User manual BLAUPUNKT VENTURA CD83

[. . . ] Safety precautions Before starting to mount your speakers, please read carefully the instructions on installation and connection. Disconnect the negative terminal of the battery before carrying out installation and connection work. Observe the vehicle manufacturer's safety instructions (regarding airbags, alarm systems, trip computers, vehicle immobilisers). [. . . ] When drilling holes, take care to avoid damage to vehicle components (battery, cables, fuse boxes). Do not mount the subwoofer onto flexible rear decks (hatchback vehicles) or anywhere where they may fall forward. SUBWOOFER ENCLOSURE TYPES Sound is created by the movement of the woofer cone back and forth. If a woofer cone moves forward creating a positive pressure wave, this same motion creates a negative pressure at the back of the woofer. If these two waves combine due to the lack of a wall separating the front of the speaker sound from the back, the output from the woofer is effectively cancelled thus substantially reducing the bass output of the speaker. This wall is absolutely necessary and is referred to as an acoustical "baffle". It can be accomplished using a box of some kind or simply the rear package shelf of an automobile to isolate the front and back waves of the speaker. COMMON ENCLOSURE TYPES In the car audio world there are five types of subwoofer enclosures commonly used: INFINITE BAFFLE, SEALED BOX (closed box), VENTED BOX (bass reflex), SINGLE-VENTED BANDPASS (often incorrectly referred to as "5th" order), DUAL-VENTED BANDPASS (often incorrectly referred to as "7th" order). No single design is superior because each has its own compromise in performance, power handling and design complexity. Care must be taken to avoid air leaks between the two woofers and final speaker wiring and impedance loads must be carefully watched. SUBWOOFER ENCLOSURE CONSTRUCTION Before starting final box assembly some basic construction issues should be mentioned: ­ Infinite baffle construction in a car is done by simply cutting a piece of wood which will act as an acoustical divider isolating the front and rear sound of the woofer. This piece of wood is mounted inside the trunk of the car under the rear deck, or against the back of the rear seat, and should have some kind of caulking to seal off all residual air leaks. Box construction can take on nearly any shape since we are dealing with low frequencies. Odd shapes that are difficult to cut and glue should be avoided. Particle board, MDF, or high grade birch plywood are good materials to build boxes of thicknesses of 19 to 25 mm. All seams in the box should be glued, screwed and caulked to prevent wall separation over time due to vibration and environmental changes within the car. Cross bracing is important for large boxes to prevent wall vibration. Acoustical damping material (sheep wool or fibreglass batting 5 to 10 cm thick), attached to 50% or more of the interior walls helps reduce box noise and also increases the box volume seen by the woofer by 10 - 20%. [. . . ] Acoustical damping material (sheep wool or fibreglass batting 5 to 10 cm thick), attached to 50% or more of the interior walls helps reduce box noise and also increases the box volume seen by the woofer by 10 - 20%. The application of self-adhesive damping mats to the inside walls also helps to eliminate wall resonances. The cables running from the amplifier to the subwoofer should be as short as possible with a cable cross section of at least 4 mm2. [. . . ]