Rode NT4 Into Everyone

So I turned to the wonderfully flexible Rode NT4 stereo mic as a source, installing the 9 volt battery that allows it to work without phantom power. Then I put together a chain of adapters to connect the mic to a Coleman Audio LS3. I bought this gadget years ago as a monitor switcher, but it also works as a passive distribution box for comparison tests like these. The LS3 gave me three outputs and another chain of adapters turned those into stereo mini plugs for the three recorders.

The mic, three field recorders, and the switcher

LS3 to 1/4" TS to RCA to Stereo Mini

Capturing the Tracks

As usual I “printed” or recorded a 1 khz test tone at the start of each recorder track. This is a snap with the single mic feeding all the recorders. I planned to create a set of tracks you can download in raw form as well as a set of level matched tracks, so I kept the recorders running while I moved the speaker and fired up my Martin OM-18GE, tuned to taropatch open G. I played a few hard strummed chords, some harmonics, then the first verse of “Sanoe” by Queen Liliu`okalani.

Here are those raw tracks. Please be very careful with your levels when playing these tracks, they contain loud piercing test tones than can hurt your ears and your equipment if played too loud!!

D50

H2n

H2

Level Matching Tutorial

I did some level matching on the clips and used the Licecap screen capture program from Cockos, the REAPER folks, to make a video of the process. I’m using the Sonalksis Free G Stereo meter on each track. This not only tells us the level on a fine scale, it allows precise level adjustment separate from the track fader and master fader. I find it indispensible for this kind of work. I also keep my monitor and headphone volumes down. Test tones can hurt your ears and your gear (second warning!) And I turn off snapping since we’re not dealing with beats and bars.

Here are the resulting clips. Remember, our brains love labels and they will affect what we hear based on those labels, so if you really want a clean comparison you need to use a double-blind testing tool like foobar2000 on the PC or abxer for the Mac.

D50

H2n

H2

What the Tails Tell Us

I’m usually not too concerned about slight variations in frequency response when I evaluate mics or recorders. I don’t want the recording to sound like it came through a megaphone, but minor colorations don’t seem to me to affect the emotional impact of the recording. I do listen for self-noise, though, because noise is a distraction, a mask over fine detail, and it breaks the illusion of “being there” that I look for in a track. So I often find myself listening to the “tails” of tracks when comparing recordings. For this comparison I went to the end of each track and selected an area after the last note had begun to decay, raised the level a lot, 12 dB, and rendered those for you.

D50

H2n

H2

Conclusions

There’s a look at our three recorders when used with an external mic. I’d say it’s pretty clear that the Sony tops the field here in low noise performance, and the H2 is bringing up the rear. In an earlier post I compared the H2n to the Echo Audiofire and was not too impressed, but now that I hear it in the context of other portable recorders, I’m much happier with the new Zoom. At least for the limited purpose of capturing solo acoustic guitar in a small room, the Zoom H2n is in the ballpark with the Sony. If your needs are more demanding, something like nature or sound effects recording, you may find that the Sony provides more clean gain, something I haven’t tested.

As usual when I do these comparisons I take a little trouble to get the clip levels matched. The more I’ve investigated audio the more I realize the importance of matching volumes. So for this comparison I used REAPER to generate a 1000 hz test tone and recorded it into all the systems. Then I used that recorded tone to adjust the volumes of the recorded tracks. This is more reliable than trying to match peak or average levels in the constantly changing energy of the music track.

Here’s a video that takes you through the process of generating these clips.

And here are the trimmed and volume matched clips for you to download and compare:

http://www.homebrewedmusic.com/audio/20110907/NT4.wav

http://www.homebrewedmusic.com/audio/20110907/D50.wav

http://www.homebrewedmusic.com/audio/20110907/H2n.wav

http://www.homebrewedmusic.com/audio/20110907/H2.wav

So how do those clips sound to you? When you go to the fadeout and turn up the volume, you should be able to hear a car go by out on the street, even though the window was closed. Listen to that section for the differences in the background noise.

The build quality, at least the “feel” of quality, certainly goes to the Sony in this comparison. It’s constructed of finely detailed metal, with firm precise switches and a solid hefty feel in the hand. Many of its features are are controlled by dedicated switches instead of relying on a menu.

The Zoom H2n instead feels light, even a bit cheap. Definitely constructed of plastic and with a minimum of dedicated external controls. The Zoom offers variable stereo patterns, but so does the Sony, using different technology. The Zoom has the advantage of a surround sound mode, and I also much prefer the “electric shaver” form factor of the H2 because it doesn’t require a stand and the metering is visible when the unit is in recording position. And of course there’s a substantial price difference between the units.

They both offer external mic and line in recording features, which I’ll look at in a future post.

External mics with the H2n

I rarely used external mics with my H2, but others at the Zoom forum tested and indicated that it is quite noisy. I’m open to the possibility that the external mic pre of the H2n could be a gem, with plenty of clean gain and headroom, but the only way to know is give it a try.

My first use of the external preamp was a test to see if the external mic could be used as part of the four channel recording capability of the H2n. In the four channel mode using internal mics, the front XY pair and rear MS pair each contribute a stereo file. I read an internet post indicating that an external mic could be used and it would replace the XY pair. This would allow 4 channel recording for other than surround purposes.

I was disappointed when I plugged in the Rode NT4 because it delivered a much lower signal level than the internal MS mics and there was no way to adjust the gain independently. I could record four channels, but two of them were much lower in volume than the others. I assumed (and you know what that means) that the NT4 was just low in sensitivity.

H2n Internal MS

Rode NT4 External XY

Today I tried again, comparing the H2n with the NT4 to a pair of Shure KSM141s into the Echo Audiofire Pre8.

Two Recording Tools

Here’s the mic setup I used.

Two XY arrays in tandem

Once again the level available from the H2n->NT4 was unimpressive. I don’t record hot, but these levels were down around -27 dBFS. By the time I added 9 dB of digital gain to get this track to match the ones from the Echo, the noise level was pretty severe. Here are the clips with matched levels:

H2n with Rode NT4 External

Echo Audiofire with Shure KSM141

Hey, looking in the docs actually turned up something. Input gain is listed as 0 to 39 dB, which is definitely on the low side. So unless there’s a firmware update that adds some gain without raising the self-noise, this external mic input is better suited to amplified concert tapers and drummers rather than acoustic guitarists. And it’s even worse news for folks interested in recording nature sounds and sound effects using external mics.

Line In on the H2n

I’ve used my H2 to record several shows by connecting to the PA mixing board. I find this is usually a cleaner sound than simply miking the room. I almost always have camera sound as well, so I can mix the board track with a room track. But the H2 has a serious weakness for my purpose – its Line Input is too sensitive for the outputs of a common PA mixer. The result is a horrible clipped mess. There’s no adjustment to reduce the sensitivity on the H2 and the tape outs on most mixing boards do not have a level control, so I’ve resorted to a passive attenuator, a simple ganged variable resistor which I use to cut the signal from the board to the H2.

I had hoped that the H2n would offer a solution. A built-in pad (fixed attenuator) would be ideal, or a wide gain range on the line input, with a low minimum sensitivity. Looking at the specs in the announcement, and then at the documentation, I found no mention of a more useful Line In connection. But a test was in order to see if things were improved.

I set up a comparison between the Line In on the H2 and the same on the H2n by connecting two hardware outputs of my Echo Audiofire Pre8 to the Line In on the two Zooms. I used an adapter to split the mono output to two channels. I adjusted the gain on the H2n to 0, there’s no gain adjustment for the Line In on the H2. To generate the test signal I used REAPER and created a 1 khz sine tone with a level of -18 dBFS – this is about 0 dBVU and should be a good starting point for evaluating a line level connection. When I checked the two Zoom recorders they were both clipped. I reduced the level and both recorders showed the same levels as they dropped below clipping.

My test tells me that the Line In on the H2n performs the same as it does on the H2, so I’ll still be bringing my passive attenuator with me when I record from the mixing board.

The first thing that jumped out at me – the new box is a lot smaller.

How'd they make the H2n box so much smaller?

Not the result of a breakthrough in packaging efficiency, I’m afraid. The reason is the lack of accessories. The AC adapter is missing, as is the mic clip adapter stick. These useful bits are now part of an extra cost accessory pack which adds $40 to the price of the H2n and includes stuff that I already have or wouldn’t use. Bummer, as we used to say in the 60s.

Not much in there, is there?

On the other hand, the AC adapter is a USB connector type, so maybe I have something around here that will work, and the long battery life makes the AC adapter less necessary. And I’ve collected a couple of mic sticks already, so for now I’ll skip the accessory pack. And I’m happy to see Wavelab LE7 in the package. Maybe I can get rid of my Adobe Audition and use this instead.

Look and Feel

The look of the H2n is cool black, the new screen is bigger and brighter. This is my number one reason for wanting the new unit – I can operate the menu without glasses. This screen is still pretty lame compared to the beauty they put on the Q3HD, though. The H2n screen is monochrome and pretty low in resolution.

Cool black vs classic silver

The menu is similar to the H2, but a bit simplified. The menu interface is simple and direct – a menu button takes you in and out of the menu, the playback paddle serves to select options. The buttons all operate much more easily and positively than those on the H2, but many of the H2 buttons are covered by a plastic skin which should add longevity even though it reduces tactile feedback.

SDHC card access is not quite as easy as the H2, it’s one of those uninspiring “flexi-hinge” covers and it’s pretty stiff right now. When I see one of these I figure there’s going to be duct tape on there someday. To be fair, plenty of people complain about the H2 hard plastic cover, and I’ve read reports of failure (and replacement with duct tape).

The battery compartment is a big surprise – the batteries both go the same way!! First time I can remember this configuration, usually two AA batteries would go opposite each other.

Operation

There’s no “Standby” mode as in the H2. The unit is listening and giving meter readings as soon as it’s turned on. Press the big red button all by itself on the front and you’re recording. Press it again and you’re not. Standby is a feature that has been part of recorders for a long time, but I know I am not the only one who missed many recordings because I only pressed the H2 record button once. I’m not sure which bit of technology made this new design possible, but I see it as a step forward, as soon as I can get out of the habit of pressing record twice – oh no!

Headphone monitoring can be turned off or turned on constantly, but the default is to have monitoring on at the home screen or while recording.

Files can be named with a date time stamp!!! No more hassles with duplicate file names when combining different recording sessions!!

The two obvious changes on the recording side are the level setting and the mic options. Instead of a three position analog “Mic Gain” along with a digital “Rec Level” control in the H2, the new recording has a continuous thumbwheel controller that is advertised as analog. My first impression is that the H2n offers much higher overall sensitivity than the H2, which will be a big benefit to nature recorders if the noise floor is adequately low.

The mic arrangement is interesting. There are still two mic arrays inside the H2n, but now there are five mics instead of four. A classic XY array (two cardioid mics at a 90 degree angle to each other, 45 degree angle to the source) points to the front of the H2n, as it does in the H2. The back array on the H2 is a pair of cardioids at 120 degrees, giving an option for a wider stereo field. In the H2n there are three mics in the rear facing array and they are combined into an MS (mid-side) configuration. This consists of cardioid mics facing opposite sides and in opposite polarity, so the two mics together emulate a single figure 8 mic at right angles to the source, while a single cardioid mic faces directly at the source and serves as the mid mic. The mid and side mics are then combined mathematically to yield a stereo field. The H2n can save either the decoded (stereo) or raw (mid and side separately) files, and it can be monitored in either mode as well. This is a nice bit of flexibility. In addition, you can adjust the amount of the side mic mixed into the decoded stereo file, changing the width of the stereo image. Visit the Zoom H2n site for a detailed explanation of the mic arrays and how they can be combined and adjusted.

I have this strong feeling that the real benefit of the mid-side (MS) mic arrangement is the marketing buzz it generates, but there are probably many users who will find a benefit in the ability to adjust the stereo width at record time. I’m guilty at times of seeing the whole recording world in terms of solo acoustic guitar, I’m afraid. I would add that the mic selector can be a bit difficult to adjust. It’s a small circular nob with a somewhat slick surface, so a slight case of sweaty palms can make it impossible to change mic patterns.

The playback speaker is a very nice addition. We no longer have to carry headphones just to confirm that we got something. Playback is controlled by the same jog-and-press wheel that navigates the menu. These things always feel a little uncertain to me, but it gets the job done. The headphone out is clean and clear, I’m thinking this unit will work very well as a powered mic to feed into a video recorder like the Q3HD.

Recording Samples

I was satisfied with most aspects of the H2 recording quality, except for the low level noise. My big hope for the H2n is an improvement in that area. I set up a comparison by putting the H2n, the H2, and a Rode NT4 stereo mic next to each other.

Rode NT4 between two Zooms

The Rode was connected to my Echo Audiofire Pre8 interface. I played a 1 khz test tone into all three recording chains, adjusted levels to avoid clipping, and recorded the tone. With the recorders still running I played a bit of slack key guitar, and left a nice long “tail” at the end of the recording complete with tummy gurgles. This ending section where the last note dies off is a classic place to hear self-noise generated by mics and preamps, along with the room noise (and the belly noise).

After recording these clips I pulled them into REAPER, put the Sonalksis FreeG stereo meter on each track, selected the reference tone in a loop, and adjusted the level of each track so they were within 1 dB or so. This is barely adequate level matching, but hopefully it will be revealing of the differences in noise level. I trimmed off the test tone when I rendered the sample files – no one should be subjected to a 1 khz tone if they don’t have to be. I also made a second set of clips with just the tails, and here I raised the gain significantly.

Zoom H2

Zoom H2n

Rode NT4

Zoom H2 Tail

Zoom H2n Tail

Rode NT4 Tail

Conclusions

Knowing what I do now, I’m glad I got the H2n. The improved battery life will make my recording projects easier, and the more readable screen will help as well. But aside from those issues, I’d say the H2 holds its own very well in this comparison. For many projects the difference in audio quality is probably not enough to justify a switch. For someone on a tight budget the H2 might still be a good purchase, especially if their eyesight is good.

*** Update ***

Down in the comments, Boston Dave asks about how the H2n deals with loud sources. I banged away pretty vigorously on my Martin and from looking at the wave form and listening to the result I think turning down the mic gain wheel successfully eliminated clipping. You can download the test clip, it’s straight from the recorder so it’s a little ungainly, but perhaps it will be useful to someone.

H2n High Volume Test

I also made a big step in my video camera arsenal with a shiny new Panasonic Lumix GH2. This little beauty is packed with a high performance sensor, lots of onboard image processing, a full range of manual controls, interchangeable lenses, and enough options and settings to keep this novice busy for a long long time.

I’m a long way from figuring out how to get the best from this wonderful camera, but I took advantage of one of the lovely “convertible weather in February” days we get here in Northern California to shoot a bit of outdoors playing. The wonderful old sentimental ballad, Silver Threads Among the Gold has become part of the slack key repertoire thanks to Leonard Kwan and Ledward Kaapana, and this song about the inevitable process of aging seemed to fit the austere scene.

By the way, I have a pretty fair collection of videos featuring Hawaiian slack key, mostly by me but with a couple of guest artists as well. You can see them at my YouTube channel.

The audio for this clip was captured using the Zoom Q3HD, it was placed about 24″ from the guitar, you can see the black blob of the windscreen in the lower right corner of the main performance shot. I also used the video from the Q3HD for the closeup of the picking hand.

I edited the clip in Edius Neo 2.5 and used a new reverb plugin from Jason Breebart’s Toneboosters line. The crows came with the house.

How About That H2

Then I remembered the excellent quality of the headphone/Line Out on my Zoom H2. While the quality is not quite at the level of the NT4 through a fine preamp, the H2 does a nice job of capturing clean, accurate audio. In the past I’ve used the H2 as a powered mic feeding the Kodak Zi8 and the Sanyo Xacti HD2000 mic inputs. This was always problematic, because the sensitivity of the mic inputs is a poor match for the output of the H2. It took a lot of experimenting to get the right level, then the camera preamp would wreck the audio anyway. Since the Q3HD audio input is called Line In, it should be a much better match for the Line Out of the H2. Another huge plus – the Q has metering!! This is a feature that is usually reserved for much pricier camcorders, and it definitely adds to the usability of the Q.

Time for a Test

With the house all to myself for the morning I set up in our bedroom to enjoy the lovely morning light, and shot video clips with the H2 as a Line In source as well as a few using the camera mic at various distances. With the construction project down the block and the heater going on an off, there’s plenty of ambient noise to stress test the various recording tactics. I shot a “making of” video using a Panasonic Lumix ZS3. I did a terrible job of setting the camera for the conditions, don’t blame the Panny.

I also didn’t bring a tape measure to the shoot (I learn a little every time, but at my age I forget a bit as well) or frame the close shots very well. I’ve thought about reshooting to get accurate measurements, but then I realized that each of us will be working with different conditions and different goals, so the exact distance will depend on the situation.

Interesingly, only the last shot with the Q3HD camera mic had audio quality similar to the H2 miked shot, and by that time the camera was at about the same distance as the H2 had been.

Field Recorder as Powered Mic

Naturally this technique of using a field recorder as a powered mic will work with any recorder that provides a monitoring signal in its headphone output. The problem might arise that the headphone output is low in quality, this was certainly true of the Fostex FR2-LE, for instance. Great recordings, but terrible monitoring sound. But if you have a recorder with a good clean headphone output, you have a tool to improve the audio in your Q3HD video clips.

I’m calling this experiment a success. I’m happy with the video I made using the H2 as a powered mic into the Line In of the Q3HD. I even have a wind sock for the H2, so I’m all set for shooting in the tropical tradewinds.

Hold the Phone

I learned a few things in the process of getting some comparison clips. First, I figured out how to use some of the mic stand parts I’ve collected as an iPhone “tripod.”

iPhone Tripod Improvised from Mic Stand Parts

The soft rubber mic clips don’t really fit any of my mics, but they’re handy for holding onto odd objects.

Then I learned that the iPhone viewfinder is not very video friendly. The right edge of the actual frame is hidden under the toolbar, so I was stuck guessing and experimenting to find the right position for my shot. And the size of the framing is off, the actual image is cropped noticeably larger than the view on the LCD, that is, if the viewfinder shows the image within some boundaries, the actual image will spill over those boundaries, and the object of interest will be smaller than expected. Once again, it was a matter of experimenting, guessing, griping, and doing it again to find the right distance to get the framing I wanted. (I’m hoping some iPhone guru will read this and call me names while explaining what I’m doing wrong!)

Here are the two clips on YouTube.

You can also download clips as delivered by the cameras: iPhone 4 Video Zoom Q3HD Video

Built-in Editing

Both cams have built-in video editing. The Q provides only bare bones functions, trim or divide. Trim lops off the beginning up to the selected point. Divide splits one clip into two at the selected point. But this is enough to pull one good performance out of a bunch of retakes, and clean up the beginning and end. It’s really all you need. The interface is a little tweaky, but I figured it out without reading the manual. The iPhone has a lot more power in the form of iMovie, an inexpensive app. It offers titling, more complex editing, inserting additional media, audio substitution. And the interface feels slicker. But I had to go online to read the FAQ to figure out how to use the thing, I didn’t need themes or titles or additional media or audio substitution, and the program appeared to transcode the video in the process of creating the output. The processing time on the Q was much shorter, making me think it left the original video compressed when trimming and splitting.

I tried out the possibility of editing iPhone video on the Q, and vice versa, but no go. I also was unable to copy a file back to the iPhone, or sync it to a location where I could pull it into iMovie. (iPhone guru, here’s another opportunity to berate and educate me. Thank you!) I was able to move files back and forth on the Q3HD by simply copying them to and from the SDHC card.

Perform for the Edit

One last thing I learned about editing on the camera – a simple “look at me play guitar” video doesn’t have much going on to mark edit points. So even though we don’t need a clap for audio syncing, it’s helpful to make a big obvious motion, like a large clapping motion, to mark the start of retakes. It’s also helpful to leave some generous and profound pauses before and after the playing so the edit point has enough leeway. These tricks will make it a lot easier to deal with the small screen and small controls when editing inside the camera or phone.

Another thing missing on both these cams and many others below the professional ($2000 and way up) level is the lack of metering and monitoring. There’s not a way to tell if the audio is being recorded well until playing back the clip, when it’s too late to make any corrections. Even when I’ve done multiple test shots I’ve always considered myself very fortunate if I manage to capture some useful audio with this kind of gear.

The Q3HD Arrives

A couple of years ago, Zoom introduced the Q3, a pocket video recorder that emphasized the audio quality. It included stereo directional mics in an X-Y configuration and didn’t inflict excess processing on the audio. Unfortunately, they released this SD format camera just when HD video took off. YouTube switched to HD format, Flip put out the MinoHD, HD video recording began to appear in phones, HD was everywhere except in the Q3. But earlier this year Zoom announced the new Q3HD, which addressed the format issue, offered improved low light performance, added special settings for difficult lighting conditions like concerts, and added a Line Input for stereo audio. In the past, new products from Zoom have arrived long after their planned date, so I was expecting to see the Q3HD sometime in 2011, but happily the first shipments have arrived in the US and are available from a number of retailers. I bought one from BSW and it arrived the day after Thanksgiving.

My initial impressions are really positive. The build quality seems a bit better than my venerable H2, and it’s noticeably more solid feeling than the Kodak Zi8. The menu system is easy to manage, there’s audio metering and monitoring during recording, it even comes with a 2 GB memory card and a set of AA batteries.

Three Way Comparison

I mentioned the other cams that I purchased because they had audio input and some degree of manual control. It seemed reasonable to use them in a comparison with the Q3HD. So I setup in Digital Duck studio (also known as the spare room upstairs) and shot some video, first using camera mics then external mics.

I chose 720p for the video format for all three cams. The Zi8 and Sanyo don’t offer control over the audio format, but on the Zoom I selected CD quality PCM (44.1 khz and 16 bit word length).

For the external mic shots I connected an Audio Technica AT822 to the Zi8, a Rode NT4 to the Xacti HD2000, and a pair of Shure KSM141s through an M-Audio DMP3 to the Q3HD. Here’s the video that resulted:

When I listen to the clips on my “junk reference” computer speakers, the difference in audio quality isn’t that great, but as soon as I put on headphones or turn on the good monitors, the audio from the older cams sounds dreadful in comparison to the Q3HD. My Zi8 sounds worse than I remember, so perhaps it’s dying, but even the HD2000 features burbling noises in the quiet moments and an odd tonal balance. I also feel that the video quality of the Q3HD was noticeably better than that of the Zi8. Looks like the Kodak is going in the drawer.

My First YouTube Clip from the Q3HD

The Q3HD has minimal built-in editing, just “Divide” and “Trim” – minimal but sufficient to create a clip for YouTube, so I figured I should put up something straight from the camera. I chose the Rode NT4 stereo mic just to simplify the setup, and fed the mic into the M-Audio DMP3 preamp. From there an adapter chain converted two 1/4″ outputs to a single stereo cable ending in a 1/8″ stereo plug, which went into the Q3HD Line In jack. I took advantage of the meters on the Q3HD to check my levels, aiming for average levels around -20 dBFS and peaks around -6 to -8 dBFS.

With that set I chose the highest resolution video, 1080p format. I chose PCM (uncompressed WAV) audio, but stayed with the basic 44.1 Khz sample rate and 16 bit word length. After a few test shots to get the framing right I recorded a few takes of an old R. Alex Anderson song, Haole Hula. With a little scrolling around in the playback, I was able to trim the clip down to the performance I chose.

Based on my experience with other camera software, I didn’t load the Handyshare package that comes with the Q3HD. I simply removed the memory card, stuck it in my card reader, and copied it to my hard disk. From there I uploaded to my YouTube account. Here’s the result:

Since I was determined to use only in-camera editing, my clip has no title, no fades, no credits, but I feel that it presents the song in fine fashion anyway.

Framing Changes with Format

One thing I stumbled on while shooting my clip – changing the video format also changes the framing of the shot. I framed the image then decided to switch from 720p to 1080p. I made the format change and shot a clip, and when I played it back my head was gone! Here are a couple of snapshots that illustrate the difference:

Framing at 1080p

Framing at 720p

As you can see, the change is pretty dramatic. So be sure you check your framing whenever you change the video format, or you might lose your head.

Not Quite Perfect, But Pretty Darned Good

On the frown side, I’m a bit annoyed that I have to buy the AC adapter separately. My brief attempts to shoot in lower light were not a big success. And while I was really pleased when I learned that Zoom added a Line In jack on this new camera, I’m already wishing it had a 1/8″ stereo mic input as well. With that extra feature the NT4 and the Q3HD would make a fantastic package for portable recording. As it is, I’m shopping for a battery powered two channel preamp with P48 phantom power that won’t bust the budget … and I’m not having a lot of luck.

On the smile side, I expect to have a lot of fun with this little camcorder. The video quality is reasonable in good light and the audio sets a new standard for a consumer cam. It’s nicely made, easy to use, an all around fun toy.

By separating the mic from the camera, I should be able to position the mic for optimum sound while placing the camera for the visual effect I want. Of course, I can do this wihout an audio input on the camera by a technique called parallel recording, that is, recording on a separate audio system of some kind. The familiar clack of the slate at the start of a movie sequence is used to make it easy to synchronize the picture and sound, and this technique works very well for my homebrewed videos as well. Still it’s very tempting to think that recording directly to the camera is an easier way out, with camera audio every take and every edit lining up without any extra effort.

I’ve been interested in the range of options for attaching a mic to the Zi8, and back in December I went on a little mic shopping binge. Between my storage drawer, Ebay, and Sound Professionals I gathered a collection of mics in a range of prices. But I was struck with a glitch in my Zi8 audio, which required several round trips to attempt repair at the East Coast contract repair depot. Eventually Kodak agreed to replace my camera, but by then I was on a lovely trip to Hawai`i.

Test Design

Now that I’m back I’m ready to offer up some test clips. At first I planned to video a number of brief samples of guitar and vocal, which was very troubling to me. I strongly believe that audio sampling should be done with a single performance and carefully volume matched, in order to reduce the number of variables in the sample. As much as we think otherwise, humans just cannot judge subtle (or even not-so-subtle) differences without careful controls. My aha moment came when I realized that I was only testing audio, not video, so I could use a recorded source to get a repeatable performance. Focusing on audio only also allowed me to upload the much smaller audio clips, so the comparison will be quicker and easier.

For level matching I decided to take the easy way out and simply normalize the files. Normalizing raises the peak of a file to a given level, in this case I chose -3 dBFS. I adjusted levels like this so our ears won’t be fooled by level differences, but these samples hide the differences in the real recording you’ll get if you use one of these mics. So I’m including the original sample as well. Remember that I adjusted the sensitivity of the Zi8 for each mic, so the volume levels are affected by that even in the original, un-normalized samples.

I first created a test recording in Reaper, some slack key guitar naturally. I recorded in mono with an Audio Technica AT4050 in cardioid pattern. Then I added a bit of narration. All camera mics I know about, and many accessory mics as well, are omnidirectional. There are plenty of reasons why an omni is a good choice, but real trickery is required to get a good stereo image with omnis. So I threw in a bit of movement in the stereo field to evaluate channel separation. I arranged the narration and the stereo test ahead of the music and adjusted levels.

I placed all the mics very close to my normal listening position and played back the test recording through my normal monitoring chaing – Echo Audiofire 8, Hafler P3000, Dynaudio BM6p. A Radio Shack SPL meter showed 74 db C weighted at the mic position.

As I mentioned, I adjusted the sensitivity of the Zi8 for each mic. In each case I adjusted the sensitivity to the highest level that did not show any red. I label the default sensitivity as 0, lower sensitivity goes from -1 to -5 and higher goes from +1 to +5. I wound up using the whole range in this comparison.

Test Clips

Here’s the reference recording. It won’t get any cleaner than this.
ref.mp3
or download ref.mp3

I used the Zoom H2 as the mic in my first experiments with the Zi8, so I included it in this comparison. It’s also handy because we can record with the H2 and the Zi8 at the same time. Even though the signal in the Zoom was very low and pumped up with a lot of digital gain in the normalization process, it is quite a bit cleaner than the Zi8. I set the Zoom to M Mic Gain because tests have shown that the H setting adds noise. This still resulted in a rather low level, so raising it also raised the noise as well.
h2p.mp3
or download h2p.mp3

Original versions, no normalization:
oh2p.mp3
or download oh2p.mp3

I used the rear mics on the H2 so I could operate the controls on the front of the unit. As a result the stereo left and right are backwards in both the parallel clip and the Zi8 clip. Here’s the output of the H2 headphone jack recorded on the Zi8 with sensitivity set to -3.
h2v.mp3
or download h2v.mp3

Original versions, no normalization:
oh2v.mp3
or download oh2v.mp3

If you’re like me you’ve been fooling with recorders for a while, maybe going back to cassette tapes. Perhaps, like me, you have some kind of little mic in a drawer somewhere. My drawer mic is labeled www.reactivesounds.com but the web site is a dead end now. I bought this to use with my minidisc recorder a few years ago. The mic is omni, no cable (requires a female to male extension), and has been repaired with superglue. I used -2 sensitivity for this mic.
drawer.mp3
or download drawer.mp3

Original versions, no normalization:
odrawer.mp3
or download odrawer.mp3

I’ve used Sound Professionals http://www.soundprofessionals.com/ for these kinds of recording gear for years. I used one of their T-mics for years with my minidisc, but somehow lost it. They still sell a mic with the same model number, SPSM-1, but it doesn’t look much like the mic I remember. I set the Zi8 to -3 sensitivity for this mic.
spsm-1.mp3
or download spsm-1.mp3

Original versions, no normalization:
ospsm-1.mp3
or download ospsm-1.mp3

The SPSM-15 is the least expensive single point stereo mic sold by Sound Professionals. It appears to have a higher low frequency cutoff than the SPSM-1, and/or lower sensitivity. As a result I set the Zi8 sensitivity to -2.
spsm-15.mp3
or download spsm-15.mp3

Original versions, no normalization:
ospsm-15.mp3
or download ospsm-15.mp3

The AudioTechnica AT825 has been a popular single point stereo mic for many years, but was recently discontinued. The replacements are much higher in price, so it might be worth watching for used examples of the AT825 on Ebay or Craigslist. It seemed perfectly matched to the Zi8 and worked well at the default sensitivity setting.
at825.mp3
or download at825.mp3

Original versions, no normalization:
oat825.mp3
or download oat825.mp3

I was impressed with the performance of the AT825. I was very disappointed in the AudioTechnica Pro 24. Although it looks much more impressive than the T-mics from Sound Professionals, it was very low in output, requiring that I set the Zi8 to the maximum +5 sensitivity.
atpro24.mp3
or download atpro24.mp3

Original versions, no normalization:
oatpro24.mp3
or download oatpro24.mp3

Let’s Look at the Video

Let’s finish off with some actual video. Be careful with comparisons, but perhaps there will be some blatant differences we can take away. When I framed the shot to include the whole guitar the camera wound up about 5 feet from the instrument. I adjusted the Zi8 sensitivity for each mic using my normal procedure – the highest setting that did not show any red squares.

I had a little fun with my new Edius Neo 2.5 software putting together a compilation of the mic demonstrations.

All these mics sound better here than in the audio test with the recording, but they still show their basic characteristics. The camera mic picks up a lot more room, as it must at that distance. And since the room is a boxy little thing, the recording sounds small and boxy.

The H2 in this clip is very slightly overdriving the Zi8, to my ears. The slightly dark voice of the H2 comes through as well. The Sound Professionals SPSM-15 does a pretty decent job for very small bucks. I failed to mention in the video that the sensitivity on the Zi8 is down to -3. This means the SPSM-15 is quite sensitive, so it might be a problem if your source is loud. To my ear the AT825 is the winner. I like the clear presentation. I’m sorry I didn’t do a better job of balancing the channels.

I hope these comparisons are useful. I plan to try these mics with a different camera in a future post.

* * * Correction on 12/03/2010 * * *

The mic I keep calling an AT825 is actually and AT822, the unbalanced version. Sorry for the brain fog.

Alan Blumlein

In 1931 Alan Blumlein applied for a patent on what we now call stereo sound. He described techniques for creating the auditory illusion of placement and depth using two (or more) channels of recorded and reproduced sound. As part of this patent application he described an array of two bidirectional mics in a coincident X/Y arrangement that we today call a Blumlein array:

Two bidirectional or figure 8 mics in a coincident XY

In the same document he described the Mid-Side mic arrangement. Rather than a crossed pair of mics at 45 degrees to the source, the Mid-Side array has the Mid mic pointing directly at the source and the Side mic at right angles to the source. The Mid mic can be any pattern but the Side mic must be a bidirectional or figure-8 mic.

Two bidirectional or figure 8 mics in Mid-Side

Mid-Side Recording

This article from emusician.com discusses the technical details of Mid-Side recording in some depth. Note that the use of different patterns for the Mid mic gives different results after decoding.

When I record in Mid-Side using my home recording chain it’s startling to see the difference in the levels of the Mid and Side channels. With both channels set to the same gain the Side channel barely shows any signal.

Decoding the Mid and Side channels to Left and Right is easy in a multitrack recording program. Simply place the Mid channel on one track panned to the center. Place the Side channel on a track panned hard left. Then place a copy of the Side channel inverted in polarity on a track panned hard right. When you mix the three tracks down you’ll have two stereo tracks.

Here’s a video I made demonstrating Mid-Side and Blumlein arrays with some demonstrations of the stereo field.

There are a few ? ? ? problems with the video, please accept my apologies. The bubble wrap stereo demo is funny (to me anyway), but the clipping caused by the amazingly loud pops wrecked the stereo field. Listen to the incidental noises for a better idea of how these recording techniques work. And the distortion is not there in the my recording, it was introduced by the YouTube compression process.

Mid-Side and the H4n

I also missed several opportunities to actually address some details of the H4n. For instance, the level metering shows levels after the signal is decoded. I think there’s a good chance of clipping the Mid mic and not seeing it in the decoded signal.

When setting up the Mid-Side connections on the H4n, notice that there’s a menu selection to identify which channel is the Mid and which is the Side.

Let me wrap up by mentioning that I sent my H4n back to the seller. I think it’s a pretty interesting recorder, but for my regular uses the H2 does at least as good a job. When I want to do more serious recording I just turn on my home studio system. I’m looking forward to continued progress in these handheld recorders, though. I just can’t resist the idea of a world class recording chain in my pocket.