Introduction
If you are going to record sounds with microphones, you cannot use a speaker in the vicinity of the microphones to listen to the sound during recording. There is then a chance that the sound will roar, a kind of short circuit between the speaker and the microphone. So you need headphones. But how further?
Criteria to be met by headphones for fieldwork
- No spiral cable because this cable is heavy on the spiral (a lot of cable over short distance) and continuously pulls on your headphones or even pulls them off your head. If the headset has such a cable, replace it with a cable without a coil.
- Foldable, you often have to walk a lot without being busy with the recorder. The headphones must then be taken away from your head and stored somewhere, that can be a bag or your jacket pocket. Small size is then handy.
- Comfortable ear cups for you. These can lie on the ear or over the ear, the latter can give after long listening a sweaty environment in the shell.
- A suitable plug for your recorder (often stereo 3.5mm jack). A gold-plated plug can be prevered, but I would not make a disaster if it is a different metal.
- A frequency range of at least 40 - 20,000 Hz.
- A sensitivity that is suitable for the headphone output of your recorder
- If no specific impedance is specified for the headphone output on the recorder, then you can assume that this is not that important.
- A maximum power handling capacity of approximately 100 to 500 mW (5 to 10 times nominal rated power), depending on the sensitivity.
ATTENTION!, this is not a standard listening level but a level to protect the headphones.
The in-ear systems are not suitable for fieldwork. One of the reasons for this is that the in-ear systems do not close sufficiently. The earcup has a dampening effect on the sounds from outside.
You cannot avoid dealing with technical data. You need to know how much power the recorder provides and whether that is sufficient to provide your headphones with sufficient sound. And what is sufficient sound? Furthermore, those headphones are very personal because not everyone's head is equal. So you have to go to the store and go fit, I would advise against ordering one via the internet.
Table
The table below contains a limited overview of headphones that are all foldable. Some models offer a choice between a spiral cord or a straight cable. Audio-Technica supplies both cables with the headphones below and with the ATH-M50x model even a short straight cable, especially for field work. All headphones have a standard 3.5 mm jack.
Headphones that meet the above requirements, but that does not mean that the headphones in question are suitable for your head and/or recorder. The data comes from the specifications of the manufacturers. All models mentioned are of the closed ear cup type. The first three headphones are no longer available (n.l.a.) and are included for reference. It is striking that the impedance of the models that are now available has gone up and the sensitivity has gone down. This will undoubtedly have to do with the trend of increasing hearing damage. That this is probably true can be seen from the table column dB/SPL in which the maximum achievable sound pressure is specified, almost all models do not go beyond ±130 dB/SPL, a value that you should never pursue for monitoring, see below under "What is sufficient sound?". I assume that the specification of the sensitivity of the Sony MDR-7506 model is a wrong statement, because it is not common to specify this with headphones in this way, you can see this kind of specifications with speakers.
| Diameter | load capacity | Frequency | ||||||||
| Make | Model | driver unit | Impedance | Sensitivity | Nominal | Maximum | dB/SPL | range | Weight | Available |
| Sony | DR-6M | 50 mm | 28 Ohm bij 1kHz | 110 dB SPL/mW | 10 mW | 100 mW | 130 | 20 - 20,000 Hz | ± 350 gr. (incl.cable) | n.l.a. |
| Sony | MDR-V4 | 30 mm | 45 Ohm bij 1kHz | 103 dB SPL/mW | 100 mW | 500 mW | 130 | 10 - 25,000 Hz | ± 165 gr (excl.cable) | n.l.a. |
| Audio-Technica | ATH-M50x | 45 mm | 38 Ohm | 99 dB | unknown | 1,600 mW bij 1kHz | 131 | 15 - 28,000 Hz | ± 285 gr (excl.cable) | yes |
| Audio-Technica | ATH-M40x | 40 mm | 35 Ohm | 98 dB | unknown | 1,600 mW bij 1kHz | 130 | 15 - 24,000 Hz | ± 240 gr (excl.cable) | yes |
| Devine | PRO 2000 | 40 mm | 32 Ohm | 95 dB (±3 dB) | unknown | 400 mW | 121 | 15 - 22,000 Hz | unknown | yes |
| Devine | PRO 900 | 45 mm | 40 Ohm | 96 dB (±3 dB) | unknown | 1,800 mW | 129 | 10 - 26,000 Hz | unknown | yes |
| Shure | SRH940 | 40 mm | 42 Ohm bij 1kHz | 100 dB/mW bij 1kHz | unknown | 1,000 mW | 130 | 5 - 30,000 Hz | ± 322 gr (excl.cable) | yes |
| Sony | MDR-7506 | 40 mm | 63 Ohm | 106 dB/W/m(?) | unknown | 1,000 mW | 136 | 10 - 20,000 Hz | ± 220 gr (excl.cable) | yes |
| Tascam | TH-02 | 50 mm | 32 Ohm | 98 dB (±3 dB) | unknown | 600 mW | 126 | 18 - 22,000 Hz | 298 gr (incl.cable) | yes |
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| Sony MDR-V4 Headphones (1986) | |||||||||||||||||||||
What is sufficient sound?
Before we go to the store for headphones, it is so useful to know what it is all about. According to the new standard you can be exposed for 8 hours to a sound level of 85dBA. The time must be halved for every 3 dB more. So you can be exposed for a maximum of 2 hours to a sound of 91dBA or 30 minutes to a sound of 97dBA. You are allowed a maximum of 7.5 minutes!!! listening to headphones with a sensitivity of 103 dB/SPL/mW connected to an amplifier that is set to deliver 1mW of power. As a result, exceeding those times means that you can either listen for a shorter time or that your hearing damage is sustained. A headphone connection with a power of 20mW is therefore more than enough power. Even headphones with a specification of 90 dB(SPL)/mW still give the maximum 103 dB/SPL. So the Devine with a sensitivity of 95 dB (assuming 1 mW) gives a maximum sound pressure of 108 dB/SPL in this example. In this example, a recorder with a headphone connection with an output power of 50mW gives a maximum sound pressure of 112 dB/SPL. The headphones themselves give it a go at a sound pressure of 121 dB/SPL.
Imagine you want to buy the Audio-Technica ATH-M50x because it is the most comfortable for your head. Your recorder has a headphone output with a maximum output of 20mW. What can you expect? The Audio-Technica ATH-M50x has a sensitivity of 99 dB. What is not stated in the specification is how it was measured. Standard this is measured at 1 mW. We therefore assume that. The calculation then becomes 10LOG20+ 99 dB = 112 dB/SPL(10LOG20 is 20mW output power of the recorder. The maximum output level is 20mW divided by the reference value of 1mW remains 20mW. The 10LOG has to do with the calculation of the power. You can add the dB value together because they are equivalent. The dB value itself says nothing, what manufacturers mean here is the sound pressure and that is noted as dB/SPL of Sound Pressure Level.) The 112 dB/SPL is therefore a value that you can only be exposed to for a minute, if it gets longer, you will suffer hearing loss.
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| Sony DR-6M Headphones (1976) | |||||||||||||||||||||
revision July 30, 2020