User manual ELECTRO-VOICE DH1012A
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ELECTRO-VOICE DH1012A SERVICE DATA (296 ko)
Manual abstract: user guide ELECTRO-VOICE DH1012A
Detailed instructions for use are in the User's Guide.
[. . . ] this design is roughly six inches, relating to a wavelength of 2. 26kHz. It should also be noted in the Figure 3 that a high frequency horn was employed above that frequency limit in order to achieve appropriate extended bandwidth and fidelity up to and beyond 10 kHz. This is a classic embodiment of a limited bandwidth line array and as we shall see in this presentation, only recently have solutions been brought to the state of the art to enable line array technology to truly be full bandwidth and extend beyond the 10-15 kHz region. Before we begin discussing bandwidth for modern day line arrays, it is important to begin with a discussion of basic radiation of sound. [. . . ] The array height Figure 17
There is, of course, a second way to achieve direction radiation. Figure 19 shows a single horn with radiating device (a compression driver) mounted to the back section of the horn. This small entrance, or throat, is coupled to the air via the length of the horn and the horn mouth. The velocity of air in that throat is represented by vt and the area of the throat is represented by at. Conservation principles require that: Figure 23, Equation 3 Let VD A D = V T A T VD = 4 in/sec A D = 4 in 2 A T = 1 in 2 VD A D = V T A T (4) (4) = V T (1) VT = 16 in/sec V D = velocity of diaphragm A D = area of diaphragm V T = velocity in throat A T = area of throat
The product theorem is shown in Figure 24, Equation 4. The explanation of this equation is very simple and again, is a key to our physical realization of an effective line array. The product theorem simply says that a simple source array has a multiplying factor that is described by the directional nature or "Q" of each horn loaded element. Or put another way, the result of a nonsimple array equals the simple array directionality plus the individual device directionality. It, again, is the a long vertical arrangement of simple point sources each spaced 12 inches apart. The frequency is 630 Hz and, again, is relatively long compared to the device spacing (in this case, the wavelength is 2 times the device spacing). Comparison of this polar with the same array where the simple sources have been replaced with horns, each bringing their own directionality, shows the change in vertical radiation. This is relatively easy to do with 15 inch and 12 inch drivers and as a result the realization of bass frequency line arrays is very straightforward.
For mid-band line arrays, if we are interested in frequencies between 250 and 1, 250 hz, the spacing needs to be 11 inches or smaller. Again, this is relatively easy to do with 6 inch or 8-inch drivers, and this is frequently the diameter of mid range devices in both large format and compact line array systems. This device basically takes the radiation of a compression driver and acts to produce both equal amplitude and equal phase sources at the front of the wave-guide. The full drawing in Figure 27 is 3 Hydras vertically stacked, thereby generating 21 "point source" radiating surfaces coupled to a horizontal wave guide with an included angle varying between 90 and 120 (model dependent). The driver is coupled to the input side of the hydra and the 7 outputs are then interfaced with a horizontal wave-guide to produce the required horizontal included angle. The space b for a hydra is . 826 inches, which equates to a wavelength of 16, 434 Hz. Again, it is always best for wavelengths to be longer than that spacing, so in this implementation, the Hydra presents excellent high frequency control in the 15kHz to 16 kHz range. The Array Show plot Figure 29 shows 21-point sources in a vertical orientation with the exact spacing provided by a hydra.
= 16, 434 Hz Figure 28
Realized Line Arrays/Horizontal Geometry
Figure 30 represents two possible methods of orienting a full bandwith line array. The high frequency section is in the horizontal center of the enclosure and is flanked by two mid drivers of 6 to 8 inch diameter and two low frequency drivers of 12 inch to 15-inch diameter (depending on individual realization). One of the advantages of an axis symmetric design is that horizontal response is the same either side of the center axis. Of course one of the consequences for axis symmetry is that devices now become horizontal "arrays". [. . . ] This is an obvious compromise in the full bandwidth control (or directivity index versus frequency control) of the system. With proper aiming, a 12 box high vertical line array of low frequency material can substantially improve the overall front to back SPL coverage of very low frequencies. Although this 12 box hang is nowhere near high enough to control 100 Hz and below, the improvement in uniformity of front to back is 5 to 10 times better than that of the groundstack. Because of that improvement in front to back uniformity, flying subs are highly recommended where improved full frequency coverage is required.
Line Arrays and Very Low Frequencies
Traditional practice with low frequency radiators, or subwoofers, has been to groundstack the subs. [. . . ]
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