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some "Y"s

Posted by Joe Murphy Jr (A) on January 6, 2002 at 12:01:15

In Reply to: the Analog meter posted by Joe Murphy Jr on January 5, 2002 at 22:35:29:

You guys are too much. Instead of answering this person's question, you criticize my method. Did either of you give a description of a method for setting up the speakers in a home theater? By the way, everyone has a different way of setting up a system. Even the "experts" disagree on what's the proper way on one topic or another. What I have described is what I believe to be the best method for this poster to use in setting up his system without going into the many technical details as to "why" something is or should be done a certain way. I believe I answered his question and I made myself available for further explanation/set-up procedures. Can either of you say this?

[I also disagree on the method of setting up subwoofer level, since most method is to use pink noise to
match at 75 or 85dB. If the subs are not placed in the proper location, serious peaks and/or nulls would
occur, and if there are a couple of serious peaks w/o any significant nulls, the sub level would be set too
low, resulting in a uneven transition from the speaker to sub around the crossover freq. I personally
prefer to match the -3dB/-6dB level @ xo freq of the main/sub.]

[I recommend using the "C" scale, or you will never be able to calibrate your sub correctly in relation to
the rest of your speakers.]

#1 Where did I describe how to set up the sub? Please read the second to last sentence in my original response. It's a crapshoot if you don't know the details of his system and his preferences.

[Typically the "A" scale is used to quantify the amount of "damaging to the ear" SPL levels in the
workplace or anywhere else for that matter. Because of this the scale is limited in frequency response
(no bass) to the range -> 500Hz to 10kHz.]

#2 The A-Weighting area is where the ear is the most sensitive, therefore, this is the area that you want the most "equality" or "level-match" from speaker to speaker. This area is also where the most "directionality" of sound takes place and relates to the ears response to sound cues and how it perceives the environment.

[Why should it be aimed 45 degree (into the ceiling?) Wouldn't the off axis response cause the result to
be more inaccurate?]

#3 I don't believe "45 degrees" is into the ceiling -- that would be 90 degrees. This number is based on 15+ years of personal experience and my own measurements and comparisons using different set-ups, information from several home theater publications and DVD set-up discs/guides. I have observed the results using 0 degrees, 45 degrees and direct line (varying degrees) to the speakers. In my opinion, the 45 degree angle mentioned in my response provides the better sounding home theater experience.

[The "C" scale, on the other hand, measures over a more musical range from 32Hz to 10kHz. Measuring
with the "C" range may also capture room mode peaks when using pure tones as the test signal source,
but this can be corrected by using "warble" tones such as those found on the "Stereophile test CD disk
2 & 3".]

#4 Let's be realistic and put this in proper context. The question from the poster -- no disrespect intended -- was from someone that wants know how to use an SPL meter to set up his speakers. Do you really think he needs a lecture on these topics: warble tones, C-Weighting, room nodes and the Stereophile test discs? Do you really think he wants one? I believe the details that you are going into are more applicable to an Audiophile or Videophile "nerd" -- my hand is raised -- or a professional A/V installer. That being said, do you really think a $40 Radio Shack SPL meter is comparable to The Audio Toolbox at $1500?

[Also, I would assume that the meter would have to be aimed at the speaker that is producing the sound,
the 120+ deg off axis response for the ratshack mike would be terrible for the high freq portion of the pink
noise.]

#5 No, I said straight forward at a 45 degree angle -- not aimed at the speaker -- and where do you get the 120 degrees off-axis from?

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