S-40 Compact Monitor
low frequencies than typical actual program, adding an extra measure of reliability. Third, the test signal includes not only the overall “long-term average” or “continuous” level - which our ears interpret as loudness - but also short- duration peaks which are many times higher than the average, just like the actual program. The long-term average level stresses the speaker thermally (heat). The instantaneous peaks test mechanical reliabil- ity (cone and diaphragm excursion). Note that the sine wave test signals sometimes used have a much less demanding peak value relative to their average level. In actual use, long-term average levels exist from several seconds on up, but we apply the long-term average for several hours, adding another extra measure of reliability.
Specifically, the S-40 is designed to with- stand the power test described in the revised EIA Standard RS-426A. The EIA test spec- trum is applied for eight hours. To obtain the spectrum, the output of a white noise generator (white noise is a particular type of random noise with equal energy per band- width in Hz) is fed to a shaping filter with 6- dB-per octave slopes below 40 Hz and above 318 Hz. When measured with the usual con- stant-percentage bandwidth analyzer (one- third octave), this shaping filter produces a spectrum whose 3-dB-down points are at 100 Hz and 1200 Hz with a 3-dB-per octave slope above 1200 Hz. This shaped signal is sent to the power amplifier with the continuous power set at 120 watts into the 3.2 ohms EIA equivalent impedance, (19.6 volts true RMS). Amplifier clipping sets instantane- ous peaks at 6 dB above the continuous power, or 480 watts peak (39.2 volts peak). This procedure provides a rigorous test of both thermal and mechanical failure modes.
Protection Circuitry
Both the woofer and the tweeter employ in- dependent protection circuits to prevent against accidental overdrive and improve system reliability. In the woofer circuit, a solid state self-resetting switch is activated once the safe level to the woofer is exceeded (approximately 60 watts). This switch then inserts a high positive current coefficient resistor (HPCCR) in series with the woofer. The resistance of the HPCCR increases as
the drive level to the woofer increases and limits the power being delivered to the woofer. The HPCCR is similar to a lamp and will produce light that is visible thru the port when activated. This is an indication to reduce the gain of the power amp if output compression is to be avoided. The maximum acoustic output is achieved just before the protection circuit is activated.
The tweeter protection circuit behaves in a similar manner, except a fixed resistor is used in place of the HPCCR which attenuates the power to the tweeter by approximately 6 dB.
Installation Notes
On the back of the S-40 are (2) 1/4"-20 threaded inserts. These are intended to be used with mounting systems which have 2- 3/8" mounting centers, such as the Omnimount Systems Series 25.
A U-type bracket, the S-40MB is also avail- able. This will allow the S-40 to be mounted on walls or ceilings. A microphone stand adaptor is also included. Complete mount- ing instructions are included with the S- 40MB.
Care should be taken to ensure that the cho- sen fixing point is strong enough to support the S-40. Care should also be taken to en- sure that the S-40 is not exposed to direct precipitation.
If the speaker system is not used with one of the mounting brackets, such as on a book- shelf, then the rubber feet that are included with the S-40 should be attached to the speaker. If the speaker is placed on the bot- tom side, then a rubber foot should be at- tached to each of the two rear corners only. This will compensate for the 3° draft that is molded into the cabinet, and allows the baffle to sit perpendicular to the surface that the speaker is placed on. If the speaker is to be placed on its side, then a rubber foot should be attached to each of the four corners. The nameplate that is attached to the grille may be rotated depending on which mounting ori- entation is used.
Architects' and Engineers'
Specifications
The loudspeaker shall be a two-way system consisting of a 13 cm (5-1/4") low-frequency
loudspeaker, 2.5 cm (1 inch) high-frequency loudspeaker and frequency dividing network installed in a vented enclosure. The divid- ing network crossover frequency shall be 3,500 Hz. The dividing network shall in- clude protection circuits for both the low- frequency loudspeaker and the high-fre- quency loudspeaker. The loudspeaker sys- tem shall meet the following performance criteria: Power handling, 120 watts per EIA RS-426A. Frequency response, … 3 dB from 85 Hz to 20 kHz. Pressure sensitivity, 85 dB SPL at one watt, 100 Hz to 10 kHz meas- ured at a distance of one meter on axis. Im- pedance, 4 ohms nominal, 3.7 ohms mini- mum. The enclosure shall be molded of high impact polystyrene structural foam. The unit shall be 24.9 cm (9.8 inch) high, 17.8 cm (7.0 inch) wide, 15.0 cm (5.9 inch) deep. The loudspeaker system shall be the Electro- Voice model S-40.
Limited Warranty
Electro-Voice products are guaranteed against malfunction due to defects in mate- rials or workmanship for a specified period, as noted in the individual product-line statement(s) below, or in the individual prod- uct data sheet or owner’s manual, beginning with the date of original purchase. If such malfunction occurs during the specified pe- riod, the product will be repaired or replaced (at our option) without charge. The product will be returned to the customer prepaid. Ex- clusions and Limitations: The Limited Warranty does not apply to: (a) exterior fin- ish or appearance; (b) certain specific items described in the individual product-line statement(s) below, or in the individual prod- uct data sheet or owner’s manual; (c) mal- function resulting from use or operation of the product other than as specified in the product data sheet or owner’s manual; (d) malfunction resulting from misuse or abuse of the product; or (e) malfunction occurring at any time after repairs have been made to the product by anyone other than Electro- Voice Service or any of its authorized ser- vice representatives. Obtaining Warranty Service: To obtain warranty service, a cus- tomer must deliver the product, prepaid, to Electro-Voice Service or any of its autho- rized service representatives together with
