View source for The Link 09 Electronics

<pre> electronics
£££££££££££££


    by GURU/TSR











       in this montly chapter, i will
be giving you ideas and theory for
useful electronic circuits.

      for those of you who don't know
a capactior from a potentiometer from a
pile of shit, return to the menu as this
is NOT your chapter



  this month i will show you how to make
a simple crossover network for speakers

   a crossover network is a circuit that
acts as a filter. it filters out HIGHER
frequency signals from LOWER frequnecy
signals and send them off to the correct
speaker ie. high freq. to tweeters, low
freq. to woofers.

     crossovers are used so as to
increase to performance of speakers,
especially at higher volumes.

    only two types of components are
needed for most crossovers, capacitors
and coils.

    a capacitor in series with a tweeter
will filter out low freq. signals

    a coil in series with a woofer will
filter out high freq. signals

    non-polarised, non-electrolytic
capacitors are recomended for this type
of work so greencaps, paper caps, or
even bi-polar electros are usable.


   coils.... thats another story, i have
searched the catalogues of many major
electronics distributors and have only
found one that sells coils - JAYCAR
ELECTRONICS - , although they are rather
expensive at around $5.50 each.

     if you prefer, you can get old
power transformers, and experiment with
using the secondary winding as straight
out coils (thats all they are after all)


     or, you can wind your own.

  about 210 turns on an air cored wooded
rod (16mm long, 12mm diam.) will give an
inductance of 0.5 MILLIhenrys

  as above but with 300 turns will give
you about 1.0 MILLIhenrys

   you can also use this formula to work
out sizes etc.:

                2 2
          l=0.2a n /(3a+9b+10c)

      where:

     l=inductance in MICROhenries
    a=average diameter of coil in inches
    b=length of the coil in inches
 c=radial depth of the winding in inches
    n= total turns of wire

     OFF THE SUBJECT OF COILS


the basic circuit diagram of a crossover


                        ##
     """"""[][][]"";""""##"""""""
     #     coil    !    ##      #tweeter
!+   #             !    cap.    #   +!
! #""#           input          #""# !
! #  #                          #  # !
! #  #             !            #  # !
! #""#             !            #""# !
!+   """""""""""""";"""""""""""""   +!
woofer



   the following table will show you
   what coil and cap. to use for certain
  cut-off frequencies (depending on
   the characteristics of your speakers)


 for 8 ohm


hz      coil(mh)      hz      cap(uf)

250      4.0         2000     10.0
500      2.0         3000     6.8
750      1.47        4000     4.7
1000     1.0         5000     4.4
2000     0.47


      if you are using a 4 ohm system,
half the coil's value and double the
cap's value.





     if you need more information
         (proper diagrams), on
       this or any other topics

ie    reset switches
      parallel copiers
      old old computers (pre- c64)

         then please contact me


    GURU/TSR
                     -code swap
 xxxxxxxxxxxxxxx     -code letters
 teralba nsw 2284    -elect. swap
    australia        -elect. letters
                     -elect. info




       THIS CHAPTER WAS NOT BORING

       AND WAS NOT A WASTE OF TIME



                        fire if you dare</pre>