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Find me! Call DAP at 214.350.7678 or email rene@dallasaudiopost.com. Also check out echocollectivefx.com for custom sfx, and tonebenders.net for my podcast.

Tuesday, December 28

Distant train extraction

So while I was out recording footsteps on rubber tracks and revolving metal turnstile doors this past weekend I managed to catch a pretty solid distant train as I was walking from one place to the next. I had heard the train a few minutes before, so I kicked on the prerecord buffer in my D50 and started walking towards the track that was a few hundred yards away.

Sure enough that train got closer and started blowing its horn. Here's the raw audio I caught - notice that you can hear me stop walking, turn and click the record button since the prerecord buffer was on. Also note the amount of wind I had going on there.

Distant train by Rcoronado

when i got back to the studio I was pretty disappointed with the amount of noise in the file so after noodling a bit I chalked it up to a swing and a miss. Regular Izotope eq and noise reduction was just leaving too many artifacts. Right before I deleted the file I decided to try one more thing on a whim: sample the train and use the tonal noise reduction algorithm to listen to the noise only.

At this point I wasn't really trying to clean up the file anymore, I was just playing around with the tools. What I got was pretty remarkable in terms of clean audio though, so I'd like to detail what I ended up doing:

The beautiful thing about the way that Izotope RX works is that it is very flexible and able to be tailored to any specific type of processing. Most other desnoising programs don't have separate controls for tonal noise vs broadband noise, and this feature really sets RX apart. I highlighted a clean section of the train whistle and used that as my noise print, then I clicked the "output noise only" box at the top right. At first I experimented a bit with bending the noise reduction curve to accentuate the train tonality and ignore the rest, but the result was a lot less natural than just the flat line there, so I left it at that.

I kicked the tonal reduction up to the max and the broadband reduction down to zero, but again that felt a little artificial so I dialed a touch of the broadband noise back in to smooth the edges out.

I actually went through this process twice, which yielded very good results.

The denoiser didn't do much for my wind and general city traffic tone though, so I ran a linear phase highpass just under the tonic note of the train whistle, and I ran it pretty steeply. That lopped off the bottom end and left me very clean.

What was left was peaking out around -30 or so, and I added about 12db of gain back into the file because I can. This is why we always record at 24 bits. :)

The end result looked and sounded like this:

Distant train-extracted by Rcoronado

I went from having something completely unusable from an impromptu recording to having something that I could layer in with some traffic (to taste this time) and have it sell. The artifacts aren't the ugly glassy things you normally get with noise reduction software either. They sound much more like an expander working, which is something you can get away with much more easily.
also, all of the reverb pretty much stayed intact, which would never happen if I hammered that with broadband reduction.

This kind of thing is pretty specialized though, as it probably won't ever work on things that aren't both harmonic and static. For things such as horns, alarms and sirens heard in noisy cities though, its pretty darn interesting.

One strange side effect came at the end, when my voice kind of vocoded against the reverberating distant tones of the train. I really didn't expect that, but I'm curious now about how to exploit it. I guess recording someone's voice while playing a static synth tone in the same room would do it, but it may also cost me friends. :)

Monday, December 27

found sound-metal turnstile

While out exploring and looking for a rubber track to record some footsteps this week I came across a little elementary school in suburban Mesquite, TX that has the potential to really be a sonic gold mine.

It's several miles from any highway and surrounded by a sleepy neighborhood with decent building cover, so the traffic noise is pretty minimal as settled areas go. It also has a wealth of surfaces - thick wood, grass, dirt, a tennis court with basketball rims at either end, and of course my coveted rubber track.

I found this school the day after Christmas so it was pretty deserted at the time. (side note, Christmas day is an ideal recording day. Downtown Dallas looked like some post-apocalyptic movie with all of the empty stillness. I will be rolling next year...) The track was surrounded by a chainlink fence that had a metal turnstile entryway to it. As I walked through the turnstile towards the track I knew that I wouldn't be able to walk back out without recording it.

I'll let the video do most of the explaining, but the bottom line here was that it was pretty loose at the top joint and made this crazy rattly ringy jackhammer sound when I spun it. In this vid my voice is recorded with the iphone mic and the turnstile is recorded with the Sony PCM D50.

Metal turnstile from rene coronado on Vimeo.

pretty crazy. Here's what it sounded like at 20%:

Revolving metal gate-20percent by Rcoronado

Even though I now know exactly where this metal gate is, I had to record it right then and there because I've learned through experience that if you let a recording pass you by you may never get a second shot. I do plan to return here though, if only to do exterior foly. I need to find out who the groundskeeper is. :)

Sunday, December 26

HH shootout part 3-parting thoughts

This post is just a wrap up of the handheld shootout.

I did the tests because I wanted to find out for sure a few of things:

1: how did the internal mics and other features of these recorders stack up against one another
2: how do they stack up against an industry standard setup
3: when can I opt for the cheaper and more convenient option over the more expensive and time consuming one?

Here's generally how I interpret the results of what I found:

Sony PCM D50:

This unit costs 1.5x what the others do, but lacks some of the features and xlr inputs. So what are you paying for? Design and build quality.

The D50 is the only device made of metal, with all metal switches, jacks, and mounting threads. Its built like a tank, and sounds great. The limiter is the best of the bunch, the preamp knob feels great, the mics swivel and are protected with metal bars, there's 4 gigs of storage built into the device, and all of the most important functions are available without resorting to menus. The battery life obliterates that of the other devices, and the size isn't compromised at all.

Its designed to be 100% stand alone, so no XLR inputs. That's a pretty big bummer if you're looking for an alternative to a 702, but it seems to fit the mentality of the grab it and roll improptu recording device, which is where it gets most of its use in my world.

Tascam DR-100

This unit was a little disappointing IMO, but mostly due to missed opportunities. It has tons of switches on the outside, but only about 2/3rds of them are truly useful. I'd love to have seen a mono/stereo switch given how often I'm jumping into the menu to change that back and forth. The limiter is analog and pre a/d, but has an incredibly slow release time and is not adjustable. The unit is built from pretty sturdy plastic but plastic nonetheless and the XLR jacks could have been the neutrick dual use kind but are not. Also, the tripod mounting threads are plastic, which is a bad place to get cheap. The internal mics performed the worst of the three units, and I didn't bother testing the other "omni" mics that are included because I listened to them earlier and deemed them unworthy of competition in this specific arena. The unit has a proprietary Li-Ion battery that charges via USB and seamlessly switches to the AA backups, though the combination of the two still don't come close to matching the battery life of the D50 with its four AA setup. I'd have gladly payed another $100 for metal construction and switches, and neutrick dual use XLR jacks.

I'd only recommend this unit as a compliment to an external microphone, but in that capacity it handles the job well and could even serve as a cheap but effective backup recorder.

The Zoom H4n

This unit is the de-facto standard for dslr filmmakers. It's by far the most versatile unit. The internal mics are good enough for use, the XLR jacks are 1/4 compatible which is great for my contact mics, and this is the only unit that can record 4 channels at once (2 from the internal mics and 2 from the XLR inputs) This makes the H4n ideal for performance recordings where one has access to the soundboard. Just run the board mix into the 1/4 jacks, mount the device where the built ins can catch the crowd and you're good. I've used it in this context before to great effect, but there is one serious caveat here - power. The power in theaters and clubs is notoriously dirty, so if you can't take a clean feed without resorting to batteries be prepared for a long night because thing sucks batteries like crazy. The switches and jacks are plastic but pretty sturdy, and the tripod mount is metal. My unit has a nasty habit of telling me that there is no SD card until I reboot it sometimes, so be on the lookout for those type of quirks as well.

Overall its a sturdy unit that is more versatile than any other out there. It is competent at everything it tries to do, but take the battery thing seriously with this unit. Two AA are not enough.

Thursday, December 16

handheld recorder shootout-part 2-listening test

Here's part 2 of the HH shootout - the listening test!

In this shootout I'm comparing the internal mics of the Sony PCM D50, Tascam DR-100 and Zoom H4n from a sound designer and field recordist's perspective. For reference I'm also including a sound devices 744t with a pair of SM81s in XY position as a benchmark. Part 1 covering comparative specs is here.

I feel like I did a good job here of calibrating the various devices to get a good solid apples to apples comparison of how the built in mics, limiters, and preamps compare. Each of the audio samples in this post are 100% unaltered with the exception of editing the clips. Once the preamps were set I never moved them for any of the tests. All are downloadable in full 24 bit 96k from the soundcloud links. If anyone is willing to host the longer unedited recordings I'll gladly post a link to those here as well.

Setup on all devices was as follows:

low cut - off
limiter - on
preamp - calibrated to 70dB spl = -12 dB fs
mic positions - as close to one another as possible

The way I calibrated the preamps was to hold them at mix position and blow pink noise through the studio monitors at 70db spl, then adjust the preamps until the noise was peaking at around -12dbfs.

This step in itself was pretty instructive of what the devices are capable of and where they are happy in the recording zone. The D50's pre was set near 6, the DR-100 between 8 and 9, the H4n was set in the 90s, and the 744t was nearly wide open with the SM81s attached. The amount of gain left in the knob after setting 70db pretty hot like that was pretty indicative of how much juice each of these devices had left to give.

The other enlightening thing was listening to how the different pink noise recordings related to one another. Now, the noise was obv colored by the speakers and the room to some degree on the way out so you can't really compare the recordings to pure pink, but the relationship to one another was pretty eye opening. Here's the side by side comparison:

Handheld recorder shootout-Pink noise comparison by Rcoronado

And here's what that looks like on a spectrogram:

To my eyes and ears the DR-100 seems to really have deep broad dips around 4k and up in the 15k range. It also doesn't seem to extend above 20k as readily as the others, which has 96k implications. This also seems to make sense given that 96k functionality was added after the product was released as a firmware update - implying that the mics really weren't designed to reach up near and past the top end of the human spectrum.

The D50 and H4n were pretty similar, with the D50 being a little brighter and the H4n a little fuller. No major deficiencies in either though, which is nice. Both were a little thin around 300Hz compared to the SM81s on the 744t though.


The next test was a self noise room tone test. This was done in the control room, which had an ambient noise floor of about 40-45 db spl. With the preamp gains up this high it was a very good test of what you're getting as far as cleanliness on the mics and pres.

Handheld recorder shootout-Room tone comparison by Rcoronado

Both the H4n and the PCM D50 had minor but audible hiss at those levels, and the high freq dips on the DR-100s mics mitigated the hiss fairly effectively, though that's not to say that they were capturing a very true sound.


Next was a voice test. I just talked for a little while with my head about 12 inches in and centered up in front of the devices. I've only posted the short clipped comparison here, but I can post up a longer clip on each of there's any demand for that. Here it is:

Handheld recorder shootout-Voice comparison by Rcoronado

The general theme here continues, as the DR-100 feels a little more lo-fi than the H4n and the D50, and all seem to lack the low end and low mids of the SM81s.


To get a feel of the stereo imaging of the devices as well as the foley recording characteristics I grabbed a bag and jostled it while walking from one side of the room to the other.

handheld recorder shootout-moving foley by Rcoronado

This was actually pretty interesting with regards to the stereo field because of how well the DR-100 performed with regards to imaging. Much clearer seperation than the XY setups, and no loss of the middle. Sound quality was still below the others however. The H4n started to differentiate itself here as well, with a better lower mid definition than the D50 when the bag was directly in front.


Now for some abuse - the limiter test! I did this test first by striking a piece of metal with a butter knife (which led to some interesting results), and then by striking a copper Noah Bell in the same manner. Listening to the bell ringout after jamming the limiters was pretty instructive here as well.

handheld recorder shootout-Limiter test comparison-metal clank by Rcoronado

handheld recorder shootout-Limiter test-noah bell by Rcoronado

Here its also useful to see what's happening in the waveforms:

The 744t has an analog prefader limiter that catches clips before they get digitized. You can hear it working in the samples, but its pretty unobtrusive when you consider how hard I was hitting it there.

The PCM D50 has a "dual path digital limiter" which records a recessed channel about 20 db lower and inserts that into the signal if the limiter threshold is passed. In my experience that sounds excellent on short transients and horrible if you catch wind noise that triggers the limiter.

The DR-100 seems to have a radio-style limiter in the analog domain that engages quickly and then spends about 2 seconds slowly (slowly) releasing out to regular gain settings. That's kind of the opposite mentality of the Sony since it would probably be less intrusive if consistently pounded, but it is definitely more intrusive when it just encounters one spike.

The H4n must have digital limiters and no protection on the analog front end because oh man that sounds ugly.


The next test is what these recorders are most useful for - outside ambiances. Unfortunately the wind protection I had on the SM81s was not adequate, so all you'll hear here is the handheld devices. This is just general traffic outside the studio side by side.

handheld recorder shootout-Outside amb comparison by Rcoronado

Each seems to do this job well. I've recorded mountains of ambiances with the D50 and H4n, and have used them consistently and successfully.


Last test is more of a demonstration than anything. Here I'm opening and closing the trunk of my car with the devices about 2 feet away. This is mostly to demonstrate just how much of the environment gets left into any recording you make with these. The pickup patterns are just so wide that if you hope to get something isolated while out in the world you should be prepared for how much of the world you're bringing back with you to the studio.

Handheld recorder shootout-Outside trunk comparison by Rcoronado


So there it is. Hope you enjoyed it. Happy shopping!

Tuesday, December 14


So anyone anxiously waiting for my HH recorder listening test is going to have to wait just a bit longer. I actually recorded the listening tests before writing the first article, but on review I discovered a flaw in the way I had one of the recorders set up, which means I'll have to re do it.

I think I can get the recording done this week, but the other thing I have going on in my life right now is sound for Benavides Born, which just made it into competition at Sundance and has a very tight deadline.

Fortunately, I've got another cool post brewing based on a truck we recorded over the weekend for the film. Stay tuned, more coming!