User manual ELECTRO-VOICE TL880D EDS

[. . . ] Directivity The directional characteristics of the TL880D were measured in Electro-Voice's large anechoic chamber; the test signal was one-third-octave filtered pink noise at the frequencies indicated. A full spherical measurement system was used, which is compatible with the AcoustaCADDTM computer-aided design program. All directional information was measured at 20 feet. [. . . ] The TL880D has also been power tested with a two-hour sine wave, at minimum impedance, so that competitive comparisons can be made using consistent methods. Continuous program power is defined as 3 dB above (double) the continuous sine-wave power rating. Subpassband Speaker Protection Below the enclosure tuning frequency, cone excursion increases rapidly. Since acoustic output is also falling rapidly, there is no utility in driving the system with signals much below tuning frequency. While such signals may be in the program material, they are often extraneous, such as a dropped microphone. The Electro-Voice EX-24, XEQ-2 and XEQ-3 electronic crossover/equalizers can provide the necessary subpassband protection. The 3-dB-down points are 30 Hz (EX-24 and XEQ-2) and 16 Hz or 32 Hz (XEQ-3). Other high-pass filters are available and onethird-octave equalizers can also be effective at providing the required protection. Use In Multiples Cone loudspeakers may be stacked for greater acoustic output and a narrower beamwidth. (It is assumed that all cones are operating in unison or "in phase. ") This principle is already employed in the dual-woofer TL880D, and is responsible for the higher sensitivity and narrower vertical beamwidth (with the system long axis vertical) relative to similar single-woofer systems. In addition, two TL880D's can be used side-by-side and their combined performance will be different from that of a single TL880D in the ways outlined below. At relatively low frequencies, below about 150 Hz for typical TL series dimensions, stacking produces additional acoustic output without altering dispersion. When a common signal is applied, a 6-dB increase in maximum acoustic output occurs. The cones "mutually couple" and act as one cone with twice the area (therefore twice the efficiency) and twice the power capacity. The additional cone area provides 3 dB more output and the additional power capacity accounts for the remaining 3 dB. Specifically, mutual coupling occurs at frequencies whose wavelengths are longer than one-quarter the center-to-center distance between the cones. The highest frequency at which mutual coupling occurs is calculated from the following equation: 3, 000 f @ ---------- , DMAX where DMAX (inches) is the distance between the cones, and f (Hz) is the highest frequency at which coupling occurs. When DMAX is greater than one-quarter wavelength, which would occur if two TL880D's were widely spaced, or at frequencies much above f even when closely spaced, the increase in acoustic output is limited to the 3-dB power-handling increase. [. . . ] Electro-Voice Speakers and Speaker Systems are guaranteed against malfunction due to defects in materials or workmanship for a period of five (5) years from the date of original purchase. The Limited Warranty does not apply to burned voice coils or malfunctions such as cone and/or coil damage resulting from improperly designed enclosures. Electro-Voice active electronics associated with the speaker systems are guaranteed for three (3) years from the date of original purchase. [. . . ]