32 bit float: Zoom H1essential

rogerch · 2024-09-15T07:12:58+00:00

I've been frustrated with clipping in my recordings using my Zoom H4n pro. Most of my recordings are improvisations and I don't know ahead of time how loud I...

iternabe

My understanding is 32-bit float may not necessarily eliminate clipping during playback, at least not without some post processing. Clipping during playback happens when digital audio signal level exceeds 0 dBFS. What 32-bit float does is it preserves the details in signal above 0 dBFS - nothing is lost, which means in post processing, by reducing the overall level, clipping can be removed and details in the loudest part of the recording fully recovered.

Look it in another way, if you don't do any post processing, you still should set the proper mic level (gain) on the mic (pre-amp or recorder) to make the recorded file sound good (no clipping) straight out from the recorder. But, if you did not set the proper mic level, post processing can still save the day.

If you are going to do post processing anyway, another factor to consider about setting mic level is the noise floor of your recorder or mic pre-amp. Lower input level will cause the recorder noise sound more prominent during quiet passages. Raising mic level (without needing to worry about clipping) can mitigate this.

pseudonym58

rogerch I am wondering why you are encountering the clipping. I assume, perhaps incorrectly, that one of the advantages of digital recording in general, assuming decent equipment, is that you don't have appreciable background noise to deal with, and that as a result it allows you to record at lower levels without being concerned about the signal to noise ratio the way you would using audio tape, for instance. Why don't you simply lower the recording level slightly, so there's no danger of clipping to begin with?
Perhaps it would be interesting to do a "blind" test, whereby you record the same music at @ 24/32 bit and lower/higher level, and have someone else playback the two samples a few times in random order.
It may be that the differences can be readily appreciated by persons 30 years or younger, as hearing sensitivity generally degrades significantly after that.
If you can easily hear the difference yourself, then please accept my apologies for suggesting otherwise.

rogerch

pseudonym58 iternabe Thanks for the suggestions about setting gain on the H4n Pro. With more experience I might learn how to more effectively manage the gain setting on the H4n Pro. If the H1essential works out I won’t have to! 🙂

iternabe

To preserve the dynamics contrast accurately between pieces recorded at different times, I'd still advocate proper gain staging in all phases of creating the recording. Having all equipment and software setting fixed takes guess work out and ensures consistency.

Take the Zoom H4n Pro for example, you still want the signal out peaks at -6dB. H4n has a "REC LEVEL AUTO" feature that can help finding the proper mic level to ensure this. Enable it, put the recorder in recording standby, then play the loudest you think you'd ever play. The recorder will detect the loudest sound then set the mic level automatically so that the loudest sound will record at -6dB. Note the displayed mic level numeric value on the screen, turn off "REC LEVEL AUTO", then manually set the mic level to this fixed numeric value. As long as you don't change your recorder's position in subsequent recordings, keep this mic level unchanged.

Later in post processing, you can boost the audio level if you want the final recording to sound louder. If you did the step above correctly, you have 6dB of headroom to play with. Let's say you decide to make the peak of the final recording at -1dB - you simply increase the level +5dB from the original output of the recorder. However, the key is, you fix this +5dB the same for all of your recordings, not just the quiet ones. The goal is quiet playing should till sound quiet and loud playing still sound loud, and the contrast remain the same even between different pieces.

Now, with 32-bit float, what leeway you have is you can set the mic level higher, and reduce the level in post processing. One main reason to do this is to mitigate high noise floor in your recorder (a common problem for nature recording but less so for piano). Still, you want to keep mic level figured out, set and fixed for consistency.

The final question is what if you do all this, and the quiet playing part of the recording just sound too quiet when playback on a mobile device or in a noisy environment. Then you will need some level of compression to bring the quiet part louder. It's a personal decision, depend a lot on what your target audience and their listening environment is. Once decided, it's advisable to keep that part of your post processing workflow fixed as well.

pseudonym58

iternabe "...mitigate high noise floor in your recorder..."
Is this commonly perceived as a faint white noise or hum?

rogerch

iternabe The beauty of the H1essential, and I believe float 32 recorders in general, is that there is no gain setting on the recorder. It has such a huge dynamic range that gain is unnecessary. The trade off, as I discovered, is that the output level needs to be adjusted at playback time. A level still must be specified, but after the recording not during the recording.

iternabe

pseudonym58 Yes. And it is generated by the circuit inside the field recorder. When you change mic level, the amplitude of this noise is not changed.

So, let's say your recorder has a white noise of -45 dBFS. If you set your mic level very low and the real sound recorded averages -35 to -40 dBFS, then the white noise will be quite audible relative to real sound. If you set your mic level high so that real sound is recorded to be -12 to -6 dBFS, then the white noise (still -45 dB) become almost inaudible relatively.

In field recording of nature sound, this become a problem because you can turn up the mic level to max, and the recorded sound still won't be loud enough to overpower the white noise in the recorder. TASCAM field recorders are notorious for this problem. Zoom might be slightly better. SONY is much better hands down, but they are also many times more expensive for this reason.

rogerch

keff rogerch I used Audacity to make the audio recording presented to the PT recital and find it straight forward to use. On the other hand I can't get GarageBand to record as it seems it is not receiving input from an external microphone. In the end I discovered that my (cell) phone records reasonable quality audio as well as making the video image

Thanks @keff! I don’t use GarageBand for recording. The zoom recorders record to SD cards. I import the recordings from SD and use GarageBand to trim the recordings and convert to MP3

TLH21

It feels like there should be a 'technical' sub-forum/area for these sorts of discussions (e.g. recording, creating videos, sound-proofing, etc.). Not that this isn't super helpful, more that it would be great to have a defined place to go to find information.

rogerch

TLH21 Yeah I thought about that when picking a forum to post in. I chose Acoustic pianos because it seems to me that recording using an external recorder applies more to acoustic pianos than digital pianos. I know some players record their digital pianos with external recorders rather than directly from line out or directly to digital so it does apply there as well.

Emeton

rogerch did you try importing the file into Audacity? It automatically plays in 32bit float, might be perfect.

rogerch

Emeton Yes I figured out how to lower the output level in Audacity to eliminate the clipping. This is really cool! I love the huge dynamic range I can capture with this recorder without worrying about ruining the result with clipping!