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.

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.

The problem has been that there are not a lot of omni mics around. The market doesn’t seem that interested in omnis, so the manufacturers are not interested. In the five years or so that I’ve been recording and buying gear, I would guess that models of directional mics in the marketplace outnumbered omnis by 20 to 1 or more, and almost all the hip new inexpensive mics have been directional.

In the last year or so, though, Jon O’Neil and his Naiant Studio Store has begun selling a very inexpensive omni microphone which Jon builds himself. He use readily available capsules, adds his own active electronics, and mounts the whole thing in an XLR connector shell. The result is compact, rugged, and inexpensive. I think they work pretty well, too. Here’s a brief comparison of a pair of Naiant MSH-1 omnis to a pair of DPA 4061s:

Naiant MSH-1
DPA 4061

The DPAs carry a list price of $429, and they require an adapter to connect to standard mic preamps that adds about $75 to the cost. Even used they cost about 10 times as much as the Naiant MSH-1 costs new. It’s certainly true that the DPA can be used in more applications, because it’s very small and unobtrusive, and the two different mics are not equivalent, but just on the basis of sound quality, I think they’re amazingly close.

This year Naiant began selling the MSH-2, a mic based on a larger capsule. Jon describes this mic as having lower noise and a gently falling high end compared to the MSH-1. I’m a sucker for an inexpensive omni, so I ordered up a pair. Here’s a recording using one of these new mics alongside an industry standard for microphone quality. I’m using a John Hardy M-1 preamp and Lynx2 converters. This time I set up the Naiant MSH-2 on one channel and a Schoeps CMC6/MK2 on the other. I mounted the mics so they were a few inches apart and about 6 inches from the Martin OM-18GE. Here are the two mono files that resulted:

Naiant MSH-2
Schoeps CMC6/MK2

I can hear some slight differences, although they’re pretty subtle. By turning up the volume and listening to the extended “tail” or decaying signal, I can hear a higher noise level in the Naiant track. But considering that the Schoeps costs about $1400 and the Naiant costs $35, I’d call the similarity pretty amazing. Certainly if someone asked me for an inexpensive microphone to record solo acoustic guitar, I’d be quite comfortable recommending the Naiant MSH-2.

How do I record my guitar so I can judge my progress (or lay down a rhythm track or even make a CD just for family and friends). I have a pickup in the guitar, I don’t need great quality, and I don’t want to spend a lot.

Since this person is posting on an internet forum, I will assume they have a computer. If it’s a PC type, it almost certainly has some kind of built-in soundcard, with at least a mic input. So all we need to do is hook the guitar pickup to that mic input and use some sort of program to capture that input and save it to a file. It just so happens that there are some very effective recording programs available to download for free, so that leaves as our only problem some way to connect the guitar pickup to the mic input. And here it is:

This is a 1/4″ phone female to 1/8″ mini male adapter. A normal guitar cable like the one just above the adapter in this picture (male 1/4″ phone plugs at both ends) fits into the hollow side. The pointed side plugs into the mic input of the computer. It costs about $4.00 at any store or web site that sells electronic geegaws (like Radio Shack). This is all you need to connect your pickup to your computer (assuming you have a guitar cable).

Now, on the software side what are the options? Unfortunately, the built-in Windows Sound Recorder is not very useful. It’s limited to about 1 minute of continuous recording without intervention. There are not effects or editing features, no click track or metronome, no metering, and certainly no multitrack overdubbing and mixing.

The easiest free program I’ve found is Audacity – it’s a little clunky but it is full featured. It includes plenty of editing capability and built-in effects, and you can save your recordings to various formats like .wav for burning to CD and (with some free extra software) to .mp3 for your portable music player or web site. I’ve used this little adapter and Audacity to record new song ideas on our laptop when we’re traveling. I’ve also used it to create practice loops when I’m trying to nail a tough section of a new song. Compared to a decent microphone, preamp, and audio interface these recordings are fuzzy, noisy, and crude, but they do the job, and the price is definitely right.

Here’s one verse of an old Hawaiian song, “No Ke Ano Ahiahi,” recorded as a solo guitar instrumental using the the 1/8″ mini plug adapter and Audacity.

And here’s the same track with some reverb added.

Obviously these are not “major label quality” recordings by a long shot. The direct output from a pickup is not very close to the natural acoustic sound of your guitar. But we’ve looked at a tool that can help get your pickup based recordings much closer to a natural acoustic sound in a previous blog entry: “Better EQ Through Software”. And, as we stated at the beginning of this entry, the whole purpose of using this simple, cheap adapter is to get simple, cheap recordings, not Grammy awards.