SPECIFICATIONS Frequency Response in Recommended Vented Enclosure, 1 Meter on Axis, Half-Space Anechoic Environment, Swept One-Third-Octave Random Noise, 4 6 dB MC8A — 42-20,000 Hz MC12A — 32-11,000 Hz Low-Frequency Acoustic Power Output vs. Frequency, Small Signal, in Recommended Vented Enclosure 3-dB-Down MC8A — 50 Hz MC12A — 40 Hz 10-dB-Down MCSA — 37 Hz MC12A — 27 Hz Sound Pressure Level at 1 Meter, 1 Watt into Nominal Impedance, Anechoic Environment, 300-2,000 Hz Average MCBA — 97 dB MC12A — 97 dB Power Handling Capacity Long-Term Average MCSA — 12 watts MC12A — 20 watts Short-Term (10 milliseconds) MC8A — 120 watts MC12A — 200 watts Half-Space Reference Efficiency MCBA — 1.35% MC12A — 1.35% Amplifier Power Requirements, Continuous Average at 8 Ohms, for the Following Average Sound Pressure Levels, Mid-Band, in the Reverberant Field of a Typical Living Room (R=200) with Peaks 10 dB above Average (Long-Term Average Power Capacity not to be exceeded) Medium Level (85 dB SPL) MCSA — 1 watt MC12A — 1 watt Loud Level (85 dB SPL) MCSA — 10 watts MC12A — 10 watts Very Loud Level (105 dB SPL) MCBA — 100 watts MC12A — 100 watts Maximum Level MCSA — 120 watts (106 dB) MC12A — 200 watts (108 dB) Impedance Nominal MC8A — 8 ohms MC12A — 8 ohms Minimum MCSA — 7.5 ohms MC12A — 8 ohms Thiele-Small Driver Parameters, Nominal (see Special Note on Low- Frequency Performance section) fs Free-Air Resonance Frequency MCBA — 75 Hz MC12A — 50 Hz Qes Electro-Magnetic O at fg MCBA — 0.87 MC12A — 1.2 5 Mechanical Q at fg MCBA — 1.95 MC12A — 2.2 Qrs a o Toral Cat tg | ___ DE 2 [as + Qms МСВА — 0.60 MC12A — 0.78 Volume of Air Having Same Acoustic Compliance as Driver Suspension MCSA — 1.05 f13 MC12A — 5.1 НЗ Half-Space Reference Efficiency MCBA — 1.35% MC12A — 1.35% D Peak Displacement Valume of Diaphragm ( = Sp X max) MC8A — 1.9 in3 MC12A — 4.7 in3 So Effective Diaphragm Area MCSA — 30 in MC12A — 75 in2 Electro-Voice” a MARK IV company ЩИ АИ ВВ MICHIGAN componen Speakers Xmax Peak Linear Displacement of Diaphragm MCSA — 0.083 in MC12A —0.063 in PE(max) Thermally Limited Maximum Input Power MCBA — 12 watts MC12A — 20 watts Re DC Resistance of Voice Coil MCSA — 6.5 ohms MC12A — 7.5 ohms Cone Diameter, Nominal MC8A — 8 in MC12A — 12 in Voice Coil Diameter MC8A — 1 in MC12A — 2 in Magnet Weight MC8A — 10 oz MC12A — 13 oz Magnet Material MC8A — ceramic MC12A — ceramic Dimensions Overall Diameter MCSA — 8-1/4 in MC12A — 12-1/4 in Overall Depth MCSA — 3-3/16 in MC12A — 3-1/2 in Mounting Bolt Circle MCBA — 7-5/8 in MC12A — 118/16 in Mounting Hole Diameter, Four Evenly Spaced Holes MC8A — 7/32 in MC12A — 0.28 in Baffle Opening Diameter (Note: Frame does not permit front mounting.) MCBA — 7 in MC12A — 11 in Net Weight MC8A — 4 16, 2 о2 MC12A — 5 6,7 oz ELECTRO-VOICE COMPONENT SPEAKERS Electro-Voice component speakers have traditionally provided the hobbyist and professional with the flexibility of custom installation as well as the oppor- tunity for simple “building-block” system expansion and improvement. A comprehensive group of cone speakers, mid-fregquency horns and drivers, horn tweeters, crossovers, and accessories is available. Additionally, all Electro-Voice component speakers offer conversion efficiencies substantially higher(3 to 8 dB) than typical “bookshelf” home speaker systems. This high efficiency is essential for most professional audio applications. In the home it permits accurate reproduction of the high sound levels of live music or, for more normal listening levels, the use of amazingly small amplifiers for satisfactory reproduction. Electro-Voice cone speakers have now been thoroughly revised to reflect the latest knowledge of rational, optimized low-frequency speaker enclosure design. The result is a combination of extended low-distortion bass response, high efficiency, and modest cabinet size simply not available in other component speakers. PRODUCT DESCRIPTION The Michigan? MCSA and MC12A speakers are designed to provide full- range high-fidelity reproduction at modest cost. Both speakers are appro- priate for home music systems and the smaller MC8A may be used com- mercially in high-quality ceiling mounted sound systems. High-frequency output is enhanced by a centrally mounted free-edge cone whose dimensions and mass have been care- fully chosen for maximum performance improvement. The free-edge cone is small and light so it is able to respond to the extremely rapid high-frequency motions of the voice coil which the large main cone cannot follow. The MCBA and MC12A have die-cast frames which offer long-term stability not found in stamped-frame speakers. Also, the MCBA's frame is drilled to accept Electro-Voice TM5, TR5, and TR15 line-matching transformers. The characteristics of both speakers have been carefully developed to work well in vented (bass reflex) enclosures of small or reasonable size. In the recom- mended 2.4 cubic feet vented enclosure the MCBA provides essentially flat response to 50 Hz with usable output down to 37 Hertz. The larger MC12A, in its recommended 6 cubic feet enclosure, has essentially flat response to 40 Hz with usable output to below ЗО Hz. In addition, the MCSA may be housed in the small sealed ceiling- mounted boxes used in commercial applications. RECOMMENDED ENCLOSURES The MC8A and MC12A have been designed for mounting in vented boxes appropriate to the speaker charac- teristics. The use of a vented box with its tuned feature complements the per- formance of the speaker and provides maximum low-frequency performance consistent with size and speaker para- meters. A vented box not only increases the low-frequency power output but also reduces distortion for a given level, The MC8A may also be used in the small sealed enclosures found in ceiling- mounted distributed speaker systems. When used in this way low-frequency performance is considerably reduced but is usually adequate for commercial applications. In the listing below we have attempted to choose a typical vented box size that best complements the MC8A and MC12A. Other vented box sizes and tunings are quite feasible and may give performance more suitable for a partic- ular application. Two small sealed enclosures for the MCBA are also shown. For further information refer to the Special Note on Low-Frequency Performance section of this sheet and ask for a copy of Bulletin 10B. Explanation of Symbols: Vg Net internal enclosure volume, not including volume displaced by bracing, port, or speaker. Variations of + 10% are acceptable. fg Helmholtz resonance frequency of box-vent combination. fa Frequency at which the small signal (normal listening levels) acoustic power vs. frequency is down 3 dB relative to the mid-band output. f1p Frequency at which the small signal (normal listening levels) acoustic power vs. frequency is down 10 dB relative to the mid-band output. fi Usable low-frequency limit, the frequency at which the large-signal maximum acoustic power output vs. frequency is 10 dB below the maximum mid-band output (due to either thermal or displacement limitations). Dimensions for the two recommended vented enclosures are shown below: Ve MCSA — 2.4 ft3 MC12A — 6 ft3 Inside Depth (D) MC8A — 13 in MC12A — 17-5/16 in Inside Width (W) MC8A — 16-1/4 in MC12A — 21-13/16 in Inside Height (H) MC8A — 20-3/4 in MC12A — 27-1/2 in Port Area (XY) MCSA — 12 in2 MC12A — 16 in? Port Depth (L) MC8A — 2-3/4 in MC12A — 4-3/4 in Enclosure Vg Тв fa f10 fLL Unit Type (ft3) (Hz) (Hz) (Hz) (Hz) MCSA Sealed 0 120 88 88 MCBA Sealed 1 0 92 58 80 MCEA Vented 2.4 50 50 37 43 MCIZA Vented © 40 40 27 34 An outline drawing of a typical enclosure is shown below. и, ENCLOSURE CONSTRUCTION Speaker enclosures should be con- structed of rigid materials such as void- free plywood or particle board. In general, 3/4-inch thick material is most satisfactory, although smaller enclosures (approximately 2 cubic feet and under) may be successfully constructed of 5/8-inch material. It is mandatory that the joints between the pieces of wood be strong and well sealed. Simple butt joints secured with wood screws or nails and white glue are very satisfactory. Removable panels should be secured with wood screws and weather stripping tape. For joints longer than about 3 feet, internal glue blocks may be appropriate. In the largest boxes— greater than about 6 cubic feet—bracing is usually required for the largest expanses of wood to prevent sympathetic vibrations from affecting overall system performance. Proper bracing technique splits a rectangular panel into two equal rectangles with the brace placed along the panel's longest dimension. Good bracing materials are 2 X 2 dimension lumber or 4-inch widths of 3/4-inch plywood, placed on edge. Three mutually adjacent inside surfaces of the enclosure (top, one side and rear) should be lined with a one to two inch thickness of glass wool or similar acoustic absorptive material to prevent internal reflections from affecting mid- frequency performance. No absorptive material should be placed over or within the port. The location of the speaker on the mounting baffle is relatively unimpor- tant but close-to-ear-level mounting will provide best mid- and high-frequency performance in the listening room. The enclosure's height, width, and depth may be changed as long as (1) the internal volume remains the same (+ 10%) and (2) extreme differences between any two dimensions are avoided. The required port area can be obtained by any convenient combi- nation of width (Y) and height (X) as long as its long dimension is no more than five times the short dimension. The port is normally located on the front baffle board but may also be on any other box surface that has free access to the listening room. For most accurate box tuning the port should be no closer than several inches from the nearest adjacent enclosure wall. The port's proximity to the speaker is unimportant. SPEAKER INSTALLATION AND HOOKUP The MCBA and MC12A are designed for installation on the inside surface of the mounting baffle. As with all quality speakers care should be taken in mounting if best results are to be obtained. Drill four mounting holes and cut the mounting baffle opening in accordance with the dimensions given in the Specifications section. To mount the speaker, four carriage bolts with nuts and washers may be used. The MCSA frame will accommodate a 3/16-20 bolt and the MC12A will accommodate a 1/4-20 bolt. Wocd screws are not recommended. Secure the speaker to the baffle board just tightly enough to compress the speaker gasket. Excessive tightening is not neces- sary since the compressible gasket will forma satisfactory seal with only nominal pressure. To avoid any significant amplifier power loss in the speaker lines and undesirable change in low-frequency response, wire size must be properly chosen. 18 gauge stranded wire (commonly called lamp or "zip" cord) is satisfactory for lengths up to 38 feet, limiting the loss in sound pressure level to an insignificant 0.5 dB. If longer speaker lines are required, use progressively larger wire sizes: 16 gauge to 60 feet, 14 gauge to 96 feet, and 12 gauge to 150 feet. These lengths assume the 8-ohm impedance of one speaker. Two speakers in parallel have an imped- ance of 4 ohms, so if connected to the end of a single speaker line the lengths listed above must be halved. If it is desired to run the speaker line under a carpet TV twin lead may be used for short distances. Transformer Installation (MCBA) For constant-voltage distribution systems an Electro-Voice TM5, TR5, or TR 15 line-matching transformer may be directly mounted on the MCBA frame using the holes provided with two 6-32 x 1/4 self-tapping screws. PERFORMANCE IMPROVEMENT WITH BUILDING BLOCK KITS While both the MCBA and MC12A will provide quite adequate sound repro- duction under most circumstances, an improvement in performance can easily be realized by adding a tweeter and mid-frequency speaker. The tweeter will provide the most dramatic improvement and should be added first through the use of an HF1 High-Frequency Building Block Kit. The HF1 includes a TW35 horn tweeter, CR35 crossover/level control, wiring harness, and mounting hardware. In addition to extending the high- frequency response beyond the limits of normal audibility, the HF 1 provides more precise definition of high- frequency wave forms and much improved high-frequency dispersion in the listening area. The improved disper- sion makes it possible for the listener to move considerably off the central axis while experiencing very little change in sound quality. The MF1 Mid-Frequency Building Block Kit, comprised of an MR 10 horn/driver, CR 10 crossover/level control, wiring harness, and mounting hardware, provides additional improvement in performance after installation of the HF1. The MF1 further reduces the fre- quency range which must be reproduced by the cone speaker, reducing harmonic and intermodulation distortion in the system, The MR 10's diffraction horn improves dispersion in the listening area in addition to increasing efficiency. The improved mid-frequency performance provided by the MF1 is especially important because instrument and voice harmonics which determine the char- acter of the sound are found in this frequency range. SPECIAL NOTE ON LOW- FREQUENCY PERFORMANCE The recommended enclosures and associated performance specifications displayed earlier were determined in accordance with the definitive analysis о? А. М. Thiele, BR. H. Small, and others. The performance of speakers in sealed enclosures (including acoustic sus- pension types) has been well understood for some time. In contrast, vented systems have been designed using not much more than cut-and-try methods with little real engineering know-how. However, the above mentioned analysis has changed this picture completely. Thiele showed the similarity between a speaker in an enclosure and an electrical high-pass filter circuit. Application of well known filter analysis techniques led to quite accurate performance calcu- lations for any speaker mounted in any vented or sealed cabinet. Moreover, it was shown that a properly executed speaker /vented-enclosure combination held clear-cut advantages over a sealed system in the areas of efficiency, box size, low-frequency limit, and distor- tion. These results make the choices of box size, low-frequency limit, efficiency, power-handling capacity, and maximum acoustic power output rela- tively easy to make. In fact, Thiele even presented in tabular form quite a number of possible vented box choices having optimum performance charac- teristics (see A. N. Thiele, “Loud- speakers in Vented Boxes: Part |” J. Audio Eng. Soc., Vol. 19, May 1971, p. 388) By applying the work of Thiele and small, Electro-Voice engineers developed a computer program which easily, quickly, and accurately predicts the performance of any speaker-box system in the frequency range where the diaphragm is acting as a simple piston. The upper limit for this operation is usually the frequency at which the dia- meter of the diaphragm becomes a large traction of a wavelength. The Thiele-Small Driver Parameters shown in the Specifications section include the speaker characteristics re- quired by the computer program to develop the small and large signal per- formance of a given speaker and enclosure combination. For more information on this subject, ask for Bulletin 10B. It includes addi- tional vented enclosure recom- mendations for Electro-Vaice component speakers and a detailed bibliography of the work of Thiele, Small, and others. Also, where the Thiele-Small Driver Parameters are known, Bulletin 10B shows how to choose the size and tuning of a vented enclosure and how to determine the low-frequency response of vented and sealed speaker systems using scientific pocket calculators. WARRANTY (Limited) — Electro-Voice High Fidelity Speakers and Accessories are guaranteed for five years from date of original purchase against malfunction due to defects in workmanship and materials. If such malfunction occurs, unit will be re- paired or replaced (at our option) with- out charge for materials or labor if delivered prepaid to the proper Electro-Voice service facility. Unit will be returned prepaid. Warranty does not cover finish or appearance items or mal- function due to abuse or operation at other than specified conditions. Repair by other than Electro-Voice or its authorized service agencies will void this warranty. For correct shipping address, instructions on return of Electro-Voice products for repair, and locations of authorized service agencies, please write: Service Department, Electro-Voice, Inc., 600 Cecil Street, Buchanan, Michigan 49107 (Phone: 616/695-6831). Electro-Voice also maintains complete facilities for non-warranty service of E-V products. Specifications subject to change without notice. EY a MARK IV company. ELECTRO-VOICE, INC., 600 Cecll Street, Buchanan, Michigan 49107 MANUFACTURING PLANTS AT ll BUCHANAN, MI lB NEWPORT, TN I SEVIERVILLE. TN Ш REDMOND, WA Bl GANANOQUE. ONT © Electro-Voice, Inc. 1987 MW Litho In USA. Part Number 53013—613
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