How to choose headphones?

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Many of us are used to choosing appliances based on their technical specifications. Does this approach to headphone selection apply?? Let’s get to the bottom of this… First of all, let’s see what the list of headphone specifications is all about. Let’s at once specify that we shall not consider such parameters as the size, weight, form-factor, principle of operation and acoustic registration now – simply because except for a principle of operation, sense of all these parameters is obvious. And the story about different principles of action would be long enough and could result in a separate article.

We will only look at the features that are directly relevant to headphone transducers. There are only four of these characteristics:

Playable Frequency Range

Resistance

Sensitivity

Maximum Input Power

Let’s look at each of these parameters in more detail.

Playable frequency range: size doesn’t matter?

In layman’s circles, this parameter is often given great importance – sometimes even from sales assistants we hear that it is the main indicator of the sound quality of headphones. We can notice the following practice of headphone producers: they usually indicate a wider frequency range for more expensive and high classed models than for more simple and budget ones.

In fact, the range of reproduced frequencies not only has no relation to sound quality, but in general, does not carry any meaningful meaning. Why? – let’s get to the bottom of it.

It is still not precisely established what range of sound frequencies a person is able to hear, but the approximate limits of this range are defined: from 20 Hz to 20 kHz. In fact, it makes no difference to a person whether the headphones are capable of playing anything outside this range, but it is important that everything that falls within this range is played with a dispersion in volume that does not exceed reasonable limits with a uniform volume level no headphone plays the entire range .

It should be said that some manufacturers intentionally increase this spread by “raising” or “lowering” certain parts of the frequency range in an effort to give the sound of their headphones a definite “brand” character – for example, the practice to “raise” certain parts of the high frequency range in expensive headphones has recently become popular – so that their sound seems more detailed, intelligible. In any case, no information about this variation in volume, rises and falls in different parts of the “frequency range” is given to us by the range of reproduced frequencies.

In addition, it is worth noting that very few modern headphones are able to play high frequencies without dips – in most models in the area above 14 kHz begins an intensive decline in volume level. So don’t get scared if the range of the headphones is claimed to be under 20 KHz it often happens with headphones based on armature drivers .

By the way, no matter how wide the frequency range indicated by the manufacturer is, the headphones can reproduce the sounds of any frequency that are outside this range, but with a very big “margin” in volume. And what “dip” should be considered large enough to mark it as the boundary of the claimed frequency range? 20 decibels, or maybe 30, or even more? In fact, there is no unified standard in this respect, and each manufacturer is free to mark the range boundaries literally wherever he wants. In such conditions it is impossible to speak not only about the usefulness of such a characteristic as a range of reproduced frequencies in headphones, but also about its correctness or truthfulness.

Resistance matters for music from tablets and smartphones

This indicator means nothing else than the value of electrical resistance of headphones. The impedance is usually recommended to pay attention to those who are going to use headphones with “low-power” sound sources – portable players, laptops, tablets, smartphones, as well as computer sound cards.

It is assumed that if the sensitivity of headphones is enough about how much sensitivity is considered “enough” we will tell further , the optimal value of their resistance for portable players, smartphones and tablets is not more than 50-70 Ohm, and for laptops and computer sound cards – not more than 100 Ohm figures, of course, approximate and average . At the same time, it is not recommended to use headphones, which impedance is lower than the output impedance of the source this applies to any, not only the above described “low-power” devices – at least, it is fraught with losses in sound quality, as a maximum – damage to the source. The latter, however, is only possible in extremely “neglected” cases.

everything seems to be simple – we look at the impedance and decide if the headphones fit to our source or not. In reality, though, things are a bit more complicated.

The headphone tubes actually have two similar characteristics to each other: DC resistance and impedance complex impedance , which reflects the headphone’s resistance to AC current. Since the sound signal from the player to the headphones is just an alternating current, of these two characteristics we are interested in the impedance.

In isodynamic headphones, impedance is linear – their resistance does not depend on the frequency of alternating current. But for dynamic and armature headphones, depending on the frequency of the current fed to them and therefore on the purity of the sound they reproduce impedance may be different.

And while some headphones dispersion is insignificant, in others it reaches a considerable value – and this can have certain sound quality implications. If in any part of the frequency range impedance of the headphones is too low below the output impedance of the source – in this area will occur loss of resolution and increase the level of distortion. Similarly, the situation is when the “low-power” source can not cope with too high impedance headphones.

A small example – many owners of popular portable headphones Koss Porta Pro, using them with players, among their drawbacks note slow, “inaudible”, although a powerful bass. Yes, these headphones do not hold any real records for fast and understandable bass, but if you were to try and hook them up to a reasonably strong amplifier you would probably notice a significant improvement in this parameter. And the thing is that although the claimed impedance of Koss Porta Pro is only 60 ohms, which is quite normal for portable headphones – in the “mid-bass” area it goes up to 140 ohms – and most portable players “pass”.

Now the question – why do most headphones impedance is denoted by only one digit, and what’s the use of this figure? Answer: this number in most cases reflects the impedance value at 1000 Hz, which is how the user defines and sets the volume level comfortable for him/herself. This number is useful: with most headphones the “spread” of impedance depending on frequency is not very large after all, so this number can serve as some kind of reference point when choosing headphones.

Complete impedance charts are rarely announced by headphone manufacturers, but if you want to know all about the impedance of a particular model you are likely to find the information on the web.

Sensitivity reflects sound pressure level

In other words, the volume that the headphones are capable of developing when a certain level of signal is applied to them. Talking about uselessness of frequency range characteristic, we mentioned that headphones volume varies in the frequency range they play back – some parts are louder and some are quieter.

Based on which part of the frequency range the sensitivity is measured? Usually it is about 1000 Hz, as well as in the case of impedance.

The sensitivity of headphones is specified in either decibels per milliwatt dB/mW or decibels per volt dB/V .Sensitivity, expressed in dB/V, is convenient because with its help, without paying attention to impedance, you can compare different models of headphones, and, in particular, to determine how this or that model is suitable for use with portable devices. The optimum level of sensitivity for such headphones is not less than 90 dB/V.

Knowing the headphone impedance value, you can convert the sensitivity, expressed in dB/mW, to sensitivity, expressed in dB/V. There is the following formula for this:

Sensitivity dB/V = Sensitivity dB/mW +20Lg(1/ ,

Where R is the impedance of the headphone.

The maximum power – this parameter is in theory…

This parameter, in theory, should represent the maximum power of the electrical signal that can be fed to the headphones without risk of damaging the transducers. is usually greatly underestimated and has no practical sense.

What the parameters of the headphones tell us about how the headphones sound? Alas, no – so comparing technical characteristics of different models to choose the most suitable in sound is not possible.

We mentioned many times before that the right way to choose headphones is to go to the store and after listening to a few “candidates” make a choice. If you do not have such a possibility, we can recommend you to gather maximum information – reviews, measurements, feedback – about those models, among which you are looking for “your only one”, and make a decision on their basis.

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