is it possible to build....

Discussion in 'Home Theater Projects' started by Anthony_I, Nov 4, 2003.

  1. Anthony_I

    Anthony_I Stunt Coordinator

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    a VU meter type thing ( i think thats what there called) for my sub, so that it will show what the levels are at and if it is clipping???? It would make it easier to adjust the volume at certain times and keep it at a reasonable level without clipping.

    I dont even know if im making sense but maybe someone will understand. [​IMG]
     
  2. Allen Ross

    Allen Ross Supporting Actor

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    is it possible, yeah sure, do i know how to do it or where to look nope, but.

    This Xmas me a my buddy are going to build a pair of 31 band Spectrum Analyzers with LEDS with line level inputs. Should be rather interesting if we can get it done.
     
  3. ThomasW

    ThomasW Cinematographer

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    Subs don't clip, amps do that.

    The only real world use for VU meters is for their entertainment value (aka light show). They are useless for getting accurate information.

    There are L.E.D. output level meter kits available. They won't tell you anything, but the instantaneous peaks of amplifier power. Several companies sell these kits, a google search should help you located them

    IOW, this is something that you need to learn to 'hear'. Amplifier clipping results in distorted sound. So if what you're hearing isn't 'clear', but is instead muffled/distorted or doesn't sound 'natural' turn down the amp.
     
  4. Dave Milne

    Dave Milne Supporting Actor

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    As usual, Thomas is correct... although I wouldn't have been quite so emphatic. I personally find amplifier clip indicators very useful for several reasons: 1. I'm not confident that I can always hear and react to minor overload before putting $1000 tweeters in jeopardy. 2. Overload on sub amps is often difficult to detect - especially with bandpass alignments and high Le drivers; the odd-order harmonics get filtered down to pretty low levels. 3. If I'm listening to something relatively unfamiliar and I see the clip light momentarily flash on, I can run for the volume control because there could be even louder passages coming.

    But, as Thomas noted, VU meters are a very inaccurate way to indicate clipping. Their logarigthmic display by nature means that the difference between, say, 70 watts and 100 watts on a 100W amp is only 1 dB!

    A "real" clipping indicator is much more effective. There are several ways to do this such as a comparator circuit to indicate when the amplifier output swings close to the supply rails or a "distortion monitor" that compares input waveform to output and alerts when a preset difference is detected. Retrofitting either of these to an existing amp will require fairly thorough knowledge of the particular amplifier design as well as electronics in general.
     
  5. RichardHOS

    RichardHOS Second Unit

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    I believe that Rod Elliot has a project on his site that addresses this.
     
  6. Jeffrey Stanton

    Jeffrey Stanton Stunt Coordinator

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    VU-meters??

    I'm using a Behringer UltraCurve (DSP-8024) on my subs that has neat LCD bar graphs for each channel for input or output. It also has a red light clip indicator that comes on in that event. Essentially a VU-meter...

    The BFD I am also using on my two subs also has LED banks of lights for input/output indicators, the top bank of lights being red for "clip". Not as close to a "meter" as the Ultra-Curve, but it does the same job as a meter.

    Get either of these to EQ your sub and you'll have your "VU meter" readings plus all kinds of EQ capability...

    Two birds with one stone....

    They're both relatively cheap about 180 and 110 bucks respectively. The UltraCurve can RTA and auto-eq your system with an ECM8000 mic or equivalent (about $30 bucks).
    The BFD will not RTA/auto-eq, you need a SPL meter and test tone disc and figure your own parametric filters.
     
  7. Anthony_I

    Anthony_I Stunt Coordinator

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    Thats American pricing Jeff, it is $229 for the BFD (that i dont have...but i will buy one eventually)
     
  8. Mark gas

    Mark gas Second Unit

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    Go to termpro.com and do a search there is a post there on how to make some using led's.
     

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