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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Front bass car speaker system. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Speakers "Everything necessarily benefits, being used in its place." K. Prutkov The attitude towards inexpensive components in the car audio environment has a touch of snobbery. Yes, it is easier to work with cool brands, tricks are not needed. But this is not a sporty approach. It is much more interesting to achieve high results with public components. In terms of promoting the autosonic movement "in breadth" this is a more effective method, we must learn from the Bolsheviks. "Peace to huts, war to palaces!" One of my goals in creating this audio system is to prove that high quality sound doesn't have to be a huge investment. The key to success is a correctly chosen concept and an integrated approach to its implementation. The concept of this installation is a three-way front with full bass, the widest possible midrange, support for tweeters and a subwoofer only at the boundaries of the operating frequency range. This is an axiom. A full-fledged frontal bass can be obtained only in one case - cabinet speakers should be under the seats. None of the door mounting options provide full reproduction of the bass attack. With the existing location of the listeners near one of the speakers and the transverse propagation of the sound wave, the most "tasty" part of the range is compensated. The turn of the speakers in the doors, the high "beard" reduce the severity of the problem, but do not solve it completely. To do this, the radiation of the acoustic systems should be directed along the cabin, and the most logical thing is to install speakers under the front seats in a hard case. (On the issue of economy - the problem of vibration damping and door sealing disappears). The midbass operating frequency band under the seat is acoustically limited from above to 500-800 Hz, so three-way acoustics is a cruel necessity, not a whim. In addition, to obtain a good tonal balance and a cohesive sound stage, without chaotically moving instruments, the frequency of the section of the bass and midrange bands should be chosen no higher than 300 Hz. The next point is the placement of the midrange speakers. Three options are known: doors, kickpanels, dashboard. Installing the midrange in the door makes sense only when the driver is reclining, otherwise the speaker is too close and the sound is tied to it. The kickpanel installation does not have this drawback, but the edges of the soundstage are noticeably lowered. If you edit the stage with high-mounted tweeters, the instruments will inevitably "run up" in height. With a low frequency of the LF-MF section, the most promising option is to install mid-range speakers in a dashboard with upward radiation. This provides a stable stage height. In addition, in this version, you can install tweeters next to the midrange, or even install coaxial heads, realizing the idea of a coherent radiator. In this case, it is desirable to use heads with a paper cone - only it provides the most natural sounding of medium frequencies. Since paper cones of small size are not subject to the zone effect, the operating frequency band can not be limited from above, which again simplifies the task - no crossover is needed. Speaking of crossovers. Passive crossovers are the last century. In addition, there is no crossover frequency of 300 Hz in any ready-made three-way speaker system - it is unprofitable to wind colossal coils and put capacitors for hundreds of microfarads, not to mention the fact that each amplifier reacts differently to a complex load. Therefore, for front acoustics, you need to use bi-amping, it is not only more convenient, but also cheaper. The section of the LF and MF / HF bands is made by active filters, the selection of the tweeter band is done by a passive filter.
This concept has been developed for a long time and repeatedly tested on cars of different brands. However, I wanted to make not a pretentious demo car for exhibitions, but a simple everyday car that would not be embarrassing to show. Therefore, the key points of the installation must be visible, and the functionality of the vehicle must be fully preserved. An additional condition is minimal intervention in the design and modest labor costs. The search began for a car that would satisfy these difficult conditions. And such a car was found - Renault Kangoo. High front seats, ideally located places for speakers in the dashboard, excellent ergonomics. In addition, in this version of the car there is no left rear door, so the sidewall of the cabin is destined to accommodate the components of the audio system. Spartan interior trim, metal elements and a fantastic view evoke associations with the cockpit of an old bomber. Given my passion for aviation, the visual solution for the installation came immediately - aluminum, panels, shiny bolts. All work is done on our own in the garage and does not require high qualifications and special equipment.
Low-frequency heads - domestic 25GDN3-4. With all the desire to find an adequate replacement for them, it has not yet been possible - despite all the richness of the assortment of modern speakers, 13-cm heads are produced exclusively in the "door" version. A 7-liter bass-reflex case is also used here, the port tuning frequency is 45 Hz (designed by O. Leonov). Cases of low-frequency speaker systems are made of chipboard, covered with leatherette on the outside. The sides are decorated with MDF overlays, painted black. Each speaker system is rigidly connected to the seat frame and moves with it. The mid-range speakers are installed in the regular places of the dashboard. The paper cone provides the most natural sound, but the search for the right speaker has been a long one. Heads with a diameter of 10 cm were required, with a light (necessarily paper, not cardboard) diffuser, a sufficiently large stroke and a compact magnetic system. The last condition is dictated by the design of the torpedo. The competition, which included both home and car heads from different manufacturers, was won by Onkyo (KIA stock speakers). With reversed corrugation and a hard dust cap, they reliably reproduce signals up to 10 kHz. Here's another proof that stock speakers aren't always bad, you just have to use them the right way. Tweeters also went through a kind of casting. With such a wide midrange band, they are required to reproduce only the upper part of the range, so the choice fell on Hertz tweeters with an aluminum dome and a complete crossover. They are installed on a protective grid according to a cross-axial scheme, which turned out to be actually a point emitter. The sound stage at high frequencies is formed by a combination of two signals: a midrange signal reflected from the glass and a diffused signal, and a direct tweeter signal. At medium frequencies, the stage is formed mainly by a direct midrange signal (the directivity pattern in this range is quite wide). The system uses a budget class amplifier Prology PAS-4100 with minor modifications. The frequencies of the built-in crossover section have been changed, the quiescent current has been increased, the sensitivity has been deliberately reduced (the output of the head unit is 12 V). Although the maximum power of the amplifier is 56x2W, the power of each channel is limited to 4-100W. A large dynamic power reserve ensures undistorted reproduction of impulse signals (string pluck, percussion instruments). On live recordings, the atmosphere of the hall is perfectly conveyed. Although the front reproduces frequencies from 45 Hz reliably, a subwoofer is needed to support the bass range. Used active subwoofer Prology AT-1200, it is installed in the trunk and secured with screw lanyards. There were already brackets for securing luggage in the trunk, it only remained to install eyebolts on the subwoofer. To connect the power, a conventional power socket for electric stoves (380 V x 40 A) was used. You can empty the trunk for cargo in two minutes. Finally, the head unit. I have tried a lot of "heads", and the choice of a single din DVD player Prology DVD-100B is not accidental. The picture quality is very good, but that's not the main thing for me. Compared to traditional CD receivers, the sound quality of the DVD-100 is immeasurably higher, and the ability to watch videos is a nice addition for the money. I never listen to music on the radio (well, I can’t, I can’t stand this mockery of my ears), so I don’t need a receiver. And if you have a TV, you can find out the news without any hassle. (More about DVD-100B) The search for a TV, on the contrary, was short-lived. Almost immediately, I settled on the Premiera RTR-800Z model. Firstly, it is the maximum diagonal (8,4') that can be obtained for a reasonable price, plus an excellent "picture". Secondly, a strict design, logical control, a Russian-language menu, a good tuner and even Tetris. Thirdly, he perfectly fit into the place allotted to him in the middle of the dashboard. The screen does not block the view, and at the same time, the driver can always look at it without looking up from the road. For installation, it was only necessary to make a bracket ("leg" from the kit did not fit in size). You can remove and hide the monitor in "vandal-prone" places in a matter of seconds. The power circuit uses a 1F Prology CAP-1 capacitor and power wiring is done with 4 and 8 gauge cables (Prology and DAXX, DAXX distributors). In the system, the only ground point is at the negative terminal of the capacitor. Speaker cables - Prology, Oehlbach. Homemade signal cable, twisted pair in the screen (Canare). It had to be shifted twice before it was possible to get rid of the fuel pump pickups.
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Photo by A.B.Tikhomirov and in places by A.I.Shikhatov Author: A. Shikhatov; Publication: bluesmobile.com/shikhman
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