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Internet Message Format  |  1992-12-29  |  4.7 KB
  1. Path: sparky!uunet!munnari.oz.au!ariel.ucs.unimelb.EDU.AU!ucsvc.ucs.unimelb.edu.au!lugb!news
  2. Newsgroups: sci.electronics
  3. Subject: Re: Speakers loose tweeters and filter elements
  4. Message-ID: <1992Dec29.033120.530@lugb.latrobe.edu.au>
  5. From: MATGBB@LURE.LATROBE.EDU.AU (BYRNES,Graham)
  6. Date: Tue, 29 Dec 1992 03:31:20 GMT
  7. Sender: news@lugb.latrobe.edu.au (USENET News System)
  8. References: <1517@chorus.chorus.fr>
  9. Organization: La Trobe University
  10. In-Reply-To: ngk@opera.chorus.fr's message of 22 Dec 92 15:42:05 GMT
  11. X-News-Reader: VMS NEWS 1.24
  12. Lines: 104
  13.  
  14.  
  15. In <1517@chorus.chorus.fr> ngk@opera.chorus.fr writes:
  16.  
  17. ..> 
  18. > 
  19. >     Hi netters,
  20. > 
  21. >     I have a pair of JAMO-300 speakers. Their specification is:
  22. > 
  23. >     - 8 Ohm impedance.
  24. >     - 300 W / each.
  25. >     - 4 ways SP system with passive filters.
  26. > 
  27. >     I use them with a Samick SM-6000 Stereo Power Amplifier (250W/channel)
  28. > for dancing parties.
  29. > The problem is that I often have the tweeters and/or some capacitors of the
  30. > filters broken, but never the other elements. I think that the filters for
  31. > the broken tweeters are not well designed or it misses some sort of protection.
  32. > So I'm wondering if any one can tell me how to avoid such a situation for the
  33. > next time I use them (i.e. an active/passive protection circuit or a
  34. > modification in the filters).
  35. > 
  36. >     I give you here the diagram of one speaker system :
  37. > 
  38. > 
  39. >         +-------+------------+----------------+------------------------+
  40. >     |       |            |                |                        |
  41. >         |       |        C1 -+-           C2 -+-                   +---+---+
  42. >         |       |           -+-              -+-                   |       |
  43. >         |      |-|           |                |                  + |       | +
  44. >         |      | |          |-|               +----+             |\+-+   +-+/|
  45. >         |   L1 | |       L2 | |               |    |          T1 | | | T2| | |
  46. >   +     |      | |          | |          C3  -+-  |-|            |/+-+   +-+\|
  47. >   o-----+      |-|          | |              -+-  | |            + |       | +
  48. >                 |           |-|               | L3| |              +---+---+
  49. > To PA           |            |              + |   | |                  |
  50. >   o--+          |            |              |\+-+ |-|                 |-|
  51. >   -  |     +----+       +----+----+      T3 | | |  |               R1 | |
  52. >      |     |    |       |    |    |         |/+-+  |                  |-|
  53. >      |     |    |       |   |-|   |         + |    |                   |
  54. >      |   + |    |     + | L4| |   |           +----+                   |
  55. >      |   |\+-+ -+-C4  |\+-+ | |  -+-C5        |    |                   |
  56. >      | B1| | | -+-    | | | | |  -+-         |-|  |-|              C6 -+-
  57. >      |   |/+-+  |   M1|/+-+ |-|   |        R2| |  | |R3               -+-
  58. >      |   + |    |     + |    |    |          |-|  |-|                  |
  59. >      |     |    |       |    |    |           |    |                   |
  60. >      |     |    |       |    |    |           |    |                   |
  61. >      +-----+----+-------+----+----+-----------+----+-------------------+
  62. > 
  63. > 
  64. >     all capacitors are bipolar chemical capacitors
  65. >     C1 = 10uF, C2 = 3.3uF, C3 = 4.7uF, C4 = 22uF, C5 = 10uF, C6 = 1uF
  66. > 
  67. >     Li are air/iron core selves (inductance) values are unknown.
  68. > 
  69. >     all resistors are winding/carbon 10W resistors.
  70. > 
  71. >     R1 = 12 Ohms, R2 = 10 Ohms, R3 = kind of varistor (ceramic disk form)
  72. > 
  73. >     B1 = bommer, M1 = medium speaker, T3 = medium-tweeter, T1=T2 = tweeters
  74. > 
  75. > 
  76. >     What happened:
  77. > 
  78. >     T3/C3 are broken very often.
  79. >         T1 and T2 eventually.
  80. >         M1/C5 sometimes.
  81. >     B1 never broken.
  82. > 
  83. > 
  84. >     Thank you very much for any advice.
  85. > 
  86. > 
  87. >                 Gia-Khanh Nguyen (ngk@chorus.fr)
  88. > 
  89. Well, my first advice would be to turn down the volume a wee bit. However
  90. there os one other possibility. It could be that the caps are dying first,
  91. which would guarantee the demise of the tweeter(s). Bi-polar electros
  92. have a relatively high dissipation factor, so at the levels you are running
  93. them, it is concievable they are running too hot. Why not replace the smaller
  94. ones with polyester film types? Even 10uF greencaps are cheap compared
  95. to replacing tweeters every week 8-).
  96.  
  97. Next, it could be worth the following: borrow a cro, hook it across your amp
  98. output, and see at what level it really starts to clip. If you are running
  99. from a cd player, you should be able to find out its max output, and determine
  100. at what volume knob position that will cause clipping. Then put a mark saying
  101. "Il est defendu sur peine d'assasination de faire tourner l'attenuateur au-dela
  102. de ce point".
  103.  
  104. By the way, do you have any hearing left? any neighbours?
  105. Bon chance,
  106. Graham
  107. > 
  108. > 
  109. > 
  110. > 
  111. > 
  112. > 
  113. > 
  114. > 
  115. > 
  116. > 
  117. > 
  118.