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How can I get better audio quality for live rock recordings?

Posted: Tue Aug 13, 2019 12:16 pm
by peterp
I use an H2n in tandem with a video recorder for live rock (semi-loud, but not crazy loud) music recordings. The "video camera" is often an iPhone, and I use PluralEyes to replace the iPhone audio after the fact. The problem I"m having is that, believe it or not, it is very difficult to get audio quality that beats the native iPhone audio (iPhone 8+). I think I'm recording everything correctly in the H2n, so I suspect the problem is that I'm doing something wrong in post processing.

I have the H2n set to 44.1khz - 24-bit WAV for recording, manual gain control, gain set to proper levels on recordings, and I'm either using no limiter or sometimes "general" limiter (but I don't think the limiter is even kicking in because I have the recording level set correctly). The H2n is using XY mics about 15 feet in front of the small band area and in the same position as where the iPhone is recording.

Scenario 1: When I compare the raw H2n recording (without any post-processing) to the native iPhone audio, the H2n volume is lower (as you would expect without AGC), but when I "equalize" volume levels with Quicktime and YouTube volume sliders, the iPhone audio actually sounds slightly better with better frequency response.

Scenario 2: When I post-process the H2n audio with Audacity, applying only "compression" (default Audacity compression settings) and "equalization" (again default Audacity that boosts only the very low and very high frequencies), in that order, it is pretty much a tie with the iPhone 8+ audio -- there are some parts where the processed H2n sounds better, and some parts where the native iPhone audio is better.

I feel like the H2n audio should trounce the iPhone audio, but I'm not achieving that yet. I don't think it's the H2n (I actually think it records better than my H4n), I just think I'm doing something wrong.

My questions are:
1. What should I be doing in Audacity to get better audio results on moderately loud live rock recordings?
2. Is there something I need to change on the Z2n recording ("Input") settings to get better results?

Re: How can I get better audio quality for live rock recordings?

Posted: Tue Aug 13, 2019 12:41 pm
by Eldon Benge
1. What should I be doing in Audacity to get better audio results on moderately loud live rock recordings?

I would Normalize the file in Audacity before doing anything else. Apply EQ and compression after normalizing the file.


2. Is there something I need to change on the Z2n recording ("Input") settings to get better results?

Try to set the gain so that peaks are around -10dB while recording.

Re: How can I get better audio quality for live rock recordings?

Posted: Tue Aug 13, 2019 2:43 pm
by peterp
Eldon Benge wrote:
Tue Aug 13, 2019 12:41 pm
I would Normalize the file in Audacity before doing anything else. Apply EQ and compression after normalizing the file.
Thank you. I will try normalizing first, and then do EQ before compression (I did compression before EQ (and no normalization) previously)
Eldon Benge wrote:
Tue Aug 13, 2019 12:41 pm
Try to set the gain so that peaks are around -10dB while recording.
This I am definitely doing wrong. I would say my peaks were more like -6db or -4db. Would recording at my peaks impair sound quality? I would have thought that as long as you're well below 0db it's safe, but I see the owners manual also recommends having peaks at -12db. I can't help but be curious why the peaks need to be so low (-12db). I guess I also need to pay a lot more attention whether the XY/MS red LED is flashing.

I guess when I start targeting peaks of -12db, I can definitely run with limiter off without any fear of overload.

Re: How can I get better audio quality for live rock recordings?

Posted: Wed Aug 14, 2019 9:09 am
by Wulfraed
For use with video, 48kHz is recommended. It divides evenly into common video frame rates (24fps film, 25fps PAL, 30fps NTSC, 50fps PAL progressive, 60fps NTSC progressive)

DO NOT use AGC for music -- it loses the dynamic quality (it would boost gain during a quiet flute solo, and then, after a momentary overload, massively reduce gain during a kettledrum sequence -- or worse, you get pumping where it a slow drum beat causes gain reduction during the beat, with a boost between beats).

The -12dB target is common for video especially (all my cameras have a larger marker on the scale at -12dB). It provides enough headroom to allow for a sudden/unexpected burst (remember, even a peak-reading meter requires integration time, so a signal could still be higher than the displayed peak). In the days of analog magnetic tape, one would push the 0dB point, because tape didn't clip -- it saturated, so very short peaks going above 0dB were essentially "compressed".

24-bit depth should give enough dynamic range that you can post process with a bit of compression and level raising, followed by a noise gate to silence any parts that are really low level. You do, however, have to set the recording gain appropriately for the loudest expected part of the performance.

Digital realm limiters aren't really useful, in my mind (and on the older H2, useless -- on the H2, there were only three analog gain levels, separate from the "record level"; record level was a digital realm gain, as were the limiter/compressor, meaning any ADC clipping occurred before the limiter could have an effect*).

The H2n at least used a consolidated gain/record level, which appears to function in the analog stage (before the ADC). Limiter/compressor is still, I believe, in the digital realm, meaning they can not save you from analog clipping.

NOTE: per the H2n manual -- if you enabled "Auto Gain", then both comp/limit and "Mic Gain" have NO EFFECT. (Manual pages 69-70).



* On the H2, you HAD to set the 3-position GAIN to avoid clipping. It was recommended that one set the record level to 100 and leave it there (100 roughly translated to 0dB, less than 100 was digital attenuation, over 100 was a bit of amplification). My normal usage in a group guitar class was record level around 110, and comp-1 -- I'd found that comp-1 would lightly flatten the top range of loudness, and record level boost would then raise the entire signal back closer to -6dB.

Re: How can I get better audio quality for live rock recordings?

Posted: Wed Aug 14, 2019 1:37 pm
by peterp
Wulfraed wrote:
Wed Aug 14, 2019 9:09 am
For use with video, 48kHz is recommended. It divides evenly into common video frame rates (24fps film, 25fps PAL, 30fps NTSC, 50fps PAL progressive, 60fps NTSC progressive)
Great info! I've been in the habit of using 44.1khz from back when I was using it for a CD. I also used to use 88.2/24 instead of the much more common 96/24 for the same reason. I never understood why anyone used 96 instead of 88.2 -- now I get it -- it's for video. I will change my settings to 96/24 since I don't care about file size and want max audio quality.

I can't tell what frame rate the iPhone 8+ records in, when I use "get info" on the Mac on the iPhone 8+ video with original audio, it says 1920 x 1080, H.264, AAC, mebx, audio channels: 1, encoding software 11.2. On video with audio replaced with H2n/Audacity, the audio info changes to "Linear PCM, audio channels: 2, S/W Lavf7.56.100".
Wulfraed wrote:
Wed Aug 14, 2019 9:09 am
DO NOT use AGC for music ...
I never use AGC on audio recorders -- though to be perfectly honest, after listening to how good the iPhone audio is (which I assume is using some form of AGC), I have been somewhat tempted to try it as an experiment.
Wulfraed wrote:
Wed Aug 14, 2019 9:09 am
The -12dB target is common for video especially (all my cameras have a larger marker on the scale at -12dB). It provides enough headroom to allow for a sudden/unexpected burst (remember, even a peak-reading meter requires integration time, so a signal could still be higher than the displayed peak). In the days of analog magnetic tape, one would push the 0dB point, because tape didn't clip -- it saturated, so very short peaks going above 0dB were essentially "compressed".

24-bit depth should give enough dynamic range that you can post process with a bit of compression and level raising, followed by a noise gate to silence any parts that are really low level. You do, however, have to set the recording gain appropriately for the loudest expected part of the performance....
I get it now regarding -12db. My Canon camcorder has the same -12db recommendation, but I always thought because it was a relatively cheap video camera (I really don't care much about video quality, but I care a lot about audio quality). Even though I had the levels too high (peaks of -4db), I don't think it overloaded, so it doesn't sound like I could expect better sound quality even if I had limited peaks to -12db instead of -4db.

I didn't notice until looking at the iPhone 8+ file info on the Mac that the iPhone 8+ still records in mono. That makes it even more surprising that I'm struggling to get better audio with the h2n/audacity. I haven't tried noise gate, I'll try that.

Re: How can I get better audio quality for live rock recordings?

Posted: Thu Aug 15, 2019 6:39 am
by emmrecs
Just one comment:
I will change my settings to 96/24 since I don't care about file size and want max audio quality.
24 bit OK, but in my opinion (and experience) using 96kHz as your sampling frequency is going to double your file size with NO audio benefit! I assume you understand the basic theory of sampling frequency, that the maximum recordable audio frequency is exactly half the sample frequency? So 48kHz sampling gives an upper audio limit of 24kHz, and 96kHz sampling gives 48kHz audio limit. (The actual pitch difference between these two maxima is precisely one octave.)

However, your H2N mics are not capable of recording any audio frequency much above about 22kHz (at the very best) so much of what is "recorded at 96kHz sampling" is actually digital "noise", with no audio present. In addition, there is no known speaker or headphone that can actually reproduce frequencies much above about 25kHz, if that. Plus, you need to accept that, at best (i.e. for very young children) human hearing cuts off all frequencies above about 20kHz anyway (and that upper limit reduces as a person ages.)

Re: How can I get better audio quality for live rock recordings?

Posted: Thu Aug 15, 2019 10:03 am
by peterp
emmrecs wrote:
Thu Aug 15, 2019 6:39 am
24 bit OK, but in my opinion (and experience) using 96kHz as your sampling frequency is going to double your file size with NO audio benefit! I assume you understand the basic theory of sampling frequency, that the maximum recordable audio frequency is exactly half the sample frequency? So 48kHz sampling gives an upper audio limit of 24kHz, and 96kHz sampling gives 48kHz audio limit. (The actual pitch difference between these two maxima is precisely one octave.)
Good point. Dr. Nyquist would kick my *** if he saw me wasting all that file space :). I often record sessions that are 3 hours or longer, and the Zoom already splits those session recordings into 2 files with 44.1/24, so 96/24 would be even worse. Also Audacity does not cope very well with the first file that is maxed out in size at 2Gb before it splits (I now split out the audio files individually for each video with Plural Eyes and then apply Audacity individually to each song).

Will definitely go with 48/24 as you suggest. My dog is going to be upset about not hearing the 24khz+ transients out of my ribbon tweeters, but life goes on :).

Re: How can I get better audio quality for live rock recordings?

Posted: Thu Aug 15, 2019 10:29 am
by Wulfraed
peterp wrote:
Wed Aug 14, 2019 1:37 pm
I get it now regarding -12db. My Canon camcorder has the same -12db recommendation, but I always thought because it was a relatively cheap video camera (I really don't care much about video quality, but I care a lot about audio quality). Even though I had the levels too high (peaks of -4db), I don't think it overloaded, so it doesn't sound like I could expect better sound quality even if I had limited peaks to -12db instead of -4db.
What's a cheap video camera these days? Granted, I'm out of date as both of mine still use miniDV tape cartridges, but my "cheap" one (Canon Optura-40) was $800+ back in 2005 for standard definition (replacing a failed $900 Optura-20) while my good one (Canon XH-A1) was $3500 for HDV, using 3CCDs as I recall). Both have the -12dB large marker.

{confession: at the time Canon had three levels of consumer video cameras: entry, mid-range, and high-end -- the Optura were the high-end with larger sensors [better low light response]). And the XH-A1 is a half step below a low-end professional camera (it lacks the time-code sync of the XH-G1, which allows multiple cameras to embed the same time code into the video for later editing)}

Re: How can I get better audio quality for live rock recordings?

Posted: Thu Aug 15, 2019 11:19 am
by peterp
Wulfraed wrote:
Thu Aug 15, 2019 10:29 am
peterp wrote:
Wed Aug 14, 2019 1:37 pm
I get it now regarding -12db. My Canon camcorder has the same -12db recommendation, but I always thought because it was a relatively cheap video camera (I really don't care much about video quality, but I care a lot about audio quality). Even though I had the levels too high (peaks of -4db), I don't think it overloaded, so it doesn't sound like I could expect better sound quality even if I had limited peaks to -12db instead of -4db.
What's a cheap video camera these days? Granted, I'm out of date as both of mine still use miniDV tape cartridges, but my "cheap" one (Canon Optura-40) was $800+ back in 2005 for standard definition (replacing a failed $900 Optura-20) while my good one (Canon XH-A1) was $3500 for HDV, using 3CCDs as I recall). Both have the -12dB large marker.

{confession: at the time Canon had three levels of consumer video cameras: entry, mid-range, and high-end -- the Optura were the high-end with larger sensors [better low light response]). And the XH-A1 is a half step below a low-end professional camera (it lacks the time-code sync of the XH-G1, which allows multiple cameras to embed the same time code into the video for later editing)}
Mine is a Canon Vixia HFM400 I bought several years ago. I use it with the add-on Canon wide angle lens (which is a heavy well-built lens) and a Rode StereoMic. The standard battery will only record 1 hour or less, but I bought some maximum capacity aftermarket batteries on eBay that will record 4+ hours with each battery. I chose that model because finding a consumer-level camcorder with manual audio controls was literally almost impossible. Not sure about today, but back then only Canon had manual audio controls, and only on some models.

I didn't factor in video quality when choosing the Canon because I care far more about audio. I like that setup because I can just record with the the Rode Stereo mic into the Canon and not have to do any post processing, but the audio recorded in the Canon + Rode is still not that great. That camera (with lens & external mic) is bulky, so I often find myself recording with an iPhone for informal events. Except for the lack of optical zoom on the iPhone, the video and audio are shockingly close in quality to the Canon+Rode.

If I crack the nut on getting quality audio recordings out of the H2n, then maybe I'll get a new camcorder -- there will be a lot more options without having to worry about manual audio controls. I don't care about 4k, mainly because of file size, but I'd like to get something with better HD video quality and that is lighter.

Re: How can I get better audio quality for live rock recordings?

Posted: Fri Aug 16, 2019 9:03 am
by peterp
Eldon Benge wrote:
Tue Aug 13, 2019 12:41 pm
I would Normalize ...
As a 1946 Martin Committee trumpet owner, I'm obligated to ask: Any relation to Eldon Benge?

Re: How can I get better audio quality for live rock recordings?

Posted: Fri Aug 16, 2019 1:32 pm
by Eldon Benge
peterp wrote:
Fri Aug 16, 2019 9:03 am
Eldon Benge wrote:
Tue Aug 13, 2019 12:41 pm
I would Normalize ...
As a 1946 Martin Committee trumpet owner, I'm obligated to ask: Any relation to Eldon Benge?
No, but I have two LA Benge trumpets. :D

Way back in 1970 I auditioned for a music scholarship at what was then West Texas State University. The trumpet professor said, "You play well, kid, but this is a Benge section; you're going to have to ditch that Bach."

I lusted for a Benge for the next thirty-five years.

Re: How can I get better audio quality for live rock recordings?

Posted: Sat Aug 17, 2019 11:32 pm
by peterp
Eldon Benge wrote:
Fri Aug 16, 2019 1:32 pm
No, but I have two LA Benge trumpets. :D

Way back in 1970 I auditioned for a music scholarship at what was then West Texas State University. The trumpet professor said, "You play well, kid, but this is a Benge section; you're going to have to ditch that Bach."

I lusted for a Benge for the next thirty-five years.
Nice!! I have a few vintage horns, but no Benge (yet!)