INFINITY 12DVQ
Service Manual

INTRODUCTION
A FEW WORDS ABOUT POWER HANDLING The power-handling capability of any woofer is related both to its ability to dissipate heat and to the maximum excursion limits of its suspension. Once the speaker�s voice coil moves outside the magnetic gap, power can no longer be converted into motion and all the amplifier�s power is converted into heat in the voice coil. Voice-coil heating is the greatest detriment to speaker longevity, so overexcursion should be avoided. Since excursion characteristics are very different for each type of enclosure, power handling will be different for each enclosure type. Sealed enclosures exert the most control over the motion of the subwoofer at the very lowest frequencies because the air inside the box acts as a spring, opposing the motion of the woofer�s cone. Larger boxes allow more excursion, providing more low-frequency output than the same woofer in a smaller box, for any input power level. When placed in a sealed box much larger than the equivalent compliance (Vas) of the subwoofer, it will perform as if it were in an infinite-baffle application, with the attendant lower excursion-limited power handling. Vented and bandpass enclosures allow the least excursion for the amount of sound output (near and above the resonance frequency of the enclosure). The mass of air contained in the port provides an acoustic load to the woofer�s cone at the tuning frequency, and this added mass decreases excursion so that the subwoofer�s motor is, essentially, coupled to the air in the port. Vented boxes do not provide adequate control below the frequency at which the box is tuned, Infinite-baffle, or �free air, mounting � allows for greater excursion than does mounting subwoofers in enclosures. The power handling of a subwoofer mounted in an infinite baffle will be reduced by nearly half its rated-powerhandling spec. Voice-coil overheating and burning have only one cause � exposure to too much power for too long. An amplifier driven into severe clipping or squarewave can output much more average power than the average power of a clean sine wave of the same level. Audible distortion in the sound is a clear indication of amplifier clipping and should serve as an indication that your speakers may be in danger of being damaged. so proper design and a subsonic filter are important. A vented bandpass box will allow the least cone excursion, provided a subsonic filter is used.

VARIABLE Q (PATENT PENDING)
Kappa Perfect VQ Series subwoofers are unique because they provide variable Q. Q adjustments may allow the subwoofer to be optimized for a particular enclosure or application and may provide the user with optimum performance for several applications in a single enclosure. The frequency response of every speaker includes three distinct regions characterized by flat amplitude (passband), high-frequency attenuation (stopband-high) or low-frequency attenuation (stopband-low) (see Figure 1). Midrange speakers and, to a lesser extent, tweeters are used to reproduce frequencies in the region where they exhibit flat frequency response. Subwoofers, on the other hand, are used in a region of lowfrequency attenuation, but those low frequencies are what we want the subwoofer to reproduce. Subwoofer system design is almost entirely an effort to extend the region of flat response to the lowest possible frequency or to shape the frequency response in the band of reproduced frequencies. Qes and, consequently, Qts are the parameters that best describe the behavior of a subwoofer in the range of frequencies it is most often used to reproduce.
� 1 0 dBSPL �15 �20 �25 �30 �35 �40 �45 �50 �55 �60 �65 �70
30 Hz 50 100 200 500 1K 2K 5K

SPL v s Fr e quen cy

Deg

180 150

LOW-FREQUENCY ATTENUATION

FLAT AMPLITUDE

HIGHFREQUENCY ATTENUATION

120 90 60 30 0 �30 �60 �90 �120 �150

�180 10K

Figure 1. Frequency response of a speaker.
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