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Thread: renewing yamaha ns 20 speakers

  1. #31
    Join Date: Dec 2018

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    I'm arsenico.

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    Quote Originally Posted by Macca View Post
    The speakers already have a tweeter so I don't know what gains you are hoping to make by adding another. From the response you show it doesn't extend much higher than 20Khz anyway. Usually you would look to roll in a supertweeter where the existing tweeter gives out. Do you know the upper FR of the existing tweeter? I guess if it is quite low(15Khz) say then it might be worth trying the supertweeter. Otherwise you are just doubling up on what is there already, you'll get cancellation, reinforcement, comb filter effects. All a bit random it seems to me.
    i agree with you,

    my first idea was simply to replace the actual tweeter, that is not an original yamaha JA0505 as it should be, you know these 50 year old things, the present tweeter is a Phillips AD0160/T8, for which i found an experimental curve like this:



    so this means that this phillips tweeter gives up at 18.000Hz, and the sensitivity is aorund 92dB, and not very flat neither

    once this is said my alternatives would be:

    1- to use the yamaha JA0506 it as a supertweeter keeping the phillips, and then where to cut the supertweeter frec. 8000Hz. ? more ?

    2- or get rid of the phillips and put this yamaha JA0506 tweeter in its place, in this case i will be using the existing crossover with its high pass filter at 6000Hz and adding an L-Pad attenuator to attenuate from the 115dB given by the tweeter and accomodate to the rest of the speaker´s setup (woofer and squawker)

    should this be better ?

    thank you

  2. #32
    Macca's Avatar
    Macca is offline Moderator and lover of technical papers
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    I'm Martin.

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    If I were you I would go for option 2 - I didn't realise the existing tweeters were not original.

    You might find you don't need the attenuator at all, I'd try it without first as it makes things a lot simpler.
    Martin



    Current Lash Up:

    Technics SLP1200 CD Player * Nelson Pass DCB1 Pre amp / Krell KSA50S Power amp * JM Lab Electra 926 loudspeakers *


    'You fool! To think that your ape-brain could contain the full knowledge of the Krell!'

  3. #33
    Join Date: Apr 2012

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    I'm Geoff.

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    I hadn't recognised the Philips tweeter and should have done, because I experimented with a couple of pairs of these years ago. They are the same model that Goodmans employed in their SL series speakers. Unfortunately, I found them rather brash sounding and moved to using lovely smooth sounding Audax silk dome units instead. Possibly worth considering here.
    "when common sense, logic and plausibility are excluded. All that remain are foolishness and lies"

  4. #34
    Join Date: Dec 2018

    Location: bilbao

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    I'm arsenico.

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    Quote Originally Posted by Macca View Post
    If I were you I would go for option 2 - I didn't realise the existing tweeters were not original.

    You might find you don't need the attenuator at all, I'd try it without first as it makes things a lot simpler.
    ok, so i went option 2 yesterday,

    first i prepared an L-pad attenuator of 8dB as the sensitivity gap is 115-92 = 23dB and i should attenuate around half that value, with the available resistors i could make for 8dB,...








    so armed with that i made the connection, first without L-pad



    must say that the difference is mindblowing, exceptional tweeter, pristine clean rich high tones,...but toooooo loud !

    so i should install the L-pad

    will report later...

    thanks

  5. #35
    Join Date: Dec 2018

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    today, waiting for the L-pad to arrive
    i have prepared the base to seat the tweeters


































  6. #36
    Join Date: Dec 2018

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    well

    attenuators have not arrived yet, so tweeters are being managed through the amplifier,

    but i am still making some tuning

    the construction of this speakers is apparently odd when compared to the ones that you can see in the catalogues, drivers in this pair are installed in the covers, nevertheless they seem to be absolutely originals

    so two goals:

    1- check the squawkers, in my case one is a yamaha original, and the other is a phillips, it is clear that they sound different, right now i prefer the yamaha over the phillips, but i have a pair of saba greencones to check, and i do not have a second yamaha

    2- build a support for the squawkers and an idependent cover

  7. #37
    Join Date: Dec 2018

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    first step is to build a support, same style as the one present in the yamaha speakers





















    once prepared and painted in black, we start replacing the squawkers, the yamaha goes from the cover to the support, and the phillips is replaced by the saba, strong fixing, and absorbent adhesive tape


  8. #38
    Join Date: Dec 2018

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    installed firmly and arranged the cables

    was able to check the two speakers carefully

    woofer the big ear shaped yamaha, squeaker one yamaha other saba, tweeters as yamaha










    pour some jazz music over them, and asked other people about the black or the green cone

    answer was clear: the green saba was clearer, brighter, and nicer

  9. #39
    Join Date: Dec 2018

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    love how they look without a cover, you can see them there and they are beautiful enough to fill the room

    ...but i bought a piece of nice fabrik,....and i wanted to see how they will look dressed with it

  10. #40
    Join Date: Dec 2018

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    first the frame









    even placed the yamaha plate, that by the way is made of brass



    and here they are, splendid in my opinion


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