Experienced readers will remember the many articles about improving the quality sound speaker systems < = 10-1, S-90 (35 ° C-212), etc., which regularly published in the magazine "Radio" in the 70s and 80s years. With the advent of on the domestic market, imported audio the interest in this topic, in theory, should be to fade, but as shown by the editorial mail, it is not so. In operation there are a lot of domestic products, which are now pretty easy "bring to mind" - the benefit of any materials and audiophile materials are available to all. One such "upgrade" we now describe. Two days (not counting time, spent on thinking and the acquisition of the necessary details) our experimenter Konstantin sky managed "to put a voice" one of the best (if not the best) domestic sound system 75 ░ C-001. Sure, his tips will help to enhance the sound of any "shovels" columns.

Speaker system 75 ░ C-001 (150 ░ C-001) under the name "Corvette" and "jib" produced plants "Oceanpower" (Leningrad) and "Red Beam" (Red Beam) respectively. The "Corvettes have been produced much more than "Jibs". And in the one and the other models exactly the same sets of speakers, schematic and design. However, the "Red beam" in addition to columns produced a set of speakers for both options, AC, and therefore, some audiophiles still believe that the "jib" in native speakers sound better than "Corvettes". Possible the reason for this are the "innovations" that are implemented in the process of serial production of the latter. For example, with time has been simplified formulation of multicomponent compound for impregnation of the cone of the midrange DS-1 excluded internal vibration of the housing.

75 ░ C-001 are the latest development of VNIIRA them. Popova (Leningrad), introduced into production, and became a kind of "Swan song" of our quested. When the design for the first time in domestic practice widely applied mathematical modeling and optimization parameters heads and barrier filters using a computer. In addition, the speakers have a number of other advantages. First, they are effective speakers (GD-3, DS-1 and 10ГLW-4) new generation, which allowed to achieve a record (late 80's) sensitivity 91 dB(W/m). The calculation circuits for computers has provided a wide range frequency 25-25000 Hz with a little uneven frequency response and small the level of distortion. Secondly, the use of fotokorrektsiya chains in the scheme of the separation filter and accommodation in one the plane of the centers of radiation of RF and CQ-heads allowed significantly improve the uniformity of the phase response. Thirdly, large the enclosure volume, low resonance frequency and the large diameter diffuser nizkochastotniki provide deep enough and powerful bass.

Finally, in the construction of the separation filters used coil air-core, coiled high quality copper with heavy gauge wire and metal-paper capacitors MBGO which has small loss and distortion. Circuit elements mounted on cardboard base using surface mounting. To unfortunately, in this ointment are several hefty honey spoons. The greatest contribution to the damage of the sound make too long wires from ordinary "luzanky" and numerous elements of the protection circuit, which is sound the signal to the speakers. This was partly justified: powerful 75 ░ C-001 could be used not only in domestic but also for the articulation of cultural houses, small discos etc Knot contains, besides 2 relays, transistors 9, 3 LEDs, 18 of conventional diodes, resistors 40 (!) and 8 capacitors. And all this stuff one way or another included in the audio chain! Numerous experiments have shown that due to high sensitivity to cause an overload in the living room almost impossible, especially when you consider that according to passport data, short-term input power can to achieve 300W.

In short, in real conditions of use from the BONDS no, while the sound of the suffering badly. With busovaca, despite the absence in his chain of relay contacts, the situation is not much better. LF components are also through an ULTRASOUND and the fuse on the 5A. All this leads to a substantial increase in the length of the wires of small section does not audiophile quality. Same cable used when mounting the filter Board, which is made too not the most optimal way: the elements are connected between an additional jumper soldered to the pistons Board. This further increases the total length of wires in the way the audio signal. Now, finally, understand the reasons unsuccessful attempts to make the sound of the AU with more worthy using audiophile speaker cables. Obviously, even the best of them are not able to compensate for the loss the quality of the internal wiring.

Incidentally, the input screw the clamps 75 ░ C-001 also leave much to be desired. The design of their of the pads is such that does not allow connection "breastbone" and "spatulas", providing convenient and reliable connection. More or less satisfactory results are achieved when the clamp them in the stripped cable, but the screwing portion of the terminal lived extrudes. Well, finally, it was surprising for such a paltry large the internal volume of the amount of damping material inside of the housing. According to reference data in a 75 ░ C-001 should be applied fibrous material ATM-1 superthin glass fibers bonded with a phenolic resin. However, in appearance the silencer is very reminiscent of conventional viscose wool. Because this spurious emissions audio back bass diffuser leads to the formation of standing waves. In addition, reflected from the rear wall of the casing wave affects the backside the diffuser, causing tightening of the front signal. As a consequence muffled and boomy sound at lower levels.

So, on the basis of the above identified the following main directions of the "upgrade":

  • the exception is unnecessary elements from the audio circuits;
  • replacing the internal conductors from on high oxygen-free copper;
  • the optimization scheme of connections to reduce the length conductors;
  • replacing the input connectors on the powerful screw terminals;
  • lining the internal surface of the effective sound absorbing material.

    Upgrading the speaker system 75 ░ C-001. Part 1

    The proposed revision was spent about 200-300 rubles and 2 man-days. You will need: 6-8 m acoustic cable oxygen-free copper (OFC) with the cross-section 2.5-4 sq mm (about 10-20 $ /m); two pairs of screw clamps, preferably gold plated, universal design, allowing you to connect "bananas", "spatula", "forks" and the bare wire (40 rubles); two air filter for kitchen cleaners (sold in stores, 20 USD/PCs); a little construction sealant or clay.

    After you have created the necessary material base, to begin the autopsy. It is easiest to perform, having laid the patient's "back" speakers up. Now we recommend adhering to the following sequence operations.

    First removed the covers of the speakers, and then out of the housing removed and themselves. In this case, all connecting wires neatly otbivayutsja. Be especially carefully when removing nizkochastotniki HTN-3 - this process due to the considerable weight dynamics is a a very difficult task. Then Unscrew the nameplate Board display and de-solder the connecting wires from the LEDs. After sealing the hole Board LEDs and signboard set on a former place.

    Then through the hole bass head, you can start dismantling the crossover boards and TIES. But first you need unsolder the wires from the input terminals and sockets SG-5 on the back the wall of the housing and Unscrew the 6 nuts on the perimeter of the filter Board. Retrieved boards are separated from each other, after which the ULTRASONIC ejected.

    In the next phase of work is necessary to remove all the conductors connecting the on-Board filters, or vypayat biting the side cutters. There also removed the resistors R6, R7 and R9 (the factory). Now RF-head directly is connected parallel to the resistor R4 ("plus" to C13). Accordingly, basovich must be connected in parallel the chain C12-R3 ("plus" to C12). Thus, electric scheme crossovers are much simpler.

    Now we have to replace the internal wiring. In this case when mounting the filter Board was used speaker cable Vampire Wire OFC Speaker Cable cross section 2.5 sq mm. They are connected to the midrange and tweeter speakers. In the circuit nizkochastotniki (from the crossover to the input terminals) was used wire with a larger cross-sections of conductors up to 4 sq mm., its it is desirable to solder with regard to the preferred direction the current flow (typically coincides with the direction of the marking). It should be borne in mind that the sound character of the majority speaker cables can be considerably improved after several hours of listening. So it will be not superfluous pre - "warm up" new conductors, urging them before starting installation.

    And some more practical advice. To reduce the number of connecting wires, it is advisable to opt out from the use of mounting clips on the Board of filters, and instead, they apply the findings of resistors and capacitors, pripaivaya other circuit elements directly to them. For reduce the influence of the return current of a powerful basovich on the chain Midrange and tweeter heads connecting the minus bus WOOFER, midrange, and RF links to the negative input bus should only be done in the same point. For this purpose it is convenient to use the appropriate the capacitor C8 or C11.

    After that, the fee of the crossover set on the old in the case of the acoustic system.

    For the installation of new input terminals need to remove the round the plastic cover on the back wall of the speaker and remove old, then be drilled open hole to the desired diameter. After the installation of the clamps to them from the inner side connect the wire from the Board of filters (if not to solder it will have to use connectors "forks", which is tightly are screwed with nuts on the inside). Then cover with connectors set on a former place.

    Now you can start connecting and installing the loudspeakers. I advise you to measure line segments connecting cable with a small margin, as this will simplify the operation. First mounted the midrange. Since DS-1 there is no polarity markings of the findings, it should be determined by using a 1.5 volt battery, noting the displacement of the diffuser when changing its polarity. Setting MF-head, it is desirable to seal the opening to enter his Boxing connecting wires. Then installed "Squeaker", after which the speakers are covered with decorative the nameplate. The second ends of the connecting cables the speakers are soldered to the terminals of the respective the filter elements on the Board.

    Before mounting nizkochastotniki acoustically need to shadenfreude internal volume of the housing. It is best to do this suitable filler for kitchen cleaner representing a finely fibrous synthetic material. One sheet will be enough. It is bonded "Point" to the side and rear walls of the housing opposite the holes WOOFER. The filler can to use ordinary technical wool or rayon, placing them into the case. When determining the optimal number wool is recommended to adhere to the norms for optimal damping: 8-11 kg per cubic meters of internal volume.

    The latter operations are connecting to the Board basovich the filter and its installation in the housing of the column, and the installation decorative ring-lining on the loudspeaker.

    Well, now you can start the most enjoyable part - listening modified columns and the evaluation of the results. Subjective examination of sound "Corvette 75 ░ C-001 SE" was conducted by connecting them to the stereo in the composition CD player Sony CDP-761E and amplifier Sony TA-F511. In quality interconnect cable used half-meter pair Monster Cable Interlink 300, and the acoustic - two-meter segments Jamo cross section of 4 sq mm.

    To start with dial "in Our city" (Annex to "The cabin AV" 3/98) they checked the correctness of the connection phasing speakers in the columns. If everything was done correctly, when playing a common-mode virtual sources the pink noise source is located exactly halfway between columns, and in antiphase - "run up" to the acoustic systems. Otherwise, before carrying out further auditions makes sense again carefully check the correctness of installation.

    Then the sound of the speakers was assessed using the most records different musical genres, including classical and popular music: "The best of Mozart" (1996 Karussell International), "The best of the Batch" (1996 Karussell International), "Famoust balet" vol.1 and 2 ("The rose collection/Elar music a/s 1992), Paul Mauriat - "Nostaljazz" (Philips 512 146-2 DDD 1992 Phonogram), The Beatles - "Please, Please Me (Parlophone/EMI) The Beatles - "Rubber Soul" (Parlophone/EMI), Deep Purple - "Machine Head" (EMI) and etc.

    Compared to the original version, the sound of the AU significantly changed. Especially noticeable change occurred in the medium and high-frequency ranges. The sound was truly transparent and crystal clear, while he was enriched with the finest the musical nuances and details that otherwise would not hear . For example, the rustle of the brush on the plates was reproduced extremely accurately, while in the original the embodiment of the speakers, their sound had several noise-like character. The changes clearly benefited and low frequency range: the bass was noticeably more clear and collected. Throughout likely, this is due not only to the introduction of absorbers inside the body, but also improve the damping basovich through the use of a much more low-impedance cable with large cross-section. In short, the effectiveness of the obvious upgrade and pay all the costs of its the holding.

    Are there provisions to further improve the quality sound 75 ░ C-001? Significant improvement can be expected necessary, as the proposed measures allows eliminate the most obvious blunders and flaws in their scheme and design. However, a little "Polish" and "lick" them, probably possible. For example, by mounting a second pair of screw clips, and adding the option of connecting to the power amplifier and method bi-wiring. It is possible that, picking up to 75 ░ C-001 other types speaker cables, you can get them more balanced and refined sound.

    Replacement metal-paper capacitors in the circuits of the passage of sound the signal on the Board of the filter on an equal capacity polypropylene or other audiophile can give perceptible to the hearing result. Finally, there is now a huge selection of different vibration-absorbing gaskets and washers for installation speakers, special coatings for pasting internal the surface buildings. But we should not forget the principle of reasonable sufficiency: each subsequent improvement will be to cost more and more expensive. Especially when you consider that 75 ░ C-001 have a number of fundamentally fatal flaws.

    First, the large width of the front panel inevitably leads to diffraction sound waves, and as a consequence, to the color and sound uneven frequency response. Secondly, a large distance between WOOFER and Midrange loudspeakers leads to the fact that more or less a uniform sound field in a wide band of frequencies provided a minimum distance of 2-3 meters from the speaker, and in small spaces they sound very peculiar. Third, powerful unshielded magnetic system WOOFER and Mid-range speakers do not permit their use in systems "home theater". Fourthly, despite the high sensitivity, 75 ░ C-001 do not work well with tube amplifiers, as heavy basovich requires effective damping low output impedance. There is a "fifth" and "Sixthly"... But in any case, if you know and like anything to do with their hands, any alterations you get real pleasure.

    Author: Konstantin sky, Salon AV; Publication: www.hi-fi.ru, www.cxem.net

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