Impedance
Impedance is the nominal electrical impedance of a speaker system. Nowadays, a set of standard impedance values are used; the most widely used speakers are
4 ohms,
6 ohms,
8 ohms and
16 ohms.
This parameter is of primary importance for passive acoustics (see "Type"). When connecting such speakers to a power amplifier, it is highly desirable that their impedance matches the speaker impedance for which the amplifier is designed; in case of a mismatch, either overload and distortion in sound (if the speaker impedance is below optimal), or a decrease in power (in the opposite case), are possible.
As for active acoustics, here the impedance is mainly of reference value — the speakers in such systems are initially selected for the corresponding amplifiers. However there is an opinion that a higher resistance reduces the level of interference and has a positive effect on the purity of the sound; however, the difference in impedance between different models is usually not so great that this effect is noticeable against the background of other factors that determine sound quality.
Bluetooth
The presence or specific version of the
Bluetooth module installed in the speaker system.
The most common way to use such a module is to broadcast sound from smartphones, tablets, laptops and other Bluetooth devices to acoustics. The main convenience of such a connection is obvious — it is the absence of wires and the corresponding freedom of movement, especially since the Bluetooth range is usually at least 10 m (within line of sight). However, note that without special technologies, the audio signal during such a transmission is highly compressed, which affects the final sound quality; so aptX support is required to achieve good quality (see below).
In addition, Bluetooth can be used for other purposes; the most popular option for such an application in the AU is remote control from an external device. However, such features are much rarer.
As for different versions of Bluetooth, they differ both in terms of bandwidth and accessibility. Here is a description of the different options used in the AU.
- Bluetooth v2.0. The oldest of the versions found nowadays. Provides only basic capabilities and up to 2.1 Mbps communication speed, and is also much more prone to compatibility issues than newer standards. Therefore, this version can be found mainly among frankly outdated acoustics.
- Bluetooth v2.1. An updated version of the 2.0 standard, which received a number of improvements regarding the compatibility of...different types of devices and connection security. It is a kind of "classic of the genre", all newer generations of Bluetooth are basically v2.1 plus various additions and improvements.
- Bluetooth v3.0. A version in which a high-speed channel of 24 Mbps was added to the basic capabilities of Bluetooth 2.1 — for exchanging large amounts of data. At the same time, the Bluetooth module automatically determines the amount of transmitted information and selects which connection to use — regular or high-speed.
- Bluetooth v4.0. A fundamental update (after version 3.0), which introduced another data transfer format — Bluetooth Low Energy (LE). This protocol is designed mainly for miniature devices that transmit small amounts of information. Nevertheless, it allows you to significantly save energy when working with larger equipment, such as speakers — in particular, the energy costs for transmitting small service data packets are reduced.
- Bluetooth v 4.1. Development and improvement of Bluetooth 4.0. One of the key improvements was the optimization of collaboration with 4G LTE communication modules — so that Bluetooth and LTE do not interfere with each other. So if a 4G smartphone is often in close proximity to Bluetooth speakers, it is desirable that these speakers have a module with a version of at least 4.1. Another interesting innovation is the ability to simultaneously use a Bluetooth device in several roles (for example, to remotely control an external device while simultaneously streaming music to headphones). However, this point is more relevant for signal sources than for speakers.
- Bluetooth v4.2. Further, after 4.1, the development of the Bluetooth standard. It did not introduce fundamental updates, but received a number of improvements regarding reliability and noise immunity, as well as improved compatibility with the Internet of Things.
- Bluetooth v5.0. Version introduced in 2016. One of the key innovations was two special modes of operation of Bluetooth low energy: speed up mode (by reducing the range) and long range mode (by reducing the speed). In addition, a number of improvements have been introduced regarding the simultaneous operation with numerous connected devices.
AptX
A feature found in Bluetooth speakers (see above) and generally highly desirable for such acoustics.
aptX technology is designed to improve the quality of Bluetooth audio. Initially, the audio signal is heavily compressed during this transmission, and the sound quality can end up being quite poor. But in
acoustics with the aptX codec, this drawback has been eliminated: this codec allows you to broadcast and receive sound in quality comparable to Audio CD — 16-bit / 44.1kHz. And although the actual sound quality of aptX is still somewhat inferior to the classic Audio CD with a wired connection, however, this point is most often not fundamental, and besides, the perception of sound is largely a subjective issue. Also note that in addition to the original aptX, a more advanced aptX HD can be used in modern technology — its capabilities are already being compared with Hi-Res audio 24-bit / 48kHz.
Of course, to use the appropriate codec, it must be supported by both acoustics and the signal source.
