SouthSIDE Glen
independentrecording.net
I mentioned earlier that there were a few reasons for this happening, one being the frequency vs. amplitude physycs thing, which is the same thing that Farview was talking about.
Another is the nature of the RTA display itself. Remember that you are looking at a logarithmic scale. One centimeter left-to-right at the low end is represents only a few Hz, whereas the same distance at the high end represents several kHz or more. It's a thousand-to-one difference in scale. The natural decrease in amplitude that accompanies the increase in frequency will also be displayed with that 1000:1 scale change. A straight line from the top left to the bottom right would be bent into a hyperbolic curve. Part of what you're seeing in that rapid drop off is a function of the display scale used by the RTA.
A third, but probably more minor consideration is that many RTAs are just not that accurate or "sensitive" above 12 or 15k because of the way they are manipulating the FFT numbers. Some of them make some comprimise in mathematical accuracy at those frequencies to make their software more responsive and less of a CPU hog.
A fourth consideration - and question to you guys - have you looked at this stuff with something other than metal as your source? The producer may have simply taken much of the high end out because a wall of Gibsons doesn't need it. Switch to jazz, classical and even more mainstream pop and alt rock CDs, and (on a quality recording, anyway) you'll find plenty of information up there.
Fifth, much of this stuff is engineered to sound best on the radio (or even sometimes now, on MP3.) FM broadcasts are only solid up to 15k, and lord knows that MP3s are useless for anything above 12k. Just as they used to emphase the midranges and not worry so much about the highs back when they wer engineering for AM radio, engineering for FM an Podcast can save studio time and money and optimize the sound by leaving off the high stuff.
All and all, though, it's a tempest in a teapot, IMHO. Those who have been around here for a while know the general disdain I have for RTAs - except in certian circumstances. But even putting that aside, I go back to the start of my original post and add a little more:
If it sounds good, leave it in, if it doesn't take it out. If it has no direct bearing on the sound, forget about it. In this case the RTA signature falls in the thrid category.
G.
Another is the nature of the RTA display itself. Remember that you are looking at a logarithmic scale. One centimeter left-to-right at the low end is represents only a few Hz, whereas the same distance at the high end represents several kHz or more. It's a thousand-to-one difference in scale. The natural decrease in amplitude that accompanies the increase in frequency will also be displayed with that 1000:1 scale change. A straight line from the top left to the bottom right would be bent into a hyperbolic curve. Part of what you're seeing in that rapid drop off is a function of the display scale used by the RTA.
A third, but probably more minor consideration is that many RTAs are just not that accurate or "sensitive" above 12 or 15k because of the way they are manipulating the FFT numbers. Some of them make some comprimise in mathematical accuracy at those frequencies to make their software more responsive and less of a CPU hog.
A fourth consideration - and question to you guys - have you looked at this stuff with something other than metal as your source? The producer may have simply taken much of the high end out because a wall of Gibsons doesn't need it. Switch to jazz, classical and even more mainstream pop and alt rock CDs, and (on a quality recording, anyway) you'll find plenty of information up there.
Fifth, much of this stuff is engineered to sound best on the radio (or even sometimes now, on MP3.) FM broadcasts are only solid up to 15k, and lord knows that MP3s are useless for anything above 12k. Just as they used to emphase the midranges and not worry so much about the highs back when they wer engineering for AM radio, engineering for FM an Podcast can save studio time and money and optimize the sound by leaving off the high stuff.
All and all, though, it's a tempest in a teapot, IMHO. Those who have been around here for a while know the general disdain I have for RTAs - except in certian circumstances. But even putting that aside, I go back to the start of my original post and add a little more:
If it sounds good, leave it in, if it doesn't take it out. If it has no direct bearing on the sound, forget about it. In this case the RTA signature falls in the thrid category.
G.
)
It'll probably go away just in time for this Saturday's gig, at which point I'll be setting up and mumbling to myself, "One of these days..." 
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