Oddest Level Problem

Discussion in 'Archived Threads 2001-2004' started by Bob U, Apr 19, 2002.

  1. Bob U

    Bob U Stunt Coordinator

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    Hi Folks,

    I really don't expect an answer to this one, but thought I would try. I'm baffled.

    I sold my subwoofers and I'm waiting on a pair of SVS's to arrive. In the mean time, I moved my mains about 6" forward and 6" in toward the center of the room to make room for the SVS's. I also bought new, heavier sand filled stands for the mains (just to mention EVERY change). I then turned the LFE off on my Parasound AVC-1800 pre/proc and set the mains to large in the interim.

    Since then, every source has to be played about 10dB louder to get the same volume level I had previously. In other words, where I might listen to a DVD at a comfortable level at -12 on the pre/proc, the same level is now at about -2. This includes putting a test tone thorugh the system by playing a Stryke test disc at 1kHz on my DVD and measuring with a Radio Shack SPL meter. It reads 10 or 12dB less than it used to at the same setting on the Parasound.

    To confuse things more, the test tones from the Parasound STILL measure right on 75dB as they did before the change.

    And last, I *think* I am now hearing a small bit of distortion on male voice on almost any source. At this point, I might be imagining that, but I do have a very good ear.

    Now, this happens on any source, CD (analog in to the Parasound), DVD, Cable TV, etc. All are low, except for the tones generated by the pre/proc. The power amps have no level controls and meters show what I would expect when driving to the volumes I am accustomed to, so it is not a power amp problem. It is on both sides, so I doubt it has anything to do with the mains.

    Is it possible that the pre/proc outputs less to the mains when they are set to large and the LFE is turned off? Since the Parasound converts everything to digital then back to analog at the output, could either the ADC or DAC failed in some way? I'm baffled.

    Any ideas?

    -=Bob=-
     
  2. rodney wiley

    rodney wiley Second Unit

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    Maybe your ear has just gotten accustomed to the subs with the mains.
     
  3. Bob U

    Bob U Stunt Coordinator

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    I considered that, but then a 1kHz test tone should still measure the same and it doesn't.

    Last night, DVD level was down even more. On both main and surround channels, so I am suspecting the processor. I'm going to check all wiring today, swap power amps, etc, just to see if I can find anything amiss.

    -=Bob=-
     
  4. Evan S

    Evan S Cinematographer

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    If your subs were powered and your speakers are pretty inefficient, could it be that by setting to Large now you are taxing your amp way more than you were before by setting them to small and letting the powered subs handle all the low frequencies? I would think that this increased load on the amps would equate to the lower output and possibly the added distortion you are hearing.
     
  5. Bob U

    Bob U Stunt Coordinator

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    I've tried thinking that one through, Evan.

    The speakers are large Westlakes, 94dB 1 watt/1 meter, 4 ohms. The amp is 250 Watts 8 ohms, 500 4 ohms, This shouldn't be any problem. And, the distortion is there at any reasonable level and intermittant.

    The oddest thing is that the self generated tones from the pre are still 75dB, but a 1K tone from CD or DVD is down 10 or so dB. The more I think, the more it points to the input section of the pre, or the outputs if somehow the internal tones bypass the last gain stage.

    But, I'm still fishing here.

    -=Bob=-
     
  6. Bob U

    Bob U Stunt Coordinator

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    OK, experimented for the last few hours and here is what I discovered:

    Pre set to -18. 1KHz tone from DVD sent to main speakers. Center=OFF, LFE=OFF

    Mains AND Rears set to large= 72dB on meter

    Mains Large/ Rears Small = 74dB

    Mains AND Rears Small = 82dB

    So, there is my missing level, but why in the world would this be? Anyone have an explanation?

    -=Bob=-
     

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