Bass roll-off question

N

notCardio

I walk the line
Everyone's always saying how you should try to get by with as little eq as possible, but they're always touting the benefits of a bass roll-off on the mic itself. How is this different? Is it simply because it's a passive eq (or is it?) and most post-mic eq is active? Can someone explain this in really simple terms?

Thanks
 
It's more because it is only affecting the very lowest frequencies which on many sound sources are not contributing anything positive (and could be adding negatives) to the recorded sound.
 
I understand the need for the bass roll-off, I just don't see what the difference is between doing it at the mic, and doing it at the board, especially since so many mixers have that specific option.
 
it doesnt matter if you do it with the mic or on the board as long as you do it before it hits tape...it will have the same effect either way.......
 
Most mixers will have a "low cut" that basically works it's way down from around 80 hz. I love Mackie's owner's manual -- says something like "Always use the low cut on all your tracks . . . except for bass guitar, kick drum, and recordings of earthquakes." Always get a kick out of that one.

Anyway, a lot of mics, like the sm57 for example, will naturally start rolling off at about 200 hz. It's more of a gradual rollof, mind you, as opposed to the steep "falling off a cliff" cutoff point you'd normally get with the bass cut on a mixer.

The difference between the two is that the bass cut on a mixer just clears up any of the really low and subsonic stuff. Rumbles, tubles, and that sort of thing. :) A bass rolloff, be it a switch or a natural feature of the mic, works more as a musical effect. One of the reasons it works so well on the snare drum or close-micing of guitar amps. The bulk of the snare's energy is usually around 200 hz, so it's a good idea to roll off anything below that point, which the 57 does naturally. Similarly, 200 hz is a good point to start rolling off on an electric guitar track, so as to free up some breathing room for the bass guitar, snare, etc.

Hence, one of the true values of the 57 -- the tracks it records require much less fiddling with after the fact.

As far as why this would be valuable over just eq-ing it after the fact, think of it this way: When I record a track on my computer, for fidelity purposes, I want it to take up as much of the 24 bits that I have available. Suppose a good portion of those 24 bits contain unnecessary bass content which I plan on cutting out.

Now I'm not going to pretend to be an expert on digital recording, and I could be totally wrong on this, so if anyone wants to chime in and correct me please do so. But it just seems more logical to me that it would be a more efficient use of my available bits and/or magnetic particles (if I'm recording analog) to use as much of them as possible on audio information I'm planning to use? As opposed to recording, say, 20 bits worth of audio and then shaving off 1/4 of what those bits have recorded (mostly unnecessary bass content) ? ?
 
I wasn't referring to cutting the bass after it had been recorded, but during tracking, nor was I referring to any natural qualities of a mic. I wanted to know what the difference was between using a bass cut SWITCH on a mic vs. a bass cut switch on a board. Since most boards and even standalone preamps seem to have them now, what's the big deal about whether a mic has that switch or not? People on this board were saying that they wished the early C-1's had it. Unless they were using a board or pre that DIDN'T have it (unlikely), why all the fuss? Is there a point I'm missing here?

Thanks for trying to get it through to me.
 
I see. In most cases, the bass rolloff switch acts in the same manner as a 57 does naturally . . . just sort of gradually rolling off the low end, and it usually starts somewhere around 200 or 100 hz (stuff that makes a real difference that you can instantly hear) as opposed to 75 or lower (mostly rumbles and other subsonic stuff that can take up unnecessary bandwidth). The bass cut on a typical mixer will pretty much lop off only the really low and subsonic stuff, but doesn't really do anything to cut out "the mud" or make it sit better in a mix, per se.
 
Ok, so you're saying that it's the actual frequencies being cut and the "slope" of that cut that's the difference, not the point (in the signal path) at which they are being cut. If you had a bass cut switch on a mic that had the same cutoff frequency and rate as the switch on your board, it wouldn't really make any difference which one you used, am I correct? Just want to get that straight.

If that's the case, I get it, and thank you very much!
 
One advantage to a roll off on the mic is that you have less low end hitting the preamp so you can get a stronger signal overall that is composed of the frequencies that you want to use. In general bass eats up headroom so the same principal applies anywhere in your signal path. The sooner you get rid of the bass the sooner you can maximize your signal to noise ratio.

As to the actual technical differences between a mic or preamp/mixer roll off I have no idea. If Alan Hyatt was still around he could probably fill us in but for now we are stuck with Chess and Gidge as our technical experts ;)
 
oh pu-leeze...im clearly an idiot, but Alan Hyatt is nowhere near the only person on this BBS qualified to answer that question.......

these forums have been pretty peaceful with him not around...dont spoil it.....
 
Gidge said:
Alan Hyatt is nowhere near the only person on this BBS qualified to answer that question.......
Click to expand...

Tex seems to be picking up some slack in that area, I see. Nice reply to that post, and a good way of explaining it. Somehow, I have a hunch that certain people in question wouldn't even bother answering a question like that anyway . . . unless it had something to do with a certain company I won't mention either. :)
 
Most board low end eqs are either of the shelving type (where they drop the signal by a certain level and it then stays constant below that frequency), or the peaking type (where the signal drops in a one octave range around the desgnated frequency). Neither is as effective as a simple high pass filter built into the mic that provides a gentle roll-off, from the chosen cutoff point all the way down to the lowest frequencies.

And yes, Alan could have givin you the answer if he were still around, but I see some people still won't let it drop here - very sad.
 
Actually, I think the subject at hand is very symbolic. The bass frequencies are something that, in the right context, can carry a lot of valuable audio information. They provide foundation and balance to the mix.

But you have to take it in context. And in the right context, they provide just that. But in the wrong context, they can make your mixes sound muddy as they show up in the wrong places and accumulate when they don't actually have something to contribute to the audio material at hand.

When they appear in just the right context, ie: when they find their proper place and context within the mix, they can serve as the very foundation of the song . . . rounding everything out and being felt as well as heard - making everything else sound better.

The bass frequencies cannont be self-serving and contribute at the same time. That's a conflict that is best worked out and dealt with before they are worked in to the mix.
 
Now I've got a question.How about using a software high pass filter while I track?Would that amount to about the same thing?The way I record at home is through my Audio Buddy right into Cakewalk via my Audiophile.I do have a couple small mixers but I only use those for tracking outside of my home.I would rather not introduce them to my signal chain if possible.I was applying a high pass filter after tracking and been getting decent results but if I could get more headroom by applying the filter while tracking it seems to me that would be a good thing.Thanks,people.
 
Card,

Several months ago, Alan expressed surprise that "the market" demanded the C-1 have a bass-cut switch, for just the reasons you mentioned.

All things being equal, I'd rather my source signal not go through a switch and yet another couple of solder connections. But I appreciate Mr. Gerst's argument for a simple low-cut filter as opposed to EQ. However, don't most mixers have low-cut filters on the mic inputs before the signal reaches the EQ section?

The important thing is to cut the ambient low-frequency noise before it hits the tape, as we all agree. My brain tends to filter out these background sounds, and I'm always surprised to watch the meters jumping during a "silent" period on what I consider a quiet day. A loaded semi rolling down the hill beside our house produces higher SPLs than an ambulance siren, although the latter seems subjectively much louder.

Perhaps Mr. Gerst can explain why low frequencies eat up so much bandwidth. Is it because they move more air?

Best wishes,

Mark H.
 
Randy,

The more you cut unwanted low frequencies before they reach your recording medium, the more "bandwidth" is available to capture musical information.

I don't have any experience with computer recording, but I can give you a simple example from analog tape. I used to have a neighbor with a large homemade subwoofer in his trunk. He'd play his stereo while he washed his car. I'd be taping a session with a client on a desktop tape recorder, and with each "thump," the recording-level LEDs would max out.

Playing back the tape on the same recorder with a small, built-in speaker, I could not hear the bass notes that were recorded. Instead, I heard horrible distortion and greatly reduced intelligibility in the voice recording I was making. The neighbor's subwoofer was saturating my tape with "noise," obliterating the "information" I was trying to capture.

If you had infinite bandwidth, then a software fix would be fine. But chances are you're losing detail by not cutting out the extraneous LF noise before it goes to your hard drive.

Best wishes,

Mark H.
 
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