Finally got a SPL...how do I use this thing?

Discussion in 'Archived Threads 2001-2004' started by Scott Simonian, Apr 13, 2002.

  1. Scott Simonian

    Scott Simonian Screenwriter

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    Actually, I know how to use it, I just dont know if I know how to use it correctly.
    I just got it today. Ive been playing with it around the house. I know how to read the SPL reading, setting it to the correct SPL the the knob and all. The "A&C weighting" doesnt make a whole lot of sense but I know which to use. I get teh slow and fast response. I got that down quick.
    I just dont know how to use it in the HT. What am I supposed to use for calibration? I dont have VE or Avia. I dont feel like going back to the store to get one of them either. The only thing I have is the movies with "Optimode" and I was under the impression that it was no good.
    For what, I dont know. All I really want to check is the bass response in my room at the listening area. Whats the quick fix?
    Oh yeah, I have a tone generator on my computer. I could burn a few tracks on a CD, but my DVD player and Xbox dont like CDRs or CD-RWs. UGH!
    Woops, I also think Im going to need the RatShack SPL meter correction numbers. I dont know about the digital, if it needs correction. Who cares about teh digital meter anyway, I got the analog meter. [​IMG]
     
  2. Bill_Weinreich

    Bill_Weinreich Second Unit

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    Scott,

    You're well on your way. You know the range settings and the slow setting (used for averaging levels rather than peak) but about the weighting. Set it to C. That gives a frequency range 32hz-10khz(A weighting is about 500hz-10khz). Without a test disc, you can use the internal tones of the receiver. The advantage of the test disc is that you are getting the levels from the DVD(all wiring and processing included). The best way to use it is on a tripod at the main listening position. Point it forwards and angle it up to about where the front wall meets the ceiling, grab your remotes and get started.

    P.S. the analog works great no need for the digital

    Bill
     
  3. Scott Simonian

    Scott Simonian Screenwriter

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    Yeah, digital sucks. :p)

    I went ahead and put a tone generator on my dads PC tablet. I got my SPL from my room. I wanted to know how it was at the seating location so I left (most of) the things in the HT at normal. I wanted something realistic and common. I did the testing at a little on my personal volume.

    I got the RadioShack meter correction off the web. There are some gaps in it though. Do I just put the corrections where it is listed? Or do I guesstimate the parts between the frequencies.

    For example, 10hz > +20db, 12.5hz > 16.5db, etc.

    I wish I knew how to use Excel better. Im not sure how to make the right graph for such a thing. Whats the quickest way to make a graph for SPL measurements on Excel?
     
  4. Scott Simonian

    Scott Simonian Screenwriter

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    Hmmm...

    Maybe if I put up my awful measurements, someone would lend me a hand. I gotta fix this.

    Here they are, corrected.

    100hz - 96.5db

    90hz - 86db

    85hz - 93.5db

    80hz - 99.5db

    75hz - 97db

    70hz - 98.5db

    65hz - 98.5db

    60hz - 95db

    55hz - 95db

    50hz - 91db

    45hz - 91.5db

    40hz - 101db

    35hz - 96db

    30hz - 94.5db

    25hz - 91db

    20hz - 91.5db

    18hz - 76db

    15hz - 72db

    10hz - 71db

    Now, not all those frequencies were stated on the form of corrections that I have. So, I only put corrections on the frequencies that stated for correction. The others were left as recorded.
     
  5. brucek

    brucek Second Unit

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    Scott,
    Generally, when measuring low frequency response, most people measure from 16Hz to 160Hz at 1/6 octaves, at about a level of 85dB to 90dB SPL taken with a Radio Shack SPL meter at your normal prime listening position. For a source, use a CD playing 3 to 5 second sine wave tones..
    Take measurements using the sub only and your processor with normally used crossover frequency.
    The correction constants for the Radio Shack meter for 1/6 octaves are valid for sine waves and are:
    16Hz +11.5
    18Hz +8.0
    20Hz +7.5
    22Hz +6.5
    25Hz +5.0
    28Hz +4.0
    31.5Hz +3.0
    36Hz +2.5
    40Hz +2.5
    45Hz +2.0
    50Hz +1.5
    56Hz +1.5
    63Hz +1.5
    71Hz +1.5
    80Hz +1.5
    89Hz +1.5
    100Hz +2.0
    111Hz +1.0
    125Hz +0.5
    142.5Hz +0.5
    160Hz -0.5
    It's a good idea to use the information and Excel graphing tool on Sonnie Parkers site (listed below) which has the graphs all pre-done including compensation correction for the SPL meter.
    Read all the information on this site including the links. The site is dedicated to equalization with a BFD. Even though you don't have an equalizer, the information is still very valid.
    http://www.snapbug.ws/bfd.htm
    Limit your testing to sixth octave tones. The Excel tool on Sonnie's site is set up for this.
    brucek
     
  6. Bill Kane

    Bill Kane Screenwriter

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    brucek, counting your scale above, I have seen 3 RS conversion corrections. THE MOST COMMON:

    20hZ-+6.2dB

    25hZ-+4.4

    31hZ-+3.0

    40hZ-+2.0

    50hZ-+1.3

    63hZ-+0.8

    80hZ-+0.5

    Yours has much higher values added.

    I wonder if there are difference among SINE WAVE TONES, PINK NOISE Tones and/or Receiver-Generated Tones?
     
  7. Scott Simonian

    Scott Simonian Screenwriter

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    Ah great, that web page was exactly what I was looking for.

    Thanx

    So do we have the real corrections somewhere?
     
  8. brucek

    brucek Second Unit

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    Bill,
    The constants I listed are the accepted values from many trusted sources, including SVS where you'll find 1/3 octaves.
    http://www.svsubwoofers.com/faq_rscomp.htm
    These are correction constants to simply compensate for inaccuracies in the meter.
    brucek
     
  9. Scott Simonian

    Scott Simonian Screenwriter

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    Bruce,

    On the SVS site, it gives correction values that are not the same as you have just stated earlier. Where did you get those? The correction chart that I have is the same as the one on the SVS site. My list goes throughout the whole audible range, though.
     
  10. Scott Simonian

    Scott Simonian Screenwriter

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    Excuse me, I miss read your post. Your correction values are right.
     

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