Comparison Polk Audio Monitor XT20 vs Polk Audio T15

Speaker sensitivity.

This characteristic is indicated on the basis of how loud the acoustics are capable of producing when a signal of a certain standard power is applied to it. Simply put, the higher the sensitivity of the speaker, the louder it will sound at the same output power of the amplifier. Thus, sensitive acoustics can be effectively used even in combination with relatively low-power "amplifiers". On the other hand, low sensitivity also has its advantages: it allows you to achieve a more uniform frequency response and reduces the likelihood of overloading the amplifier. In the least sensitive modern speakers, this indicator does not exceed 84 dB, in the most sensitive it is 95 – 96 dB or more.

Note that in fact, you have to pay attention to this parameter when acoustics are planned to be used with a separately selected power amplifier. Therefore, for active systems (see "Type"), sensitivity is purely a reference value, and, usually, it can be ignored when choosing.

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.

The crossover frequency provided in the speaker design.

A crossover is installed exclusively in a multi-band model (see "Number of Bands"). This is an electronic filter that ensures the division of the incoming audio signal into separate frequency ranges and directs each range to "its" set of speakers. And the crossover frequency shows where the boundary between these ranges lies. If there are more than two bands, there will be several such boundaries: for example, for a four-band system it may be specified "0.15 / 0.8 / 2.8 kHz" or "0.12 / 1 / 3.8".

In most cases, this parameter has mainly a reference value: the frequencies of the built-in crossover are selected to match the operating characteristics of the speakers installed in the speaker system.

The highest power rating of an amplifier that the loudspeakers can handle safely. Too much input power can damage the speakers, so when connecting, make sure that the amplifier's characteristics do not exceed the capabilities of the speakers. It is worth noting that this parameter may be slightly higher than the total nominal power of the acoustics (see below), since in this case we are only talking about the safety of the equipment, and not about the absence of distortion in the sound.

The total frequency range that the speaker is capable of reproducing. Specified from the bottom of the range in the lowest frequency component to the top of the range in the highest frequency: for example, in a 2.1 system with main speakers at 100 – 22000 Hz and a subwoofer at 20 – 150 Hz, the total value will be 20 – 22000 Hz.

The wider the frequency range — the fuller the reproduced sound, the lower the likelihood that some part of the low or high frequencies will be "cut off". It is worth noting here that the human ear perceives frequencies on average from 16 Hz to 22 kHz, and from a practical point of view, it makes no sense to provide a wider frequency range in speakers. However, quite a few models go beyond this range, sometimes quite significantly (for example, there are speakers with a range of about 10 – 50,000 Hz). Such characteristics are a kind of "side effect" of high-end acoustics, and they are usually given for advertising purposes.

Thus, the lower limit of the range in modern speakers can be within frequencies up to 20 Hz, however, higher values \u200b\u200bare more common — 30 – 40 Hz, 40 – 50 Hz, or even more than 70 Hz. In turn, the upper limit in most modern speakers lies in the range 19 – 22 kHz, although there are deviations both upwards (see above) and downwards.

Various additional features provided in the design of the speaker.

The list of such features may include general design nuances ( bipolar layout, magnetic shielding, horn design, Bi-Amping/Bi-Wiring), special types of emitters ( ribbon, electrostatic), adjustments to improve sound ( HF adjustment, LF adjustment, rotary tweeter), as well as special design elements to improve acoustic characteristics. Regarding the latter, it is worth noting that, in addition to the classic closed design, in our time you can find sound system with phase inverters( front, back or bottom), acoustic labyrinths, passive radiators and with acoustic spikes.

Here is a more detailed description of each of these features:

— Bipolar. Columns of this design have two sets of emitters directed in different directions at an angle to each other (usually about 90° or slightly more). Such sound system are used in some specific c...ases — in particular, bipolar models are considered a good option for the rear channel in a home theater.

— Rotating tweeter. A tweeter is a high-frequency speaker with a rotating design. This feature allows you to change the direction in which the speaker emits sound in the high-frequency range without pivotal the speaker body itself (recall that the correct localization of such sound is quite important for adjusting the sound of the system as a whole). At the same time, there is no particular need to provide this function in free-standing sound system: in such models, as a rule, there are no problems with pivotal the entire body. Therefore, rotating tweeters are found exclusively in built-in speakers (see "Installation") - after all, after installation, such a speaker no longer assumes any movement.

— Magnetic shielding. In speakers with this feature, the housings are supplemented with special materials that are impermeable to magnetic fields. Thanks to this, the powerful magnets that are usually equipped with speakers in modern speakers have virtually no effect on surrounding devices. This is especially important when used near sensitive electronics: plasma panels, high-end amplifiers and receivers, etc.

— Phase inverter. A device in the form of a characteristic tube installed in the speaker body with an outlet into the surrounding space. The phase inverter (PI) increases the sound pressure and improves the sound of the speakers in comparison with similar closed-type sound system ; this is especially noticeable at low frequencies. True, the movement of air in the tube can create additional noise; however, most models use various tricks designed to compensate for this phenomenon. But the clear disadvantage of such equipment is the increase in the overall dimensions of the speaker. We emphasize that this function should not be confused with the acoustic labyrinth (see below) - the PI is made straight and has a relatively short length.
It should also be noted that the phase inverter can be installed in different ways: most often in the front, less often in the back, in some models - below, and extremely rarely - on top or on the side. And in some speakers, two phase inverters are installed at once, with different locations. These details are not indicated in the specifications, since they can be easily determined from the photographs. From an sound system point of view, it is impossible to say for sure which location is better - each option has its supporters and opponents, especially since the issue of sound quality is largely subjective. But from a purely practical point of view, the front phase inverter is the most convenient: it allows you to place the speakers even close to the wall. With a rear location, the speaker system should be at least 3 - 4 cm from the wall, and ideally - not less than the diameter of the phase inverter. The third popular option - bottom installation - is found in some models of shelf and floor-standing speakers equipped with stands of the appropriate height, as well as in suspended models designed for a large amount of free space under the speaker.

— Acoustic labyrinth. Another device used to improve the richness and overall quality of sound. In some ways similar to the phase inverter described on top — it is also an air duct of a strictly selected length, connecting the internal volume of the speaker with the external space. The key difference is that in this case the air duct is not made straight, but in the form of a “snake” with many bends (hence the name “labyrinth”). The walls of the labyrinth are covered with special materials that absorb sounds. Such a design has a number of advantages over traditional bass reflexes. Thus, the speakers are more compact; with the same dimensions of the case, the labyrinth has a greater effective length, which has a positive effect on the power and richness of low frequencies; and the winding air duct is almost not susceptible to the occurrence of extraneous sounds (unlike phase inverters, where the design must be calculated very accurately to dampen such sounds). On the other hand, labyrinths are noticeably more complex and, accordingly, more expensive, and therefore are less common.

— Treble control. A control that allows you to adjust the sound level of high frequencies separately from the rest of the range. Due to this, you can change the color of the sound to a certain extent, without resorting to external equalizers and other complex devices. This function can be combined with bass control (see below), but there are also many speakers where only high frequencies are adjusted.

— Low frequency control. A control that allows you to adjust the sound level of low frequencies separately from the rest of the range. Like the HF control described on top, it allows you to change the sound color to a certain extent without resorting to external equalizers and other complex devices. However, this function is very rarely used without a high frequency control (although there are such speakers).

— Ribbon driver. A ribbon driver installed in one or more speakers of a speaker system; for a number of reasons, this design is used mainly in high-frequency tweeters. The difference between such devices and traditional drivers is that in this case, a metal ribbon is installed between the poles of the magnet instead of a traditional coil (hence the name). This provides a number of advantages: high sensitivity, minimal distortion, wide horizontal coverage. The main disadvantages of the ribbon design are its high cost and poor suitability for low frequencies.

— Electrostatic emitter. An electrostatic emitter installed in one or more speakers of the speaker system. The design of such a device is based on a thin and light membrane fixed between two stator grilles — a signal is fed to the bottom, and the membrane vibrates with an electric field. In this way, you can achieve very reliable, clear sound, with a minimum of nonlinear distortion. At the same time, electrostatic emitters are effective mainly at mid-high and high frequencies, so for effective operation, the speaker system inevitably has to be supplemented with traditional speakers. Among the clear disadvantages of such equipment, we can note the large dimensions, high cost and specific requirements for amplifiers: an emitter of this type requires a high-class "amplifier", necessarily with an output transformer. Therefore, this function is rare - in some premium speakers.

— Horn design. The presence of speakers in the speaker system built according to the horn scheme. Such a speaker has the form of a characteristic bell, in the depth of which there is a radiator. Due to the narrow directivity and specific influence on the propagation of sound waves, horns improve the efficiency of sound transmission in a fairly wide frequency range. In fact, it can be said that the presence of a horn increases the sensitivity of the speaker system. For a number of reasons, it turned out that the horn design of the main speaker is used mainly in information speakers (see purpose), while in other cases this form is provided for a high-frequency speaker (twitter).

— Passive radiator. The presence of a passive radiator in at least one speaker of the AC system. Such a device can be described as a low-frequency speaker from which the coil and magnet have been removed, leaving only the outer membrane of the radiator. This membrane oscillates due to sound waves created by conventional speakers and acts as a resonator that amplifies the sound of low frequencies. In this regard, a passive radiator is similar to a phase inverter and an acoustic labyrinth (see on top); however, unlike a bass reflex, it is almost not subject to the occurrence of extraneous noise, and is significantly cheaper than a labyrinth. On the other hand, an additional radiator on the front panel significantly increases the dimensions of the speaker — usually in height.

— IMAX Enhanced. The IMAX Enhanced certification mark is assigned to equipment that meets the audio device certification requirements of IMAX Corporation. In combination with DTS audio technology, it provides the signature sound “like in IMAX cinemas” at home. The most accurate reproduction of such audio is possible in systems with a large number of channels (from 5.1 and more). Note that for the effect of full immersion, IMAX Enhanced certification must also apply to video equipment for content playback (TV, projector, etc.).

— Bi-Amping/Bi-Wiring. The ability to operate sound system in the Bi-Amping or Bi-Wiring format. Models with this feature are multi-band (see "Number of bands") and have not one, but two sets of terminals for each speaker - for low and high frequencies. This allows the use of the on top-mentioned connection methods. Thus, when working in the Bi-Wiring format, each contact at the output of the power amplifier is connected with two separate wires to two terminals on the corresponding speaker at once: for example, the positive contact of the left channel - to the positive contacts of the low-frequency and high-frequency inputs on the left speaker, the negative - to the corresponding negative contacts, etc. This improves the frequency response: due to the division into separate cables, the low-frequency signal does not "steal energy" from the rest of the range, and each band receives enough power for the effective operation of the corresponding speakers. In the Bi-Amping format, two separate amplifiers are used, each with two pairs of contacts at the output - as a result, each speaker terminal is connected strictly to "its" contact. This connection method is not cheap, but it allows you to achieve even greater purity of sound and uniformity of frequency response; Bi-Amping is considered the ideal option for tech who do not accept compromises in matters of sound quality.

— Acoustic spikes. Supports of a special shape, used mainly in floor-standing speakers. In accordance with the name, such supports are made pointed, and it is the sharp ends that rest on the floor; special small plates are usually used to protect the floor from damage. In any case, the point of such a design is to minimize the area of contact between the speaker and the surface underneath it. This, in turn, increases the pressure at the contact points and minimizes the so-called parasitic vibrations — vibrations transmitted from the speaker to the floor. Acoustic spikes are considered an almost mandatory element of equipment for Hi-Fi class floor-standing speakers — without such equipment, the aforementioned parasitic vibrations can irreparably spoil the sound of high-class speakers and negate all their advantages. Note that speaker spikes are also sold separately; however, buying speakers initially equipped with such stands is often easier than looking for third-party accessories.

The diameter of the tweeter (speakers) speakers. Since size primarily affects the range of the speaker (as the diameter increases, the operating frequencies decrease), in HF components it can be quite small. More detailed information can be found in special sources.

The diameter of the woofer or combined woofer/midrange speaker(s). The larger the speaker, the lower its operating frequencies and the more sound power it can provide. Therefore, you should pay special attention to this parameter if you want to get high-quality rich bass - especially if we are talking about an audio system without a subwoofer. More detailed information about speaker sizes can be found in special sources.

The total weight of all components of the speaker system.