Right now I have a basic audio processor that has a standard single AGC and multiband limiters. I was wondering if there actually is much benefit to having a multiband AGC? Now of course to some people I'm sure there is, however, I don't like my music F-ed with. I have a feeling that the multiband AGC will make the more dynamic parts of the music just sound flat. Essentially it's normalizing the levels of everything, so if part of the music's frequencies are meant to be quieter than others, will it just flatten it and make it sound more boring? Yeah, maybe it'll be louder, but I don't want to sacrifice the quality of the music.
Also, if you set all the AGCs to the same levels, will it have the same result as having only one AGC or will it still act differently?
Have you ever tried one and can comment on what it sounds like or maybe you just know enough to tell.
I doubt there would be any benefit of having multiband AGC.
Normally the AGC is used to keep everything from the studio at an appropriate level for feeding the crossover/multiband limiter section. The AGC should be slow enough that all audio rides around a tolerable level and then the multiband limiter is used to separate sections of the audio for individual processing so low frequencies don't cause punched holes in high frequencies and vice-versa across the spectrum depending on how many crossover networks are involved, usually 3 to 5 individual bands being plenty efficient for most music, and sometimes special treatment for the voice range for when the processor detects talk only.
Of course the sound contour is strictly up to the engineer by setting the limiters attack and release times, drive levels, and even crossover frequencies.
The AGC should be mostly transparent since it's the first stage of audio processing. Slow gain changes riding on both pits and peaks of audio to smooth out the overall loudness over a few seconds of live audio with instant attack time in case of sudden loud sounds so not to overdrive the limiters ahead. The resulting audios character will reside on all the settings of everything after the AGC, or at least should.
Only thing that sort of makes sense with "multiband AGC" is the use of a multiband downward expander ahead of each limiter stage which isn't quite the same thing. This is only used to keep quiet sounds dead silent below a threshold, and rapidly rise audio to normalized upon normal level music/voice. This would be to keep things out like tape head hiss, vinyl record wear, or studio background noises that would otherwise be sucked up largely by the limiters. This is kind of the reverse of AGC though depending on how you look at it.
"Only thing that sort of makes sense with "multiband AGC" is the use of a multiband downward expander ahead of each limiter stage which isn't quite the same thing. This is only used to keep quiet sounds dead silent below a threshold, and rapidly rise audio to normalized upon normal level music/voice. This would be to keep things out like tape head hiss, vinyl record wear, or studio background noises that would otherwise be sucked up largely by the limiters. This is kind of the reverse of AGC though depending on how you look at it".
This makes sense, and pretty much describes, I think, the idea behind the now "long in the tooth" Aphex 320A Compellor used in front of the Aphex Dominator II. The Compellor, whose name is derived from its working as both a Compressor / Leveler has the additional feature of setting a threshold of silence to prevent noise from rising up in quiet audio passages, be they speech or music as well as quite decent at compressing & leveling.
Typically, the Compellor feeds the Dominator, which is a multi band (3 band) limiter. Both units have the ability to mangle the audio to complete uselessness, or when used carefully, can compliment audio punch and clarity.
With these 2 units I can put a hotter signal into my FM Xmtr without distorting and when set up properly it makes not quite as loud as others on the FM dial in my universe but the music sure sounds a lot better.
I find it a lot easier to tweak with real knobs. Having lots of blinking/flashing lights helps to compare if you don't trust your ears.
These units are generally easy to locate on the used market and are reasonably priced for what they offer. If I could only afford one or had to purchase separately I'd go first for the Compellor.
These 2 hardware units are superseded today with software that probably does a better job, however having worked in commercial radio in the 70s, 80s and 90s I grew fond of that existing technology and its sound.
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