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Gear / Technical Help => Microphones & Setup => Topic started by: (Evan) on December 17, 2010, 07:35:34 PM
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Hey guys. So I was wondering whether there is any difference between rolling bass off using my Sony D50, vs having an actual hi-pass filter on my microphones? Is one of these a better option? Thanks.
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Per the terminology, a roll off fades the bass end by say 6dB per octave past a certain Hz. The HPF is misleading in that it's the frequencies that you want to keep, the High Frequencies. As in those above a certain Hz. Both of which reduce the low end, which is mostly responsible for Hum, Wind noise, Handling noise, and other nasties. But sometimes you actually want to keep those frequencies. They mainly differ in how fast the low end fades and at what Hz.
I try to avoid using them. But recently noticed that my microphone preamps have said roll off switches on them, and in high wind situations using that trigger, lets me boost the gain a little hotter (more normal) despite the wind distraction. And as long as I'm not recording music with a bass track, not that problematic. If you have a Bass Voice / Tuba Voice you might want 30Hz and higher frequencies. Even though 60Hz might prove problematic, because of that A/C power thing. And it's harmonic 120Hz as well. (or 50Hz / 100Hz in PAL land).
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If you need to use roll off, is better in mic than recorder.
Saludos!
Erick del Valle
Santiago de Chile
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If you need to use roll off, is better in mic than recorder.
Agreed, with the caveat that all things are equal. All things equal, use the rolloff on the mic first. But if you think you need only a slight rolloff, you'd be better using the recorder or separate preamp if it offers a 75Hz rolloff with a 6db slope, rather than using a 160Hz rolloff with an 18db slope if that what is all that is available on the mic.
Bottom line, best using the rolloff that best matches your needs. If the same rolloff can be found on both the mic and the preamp/recorder, use the mic's rolloff.
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FWIW, my preferred approach: unless I need the rolloff to prevent overloading somewhere in the recording chain, I roll off in post so I have full control over the threshold and slope.
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FWIW, my preferred approach: unless I need the rolloff to prevent overloading somewhere in the recording chain, I roll off in post so I have full control over the threshold and slope.
agreed.
Cardioid, and other directional mics I suppose, have a "proximity effect". If you are within a few inches of the sounds source (mic in front of a vocalist, or close mic'ing a guitar) then you might want the roll off to counteract that effect. If you are more than a few feet away from the sound source, you don't need it. I've used roll off twice in the last few years, because at the time I thought I might need it. Both times I decided afterward that I shouldn't have used it because the bass was a little thin.
I suppose if you are running omnis close to stage at something which is ridiculously bass thumpy, and you can feel the energy from the subs hitting you in the chest, maybe there is justification for running rolloff. Otherwise, no.
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FWIW, my preferred approach: unless I need the rolloff to prevent overloading somewhere in the recording chain, I roll off in post so I have full control over the threshold and slope.
Agreed
how can you know if you actually need roll off before you record?
record - roll of the amount you (perceive) you need in post.
I've heard too many recordings (that I perceive) lack bass or any smooth low-end - 'cause they were recorded with bass roll off...
tweek the amount you need or don't need after the show not before.
--Ian
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how can you know if you actually need roll off before you record?
record - roll of the amount you (perceive) you need in post.
I've heard too many recordings (that I perceive) lack bass or any smooth low-end - 'cause they were recorded with bass roll off...
tweek the amount you need or don't need after the show not before.
--Ian
Generally, I agree, but I still think there are situations where roll-off at point of capture will be of benefit. I've taped in situations where the bass notes masks everything else and it seems like I have better EQ capability in post if I try to get a better balance at point of capture.
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There's some variation in the following so YMMV, but: "Rolloff" tends--at least somewhat--to imply a relatively gentle decrease in response above or below a given frequency. "Filtering," on the other hand, tends to imply a possibly stronger action. By the time you get into steep filtering--12 or 18 dB/octave or even greater--that would almost certainly be called filtering rather than a rolloff.
With filtering, it's reasonable to want to know the turnover frequency (i.e. the -3 dB point on the curve) and the steepness in dB/octave (or alternatively, the number of "poles"); that way you can make much more meaningful comparisons. For example my Grace Lunatec V3 preamp has a switch setting for two-pole (i.e. 12 dB/octave) filtering below 50 Hz; "below 50 Hz" specifically means that the filter creates a -3 dB gain (or 3 dB of loss, if you prefer) at 50 Hz. With a rolloff, "below 50 Hz" wouldn't necessarily imply that the response is down 3 dB at 50 Hz although again, it might, especially if a specific slope is given (such as 6 dB/octave).
I hope that doesn't make things seem even more vague.
--best regards
P.S.: I don't get why someone would make the blanket statement that it's better to roll off in the microphone than in the recorder, except in cases of near-overload to the input of the recorder/preamp/mixer. In that case, sure, because the decreased voltages coming out of the microphone would be less likely to cause input overload in the preamp. That makes sense especially where wind noise is concerned. But otherwise, how often are you right on that threshold, and wouldn't there usually be a better solution available?
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That makes sense especially where wind noise is concerned. But otherwise, how often are you right on that threshold, and wouldn't there usually be a better solution available?
Only once have I ever had this situation, the day after I got my mixpre I got to a show not really knowing what to expect, ran km184's which had no attenuators, was getting absolutely blown out and switched on the 80Hz @ 6dB per octave which calmed things down enough for me to tape the show. I then went and got the "better solution" which was some inline pads as I've mentioned in some other threads.
I do notice listening to tapes of friends I tape with that running a 40Hz rolloff @12dB per octave can make an otherwise ugly sounding room sound a bit more framed and the recording somewhat more under control or ruly, basically only cutting out what usually amounts to the ugliest part of low end, that's on a 722, the mixpre is a lighter 6dB per octave rolloff at 80Hz which I find to be a bit much. Even with the softer tail the wider frequency span up to 80Hz cuts out too much of the low end for my tastes. IMO, It would have been nice if the mixpre had a 40Hz@6dB which I feel might be the best rolloff for live recording indoors if any were to be used. Those are my experiences when a rolloff is used, however, it should be said that as a rule, I run wide open and just deal with it in post of necessary. It's always seemed easier to take out, than to put back in, to me at least.
This post probably won't help you at all with the technical difference you asked about but perhaps it will help you to choose what's best for your particular application.
Cheers,
J