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Headroom

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greenmachine

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There was a question about headroom and the dB scale from 'MDnewuser' before the 'accident' happened. He asked me to mail him the dBscale for the NH700, which i've tried but couldn't reach his email address and got a Delivery Status Notification (Failure) message instead. So i'll bring it up here again. Maybe he'll appear here and repeat his specific question.

Anyway, here's the scale, taking level 30/30 as 0dB reference:

Values below approx. level 10/30 are of no practical use and increasingly inaccurate.

30 / 0dB

29 / -1.80

28 / -3.61

27 / -4.18

26 / -5.97

25 / -7.77

24 / -9.57

23 / -10.14

22 / -11.94

21 / -13.74

20 / -15.54

19 / -16.11

18 / -18.10

17 / -20.08

16 / -22.06

15 / -24.05

14 / -26.02

13 / -29.59

12 / -30.97

11 / -32.96

10 / -34.95

09 / -37.94

08 / -40.95

07 / -43.92

06 / -47.84

05 / -51.80

04 / -57.67

03 / -61.48

02 / -65.26

01 / -72.91

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greenmachine: thanks, as stated in the other thread bass and drums are the biggest threats when recording, it isnt easy setting a recording but from own experiance if its amplified around 25-26 (-6DB) is quite safe. I do a lot of testrecordings to get ready for the real stuff, that a good way to learn your equipment. Would like more experiances with levels, which settings do you use ?.

Edited by MDnewuser
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It totally depends on the sensitivity of your microphones what settings suit you best for certain locations. All you can do is to experiment. The scale is just useful for comparison. If you have used 15/30 in a certain location for example, have peaks at -20dB and want to have peaks at -6dB next time recording under the same circumstances, you'll use 23/30 to amplify by roughly 14dB according to the scale. (24-10dB)

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greenmachine: done quite a lot of experimenting, my conclusion is with 26 sound lack of presence (a lot under 0) and 29-30 is too loud (levels over 0), so only 27-28 is left, any hints how to test these two and see which is best ?. Also another question. 18/30 is unity gain, which means that there is no amplification, i imagine its ideal when transferring old cassette tapes and vinyl records. Good idea ?.

Edited by MDnewuser
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Believe it or not, there is no all-round best level setting for recording from different sources, you need to set it everytime anew. If you use 27 or 28 is of very low importance for the resulting sound quality - as you can see in the scale, there's only approx. 0.6 dB difference - really negligible. It's usually better to leave some headroom, the theoretically possible dynamic range is hardly ever fully exploited anyway - in the worst case you'll get a slightly worse S/N.

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The proper setting depends absolutely and completely on your microphone. Other users' settings are irrelevant to you unless you are using the same microphones.

Unity gain is theoretically what to use when recording from prerecorded sources through line-in. But again, it depends on what you are recording from and what the volume is that is coming out of your source--if you have it all the way cranked up, unity gain might overload.

You need to think about which will provide the cleaner signal: the output of your prerecorded source or whatever amplification the MD can provide. For instance, if I was recording from a stereo with a good amplifier, I would use the stereo output and unity gain, playing with the stereo volume control until 18/30 shows the peak level below overload (i.e., between the two dashes). If I was recording out of a cheap cassette recorder, I might want to use 20-22/30 and play the cassette a little more quietly. The level is what's important--not too quiet, not overloading--rather than the numbers.

Recording from prerecorded sources is usually simpler than recording live sound because the prerecorded sources, particularly vinyl LPs, are usually compressed--that is, they don't go to extremes of loud and soft. So you can usually find a comfortable setting and leave it. But that setting will be different for each LP.

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There are two major enemies when recording: On one side clipping, which occurs suddenly if your peaks exceed the 0dB mark. On the other side of the usable dynamic range there's noise. It doesn't occur suddenly, but the lower you set the average recording level, the more noise you'll have after normalizing.

The engineer's ideal has always been to have peaks as close as possible to the 0dB mark, but not over. It's usually better to leave some headroom than to get clipping, the dynamic range of 16 bit recording formats like (Hi-)MD is large enough not to have your recording ruined by noise even if you set your levels somewhat too low.

I usually try to get average peaks between -12 and -6dB for live recordings, just in case that anything unexpected happens. The more dynamical the source, the more difficult it'll be to set levels properly. The best thing to do is to practice and to get to know the sensitivity of your mics to be able to predict an approximate setting for each location.

If you record from other media like tape or vinyl, it should be easy to find peaks and set the levels accordingly before you start the recording. A minimum of headroom is adequate there.

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  • 2 weeks later...

A question, if you visit an acuostic gig where you know drum/bass is out of the picture should is it wise to use some headroom for handclapping and screaming in the audience ?. I can see when i playback in Soundforge mostly "audience-noice" hit those high peaks (clipping). Can it be harmful to recording ?. Got around -6 when using 28/30.

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How are you recording? Mic to mic-in? Mic to battery box to line-in?

28 or 29/30 is a lot of amplification from the preamp. If you're going through mic-in with something that quiet, then I hope you're not using any attenuator, and you should check under REC SET to use HIGH SENS rather than LOW. (It won't matter with line-in.) Perhaps you're using a low-sensitivity mic.

Whether you should leave headroom: yes. The mics and MD don't care if the loudest sound is music, handclapping or low-flying helicopters

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A440: RS Auris to battery box to line-in, i saw in other songs that peaks were just under 0, but i missed that "direct sound" greenmachine were talking about in the other thread i sat on 8th row still close to the stage though.

I were in a church today trying to sit a bit closer to the stage, i will listen how it came out later if it got any better or if cards would be a better choice.

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  • 2 weeks later...

Ok, just got my new mics, they are Omnidirectional Powered Stereo Mics from Giant squid - they have pretty dam low sensitivity, and I would like some opinions.

Sensitivity: -44 decibel +3 decibels - they have a linkwitz mod and I am using a battery box! I am recording through line in!

So I did some tests around the home, hooked the mics on my shirt, and cranked up my home stereo and sat in front of the speakers, pretty loud, but not as loud as a rock concert the type of recordings I would like to make, I adjust the REC LEVEL settings and started playing, and even with the level set to 30 I could only get the bars to 4 on each side peaking with the odd pop between the dashes, on my RH10. These aren't gonna be too low sensitivity are they? The results sound pretty good, I have to crack up the volume but it sounds good, I could always normalize the recording after anyway right....so really just wondering 4 bars on 30 isn't too much of a worry from a home stereo is it, if I am wanting to record loud concerts!

And also, if 30 is giving me 4 bars from a stereo, 30 is pretty much gonna have to be what I use to record a concert right?

Just a newbie that wants some reassurance, Cheers!

Also, I noticed that the right side is a little more sensitive than the left, is this just the music that I am recording and the sounds coming out of each channel or is one mic likely to be a little more sensitive than the other and is so that’s not too big a deal is it?

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And also, if 30 is giving me 4 bars from a stereo, 30 is pretty much gonna have to be what I use to record a concert right?

Close to impossible to predict, it could be significantly louder and you would have to use a lower level setting, you should get used to set levels according to the meter once you're there. With some experience you'll get to know the sensitivity of your mics and the behavior of the level system soon and will be able to predict level settings according to different sources if needed, but in the meantime you need to gaze at the display as often as possible. Try to get average peaks around the -12dB mark (left dot) and don't ever let it reach the right dot (>0 dB - clipping).

Also, I noticed that the right side is a little more sensitive than the left, is this just the music that I am recording and the sounds coming out of each channel or is one mic likely to be a little more sensitive than the other and is so that’s not too big a deal is it?

The mic elements come with rather large tolerances out of the factory. It's the mic builders' job to find two matching pieces. The more exactly he works, the less channel difference you (the end consumer) will experience. Can you express it in dB? For me, anything above ~1-3 dB is intolerable (depending on the price).

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The mic elements come with rather large tolerances out of the factory. It's the mic builders' job to find two matching pieces. The more exactly he works, the less channel difference you (the end consumer) will experience. Can you express it in dB? For me, anything above ~1-3 dB is intolerable (depending on the price).

The mics were $80US with a battery box! Not that expensive at all, and the guy did the Mod for me for free too, so I am pretty happy!

I can't hear the difference between the channels, on the level meter on my RH10 I just noticed that the right side goes up a bit before the left, never more than one bar above it, and only briefly, they are normally the same though, just when the sound increases the right bar jumps up first! How can I express this in db?

So back at your other comment, so your saying about 4 bars is ideal with peaks at about 5...and never going up off the end? I thought you were meant to have it on 5 ideally! 4 did sound pretty good though, I would be happy with that! Then normalize after for listening purposes!

Cheers

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I can't hear the difference between the channels, on the level meter on my RH10 I just noticed that the right side goes up a bit before the left, never more than one bar above it, and only briefly, they are normally the same though, just when the sound increases the right bar jumps up first! How can I express this in db?

You could analyze it in an audio editor after upload, but it's propably nothing to worry about, propably within the 2 dB range and considering the price including the SF mod it should be a good deal indeed. If the slight difference worries you, you can equalize it in an audio editor anytime.

So back at your other comment, so your saying about 4 bars is ideal with peaks at about 5...and never going up off the end? I thought you were meant to have it on 5 ideally! 4 did sound pretty good though, I would be happy with that! Then normalize after for listening purposes!

See post #9. If you run your levels 'hot' or prefer to stay on the safe side is up to you, just try to avoid clipping without setting it way too low.

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  • 1 month later...

greenmachine: thanks for the advice, -12 was good enough it only reached -4 never 0. Now i have really seen how unpredictible amplified music can be, ashame it isnt always that easy to pull the MD out during a concert i set it low from the beginning.

I used and old MD, so now iam thinking of the best way to transfer it to computer. Soundcard seem to add "noise" so i am thinking of copy it to Hi-MD and from there to computer instead

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