Created on 05/04/2015 02:10 PM.
Updated on 31.01.2020 23:12.
Author: Pavel Sayk.
The main problem in creating a high-quality car audio system is not achieving high power, low distortion, or even getting a good frequency response. The main challenge is getting a high and wide soundstage for the front listeners. Its solution is directly related to the place where the front speakers are installed. Do not think that the rear passengers have been forgotten: with well-placed frontal acoustics, the sound is balanced throughout the entire cabin.
However, solving this problem is associated with a number of problems. First of all, for any reasonable arrangement of the speaker systems in the front of the car, the difference in the signal path from the left and right radiators reaches unacceptably large values. To increase the effective distance from the listener to the acoustics (and, accordingly, reduce the travel difference), you can use the reflection of all or part of the signal from the windshield.
This is how installations with floor-standing front acoustics appeared. Those. the acoustics crash into the floor of the car in such a way that the signal, “falling” on the windshield, is reflected into the cabin with the most advantageous direction. The solution is complex and time consuming, but the result is impressive. However, not every “driver” “wrapped” in sound will be able to cut the floor to install the speakers, and besides, problems during technical inspection are guaranteed.
Therefore, there are not so many places for installing frontal emitters in a passenger car: the dashboard, windshield pillars, doors, kick panels, space under the front seats. None of the options solve the problem completely, moreover, the advantages and disadvantages of each of them are interrelated.
The main problem that arises when creating a high-quality car audio system is the choice of the number of bands and section frequencies. A centered (coaxial) front speaker system lacks the promise of a high-quality setup. An exception is the use of two-way coaxial loudspeakers as combined mid / high frequency emitters.
The two-way component front speaker system, like any compromise design, has several disadvantages. First of all, it is associated with layout constraints, and in this case it is difficult to get the right soundstage and good balance at the same time.
Best results can be achieved with a multi-way, diffuse front speaker. In our situation, “many” means “three”, a broad offensive of the four-lane systems is not yet foreseen. In this case, strip radiators can be placed in those places where they will work with maximum efficiency.
To obtain a high and uniform sound stage (equal at every point of the cabin), the easiest way is to raise the emitters as high as possible. The dashboard allows them to be installed at a sufficient height. The size of standard seats is usually limited to 10-13 cm, the acoustic design (the volume required for a high-quality speaker sound) is practically absent, so the low frequencies are not reproduced effectively enough.
Therefore, only mid-range drivers can be mounted in this location. However, this option has a number of serious disadvantages.
The main one is the “binding” of the sound to one side of the cabin due to an unacceptably large difference in the path of the sound wave from the left and right emitters. Among domestically produced cars, only Moskvich-2141 has real prospects for using the standard seats for their intended purpose.
A good result when installing speakers in the dash is possible in very rare cases, so enthusiasts are forced to look for other places to install the speakers.
Traditionally, woofer, full range or coaxial loudspeakers have been placed in the front doors. This is usually justified by an increase in the efficiency of low frequency reproduction by the finished acoustic design (the volume of voids in the door). In addition, most automotive heads are designed to handle high rear volume. But when the heads are installed “on the plane” of the door lining, the effect of compensating for the bass attack appears.
When mixing phonograms, most modern sound engineers place the bass register instruments in the center of the soundstage. The audio signals of the left and right channels in this frequency range are in phase and have practically the same intensity. Therefore, when installing emitters in the doors, the wave front at frequencies of 100-150 Hz, which is critical for the perception of a bass attack, reaches the opposite head in antiphase (which is determined by the width of the cabin) and is compensated (damped).
To reduce this phenomenon, when installing the speakers in the door, they must be turned up and towards the listener.
Usually satisfactory results are obtained by “aiming” the heads in the middle of the headlining above the front seats. This option is most rational when using two-way front acoustics with a relatively high crossover frequency (5-7 kHz).
The effect of compensating for bass attack largely depends on the installation location of the low-frequency radiators in the doors and the design features of the passenger compartment. The high tunnel and the extended console of the dashboard (“beard”) are a fairly good acoustic baffle. In the case where this screen excludes direct interaction of the heads, the effect of compensation for bass attack is reduced.
In such a situation, the installation of the heads “on a plane” is quite justified. This option is most rational with a relatively low crossover frequency in a two- or three-band system (1.5-3 kHz). Up to these frequencies, the radiation pattern of most LF / MF drivers is wide enough, which makes it possible not to pay special attention to their orientation.
On the other hand, it is possible to partially weaken the effect of “stuck” sound by equalizing the intensity at the mid and high frequencies, using the features of the directional pattern of the speakers used. However, phase shifts caused by signal path differences cannot be corrected in this way.
The installation depth of the heads in most cases is much greater than the available one, therefore, when installing the emitters in the door, it is necessary to make “podiums” (special housings) or ring spacers for the heads. In addition, in this case, it is necessary to make careful vibration damping (exclusion of vibrations) of the panels and door mechanisms.
The main problem of two-way acoustic systems with a low crossover frequency is the need to use high-power high-frequency heads with a sufficiently low natural resonance frequency. Their acquisition can be fraught with some difficulties. In addition, to effectively suppress the mechanical resonance of the moving system, located close to the crossover frequency, it is necessary to use a high-pass filter or special correction circuits.
When setting the bass …