In this article, we would like to figure out which headphones to buy to work with the metal detector: wireless headphones, wired, what characteristics, what should I look for when choosing?
There are many myths and opinions about earphones for metal detectors. But not all of them are true in our case (or applicable for search with a mine detector).
In particular, there is an opinion that it is best to buy headphones with high impedance (more than 100 ohms). In the case of a metal detector - this is not so.
But let us find out the essence of the matter.
Important headphone features:
Resistance (for example 32 ohms)
• Frequency range (eg 20 to 20,000 Hz)
• Headphone sensitivity (rarely published in ordinary headphones, as numbers may not be very prominent)
• Frequency response - amplitude-frequency characteristics (rarely sold in ordinary headphones)
• Operating time (for wireless headphones) (for example 19 hours)
• Delay (for wireless headphones) (for example, 0.04s)
Of the whole range of available features for working with a metal detector, the following are important to you:
For wired headphones
• Frequency range
• Headphone sensitivity
• Frequency response
For wireless headphones
• Frequency range
• Work time
• Headphone sensitivity
• Frequency response
Looking ahead, it is safe to say that almost all headphones sold on the market are suitable for the metal detector. On average, sufficient features to search with these devices will look like this:
• Impedance - 32 Ohms (this is not important for wireless headphones)
• Frequency range - from 20 to 20,000 Hz
• Operating time - 12 hours (for wireless headphones)
• Delay - from 0.04 to 0.06 s (for wireless headphones)
Why is this so?
In order to find out this, you need to understand each parameter.
Headphone Frequency Range
The phrase that the headphone frequency range is from 20 to 20,000 Hz means that the headphone can reproduce sound with frequencies in this range. Anything smaller or larger will be reduced to the nearest row boundary.
But there are 2 facts:
1. An average person perceives a frequency sound range in the range from 25 to 18000 Hz (maximum from 16 to 20,000 Hz).
2. The metal detector produces a sound range in the range from 1000 to 2000 Hz)
3. Hence there is a conclusion: any headphones that block the capabilities of the metal detector and the human ear are suitable for us.
(In general, the wider the frequency range, the better the headphones. But in the case of a metal detector, everything is much more modest).
4. Headphone impedance
5. When they say that the headphones have a resistance of 32 ohms, this means that this is the average value of the resistance of these headphones for different frequencies. It is also called impedance.
However, from the school physics course we know the formula: I = U / R.
The voltage in the device is constant. Therefore, the greater the resistance, the lower the volume (= less current).
And since the metal detector supplies low voltage to the headphones, it makes no sense to use high-impedance (more than 100 ohms).
(That is, on 100-ohm headphones the volume will decrease, but this will not affect the quality).
For reference, the voltage supplied by the metal detector to the headphones is equal somewhere - 1.5-2V.
Moreover, resistance is important only for wired headphones (because they have a wire), and for wireless this is useless information (because the signal is sent through a different medium).
Hence the conclusion: for working with a metal detector, any low-impedance headphones sold on the market are enough.
Why are there any low-impedance headphones and high-impedance ones?
Earlier, before the era of players, metal detectors, etc. (i.e. devices with low power) was mainly stationary equipment, requiring 220V power, and having good power. High-impedance headphones were produced for such equipment.
After the advent of low power devices, there was a need for headphones for these devices (i.e. corresponding to this low power). So low-impedance headphones began to appear.
At the same time, the sound quality of the headphones does not provide resistance, but the frequency range, sensitivity and frequency response.
Therefore, headphones for low-power devices may well have a good sound.
Why are headphones with a resistance of more than 100 ohms still popular?
High resistance protects the headphones from overload when connecting them to studio equipment (amplifier).
Accordingly, low-impedance can`t be connected to such equipment.
But high-resistance can be connected to a weakly powerful (player, metal detector). They will work well.
But not necessarily better than low-impedance (depending on frequency range, sensitivity and frequency response). Although the sound will be quieter on high-impedance headphones.
· Headphone sensitivity
· Sensitivity is an important characteristics. For headphones that are used with metal detectors, this value is usually not written (because the simplest headphones are suitable for these devices).
Moreover, the manufacturers of the metal detectors do not lead to any requirements for headphones in their documentation to the devices:
· • no resistance
• no output current (on the connector)
• neither sensitivity
• no frequency range
In general, the documentation does not have any requirements for headphones.
Sensitivity is measured in dB.
This value reports the maximum undistorted volume level when a unit of power is supplied.
For the average user, this means how quiet sounds will be heard in the headphones without distortion (these sounds).
Good value is 90dB.
Due to the fact that the metal detector uses low power when transmitting a signal, any headphones are suitable for it.
Headphone frequency response
The amplitude-frequency characteristics of the headphones (AFC) are presented in the form of a graph - the dependence of the volume on the signal frequency.
Such a characteristics as a frequency range is a consequence of the frequency response graph.
The graph shows how the headphones behave at different frequencies. Where they have peaks and where there are failures.
Such graphics lead to very high-quality and expensive headphones.
For a search with a metal detector this is not required, respectively, and no one indicates such data.
Opening hours and delay
These parameters are already clear when using wireless headphones.
Headphones are different ... Some have a working time of 8 hours. Others - 12 hours.
It is necessary to take those that work longer.
The minimum delay is extremely important when working with a metal detector. Modern technologies allow us to provide an acceptable value for this delay - 0.04-0.06 s.
If more, then it is no longer acceptable.
In particular, the old Bluetooth technology had a high delay.
There is also such a thing as protection against external noise.
If high protection (noise isolation) is a blessing in the studio, then for search engines with a metal detector this is not so.
Because you need to hear what is happening nearby (in terms of security).
And besides, in the heat your ears will sweat in the headphones with a high degree of protection.
But there is a downside ... The earplugs will not be able to remove the noise of the wind. Therefore, they are undesirable when searching with a metal detector.
Design features of headphones for a metal detector
Wired headphones for the metal detector (in terms of design) should have a thick, spring-loaded cable and it is desirable to adjust the sound on each speaker.
For wireless headphones, there are no specific design requirements yet.