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Author Topic: Newbie Question: Roll Off  (Read 6136 times)

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Offline realkuka

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Newbie Question: Roll Off
« on: May 06, 2010, 11:00:50 AM »
Hi,

I would like to understand what is exactly the roll off, and how can I use it to improve my recordings , I have a battery box that I can set up in 16, 69, 95, 107, 160, 195 and 888 hz.

Thanks!!

Offline guysonic

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Re: Newbie Question: Roll Off
« Reply #1 on: May 07, 2010, 01:49:57 AM »
Live pop/rock music venues often have much louder low frequency bass than normal for home speaker playback. 

Older tecnology 16 bit depth recording limitations forced recording with maximum VU levels so resolution (audio details) were optimum, but this is not an issue with far more detailed 24 bit flash recording. 

If using 16 bit recording modes, then bass from most mics (usually more an issue with omni capsules) drives the maximum loudness of the audio making the recordist turn down VU levels from mostly bass strong levels.

And then the mid-high frequencies are way down in relative recorded level where far less 16 bit resolution is at work. 

Using a mic bass filter while recording reduces the very loud bass signal , and so now much louder mid-high signal frequencies get recorded at higher VU levels, and this is more optimum for vocal/guitar and other instrument operating at the higher frequencies. 

Again, if recording in 24 bit mode, then not necessary to use bass filters while recording, just reduce bass to desired balance in post software (and everthing else you want to modify on copy of master 24 bit recording with editing) BEFORE converting edited version of your recording to 16 bit depth for CD or sharing.
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Offline willndmb

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Re: Newbie Question: Roll Off
« Reply #2 on: May 07, 2010, 12:26:23 PM »
awesome info by guy
what i liked to do - if you record in a venue with a lot or with mics that are more bass heavy that you set it on some level of roll off
i used 95
it saves you time in post if nothing else
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Offline realkuka

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Re: Newbie Question: Roll Off
« Reply #3 on: May 07, 2010, 04:10:40 PM »
thanks, it´s more clear now, but for example, what will happen if I set the roll off in 16hz or 888hz.

I usually record metal shows, which setting will be the best?

Offline willndmb

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Re: Newbie Question: Roll Off
« Reply #4 on: May 10, 2010, 11:54:21 AM »
the lower the number the less thats is rolled off
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Offline jefflester

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Re: Newbie Question: Roll Off
« Reply #5 on: May 10, 2010, 05:19:02 PM »
thanks, it´s more clear now, but for example, what will happen if I set the roll off in 16hz or 888hz.

I usually record metal shows, which setting will be the best?
You would likely hear no difference at 16Hz and a huge difference (very lacking in bass)  at 888Hz.
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Offline realkuka

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Re: Newbie Question: Roll Off
« Reply #6 on: May 10, 2010, 11:22:54 PM »
Thanks, last question, has the roll any relation with the volume of the recording?

Offline darktrain

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Re: Newbie Question: Roll Off
« Reply #7 on: May 10, 2010, 11:43:02 PM »
Thanks, last question, has the roll any relation with the volume of the recording?

no

Offline realkuka

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Re: Newbie Question: Roll Off
« Reply #8 on: May 11, 2010, 12:09:37 AM »
thank you!

Offline M

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Re: Newbie Question: Roll Off
« Reply #9 on: May 11, 2010, 07:49:32 AM »
Thanks, last question, has the roll any relation with the volume of the recording?

no

I would say yes, only the frequencies that are being rolled off though but this will show up in the total RMS voltage (total power of the audio).  The whole purpose of a roll off is to lower the volume of certain frequencies.
« Last Edit: May 11, 2010, 07:53:15 AM by orestesluna »
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Offline jlykos

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Re: Newbie Question: Roll Off
« Reply #10 on: May 11, 2010, 08:54:38 AM »
For metal shows, I would start at 95 and work from there.  If 95 still has too much bass, move up to 107.  If it is too little, go down to 69.  160 would remove too many low frequencies while you would probably not see much of a difference from no rolloff at 16.  Just IMO.
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Offline acidjack

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Re: Newbie Question: Roll Off
« Reply #11 on: May 11, 2010, 08:59:37 AM »
^^^ Agree w/ jlykos.

TS.com standard wisdom is "don't use rolloff, do it in post."  If you use a cardiod mic, especially a small one that probably doesn't pick up much bass anyway, that is probably right.  But if your recordings consistently have too much bass, IMHO it doesn't hurt to use a little roll off up front.  You seem to have the sound pros battery box rolloff system.  I'd say don't go much over 95 with the rolloff - "you can't put back in what you've taken out" - and even then, I'd only go that much if you use omnidirectional mics.  When I ran SP mics I usually used 69 or none with cardiods. With omnis, 95 max.  You can always do more bass rolloff in post; as jlykos points out, doing it up front will save time. 

The numbers are the bass frequencies below which the bass will be rolled off.  888 is quite close to 1000Hz which is really midrange-- this is very "audible" bass.  The farther down you go - 16 for example - you are talking about bass you can 'feel', which often comes across as the boominess that people find unpleasant in recordings, especially on weaker playback systems.

Metal shows probably have a lot of that.
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Offline Patrick

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Re: Newbie Question: Roll Off
« Reply #12 on: May 11, 2010, 11:04:44 AM »
Something to keep in mind when rolling off is the slope of the filer you're applying.  There is a huge difference between Low cutting @ 107hz with a 18db per octave slope compared to a 6db per octave slope.  The former slope will cut important bass information out of the recording; for a metal show, the "thump" of the kick and lots of the fundamental bass frequencies as well as some guitar are going to be removed.  The latter slope will likely just reduce room/wind rumble and clean up some sub bass that could reduce dynamic range especially when recording at 16bit. 

Most microphones made for taping can handle intense amounts of bass, it's the recording medium and playback signal chain that can reveal too much bass causing people to cut higher than needed.  It's easy to take a little bass out during post work, but if it's going to save your recording by filtering at the show, then do it.   
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Offline aaronji

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Re: Newbie Question: Roll Off
« Reply #13 on: May 11, 2010, 12:41:56 PM »
The numbers are the bass frequencies below which the bass will be rolled off.  888 is quite close to 1000Hz which is really midrange-- this is very "audible" bass. 

Not just bass, either.  The A above middle C on a piano, if I recall correctly, is 440 Hz.  So 888 Hz is a touch higher than the A an octave above that.  Something like 2/3 or 3/4 of the keys on a piano are below 888 Hz...Even at 195 Hz, you'd be rolling off a lot of keys...

Offline fmaderjr

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Re: Newbie Question: Roll Off
« Reply #14 on: May 16, 2010, 01:56:01 PM »
WARNING: Knowing how much roll off you are getting from a battery box can be very tricky. You can easily get way more than you meant to unless you know how it functions with your recorder.

The old Sound pro's battery boxes produced the listed roll offs only if going into a recorder input with a 10 Kohm impedence (Sony MD mic in) and it probably is still that way.

If the impedance of the recorder input is 50% higher (R-09HR line in), the roll off is 1.5 times of the amounts listed.

Most of the recorders we commonly use today have mic in and line in impedences over 10 Kohms and you will get more roll off than the listed amounts. Sometimes way more (R-09HR mic in is 30 Kohms and would produce 3 times the listed roll offs).

You have to know the impedence of your line in or mic in (which are usually different for a given recorder) to know how much roll off you are getting.
« Last Edit: May 16, 2010, 06:07:11 PM by fmaderjr »
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