Electrovoice 205-4t 参考指南

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greater the overlap, the more uniform the coverage — and the higher the cost. Budgetary 
constraints tend to favor sacrificing density, so the optimum center-to-center 
configuration is, in practice, the least common of the three.  The illustration below shows 
these various layout patterns. 
Ceiling Systems – Size 
vs. Coverage 
In the past system designers 
usually specified 8-inch cone 
loudspeakers for distributed 
overhead systems, at least in 
part because they represented 
the traditional choice.  The 
EVID systems however allow 
for far more flexible options. 
In many cases, you can achieve 
excellent results — at a significant savings — by using 4-inch elements.  This is true in 
jobs that do not require extended low-end response or high SPL levels.  4-inch elements 
such as used in the EVID the C4.2 offer wider dispersion to allow for fewer speakers to 
be employed in the job. 
For example, due to its smaller cone diameter, the C4.2 exhibits significantly wider 
dispersion (130 degrees) than the C8.2 (110 degrees) at the -6 dB points. 
The effect of this characteristic on an overhead system is indicated in the illustration 
below. In replacement applications where existing speaker positions are used, the C4.2 
(shown in angle “A”) offers greater overlap and, thus, more uniform coverage than an 
older conventional 8-inch unit (shown in angle “B”. When specifying a new system, you 
can take advantage of the C4.2’s wider dispersion to decrease the number of speakers 
required to cover a given area. 
This will result in even greater 
savings.  
Of course, the C4.2 is 
somewhat less sensitive than 
the 8-inch C8.2.  The 
difference is –7 dB.  The C4.2 
will also have slightly reduced 
low-frequency capabilities 
below 90 Hz. 
Neither of these factors is a 
significant problem in many distributed systems, however. The C4.2 is conservatively 
rated to handle 50 watts of continuous power equal to or greater than most other brands 
of 8-inch units so its continuous SPL output will be more than adequate. Moreover, its 
reduced output below 90 Hz can easily be overcome with the addition of the C10.1 
subwoofer. For these reasons, the C4.2 represents a great way for you to maintain good