L O U D S P E A K E R

H A N D B O O K

A N D

L E X I C O N

byWinslow Burhoe

1978

REVISED 1994, 1995, 1997

ART OR SCIENCE?

This handbook has been prepared to take justa touch of the mystery out of the subject ofloudspeaker design and performance, with aneye out to the characteristics that make aloudspeaker sound good (or bad).

Since this is a personal statement of onedesigner, who necessarily is in business forprofits as well as enjoyment, the handbookmakes no claim to being either objective orcomprehensive.

For the reader's convenience, the handbookhas three related, but different, sections:

1: A general introduction which tersely tiestogether some fundamental concepts and setsforth the problem;

2: An expansion of some of the key conceptsof speaker design and speaker construction;and

3: A lexicon of commonly encountered speakerterms and vocabulary.

Throughout this document, any term defined inthe Lexicon is in bold italic type.

Hoping you'll have a bit of fun with thishandbook, even if it may seem to raise morequestions than it answers. . .

D e d i c a t e d t o E d g a r V i l l c h u r ,

w h o i n v e n t e d n o t o n l y m o s t o f

t h e k e y i n n o v a t i o n s o f m o d e r n

h i g h f i d e l i t y s p e a k e r s , b u t

a l s o t h e t e c h n i q u e s o f

p o p u l a r i z i n g t h e s c i e n t i f i c

a s p e c t o f h i g h f i d e l i t y .

❧

PART ONE

SPEAKER DESIGN

At first glimpse, speaker design tends to lookrelatively simple and uncomplicated: thedesigner seems to have little more to do thanselect the right combination of drivers andelectrical components, mount them in a cabinetwhich will enhance the sound they createtogether, and then send the results down to theproduction department.

However, technically speaking, the task athand is converting electrical waveforms from anamplifier into acoustical, three-dimensionalwaves. The challenge is to accomplish this withthe least possible distortion. Ideally thereshould be none. Usually there's quite a lot. Andthat's just the first problem.

The designer is challenged by the materials hemust work with. The woofer, from which room-filling bass must come, in reality is generally afragile paper cone with unpredictable minormovements, pushed by a wound wire moving inthe gap of a MAGNET whose magnetic fieldshould be uniform but seldom can be. Thetweeter, on which the highest audiblefrequencies depend, is generally a tiny objectcalled upon to perform the vir tually impossibletask of emitting sound identical to that whichcomes from large musical instruments with vastradiating surfaces. And, dividing sounds

between woofer and tweeter is the job of anelectronic or mechanical CROSSOVER whichcannot, by definition, do the job perfectly.

Then there's the problem of inefficiency.Almost all loudspeakers are notoriouslyinefficient, producing far more heat than music.Improving loudspeaker efficiency is certainlypart of the goal. Large drivers, large magnets,and large enclosures help. However,improvements in efficiency are seldom free.They are usually paid for by narrowing offrequency response (bandwidth). (Bandwidth isenhanced by small drivers and long voice coils;both are enemies of efficiency.) Then there'sthe problem of size versus performance. Largeboxes give better bass efficiency and poweroutput, but add to the cost of the speaker.Smaller boxes provide better dispersion andfrequency response, but without the realism.Designers must therefore constantlycompromise between cost and size incommercial designs.

Not only must the designer compromisebetween size and cost, bandwidth andefficiency. Each time he designs a new speaker,there are scores of factors to be juggled.Theory and math can only be a looseframework. Pure theory has its limits, first,because the rooms in which speakers willeventually be used can only be guessed at, yetwill influence frequency response anddispersion, and also because psycho-acousticfactors (how and what the ear hears, how itselects and interprets) have a strong influenceon the final sound or "response" of the speaker.

In its painstaking advance towards less andless distortion, successful speaker design

requires of its practitioners a thorough grasp ofhow sound behaves and how the ear hears, butthat's only one prerequisite. A secondqualification for success may be and attic orbasement or perhaps a back room full ofspeakers of all sizes and shapes, all uniqueprototypes, each built with care and the hopethat this particular combination of designconsiderations may be the designer's finestspeaker yet. Some designers seem to build onefine speaker after another, yet often the realsecrets of their successful and famous designsderive from many unfamous and even unnamedprototypes representing years of effort but nowpractically forgotten.

Hopefully what the designer learned from themis not, so that when you choose a speaker by agood designer, you're getting more than anenclosure and electronics. You're also getting aunique blend of design factors and thedesigner's experience: a share of the importantthings learned among the prototypes in theback room.

P A R T T W O

T h e B a s i c s

FREQUENCYRESPONSE

The most important thing about any speaker isits frequency response. It is here that designersspend most of their effort, for the wider thefrequency response (the higher and lower themusical tones it can reproduce), the more youhear.

Various frequencies of vibration generatevarious pitches. For example, middle C on apiano creates a vibration or sound wave or 256cycles per second.

A good example of high frequency sound isthe almost inaudible (for many people) hiss orwhistle given off by the flyback transformer of atelevision set, which vibrates at 15,750 cyclesper second in order to generate the 15,570lines per second displayed on the TV screen. Ifyou can't hear this on your own set, try listeningin a TV showroom. This is a good test to try outthe top end of your hearing, for 15,750 cyclesper second is near or past the top limit formost people's hearing.

WOOFERS ANDTWEETERS

The search for speakers with the widestpossible frequency response led to thespecialization of drivers as woofers andtweeters. Bass or low frequency responsedepends on a speaker moving large quantitiesof air, and therefore generally requires aspeaker cone of large size and area (and also along voice coil).

A woofer becomes more efficient as frequencyrises. This is because higher frequencies haveshorter wave-lengths, closer to the size of thewoofer cone itself, resulting in more effectivecoupling of the woofer cone and the air.

Generating high frequency sounds is a totallydifferent problem, requiring very little mass andsize . Usually, the smaller the tweeter, thehigher its frequency response. A large tweeterwill play more loudly, but with less range andrelatively poorer accuracy at the higherfrequencies.

VOICE COIL

One of the moving parts and hence movingmass of a dynamic speaker or driver. Thedesign and shape of a voice coil is a criticalaspect of speaker design. The coil must notonly perform perfectly as an electricalcomponent, accepting and converting currentfrom the amplifier into mechanical energy; butthrough its length and its mass it alsoinfluences the physical behavior of the speaker.

Low frequencies require a relatively heavylong voice coil.

Initial design, winding accuracy, quality ofmaterial and workmanship and precise qualitycontrol are all factors in voice coil production.

DRIVER

A speaker. Since the term "speaker" refersboth to an individual component and to asystem of several speakers, the word "driver",which refers only to a single element, is often

used to avoid ambiguity. Examples of driversinclude a woofer, a mid-range, a tweeter, ahorn, an electrostatic unit.

CROSSOVER

In speaker design, a mechanical or electricaldevice to split a speaker's input signal intohigh-frequency and low-frequency components.In a two-way speaker system, the crossover isessentially two filters: an inductor which allowsonly low frequencies to reach the woofer, and acapacitor which allows only high frequencies toreach the tweeter.

More complex crossovers have combinationsof coils, capacitors, resistors and othercomponents. The use of more crossovercomponents allows the designer either to makethe crossover slopes steeper (so that there isless overlapping of the sound from the twodrivers) or to shape the frequency response asdesired to improve the frequency response ofthe drivers.

CROSSOVER POINT

In a two-way system, the low end of thetweeter's frequency response and the high endof the woofer's frequency response. Thetweeter's low end therefore should be justabout the same as the high end of the woofer.One advantage to a speaker company whichmanufactures its own drivers, rather thanbuying them ready made, is that the designercan precisely control frequency responsethrough precise variations in such factors ascoil mass and cone shape.

EFFICIENCY

Speaker efficiency is the ratio of sound energyto power input. The range of efficiency inspeakers runs from about one third or a percentto about ten percent. Very few speakers havebetter than ten percent efficiency, and most runabout one percent.

The loss or wasted energy is mostly heat. Inthis sense, a speaker is essentially a heaterwhich produces music as a by-product, which iswhy speakers occasionally burn out or blow up.The trend towards very high-powered amplifiersdramatically increases the possibility of suchmishaps.

A general rule of thumb is that more efficiencyin a loudspeaker actually means a narrowerfrequency response. Consider the speaker asanalogous to a filter and the reasons becomeclear. Any filter allows only a certain bandwidthto pass through. A narrow band has higheramplitude. If the filter is designed to allow awide-range signal to pass, there willnecessarily be less amplitude. In this sense aspeaker can be perfectly represented bysymbols which are the same as electronicsymbols. (Also see THIELE.)

DISPERSION

Uniform dispersion of sound exists when youcan sit anywhere around a speaker and hearthe same sound. Dispersion is an importantchallenge in speaker design. Ideally a speakershould produce a spherical sound wave at allfrequencies. In reality both woofers andtweeters begin to beam sound as frequency

gets higher.

The smaller a speaker, the higher thefrequency up to which it gives uniformdispersion (spherical waveform). For example, aone-inch tweeter is able to give sphericaldispersion up to about 12,000 or 13,000 Hz. Ahalf-inch tweeter is good to nearly 20,000 Hz. Awoofer usually begins to beam at about therange of the female voice (800-900·Hz).

Most of the sound that you hear is reflected offthe wall. If there's a frequency range wheredispersion is poor, then you don't hear thereflected sound wave and the overall powerresponse is off in that frequency range.

Because of the difficulty in obtaing drivers thatprovide ideal dispersion, some designers try totake advantage of the limited dispersion toenhance some other aspect of the performance,such as, stereo imaging or absence ofmicrophone feedback.

DISTORTION

When light goes through a lens, a certainamount of fuzziness is always introduced to theoriginal image. When an electrical sound-waveenters a loudspeaker, a certain amount offuzziness or distortion is always introducedwhile converting the electrical energy intosound energy.

This distortion comes about because themotion of the speaker is never exactly the sameas the input. When the voice coil moves, theforce behind the motion may not be uniformbecause the coil moves in relation to thestationary magnetic field and because

opposition to the coil motion is not uniformbecause of the varying resistance and stiffnessof the suspension

Ways of decreasing distortion are:

1. Longer voice coils

2. Uniform suspension elements which allow alot of play (excursion).

3. Oversized elements. (Large drivers, longvoice coils, large suspension elements.)

Distortion will occur: if the force from themotor driving the cone is non-linear, if parts ofa cone move independently, if air is escaping inand out of small vents in the enclosure, if thereis ringing from parts which should not vibrate,or if components emit their own resonantfrequencies when excited by other frequencies.

Distortion also occurs when dispersion of thesound wave is uneven, or if the phase responseis not uniform as a function of frequency.

If the magnetic field of the magnet is unequalon two sides, this will also cause distortion.

Since the room in which the speaker functionscan also introduce distortion into the speaker'soutput, placement of speakers in the room,particularly bass reflex designs, can be crucialin improving sound.

Forms of distortion:

HARMONIC: easiest to measure

LIMITED BANDWIDTH: most important

INTER MODULATION OR IM: most unpleasant

TRANSIENT INTERMODULATION OR TIM

UNEVEN DISPERSION: difficult to hear

UNEVEN PHASE RESPONSE: difficult to hear

DOPPLER: difficult to measure

SPURIOUS BUZZES, RESONANCES ORVIBRATIONS: from poor construction

ENVIRONMENTAL EFFECTS: room acoustics.

QQ is the formula for what happens electrically

and physically at resonant frequency. Q isrelated to how slowly a natural vibration diesdown. Q is a neat term that combines manyelements of speaker design, so it's animportant term to speaker designers.

Q is important to the woofer because in aspeaker system where the Q is too high, you'llget a whomp in the bass. If a speaker system'sQ is too low, then the bass output is relativelyweak, because frequency response is highlydamped in that region.

The best Q for a speaker to have is one thatgives flat response down to the resonantfrequency.

If you do nothing to a speaker but make thecabinet smaller, you increase stiffness andtherefore Q goes up. But Q is not a word forstiffness alone. It's a ration involving mass,stiffness, and resistance (or damping).Designers often juggle these three factors.Good bass is not enough. Good bass withuniform frequency response and sphericalwave-form is the goal. Obtaining that goalwithout too much sacrifice in efficiency is thechallenge.

EFFICIENCY ANDMAGNETIC FORCE

In a dynamic speaker, the voice coil and themagnet structure interact to force the speakerto move. Send an electric current through a coilin or near a magnet and a force is produced.The force results in an alternating movement ormotion which is converted to variations in airpressure by a cone. The pressure is radiated asa sound wave.

The stronger the magnetic field, the higher theforce, the higher the efficiency. Bigger magnetsoften lead to stronger magnetic fields, but notalways, because the strength is related, notonly to magnet size, but also to the size andshape of the gap that the voice coil moves in.Toget a more efficient speaker of the same size,you can use a stronger magnetic field.However, this gives you lower Q. You'll get moreoutput at the middle frequencies, but less at thehigh and low ends. This can give relatively lessbass even though you now have higherefficiency. Therefore, if you increase magneticfield, you have to go back and redesign thetuned port of the cabinet to get back to correctresponse.

CABINET DESIGN

Speaker cabinets have two jobs: they serve asa baffle for mounting of drivers, and serve tomodify, re-phase, improve, radiate, suppress, orredirect the back wave from the woofer andkeep it separate from the front wave.

As a baffle, the speaker cabinet is usually less

than ideal. Since the cabinet sticks out from thewall, and has sharp edges and corners,acoustic problems develop as sound wavespass over the edges of the cabinet. Onerelatively effective response to this problem is acabinet whose shape flow smoothly "into thewall" because of beveled or curved panels.

Cabinets should ideally be designed to avoid:

1. Motion of the walls of the cabinet.

2. Transmission of sound through the cabinetwalls.

Therefore, the ideal cabinet is heavy and rigid.These considerations are particularly importantin acoustic suspension designs, where the backwave the woofer must be completely"contained".

Today, almost all speaker cabinets are madefrom particle board. This material is particularlygood because it has no spaces into which aircan flow (unlike plywood), which often does).However, particle board is relative flexible,therefore failing to avoid condition 1 above, andoften requires astute bracing and very solidconstruction techniques (screws, glue,reinforcement, etc.) in order to approachrequired rigidity.

There are many types of speaker designswhere the cabinet design is integral to thespeaker design. Some that come to mind are:TRANSMISSION LINEIsobaricOmni-directional (Bi-polar)BAND-PASSHornsLimited dispersion

P A R T T H R E E

T h e L e x i c o n

A

ABSOLUTE PHASEIn the recording and reproduction chain, there

are many opportunities to reverse polarity,especially when hooking up speaker wirebetwen the amplifier and the speaker. For mostpeople there is no difference in the sound whenthe polarity is reversed. However, someaudiophiles argue that there would be adifference in the sound if the polarity were to bechanged for something like an explosion and ifthe reproduction could reproduce all the lowfrequencies in the sound. The sound of anexplosion would have positive polarity, you see.

(See POLARITY, PHASE.)

ACOUSTIC FEEDBACKIf a portion of the sound output from

loudspeakers can somehow excite the turntableor stylus of the system, a new, unwanted signalis created, which is in turn amplified by theelectronics and reproduced by the speakers. Ifthis signal is in phase with the original signal ata particular frequency (usually bass) atremendous resonance (oscillation, a form ofpositive feedback) can occur in the room. Evensmall amounts of acoustic feedback can causea considerable amount of distortion.

The careful positioning of speakers andturntable is the usual remedy to the problem.Placing the turntable anywhere near thespeakers is usually a mistake.

An effect similar to acoustic feedback occurswhen vibrations from walking in the room are

transmitted up to the turntable from the floor.Generally if a turntable is positioned so that itis free from this kind of vibration, it will also besafe from acoustic feedback.

CD players and amplifiers are a lot lesssusceptible to acoustic feedback, but it doesexist, and precautions sometimes help.

Another example of acoustic feedback (thistime at high frequencies) is the squeal thatoccurs in microphone hookups where outputfrom the speaker re-enters the system throughthe microphone.

No matter what the frequency, even if the gainof the amplifier is not high enough to causeoscillation, distortion in the form of a boost inresponse at certain frequencies will result fromacoustic feedback. This can cause even thebest speakers to sound "boomy". Ironically, thegeneral recent improvement in low frequencyresponse of quality systems has simplyintensified the problem, so that acousticfeedback has become a major problem inquality sound installations.

"ACOUSTIC RESEARCH", or"AR, Inc."This is the company founded by Ed Villchur

(see Dedication) and Henry Kloss (later of KLHand Advent). Here began the invention ofacoustic suspension and many other principlesand techniques of modern speaker design.

ACOUSTIC SUSPENSIONMounting a speaker in a hermetic or air-tight

enclosure traps a fixed quantity of air behind it.The springiness of this air can effectivelyreplace the suspension spring used in speakersto return the speaker cone to its "normal"position, hence the term "acoustic suspension"(either "air suspension" or "pneumaticsuspension" would be more accurate). TheADVENT, the AR 3, and the EPI 100 are (old)examples of acoustic suspension speakers.

Acoustic suspension speakers are traditionallymuch less efficient than bass reflex speakersand therefore need more powerful amplifiers.

The major advantage of the design issimplicity and therefore simpler manufacturingand lower initial cost. However, any savingsmay be eaten up by the need for a morepowerful amplifier. This is the hidden butunavoidable cost of inefficient speakers.

ANALOGA method of reproducing sound waves that is

analogous to how they are in air. Analog soundwaves can be converted into digital informationbits in an A to D converter.

(See DIGITAL)

B

BAFFLEA baffle is a mounting for a speaker which

assists sound radiation. A baffle is importantbecause many sound wavelengths are longerthan the speaker. The ideal baffle is flat andextends forever, creating a hemispherical soundwave.

The baffle is usually part of the cabinet.Sometimes special baffles are built for testingpurposes.

When a small speaker is placed near the wall,the wall becomes part of its baffle.

The term infinite baffle is another way ofdescribing the ideal baffle mentioned above.Actually, infinite baffle is often used to describeany situation where the back wave from thespeaker is completely isolated from the front,as when a speaker is mounted in a hole in awall.

BAND-PASSA variation of the bass reflex design. A

speaker enclosure is divided into two chamberswith the woofer mounted between them. One ofthe chambers is then vented with a tuned port.The tuned vent acts like a filter which limits thefrequency responce to a desired bandwidth,thus the term band-pass. This type of design isused primarily for sub-woofers and bass unitsof satellite systems.

(Also see FILTER)

BANDWIDTHThe range of frequencies in which amplitude

remains constant. Bandwidth is generally thesubject of much controversy and confusion,since there is no standard method ofmeasurement. Should speaker bandwidth bemeasured in a living room or in an anechoicchamber? How far should the microphone befrom the speaker: Should the mike recordreflected sound? Etc.

bandwidth is another way of saying frequencyresponse.

(See SPEAKER SPECIFICATIONS)

BASS REFLEXA speaker in an infinite baffle or a sealed

enclosure uses only its front wave to producesound. In a bass reflex or tuned port design,part of the back wave of the speaker is used toreinforce the front wave usually in the bass.

The back wave excites a resonant systemwhich then radiates sound. This resonantsystem has two components: mass (actually airin this case), and the stiffness of the airsuspension in the box.

The resonant system using the backwave is farmore efficient than the primary system. Verylittle power excites great sound from bass reflexsystems in the frequency range to which theport is tuned (generally below 100 Hz).

The increased output obtained in a bass reflexdesign can be used by the designer either toimprove efficiency or to extend low frequencyresponse.

An advantage of bass reflex design over

acoustic suspension design is that the relativelyhigher efficiency of the former permits thesame amount of bass to be produced with farless woofer travel or excursion. Since thisgenerally increases linearity of the response, itproduces less distortion, particularly in the lowbass.

(Also see BANDWIDTH, THIELE, TUNEDPORT)

BASS UNITA speaker designed for low frequencies only,

usually for use in conjunction with two or moresatellite speakers.

A bass unit is different from a sub-woofer inthat it does not claim full bass coverage and itis designed for use with specific satellites.

BEAMING (See DIRECTIONALITY.)

C

CAPACITORAn electronic element in which two metallic

plates are close to each other but not incontact, with voltage on one plate affecting thevoltage on the other. A capacitor will notconduct a direct current, but will allowalternating current to pass.

Capacitors have an impedance with respect tofrequency which declines at a regular rate of 6dB per octave. At low frequencies a capacitortherefore has high L, making it an excellentfilter for keeping low frequencies away from atweeter. Therefore, capacitors are commonelements in crossovers.

CAPACITANCEThe magnitude or size of a capacitor in

microfarads.

(See IMPEDANCE.)

D

DAMPINGAny form of resistance or friction, electrical,

mechanical, or acoustic.

Most of the damping of woofers is caused bythe amplifier (electrical damping). Fiberglass inspeaker enclosures is another form of damping(acoustical damping). In tweeters damping maybe accomplished by means of a magnetic fluidbathing the voice coil (See FERROFLUID).

In general, damping reduces the amplitude ofresonance

The careful control of damping is important inspeaker design because resistance or dampingis a factor in the calculation of Q, which greatlymodifies speaker response across a wideaudible frequency range.

DAMPING FACTORThe ratio of a speaker's impedance to the

output impedance of the amplifier which drivesit. Since speaker impedance is usually around 8ohms, and amplifier output impedance isgenerally less than .1 ohms, damping factorsmay reach or surpass 100.

Most amplifiers have comparable dampingfactors. An amplifier can be designed to createmore damping effect, but it is not certain that ahigher damping factor is better. Amplifierdamping is often related to negative feedback,which is not necessarily a good thing.

(See NEGATIVE FEEDBACK.)

DAMPING FLUIDDamping fluid is not necessarily ferrofluid, but

ferrofluid is so useful and versatile that it hascompletely replaced other types inloudspeakers.

(See FERROFLUID)

dBdB refers to the ratio between two power

levels. 10 dB is equivalent to a power ratio of10; 3 dB is equivalent to doubling; -3 dB isequivqalent to halving. 20 dB is multiplying by100. 100 dB means multiplying by10,000,000,000.

(see SPL, DYNAMIC RANGE.)

DIGITALA way of storing and processing bits of

information in a format that is suitable forcomputers to manipulate. Before digitalinformation can be heard from a loudspeaker ithas to be converted to analog in a D to Aconverter.

(See ANALOG.)

DIRECTIONALITYAt its highest frequencies, a speaker directs

almost all of its sound straight ahead . At lowfrequencies, sound radiates equally in alldirections. The former effect, referred to as"beaming", can be a problem in speaker design.(See DISPERSION.)

Beamed sound has a psychological effectwhich can be pleasant: it causes voices to

sound more "up front". It can also beunpleasant.

STEREO EFFECT is exaggerated with beamedsound. If you get good dispersion, there's a lotof sound arriving at your ear in complexpatterns: the first reflection, the second, etc.making it confusing to judge when the soundactually happened. The phase information usedby the mind to derive the stereo image isemphasized when beamed. This is one of theappeals of earphones, where vir tually all soundis beamed with no dispersion.

Some designers choose to use drivers in theirdirectional range (or beaming range) in order toobtain the desirable effects of beaming. If thedesigner is trying to achieve a more linearspeaker (with respect to dispersion) he willwish to eliminate beaming. This can be done bycrossover design, using crossovers to deprivedrivers of frequencies where they beam, orthrough driver design, since drivers can bedesigned so that they don't produce any soundat frequencies where they would beam.

Though directionality is generally thought of asa high frequency problem, it also occurs at themidrange frequencies at the "high-end" of thewoofer.

DOLBYDolby Labs is a company prominent in the

design and manufacture of hardware andsystems to modify the reproduction of sound,most notably for the "Dolby Prologic" and"Dolby Digital" systems.

(See HOME THEATER.)

DOME TWEETERThe original appeal of the domed tweeter is

that it physically resembles the sphericalwaveform which an ideal loudspeaker shouldproduce. Actually, the real advantage is that thedome shape gives the tweeter a very rigidstructure so that it does not deform at highfrequencies as much as a cone tweeter, e.g. thedome shape resists deformation and thereforehas a more uniform response.

The conventional domed tweeter is convex,with a voice coil of the same diameter.

Also see SOFT DOME TWEETER, INVERTEDDOME TWEETER)

DOUBLINGA speaker generally has some low frequency

at which there is a dramatic increase indistortion; reviewers generally refer to thisphenomenon as "doubling." The origin of theterm may be the fact that most speakers have atendency to produce the harmonics of any tonethey are required to reproduce, and one suchharmonic is double the original frequency. Alsothe loudness seems to double. In reality, it isthe third harmonic which sounds less pleasantthan the second, so that what is labeleddoubling may in effect be trebling.

Another type of distortion often called doublingoccurs when a speaker causes a low-frequencyvibration in the grill-cloth assembly. Anotheroccurs when a speaker goes beyond its normallimits of travel and hits up against itssuspension or frame (bottoms out).

DYNAMIC RANGE

The difference between the loudest and thesoftest sounds. This is normally expressed indB. The dynamic range of human hearing isabout 130 dB. The dynamic range of symphonicmusic is about 100 dB. For a typical CD it isabout 80 dB; for a typical LP, about 40 dB. Thelower limit of dynamic range is determined bybackground noise; the more noise, the lessdynamic range. The upper limit of dynamicrange is determined by physical restraint:amplifier power, for example; for human hearingit is physical pain; for absolute sound, it is theelastic limits of air.

(see dB, SPL,NOISE.)

E

ELECTROSTATIC RADIATORThe simplest form of electrostatic radiator is a

capacitor in which one of the plates is allowedto move, causing sound waves. The force iscreated by the alternating electric field whichcomes from the amplifier. Adding a polarizingvoltage to one plate of the radiator will usuallyimprove efficiency and lower distortion, somany electrostatic designs use power suppliesof their own. Very often high voltages areinvolved (up to 3000 volts) because efficiencyincreases with voltage. This voltage can beobtained from house current, in which case thespeaker will plug into the wall, or from theaudio signal. This latter technique causes someleakage and loss of signal, leading to clippingand a bit of distortion.

The area of the plate reached by electriccurrent gets smaller as frequency increases. (Itis, after all, a capacitor.) Designers can controlwhat part of the plate current goes to by use ofelectrodes in the plate, by use of multipleplates, and by controlling the conductivity of thematerial itself.

Polyvinylidene (of Saran-wrap fame is oftenused for plates because it has the rightcombination of conductivity and low weight.Mylar can also be used.

EQUALIZATIONYears ago, recording studios used speakers

which were chosen primarily for efficiencyrather that bandwidth. People in recording

studios had no idea what kind of high and lowfrequency response was going onto theirrecords. The introduction of the equalizerallowed them to change the power to thespeaker to make up for its deficiencies, and alot of studios can now hear stuff they couldn'thear before. Therefore the quality of sound onrecords, particularly in the last five years, hasimproved a great deal. This has in turn causedspeaker manufacturers to become more andmore interested in the high and low frequencyresponse of their products.

The improvement in records has also hadbeneficial effects on cartridge design. In turn,the improvement in cartridges allowed therecording industry to make yet another round ofimprovement through better hearing. This is,perhaps, the best example of symbiotic effect inaudio. Also true, of course, with speakers andother components.

The introduction of CD's and digital technologyhas accelerated this process even more.

EQUALIZERA component with lots of knobs, each one

representing a certain bandwidth, or frequencydivision (an octave or fraction of an octave)which allows you to boost or decrease energygoing to a speaker in that range. The result isthat you can compensate for speaker limitationsor acoustic distortion in the room itself. Nowcommon in recording studios and becomingmore common in living rooms.

F

FERROFLUIDFerrofluid is a trademark of Ferrofluidics, Inc.

It is truly a space age material, a magneticfluid, originally created for lubricating ballbearings in space. The liquid has tiny magneticparticles attached to the fluid base the waysoap attaches particles of dirt. This fluid flowstoward stronger magnetic fields.

In speakers, ferrofluid can be used in the gapof a tweeter magnet. Because of the fluid'smagnetic properties, it is held in the gap andcannot run out. The presence of this fluid helpscool and therefore protect the tweeter byimproving conductivity between the coil and theframe. ferrofluid also helps lower distortionbecause it prevents air movement in the gap.(This eliminates the possibility of spuriouswhine or whistle.)

Once sold at more than $100 an ounce, now abit cheaper, this fluid is more in the class ofoptimization than luxury. The net result is thatthe loudspeaker can take greater power inputand produce greater amounts of sound withoutburning out tweeters.

FILTERSomething which limits the bandwidth of

transmission. A filter can be electrical,mechanical or acoustic. Typically, filters are hi-pass, low-pass or band-pass, referring ofcourse to frequencies. For example, thesuspension of an automobile is a low-passfilter, hopefully blocking all but the very slowest

bumps from the tender sensibilities of thepassengers.

(See CROSSOVER, BAND-PASS.)

FLETCHER-MUNSON EFFECTFletcher and Munson proved conclusively that

at low volume levels, the responsiveness of theear to both high and low frequencies declines.In other words, as you reduce volume, bothbass and high treble disappear before themidrange sounds do. Many amplifiers have aloudness control to boost low and high-endresponse at low volume settings and thuscompensate for this particularity of the humanear.

(See LOUDNESS, HUMAN HEARUNG.)

FREQUENCYAn example of frequency is a single musical

note. Frequency was originally described ascycles per second, now simplified to Hz. (SeeHERTZ). The frequency of a second hand on aclock is one cycle per minute 1/60 Hz.A singlefrequency is a series of identical waves. Thenumerical value of the frequency is the numberof complete waves that pass a single point inone second.

(See OCTAVE, HARMONICS, WAVELENGTH.)

K

KLIPSCHORNBook shelf speakers seldom have efficiency

above one percent. For the Klipschorn (aninvention of Paul Klipsch), it's something about30%. The horn-loading makes it far moreefficient, but the speakers really have to be big.The Klipschorn principle uses the walls of theroom as effective extensions of the speakeritself. This effect applies only to sub-wooferfrequencies.

L

LINEAR, LINEARITYAs opposed to non-linear. When dealing with

cause and effect, an effect is linear when it isexactly proportional to the input. When you pullon a spring with a specific force, twice the forceshould produce exactly twice the deflection. Ina speaker, twice as much power from theamplifier should produce exactly twice as muchsound.

All devices have some degree on non-linearity,hence distortion.

LOUDNESSIn audio, a term which usually refers to the

principle (documented by Fletcher and Munson)that the response of the human ear to sound isnot regular, but varies enormously with theintensity or loudness of the music.

At very low levels both bass and treblefrequencies seem to decline more than themidrange frequencies. Many audio amplifierstherefore have some form of loudness controlwhich causes the amplifier to boost certainfrequencies at low-volume playback.

LOUDNESS CONTROLIdeally a loudness control should affect both

high and low frequencies. Actually, many so-called loudness controls affect only bassresponse, therefore doing only half the job. Thisis worth investigating when buying an amplifier.

Ideally, at concert-hall levels of sound, the

frequency response of the amplifier should beflat whether the loudness control is engaged ornot. Accurate compensation requires twocontrols, a gain control in addition to theloudness control. The gain control must be usedto compensate for gain variations in allelements of the system (speaker efficiency,room acoustics, room size, source level,amplifier gain, etc.) to set the amp to the onegain setting at which loudness contour willprovide a realistic balance.

Loudness systems which consist only of abutton to convert the volume control into aloudness control and back again can't usuallyprovide exact compensation. As a result, manyaudiophiles have never heard music with properloudness compensation.

Understanding loudness compensation isimportant because properly used it can providethe same sonic balance from a system at lowlistening level as at full volume. Loudnesscontrols, though, are generally misunderstoodand often are used simply to increase bassresponse (sometimes because people feelnervous about any deviation from "flat"response and fell vaguely that the loudnessbutton is "legal" while the bass control is not.)

M

MAGNETThe source of the magnetic field which

interacts with electrical current flowing throughthe voice coil wire to produce the force whichmoves the speaker cone.

Alnico, which used to be the material ofchoice, has been mostly replaced by ceramicferrites. In cases where the magnet has to bevery small or very strong, a neodymium alloy isnow used.

MOTORThe combination of magnet, its steel housing

and the voice coil. These parts provide thepower and the force to move the loudspeaker.

N

NEGATIVE FEEDBACKIn general, feedback is the application of a

portion of the output signal to the input signalof any system which has gain. The mostcommon usage of feedback is in audioamplifiers, since distortion in the output signalof an amplifier can generally be reduced byfeeding a percentage of the output signal backinto the input of the circuit with polarityreversed (hence the term "negative feedback").

In fact since all design is a matter of trade-offs, any decrease in distortion obtained by thistechnique must be paid for by a decrease ingain in the amplifier. Since negative feedback isessentially a corrective technique with aninevitable trade-off cost, a better solution is tocreate an amplifier with so little DISTORTIONthat negative feedback is not required to correctit.

Since negative feedback changes the dampingfactor of an amplifier (and therefore changes Q,therefore changing the frequency response ofthe speaker) some attention should be paid tothis question when choosing an amplifier sincespeakers may sound quite different when drivenby amplifiers with different amounts of negativefeedback.

NOISERandom sound at all frequencies. Produced

everywhere, even by the collision of moleculesin the air around us. (This noise is just belowthe level of sound audible to humans, but exists

nonetheless.) In audio, noise is also caused bythe flow of electric current through transistors,vacuum tubes, and resistors.

Since there is always noise in the listeningenvironment, sound-producing systems must beturned up loud enough to mask the noise. Thisfact may become a problem with components,like amps, which produce their own noise, sinceinternally-generated noise may increase fasterthan the musical signal as volume is increased.Though modern high fidelity equipment usuallygenerates so little noise that this not much of aproblem, some internally-generated noisealways shows up nevertheless in almost allcomponent-generated sound. (Also seeDISTORTION in PART TWO.)

Systems which are to be used in a noisyenvironment should include relatively efficientloudspeakers. In such environments, lowefficiency loudspeakers may require too muchpower in order to come up to levels whicheffectively mask ambient noise.

(Also see WHITE NOISE AND PINK NOISE.)

O

OCTAVEA frequency term: doubling or halving a

frequency. Called an octave because it is eightnotes of a musical scale.

Also see HARMONICS.

OVERTONESSame as harmonics

P

PASSIVE RADIATORA loudspeaker component that looks like a

woofer but isn't, for it has neither voice coil normagnet. Like a tuned port, a passive radiator ispart of a secondary sound producing systemused either to improve efficiency or to widenbandwidth by utilizing the real woofer's backwave.

A passive radiator may be loaded with moremass than can be obtained in a tuned port ofstandard size, so it may be the solution in aparticularly small cabinet. A sales advantage ofthe passive radiator is that it often makes thebuyer think he is getting a large woofer whenhe isn't.

PHASE or PHASINGSometimes called polarity, when it refers to the

plus/minus of interconnections. In a moregeneral sense, it refers to the timing of awaveform. Particularly important in stereo. Twospeakers connected to the amplifier out ofphase so that one is pushing (waveform isincreasing) while the other is pulling (waveformis decreasing) will usually sound flat. Mis-phasing can cancel out most of the bass,particularly if the speakers are close together.Speaker hook-up wire is generally color-codedor otherwise coded so that both speakers canbe grounded to the negative output connectionof the amp, putting them "in phase".

PHASE is also important in each individualspeaker system. Suppose you have a woofer

and tweeter producing the same soundsimultaneously. The timing or phasing of thesounds will be influenced by cross-over design,mass, , impedance etc.

In the more general meaning of phase, onecomplete cycle of a sound wave can beconsidered to be 360 degrees of phase. 180degrees is one half way through the soundcycle, etc. As frequency rises, inductance alonecan cause phase shifts of as much as 90degrees. At the cross-over point phase shifts asgreat as 120 degrees are not uncommon. Forthis reason, crossovers are sometimes wired180 degrees out of phase (by reversing wires)for a net reduction in mis-phasing or mis-timing.

Another interesting area of phase change isaround woofer resonance. Right at resonancethere is generally minimum phase shift, butphase does shift dramatically just above andjust below resonance.

In a speaker with high Q, phase shift aroundresonance will be greater. There is somedispute and discussion as to whether one canactually hear this phase shift. Since variationsin frequency response are often associated withvariations in phase response, it's difficult toknow which one is being heard. It's generallyaccepted that drastic shifts in phase areaudible as distortion. To put it differently, it'sdesirable to have a system in which phaseshifts only gradually with change in frequencyresponse

POLARITYA special case of phasing (either 0 or 180

degrees, plus or minus).If you touch a battery'sterminals to those of a woofer, the woofer willmove in one direction, either in or out. Theconvention is that if the woofer cone moves out,the positive terminal of the battery is touchingthe positive terminal of the woofer. In this casethe polarity is positive. If the battery's terminalswere reversed, the woofer cone would move in,representing negative polarity , or a reversal ofpolarity.

PRO LOGICProduced by DOLBY Labs for home theater

systems, using four amplifier channels for Left,Right, Center and Rear (Ambient) speakers.

S

SATELLITESVery small speaker enclosures with only a

tweeter or a mid-range and a tweeter. Theseare designed for high frequencies only and areusually combined with a bass unit, sub-wooferor other main speakers.

Satellites can be used as main speakers, whencombined with a sub-woofer or bass unit or asrear channel speakers.

(See HOME THEATER)

SOFT DOME TWEETERA dome tweeter made out of relatively soft

material, which allows radiation from only aportion of the dome (mostly adjacent to thebond to the voice coil)

(See DOME TWEETER.)

SPEAKER CONTROLSSome loudspeakers have controls which allow

the owner to modify their sound. Usually there'sa knob to change tweeter response, and inthree-way or four-way systems, a knob or knobsto change the intensity of midrange response.

The purpose of these controls is to permit thespeakers to be "tuned" to the room in whichthey will perform and/or to the ear of thelistener. Some individuals spend a great dealon speakers then fail to get maximumperformance from them by neglecting to findthe optimum settings for controls (a processwhich may take quite a bit of time and

experimentation.)

There's no system so good that it can't beimproved. Therefore minor adjustments tospeaker and electronic component controls mayeasily create an improvement in overall sound.The listener should feel free to experiment untilhe arrives at the sound quality which suits boththe environment and his own hearing. The ear,not some arbitrary ideal setting (e.g. flatcontrols) should be the ultimate test.

SPEAKER SPECIFICATIONSSomething to be used with extreme

skepticism.

Most specifications which are used to promoteand sell loudspeaker are simply those whichare easily made. The equipment used toproduce them is easily obtained and easy touse. So, most specifications you may readabout a piece of equipment are not generallyvery important to the performance of the unit.Every time someone invents a new piece of testequipment, one finds new specs getting intospeaker literature.

FREQUENCY RESPONSE isa specificationwhere there has been confusion for years.That's because there is no simple or agreed-upon way of measuring the frequency responseof a speaker. Microphone placement, room sizeand shape, reflecting surfaces, etc. may varyand give immensely different specifications forthe same speaker. For example, it's quite easyfor frequency response specifications to gofrom +/- 2 dB to +/- 10 dB simply byrepositioning the microphone, creating perfectly"accurate" yet completely differentspecifications for the same speaker.

Historically the meaning for frequencyresponse has been "any audio output in thatfrequency". In these terms, a response curvereading 15 Hz to 25 KHz is completelymeaningless because both these frequenciesare beyond the range of human hearing.

Furthermore, they are both outside the rangeof the usual test equipment used by speakermanufacturers to test their products. Thismeans that such specifications are either beingmade up by copywriters and engineers, or thatthey are judging by any kind of audio output.(For example, if you put 15 Hz into manyspeakers, you'll hear something. It won't be 15Hz, but one of its harmonics: 30, 45, Hz etc.)

On-axis measurement of frequency responseis also tricky. Lots of speakers have responseup to about 16 KHz +/- 3 to 5 dB if themicrophone is placed dead center in front of thespeaker. That kind of measurement gives goodspecifications. However, anywhere but straightahead the actual power output at the highestfrequencies may be negligible compared toother frequencies. (See DIRECTIONALITY.)

CROSSOVER frequency specifications? Whocares? The usual reasons for including them:they're easy to specify and fill out some of thewhite space on the page.

A basic tenet of science is that measuringtechniques inevitably affect the phenomenonbeing measured. A good example of this occursin the field of amplifiers. For years amplifiershave been judged by an inexpensive piece ofequipment to measure it. There are amplifierswhich sound better with their high harmonicdistortion than others with better specifications,but it's the ones with the best specs which sell

best. In speakers, a new piece of equipmenthas just become available to measure phasedistortion, and now all kinds of specificationsrelating to phase are appearing in theindustry's literature; yet it's a relativelyunimportant consideration. In this sense, theimportance given to specs by reviewers maynot be helping the public.

SPEAKER WIREAudiophiles with extremely sensitive hearing

claim that they can hear differences betweenvarious forms of speaker wire. Scientificevidence for this is very slight. Even straightwire has some inductance, and there is alwaysat least some capacitance between two wires inproximity to each other. It turns out that thereare some wires which have detectablereactance at audible frequencies and thereforeto infer that there may be some audible effects.

There are many conjectures about how wirecan cause a difference in sound, such asoxidation in the wire, magnetic eddy currentswithin thick wires, rectification between wirestrands, and interference between high and lowfrequencies.

What is certainly true is that the thinner andlonger the wire, the more resistance. Speakersusually have impedance of several ohms. Inorder that the resistance of the wire be smallcompared to that of the speaker, one half ohmwould be too much.

SPLSound Pressure Level is expressed in dB and

is defined in terms of the practical hearing

range of human hearing. For the human ear,silence is defined as 0 dB SPL. The thresholdof pain for the human ear is at about 130 dBSPL.

(See dB.)

STANDING WAVEAn acoustic resonance of high Q, generally an

annoying form of distortion, usually in the bass,caused by the shape and dimensions of theroom in which music is being reproduced. Whenthe distance between two parallel roomsurfaces is one fourth of the wave length of agiven frequency, or an odd multiple of the wavelength (three times, five times, etc.) thepressure of the reflected wave is in phase withthe wave itself, creating a room resonance atthat frequency.

On the other hand, if the distance between thetwo room surfaces is one half the wave length,or an integral multiple thereof, the pressure ofthe reflected wave is out of phase with the waveitself, creating a canceling at the frequencywhich is another form of distortion but a bit lessnoticeable.

Of the two types of distortion, the former is thegreatest problem, because it tends to augmentor complicate acoustic feedback.

Careful repositioning of speakers, carefulrepositioning of objects in the room (likefurniture) and the use of sound-absorbingmaterials on room surfaces are the classicsolutions to standing waves. The fewer parallelplanes there are in the room's surfaces, theless likely that there will be standing waves, sothat room acoustics are generally improved by

angling a wall or two, and/or the ceiling, whenthe room is being planned.

Organ pipes are based on standing waves.

(See Resonance, Q.)

STEREO and STEREO EFFECTAlso see HUMAN HEARING)

If a click is heard by both ears at once, it willappear to be straight ahead or behind thelistener. If the sound reaches one ear slightlysooner, the sound will seem to emanate fromthat side.

This is the principal cause of stereo effect, ashift in timing or phase.

However, a change in volume in one ear willhave a similar stereo effect. Because of studiomixing techniques, many stereo recordings useonly this volume differential to convey stereoinformation, and overlook or ignore the primaryinformation, timing. This stereo is not ascomplete, but is particularly common in poprecordings, where one track is recorded at atime and then added to the final tape.

At very low frequencies, however, phaseinformation in two channels is almost nilbecause of the wavelength of the sounds.Conversely, at frequencies where wavelengthcomes close to the size of the space betweenthe ears, (250-10,000Hz), the perception ofdirectionality increases.

SUB-WOOFERA separate speaker enclosure (often with its

own power amplifier) dedicated only to bassfrequecies, e.g., from 15 - 150 Hz. The theory is

that most stereo speaker systems lack one ortwo octaves of the deepest bass, and that thiscan be added with a separate speaker.Unfortunately many so-called sub-woofers arestill missing one or two octaves of the deepestbass.

Sub-woofers are often configured as onemonaural channel, on the assumption that lowfrequencies have very little stereo information.

(See also BAND-PASS)

T

THIELEAn Australian electrical engineer whose name

has become quite famous in audio circles.Thiele's work was based on the fact that anyloudspeaker system can be expressed inclassic electronic symbols. He then appliedfilter theory (a special branch of electronicanalysis) to speaker design.

The advantage of Thiele's work is that itmakes it possible for the designer to availhimself of the immense body of statistics andresearch that has gone into electrical filtertheory in order to obtain the desired frequencyand phase response in a new design withminimum trial and error.

Thiele's theories have been taken up andpopularized by Richard Small, who did a Ph.D.on Thiele's work.

Today's speaker designers often use filtertheory, analyzing loudspeakers as analogous toelectronic circuits. This approach is particularlyuseful for designs using either a port or apassive radiator, for Thiele's work is particularlyapplicable to the selective tuning of the port orradiator to achieve desired frequency response.Still, the Thiele approach is only one of severalmethods which may be used to arrive at thedesired result.

THIELE-SMALL PARAMETERSThese are the values of the basic parts of the

electronic circuit analogue proposed by THIELEand popularized by Small. They are related to

the physical properties of a woofer, e.g. masscompliance, resonance, Q, Bl, etc. They arecommonly circulated between manufacturersand design engineers because there are anumber of cookbook recipes which use theThiele -Small parameters for determining boxsize and port tuning.Computer programs arenow common both for measuring theparameters and for designing the enclosuresbased on them.

TRANSDUCERAny device which converts mechanical energy

to electrical energy, or vice versa. Therefore,speakers, microphones, generators, alternators,motors, cartridges, etc. In speakers there aregenerally three types of transducers: dynamic,or conventional magnet and coil and papercone; electrostatic, and piezo-electric effect.

In the dynamic type, sound comes from themovement of a coil in a magnetic field whencurrent passes through it. In electrostatic,variations in voltage on two plates causes oneplate to move in respect to the other (one plateeffectively replaces the magnet of the dynamicspeaker) transmitting a sound wave to the air inthe room. In the piezo-electric effect, currentcauses a change in the shape of the material, asolid, causing it to vibrate and transmit soundwaves to the air. (All these effects also work inthe opposite direction.)

Transducers are particularly important in highfidelity because they are used in speakers,microphones, and cartridges, and they all haveto be good for the sound to be good.

TRANSIENT RESPONSEA term often used ambiguously. Specifically,

transient response is the ability of a system toreproduce sudden changes, such as clicks orpops, especially at the beginnings ofcontinuous sounds,rather than a steadywaveform (sine wave).

In reality transient response is a reflection offrequency response. Pass a pulse through anysystem with a certain frequency response, andthe accuracy of reproduction of a transientwaveform will correspond to the limitations ofthe system's frequency response. A squarewave can be used to indicate transientresponse. If there's a deficiency in high endresponse there will be a rounding of the squarewave and a change in the vertical edge.

Though transient response is usually thoughtof as a high frequency function, there is alsosuch thing as low frequency transient response.Failure to handle this results in a tilt of thehorizontal section of the wave.

Some people confuse high Q with poor lowfrequency transient response, because drumsseem to be muffled in a high Q system, and thiscan be erroneously labeled "poor low frequencytransient response". Actually, poor lowfrequency transient response is of limitedimportance since the human ear does notusually recognize the absence of low frequencyharmonics (or sub-harmonics).

TRANSMISSION LINEOne type of transmission line is a type of bass

reflex system with the added characteristic ofproviding a long path for the rear wave to followso that by the time it gets out of the enclosure itis in phase (in a certain frequency range) withthe front wave. Not particularly useful, sincethis design offers neither the frequency rangenor the efficiency of a tuned port. It is howeverappropriate for those who prefer a softer, well-damped bass.

A second type of transmission line, lesscommon, uses a cabinet design which absorbsall the rear energy from the woofer, making itbehave as if it were mounted in an infinitebaffle.

TUNED PORT/BASS REFLEXA tuned port is simply a tube or opening

allowing air from inside the speaker box toescape or enter. Note that the air in a tunedport has the property of acoustic mass. Itmoves in the port without being compressed,has inertia, and therefore has its own resonantfrequency. The port is generally tuned(dimensioned) in the vicinity of the woofer'sresonant frequency in order to augment bassoutput. A tuned port can be used either toincrease efficiency or to increase frequencyrange, depending on the goals of the designer.

(See PASSIVE RADIATOR, BASS REFLEX.)

W

WAVELENGTHInverse to frequency, waves are short at high

frequencies and long at low frequncies. Thecorresponding range for 20 to 20,000 Hz is 50feet to 1/2 inch. Wavelength is the distancefrom crest to crest, similar to ocean waves.

(See FREQUENCY.)

WHITE NOISE and PINK NOISENOISE is often used in testing speakers

because it's easy to obtain. Also, a lot ofcompanies like to use noise as a signal sourcewhen measuring specifications because it doesnot show up peaks in the frequency responseas a pure tone would.

WHITE NOISE: noise in which there is equalenergy per frequency division. (For example,the same amount of energy between 100 and200 Hz as between 1100 and 1200).

PINK NOISE has equal energy distributedlogarithmically, for example, the same energybetween 100 and 200 Hz as between 1000 and2000. Pink noise corresponds fairly closely, onan average basis, to music. (More energy at lowfrequencies.) In listening tests with speakers,Pink noise is a better listening tool than Whitenoise. In white noise there is a greatexaggeration of treble. Surf is an excellentexample of white noise.

High frequency sound is attenuated in air(particularly humid air) so that the closer youare to surf (white noise) the shriller it sounds.

Even the humidity in your living room will tosome degree influence the treble response ofyour speakers. On cold winter mornings, soundtravels well, not just because the air is cold,thus dense, but also because of its dryness.(Very cold air rejects humidity.) Probably no-one will seriously suggest getting adehumidifier for your living room in order toimprove the high end response of your soundsystem. Still, acoustically speaking, it wouldhelp.

WINSLOWBURHOE

A loudspeakerdesigner sincethe early1960's, starting

at Acoustic Research, becominga production engineer at KLHand founder of EpicureProducts with a number ofbreakthrough speaker designs.Since then he has designedhundreds of speakers forcompanies that include BostonAcoustics, Inkel, GenesisPhysics, Energy, Nuance, andSynergy.