ONE GOOD, AND TWO IN ONE - BETTER?
The test of coaxial speakers, alas, did not confirm their theoretical advantages over broadband.
Georgy KHOKHLOV, Anatoly FOMIN
This time, the object of our test was inexpensive two-way coaxial speakers with a diameter of 10 cm or 4 inches. Their characteristics correspond to the needs of not the most demanding customers, which, however, are not satisfied with the sound from primitive broadband speakers. Moreover, the installation of coaxial speakers is not more complicated, because, as the name implies, the centers of radiation of the low-frequency (LF) and high-frequency (HF) heads are located on the same axis, although they are not completely combined.
In theory, coaxial speakers should have at least two advantages over broadband. Firstly, a wider radiation pattern, and secondly, a more even frequency response of sound pressure. That is the theory. Quite different results are obtained in practice.
To get “first, ” you need tweeters with a small (preferably domed) membrane and a powerful magnetic system. But since they are quite expensive, they use cheap and large (30–40 mm) tweeters with a classic diffuser.
The woofer is used in the entire frequency range, as well as in broadband speakers. As a result, standing waves arise between the low-frequency diffuser and the “bottom” of the “tweeter”, which prevent the second advantage from being realized. As a result, we can say that the directional coaxial speakers are no worse than broadband ones, but the uniformity of the frequency response is not fully achieved. The failure caused by the reflection of sound waves between the bass and treble heads is especially characteristic. Fortunately, it is rather narrow and does not spoil the sound too much.
Most of the speakers presented for the test are made in China. Exceptions are Kenwood from Malaysia and Pioneer from Poland. Workmanship is very high, can not be compared with Chinese products two or three years ago. For the worse, only the “Pyramids" stand out - there are noticeable drips of glue from under the magnet and the o-ring is jammed. But in the end, they are the cheapest.
The mounting depth of all speakers is small and makes it easy to install them in any door.
On the graphs - the frequency response of sound pressure. The green curve in the graph of the frequency response (frequency response) of sound pressure is obtained along the axis of radiation, and the red curve at an angle of 50 ° to it. The higher and smoother the characteristic, the better.
PHILIPS GTP 1020
A distinctive feature - fixing eyes with perforation, which allows you to break off the "extra" when installed in a regular place. As usual, the speakers of this company have a good seal between the rim and the plastic frame of the protective grill. Both heads (LF and HF) with cardboard diffusers, and the “tweeter” is quite large in size. Nevertheless, the developers managed to achieve an acceptable frequency response both along the radiation axis and at an angle to it. The level of nonlinear distortion is not the lowest, but quite acceptable. It is especially important that it does not increase much at low frequencies (8.8% at 110 Hz). Perhaps this is the only speaker from the six, capable of providing truly high-quality sound. Therefore, he took the deserved first place.
The appearance of the speaker is not admirable. A very large membrane type tweeter (diameter 45 mm) is somehow not installed directly. The low-frequency diffuser is made of cardboard with special impregnation. The frequency response along the axis of the speaker is not the best, but the picture is almost exemplary at an angle. Alas, the “tweeter” here is too weak and poorly reproduces the highest frequencies.
A curious design feature is the selection of the characteristics of a low-frequency speaker. It is able to reproduce frequencies below its own resonance. Unfortunately, in the range 200–300 Hz, the characteristic is bulged up by as much as 5 dB. When installed in the door, this range will be even louder, contributing to a booming (like from a barrel) sound. Only a low price allowed the Pyramids to get ahead of the Pioneer and take the final third place.
Traditional design: a low-frequency speaker diffuser - polypropylene, high-frequency - a membrane with a diameter of 40 mm. The suspension of the main diffuser is oilcloth. An impressive magnet of a tweeter is noteworthy - in cheap loudspeakers they do not use expensive, but very effective neodymium magnets, so you have to take it by weight.
In the center of the main diffuser there is a special non-radiating corrugation, which helps to weaken the characteristic resonance at a frequency of 4 kHz.
The main advantage of the Sony XS-102F is the very low level of non-linear distortion in the entire frequency range - only 0.5% versus 1.5–2 for the rest. The only pity is that there is a clear “blockage” at the top. If not for this, the loudspeakers could claim a place higher than the second.
Very simple in appearance and uncomplicated in design. The basket has a cheap zinc-chrome coating, but the technological level of the company is indicated by the highest sensitivity with a small magnet.
The low-frequency head with a polypropylene diffuser makes a very favorable impression. Nonlinear distortion at medium frequencies is small, although at lower it is worse (15.7% at 170 Hz).
The whole picture is spoiled by a weak “tweeter”. Her contribution to the sound palette is so small that even the thought arose whether it works at all. Tests of the second speaker confirmed the results of the first, and suspicions did not materialize. However, only fourth place. The high price contributed to this.
KENWOOD KFC 1066
The zinc-chrome protective coating on the basket immediately indicates the simple origin of these speakers. But the "tweeter" with a membrane of metal foil looks advantageous. In shape, it is transitional from domed to conical, so that both the dome and the adjacent cone emit sound. The brand name of the device is “Balanced Dome”. However, other advantages of the tweeter were not noticed - it barely masters frequencies above 14 kHz. And the high resonant frequency of the woofer does not allow him to reproduce a little more deep bass.
A characteristic design feature - “tweeter” is located very close to the main diffuser. Due to this, the failure caused by the interference of sound waves between the LF and HF heads has moved to a frequency of 6 kHz, where it is not so noticeable to hearing. But impartial equipment recorded it even at an angle of 50 ° to the axis.
In general, the frequency response is so-so. Even the low level of nonlinear distortion at all frequencies (except low) does not save. The logical result is the fifth, last but one place in the tested six.
In appearance, these speakers are simply chic. The translucent blue material of the diffuser, outwardly similar to polypropylene, gives them elegance. A high side made of hard plastic provides reliable sealing of the case and frame.
The loudspeaker has a remarkably even frequency response, with the low-frequency part being especially attractive. Unfortunately, this is where the virtues end. Firstly, it has the lowest sensitivity. This means that to obtain sound pressure, such as that of Kenwood or Philips, you will have to apply more than two times more power.
Secondly, at any significant volume in the RCF RC-104, noticeable distortion occurs. Their value is unstable and is not directly related to frequency or power. It seems that in the material of the diffuser there are elastic-plastic deformations, which is completely abnormal. To complete the sound picture at a frequency of 185 Hz, the body of the tweeter begins to resonate.
It is easy to guess that RCF products took the last, sixth place.
DOUBLE-BAND SYSTEMS OF THIS PRICE CATEGORY ($ 22–35) DID NOT REVEAL ADVANTAGES BEFORE BROADBAND. The technical solutions used in them did not allow to realize the advantages of the layout. For those who are interested in better sound quality, we recommend looking for “two-way” expensive.