The popularity of wireless headphones is growing every year. The trend is due to the convenience of their use, because the method of communicating with the device via Bluetooth does not involve burdening wires, which gives the user more freedom of movement. Gradually, smartphone makers are also abandoning the 3.5-millimeter headphone jack, forcing owners of modern devices to keep up with the times. At the same time, sound quality is not always attached to comfort. Good classic headphones often surpass wireless fellows in this parameter. But with the recent advent of Qualcomm's AptX technology, lovers of listening to music on headphones no longer have to choose between sound quality and usability. Now AptX, as well as AptX HD, can be seen more and more often in device specifications. What is the technology, how it works and what is needed to assess its capabilities, we will consider.
How to use wireless headphones.
What you need to know about listening to wireless audio
Let's start with what Bluetooth is. This is a kind of wireless data transmission over a short distance between compatible devices. The standard relates to wireless personal area networks (WPAN) and allows you to organize communication using radio waves. Radio communication is implemented in the ISM-range 2.4-2.4835 GHz, used in various devices, including home appliances, smartphones, computers and others. At the same time, the Bluetooth protocol supports both a point-to-point connection and a point-to-multipoint connection. The full transfer of music through Bluetooth technology is provided by the following characteristics of sound quality:
- Sampling rate (or sampling). This is the number of sound volume measurements per second, that is, the frequency with which the analog signal is converted to a digital array. The parameter is measured in hertz or kilohertz (Hz, kHz). So, the higher the sampling rate, the better the sound is transmitted.
- The depth of audio coding (bit resolution). This is the amount of data required to encode discrete loudness levels of digital audio, the parameter is measured in bits. In simple terms, the digit capacity determines the accuracy of the measurement of the incoming signal and the larger the bit depth, the higher the sound quality, and at the same time the volume of the sound file increases.
- Information transfer rate or bit rate. This is the amount of data transmitted per unit of time. In this case, we are talking about the transfer of sound data from the device to the headphones. That is, the higher the value, the more data during the same time is transmitted, processed, which improves the sound quality. Measured by kilobits per second (kbps or kbps).
Now consider what kind of technology AptX Bluetooth. This is an audio codec from Qualcomm, which allows you to transfer via Bluetooth, compress and unpack high-quality audio files. So, with the use of technology, we managed to achieve better sound, this is ensured by the fact that the losses are practically absent at the time of conversion into the digital, so the difference with the standard Bluetooth codec (SBC) is noticeable. An improved version of AptX HD uses dynamic coding, when most of the data is completely losslessly encoded, and if this is not possible, it reduces them to a minimum.
With all the impressive advantages of modern technology, the sound quality depends not only on the audio codec used, but also on the characteristics of the hardware (headphones, speaker). So, the supported devices should also be implemented at the highest level, it is definitely not worth expecting from low-power equipment with the stated support of the AptX-codec of pure deep sound.
What do aptX, aptX HD and LDAC mean?
All of these names indicate Bluetooth codecs that differ in the characteristics of data transfer. They have different parameters for the sampling frequency, audio coding depth and bitrate, respectively, and the sound quality will be different.
Audio codec that allows audio to be transmitted over Bluetooth as 16 bits at a sampling frequency of 48 kHz at a speed of 352 kbps. The analog signal is read 48 thousand times per second, transmitted with 16 bits, which corresponds to the parameters of the CD. It is a worthy alternative to SBC with less compression loss and better sound, cleaner and more detailed. AptX transmission speed is not the most impressive by modern standards.
The advanced technology provides even better sound quality with a lower delay, which distinguishes it from the previous version of the codec, AptX HD supports higher resolution audio. The sampling rate is also 48 kHz, while the digital signal is already stored with 24 bits, and the transmission rate is 576 kbit / s. The technology provides almost no loss of signal transmission. Technically, this is also a lossy compression format due to bandwidth limitations for this type of wireless transmission, but the codec maintains a dynamic range of at least 120 dB and sound frequencies up to 20 kHz, which in practice caused high sound quality with the least distortion.
High-resolution audio coding technology, called LDAC, is a development by Sony and today it offers the best sound quality and the highest bit rate. CD quality is implemented at a sampling rate of 96 kHz and a sampling depth of 24 bits with a maximum bitrate of up to 990 kbps. LDAC transmits three times more data per second and exceeds even AptX HD in parameters. The codec is actively used by Sony devices (smartphones, headphones, speakers, etc.), and starting with Android 8.0, it is part of the open-source Android project, which allows equipment manufacturers to include support for the standard in their devices.
What you need to evaluate aptX HD
If you want to experience all the delight of great sound with aptX HD on yourself, the standard for devices will be a prerequisite for this. And here it is supposed to work in tandem, so both the interfaced devices are required to support the technology, sending data, for example, a smartphone, and the receiver - headphones (speakers), otherwise SBC will be used, and the difference between codecs is noticeable. Backward compatibility is easier, devices with aptX HD support will be compatible with those that support aptX. So, for the implementation of this opportunity, you will need equipment equipped with a specialized chipset, a software solution is not provided.
What devices support AptX HD
Not at all in any equipment specification is now implemented, but the list of products from different manufacturers with AptX Bluetooth support is gradually growing. The list adds phones, tablets, headphones, headsets, portable players and others. Among those that can communicate using the AptX HD standard, some modern smartphones from LG, Xiaomi, Huawei, Motorola and other manufacturers, Astell & Kern players, headsets, headphones and other devices of various brands. You can learn more about the models that support the standard in question, you can on the site.