Review of the Sony PCM-M10 recorder (for linguists)

August 2010

Introduction and first impressions

The Sony PCM-M10 (Figure 1) is the smallest addition to Sony's family of portable audio recorders. The palm-sized PCM-M10 recorder adopted many of its features and style from the highly acclaimed PCM-D50 model, including a rugged construction and an attractive design. Sony states in its marketing campaign that "It's the ideal choice for making live musical, nature sound and field recordings." Sony has done a really good job with the entire series in terms of design, performance, price, and marketing (see this interesting video tutorial). The PCM-M10 recorder is among the most popular small recorders available today. I receive a lot of emails with questions about it, hence my decision to write a review.

Figure 1. The Sony PCM-M10 field recorder

The Sony PCM-M10 recorder is one of the many popular portable digital recorders available today. Every major manufacturer seems to make one of these: Tascam, Marantz, Yamaha, Korg, Samson, and others. The design is based on the idea that one should be able to obtain high-quality stereo digital recordings of ambient sounds, including live music, oral history, sounds of nature, school plays, sermons, etc. The recorders are self-contained devices equipped with a pair of good microphones, a number of digital signal processing (DSP) options, automatic and manual recording levels, and a few different recording file formats and levels of compression.

The Sony PCM-M10 recorder makes an excellent first impression. It simply looks gorgeous! I have seen so many badly designed palm-size electronic gadgets lately, so it is so refreshing to hold the PCM-M10. Everything about the design seems right. It feels solid, though only the front plate is made of (very thin) metal. The burgundy color looks fantastic. The device certainly feels like a prosumer device; it looks and feels better than the $200 price tag (street price) might indicate.

Why use small recorders?

For most amateur users of field recorders, the small size is an advantage. However, the demands of professional field use usually require a more rugged, larger design, especially one that can accommodate two XLR inputs and superior microphone pre-amplifiers. The price for a reduction in size is rather dramatic: small recorders are difficult to interface with professional-grade microphones, which are required for speech research. Also, despite clear advances in miniaturization, it is still rather difficult (and costly) to make and implement quality analog and digital components, especially microphone pre-amplifiers, headphone amplifiers, and phantom power supplies. The Sony PCM-M10 somehow manages to work around the form-factor limitations and delivers a strong alternative to the larger and more expensive units, without cutting too many corners.

Internal microphones

The Sony PCM-M10 offers a pair of really decent built-in microphones (Figure 2). There are several good reviews available in pro audio magazines and on the Internet. Wingfield Audio ranks the built-in microphones to sound "as good as the D50" and to have "some of the cleanest sound you can get for the price." I tested the microphones with ambient speech and guitar music and certainly agree that the overall subjective quality of the recordings is excellent. However, because speech and hearing professionals rarely use built-in microphones, I am going to limit the present discussion to the performance of the recorder's external microphone interface.

Figure 2. The Sony PCM-M10 recorder comes equipped with a pair of really decent microphones

The plug-in power interface

The Sony PCM-M10 offers an external, stereo microphone input and a stereo line input (Figure 3). It is an important distinction, and I think it requires a little bit of clarification. The microphone is designed specifically for stereo, electrect condenser microphones, wired for so-called "plug-in power." Plug-in power is a popular 3.5 mm (1/8-inch) interface found on small audio recorders and camcorders. It is based on the simple idea that the recorder, through the interface, supplies the microphone with small DC voltage required for proper operation. Sony has had a long history of plug-in power devices, dating back to the venerable DAT recorders, such as the TCD-D100. Sony also makes a line of plug-in power stereo microphones, such as the ECM-DS70P. The beauty of the design is that, in most cases, it simply works. One does not need to worry about impedance, sensitivity, or phantom power. Simply connect a compatible microphone to the recorder and the combination works perfectly, most of the time. The added advantage of the PMC-M10 is that you can turn the plug-in power off for use with self-powered microphones, such as the ECM-MS957 and the Sony ECM957PRO. Finally, the plug-in power interface uses an unbalanced connection, which may be more susceptible to interference, especially with longer cables.

Figure 3. The stereo microphone and line inputs

However, as you look through the inventory of available plug-in power microphones, you soon realize that you may not be able to find one that is suitable for recording speech for research purposes. While they are mostly very decent general-purpose stereo microphones, they simply do not have the electrical or acoustic properties required for speech and hearing research. However, it is possible to interface a professional-grade microphone with plug-in power recorders. The key is to use a battery-powered microphone along with the appropriate XLR-to-3.5mm adapter cable. The 3.5mm mini-plug should be a stereo TRS plug, and it can be wired either for the left channel only or for so-called "dual mono," which distributes the signal equally in both channels (my preferred method). The wiring is very important, so you have to make sure to ask for this particular kind of cable when ordering the PCM-M10 recorder. Most major vendors carry the cables and adapters you need.

In theory, you can also use dynamic microphones with a plug-in power input. However, I would not recommend doing so because of the likely differences in impedance and the lack of appropriately high and clean gain. You can somehow alleviate the problem by using an in-line impedance matching transformer, such as the Shure A96F. I have done it myself in the past, but I was never happy with the resulting recording quality (see the self-noise section below).

Of course, the best option is to use a dedicated, stand-alone, two-channel microphone pre-amplifier, such as the Sound Devices MixPre (reviewed here). You will get fantastic quality because the MixPre will do all the heavy lifting for you, but the use of an external mixer seems to defeat the purpose of using a small recorder, doesn't it? For me, personally, this would still be a really good option. I encourage to consider it, especially if you already own a small, plug-in power recorder.

Design and specifications

The full specifications sheet can be found here. I will limit this review only to the features that I consider to be of most interest to linguists. As I mentioned earlier, the Sony PCM-M10 is designed incredibly well. All the controls, buttons, sliders, rockers, and dials are of just the right size and are located just where you would expect them to be, especially if you've used Sony portable DAT recorders before. The front plate is made of thin metal, but the rest of the recorder external cover is made of plastic. The plastic does not feel terribly flimsy or cheap, but the device probably would not survive a hard fall or a dip in the lake. The recorder seems to be built at least as well as the Zoom H4N (reviewed here), but I like the Sony PCM-M10 better. It simply feels right. It is a very subjective feeling, and you may have completely different impressions. It would be best to stop by an audio store and hold the device first before buying it. If you are not able to do that, you should take my word for it: the overall design of the recorder is first-rate, at least for a device in this price range.

All the main functions are available through dedicated buttons (Play, Stop, etc.), rockers (headphone volume), switches (pre-amp sensitivity), or dials (recording levels). All other functions are available through a menu-driven interface visible on the adequately bright and high-resolution LCD.

The recording level dial is located on the right side (Figure 4). It is an oversized dial with a very solid feel. Sony must be praised for its attention to detail. The dial is likely to be one of the most commonly used controls on the recorder, so it is very reassuring to know that it is designed well and is very easy to use. Also, on the same side, you will find the Power/Hold switch and the 3.5mm input for the remote control (Figure 5).

Figure 4. The right side of the recorder showing the Power/Hold toggle, the remote control input, and the recording levels dial

Figure 5. The included remote control unit

On the left side (Figure 6), you will find the headphone/line output (selectable via the menu), the mini-USB connector, a compartment for a micro SD card, and the DC input (for use with the supplied adapter).

Figure 6. The left side of the device showing the headphone/line output, the mini-USB connector, a compartment for a micro SD card, and the DC input

On the bottom (Figures 7 and 8), you will find the microphone sensitivity switch, the speed control switch, and the headphone volume rocker. The switches have a positive and solid feel. The last thing you want is for some of the settings to be accidentally changed between or during your recording sessions.

Figure 7. A close-up of the microphone sensitivity switch and the DPC speed controller

Figure 8. A close-up of the volume rocker

Finally, you will find a battery chamber (Figure 9), with a nicely designed lid. The compartment houses two AA batteries. Battery life has been ranked extremely high by Wingfield Audio in their review. My tests confirm many hours of recording available, even with constant headphone monitoring. This might be the most extraordinary feature of this recorder.

Figure 9. The battery chamber

The menu system is simple and easy to use. The recorder does not have too many functions or DSP special effects. It does, however, offer a core of very useful functions, such as the option to supply power with the microphone input, a pre-record buffer, and the very useful cross-memory recording feature, which allows you to record continuously from the built-in (4 GB) and to the external memory (via a micro SD card), and vice versa, without recording interruptions. There are also the typical digital filters, such as the low-cut filter, limiter, and pitch control, but they are of less use and interest to speech scientists. The menu also lets you select the audio file format and settings. The recorder's highest quality setting is PCM (uncompressed) WAVE format at 24-bit/96,000 Hz. I typically recommend the 24-bit and 48,000 Hz setting for most speech research, so the recorder is, at least in theory, capable of delivering perfectly adequate frequency response and dynamic range. You have a choice of the WAVE or MP3 file formats. I would imagine that most researchers would record WAVE files, especially with the low price and high capacity of micro SD cards available today.

There is one additional feature that I find particularly useful: the track marker. At any point during the recording, you can add a soft marker to your audio file by pressing the T-Mark button either on the recorder or the remote. The included Sony Sound Forge software recognizes the markers, which makes navigation and editing much easier. This is one of my favorite features of the Sound Forge software in general, so I find the fact that the file marker feature is available on the recorder very useful, indeed.

I like to think that I am fairly flexible and forgiving when it comes to equipment design, firmly believing that recording technique is more important than the details of design. However, one feature that I prefer not to do without is real-time analog signal level monitoring. Sound Devices recorders and mixers have fabulous LED monitors, and I am really partial to them. The Sony PCM-M10, like many other small recorders, uses a dBFS-based real-time levels display on the LCD. It is adequate, though somewhat difficult to see in bright light. Fortunately, there are dedicated LEDs for -12 dBFS (a commonly used peak value) and signal overload, so at least you can fall back on these if the LCD display is unreadable.

Finally, the recorder comes with Sony Sound Forge Audio Studio LE software for MS Windows. Sound Forge is an excellent audio editor, with an impressive array of digital functions and filters. It is particularly good as a front-end recording software to a PC-based recording rig. I have been using Sound Forge for years, and it has remained one of my favorite audio editors. Sound Forge is compatible with the markers made during your recording session to facilitate easy editing, especially of long sound files. It also offers a very capable noise reduction plug-in (requires a separate license) and an MP3 converter.

Audio tests

I put the Sony PCM-M10 recorder through all my usual tests. The recorder performs really well, but only if you are willing to work around its limitations. I decided to use the Audix HT5 omnidirectional headset microphone for most of my tests, primarily because it has a battery power supply, which guarantees the correct voltage being supplied to the microphone. Like most professional microphones, the Audix HT5 is not compatible with plug-in power, so you need to turn the plug-in power option off in the PCM-M10's menu for optimal results.

Self-noise

Overall, I was impressed with the noise performance of the Sony PCM-M10. However, I must emphasize the fact that the recorder works best with self-powered condenser microphones of medium-to-high sensitivity. You have very little room for error. You need to match the recorder with the right microphone, and use your recording technique (esp. close placement) to your advantage.

The Audix HT5 is a medium-high sensitivity microphone, so it does not put too great demands on the microphone pre-amplifiers. In fact, to obtain the typical conversational levels for a linguistic interview (peak of -12 dBFS), I only needed to turn the pre-amplifier gain to level 3.5, just over 30% of its range. This ensured that pre-amplifier noise was kept at a relatively low level. Noise does increase significantly with high gain settings. You can read more about noise and my noise testing methodology here and here.

If you look at the FFT of self-noise in Figure 10, you will see that overall noise levels are just a little higher than those obtained with the Audix HT5 and the Fostex FR-2LE and the USBPre recorders. The noise spectrum looks very normal, with a peak around 60 Hz, and a randomly distributed noise above. This type of noise is not particularly detrimental to acoustic analysis of speech, at least not at these low levels. Again, you must watch your technique to maximize signal-to-noise ratio. In theory, based on Equivalent Input Noise of the PCM-M10 and the Equivalent Noise Level of the microphone, the Sony recorder should not appreciably degrade overall noise performance of the recording chain, at least at moderate recording levels. In practice, the theory bears out. The Sony PCM-M10 is capable of producing high gain, low noise recordings.

Figure 10. FFT of the Sony PCM-M10's self-noise with the Audix HT5 microphone

I tried using the PCM-M10 recorder with a dynamic microphone. You will need an in-line impedance matching transformer, such as the Shure A96F to get the best results, without a dedicated, stand-alone microphone pre-amplifier. I used my favorite Sennheiser HMD25 dynamic microphone and connected it to the recorder via the Shure A96F adapter. I had to raise pre-amplifier gain to 6.5 (65% of the range) and was immediately able to hear an appreciable increase in noise in my monitoring headphones. However, the noise level was surprisingly low for a device in this price bracket. Figure 11 shows an FFT of self-noise obtained with the Sennheiser HMD25 microphone. As you can see, overall levels are a bit higher than in the case of the Audix HT5. You can download the audio files at the bottom of this page.

Figure 11. FFT of self-noise obtained with the Sennheiser HMD25 microphone

Low-frequency response

A neutral low frequency response is crucial to a successful speech recording. Many important acoustic characteristics of speech can be found in frequencies below 600 Hz. It is also an area where a bulk of my own research lives, which is why I am particularly interested in testing low frequency response of professional audio recording equipment.

I use the same test across all my reviews for easier comparison. I generated a waveform with peaks of equal amplitude at the frequencies of 50, 100, 200, 300, 400, and 500 Hz. I then played the signal out of a flat-response loudspeaker and recorded it with the Audix HT5 microphone and about 1.5 inches from the sound source (a typical headset distance). The spectrum in Figure 12 shows the low frequency response of the recorded audio file. The microphone reproduces each center frequency really well, with no appreciable attenuation or amplification above 200 Hz. There is, however, a slight dip around 100 Hz, and a more significant dip around 50 Hz. Clearly, there is some attenuation below 100 Hz. It might be a conscious engineering decision (e.g., to help reduce low frequency noise), or it might be due to the shortcomings of the hardware. It is hard to say, but it is important to recognize the fact that unless you are interested in small detail around or below 100 Hz, the recorder should give you adequate low frequency response, provided a flat-response microphone is used. Overall, I would rank the PCM-M10's low frequency response as adequate for most analysis, but not good enough for some of my own work.

Figure 12. A spectrum of the Sony PCM-M10's low frequency response showing attenuation below 100 Hz

Spectral detail

Once you match the recorder with the microphone, and provided the noise floor is appropriately low, you should be able to get good spectral detail out of your recordings. The A/D converter can introduce some noise (mainly quantization noise) and distortion, but these days the PCM digitizing technology is so good that that one can have enough confidence in the sampling aspect of the recorder, even at this price point. Audiophiles will still, of course, be able to hear differences, but for most types of linguistic analysis, noise and artifacts due to the A/D converter itself are not terribly significant. They may play a role in LPC analysis/re-synthesis, or low-level spectral analyses, but if you are primarily interested in formant analysis, the Sony PCM-M10 should give you ample detail to work with.

The only area where I thought the recorder was lacking was in high frequencies, above 10,000 Hz or so. It is probably due to the characteristics of the frequency response itself, and may be a deliberate design decision for the sake of subjective sound quality. For speech analysis, we want the entire spectrum to be pancake-flat, but for most people, flat recordings sound, well, flat and lifeless, so audio engineers intentionally shape the frequency response of most consumer and prosumer recording devices to improve perceived audio quality. This might also be the case here, though I was not able to confirm it with Sony USA product managers directly. Indirectly, yes, they say the recorder is designed to "make great recordings," which is vague, though perfectly understandable.

The spectrograms in Figures 13 and 14 show good spectral detail with some loss of definition in the higher frequencies. Otherwise, the frequency envelope appears to be fairly natural. I would trust these recordings to deliver decent, though definitely not perfect, data.

Figure 13. A spectrogram of the Polish phrase "czarna krowa" obtained with the Audix HT5 microphone and the Sony PCM-M10 recorder

Figure 14. A spectrogram of the English phrase "buy a large barrel of good beer" obtained with the Audix HT5 microphone and the Sony PCM-M10 recorder

Most sociophonetic analysis involves the LPC analysis of formant frequencies, bandwidths and amplitudes. The PCM-M10 delivers a respectable LPC spectrum with sharply defined peaks of F1, F2, and F3, as seen in Figure 15.

Figure 15. An LPC spectrum of the vowel /ae/ obtained with the Audix HT5 microphone and the Sony PCM-M10 recorder

LPC analysis/re-synthesis

LPC analysis/re-synthesis is a particularly demanding test of spectral detail and low noise. It happens to be one of my favorite tests, partly because I do a lot of work involving speech synthesis. My tests confirmed excellent detail up to F2, but a loss of definition above. With a fully voiced token (/aed/), the F3 behaves well, with some drop-outs into the consonant /d/ (Figure 16). However, with a more complex string ("bordo"), there are significant frame drop-outs throughout the F3, resulting with audible artifacts (Figure 17). The black lines represent formant tracks prior to synthesis; the red represent F1 values decreased by 50 Hz and F2 values increased by 200 Hz, as a result of the synthesis.

Listen to MP3 at 128 kbps (the first token original; the second re-synthesized):

Figure 16. LPC analysis/re-synthesis of the string /aed/

Figure 17. LPC analysis/re-synthesis of the string /bordo/ showing a loss of detail along F3

Conclusions

The Sony PCM-M10 is a really cool device. I use the term "cool" deliberately. It is about the size of a Blackberry smart phone, it has a great user interface, a really decent acoustic performance, and fantastic battery life. There's a lot to love about this recorder. Who is it for? It would make a fantastic oral history tool, but getting two external microphone tracks into it is not particularly easy. It would make an excellent interview microphone for impromptu field recordings. It would make a very capable live theater and music recorder.

So how about linguistics, speech, and hearing sciences? I think that, with the right microphone, you can use the PCM-M10 for a lot of kinds of field recordings. I probably would not use it for the most critical research projects, but I would buy a bunch of those if I were to teach a methods class or run a research laboratory for undergraduate students. Bear in mind, however, that you have very little room for error. You need the right microphone, and nearly perfect technique for the best results. In a sense, the PCM-M10 is a perfect modern equivalent of the venerable Sony TCD-D100 (PCM-M1) DAT recorder, no more, no less.

Download audio files

	Description	Quality	Comments
	With the Audix HT5 microphone; test recording in Polish	48,000 Hz; 24-bit; mono	Captured in a sound booth
	With the Audix HT5 microphone; test recording in Polish	48,000 Hz; 24-bit; mono	Captured in a sound booth
	With the Audix HT5 microphone; test recording in American English	48,000 Hz; 24-bit; mono	Captured in a sound booth