Audio Level Display Devices?

Discussion in 'Archived Threads 2001-2004' started by Steven_MB, Feb 17, 2003.

  1. Steven_MB

    Steven_MB Agent

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    Folks:

    Does anyone know of a device to visually (eg with LEDs or electro-luminesent devices) to display the relative sound levels in a 4.1 or 5.1 system. An old SONY receiver I had did this very effectively with a built in gas-discharge display. The gadget I want would be outboard, and have 4-6 pairs of high Imp. wires to put in parallel with each set of speaker terminals at the receiver output.

    Thanks,

    Steve
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    Hi Steve.

    I've got to warn you that the little flashing LED display that some inexpensive equipment has is actually considered distracting/bad. Many mid-to-high end receivers actually offer options to turn off/dim the front panel display. Not make it jump/flash in time to the sound.

    If you could find such a display device, it would not be in parallel with your speaker wire, it would have to be in series to sense how much power is going to each speaker.

    Are you looking for this for "eye candy" or have you not yet used a SPL meter to level-adjust your speakers?
     
  3. Steven_MB

    Steven_MB Agent

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    Bob:

    Thanks for the reply. Here are some random thoughts.

    1- I don't want eye candy, and that is why I resist building one out of the low cost LED VU meter kits you can find in a web search. What I would really prefer is an all in one mult-channel (low key soft blue) level meter that showed all 4-7 channels in their relative positions in the room (front left, center, front right, etc etc). My old Sony had this built in for 3-4 cahannels and it was really useful.

    2 - Based on my past experience with that old Sony, I have found that such an indicator helped me quickly spot major problems (open coax input lead to one channel, decoder set incorrectly) much more rapidly then listening to the defective sound from the speakers. What I really want is a (low key) spatial sound analyzer and not 4-7 rows of blinking LEDs. (By way of a strained analalogy, TV engineers use vectorscopes for this, hams use multi-needle SWR meters for this.)

    3 - It could go in parallel also to sense power.

    4 - Is some manufacturer listening? The design should not be difficult, although I would start with a special purpose gas discharge display or perhaps an LCD scope.

    Thanks,

    Steve
     
  4. AaronBatiuk

    AaronBatiuk Second Unit

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  5. Bob McElfresh

    Bob McElfresh Producer

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    Back when I was struggling with loose wires caused by Monster "Twist Crimp" bananas, the "Test Tone" button on my remote was a quick and dirty way to check that all 5 speakers were operating.

    Avia/Video Essentials both have warble tones that help you detect wires connected backwards.

    A SPL meter located at the primary listening position can be used with test-tones or Avia/Video Essentials to adjust levels to compenstate for different efficiency speakers, different distances and different speaker angles.

    But all of these are usually the 'set and forget' type of adjustments. They dont change unless you move things around.

    I understand the desire to have something to constantly monitor things, but this is really difficult to do with a DVD-based movie system for this reason: 5 speakers are constantly changing/producing different sounds.

    You cannot simply tell the difference in real time between a setup/wireing problem and quiet passages for a particular channel. And the huge dynamic range possible with a DVD gives production-studios lots of choices. If you got used to the readings on 6 channels for one movie, a different movie could make the system look 'broken' simply because of different levels being sent to different channels.

    (Yes, dont forget you have a 6 channel system with a DVD player, not 5).

    And monitoring the signals to the speakers totally misses the more common problems: the speakers, placement, room interactions. You really should monitor AFTER the speakers, not before to catch these issues.


     
  6. Steven_MB

    Steven_MB Agent

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    Folks:

    Thanks for 'sound advice' and concuuence that 'power' can be measured either way. Here are more random thoughts:

    I'm aware of those chips - they must be the heart of many of those low cost LED VU meter kits I saw in my searching. I'm capable of building with them, but the blinking rows of LEDS is not what I was after. Thinking more about chips, what I really would like is a sound analyzer chip that inputs the 4.1 to 6.1 channels and outputs an NTSC or VGA display signal (to a monitor) showing the relative levels correlated to the speaker positions.

    I concur with the method of RTA using room mikes and calibrated test signals, but that is beyond where I need to be. That does remind me of my old days at Bell Labs. They used to provide the audio setups for the ATT annual meetings (held in big city auditoriums) and used that technique with a room full of frequency and delay equalizers to set up a room. At the end they would have recordings and people say balanced phrases like " Joe took father's shoe bench out; it was waiting on my lawn", while key supervisors with golden ears yelled at technicians - '2 db more here, 10 more ms there, etc etc'. At one meeting, after all was fully balanced and approved by the golden ears, it was discovered that one of the key equalizers was not in the circuit, and had become an audio placebo. This became an urban legend at BTL. I was not there, but knew several of the the guilty golden ears, and felt that it was extremely likely. :))

    Cheers,

    Steve
     

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