It is difficult today to find a person who does not use acoustic accessories. Especially now, when, to listen to high-quality music, just use a smartphone. But few people understand the abundance of technical indicators prescribed on the packaging and in the passport of the device. And even more so, not everyone understands what the electric impedance of the headphones is, how and what it affects.
What it is?
In this case, we are talking about electrical impedance. From the Latin language, the name of this phenomenon is translated as “obstruct”. In simple words, it means a combination of active and reactive (or reactance) resistances, the level of sensitivity of the headphones depends on this . It is measured in Ohm units (in the international system of units it is designated as Ω), named after the scientist Georg Simon Ohm. In accordance with the law established by him, the same audio accessories on completely different equipment can produce sound of different volume and quality.
Moreover, the packaging does not indicate the average resistance, but only its active component. This means that in reality deviations with the declared parameters are considered normal.
What is the effect of resistance?
The impedance of acoustic instruments affects a number of such indicators.
- Sensitivity. This parameter determines the highest volume level when applying a unit of power (1mW) until distortion appears. Low resistance gives high sensitivity and vice versa.
- Duration of work. Electricity consumption also depends on the resistance value. For example, for a smartphone, the optimal resistance value is 32 ohms. If you take a level of 22 ohms, the phone’s battery will be consumed by sound (playing files) - the charge will end faster. That is, the higher the resistance, the longer the energy will last.
- Sound quality. This indicator is responsible for such definitions as volume, transparency, brightness, coldness, naturalness, etc.
- Frequency response (frequency response or system frequency response) of acoustic instruments.
Indicators of different types of headphones
The range of impedance values for products varies from 8 to 600 ohms. And the most common headphones have an impedance of 16 to 32 ohms. There are also models of acoustic devices with an indicator of 64 ohms. Audio accessories are:
- high resistance;
- low resistance.
Their values depend on the principle of operation of the headphones. For example, devices with a small “earbud” type speaker with a value below 32 ohms are considered low impedance. And with an indicator of more than 32 ohms, it is considered high resistance. While full-size and overhead “ears” with a low rate have a resistance of up to 100 Ohms. And devices with a high parameter are characterized by an impedance of more than 100 ohms. How exactly the signal frequency reacts to the resistance level in different devices is clearly shown by the impedance curve. This is a graph of the change in this value, depending on the mode of operation.
Its essence is to identify the effect of resistance on amplitude and nonlinear distortions in the reproduction of sound.
For wired and wireless audio accessories such as traditional earbuds or plugs, the impedance curve is a straight horizontal line. It is characterized by the absence of any significant deviations in the range from 16 to 32 Ohms and in the range of frequencies of sound vibrations audible to the human ear - from 20 Hz to 20 kHz.
Full Size and Overhead
Most headsets of this kind have an uneven curve, which is characterized by a large take-off when playing at low frequencies and a slight rise at high frequencies. This suggests that sometimes the standard impedance of 32 ohms in reality may differ from the declared one.
Audio accessories with a balanced anchor (reinforcing) are miniature devices. But sound needs volume, so the lack of space here is compensated by the installation of additional driver emitters. Thus, they can be one-, two- and five-driver.
Such acoustic devices are characterized by a flat amplitude-frequency characteristic.
In isodynamic audio accessories with a planar emitter, the impedance curve is characterized by a straight horizontal line. When choosing such devices, you need to remember about their low sensitivity, although deviations are possible at high frequencies.
Which is better to choose?
The headphone impedance indicator depends on in combination with what equipment these acoustic devices will work. For example, for conventional stationary devices, audio accessories with a recommended resistance of 120-150 Ohms are suitable. And for a phone, tablet and player, values much less suitable, only 16-40 ohms.
For a computer, a music system, full-size high-impedance headphones with a resistance of up to 120 Ohms are needed. These are devices with an output voltage greater than 4 V. Only stationary devices connected to the mains can give such great importance. Therefore, for a bunch with them, you should choose accessories with the appropriate impedance.
With a high output voltage (more than 200 mV), it is better to choose "ears" with low sensitivity, with a resistance level of 32 ohms. They spend less on electricity. For the successful operation of high-impedance audio accessories, a special sound amplifier is required.
Its task is to equalize the characteristics of the amplitude and frequency. But we can’t talk about non-portable technology.
In devices of small sizes, the output voltage generally does not exceed 1 V, so the impedance in the headphones should not be high. Otherwise, the sound will become quieter. Using the same principle, you can determine what impedance is needed for a smartphone. The 1/8 rule can help match audio accessories with the source. It suggests that the source impedance level at the output should be 8 times less than the impedance in the headphones. For example 2 ohms to 16 ohms.
But if there is no way to calculate, remember the following.
- Low-impedance "ears" give greater volume, but reduce the battery life of the device. They are suitable for portable devices.
- High-resistance gadgets will sound quieter, but more economical to consume the battery. They are best used in combination with stationary equipment.
Here it’s worth deciding for yourself that the priority is the desire to enjoy sound at high volume or to conserve power economically. To select the appropriate headphones, you need to take into account the highest voltage level on which the output power of the device depends (Ohm's law). That is, with an increase in volume, the output voltage will increase, and the current will be consumed depending on the load resistance. According to this formula, a calculation can be made. To find out what kind of impedance is required for the device, you can try to find the optimal indicator blindly. You just need to listen to the sound on the middle parameters and move the Ohms values in the right direction.
Understanding such a technical indicator as resistance will help simplify the selection of suitable headphones and enjoy high-quality sound.
- Bowers & Wilkins P7.1 are low-impedance headphones with a standard range of sound frequencies. Carefully thought-out speakers clearly convey every note. According to customer reviews, accessories have only one drawback - the high price. But the high quality of the device corresponds to its value. These are the perfect gadgets to use with your iPhone. Model indicators: Frequency Response - 10 Hz 20 kHz; Impedance - 22 OHM; SPL - 111 dB (+/- 3 dB).
- Focal Spirit One is the main competitor of previous accessories. If you have a phone with a low power, you will need an amplifier for volume. In other cases, it fully reveals its potential. It is characterized by natural sound, good sound insulation and sufficient sensitivity. Compatible with players, iPhone. Device characteristic: Frequency Response - 40 Hz 15 kHz; Impedance - 36 OHM; SPL - 116 dB (+/- 3 dB).
- Audio-Technica ATH-CKR10 - acoustic devices with a good playback range and a sufficient level of sound insulation. Despite the “earbuds” category, in some respects they far surpass some of the models of full-sized monitor devices. On a smartphone, it is advisable to listen through an amplifier. Technical characteristic: Frequency Response - 5 Hz 40 kHz; Impedance is 32 OHM; SPL - 102 dB (+/- 3 dB).
- Beyerdynamic DR 990 Pro are high-impedance acoustic devices that are more suitable for professional use. Have superb clear sound quality. Unfortunately, due to the high impedance value, they are not compatible with non-portable equipment, including the iPhone. They require a separate amplifier or audio player with a powerful sound card. It has the following technical indicators: Frequency Response - 5 Hz 35 kHz; Impedance - 250 OHM; SPL - 96 dB (+/- 3 dB).
- Denon AH-D7100 - low-impedance headphones closed. From the Samsung phone they give out a detailed, clear, transparent sound. In combination with gadgets, Apple works quite loudly, but to fully reveal their capabilities, a high-quality source with an appropriate amplifier is desirable. Model Feature: Frequency Response - 100 Hz 10 kHz; Impedance - 30 OHM; SPL - 112 dB (+/- 3 dB).
- Final Audio Design Adagio II Indigo - portable in-channel devices with one driver. Light retro accessories are preferred by bass lovers. They have sufficient volume and perfectly convey all the nuances of music in combination with the phone and the iPhone. If you need a volume amplifier, then it is not needed for volume, but to obtain a low level of distortion. Accessories have a resistance of 18 ohms; range of reproduced frequencies: 40 Hz 15 kHz; volume level: 127 dB (+/- 3 dB).
- Ultrasone IQ - in-channel multi-driver hybrid type headphones. They use two different types of emitter (dynamic for the low frequency range and reinforcing for the high frequency). Combine the advantages of dynamic and reinforcing acoustic devices. Perfectly compatible with both iPhone and Android. Characteristic: Frequency Response - 40 Hz 15 kHz; Impedance - 19 OHM; SPL - 129 dB (+/- 3 dB).
See how to choose the right headphones for the player, smartphone or PC in the next video.