There is a lot we still don't understand about how the human processes what they hear. There is a lot of silliness in the audiophile world, but keep in mind they are the ones who pushed audio pros to do better. And it turns out that sometimes they are right.

Extended bandwidth, especially on the high end, seems to be the hallmark of most of the revered vintage gear. Now the truth is, the upper limit of the pass band was out around 40kHz, or even 80kHz because they couldn't build filters with steeper slopes that didn't ring terribly. BUT, it turns out that those gentle slopes may have contributed more to the sounds we like than we realize.
 
I designed a microphone preamplifier a while back. I used all discrete, Class A gain elements, no negative feedback, precision current sources, and multiple blocks of moderate gain (yeah, it should sound familiar<G>!) But I was designing this to have a digital output, so I spent a great deal of time playing with the Low Pass Filter at the output of the preamplifier. Actually, I tried placing the LP filter at different points, including as the very first stage. Everyone that listened to this design agreed that it sounded better with no LP filter. As it turns out, modern "Switched Capacitor" filters on the input of most A/D converters to a very nice job of band limiting at somewhere below the Nyquist frequency, so it wasn't as big a deal as I expected.
 
So what do we do about large multi-track productions where 20, 30, 40 or more tracks will contribute significant energy in the upper registers, and most of that energy will be noise? I tend to use gentle filters (even though there are digital filter configurations that do not cause phase problems, and don't ring) and I still tend to place them at least an octave above where I might think they need to be. And I place them on the individual tracks, because one the tracks are summed together it's a lot more difficult to address noise problems.
 
As far as the low end goes, if the source is electronic I don't use High Pass filters... there isn't going to be any energy there anyway. If the source is acoustic then I will place a HP filter early in the recording chain.
 
One important caveat, that several folks have pointed out, is that NONE of this is done to gain an advantage in terms of levels. It is done entirely to manage the noise contributions. I still think that -18 dBFS is a fine operating point!!!!

Nice thread.

Always loved the above cartoon from many years ago.  Unfortunately I was unable to find a higher resolution copy of it for you ... If you can't read the sign in the window it says:
 
Senior Citizens!
Why pay for useless thrills?
By this 1200 - 5800 Hz
Speaker System and Save!!!

Good one, Dave. Of course, when today's teens become senior citizens they won't need the Senior Special. They'll have been conditioned by years of listening to plastic earbuds to have low expectations. The sign might read "these speakers sound just like your earbuds, but more than two people at a time can listen to them!"
 
 

Danny Danzi

backwoods
This is for my own education mostly. After fiddling around with Izotope and the brickwall filters I got to thinking.
 
Why not brickwall the low frequencies and the hi ones- say over 18000 that no one hears or cares about on standard playback equipment. Won't we then be able to push the signal higher without distortion for a louder file?
 
Also, why does a hi pass at say 40hz cause a file touching zero to clip? 

Anything under your target low frequency (we can use 40 hz for this example) should be removed....anything up high that is doing nothing, can also be removed. I do it all the time. But some things may show a little activity in those ranges too, so you have to be careful. Some of this will be genre specific too.
 
For example, if we remove everything below 40 Hz in a r&b song or rap song, we just affected any bass drops they may have had in the song.
 
If we remove 18 k and above (which is usually safe to do) there are a few plugins out today that accentuate like 22 k. I see them as senseless but some guys swear by them and I have a few clients like that. They literally feel that high end air is making a difference for the better where to me, it's adding hiss that can mess with the audio.
 
So depending on what style of music you are working on will determine where you high pass and low pass. I think you'd be better off high passing and low passing over brickwalling the stuff. This way you have a little more control over what you allow to pass through naturally where as brickwalling it could introduce artifacts.
 
A file touching 0 dB is clipping in the digital realm unless you are literally getting readings of -0 dB. But at regular 0 dB without the minus, you'll show clip points no matter what you add to the audio unless you are cutting something drastically. But just about anything you bring in will clip a file like that. It may even clip just passing through the plug without touching a parameter on the plug.
 
Your best bet is to keep anything un-mastered at -3dB peak...anything you master, -0.3 and no hotter than -0.1 dB peak. But after something has been mastered, there is a good chance anything you add will make the song clip...even if you're high passing.
 
Though -0 dB doesn't show up as a clip, you shouldn't really go that high if you can help it as you're just way too close to the clipping zone and chances are you just may go over.
 
-Danny

Hi Danny, just a couple of things from the above statement, -0.2DB is now the worldwide mastering standard and get this mastering for I-Fools its -1DB.  I'd have to hunt for the article in regards to mastering for I-Fools but apparently that's the level.  Sorry for going off topic.
 
Ben

-0.2DB is now the worldwide mastering standard...

Can you cite an authoritative reference to support that statement?
 
AFAIK, there is no standards organization for mastering, but -0.2 dB could still be a de facto standard by consensus. I've only checked a small handful of recent releases personally, so I wouldn't know.
 
However, I do have a great many CDs that peak well under -1.0 dB, so if this is indeed the worldwide standard then it must be a recent development. Or was your statement perhaps aimed at a specific musical genre or market segment?

Well, -.3 used to be the "standard".  For no other reason than it was the default preset in the widely used Waves L1 Ultramaximiser.  I don't know how it slowly crept up to -.2 but that seems to be a consensus by no other reason than popular use.   Many older disks and independent projects don't follow the popular consensus.  For my own classical work sometimes I won't get anywhere near the peak, but that is because I master to average levels for the entire disk first and foremost. 

Rimshot
Nice thread.

Yep.

bitflipper

-0.2DB is now the worldwide mastering standard...

Can you cite an authoritative reference to support that statement?
 
AFAIK, there is no standards organization for mastering, but -0.2 dB could still be a de facto standard by consensus. I've only checked a small handful of recent releases personally, so I wouldn't know.
 
However, I do have a great many CDs that peak well under -1.0 dB, so if this is indeed the worldwide standard then it must be a recent development. Or was your statement perhaps aimed at a specific musical genre or market segment?

Hi Bit, it's what's taught in all the audio schools these days.