Posted on Monday, 2nd January 2012 by Auw Jimmy

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My wife knows and supports my hobby in audio. I think she even knows almost all of my expenses. Well, ‘almost’ means maybe there are some that she doesn’t care or aware of – not my intention to hide from her :) .

Once upon a time, when we were on her mother’s living room, I stumbled upon an audio system used there. It was quite old and sounded ‘ultimately’ bad. She jokingly asked me how do I rate this system. Honestly I said, maybe around 20 from 100 scale. Well, it’s true. Even maybe 20 was still slightly over rated. Then she challenged to improve it. After checking them for few minutes, I decided to give further examination as the condition was ‘terrible’. OK, I could bring this home for some new year’s fun. Then the adventure begun…

Now, let’s start with the speaker. The speaker is Mission 762. Quite good on its era (20 years back). But now, it sounds so bad. The woofer seems fine, but the tweeter I think already running out of his life. Too much noises and ‘too smooth’ (means no treble or detail) .

Then the second issue is the receiver. It’s an old Marantz PM400AVK. I check elsewhere that this should be for Japanese market. First suspect is the volume control problem which produces some breaking voice. But will see.

Inside the Mission tweeter. Dusty for sure, but that’s not the problem.

The original crossover. Some bipolar capacitor, Tesla resistor, and two inductors. They form 2nd order for the high pass and 1st order for the low pass. As simple as you can be.

Will see what I can improve from this. Making them higher score over 50 would be an amazing job (as currently I rate them only 20).

One note to be taken is, we will not see expensive stuff on this upgrade (something which is unlikely for my project). So the target is economical spending, but reasonable result. Quite challenging, huh?




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Posted in DIY Audio, Personal | Comments (7)

7 Responses to “A New Year’s Challenge”

  1. aphinx Says:
    January 3rd, 2012 at 08:55

    clarity caps sa buat gantiin bipolar caps kayaknya bakal improve signifikan dengan harga relatif ekonomis ….. r-nya kelihatan cukup oke ….. tapi, kalo mau l-nya pake air-core, jatuhnya bisa mahal juga ….. hehehehehehe …..



  2. Auw Jimmy Says:
    January 3rd, 2012 at 10:19

    Clarity Caps dari yang saya sudah kenal karakternya sih kurang cocok ya… Dan juga mungkin kurang ekonomis dan kurang mudah didapat.

    R Tesla juga karakternya enggak gitu cocok saya tuh he he he. Walaupun nilainya masih valid sih setelah saya test.

    L-nya tidak harus air core, karena dengan pertimbangan saya tidak butuh vocal yang terlalu manis dan ini untuk woofer 8″ koq. Sedikit efek distorsi dari ferrite mestinya acceptable.

    Jadi arah mod ini rasanya akan sangat sulit dipahami kalo pendekatannya text book. Harus agak sedikit “out of the box” atau mungkin “out of the brain”. Namanya juga proyek iseng. Sebenarnya saya sudah selesai mod-nya sih, tapi belum sempet upload he he he.

    Thanks atas sarannya bro :)



  3. Jimmy’s Junkyard » Blog Archive » New Year’s Challenge Continues [Mission 762] Says:
    January 4th, 2012 at 00:20

    [...] on Wednesday, 4th January 2012 by Auw Jimmy If you have read this previous article, probably you got my point when reading this one. Now, I’m doing the [...]



  4. Anonymous Says:
    January 11th, 2012 at 13:50

    just simply change the bi bolar cap to film cap, but u need to measure the uF of biboplar and not just base on the uf write on the cap. as a 4uf bipolar can easily give reall reading ~4.5-4.8uf

    then twisted the wire, put some absorber material and sand bag … they will be enough to see significant changes, no point to spend too much on that.



  5. Auw Jimmy Says:
    January 11th, 2012 at 14:22

    Hi,
    Not all film caps sounds the same.

    Good caps will have exact value as written. Definitely you will not use 4.8uF value with a caps written at 4uF.

    Thanks.



  6. James Says:
    April 8th, 2013 at 03:13

    I have a pair of these but cannot find the cones for them, Do you still have the originals, if so are they in decent condition and can i buy them from you.

    I am in the uk.

    James



  7. Auw Jimmy Says:
    April 9th, 2013 at 09:10

    Hi James,
    Unfortunately, I don’t have it.
    Thanks.



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