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DPA 4066 Omnidirectional Headband Microphone Review (for linguists)
The DPA 4066 microphone is a relatively new addition to the headset lineup and is additionally available in a low sensitivity variant (4067). The DPA 4066 has impressive specifications, including a broad and flat frequency response, an omnidirectional polar pattern, medium sensitivity, close placement, and resistance to excessive moisture and temperature. The DPA 4066 has the potential to be the phonetician's perfect microphone, at least in terms of its electrical and acoustic properties. Let's take a closer look at the microphone and see if it lives up to our expectations. Interface options, price, and availabilityBefore I go into the details of design and performance, I would like to emphasize a truly unique feature of the DPA 4066 (and most other DPA MicroDot microphones): it is available for just about any wired or wireless professional microphone system. DPA have made an effort to be truly platform-agnostic and thus appeal to a rather broad audience. DPA uses a proprietary MicroDot interface, but offers adapters for most major wired and wireless systems. If you are already using, say, the Shure wireless system, you will simply need to buy a MicroDot to TA4F Switchcraft adapter and you will be able to seamlessly incorporate the DPA 4066 into your existing system. This modularity gives the DPA series of microphones a distinctive advantage over the competition. In addition to most wireless standards, the DPA 4066 can be easily incorporated into wired applications, including those preferred by field recordists. Let us now look at two such use cases. Systems with plug-in powerA lot of field linguists prefer to use small, solid-state digital recorders with a plug-in power microphone interface, such as Zoom H1 or Sony PCM-D50. Plug-in power has been a popular microphone interface on DAT, MiniDisc, and solid-state recorders for some time. It involves a 3.5mm stereo input that provides a small voltage to a compatible electret condenser microphone. Despite the ubiquity of the plug-in power interface, there are relatively few professional-grade microphones compatible with it. Those are typically stereo microphones (shotguns, handhelds, and lavaliers) for ambient sound recording (e.g., video production). However, none of the microphones recommended for speech recording on this website (and elsewhere) are compatible with the plug-in power interface. This is precisely the reason why I have never recommended plug-in power recorders to linguists. I have always preferred to use a recorder with a standard XLR interface and 48 V phantom power because of its compatibility with a wide range of professional microphones. The DPA 4066 changes the status quo. When used with the optional two-channel MPS6030 Miniature Power Supply (a belt-pack using a 9 V battery), the DPA 4066 (and many other DPA microphones) can be properly interfaced with a DAT, MiniDisc, or solid-state recorder with a 3.5mm stereo input. Because you can connect two DPA 4006 microphones via the MPS6030 unit, you get the most compact, professional interview setup available today. DPA solves the plug-in power problem simply and elegantly. But there's more. Suppose you use the Sony PCM-D50 field recorder because it gives you excellent battery life and a really decent 24-bit/96,000 A/D converter. However, the microphone's pre-amplifier on the Sony recorder is the Achilles' heel of this and most other small field recorders. If you are not happy with your recorder's pre-amplifiers, all you need is the DPA MMA6000 Miniature Microphone Amplifier, which will enable you to obtain lab-quality field recordings with your existing flash recorder. This is likely to make a lot of field linguists and oral historians extremely happy. Systems with XLR inputsThe DPA 4066 microphone can also be easily interfaced with professional-grade microphone pre-amplifiers and recorders equipped with the industry-standard XLR input. All you need is the optional MPS6001 Miniature Power Supply, which provides (1) an MicroDot-to-XLR adapter, (2) a phantom power adapter, and (3) a battery-powered power supply - all in one sleek and durable unit. This enables the DPA 4066 microphone to be connected to field recorders with or without phantom power on board. Moreover, the ability to power the microphone with a single AAA battery will save a lot of your recorder's own battery power because you will be able to switch your recorder's phantom power supply off. Alternatively, you can use the DAD6001 MicroDot to 3-pin XLR (Figure 2), which doesn't provide battery power, but which does allow you to connect the microphone to any pre-amplifier or recorder with 48 V phantom power.
Figure 2. DAD6001 MicroDot to 3-pin XLR, which allows you to connect the microphone to any pre-amplifier or recorder with phantom power Price and availabilityThe DPA 4066 microphone is one of the most expensive miniature headset microphones available today. It retails for about $650 (USD), and the optional MPS6001 power supply will set you back another $300. With sales tax and shipping, you are likely to spend about $1,000 for one microphone kit, and twice as much if you want to record interviews. That is a very steep price, indeed. However, given the unique features you get with the DPA system, the steep price should be justifiable. After all, this is the only microphone system available today that has the necessary features to guarantee perfect results in the field, no matter what recording system you use. If the acoustic performance proves to be as outstanding as the engineering aspects of the DPA system, many of us will be trying to raise funds to buy it. Design, construction, and specificationsThe DPA 4066 omnidirectional microphone is a miniature microphone with a flexible metal boom, attached to a flexible behind-the-ears headband. This is a rather familiar design, similar to the competitor microphones, such as the Sennheiser HSP2. The boom can be detached from the headband and used with another headset. The entire unit has been designed for unbotrusive stage use, with special attention paid to reducing handling noise and increasing resistance to moisture (a double vent protection). The boom is not as sturdy as that of the Shure Beta 53 or Beyerdynamic Opus 55 MkII, but it is more flexible, thus allowing more precise, customized placement. The headset comes in black, brown, and beige colors.
Figure 3. DPA 4066 omnidirectional headset microphone, with close-up images of the MicroDot connector and the microphone capsule The DPA 4066 is a medium sensitivity microphone (6 mV/Pa) and with an excellent ability to handle high pressure levels (up to 144 dB SPL). These two characteristics should be conducive to capturing signals with rich spectral detail and ample headroom. Table 1 summarizes the specifications of the DPA 4066 microphone, according to the manufacturer.
Table 1. Technical specifications of the DPA 4066 microphone As expected, the DPA 4066 has a broad and flat frequency response. Figure 4 shows the frequency response graph, according to the manufacturer. DPA offers two "boost grids" which change the response above 5,000 Hz, for extra "presence."
Figure 4. Frequency response graph of the DPA 4066 omnidirectional microphone with the "soft boost grid" option Low frequency performanceLinguists, speech scientists, hearing scientists, and others in related areas are interested in clean, unaltered, high-fidelity recordings. Most vocal microphones have rather poor (i.e., non-neutral) performance below 500 Hz. The omnidirectional microphones recommended on this website,however, have very good low-frequency performance, and the DPA 4066 is no exception. A great deal of my own research focuses on voice quality and nasalization, whose spectral correlates occupy the lower frequency ranges of speech. I wanted to take a closer look at the low-frequency performance of the DPA 4066. 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 DPA 4066 microphone. The spectrum in Figure 5 shows the low frequency response of the DPA 4066 microphone. It reproduces each center frequency really well, with no appreciable attenuation or amplification throughout the range. There is a slight bump in the spectrum around the very low end (50 Hz), but I it is negligible, and possibly a result of the inevitable low-frequency rumble in the immediate recording environment. I am confident that speech signals captured with the DPA 4066 microphone will give me reliable low-frequency data. This neutrality of the low-end is extremely important, and I am very happy to report that the DPA 4066 passes the low-end the test.
Figure 5. Low frequency response of the DPA 4066 microphone NoiseI tested the DPA 4066 microphone's self-noise to see how it compares to the competition. My setup is the same for all my tests. I use a sound-treated booth, I record with the Sound Devices USBPre, into a laptop computer running on battery power. The microphone is at the distance of about 4 feet from the laptop computer, which is the only appreciable source of noise. The laptop uses SSD storage and its fan is disabled. Some level of noise from the environment (especially low-frequency rumble) is unavoidable. Clearly, the DPA has very low self-noise, which will likely be negligible for most types of speech analysis and synthesis. The medium sensitivity of the DPA 4066 requires moderate pre-amplifier gain, which is likely to be of benefit, particularly when recording with portable field recorders whose pre-amplifiers tend to be noisy at higher gain settings. Overall, I am really impressed with the DPA 4066 microphone's noise performance. Figure 6 shows the spectrum of the microphone's self-noise.
Figure 6. DPA 4066 self-noise spectrum Speech recordingsI tested the microphone thoroughly with different setup variations. One of the things I was interested in was whether the microphone was resistant to handling noise. The microphone boom rests on one's cheek most of the time, so there is a possibility that some of the rubbing noise might leak into the recording. I found that while the DPA 4066 is not completely immune to handling noise, it does handle it well (pun intended). I still do not consider such neckbands to be the right choice for fieldwork, but because the boom can be easily detached, I recommend that you try to use the microphone with any of the DIY headband designs that I you can find throughout this website. Speech recording performance was explemplary, on par with the Beyerdynamic Opus 55 MkII and Sennheiser HSP2. The spectral envelope was very natural and the spectral detail rich and accurate (Figure 7). I am very comfortable recommending this microphone for speech research.
Figure 7. Spectrogram of the Polish phrase "czarna krowa" showing very good spectral detail As expected, both FFT (Figure 8) and LPC (Figure 9) graphs show very well-defined formant peaks, with no evidence of distortion, smearing, or unwanted noise.
Figure 8. FFT of the vowel /a/ in "krowa"
Figure 9. LPC of the vowel /o/ in "krowa" showing very well-defined spectral peaks and a natural envelope ConclusionsThe DPA 4066 omnidirectional headset microphone is one of the best microphones that I have ever tested. It has very low self-noise, medium sensitivity, flat frequency response, resistance to excessive moisture, temperature, and handling noise. What sets this microphone apart from the competition is the modular design of the entire DPA system. No matter what wired or wireless system you are using, you will be able to incorporate the DPA 4066 into your workflow with ease. The only downside is the price, but at least in this case you do get what you pay for. Download original files
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