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Old February 11th, 2004, 01:19 PM   #1
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Final Word on Bass Rolloff?

I've been searching, and this topic is touched on several times, but I haven't seen a definitive answer on whether it's a good idea to ever use an in-mic bass rolloff.

For example, I have a relatively less-than-pro Azden SGM-2X boom, and it has a really nice bass rolloff switch, which has helped me much when shooting in certain locations. But I'm wondering, should I instead just deal with it in full mode and do the bass rolloff in post? I use Vegas, btw, which I'm sure does this pretty well, since it's been so good to me with Audio features.

Basically, do pro's ever use in-mic bass rolloff? My gut says hell no, never, but I'd just be guessing. As always, I'm on the quest to get better, less tinny, less echo-y audio than that which always seems to plague small indie productions. I did much better in my last shoot at the end of last year because of the fine minds on this forum, but I need to get better. I realize also that I'm going to need a new mic to kick it up to the next level, but I know I can do better with mine. I've found some pretty good audio at times when I use the half-barrel indoors, and the full barrel outdoors. Not bad for a $200ish mic.

Imran Zaidi is offline   Reply With Quote
Old February 11th, 2004, 02:08 PM   #2
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I nearly always use bass rolloff. Even though it can be done in post, from my perspective it's best to not even have it there in the first place. It's more for removing rumble. If you are recording non-dialog and need full spectrum, then perhaps you'd want it in place.
I don't know that there is a 'final word' on this subject though.
Douglas Spotted Eagle/Spot
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Old February 11th, 2004, 02:21 PM   #3
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I guess my fear is that by using the bass rolloff, I might be shorting myself something in the dialog. But if normal dialog doesn't really ever plunge into the range that gets nixed by the bass rolloff switch, then I suppose it's a non-issue then...

I was going to try something new with my next shoot in a couple of weeks. I was going to use the boom on one channel on my DVX100A, and then feed a wireless lav into the other channel, and then decide in post what turned out better for the particular scenes. Do you think this might be a bad idea for any reason? I figured it would be a nice way to make sure that I'm getting good dialog while at the same time still having good ambience recorded to make it sound real.

Sigh, so much experience yet to gain in the location audio world...
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Old February 11th, 2004, 02:50 PM   #4
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Vocals CAN benefit from flat bass response, but not on a live shoot in most instances, and certainly not at any distance. Try some experiments on your own. Go record people in a mall at short distances with the rolloff enabled, do the same with it disabled. You'll notice more rumble than you'll notice voice improvements.
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Old February 11th, 2004, 03:00 PM   #5
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Using the bass rolloff or not depends on the circumstances. It depends on the mic, its knee-point and how its rolloff is shaped. It varies from model to model. Check the manufacturers specs for this. Some of them will eat into dialogue, some won't.
It also depends on what you're recording and how full bodied you want that capture to be. This decision can also be influenced by the other rolloff switches you have with you on a mixer or camera.
If you are hooking directly in, it also depends on which recorder you're using and how the sensitivity of the inputs relates to the output of the mic. Sometimes you can't spare any headroom that may be used up by unwanted bass energy.
As stated, you can take your time and do a more controlled rolloff in post, as long as circumstances weren't so severe that it clearly should have been rolled off in the field.
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Old February 14th, 2004, 11:50 PM   #6
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Hello Imran,

I'm a 20 year sound recordist for film and video. More and more I'm using hidden wireless
lavs to capture dialogue. I lav the talent (omni or uni depending on situation) and I use
another channel to capture "ambiance" (room tone). Doing it this way ensures that I
capture super clean dialogue and the amount of room tone (if needed) can be mixed in at
post (sound sweeting).

As opposed to using a boom w/shotgun; this helps to avoid many nasty things that makes
my job tougher such as:

An environment that is " too live w/echo" due to hard surfaces and mic to source distance.
I no longer have to set up acoustic sound blankets all over the studio/set.

I'm never off mic axis, when the talent “blocking” changes or if there multiple speaking

I never get a boom or the shadow of the boom in the shot

A director that NOW wants to do wide shot (lots of headroom) after I have boomed
(shotgun) recorded most of the dialogue at a much closer fixed distance from the source.
(continuity of sound when the mike to source distance changes radically)

Never have to "loop" or “adr” even on the widest of shots

My arms never feel like they are going to fall off and I can sit down instead of being a
statue w/arms raised all day or having to spend the day perched on a ladder).

For years I didn't like to use any type wireless (still have nightmares), I used the best pro
systems of the time; RF Associates, Celtic/Vega and Sony VHF systems. They were all
prone to; RF interference, poor signal to noise ratio, less than desirable frequency
response, funky RF harmonics and the pops and cracks of drift prone duel diversity

Now I have a Sony MB806A UHF wireless system with WRT-805 x-mitters, I use
ECM-77BMP (omni) and ECM-166(uni). For ambiance, depending on the
situation, I use either a Scheps or Sennheiser shotgun or another hidden lav placed at
roughly 3+ the same distance as the main source lav (3 to 1 rule), but aimed a little off
axis from the source.

The ECM-77 is a super mic, full bandwidth from 20hz - 20khz giving it a great
"presence", its other good feature is its rejection to "mic russel". I clip or tape it
underneath clothing (it has a very small pick up head), I do this when the talent is in
makeup, so as soon as talent arrives on set I'm all ready to go. And I don't have to worry
about "blocking aspects or massive headroom shots".

I always try to keep my mic's recorded discreet (pro Dats or VCR's have 4 sound
channels) I only use a field mixer when I'm forced to do a field mix because of more than 4
channels. (be careful-digital sound has very little "signal headroom" so the point of signal
(clipping) distortion is much lower than with analog type VCR's or 1/4"Nagras)

As far as your question about low Hz "rolloff" I rarely use it, because if it's needed, let it
be done in post sweeting (why strip off Hz in the field?). My goal as a sound recordist is
to capture dialogue with; good presence, good ratio between source and roomtone, full
dynamics and clean sound that is on axis, full bandwidth and non distorted.

Good luck with your shoot, try the hidden lav idea, play around with placement.

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Old February 15th, 2004, 11:26 AM   #7
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As a reinforcement for a small part of the post on hidden lavs, remember that to make best use of hidden lavs you must have access to 4-track or more recording devices. For 2-channel DV you only have room for one lav and one shotgun or 2 lavs without having to mix channels together. This means you either have to mix live with a mixer and run the risk of missing something, or you have to add channels together and hope that a problem with one doesn't do harm to the other.
For example, if you are trying to go with 3 total mics on 2 recording channels and have two lavs mixed onto one track and those two people stand close to each other and have a rapid interchange of dialogue, then there's nothing you can safely do to prevent phasing. If you try to have the 2 lavs split and are adding in some ambient sound to fill out the close-in lav character, then you can't change that in post once it's added in during the original recording.
As Bob Barter said, but I want to strongly reinforce, if you have enough recording channels to discretely record all your mics, then that's great. Most people on this board don't regularly have that available to them and are stuck with 2 tracks, no mixer (either machine or human) and are less likely to have the smaller lavs and high-quality wireless units.
It's great if you can lav everybody and have a boom or ambient for backup, but you've got to have the right equipment to make it work to your advantage instead of simply replacing one set of disadvantages with a new set of problems that can't be fixed later. If you want to try out 2 lavs versus booming on DV, remember to at least add some kind of backup recorder for your ambient or shotgun mic so you can have the latitude to adjust, replace or fix it later if something goes wrong with your lavs.
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