THE MOST COMMONLY ASKED QUESTIONS ABOUT BUILDING ENCLOSURES<\/p>\n
Many JBL users build their own loudspeaker enclosures. Their audio
\nskills range widely from novice to expert. From the thousands of
\nletters and calls we have received addressing the subject of
\nloudspeaker enclosure construction, we have determined the most common
\nquestions and present the following Questions and Answers. The
\nparticular questions listed attempt to answer as many questions as we
\nfeel are necessary to provide enough information to build an enclosure
\nwhich will allow your JBL loudspeaker to operate to its potential. The
\nquestions selected here concentrate on vented “bass reflex” enclosures,
\nsince low frequency horns are fairly complex, and many good tested
\ndesigns exist. Also, it is often more econonomical to buy a bass horn
\nenclosure than to build one. Vented box enclosures are by far the most
\npopular enclosure type. Vented boxes are finding increasing use by
\ntouring sound companies, displacing existing horn enclosure designs
\nbecause of the greater low frequency power output and extended low
\nfrequency capability they offer when used in arrays. In addition to
\ntheir simple design requirements, vented loudspeaker enclosures offer
\nflexibility of design in shape, weight and component complement, and
\nusually produce the best results obtainable from modern loudspeaker
\ndrivers at the lowest cost.<\/p>\n
[1]
\nQ: What makes a good vented enclosure?<\/p>\n
A: Basically, an enclosure serves to partition the front and rear of
\nthe driver’s cone, preventing the opposing air pressure changes
\nproduced by cone motion from cancelling, and allowing the radiation of
\nsound from the front of the driver only. In addition, vented
\nenclosures allow the compressibility of the air inside the enclosure to
\nwork as a more active part of the “system” consisting of driver and
\nenclosure. Beyond these two basic functions, a low frequency
\nloudspeaker enclosure should do absolutely nothing, that is, it should
\nadd no effects of its own–no vibration, no tonality, no motion–
\nnothing to interfere with or absorb acoustic energy produced by the
\ndriver.<\/p>\n
[2]
\nQ: Is it possible to get low, punchy bass from a small enclosure?<\/p>\n
A: Yes, if the driver in the enclosure is designed for low bass
\noperation in a small enclosure. Unfortunately, it’s usually a small
\ndriver that can work properly in a small enclosure, and that dictates
\nthat lower sound levels will result from the small amount of air such a
\nsmall driver can move. Larger boxes (with larger bass drivers) produce
\nmore bass, smaller boxes produce less bass. It’s a fact of life, like
\nthe fact that it takes a bass viol, a tuba, longer piano strings, or
\nvery large organ pipes to produce bass energy in the air. Low bass
\nrequires that more air move, and bigger boxes contain more air that can
\nbe put to work making low bass. <\/p>\n
[3]
\nQ: Can I get more bass from my enclosure by installing a bigger driver?<\/p>\n
A: A given enclosure will not automatically produce more bass when a
\nlarger driver is installed, in fact the opposite is often the result. <\/p>\n
[4]
\nQ: What about putting two drivers in the enclosure to increase bass?<\/p>\n
A: Placing two bass drivers in an enclosure designed for one will
\nusually produce less bass and more midrange output, and will upset the
\noperation of the driver-enclosure system because each driver will
\nbehave as though it is installed in an enclosure which has only half
\nthe internal volume of the original enclosure (with one driver).<\/p>\n
[5]
\nQ: What should I do to use two drivers (for more bass)?<\/p>\n
A: There are two alternative possibilities. When using two identical
\ndrivers, you can build an enclosure with twice the internal volume of
\nthe original enclosure that contained one driver, or you can duplicate
\nthe original enclosure and stack the two. As the latter alternative
\nsuggests, when building the double enclosure, it’s necessary to treat
\nthe enclosure as if it were two enclosures–you must double the porting
\nused on the single smaller enclosure–although it is not necessary to
\ndivide the volume of the double enclosure unless two different driver
\nmodels (e.g. E130 and E155) are used and their interaction would be
\nundesirable. A usable example of this might be a 227 liter (8 cubic
\nfoot) enclosure divided into two chambers so that the E130 occupies 57
\nliters (2 cubic feet) and the E155 occupies 170 liters (6 cubic feet).
\nIn this case, the ports tuning either chamber to the same desired
\nfrequency will be quite different.<\/p>\n
[6]
\nQ: What does port or enclosure “tuning” mean?<\/p>\n
A: In exactly the same way the resonant note from a bottle can be
\nraised and lowered by adding or pouring out liquid to change the
\nbottle’s air volume, enclosure tuning is affected by the ratio of air
\nvolumes in the port (the bottleneck) with its attendant flow
\nresistance, and the enclosure interior volume. Tuning of loudspeaker
\nenclosures is a result of manipulating the differences in effective air
\nmass between the enclosure interior and the air in the port. The
\nbottle-like nature of a vented enclosure is known as a “Helmholtz
\nresonator.” The ports or ducts in a vented enclosure work only over a
\nnarrow band of frequencies near the chosen tuned frequency, producing
\nthe same effect noted when blowing across a bottleneck–a single
\ndistinct pitch.<\/p>\n
[7]
\nQ: Is it always necessary to use a port for good bass?<\/p>\n
A: JBL uses vented enclosure designs because they are superior to
\nsealed enclosure designs in several important ways–as long as it is
\npossible to tightly control the loudspeaker driver parameters in
\nmanufacturing as JBL does. Vented designs produce lower distortion at
\nthe lowest operating frequencies, afford the driver protection against
\nmechanically destructive large cone excursion, and better enable the
\ndriver to absorb and utilize its full power rating from an amplifier
\nwhen operating at low frequencies. It is important to keep in mind
\nthat porting and tuning an enclosure provides air loading for the bass
\ndriver down to frequencies just below the Helmholtz frequency, but does
\nnot provide any loading for the driver at frequencies below that, such
\nas subsonic turntable rumble, record warp or microphone wind pickup.
\nIf you intend to operate a sound system at high power levels, we highly
\nrecommend an electronic high-pass filter to eliminate subsonic input to
\nthe power amplifier(s). This will substantially increase the available
\nuseful power from the amplifier which will then only operate in the
\naudible frequency range. Such a filter is the UREI model 501 Sub Sonic
\nProcessor, or the built-in sub-sonic switches of the JBL Electronic
\nFrequency Dividing Network model 5234A.<\/p>\n
[8]
\nQ: Where should I locate the port(s) with respect to the woofer?<\/p>\n
A: Bass reflex enclosures are usually designed to tune from about 100
\nhertz and down. The length of sound waves at these low frequencies is
\nover 11 feet, so port placement is not critical. Ports may be located
\nanywhere on the baffle with no change in bass performance; some designs
\neven locate ports on the back of the enclosure which works well as long
\nas the enclosure is not close to a wall (a couple of port diameters
\naway) and there is an unobstructed air path between the woofer and the
\nport. Overall, it’s safest to locate the port somewhere on the baffle
\nwith the woofer(s) far enough away from side walls to avoid interaction
\nbetween port and enclosure wall or the fiberglass insulation on the
\nwall.<\/p>\n
[9]
\nQ: What should the ducts be made of? Is round better than rectangular?<\/p>\n
A: Port ducts may be made of anything rigid, such as paper cardboard
\nwith about a 1.5 mm (1\/16″) or larger wall thickness. They can be any
\nshape, square or rectangular (such that port area remains constant) and
\nmade of wood or other suitable material. It is not necessary to use
\nPVC pipe for port tubing, particularly when most carpet stores throw
\naway large amounts of heavy carboard tubing of between 3 and 4-1\/2
\ninches inside diameter.<\/p>\n
[10]
\nQ: What is the relationship of duct length to port area?<\/p>\n
A: When port area is increased, independently of other factors,
\nenclosure tuning is raised. If duct length is increased, independently
\nof other factors, enclosure tuning is lowered. To keep the same tuning
\n(Helmholtz frequency) you will need to increase duct length as you
\nincrease port area. <\/p>\n
[11]
\nQ: How big should the port be?<\/p>\n
A: The bigger, the better. Any port causes some resistance to air
\nmovement, and so introduces unavoidable losses in output to the system
\nas a whole. The ratios of port area and length and enclosure volume
\ndetermine the Helmholtz frequency tuning. Mechanical reactance
\nelements, stiffness and air mass, control the effective air mass
\nratios. At very low operating levels, where air in the port does not
\nmove very fast, a small short port will behave the same as a large
\nlonger port as far as enclosure tuning is concerned. At high power
\nlevels however, the restricted air flow of the smaller port will
\nproduce output level losses, some de-tuning and at high enough levels a
\nsmall port will cause the enclosure to behave like a sealed enclosure
\nwith little or no contribution from the port. To minimize resistive
\nlosses, the largest practical port should be used. Computer listings
\nof port choices calculated to limit air velocity inside the port duct
\nwill list duct sizes which are normally impractical. A 380 mm (15 in)
\ndiameter port is not an unreasonable choice for a 380 mm bass driver,
\nhowever the necessary length would dictate that such a port might
\nitself have a volume of many cubic feet, sometimes equal to or larger
\nthan the original enclosure. A good rule of thumb would be to avoid
\nports whose circular area is smaller than at least 1\/3 the diameter of
\nthe driver such as a 127 mm (5 in) diameter port for a 380 mm (15 in)
\ndriver. This will usually provide sufficient port area so that the
\nport will not “whistle” when the system is operated at high power
\nlevels near the helmholtz frequency–a sure indication of severe system
\nlosses and potential power compression and low-frequency output
\nlimiting.<\/p>\n
[12]
\nQ: Can I use several smaller ports instead of one big one?<\/p>\n
A: Yes, however there is a phenomenon associated with air resistance
\nresulting from air drag on the internal surfaces of port ducts and
\nturbulence at the ends of the ports that requires a duct length
\ncorrection when several ports are used. For example, when using four
\n100 mm (4 in) tubes instead of one 200 mm (8 in) tube (which has the
\nsame port area but one-quarter the internal surface area), the length
\nneeded will be slightly less than that needed for the single 200 mm
\ntube, perhaps 5% to 10% less, depending on overall enclosure volume.
\nThese effects exhibited by port ducts is exaggerated by proximity of
\nthe duct to enclosure interior surfaces or any other type of boundary
\nthat may cause air turbulence near the end of the duct, therefore it’s
\nimportant to keep duct ends away from the rear of the cabinet or other
\nobstructions by an amount at least equivalent to or larger than the
\ndimension across the port. If you are using a rectangular port that
\nhas as one of its sides, an enclosure wall, you might have to use some
\ncorrection.<\/p>\n
[13]
\nQ: Is there a simple mathematical way of designing proper enclosures?<\/p>\n
A: Yes, a JBL scientist, D.B. Keele Jr., simplified the work of A.
\nNeville Thiele and Dr. Richard Small so that anyone with a pocket
\ncalculator and a ruler or straight edge can design the right enclosure
\nvolume and choose the right port or duct for a given loudspeaker
\ndriver. JBL offers, at no cost, a four-page “kit” containing detailed
\nstep by step instructions, written specifically for non-mathematicians,
\nshowing how to use published Thiele-Small driver parameters in
\nenclosure design. Examples are shown with their results graphically
\nrepresented. An enclosure design flow chart and enclosure venting
\nnomograph are included. <\/p>\n
[14]
\nQ: Should the enclosure’s baffle be removable?<\/p>\n
A: This is a question of mechanical strength and rigidity. All
\nenclosures, particularly those intended for rough portable use, should
\nbe constructed with all sides permanently fixed by glue and screws, and
\nsealed air-tight by virtue of well cut and glued joints. It is
\npreferable to mount loudspeakers from the front of the baffle board to
\neliminate the possiblity of reflections from the inside of the
\nloudspeaker mounting hole, thus it becomes unnecessary to provide for
\nremoving the baffle. Woofer openings are usually large enough to reach
\nthrough in order to work inside the box, for example, to install other
\ncomponents.<\/p>\n
[15]
\nQ: Is there a preferred shape for loudspeaker enclosures?<\/p>\n
A: There are a number of shapes that improve performance and some that
\ncause distinct degradation in performance. For single, full-range
\ndrivers (e.g. JBL’s LE8T) a sphere is the ideal shape for an enclosure
\nbecause the curved surfaces avoid the diffraction effects of cabinet
\nedges, which bend sound waves in a manner dependent on frequency. For
\nmulti-way loudspeaker systems, spheres are usually impractical because
\nof the large size needed and because of the precise orientation
\nrequired for optimal listening. Conventional enclosures work best
\nmounted flush into a wall where diffraction is controlled by virtue of
\nthe wall surface, and for free-standing enclosures, tilting, angled and
\ncurving surfaces may be employed to help reduce or control edge
\ndiffraction. The overall shape of the enclosure is relatively
\nunimportant except where the shape makes it difficult to build a rigid
\nenclosure. It is best to avoid enclosure dimensions that are multiples
\nof each other, such as 1 X 2 X 4 ratios, and strive to use dimensions
\nthat have somewhat unrelated ratios such as 1 X 1.23 X 1.41.<\/p>\n
[16]
\nQ: What is the best material to use for building enclosures?<\/p>\n
A: For home and permanent installation use, high density particle wood
\nis the most cost-effective material for general enclosure construction.
\nThe best wood to use for portable enclosure construction is 14 to 20
\nply per inch Finland birch type. Birch plywood is very expensive
\nhowever, and a carefully braced enclosure made of high grade void-free
\nfir plywood can do the job just as well in most cases. The thicker you
\ncan make the cabinet walls, the better the results will be because of
\nreduced wall vibration and resonance, but the tradeoff is cost and
\nweight. Enclosure walls should be cut so that edges form an air-tight
\nseal when glued together. Cleats and caulking can also be used if
\nneeded to insure a good fit and tight air seal.<\/p>\n
[17]
\nQ: Is bracing necessary? How much should be used?<\/p>\n
A: Bracing should be added to the enclosure interior to minimize
\nenclosure wall vibration. Enclosure walls simply cannot be stiff
\nenough since wall vibration indicates that energy is being wasted to
\nmove enclosure panels rather than moving air. 25 X 76 mm (1 X 3 in)
\npine bracing fixed on edge with glue and screws to the enclosure walls
\nwill help provide the minimum necessary stiffening without affecting
\nthe internal volume significantly. If you are building large subwoofer
\nenclosures, bracing with two-by-fours works better, though you should
\ntake the bracing volume into account since a 3 m (10-foot) length takes
\nup 12.9 liters (0.36 cubic foot) of enclosure volume. <\/p>\n
[18]
\nQ: How should I mount drivers on the baffle?<\/p>\n
A: Mount drivers on the front of the baffle whenever possible to avoid
\nthe reflections from inside the mounting hole. Heavy drivers should
\nnormally be front-mounted using Tee-nuts and machine screws or JBL’s
\nMA15 clamps. If Tee-nuts are used, apply a bit of Bostic or Pliobond
\ntype rubber glue to the inside of the nut flange to help avoid losing
\nthe Tee-nut inside the enclosure when installing the driver. Baffle
\nboard construction is much easier if all baffle parts are assembled
\nprior to final box assembly. <\/p>\n
[19]
\nQ: Do I need fiberglass inside the enclosure?<\/p>\n
A: JBL uses a 25 mm (1 in) padding of 1\/2-pound density fiberglass
\nstapled to the enclosure interior on all surfaces except the baffle.
\nYou should use 100 mm (4 in) thick dacron or 25 mm (1 in) fiberglass on
\nat least three of the surfaces of parallel interior walls. Keep sound
\nabsorbing materials away from the port(s) as the air velocity inside
\nthe port can be sufficient to tear off bits of the material and squirt
\nthem out of the enclosure. It is not necessary to cover the inside of
\nthe baffle, but doing so will rarely degrade system performance. The
\nenclosure exterior may be covered with your choice of any suitable
\nfinish or decoration; this will not affect bass performance and in some
\ncases (as with Formica) may help stiffen the enclosure walls.<\/p>\n
[20]
\nQ: Does Fiberglass significantly affect enclosure tuning?<\/p>\n
A: No, not unless the enclosure is stuffed full of fiberglass, in which
\ncase the apparent volume of the enclosure increases by 12% to 20% as
\nseen from the point of view of the bass driver. Stuffing the enclosure
\nfull with fiberglass is not recommended because it introduces system
\nlosses, is expensive and interferes with port operation. The exception
\nto this would be a sealed “air suspension” type system enclosure where
\nmore virtual volume is needed and actual volume is not available,
\nand\/or where box dimensions which are multiples of each other can’t be
\navoided and the fiberglass stuffing will help absorb the internal sound
\nreflections.<\/p>\n
[21]
\nQ: What is needed to mount a midrange on the baffle with the woofer?<\/p>\n
A: For cone-type midrange drivers, a sealed sub-chamber should be used
\nto prevent interaction with the enclosure’s bass driver. JBL drivers
\nsuitable for sealed-chamber midrange use require only 10 to 40 liters
\n(.3 to 1.0 cubic foot) of chamber volume to operate at typical midrange
\nfrequencies, above 200 hertz. Subchambers should be constructed
\nsolidly and liberally lined with fiberglass. As in the case of
\nenclosure shapes, avoiding multiples of dimensions, subchambers should
\nbe built so as to avoid square and cube shapes in favor of non-related
\nnumerical ratios.<\/p>\n
[22]
\nQ: Is there any special procedure for mounting a horn in an enclosure?<\/p>\n
A: Use of a horn\/compression driver does not require any subchamber
\nsince these devices form their own air-tight seal. JBL horns such as
\nthe 2344, 2370, MI-291 and 2380 horn family also seal their own cutout
\nopening in the enclosure when properly mounted on the baffle. Better
\ncompression drivers are quite heavy, so a brace should be provided to
\ncradle the driver to prevent driver movement during shipping. In
\ncombination with the length of a horn as a lever, driver mass can cause
\nthe assembly to tear off the baffle or break the horn if the enclosure
\nis handled roughly or dropped. Driver mass can also tear off the horn
\nthroat if cabinets are dropped on their backs.<\/p>\n
CONVERSION CONSTANTS and USEFUL DATA
\n ____________________________________<\/p>\n
LITERS FEET^3 INCHES^3 METERS^3 MILLIMETERS INCHES METERS
\n___________________________________ _____________________________
\n 1.00 = .03531 = 61.0 = .001 1.00 = .039 = .001
\n 28.32 = 1.00 = 1,728 = .02832 25.40 = 1.000 = .0254
\n1000.00 = 35.31 = 61,016 = 1.00 1000.00 = 39.370 = 1.000<\/p>\n
TO FIND SOUND WAVE LENGTH: divide velocity of sound by frequency (Hz)
\n (SOUND VELOCITY = 344 m\/s, 1130 ft\/s or 13,560 in\/s)<\/p>\n
AREA OF CIRCLE = 3.14 x (radius squared) Note: radius = 1\/2 diameter<\/p>\n
TO FIND THE DIAMETER OF A CIRCLE WITH EQUIVALENT AREA:
\n 2 x square-root of (area divided by 3.14)
\n example: area of 9″ tube = area of 8″ square duct calculated:
\n (area) 64\/3.14=20.37, square root = 4.51 x 2 = 9.03 (diameter)<\/p>\n
VOLUME OF CYLINDRICAL DUCT = circular area x length<\/p>\n
VOLUME DISPLACED BY JBL LOUDSPEAKERS: 8″ = .05 cu ft, 10″ = .1 cu ft,
\n12″ = .15 cu ft, 15″ = .2 cu ft, 18″ = .3 cu ft.<\/p>\n
JBL LOUDSPEAKER MOUNTING HOLE AND BOLT CIRCLE DIMENSIONS:
\nmounting holes:
\n8″ = 7-1\/16″ 10″ = 9″ 12″ = 11-1\/16″ 15″ = 13-31\/32″
\n18″ = 16-13\/16″<\/p>\n
bolt circles:
\n8″ = 7-5\/8″ 10″ = 9-3\/4″ 12″ = 11-9\/16″ 15″ = 14-9\/16″
\n18″ = 17-3\/8″<\/p>\n
BIBLIOGRAPHY of RECOMMENDED AUDIO REFERENCES
\n ____________________________________________<\/p>\n
FOR AUDIO NOVICES:<\/p>\n
BOOKS:<\/p>\n
David B. Weems, “Building Speaker Enclosures,” Radio Shack
\npublication, stock# 62-2309<\/p>\n
“The CAMEO Dictionary of Creative Audio Terms,” Creative Audio & Music
\nElectronics Organization, 10 Delmar Avenue, Framingham, MA 01701<\/p>\n
F. Alton Everest, “The Complete Handbook of Public Address Sound
\nSystems,” Tab Books #966, Tab Books, Blue Ridge Summit, PA 17214<\/p>\n
David B. Weems, “Designing, Building & Testing Your Own Speaker
\nSystem,” Tab Books #1364 (this is the same as the Weems book above)<\/p>\n
Abraham B. Cohen, “Hi-Fi Loudspeakers and Enclosures,” Hayden Book Co.,
\n0721<\/p>\n
Alex Badmaieff and Don Davis, “How to Build Speaker Enclosures,” Howard
\nW. Sams & Co., Inc., 4300 West 62nd Street, Indianapolis, IN 46268<\/p>\n
Bob Heil, “Practical Guide for Concert Sound,” Sound Publishing Co.,
\n156 East 37th Street, New York, NY 10016<\/p>\n
PAPERS:<\/p>\n
Drew Daniels, “The Most Commonly Asked Questions About Building
\nEnclosures,” JBL Professional, 8500 Balboa Blvd., Northridge CA, 91329 <\/p>\n
Drew Daniels, “Using the enclosure design flow chart,” JBL
\nProfessional, 8500 Balboa Blvd., Northridge, CA 91329 <\/p>\n
FOR EXPERIENCED AUDIO PRACTITIONERS AND HOBBYISTS:<\/p>\n
BOOKS:<\/p>\n
Jens Trampe Broch, “Acoustic Noise Measurement,” Bruel & Kjaer
\nInstruments, Inc., 185 Forest Street, Marlborough, MA 01752 (617) 481-
\n7000<\/p>\n
Howard M. Tremaine, “The Audio Cyclopedia,” 2nd Edition 1969, Howard W.
\nSams & Co., Inc., 4300 West 62nd Street, Indianapolis, IN 46268<\/p>\n
Arnold P. Peterson and Ervin E. Gross, Jr., “Handbook of Noise
\nMeasurement,” General Radio, 300 Baker Avenue, Concord, MA 01742<\/p>\n
Martin Colloms, “High Performance Loudspeakers,” A Halstead Press Book,
\n1978 John Wiley and Sons, New York and Toronto.<\/p>\n
Harry F. Olson, “Modern Sound Reproduction,” 1972, Van Nostrand
\nReinhold Co., New York.<\/p>\n
Harry F. Olson, “Music Physics and Engineering,” Dover Publications,
\n180 Varick Street, New York, NY 10014<\/p>\n
Don and Carolyn Davis, “Sound System Engineering,” Howard W. Sams &
\nCo., Inc., 4300 West 62nd Street, Indianapolis, IN 46268<\/p>\n
F. Alton Everest, “Successful Sound System Operation,” Tab Books #2606,
\nTab Books, Blue Ridge Summit, PA 17214<\/p>\n
PAPERS:<\/p>\n
Drew Daniels, “Notes on 70-volt and distributed system presentation,”
\nfor the National Sound Contractors Association Convention, September
\n10, 1985, JBL Professional, 8500 Balboa Blvd., Northridge, CA 91329<\/p>\n
Drew Daniels, “Thiele-Small Nuts and Bolts with Painless Math,”
\npresented at the 70th Convention of the Audio Engineering Society,
\nNovember 1981 AES preprint number 1802(C8).<\/p>\n
FOR ENGINEERS:<\/p>\n
BOOKS:<\/p>\n
Harry F. Olson, “Acoustical Engineering,” D. Van Nostrand Co., Inc.,
\n250 4th Street, New York 3, NY 1957 (out of print)<\/p>\n
Leo L. Beranek, “Acoustics,” Mc Graw-Hill Book Co., New York 1954.<\/p>\n
Harry F. Olson, “Elements of Acoustical Engineering,” D. Van Nostrand
\nCo., Inc., 250 4th Street, New York 3, NY (1st ed., 1940, 2nd ed., 1947
\nboth out of print)<\/p>\n
Lawrence E. Kinsler and Austin R. Frey, “Fundamentals of Acoustics,”
\nJohn Wiley and Sons, New York and Toronto.<\/p>\n
N.W. McLachlan, “Loudspeakers: Theory Performance, Testing and Design,
\nOxford Engineering Science Series, Oxford at The Clarendon Press 1934,
\nCorrected Edition, Dover Publications 1960.<\/p>\n
PAPERS:<\/p>\n
Don B. Keele, Jr., “AWASP: An Acoustic Wave Analysis and Simulation
\nProgram,” presented at the 60th AES Convention in Los Angeles, May
\n1978.<\/p>\n
Fancher M. Murray, “An Application of Bob Smith’s Phasing Plug,”
\npresented at the 61st AES Convention in New York, November 1978.<\/p>\n
Don B. Keele Jr., “Automated Loudspeaker Polar Response Measurements
\nUnder Microcomputer Control,” presented at the 65th AES Convention in
\nLondon, February 1980.<\/p>\n
R.H. Small, “Direct-Radiator Loudspeaker System Analysis,” Journal of
\nthe Audio Engineering Society (JAES), Vol. 20, p. 383, June 1972.<\/p>\n
Mark R. Gander, “Ground Plane Acoustic Measurement of Loudspeaker
\nSystems,” presented at the 66th AES Convention in Los Angeles, May
\n1980.<\/p>\n
“Loudspeakers,” An anthology of articles on loudspeakers from the pages
\nof the Journal of the Audio Engineering Society, Vol. 1 through Vol. 25
\n(1953-1977). Available from the Audio Engineering Society, 60 East
\n42nd Street, New York, NY 10165 Telephone (212) 661-8528<\/p>\n
A.N. Thiele, “Loudspeakers in Vented Boxes,” Proceedings of the IREE
\nAustralia, Vol. 22, p. 487 August 1961; republished in the JAES, vol.
\n19, p. 382 May 1971 and p. 471 June 1971.<\/p>\n
Fancher M. Murray, “The Motional Impedance of an Electro-Dynamic
\nLoudspeaker,” presented at the 98th Meeting of the Acoustical Society
\nof America, November 19, 1979.<\/p>\n
Mark R. Gander, “Moving-Coil Loudspeaker Topology As An Indicator of
\nLinear Excursion Capability,” presented at the 64th AES Convention in
\nNew York, November 1979.<\/p>\n
Garry Margolis and John C. Young, “A Personal Calculator Program for
\nLow Frequency Horn Design Using Thiele-Small Driver Parameters,”
\npresented at the 62nd AES Convention in Brussels, March 1979.<\/p>\n
Garry Margolis and Richard H. Small, “Personal Calculator Programs for
\nApproximate Vented-Box and Closed-Box Loudspeaker System Design,”
\npresented at the 66th AES Convention in Los Angeles, May 1980.<\/p>\n
Fancher M. Murray and Howard M. Durbin, “Three Dimensional Diaphragm
\nSuspensions for Compression Drivers,” presented at the 63rd AES
\nConvention in Los Angeles, March 1979.<\/p>\n
R.H. Small, “Vented-Box Loudspeaker Systems,” Journal of the Audio
\nEngineering Society, Vol. 21, p. 363 June 1973, p. 438 July\/August
\n1973, p. 549 September 1973, and p. 635 October 1973.<\/p>\n
JBL TECHNICAL NOTES:<\/p>\n
The following are available at no cost from JBL Professional:<\/p>\n
Vol. 1, No. 1 – “Performance Parameters of JBL Low-Frequency Systems”<\/p>\n
Vol. 1, No. 2 – “70-Volt Distribution Systems Using JBL Industrial
\n Series Loudspeakers”<\/p>\n
Vol. 1, No. 3 – “Choosing JBL Low-Frequency Transducers”<\/p>\n
Vol. 1, No. 4 – “Constant Directivity Horns”<\/p>\n
Vol. 1, No. 5 – “Field Network Modifications for Flat Power Response
\n Applications”<\/p>\n
Vol. 1, No. 6 – “JBL High-frequency Directional Data in Isobar Form”<\/p>\n
Vol. 1, No. 7 – “In-Line Stacked Arrays of Flat-front Bi-Radial Horns”<\/p>\n
Vol. 1, No. 8 – “Characteristics of High-Frequency Compression Drivers”<\/p>\n
Vol. 1, No. 9 – “Distortion and Power Compression in Low-frequency
\n Transducers”<\/p>\n
Vol. 1, No. 10- “Use Of The 4612OK, 4671OK, And 4660 Systems In Fixed
\n Installation Sound Reinforcement”<\/p>\n
Vol. 2, No. 2 – “JBL\/UREI Power Amplifier Design Philosophy”<\/p>\n
Instruction Manual – “Motion Picture Loudspeaker Systems: A Guide to
\n Proper Selection And Installation”<\/p>\n
“JBL Sound System Design Reference Manual” ($15)<\/p>\n
