Improving GH1 audio: GH1 audio conditioner

shaveblog said:
I'd bet dollars to donuts the iPhone/FiRe trick sounds lots better than any external mic that has to go through the GH1's audio chain.
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Why would a cell phone sound recording be any better than the GH1 with options for any kind of external mic with att pads and mixer to accompany? That seems like a stretch, doesn't it...?
 
It's not a cellphone sound recording. It's a high quality electret mic capsule, a decently clean audio circuit with no AGC and full frequency response (2 things the GH1's mic input evidently lacks), and a software based audio recorder with flash based storage. That's what the FiRe app turns the iPhone into. It is not a recorded cellular voice call. It's essentially a mono version of the Zoom field recorders.

Listen to the audio on the Vimeo clip. That's an iPhone sitting on a table between 2 people speaking. Does that sound like a cellphone sound recording to you?

Hey, use the info if you want, or don't. It's a trick I use all the time on gigs and it always works great, especially considering it cost me five bucks. But if anyone would rather pad the GH1's mic input and deal with AGC noise floor pumping and what looks like a pretty ragged frequency response, by all means use what works for you.

If anyone with an iPhone 3G, 3GS or 4G wants to try this trick for free, you can download a free version of the FiRe app called BlueFiRe, which lacks input level control but otherwise has the same functionality and sound quality as the $5 FiRe app. Run the app, hold the iPhone like a mic and say something pithy. Upload the 16-bit 48KHz AIFF file to your computer, and then you can listen for yourself.


PappasArts said:
Why would a cell phone sound recording be any better than the GH1 with options for any kind of external mic with att pads and mixer to accompany? That seems like a stretch, doesn't it...?
Click to expand...
 
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shaveblog said:
It's not a cellphone sound recording. It's a high quality electret mic capsule, a decently clean audio circuit with no AGC and full frequency response (2 things the GH1's mic input evidently lacks), and a software based audio recorder with flash based storage. That's what the FiRe app turns the iPhone into. It is not a recorded cellular voice call. It's essentially a mono version of the Zoom field recorders.

Listen to the audio on the Vimeo clip. That's an iPhone sitting on a table between 2 people speaking. Does that sound like a cellphone sound recording to you?

Hey, use the info if you want, or don't. It's a trick I use all the time on gigs and it always works great, especially considering it cost me five bucks. But if anyone would rather pad the GH1's mic input and deal with AGC noise floor pumping and what looks like a pretty ragged frequency response, by all means use what works for you.

If anyone with an iPhone 3G, 3GS or 4G wants to try this trick for free, you can download a free version of the FiRe app called BlueFiRe, which lacks input level control but otherwise has the same functionality and sound quality as the $5 FiRe app. Run the app, hold the iPhone like a mic and say something pithy. Upload the 16-bit 48KHz AIFF file to your computer, and then you can listen for yourself.
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Why would I use an expensive iPhone to record audio for the GH1? How do you take phone calls during the recording? Oh, now I get it, you're trying to sell something...

Randy
 
Really? That's your response? I'm just trying to share a cool trick for guys who already own an iPhone, and one guy says huh why record a cellphone call and the other thinks I'm recommending buying an iPhone just to record audio?

Either you guys are hazing a newcomer or you're being rude. Help me out here, which is it?
 
Blue Fire is free, just tested it for the first time and it does sound great. Excellent for a backup audio recording device.
 
Matthew P said:
Wow, that's quite a good device there! The results certainly speak for themselves!


Yet another testimony that DIY rules. If this was built by some company specifically for DSLRs, they'd sell it at a rip-off price like they've been doing with so, so many 'enhancements'.



Talk sense. This probably cost £6 ($10) to make. This is probably more practical too because you a) don't need to worry about pressing record on the external recorder, and b) don't have to sink up in post, which can, although easy, be a bit of a pain.
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Why on EARTH would you want to record into the GH1 with no proper phantom power, no proper preamp, and compressed audio? Even if this device did fix what it says it does, you are still left with two other MAJOR problems, and you are tethered to the camera for moves, steadicam.. ect....

Syncing is very easy. Write the # of the audio file on the slate... when you go to edit, just drop that file into the timeline, there are now even programs to find the clapstick slap and auto sync.
 
The best deal on the block is a Zoom h4n modified by oade brothers or someone similar.
The a/d converter in the zoom H4n is very good, the preamp is very bad, if you know anything about electronics you can change the preamp to a very good one and it sounds amazing, if you don't, you can have someone do it for under $100 normally depending on the preamp.

If you have the $$$, get the sound Device 702 or one of those series... the preamps and recording are just insane quality, but we are talking $2000 and up just for the recorder... if you need a 4 to 6 channel mixer things can really get crazy.

For low budget gigs, a modified zoom h4n is fairly amazing. The preamp it comes with sounds like cardboard though.

I have to find my old recordings, but here is an unprocessed 24 bit take with the NEW preamp:

MIND you, this is a $1500.00 sanken cs-3e mic. King of dialog mics to my ears. This was ina VERY echo noisy high school hallway, and the mic pulled them out beautifully, while the 416 sounded like kaka. This is the sanken cs-3e going directly into the modified zoom h4n, not through a mixer:

http://blackout.com/clients/teenage_wasteland/MONO-041.wav

After post processing and compression, what you have is pure movie audio beauty...
 
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Blackout said:
Why on EARTH would you want to record into the GH1 with no proper phantom power, no proper preamp, and compressed audio? Even if this device did fix what it says it does, you are still left with two other MAJOR problems, and you are tethered to the camera for moves, steadicam.. ect....

Syncing is very easy. Write the # of the audio file on the slate... when you go to edit, just drop that file into the timeline, there are now even programs to find the clapstick slap and auto sync.
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I record audio to my GH1 for several reasons. I want some sort of audio backup in case my audio recorder fails for whatever reason. Also for situations where I don't have an external recorder, it happens and I want to maximize the quality I can get with the GH1 in those situations. I also want to sometimes edit right away without having to do any audio syncing which might happen with a client and then after the client leaves I'll sync/insert the audio from the audio recorder.

It's also great for making quick DVD's of the raw video/audio which I can do from my Panasonic Blu-Ray player with an SD slot and play the GH1's SD card into a DVD recorder. Simply impossible to do without recording audio to the GH1 at the same time.

I can go wireless from my audio mixer output to the GH1 so that I'm not tethered and remain completely mobile with the GH1. Since I have an audio recorder attached to the audio mixer, going wireless and losing a little quality there is not that critical to me. Having some sort of audio backup is. One scenario I can think of is with cell phone/blackberry RF interference buzzing noise which can happen. when it does on my main audio recorder I can see if it happened on my GH1 audio and if not I can splice in that audio in to cover where the RF noise occurred on the audio recorder.

So how do you eliminate echo from audio/narration? Not one audio expert I know of has an effective answer for that problem. You should post the "processed" audio WAV file so we can hear the difference.

By the way, you can't knock the 416 mic since it's a shotgun mic and not designed to be used indoors. From audio pro Ty Ford:

"With all due respect. The only reason I'd use a 416 indoors is if I didn't have another mic. Or if the acoustics of the room allowed it. I've used the David Letterman example many times before. You can use a shotgun on an interview show because the set has no walls and the ceiling is 30 feet up and probably treated. 6-8' away from your target while shooting in most average interiors will provide a washed out and distant track for which there is currently no plug in to fix.

If you're inside and can't get closer than 18"-24" with a super or hypercardioid, go to a lav."

Here is a "what mic to use" tutorial video he did which includes the 416:

http://gallery.me.com/tyreeford#100038

Randy
 
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Cave, what I meant was, if I could only have one mic - it would be the sanken cs-3e.... it has the best ability to focus on exactly the dialog and reject off axis without making things sound weird, and it works well inside or outside - I guess because it is a super Cardiod, not a regular shotgun.
Did you listen to the sample? I think the voices are dramatically clear and the echo, what little there is, is totally natural for the location, which is a high school hallway. You wouldn't want to remove all the echo, then it would sound like a lav and be totally unnatural for the scene, however with a 416, it sounded totally echo filled. I soly my scheops after I got the sanken cs-3e because there wasn't really a point in having it.. I am not usually shooting in a perfect studio... usually on real locations...

The only post processing I do is to compress the voice to bring it up usually with a waves L2 or that flavor of compressor.. sometimes take out low end rumble, and perhaps some noise floor removal if it's a problem, but I lay down room tone anyway.. you don't want to remove that.
 
See http://www.dvxuser.com/V6/showpost.php?p=2058837&postcount=75 for my analysis of how the GH1 limiter works.

Given that it's an "intelligent" limiter changing its characteristics to suit the nature of the incoming audio, applying a high frequency tone while at the same time recording normal audio might lead to undesirable results. For instance, a music signal might be over-compressed, or clipped.

I would suggest careful testing of the consequences of the technique with a good pair of ears as well as test kit. It should be possible to get some idea by simply mixing a high level 16kHz tone with lower-level speech or music replayed through loudspeakers into the GH1's own mic, before going to the lengths of getting out the soldering iron. Just don't upset the dogs.
 
Addendum - I just tried that (tone mixed with music via loudspeakers into GH1 mics) and it works, though I'm not sure I could conclude a great deal about the result. Just running a 16kHz tone out of the speakers on its own seemed to achieve a level reduction in a speech recording (in other words, I talked for a little, then turned on the tone, then talked some more, then turned off the tone) but oddly, no change in room noise when I turned the tone on or off. That's what I mean about results from this technique not necessarily be what you'd expect.
 
I can hear change in speech and room noise. Strange. Maybe you mixed some of inner GH1 signals (it is relatively loud around 82Hz) with room noise?

OK, I have made measurement of frequency characteristics. It is the following: Audio gain is more or less constant in frequency range from about 500Hz-14kHz. Lower frequencies are slightly attenuated till about 50Hz (-3dB). Attenuation at lower frequencies is higher.

Similar happens when using attenuator with external high-frequency signal, except that the overall signal level is lower. I noticed slight reduction of signal amplitude around 70-80Hz for about 2-3dB. The rest of characteristics is similar.

It is also very interesting that there exists some very efficient filter which cuts all the frequencies above 14kHz. At 16kHz, the signal is already reduced by 20dB, and at 18kHz it practically vanishes.

So, to sum up: Frequency response is between 50Hz and 14kHz in both cases.
 
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