The sound in the car: theory and practice
It is known that for many motorists machine turned into something more than just a means of transportation. After all the person conducting the wheel a few hours a day, wants to listen not only local news, but good music. However, tooling salon high quality automotive reproducing installation, little who can do only industrial products.
In recent years Amateur literature there were many publications, dedicated to independent manufacturing car audio equipment, basically amplifiers. But even a good amplifier still does not solve all of the challenges confronting the Creator of the audio system Hi-Fi class for your car. Skeptical the attitude of many motorists to such systems childbirth caused, first of all, illiterate approach to AC in the cabin. To unfortunately, in most cases, their placed in the car on the principle of "where fit", not "where necessary". However, a definite answer to question - "where do we need?" - not exists. Any known solutions does not give guaranteed result. It is much easier to answer to the question "where?". The common mistake - placing powerful and high-quality heads, the speakers on the rear shelf. Front same set that have or nothing at all. Do the owner of such a machine prefers sit with your back to the stage?
Contrary opinion, the main thing with auto design the audio system is not achieving high power, small distortion and not even getting good frequency response. The main problem is create a wide sound for anyone sitting on the front car seats. The solution directly connected with the place install front heads.
In any a reasonable version of their placement in the cabin is the difference between the signal path from the left and right speakers before the listener reaches unacceptable large values. To reduce this difference can be used the reflection of all or part of the signal from the windshield. So there was install front floor acoustics (see Fig. 1).
Constructive an embodiment of such a decision is quite it is difficult and time consuming, but the result impressive. However, to cut the floor for installation heads will be decided far not every. Therefore, for real install front radiators a car is not so so many places: dashboard, the windshield pillar, door, the vertical bar at the bottom salon at the front wheels of the vehicle.
Instrument the Board allows you to set emitters, and high enough but the size of the heads are usually limited 10...13 cm, acoustic design virtually no, so low frequencies are reproduced in this case is not enough effectively. For further lifting the sound pattern can to install the transducers on the racks on the side edges of the windshield, but there really can fit only the tweeters(the tweeter).
Popular in because of its simplicity to install low-frequency and coaxial heads in car doors usually the rationale behind the increase effectiveness of reproduction low frequencies are willing acoustic design. The same result it turns out the opposite desired. During the mixing of phonograms most modern sound engineers has tools-bass in the center of the sound stage, i.e. sound the signals of the left and right channels in this frequency range common-mode and have almost the same the intensity. Therefore, when installing emitters in the door the front sound waves at frequencies of 100...150 Hz, critical for the subjective the perception of bass attack reaches the opposite head in the opposite phase (that is determined by the width of the cabin) and compensated. Hence dull, lifeless sound, which is not to fix any EQ. Installation heads in bukanlah reduces the difference in the way the signal from the left and right emitters, but sound picture falls unacceptably low. In addition, this variation is inherent in the same effect "blanking" bass attack, though to a lesser to the extent that when installing heads in car doors, and to organize a decent acoustic design is not easy.
It follows, that the best result can be achieved by applying multiband restrictocin front speakers. Strip emitters should be placed in places where they will work with maximum efficiency. In the author's opinion the best place to install bass radiators in buildings under the front seats with sound radiation forward-up. MF emitters should be placed on the front panel or in the upper front corner of the door, and HF on the racks windshield (this raises the sound image).
Full bass performance is only possible when using acoustic design of considerable size, therefore, in almost all automotive audiostrobe frequency range of the main channels is limited to 100...120 Hz, and lower frequencies are radiated by a subwoofer as the total signal. Since the lowest frequencies, the loudspeaker has a circular radiation pattern, the choice the installation location of the subwoofer question layout of the system. Most often it is placed in the trunk. The problem is that the frequency response of the salon, which plays here the role of acoustic design has the rise in the region of low frequencies, for each individual model of the body. Therefore, to obtain uniform total response of the system must have the ability to adjust not only the level but also the frequency characteristics in subforeman channel.
The sound image formed without the use of rear speakers, of course, be incomplete. Their main value - creating effect of the hall" by simulating the reflected sound. The spectrum of the signal rear channels (Fig. 2) it should be limited , and the signal can be either traditional (left and right channel), and total or differential or a combination thereof. Power rear channel not Vilik (not more than 10% of the total capacity of the system), and in some cases for its implementation will require additional amplifying devices. The simplest case is a counter-consistent inclusion of rear heads between the outputs of the amplifiers left and right channels through a simple filter.
On the influence of the connecting cables on the sound of a recently written so much that the topic here is not to touch. The cross section of the power wires should correspond to the consumed current and the length of the wires themselves. In any case, the voltage drop on the power cable at maximum power should be not more than 0.1...0.2.
Damping of spurious resonances elements and soundproofing of the cabin are also important. - Attenuating material should be applied to all of the available panels and plastic body parts, the special emphasis panel, located near the heads of the speakers, or those used as part of a speaker enclosure. Resonances usually disappear when the cover 25 percent or more of the square. To absorb road noise sound-absorbing material should cover Poliana, fireproof bulkhead and the area of the wheels.
Author: tolik777 (aka Viper); Publication: www.cxem.net