FLASH­BACK FEA­TURE

Sound & Vision - - CONTENTS -

21 Au­dio Myths

Myth­bust­ing Stereo Re­view- style. We look back at Peter Mitchell’s 1983 fea­ture tack­ling top­ics rang­ing from weighted specs to belt-drive vs. di­rect-drive turnta­bles.

and, later, Sound & Vi­sion, have been blessed through the years with the re­views, col­umns, and fea­tures of a great many su­per­star ex­perts. The list of pro­lific writ­ers who have graced the mag­a­zine’s mast­head as ei­ther a full-time or free­lance editor is a who’s who of au­dio in­dus­try celebri­ties. Their col­lec­tive con­tri­bu­tion to the hobby sim­ply can­not be over­stated. If you’re a loyal reader for some time you’ll rec­og­nize these names: Ju­lian Hirsch, David Ranada, Larry Klein, Ivan Berger, Tom Nou­saine, and even long­time cur­rent con­trib­u­tors Ken Pohlmann and Daniel Ku­min. Peter Mitchell, whose work we re­pro­duce here, is an­other mem­ber of this ac­com­plished group. At one time a con­trib­u­tor to sev­eral au­dio pub­li­ca­tions and the pres­i­dent of the Bos­ton Au­dio So­ci­ety, Mitchell brought a fact-based, en­gi­neer­ing ap­proach and a re­fresh­ingly clear writ­ing style to both his fea­ture sto­ries and, later, his “High End” col­umn that graced the back in­side page of SR un­til his un­timely pass­ing. This ar­ti­cle, which ap­peared in the July 1983 is­sue, was in the vein of so many of the help­ful how-to and shop­ping sto­ries in SR and S&V that at­tempted to teach while de­bunk­ing the mis­in­for­ma­tion ram­pant among au­dio­philes. You’ll note that while some of Mitchell’s “myths” ad­dress dated tech­nolo­gies and con­sti­tute a nos­tal­gic walk down mem­ory lane, oth­ers—even his com­ments about vinyl—re­main both rel­e­vant and time­less. Es­pe­cially this: “To choose au­dio com­po­nents, lis­ten to them, not to the­o­ries and claims about them.” A real pearl, that one. — ROB SABIN

hop­ping for hi-fi com­po­nents can be con­fus­ing enough even when you have all your facts straight. And if you sub­scribe to many of the com­mon myths and mis­un­der­stand­ings about how au­dio equip­ment works, how spec­i­fi­ca­tions re­late to what you hear, and what all of the tech­ni­cal jar­gon means, you’re re­ally in trou­ble. Some mis­con­cep­tions have their ori­gin in mis­lead­ing claims made by sales­peo­ple or in ad­ver­tise­ments; oth­ers arise from the won­drously com­plex and sub­tle na­ture of the hu­man hear­ing process, which in­evitably gets in­volved in the judg­ments that peo­ple make about how good a stereo sys­tem sounds—or how they as­sume it ought to sound.

Let’s shoot down some of the hot-air bal­loons that con­tin­u­ally arise in hi-fi, tak­ing as our gospel the prin­ci­ple that there are ex­cep­tions to al­most ev­ery rule. To choose au­dio com­po­nents, lis­ten to them, not to the­o­ries and claims about them. And re­mem­ber that what you hear in any par­tic­u­lar case may be in­flu­enced as much by the fac­tor of com­pat­i­bil­ity—be­tween a sty­lus and a tone arm, be­tween an am­pli­fier and a speaker, be­tween speak­ers and room acous­tics—as by the qual­ity of in­di­vid­ual com­po­nents. If a sys­tem sounds good, it is good, re­gard­less of the­ory. If it sounds bad, some­thing in it prob­a­bly is bad—but the fault may not be what you think it is. The twenty-one mis­con­cep­tions dis­cussed here, in no par­tic­u­lar or­der, are among those we have found to be most com­mon.

Weighted spec­i­fi­ca­tions are the au­dio in­dus­try’s way to cheat by mak­ing the num­bers look bet­ter.

False. Weight­ing is an ef­fort to make test equip­ment “hear” the way the ear does, so as to pro­duce mea­sure­ments that ac­cu­rately pre­dict what we will hear. For in­stance, A-weighted mea­sure­ments of back­ground noise cor­rectly re­flect the fact that at low vol­umes the ear is sen­si­tive to even very small amounts of noise oc­cur­ring at mid-tre­ble fre­quen­cies (around 3 khz) while much larger amounts of noise at low bass fre­quen­cies are in­audi­ble.

Okay, then, un­weighted spec­i­fi­ca­tions are mean­ing­less.

Wrong again. Al­though un­weighted specs of­ten don’t cor­re­late di­rectly with what we hear, they can alert you to other prob­lems. For in­stance, if a turntable’s rum­ble is con­cen­trated at fre­quen­cies be­low 10 Hz, where the ear can’t hear it, the DIN-Bweighted rum­ble fig­ure is likely to be down around -60 or -70 db, cor­rectly pre­dict­ing that you won’t hear the rum­ble it­self in play­back. How­ever, if the un­weighted rum­ble fig­ure for the same turntable were -30 db or worse, that could in­di­cate un­wanted sty­lus vi­bra­tion that would be heard—not as rum­ble, but as flut­ter and mis­track­ing. Sim­i­larly, if a prod­uct’s A-weighted sig­nal-to-noise ra­tio (S/N) is good but the un­weighted S/N is much worse, it may have ex­ces­sive 60-Hz hum since A-weight­ing re­duces the in­flu­ence of any power-line hum on an S/N mea­sure­ment. Records must be stored ver­ti­cally, never ly­ing flat. Only half true. Ac­tu­ally, once you un­der­stand that record vinyl is a con­gealed liq­uid that yields un­der pres­sure (like very thick mo­lasses), the two pri­mary rules of record stor­age will be ob­vi­ous: (1) Records should be sub­jected only to light pres­sure; heavy pres­sure may press loose dust or wrin­kles from the plas­tic liner into the vinyl

sur­face. (2) Any pres­sure should be distributed evenly over the disc; un­even pres­sure may cause warp­ing. Thus, ver­ti­cal stor­age is fine (re­ally ver­ti­cal, not lean­ing; fill empty spa­ces with card­board). But hor­i­zon­tal stor­age on closely spaced shelves is also okay; you can stack up to a dozen discs on a level sur­face be­fore the pres­sure on the bot­tom disc be­comes too great. In ei­ther case, be sure that the discs’ jack­ets are not them­selves warped or tight enough to cause warp­ing.

A 60-watt am­pli­fier will play 20 per­cent louder than a 50-watt am­pli­fier, and a 100-watt amp will play twice as loud.

Nope. A 20 per cent in­crease in avail­able wattage amounts to less than 1 db of in­creased loud­ness ca­pa­bil­ity. Dou­bling the power in­put will give a 3-db in­crease in vol­ume, which can be no­tice­able but is def­i­nitely not dra­matic. It’s a mat­ter of bi­ol­ogy: our eyes and ears have an ap­prox­i­mately log­a­rith­mic re­sponse to light and sound so that they can cope with the mil­lion-to-one range in iñten­si­ties that they are ex­posed to. In any stereo sys­tem only 1 to 10 watts of power are ac­tu­ally used, on av­er­age, to gen­er­ate “loud” sound lev­els with typ­i­cal mu­sic. An am­pli­fier’s abil­ity to put out more power does, how­ever, in­flu­ence its sonic clar­ity, “open­ness,” and low-bass im­pact, es­pe­cially dur­ing tran­sient peaks and cli­maxes.

Any two 50-watt am­pli­fiers should sound alike.

Well, sort of. Ac­tu­ally, a well-made 20-watt amp and a 200-watt amp will sound alike much of the time. But if you are con­cerned about those tran­sients and cli­maxes that stress an am­pli­fier’s ca­pac­ity to the max­i­mum, then the rated power is only a very rough guide be­cause it is mea­sured us­ing an 8-ohm re­sis­tor in­stead of a loud­speaker. “Power” is the elec­tri­cal prod­uct of both voltage and cur­rent. Two am­pli­fiers with the same power rat­ing usu­ally have the same max­i­mum voltage out­put, but they may have very dif­fer­ent out­put cur­rent ca­pac­i­ties, which can make an im­por­tant dif­fer­ence in driv­ing a loud­speaker that has a low or com­plex (“re­ac­tive”) im­ped­ance.

Mov­ing-mag­net (MM) phono cartridges are not as good as mov­ing-coil (MC) cartridges.

As cartridges of both types con­tinue to im­prove, the ac­cu­mu­lat­ing ev­i­dence in­di­cates that it re­ally doesn’t mat­ter whether the mag­net or the coil does the mov­ing. In var­i­ous com­par­isons among highperformance MC and MM cartridges— notably a set of care­fully con­trolled lis­ten­ing tests su­per­vised by Cana­dian re­searcher Floyd E. Toole—the au­di­ble dif­fer­ences in tim­bre and de­tail have con­sis­tently been re­lated to the cartridges’ known dif­fer­ences in fre­quency re­sponse. When these dif­fer­ences were equal­ized, the MM and MC pick­ups sounded alike.

A com­po­nent rated at 0.01 per cent to­tal har­monic dis­tor­tion (THD) will sound bet­ter than one rated at 0.1 per cent THD.

Bi­ol­ogy again. Dis­tor­tion gen­er­ates false tones at fre­quen­cies other than those in the orig­i­nal sig­nal. If these dis­tor­tion com­po­nents are suf­fi­ciently weak com­pared to the orig­i­nal sig­nal, they won’t be heard. If you can’t hear them, re­duc­ing them still fur­ther be­low the thresh­old of au­di­bil­ity won’t make them any more in­audi­ble. The ac­tual thresh­old of au­di­bil­ity de­pends on the fre­quen­cies in­volved in both the orig­i­nal sig­nal and the dis­tor­tion. With mu­si­cal sig­nals of typ­i­cal com­plex­ity, tests have re­peat­edly shown that dis­tor­tion lev­els be­low 3 per­cent aren’t heard even by ex­pe­ri­enced au­dio­philes.

Sen­si­tiv­ity is the most im­por­tant spec­i­fi­ca­tion of an FM tuner.

Per­haps— if you are lo­cated more than fifty miles from your fa­vorite sta­tion and can­not use a roof an­tenna. In the ur­ban and sub­ur­ban lo­ca­tions where most peo­ple in the U.S. live, how­ever, sig­nal strengths of sev­eral hun­dred mi­cro­volts are typ­i­cal, and the usual prob­lem is in­ter­fer­ence (due to mul­ti­path re­flec­tions or strong ad­ja­cent sta­tions). There­fore, for the ma­jor­ity of FM lis­ten­ers the re­ally im­por­tant

FM- tuner spec­i­fi­ca­tions are cap­ture ra­tio, AM re­jec­tion, and al­ter­nat­e­chan­nel se­lec­tiv­ity.

Bass de­pends on woofer size.

A large woofer can al­ways re­pro­duce deep bass bet­ter than a small woofer. The prob­lem here is to dis­tin­guish be­tween qual­ity and quan­tity. The quan­tity (the vol­ume level) of deep-bass out­put is strictly de­pen­dent on the amount of air that is moved, which equals the area of the woofer cone mul­ti­plied by its “ex­cur­sion” (backand-forth move­ment). Thus, a large woofer can re­pro­duce bass at higher max­i­mum vol­ume lev­els; con­versely, at a given high vol­ume level, a large speaker can usu­ally re­pro­duce lower fre­quen­cies with less dis­tor­tion than a small one can. But at mod­er­ate vol­ume lev­els the deep-bass “reach” of a speaker is a mat­ter of de­sign choice; some 8-inch woofers have use­ful re­sponse down to 25 Hz while some 12-inch woofers roll off steeply be­low 50 Hz. Deep-bass re­sponse is not free: to ex­tend the bass you must ei­ther re­duce ef­fi­ciency (thus re­quir­ing more am­pli­fier power for those cli­maxes) or use a big­ger, costlier cabi­net.

A three-way speaker sys­tem is bet­ter than a two-way sys­tem.

The main ad­van­tage of a three-way sys­tem is higher power-han­dling: it can play louder with­out burn­ing out its voice coils, a sig­nif­i­cant con­sid­er­a­tion if you are try­ing to re-cre­ate rock-con­cert sound lev­els in a very large room. The purely sonic ad­van­tages of a three-way de­sign, how­ever, are small in the­ory and some­times nonex­is­tent in prac­tice. Par­tic­u­larly in the mid-price range of speak­ers, a sys­tem em­ploy­ing two high-qual­ity driv­ers and a care­fully tai­lored crossover of­ten out­per­forms one

with three cheaper driv­ers and a com­pli­cated crossover. The proof, of course, is in the lis­ten­ing.

Sep­a­rate com­po­nents (tuner, 11 pream­pli­fier, power am­pli­fier) are bet­ter than an all-in-one re­ceiver.

Some­times yes, but of­ten not. Sep­a­rates of­fer greater flex­i­bil­ity, of course, and some in­clude more elab­o­rate cir­cuits or fea­tures (se­lectable wide/nar­row tuner i.f. fil­ters, for in­stance) that can prove use­ful in spe­cial cir­cum­stances. Also, very few re­ceivers of­fer more than 100 watts per chan­nel, so users who need or want more power may have to go the sep­a­rates route. But a few man­u­fac­tur­ers have found it more cost-ef­fi­cient to make in­te­grated am­pli­fiers and re­ceivers us­ing the same cir­cuitry as in their sep­a­rates; such a re­ceiver ac­tu­ally con­sists of tuner and am­pli­fier sep­a­rates in a sin­gle hous­ing.

A belt-drive turntable is bet­ter 12 than a di­rect-drive turntable, or vice versa.

Nei­ther. The best ex­am­ples of ei­ther type are su­perb. Among lower-priced units, each type has its strong and weak points. For in­stance, even a low-priced di­rect-drive sys­tem can eas­ily be made to pro­vide vari­able pitch and ex­act speed reg­u­la­tion. Belt-drive de­sign, on the other hand, makes it easy to float the plat­ter and tone arm on springs for iso­la­tion from in­ter­nal and ex­ter­nal vi­bra­tions. Take your pick.

13 Dig­i­tal tuners are bet­ter than “ana­log” tuners.

The ba­sic ad­van­tage of dig­i­tal-syn­the­sis tun­ing is its con­ve­nience: quick, pre­cise, push­but­ton se­lec­tion of fa­vorite sta­tions. In terms of sen­si­tiv­ity and sound qual­ity, though, the tun­ing method is ir­rel­e­vant— ex­cept in those few dig­i­tal tuners with in­ad­e­quate in­ter­nal shield­ing that al­lows noise and whis­tles from the dig­i­tal cir­cuitry to leak into the au­dio.

Chrome and metal tapes cause 14 more rapid head wear than fer­ric tapes tend to do.

This old ca­nard has been con­sis­tently proved false in tests. Poorly made “bar­gain” tapes are the only ones likely to cause rapid head wear, and these, of course, are mostly low-grade fer­rics. With good tapes from rep­utable man­u­fac­tur­ers there is no clear cor­re­la­tion be­tween tape type and head wear. (With all tape types wear does tend to in­crease with high hu­mid­ity, though.)

Chrome and metal tapes have 15 more dis­tor­tion than fer­ric tapes do.

This is true at high record­ing lev­els (0 VU and above), but the dif­fer­ences in dis­tor­tion are slight. More to the point, at lower record­ing lev­els the dis­tor­tion de­creases rapidly to in­audi­bil­ity with all tape types.

So, to make record­ings on high-bias tapes that are as dis­tor­tion-free as those on premium fer­ric tape, sim­ply de­crease your record­ing lev­els by about 2 db.

Play­ing a “nor­mal” (fer­ric) tape 16 in the chrome (high-bias) po­si­tion will dam­age the record­ing.

No way. Dur­ing play­back, mis-set con­trols may cause poor sound, but the sig­nal on the tape won’t be al­tered— un­less you ac­ci­den­tally set the deck for record and erase the tape!

Over­load­ing a tape recorder 17 (by push­ing its level in­di­ca­tors strongly into the red) may dam­age the ma­chine.

Not even a lit­tle bit. Oh, it’s con­ceiv­able that you might bend a me­ter’s nee­dles if you “pin” them hard enough, but even that is very un­likely. As for the recorder’s elec­tron­ics, they can be dam­aged by con­nect­ing the 120-volt a.c. power line to an in­put jack but not by any au­then­tic au­dio sig­nal.

Tone con­trols should al­ways be 18 set “flat” for the most ac­cu­rate sound.

This might be a rea­son­able no­tion if ev­ery other el­e­ment in the record­ing and play­back chain (from mi­cro­phone to speak­ers to room acous­tics) were known to be “flat,” but of course that’s not so, at least not yet. Re­gard­less of how good your play­back sys­tem is, record­ings vary a great deal in tone qual­ity (some­times be­cause of equal­iza­tion added to com­pen­sate for im­per­fec­tions in the stu­dio’s mon­i­tor speak­ers). In the ab­sence of any ob­jec­tive stan­dard of ac­cu­racy, it sim­ply makes sense to use tone con­trols to ob­tain the sound that seems nat­u­ral and life­like to you.

Cir­cum­au­ral head­phones (the 19 kind with a rub­ber ring that fits all around the ear, mak­ing an air­tight seal) are bet­ter than the open-air types that sim­ply rest on the outer ear.

Cir­cum­au­ral phones have two ad­van­tages: ex­tended deep-bass re­sponse is eas­ier to ob­tain, and the air­tight seal ef­fi­ciently ex­cludes ex­ter­nal sound (an im­por­tant con­sid­er­a­tion in live on-lo­ca­tion record­ing). Open-air phones tend to be more com­fort­able to wear and can sound equally good. In Stereo Re­view’s July 1982 lis­ten­ing tests of fif­teen head­phones, the three high­est-ranked mod­els were an open-air, a cir­cum­au­ral, and a quasi-cir­cum­au­ral de­sign with a “leaky” foam ring in­stead of an air­tight rub­ber sur­round. Ev­i­dently no one de­sign ap­proach is un­equiv­o­cally the best.

20 Un­like discs, tapes don’t wear out with re­peated play­ing.

They do, but in a less ob­vi­ous way. With worn discs, noise and dis­tor­tion are added to the sound. When tapes are played a great many times there are sig­nal losses, dropouts and high-fre­quency rolloffs, caused by the rub­bing and flex­ing of the tape as it is pressed against the deck’s heads, cap­stan, and guide posts. The highs may also be par­tially erased by resid­ual mag­netism in these metal parts, hence the need for pe­ri­odic de­mag­ne­tiz­ing.

21 Dig­i­tal Com­pact Discs (CDS) are vir­tu­ally in­de­struc­tible.

Not so. It is true that or­di­nary sur­face dust, fin­ger­prints, and light lin­ear scratches have lit­tle or no ef­fect on them and that wip­ing a dirty CD clean usu­ally re­stores pris­tine play­back qual­ity. But a curved scratch that fol­lows the CD’S spiral sig­nal path can make it un­playable. There­fore, when clean­ing a CD, do not use the cir­cu­lar brush­ing mo­tion that is cus­tom­ary with ana­log LPS; wipe the disc from cen­ter to edge. And re­mem­ber that the CD’S sig­nal sur­face is embed­ded di­rectly be­neath the la­bel, pro­tected only by a thin coat­ing of lac­quer. A scratch that pen­e­trates through the la­bel is likely to wreak more havoc than a scratch on the trans­par­ent-plas­tic-coated “play­ing” side of the disc.

Peter W. Mitchell, one of hi-fi jour­nal­ism’s most pro­lific writ­ers, is also pres­i­dent of the Bos­ton Au­dio So­ci­ety and of his own elec­tron­ics con­sult­ing firm.

Newspapers in English

Newspapers from USA

© PressReader. All rights reserved.