Electro-Voice SP12C User's Manual
Contents
1. FREQUENCY PERFORMANCE The recommended enclosures and associated performance specifications displayed earlier were determined in accordance with the definitive analysis of A N Thiele R H Small and others The performance of speakers in sealed enclosures including acoustic suspen sion 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 How ever 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 calcula tions 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 relatively easy to make In fact Thiele even presented in tabular farm 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 Gulton Industries In2. SPECIFICATIONS Frequency Response in Recommended Vented Enclosure 1 Meter on Axis Half Space Anechoic Environment Swept One Third Octave Random Noise 6 dB SP8C 41 12 000 Hz SP12C 37 10 000 Hz SP15A 34 8 000 Hz Low Frequency Acoustic Power Output vs Frequency Small Signal in Recommended Vented Enclosure 3 dB Down 10 dB Down SP8C 50 Hz SP8C 36 Hz SP12C 43 Hz SP12C 32 Hz SP15A 40Hz SP15A 30Hz Sound Pressure Level at 1 Meter 1 Watt into Nominal Impedance Anechoic Environment 300 2 000 Hz Average SP8C 95 dB SP12C 100 dB SP15A 103 dB Power Handling Capacity Long Term Average Short Term 10 ms SP8C 25 watts SP8C 250 watts SP12C 25 watts SP12C 250 watts SP15A 50 watts SP15A 500 watts Half Space Reference Efficiency c 0 9 SP12C 1 9 SP15A 3 5 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 SP8C 1 4 watt SP12C 0 66 watt SP15A 0 36 watt Loud Level 95 dB SPL SP8C 14 0 watts SP12C 6 6 watts SP15A 3 6 watts Very Loud Level 105 dB SPL SP8C 140 watts SP12C 66 watts SP15A 36 watts Maximum Level SP8C 250 watts 107 dB SP19C IAN watts 111 dR Impedance No
3. 10 5 16 in SP12C 17 1 4 in SP15A 19 in Port Area XY SP8C 4 3 in2 SP12C 30 4 in2 SP15A 33 1 in Port Depth L SP8C 2 6 in SP12C 3 4 in SP15A 3 2 in An outline drawing of a typical enclosure is shown below 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 appro priate 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 perfor mance Proper bracing technique splits a rectangular panel into two equal rectan gles 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
4. 5 1 8 in Overall Depth SP8C 4 3 4 in SP12C 6 1 8 in SP15A 7 in Mounting Bolt Circle Diameter SP8C 7 5 8 in SP12C 11 9 16 in SP15A 14 9 16 in Bolt Hole Diameter 9 32 in in all units Mounting Hole Number SPSC 4 SP12C 8 SP15A 8 Baffle Hole Diameter Front Mounting SP8C 7 1 4 in SP12C 11 1 16 in SP15A 14 in Rear Mounting SP8C 7 1 8 in SP12C 10 15 16 in SP15A 14 1 8 in Net Weight SP8C 7 Ib 2 oz S P190 11 Ih 17 a7 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 frequency 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 s
5. artic ular application For further infor mation please turn to the section of this sheet entitled Special Note on Low Frequency Performance If additional information is needed please ask for a copy of Bulletin 10B The low frequency performance of these three vented enclosures is summarized below SP8C___SP12C__SP15A Ve 1 23 56ft3 75ft3 fg 47Hz 43Hz 40Hz fa 50Hz 43Hz 40Hz fio 36 Hz 32Hz 30Hz fie 40 Hz 34 Hz 31 Hz Vg Net internal enclosure volume not including volume displaced by bracing port or speaker Varia tions of 10 are acceptable fg Helmholtz resonance frequency of box vent combination f3 Frequency at which the small signal normal listening levels acoustic power vs frequency is down 3 dB relative to the mid band output f10 Frequency at which the small signal normal listening levels acoustic power vs frequency is down 10 dB relative to the mid band output ft 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 three recommended vented enclosures are shown below Vg Volume SP8C 1 2 ft8 SP12C 5 5 ft3 SP15A 7 5 ft3 Inside Height H SP8C 16 5 16 in SP12C 27 1 4 in SP15A 31 1 8 in Inside Width W SP8C 13 in SP12C 21 1 2 in SP15A 23 7 8 in Inside Depth D SP8C
6. c 1983 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 fraction of a wavelength The Thiele Small Driver Parameters shown in the Specifications section include the speaker characteristics required 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 additional vented enclosure recommena ations for Electro Voice 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 repaired or replaced at our option without charge for materials or labor if
7. 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 Ceci Street Buchanan Michigan 49107 Phone 616 695 6831 Electro Voice also maintains complete facilities for non warranty service of E V products Specifications subject ta change without notice Part Number 53001 614 a GUILON company ELECTRO VOICE Inc 600 CECIL ST BUCHANAN MICH 49107
8. e largest unit of the SP series The 78 ounce magnet is the same as that used on the EVM18B high power music speaker The voice coil is also the same and this combination leads to sound pressure levels about 8 dB above that produced by the SP8C The SP15A can be used for excellent performance as a very low frequency woofer with essentially flat output down to about 32 Hz There are very few musical instru ments producing signal in this very low frequency range Even with this perfor mance the enclosure is not so large as to be unwelcome in the usual listening room The vaice coil of edge wound aluminum wire makes maximum use of the space within the magnetic gap In addition the light weight aluminum results in improved performance at higher frequencies for a speaker this large RECOMMENDED ENCLOSURES The SP series of loudspeakers 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 output but also reduces distortion for a given level In the following list we have attempted to choose a typical vented box size that best complements the SP8C SP12C and SP15A Other vented box sizes and tunings are quite feasible and may give performance more suitable for 3 p
9. ions section To mount the speaker four or more carriage bolts with nuts and washers may be used The SP8C will accomodate four 9 32 inch diameter bolts while the SP12A and SP15A will accomodate eight bolts of the same dimension Wood screws are not recom mended for mounting the speaker Secure the speaker to the baffle board just tightly enough to compress the speaker gasket Excessive tightening is not necessary since the compressible gasket will form a satisfactory seal with only nominal pressure To avoid any significant amplifier power loss in the speaker lines and undesire able 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 output 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 an impedance level of one speaker or 8 ohms Two speakers in parallel have an impedance of four ohims 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 PERFORMANCE IMPROVEMENT WITH BUILDING BLOCK KITS While the SP8C SP12C and SP15A will provide quite adequate sound repro duction under most circumstances an improvemen
10. minal Minimum SP8C 8 ohms SP8C 6 7 ohms SP12C S8ohms SP12C 6 7 ohms SP15A 8o0hms SP15A 6 2 ohms Thiele Small Driver Parameters Nominal see Special Note on Low Frequency Performance section Free Air Resonance Frequency SP8C 55 Hz SP12C 45 Hz SP15A 40 Hz Qes Electro Magnetic Q at fs SP8C 0 49 SP12C 0 75 SP15A 0 49 MS Mechancial Q at fs SP8C 5 2 SP12C 5 9 SP15A 5 0 Re Total O at fs eos Qes Oms SP8C 0 45 SP12C 0 67 SP15A 0 45 Vas Volume of Air Having Same Acoustic Compliance as Driver Suspension SP8C 1 0 ft3 SP12C 5 9 ft3 SP15A 9 9 ft3 nN Half Space Reference Efficiency SP8C 0 9 SP12C 1 9 SP15A 3 5 D Peak Displacement Volume of Diaphragm So Xmax SP8C 3 6 in3 SP12C 10 8 ft3 SP15A 25 in3 D Effective Diaphragm Area SP8C 30 in2 SP19C AR in2 Eleciro Voice a gultan company a or 126 oP 10A Component Speakers Xm ax Peak Linear Displacement of Diaphragm SP8C 0 12 in SP12C 0 13 in SP15A 0 20 in PE max Thermally Limited Maximum Input Power SP8C 25 watts SP12C 25 watts SP15A 50 watts Voice Coil Diameter SP8C 2 in SP12C 2 in SP15A 2 1 2 in Magnet Weight SP8C 22 oz SP12C 22 oz SP15A 78 oz Magnet Material Ceramic Dimensions Overall Diameter SP8C 8 3 8 in SP12C 12 3 16 in SP15A 1
11. 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 SP series of speakers may be installed either on the inside or outer 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 or more mounting holes and cut the mounting baffle opening in accordance with the dimensions given in the Specificat
12. peaker enclosure design The result is a combination of extended law distortion bass response high efficiency and modest cabinet size simply not available in other component speakers THE SP SERIES OF LOUDSPEAKERS All of the SP series af Electro Voice speakers have a rugged die cast frame for maximum mechanical stability much more so than the ordinary stamped frame speaker All three units utilize a ceramic magnet with adequate magnetic assembly for maximum flux in the gap and consequent high efficiency All three units incorporate a centrally mounted free edge cone for improved high frequency propagation SP8C The SP8C was designed for full range use or as a Woofer in a two or three way system For an eight inch speaker it will provide remarkable performance in the bass range even in a small enclosure only 1 2 cubic feet The SP8C is ideal for a small or starter high fidelity component speaker system It will produce quite adequate sound pressure levels in environments such as the average living room SP12C The SF 12C was also designed for full range use or service only as a woofer Due to the greater power handling capacity as well as the larger magnetic assembly as compared to the SP8C this unit will produce about 3 5 dB greater sound pressure than the smaller unit In addition it may be mounted in a larger box to provide response to half an octave lower frequency than the SP8C SP15A This is th
13. t 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 a BB1 High Frequency Building Block Kit The BB1 includes a T35 horn tweeter X36 Crossover Network Level Control wiring harness and mounting hardware In addition to extending the high frequency response beyond the limits of normal audibility the BB1 provides more precise definition of high frequency wave forms and improved high frequency dispersion in the listening area The improved dispersion makes it possible for the listener to move considerably off the central axis while experiencing very little change in sound quality The BB4A Mid Frequency Building Block Kit consisting of an 1823M Driver 8HD Diffraction Horn X8 Crossover Network and a Level Contro with wiring harness provides additional improvement in performance after installation of the BB1 The BB4A further reduces the frequency range which must be reproduced by the cone speaker reducing harmonic and inter modulation distortion in the total system The BB4A s diffraction horn improves dispersion in the listening area in addition to increasing efficiency The improved mid frequency performance provided by the BB4A 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
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