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.

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.

or download h2p.mp3
Original versions, no normalization:

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.

or download h2v.mp3
Original versions, no normalization:

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 an female to male extension), and has been repaired with superglue. I used -2 sensitivity for this mic.

or download drawer.mp3
Original versions, no normalization:

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.

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

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.

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

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.

or download at825.mp3
Original versions, no normalization:

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.

or download atpro24.mp3
Original versions, no normalization:

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.

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.

I got a long and interesting email from Mark McPherson of Portland, describing his evaluation of the H4n:

Hi Fran,

Mark McPherson here, up in sunny Portland, proud owner of a shiny new Zoom H4N.

I’ve been enjoying your slack-key recordings and gear commentary for some time, and thought I might pass along a few preliminary observations regarding the H4N.

To begin, let me say that I have a modest technical bent. I’m a retired engineering guy, with now-ancient education in engineering physics and math, and an increasingly-ancient career in the semiconductor and electronics industries. Now I dabble in music, and have an ongoing interest in amateur recording, tempered by the fact that I don’t play well enough to make anything worth recording.

I’ve been using an H2 for the past 18 months or so, and have had excellent results with it — there can’t be a better value in small digital recorders. I’ve had particularly rewarding experiences when using it in four-channel mode, mounted on a photographic tripod in the middle of an ensemble jam. I had an H4 for a short period, but returned it after finding lots of wide-spectrum noise in the preamps, the infamous beep problem, and various whistles and descending and ascending tones in recordings made with external mics with phantom power applied. And I hated the user interface passionately.

I think Samson/Zoom fixed some of this with the H2. Much better user interface, decent mics, simultaneous four-channel recordings, simple yet useful software to pan, mix and normalize the four-channel recordings in the recorder — wonderful stuff for the price.

So I was mighty hopeful when I saw word of the impending release of the H4n, thinking that the light had been seen at Zoom, and the H4′s defects perhaps laid to rest.

I’ve had my new H4n for a week now, and have found a few things that might be of interest.

Overall, I’m hugely impressed with improvements in the mechanical design, build quality, and can live with the user interface, which is better, but far, far from intuitive. I’d appreciate better display resolution, but it’s bigger, brighter, and it works well enough. I really like the use of more durable metal 1/8″ jacks for frequently-used I/O ports.

I’m anxious to learn where the single gain control for the preamps is placed in the input circuitry. I haven’t yet tried to determine this. The onboard microphones seem adequate, if perhaps a trifle bright for my taste.

Last night I decided to check on the phantom power situation, having read a post or two on the Nature Recordist’ site about problems. My only mics requiring phantom power are a pair of MXL 604s, Chinese small-condenser devices. Nothing particularly special about them, and certainly not low-noise.

After attaching them to the recorder I turned on 48V phantom power and made a 2-channel recording. I heard a fair amount of hiss, and the old familiar ascending and descending “whistle” tones at low levels, too, and was quite discouraged. Adding or removing the AC power adaptor made little difference. No “beep”, though.

Then I decided to set up the recorder with a 16 GB Transcend HDSC card, put it in four-track mode, and let it run overnight on AC power to see how the recorder handled the transitions at the 2 GB file size limit, and also what happened when the card filled up. I left a pair of half-discharged NiMH batteries in the recorder, set the record gain to “50″ for all mics, and let it run over night.

I’m happy to report that the recorder with 16 GB Transcend HDSC card installed ran smoothly all night long, making several sets of files smoothly and apparently seamlessly, and that the final file terminated properly when the card filled up. The recorder seems to handle that 16 GB card without problems. I think I’ll order another one.

Another interesting thing was that, after about ten minutes of recording, much of the unwanted whistling and noise I associated with the phantom-powered external mics disappeared and did not return. These mics are not used frequently, so there may be some interaction between the Zoom’s phantom power supply and some temporary mic behavior which disappeared with use. Anyway, the message here might be that if you encounter noise, particularly ‘whistles’ of ascending or descending frequency on the H4n’s external inputs with phantom power applied, it may make sense to let a recording run for an hour or two and then re-examine the noise profile.

It also appears that the NiMH batteries in the Zoom received a charge while the AC power adapter was in use overnight — they were pretty flat when the recording started, but by the next morning were apparently fully charged again. Not sure I saw anything about this in the manual, but I may have missed it. Nice if true.

So I’ve gone from thinking the H4n to be no better than the H4 at recording to thinking that it may just fill the bill for a decent four-channel-capable machine, without high expectations for low-sound-pressure recordings because of the preamp noise, which appears to be a little better, but not exactly transformed. I’ll repeat some of this stuff to validate it, but right now I’m pretty happy, and thinking this is a good value and can be a useful tool. I considered purchasing the Sony PCM-D50, but really wanted the four-channel recording option and like having the ability to plug in a couple of mics requiring phantom power.

Hope this is of some interest, and would be happy to share any other data or try some simple tests with the gear I have here if it’s useful to the cause…

Cheers,
Mark McPherson

In further discussions with Mark we’re questioning whether the odd noises he heard were in fact coming from his microphones rather than the recorder. We’re both talking about ways to do more rigorous testing.

In the meantime I’ve been exploring the Mid-Side recording feature of the H4n, and I hope to have a post about that soon.

Zoom Field Recorders

I’ve had a Zoom H2 field recorder since they were delivered and it has been a very satisfactory tool. I’ve used it to capture audio for my YouTube videos, to record hula accompaniment for my wife, to archive band rehearsals, and to save ideas for original compositions. A very satisfactory tool, but not quite CD quality, not quite the tool I would use for high quality recording. The self-noise just peeks into the quiet spots and long fades, the mics roll off a bit above 16 Khz.

I have posted some comparison tests between the H2 and other recording chains here on Home Brewed Music: a comparison with my best studio recording chain and a shootout with several other field recorders. In both cases the H2 was “amazing for the price” but not the winner.

The H4 preceded the H2, cost a bit more, does multi-track recording and has XLR inputs and 48V phantom power for serious microphones. There have been many complaints about the user interface and the fragile feel of the controls. I’ve never used one myself, so I can’t say anything about the recording quality.

Both these units offer a remarkable level of functionality, with multitracking on the H4 and surround sound on the H2, and both function as a USB interface for recording directly on the computer.

What’s new with the H4n?

This year Samson/Zoom announced a new recorder, the H4n. This unit has a larger LCD screen, improved user interface, and according to the manufacturer, improved mic preamps. I ordered one as soon as they were available and it arrived today.

The H4n is only slightly larger than the H2, but it is just that bit too big to be comfortable in a shirt or pants pocket. And the mics sticking out without protection also make it unlikely as a pocket device.

The bright orange LCD screen on the H4n is a big improvement over the H2 and H4. The look and feel is also more impressive, with a style and solidity that are missing from the earlier units.

The gain setting on the H4n is a big change from the H4 and H2. Both those recorders have a 3 position level switch, which sets the preamp level before the a/d converters. Then another control sets the recording level from 1-100, but this setting is applied after the a/d converter and mic preamp. This means that only the 3 position switch can actually lower the recording level in a way that prevents overload and distortion, and the second finer control is essentially useless.

The H4n has only the incremental gain control from 1-100. Hopefully it is implemented so that it turns down preamp gain and controls overload. I’m counting on the smart guys at the Zoom H2/H4/H4n forum to poke around and figure out the details.

I was expecting features like auto-level, limiting, and auto-record, but Samson/Zoom surprised me by including a Mid/Side decoding function in the preamp as well.

Recording with the H4n

Well, how about some clips? The big bright screen on the H4n makes level setting easier than the H2, and with my recording mode all set to stereo 44.1/24, recording is just as easy as the H2 – one press of Record starts standby mode for level checks, then one more press and we’re storing bits.

After a quick recording a feature I never thought much about – a monitor speaker – turns out to be very comforting. Just hit play and there’s confirmation that you captured something. Its time to move the tracks to the computer, and this would be good time to compliment Samson/Zoom on their manual. This little recorder has a ton of features and the manual has covered every one I’ve needed so far. Page 35 clearly explains how to connect the H4n to the computer over the USB connection and it worked like a charm on my XP SP3 system.

Another improvement is obvious and very welcome – this new unit is a USB 2.0 High Speed device. The previous H4 and H2 are both USB 2 compatible, but they are anything but high speed. This H4n makes my standalone cardreader obsolete. Switching cards in and out draws attention to a potential problem, though. The door over the SD card slot does not look rugged enough for the use it will get. I kind of expect to see a lot of these with masking tape or gaffers tape covering the SD slot when they get older.

Hey, as long as it’s hooked to the computer, let’s see how it works as an audio interface. Maybe I’m just having a good night, but everything goes smoothly, Adobe Audition 1.5 sees the Zoom H4n and records a decent track.

Here’s a little “Opihi Moemoe” using the H4n as an audio interface, using the built-in mics. The positioning is about 30″ between the guitar and mics:

or download opihi.mp3

Sounds pretty good to me, but in the fade at the end you can hear a bit of noise. Hmmmm.

A four way comparison

The main comparison is between the two Zooms, the Fostex FR2-LE, and my main studio recording chain, a John Hardy M-1 preamp feeding a LynxTwo-C A/D converter. A pair of Shure KSM141 mics provide audio to the Fostex and John Hardy. I tried to group all four units as close as possible.

Two mics and two Zoom recorders

Each of the clips is mono, I kept only the Zoom track from the mic that was pointed toward the guitar. The streaming clips are MP3, but the download is a PCM WAV file and considerably larger. I positioned the guitar 3 feet from the mics. This is a quite a strenuous test of the recording chain, because the guitar is such a quiet instrument that plenty of gain is required even for much lesser distances.

The Fostex:

or download 1-1-fr2.wav

The H2:

or download 1-2-h2.wav

The H4n:

or download 1-3-h4n.wav

The Hardy:

or download 1-4-jh.wav

I’m a bit disappointed with the results here. I was hoping the H4n’s new preamp and mics would provide a big improvement in noise performance compared to the H2, but I’m not hearing it. Listening to the long fade at the end of the clip, both the Zoom units exhibit more noise than the other two systems. Of course this is an extreme test, and with a more normal recording distance the noise wouldn’t be a problem. And the source of the noise might be the mics rather than the preamps, so it’s only fair to compare the H4n with one of the Shure KSM141 mics.

Using external mics

The Fostex with Shure mic:

or download 2-1-FR2.wav

The H4n with Shure mic:

or download 2-2-h4n.wav

In these clips the guitar is a little closer to the mics, about 30 inches. This is still far enough to require a lot of gain, and both units exhibit some noise. But again the H4n is a touch noisier than the Fostex in the fade at the end of the clip. With the external mic, though, the difference is a lot smaller.

In the four way comparison, the studio chain with the Hardy preamp and Lynx converters was clearly the quietest. How does the H4n do in a head to head with the champ?

The H4n with Shure mic:

or download 3-1-h4n.wav

The Hardy with Shure mic:

or download 3-2-jh.wav

This recording has the guitar even closer, less than 2 feet and just far enough to avoid proximity effect. With lower gain and the external mic the H4n sounds a lot less noisy but still just a hair more than the Hardy and Lynx.

And so the story is told

I’m really quite impressed with the H4n. It has a solid feel and a look that inspires confidence. The controls work cleanly and seem sturdy. The large bright display makes the unit much more friendly to old fogey eyes like mine. The manual is substantial because the feature set is pretty amazing. I’ll probably only scratch the surface, but plenty of other musicians will find use for the multi-track recorder with overdubbing, effects, metronome and so on. Folks doing interviews and recording lectures can benefit from the limiter, automatic gain control, and auto-record.

How is the H4n as a solo acoustic guitar recording tool? I’d say about 95%. The tonal balance of the recordings are fine, the dynamics are good. I’m quite happy with how the guitar sounds with either the external mic or the built-ins. I’m a little bit disappointed by the noise performance, though. A bit closer placement, a little noise reduction software in post, it’s a problem that can be solved, but I was hoping for world class performance from this little unit and I’m afraid it’s not quite at that level.