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MessagePosté le: Jeu 30 Nov - 16:33 (2017)    Sujet du message: Twilight garden party costume? Répondre en citant

 Build this subwoofer for your car A 2 x 18-watt automotive stereo amplifier will provide a good match for original equipment factory or aftermarket stereos and provide the best price / power ratio. For systems with higher power separate components, a larger power amplifier and subwoofer should be considered to equal out the system. Speaker and enclosure To get the best value here, build your own enclosure and use a dual-voice coil speaker. A dual-voice coil speaker can be connected directly to both outputs of a 2 x 18 amplifier, eliminating the need for two speakers. This really cuts the cost in half. A single 8- to 12-inch dual-voice-coil woofer is adequate for systems that will not have to enter the whole neighborhood. Choosing the right speaker is important. Polypropylene cone speakers are preferred because they are resistant to moisture. The author used a Madisound No. 81524DVC speaker which has an 8-inch diameter polypropylene woofer and dual 4-ohm voice coils. It is available from Madisound for $ 34.
Building your own firm is not only a lot of money, it also helps you build your office with exactly the size and shape you want for your vehicle. This is important where space is where you would rent an obscure location. Avoid installing the crossover and power amplifier where they are subject to excessive temperature (such as in direct sunlight) or where they are exposed to moisture or dirt. For a professional touch, speaker box carpet is available in colors to match almost any vehicle interior, and it can be applied to the outside of the enclosure. Crutchfield, Parts Express, MCM Electronics, and other audio-supply distributors. The prototype subwoofer is housed in a 1.25 cubic foot enclosure, which is the best trade-off between size and bass response. This box volume provides a cutoff frequency of 37 Hz. The prototype is made of 3/4-inch particle board, and has been made from a PVC pipe. The computer-generated frequency response of the Madisound 81524DVC speaker in this enclosure is shown in FIG. 6 Installation The subwoofer can be mounted inside the vehicle or in a trunk. If you install it in a trunk, use quick-connects for the wiring and adjustable straps Velcro to keep the subwoofer from sliding around. This will also allow you to take advantage of the extra trunk room. Connect the crossover inputs to the left and right speaker of the stereo, as shown in Fig. 7. If the stereo has front and rear outputs, use the outputs that will be turned up for the loudest sound. Because the subwoofer crossover has a high input impedance, it does not load the receiver, The subwoofer crossover sums the signals from the left and right channels, so the left and right inputs are interchangeable. How to Replace Car Speakers Change Speakers in Car : Since the inputs of the crossover subwoofer are isolated from ground, the positive and negative inputs are also interchangeable. Be sure to observe the same polarity for both the right and the right channels. This interchangeability feature is particularly useful when the speaker is unclear. The crossover's phase switch can reverse the input polarity to provide the correct phase.
Use crossover to the power amplifier to prevent ignition noise pickup. Adding bass-blocking capacitors in line with each of the speakers is recommended, as shown in FIG. 7. This reduces the burden of reproducing deep bass. The capacitor values ​​with 4-ohm speakers for popular bass-blocking are listed in Fig. 7. Bass-blocking capacitors should be nonpolarized (bipolar). Use 135-Hz bass-blockers for most applications. Choose a higher frequency when the speakers are weak in your response. Adding a choke coil in series with each side of the dual-voice-coil subwoofer (see Fig. 7) will prevent power amplifier oscillation problems. The inter-winding capacitance or mutual inductance of dual-voice-coil subwoofers can cause some power amplifiers to oscillate. You can purchase choke inexpensively coils, or wind your own. Twenty turns of No. 22 wire wrapped around a 1/4-inch diameter steel bolt will provide an approximate value of inductance of about 20 microhenries. Power for the subwoofer crossover and power amplifier can be supplied from the automobile's + 12-volt ignition lead or from the remote turn on / power antenna lead. First power up Before turning the system on for the first time, set the volume controls of the subwoofer amplifier and the receiver to minimum. Set the cutoff crossover frequency control to maximum (fully clockwise). After turn on, increase the receiver volume. If it does not, check for short circuits or open connections. If sound comes from each of the main speakers, increase the subwoofer power amplifier level. Listen for bass from the subwoofer. If little or no sound is heard, try setting the receiver's balance control all the way to one limit. If this is one of the crossover inputs is connected backwards.… The most important step in adjusting the subwoofer is to set (and keep) the stereo's bass control at or below the flat (middle) position. Vehicle interior acoustics are notorious for overemphasizing upper bass frequencies. By turning the bass control down, the boomy-sounding upper bass is reduced. By adjusting the subwoofer crossover cutoff frequency for optimum sound, the subwoofer will fill a deep, solid sounding bottom end. Set the crossover polarity switch (S1) to a position that gives the most bass. Set the crossover Eq. switch (S2) in the "boost" position to increase deep bass frequencies and to help extend the subwoofer's response. Use the "flat" position if you hear distortion from the subwoofer. Adjust the crossover cutoff frequency and the level control of the amplifier to provide the best sounding bass. SOURCES Crutchfield 1 Crutchfield Park Charlottsville, VA 22906 (800) 955-3000 (car stereo components) Madisouns Speaker Components 8608 Green University PO Box 44283 Madison, WI 53744-4283 (608) 831-3433 (speaker building supplies) MCM Electronics 650 Congress Park Drive Dayton, OH 45459-9955 (800) 543-4330 (speakers, boxes, car stereo, electronic components) Express Parts 340 East First Street Dayton, OH 45402-1257 (800) 338-0531 (speakers, boxes, carstereo, electronic components) RELATED ARTICLE: PARTS LIST All resistors are 1/8-watt, 5%, unless noted. R1-R4--47,000 ohms R5, R6, R19, R21--10,000 ohms R7--20,000 ohms R8--16,000 ohms R9--3300 ohms R10, R11-9100 ohms R12, R14, R16, R23-2200 ohms R13--10,000 ohms, linear potentiometer tap R15--100,000 ohms R17--5100 ohms R18-1000 ohms R20--47 ohms R22--18,000 ohms Capacitors C1, C2 - .22 [micro] F, Mylar C3 -. 047 [micro] F, C4, C6, C7--0.1 Mylar [micro] F, C5--0.01 Mylar [micro] F, C8 Mylar, C9 - .22 [micro] F, Mylar C10--1 [micro] F, 25 volts, electrolytic radial, 105 degrees C C11, C13--10 [micro] F, 25 volts, radial electrolytic, 105 degrees C C12 --220 [micro] F, 25 volts, axial electrolytic Semiconductors Q1, Q3-Q5--2N3904 NPN transistor Q2--2N3906 PNP transistor D1, D2--1N914 diode IC1 - MF4CN-100 switched capacitor filter IC2-78L08 voltage regulator Other Components S1 - DPDT switch S2 - SPST switch J1, J2 - RCA jack, PC mount Miscellaneous: PC board, project case, hardware, 18 AWG stranded wire Note: The following items are available from MFR Engineering, 10308 Indian Lake Blvd S, Indianapolis IN 46236: * Crossover PC board (drilled and plated) - $ 10 * PC board and IC1 and IC2 - $ 14 * PC board and all electrical components including switches and jacks - $ 29 * Complete kit of all parts (includes PC board, all parts, and project box - $ 39 * Assembled and tested crossover unit - $ 59 Shipping and handling is included in all prices (Continental US). Certified gold cashiers checks, money orders, and personal checks accepted. (Shipping will be delayed


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MessagePosté le: Jeu 30 Nov - 16:33 (2017)    Sujet du message: Publicité

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