Speaker volume control

Discussion in 'Electronic Basics' started by Andrew Howard, Sep 24, 2003.

  1. What is the best way of controlling a speaker's volume directly? (not
    adjusting the amp). I have a single 8ohm speaker, and I have tried a
    variable resistor, but the volume decreases too quickly. Any suggestions?

    Andrew Howard
     
    Andrew Howard, Sep 24, 2003
    #1
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  2. Andrew Howard

    John G Guest

    Get a Variable resistor about 50 ohms.
    Probably very hard to find though.
    An nderstanding of OHMS law would be a great advantage for the future.
    --
    John G

    Wot's Your Real Problem?

    "Andrew Howard" <> wrote in message
    news:qd8cb.120052$...
    > What is the best way of controlling a speaker's volume directly? (not
    > adjusting the amp). I have a single 8ohm speaker, and I have tried a
    > variable resistor, but the volume decreases too quickly. Any suggestions?
    >
    > Andrew Howard
    >
    >
     
    John G, Sep 24, 2003
    #2
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  3. Andrew Howard wrote:
    >
    > What is the best way of controlling a speaker's volume directly? (not
    > adjusting the amp). I have a single 8ohm speaker, and I have tried a
    > variable resistor, but the volume decreases too quickly. Any suggestions?
    >
    > Andrew Howard


    You need an L-Pad.
    --


    Michael A. Terrell
    Central Florida
     
    Michael A. Terrell, Sep 24, 2003
    #3
  4. Stepan Novotill, Sep 24, 2003
    #4
  5. Andrew Howard

    Baphomet Guest

    "Andrew Howard" <> wrote in message
    news:qd8cb.120052$...
    > What is the best way of controlling a speaker's volume directly? (not
    > adjusting the amp). I have a single 8ohm speaker, and I have tried a
    > variable resistor, but the volume decreases too quickly. Any suggestions?


    You need either an L or a T pad which Radio Schlock sells. An L pad consists
    of two ganged rheostats and the T pad three. This is to provide a constant
    impedance as seen by the source, load or both. Additionally, a regular one
    section variable resistor will cause serious distortion.
     
    Baphomet, Sep 24, 2003
    #5
  6. Andrew Howard

    JeffM Guest

    Additionally, potentiometers come in 2 tapers: linear and logarithmic.

    The human ear's response to sound intensity is a logarithmic function
    so that's the taper required for those applications.

    There's 1 caveat: a _pad_ needs to have a REVERSE logarithmic taper.
    As has been said, BUY a ready-made

    L L PPPPPPPP AA DDDDDDD
    L L PPPPPPPPP AA DDDDDDDDD
    L L PP PP AA AA DD DD
    L L PP PP AA AA DD DD
    L L ===== PPPPPPPPP AA AA DD DD
    L L ===== PPPPPPPP AA AA DD DD
    L L PP AAAAAAAAA DD DD
    L L PP AA AA DD DD
    L LLLLLLL PP AA AA DDDDDDDDD
    LLLLLLLLL PP AA AA DDDDDDDD
     
    JeffM, Sep 25, 2003
    #6
  7. I used an "L" pad from the Shack. I believe it was a stereo volume control.
    Large rheostat that would mount in a standard wall plate. Works Great!
     
    Baronvonrex420, Sep 26, 2003
    #7
  8. Andrew Howard

    BobGardner Guest

    > This is to provide a constant
    >impedance as seen by the source, load or both.

    The speaker doesnt care what the source impedance is, and the amp doesnt care
    what the load impedance is, so an L pad is unneccessary in this case.

    > Additionally, a regular one
    >section variable resistor will cause serious distortion.

    This is incorrect. If the amp is clipping, it will sound fuzzy, but not because
    the amp is operating into a hi impedance load, but because its turned up too
    loud. Regular old resistor will attenuate the signal.
     
    BobGardner, Oct 22, 2003
    #8
  9. Andrew Howard

    John Fortier Guest

    "BobGardner" <> wrote in message
    news:...
    > > This is to provide a constant
    > >impedance as seen by the source, load or both.

    > The speaker doesnt care what the source impedance is, and the amp doesnt

    care
    > what the load impedance is, so an L pad is unneccessary in this case.
    >


    I can't find the original thread to which this re. refers, but I have to say
    that this is incorrect. The speaker and amp output impedances should be
    matched for greatest power transfer and, failing that, the impedance of the
    speaker should be greater than that of the amp output, to avoid distortion
    in the output stage of the amp. Since the nominal (very nominal) impedance
    of a speaker is 8 ohms, the amplifier output impedance should be 8 ohms or
    lower. Since most amplifiers are designed to drive a nominal 8 ohm load,
    providing them with such a load avoids distortions.

    An L pad can provide attenuation between the amplifier output and the
    speaker and provide a correct load for the amplifier. However, for each
    volume setting you will need different resistor values.
    http://www.goldpt.com/schm_ml.html shows a circuit diagram of a switchable
    attenuator. If you click on the DIY reference box, you will get access to a
    whole lot more info as well.

    > > Additionally, a regular one
    > >section variable resistor will cause serious distortion.

    > This is incorrect. If the amp is clipping, it will sound fuzzy, but not

    because
    > the amp is operating into a hi impedance load, but because its turned up

    too
    > loud. Regular old resistor will attenuate the signal.
    >


    Depending on the design of the output stage, the use of "regular old
    resistors" can cause distortion. If the resistor in question is in the
    hundreds of ohms range, which would be necessary to reduce the volume of an
    8 ohm speaker by 40 or so dB, then the amplifier will clip at much lower
    output levels than it would if it were driving its design load. Presumably
    the original intention was to have a volume control between amp and speaker,
    not to have to adjust the amp volume.

    A switched L attenuator will avoid these problems and provide volume control
    between the amp and speaker.

    John
     
    John Fortier, Oct 23, 2003
    #9
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