dont turn out. Here are they spikes I m talking about.
    Attached Images Attached Images  

  14. #44
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    Originally posted by CLASS A
    I suppose I might have to use pliers to extract them if they dont turn out.
    Yup. Sometimes the last few threads are intentionally deformed to prevent them from falling out.

    Cool looking spikes, there!

  15. #45
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    Hi CLASS A

    -,,, the bypass capacitors . I live in the uk and I cant find or source the audiocaps, can you recommend a different make.
    AudioCap is a trade name for a line of audiophile caps that are manufactured by RELIABLE CAPACITORS . Their UK representative is "Audio Com" who can be emailed at audiocom@scotnet.co.uk . Get them to quote some prices to you , including their delivery times . If it seems the caps having to be shipped out from California then consider checking out Parts Connexion who sell Reliables' other 2 lines' of caps. These other 2 lines are "MultiCap" and "RelCap" . Parts Connexion is a Canadain eTailer ( Toronto based ) .

    I'd be very wary of just replacing the bypass caps and expecting instantly positive results. For Instance; The reason I asked if the existing bypass caps were MKT or MKP ( or MKC ) is: If MKT was used , they would be present to blunt the edge or round out the typical "edgy" signature of the electrolytic. The necessity to include MKT would imply to me something about the sonic signature of the Elna(s). MKT , unfortunately doesn't offer great depth or resolution - just a "masked rounded" quality. MKT is Metallized Mylar ( MKP is metallized polypropylene & MKC is metallized polycarbonate ) . If MKP types are present , they would suggest that the DC-biased Elna(s) are not as edgy as most typical electrolytics. That would signal (me) that they might be able to be left intact with just higher quality Film & Foil bypasses shouldering the resolution burden. MKC has qualities that combine attributes from both MKT & MKP .

    Base Caps - replacement

    Space limitations could dictate that you might have to replace your electrolytics with "Metallized Polypropylene" caps . Smaller physical size was the driving force behind the development of all types of "metallized caps". Eliminating the separate foil layer ( by vapour depositing ) metal directly onto one or both surfaces of the plastic dielectric creates a "metallized" dielectric capacitor . Smaller size is the only "real" benefit for this type of cap. All the current cap makers are trying to construct MPP types that sound as good as a plain old "Film & Foil" types .

    - Giskard has already recommended Solen - "Metallized" ( the second post of this thread) and then went on to later mention that the 250ti(s) developer ( from JBL ) has used Solens in his Charge Coupled Networks. Giskard has also stated that what is released to the public isn't necessarily what those who know better will use them themselves. Does more really need to be said on this ? I'd add, that you should stick with the smallest Solens available - the 250 volt variety . Also, I don't believe "Axion" MPP(s) will be much different with these transducers. I'd buy whatever type is most available to you.

    <> Earl K

    ps I wouldn't let all the recent "yellow-flags" over replacing your NP electrolytics deter you from pursuing better resolution.

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