From: ngk@opera.chorus.fr (Gia-Khanh Nguyen)
Newsgroups: sci.electronics
Subject: Speakers loose tweeters and filter elements
Keywords: Audio, PA, Speaker
Date: 22 Dec 92 15:42:05 GMT
Reply-To: ngk@opera.chorus.fr (Gia-Khanh Nguyen)
Organization: Chorus systemes, Saint Quentin en Yvelines, France



	Hi netters,

	I have a pair of JAMO-300 speakers. Their specification is:

	- 8 Ohm impedance.
	- 300 W / each.
	- 4 ways SP system with passive filters.

	I use them with a Samick SM-6000 Stereo Power Amplifier (250W/channel)
for dancing parties.
The problem is that I often have the tweeters and/or some capacitors of the
filters broken, but never the other elements. I think that the filters for
the broken tweeters are not well designed or it misses some sort of protection.
So I'm wondering if any one can tell me how to avoid such a situation for the
next time I use them (i.e. an active/passive protection circuit or a
modification in the filters).

	I give you here the diagram of one speaker system :


        +-------+------------+----------------+------------------------+
	|       |            |                |                        |
        |       |        C1 -+-           C2 -+-                   +---+---+
        |       |           -+-              -+-                   |       |
        |      |-|           |                |                  + |       | +
        |      | |          |-|               +----+             |\+-+   +-+/|
        |   L1 | |       L2 | |               |    |          T1 | | | T2| | |
  +     |      | |          | |          C3  -+-  |-|            |/+-+   +-+\|
  o-----+      |-|          | |              -+-  | |            + |       | +
                |           |-|               | L3| |              +---+---+
To PA           |            |              + |   | |                  |
  o--+          |            |              |\+-+ |-|                 |-|
  -  |     +----+       +----+----+      T3 | | |  |               R1 | |
     |     |    |       |    |    |         |/+-+  |                  |-|
     |     |    |       |   |-|   |         + |    |                   |
     |   + |    |     + | L4| |   |           +----+                   |
     |   |\+-+ -+-C4  |\+-+ | |  -+-C5        |    |                   |
     | B1| | | -+-    | | | | |  -+-         |-|  |-|              C6 -+-
     |   |/+-+  |   M1|/+-+ |-|   |        R2| |  | |R3               -+-
     |   + |    |     + |    |    |          |-|  |-|                  |
     |     |    |       |    |    |           |    |                   |
     |     |    |       |    |    |           |    |                   |
     +-----+----+-------+----+----+-----------+----+-------------------+


	all capacitors are bipolar chemical capacitors
	C1 = 10uF, C2 = 3.3uF, C3 = 4.7uF, C4 = 22uF, C5 = 10uF, C6 = 1uF

	Li are air/iron core selves (inductance) values are unknown.

	all resistors are winding/carbon 10W resistors.

	R1 = 12 Ohms, R2 = 10 Ohms, R3 = kind of varistor (ceramic disk form)

	B1 = bommer, M1 = medium speaker, T3 = medium-tweeter, T1=T2 = tweeters


	What happened:

	T3/C3 are broken very often.
        T1 and T2 eventually.
        M1/C5 sometimes.
	B1 never broken.


	Thank you very much for any advice.


				Gia-Khanh Nguyen (ngk@chorus.fr)













Newsgroups: sci.electronics