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Ext spkr for VHF Radio

Discussion in 'Boat Electronics' started by Bill Andersen, Dec 18, 2003.

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  1. I want to use the two stereo speakers of my boats AM/FM/Cassette Player for
    my VHF radio. I wired both radios to a Double Pole Double Throw switch. The
    AM/FM/Cassette Player works, but the VHF radio volume is so low I can barely
    hear it.
    The specifications for both radios state 4-8 ohm speakers. The
    AM/FM/Cassette Player states 14 watts RMS maximum stereo power, the VHF
    radio states 4 watts audio output.
    Is there anyway I can use the stereo speakers for both radios? If not, will
    the VHF radio have enough power to hear it if I add two of the mini-speakers
    designed for it in the rear cockpit area?
  2. Larry

    Larry Guest

    I'm not sure how you wired it as the VHF radio most likely has a single
    speaker output and the stereo has two outputs (right and left) and may
    share a common ground. You can use the stereo speakers for both radios,
    but you should turn off whichever radio is not connected to the speakers to
    avoid blowing out the audio section.

    If it were me, I'd add a SINGLE remote speaker to the VHF radio, making
    sure it is plugged into a connection designed to power a speaker.
  3. The stereo has a separate output and ground for each speaker.
    The VHF has a built-in speaker and a outlet for an external speaker jack.
    The DPDT switch has 6 posts, I cut one of the wires from the stereo to each
    speaker and ran them to the left and center posts of the switch so, when the
    switch is to the left, the stereo is connected to the speakers.
    I ran a wire from the external speaker jack of the VHF to the right and
    center posts of the switch so, when the switch is to the right, the VHF is
    connected to the speakers.
  4. Gary Schafer

    Gary Schafer Guest


    It sounds like your wiring is wrong. Without your switch connected,
    First check to make sure that the common wire on the stereo is really
    at ground on the radio.

    Next check to see that one of the wires out of the marine radio is at
    ground on the radio.

    If both have those leads grounded on each unit then you can do what
    you want with the double pole double throw switch.

    Leave the common speaker leads grounded to the common lead on the
    stereo. Place each of the other speaker leads on the CENTER poles of
    the switch. (one on each pole) On one end of the switch place each of
    the leads from the stereo. Now when the switch is in one position the
    speakers will be hooked as they normally were to the stereo. In the
    other position of the switch one lead of each speaker will be
    disconnected from the stereo. In that position of the switch the
    speakers will now be hooked to the opposite end of the switch.

    You can hook the ungrounded lead of the marine radio to one of the
    poles on the opposite end of the switch from where the stereo radio is
    The grounded speaker lead from the marine radio would get connected to
    the grounded connection of the stereo and speaker ground junction.

    Now with the switch in the marine radio position the stereo is
    disconnected on both channels and the marine radio is connected to ONE
    of the speakers. If you want both of the speakers to be connected to
    the marine radio place a jumper wire between the two terminals on the
    end of the switch that the marine radio is connected to. (one of those
    would have been the only unused pole on the switch)


  5. Thanks, Gary. I thought that was how I wired it. I'll print your post and
    take it with me the next time I have a chance to tinker with the speakers.

  6. parallel.. I'm trying to remember what that is.
    But, only one radio powers the speakers at a time, that's why I used a DPDT
  7. I dunno but taking the "Kiss" theory, it might be best to just have another
    extention speaker for the radio ??
    Not like it will break the bank and you dont have to remember to throw the
    A small 'coms" type speaker would do it and you would not be compromising
    either system.
  8. Larry

    Larry Guest

    Absolutely! It's really the best way to do it and not at all expensive.
  9. Another solution to this problem is to use a Dual Voicecoil Speaker.
    Motorola built a very nice Marine VHF Radio years ago called a MODAR
    Triton that used one of these in the Bridge to Bridge version. This
    radio has two receivers and both drive a single speaker with two
    individual voicecoils. Worked very slick. I have a number of the
    speakers that I salvaged from these as the radio's died, and use them
    just for this purpose. I have seen a few speakers with similar setups
    in Jameco on occasion.

    Bruce in alaska
  10. Harry Krause

    Harry Krause Guest

    But how does it handle those cassettes???
  11. The switch I bought is called DPDT. It has six posts: 2 left, 2 center, 2
    I intended to use the two on the left side for the left and right stereo
    channels and the two on the right side for the VHF (jumpered to both posts).
    The center posts are for the grounds of both speakers.
    I know I can add a separate speaker for the VHF radio. My idea was to use
    the existing stereo speakers for the VHF radio with the option of switching
    them back to the stereo.
    I sometimes place my hand held radio in a holder mounted on the engine
    compartment. That's OK, but uses up the batteries.
  12. Not quite right...

    Connect the "hot" wires from the stereo to the two left terminal, the
    "hot" wires to the two speakers to the center terminals, and the "hot"
    wire from the VHF to the two right terminals. The ground wires from
    speakers, stereo, and VHF should all be connected together, and
    connected to the switch.

    This assumes that one side of each stereo speaker is really grounded -
    if this is no so, you need a four pole switch, and will need to switch
    both sides of both speakers.
  13. Larry

    Larry Guest

    That assumes that both devices use ground as the other conductor. If your
    stereo does not use ground as the second speaker terminal, you will have
    problems. Really, this is not a good idea, as someone might turn on the
    stereo, not hear anything and turn it up which can damage the outputs.
    Same thing can happen to the VHF.

    A second speaker is cheap and safer!

    As for mounting a handheld on the console, why not just get a 12 volt
    adapter for it?
  14. That connection could destroy Your amplifiers..

    To be on the safe side You need a 4-pole 2-position switch (4+4+4=12

  15. Oops - the ground wires should NOT be connected to the switch!
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