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Thread: Am I building these correctly - JBL 4355 Crossovers

  1. #46
    Senior Member martin2395's Avatar
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    Still I can't really get used to it's sound atm, much more open but still somehow grainy, even with the "2 Radian phragm so it must be something else that causes this.
    I decided to give my BSS FDS-360 another major overhaul, it already had it's input opamps replaced from NE5532's with LM4562NA's but now I took the plunge and will replace all of the remaining (LF353) opamps with OPA2134PA.

    Hell, this will be the most expensive FDS360 ever
    I have all the schematics and see if I can replace some electrolytics with fancy stuff like Nichocon Muse. They are all small values so it won't cost a fortune.

  2. #47
    Senior Member martin2395's Avatar
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    By the way, has anyone tried bypass caps in JBL networks, for example the 0.01uF Theta caps?

  3. #48
    Senior Member martin2395's Avatar
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    Just a small question regarding the impedance flattening part (coil+resistor), do they have any influence on sound quality or can I use cheap(er) parts for it?

  4. #49
    Senior Member ivica's Avatar
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    Quote Originally Posted by martin2395 View Post

    Still I can't really get used to it's sound atm, much more open but still somehow grainy, even with the "2 Radian phragm so it must be something else that causes this.
    I decided to give my BSS FDS-360 another major overhaul, it already had it's input opamps replaced from NE5532's with LM4562NA's but now I took the plunge and will replace all of the remaining (LF353) opamps with OPA2134PA.

    Hell, this will be the most expensive FDS360 ever
    I have all the schematics and see if I can replace some electrolytics with fancy stuff like Nichocon Muse. They are all small values so it won't cost a fortune.
    Hi martin2395,

    how do you know what type of IC to replace with other type or brand?

    regards
    ivica

  5. #50
    Senior Member martin2395's Avatar
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    I got tips from guys who know more than I do, I also have the complete schematics and documentation for the 360

    Still, I fully tweaked the FDS with OPA's and Nichicon Muse KZ and then I bought the Bryston 10B, it trashed the BSS to no end

  6. #51
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    Quote Originally Posted by martin2395 View Post
    By the way, has anyone tried bypass caps in JBL networks, for example the 0.01uF Theta caps?
    The 3155 is factory equipped with 10nF bypass caps.

  7. #52
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    Quote Originally Posted by martin2395 View Post
    Just a small question regarding the impedance flattening part (coil+resistor), do they have any influence on sound quality or can I use cheap(er) parts for it?
    They are a part of the filtering network and have no clue that they are only impedance correctors . If you are into boutique parts for your filter, there's no reason to stop here.

  8. #53
    Senior Member martin2395's Avatar
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    There is a reason, my budget!

    Beucase there are no 2.0uF Jantzens I must use 4x1.0uF (2x1 + 2x1) and the cost is getting outrageous.
    For two 3155's I'd need 12x 1.0uF, 4x0.33uF and 4x3.30uF - €220 euros including shipping
    I'm not even looking at the 15 and 18uF one's....

    Also I'm really considering stopping with CC because of the price of good caps, if I won't use CC I could get away with a single 1uF cap in place of 4...

  9. #54
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    For further clarification:



    The LEAP schematic is correct. Ignore R10, R11, R12 and R13, R14, R15. They were used to simulate L-Pads at 50% power reduction. A person would use L-Pads instead. 16-ohm L-Pad on the 2441 and 8 ohm L-Pad on the 2405. The coils are standard Solen coils with DCR values lower then 0.5 ohm. The capacitors are Solen PB capacitors, the smaller sized poly caps. If I remember correctly, the PA caps were the larger, higher voltage caps.

    Unfortunately this LEAP schematic doesn't show exactly how to bias capacitors, that knowledge is assumed based on many past discussions and posted schematics. One can use either the battery method as shown in many JBL schematics or the diode method as shown in the 4365 schematic.

  10. #55
    Senior Member martin2395's Avatar
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    In a well dampened room they 'll do without the L-pads but YMMV.

    Also - save money for good caps, I'm paying the price for buying the cheap crosscaps.
    Something like Mundorf S/G/O or maybe some soviet-era PIO's should be miles better.

  11. #56
    Senior Member martin2395's Avatar
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    Very, very big thanks to member JBLPRO for noticing and letting me know that my hand drawn schematic of the 2441 HF section has a major flaw - the .47mH coil should we wired in series, not in parallel

    Now I have to fix both networks

  12. #57
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    Quote Originally Posted by martin2395 View Post
    In a well dampened room they 'll do without the L-pads but YMMV.

    Also - save money for good caps, I'm paying the price for buying the cheap crosscaps.
    Something like Mundorf S/G/O or maybe some soviet-era PIO's should be miles better.
    What caps did you use? I ordered Solen's all the way around but I am not at the listening stage yet. G Timbers recommends Solen's so i figured that would be a good choice.

    mk

  13. #58
    Senior Member martin2395's Avatar
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    I started with Jantzen crosscap (apparantly Tony Gee rates these higher than all the SCR's) but they were disappointing - harsh and grainy.
    Now I have the white Audyn Plus combined with Mundorf Supreme, only the 2123H is still running on 4x18uF Crosscaps because of cost and the sheer size of the Audyn caps.
    I'm also considering adding MKP1837 on those Crossaps to see if they make any difference on the midwoofer.

    Next step will be the resistors, I will be replacing the green Jantzens with Mundorf Mresist supremes.

  14. #59
    Senior Member martin2395's Avatar
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    Still happy with the 3155's. I changed the HF amp to a tube OTL and never been happier. I've heard many systems so far but I'd never trade my JBL's for anything else, expect maybe the DD series or some high end custom TAD's.

    However I still don't understand the need for a highpass for the 3155 (the need for lowpass for 2235H is obvious as it's directly coupled to the amp) as it makes you use an active crossover and a passive one behind it. or am I doing it wrong the whole time?

  15. #60
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    Quote Originally Posted by Odd View Post
    This is easier to understand.

    Quote Originally Posted by martin2395 View Post
    Is the overall resistance of the coil and resistor 7,5ohms together?
    Or do I have to use a 7,5ohms resistor in addition to the coil? If so, whatīs the resistance of these coils?

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