Tp ch How Stuff Works c lot bi tm hiu c ch hot ng ca loa, t vic pht m, thit k loa nh hng th no n cht m pht... hiu loa hot ng nh th no, trc tin cn phi hiu m thanh hot ng ra sao. Bn trong tai ngi c mt mng da rt mng gi l mng nh. p sut bin i lin tc trong khng kh s tc ng n mng nh lm chng rung ln. Khi mng nh rung ln, no b s dch cc rung ng ny thnh m thanh. l cch con ngi nghe. Mt vt th to ra m khi n rung ng trong khng kh. Khi vt th rung ng, n lm cc ht kh xung quanh chuyn ng theo. Cc ht kh ny li tc ng ln cc ht kh bn cnh n chuyn ng tip, t mang theo xung rung ng truyn qua khng kh n tai ngi. Theo cch trn, vt th rung ng gi mt sng dao ng thng qua khng kh, v khi dao ng ny ti tai ngi, n s lm mng nh rung ln. No b s dch cc rung ng ny thnh m thanh ca vt th . Phn bit m thanh

Cu to c bn ca loa. nh: Howstuffworks.

Con ngi nghe c m thanh khc nhau t cc vt th rung ng khc nhau bi nhng yu t sau: Tn s sng m Sng m tn s cao n gin l p lc khng kh dao ng vi tc nhanh trong mt khong thi gian nht nh. No b s bin dch cc dao ng ny di dng m cao. Khi cng mt khong thi gian nh vy nhng t dao ng hn, m s thp hn. Mc p sut khng kh y l bin ( ln) ca sng m, quyt nh mc m lng ca m thanh. Sng m vi bin ln s lm mng nh rung ng mnh hn, no b s din dch rng m thanh ny to hn. C mt thit b cng hot ng tng t nh tai ngi, l microphone dng thu m. N cng c mt mng rung ng theo sng m trong nhng mi trng nht nh. Sng m thu c t micro ny s c m ha v c lu trong bng t, CD di dng mt tn hiu in t. Khi cc tn hiu ny c gi n loa, loa s bin dch li thnh rung ng vt l ca mng loa. Cc loa cht lng tt thng c thit k ti u sao cho rung ng vt l ca mng loa s ti to c gn nh nguyn vn m thanh thu c t micro. To m thanh Loa, v c bn, l mt b my bin dch u cui hot ng ngc vi microphone. Loa chuyn tn hiu in t trong cc phng tin lu tr thnh rung ng c hc ti to sng m sao cho ging vi sng m thu c t microphone nht. Cc loa truyn thng thc cht thng gm mt hay nhiu loa con (hay cn gi l c loa - driver). Mng loa (Diaphragm)

Cu to ca mt loa tiu biu gm khung st, nam chm vnh cu v mng giy. nh: Howstuffworks.

Loa con to sng m bng vic rung mng loa (cone hoc diaphragm) vi tc cao. - Mng loa thng c lm t giy, nha hay kim loi, trong phn vnh rng c gn vi vin treo (suspension). - Vin treo, hay vnh loa, l mt vnh trn bng vt liu co gin, cho php mng nn chuyn ng vo ra. Vin treo ny c gn vi khung kim loi ca loa (basket). - Phn vnh hp ca mng nn loa c ni vi cun m (voice coil). - Cun m gn vi khung kim loi bng mng nhn (spider) vn cng l mt vnh trn bng vt liu co gin vi nhim v gi cho cun m lun ng v tr chnh gia nhng vn cho php cun ny chuyn ng vo ra. i vi mt s loi loa nht nh, mng loa c thit k dng vm (dome) thay v nn (cone). Cun m

Khi dng in chy qua cun m i chiu, hng cc ca cun m cng i chiu theo.

nh: Howstuffworks. Cun m thc cht l mt nam chm in t. Nam chm in t gm mt cun dy qun vng quanh mt li kim loi (thng l st). Khi cho dng in chy qua, cun dy s sinh ra mt t trng xung quanh lm cho st c t tnh. T trng ny tng t nh t trng xung quanh nam chm vnh cu, cng gm cc Bc v cc Nam v cng ht kim loi. Nhng khng nh nam chm vnh cu, nam chm in t ngi ta c th o cc Bc Nam bng cch o chiu dng in.

Dy t h thng m thanh s c ni vi loa con bng hai u ni trn. nh:Howstuffworks.

C ch ny cng tng t nh cch thc ca tn hiu stereo, cng i chiu in t lin tc thng qua hai u ni en vn rt quen thuc i vi nhng ai hay phi ni loa. V c bn, b khuch i (amplifier) lin tc thay i tn hiu in, dao ng gia dng dng v dng m ca dy . Do in t lun chy theo mt chiu gia cc dng v cc m, dng in chy qua loa cng o chiu lin tc to thnh dng xoay chiu. Dng xoay chiu ny n lt n s lm o cc nam chm in t lin tc nhiu ln trong mt giy. Nam chm

Khi dng in chy qua cun m i hng, cc ca cun m cng o chiu. Hot ng ny lm thay i lc t trng tc ng gia cun

m v nam chm vnh cu, theo lm cho cun m cng mng loa gn vi n chuyn ng theo. nh:Howstuffworks. Di y l cch thc m dao ng in c th khin cho cun m chuyn ng vo ra. Nam chm in t c t trong t trng c nh ca nam chm vnh cu. Hai nam chm ny (in t v vnh cu) tng tc vi nhau nh hai nam chm bnh thng, tri du ht nhau, cng du y nhau. Khi cc ca nam chm in thay i, chng hn t cc dng sang cc m s to nn lc t ht sang y i vi cc m ca nam chm vnh cu. Lc tc ng ny khin cho cun m chuyn ng vo ra lin tc theo dao ng in tng t nh mt chic piston. Khi cun m chuyn ng, do c gn vi mng loa nn mng cng s chuyn ng theo. Mng loa chuyn ng khin cho khng kh pha trc loa b rung ng, t to ra sng m. Tn hiu in t cng c th c bin dch thnh dng sng, theo , tn s v bin ca sng in t ny s tc ng v iu khin cun m chuyn ng theo t l v khong cch nht nh. Do sng in t ny l dng m ha ca sng m gc nn chuyn ng mng loa theo t l v khong cch nht nh n lt n s to nn sng m ng vi tn s v bin m n c m ha. Cc kch c loa con khc nhau thng c ch to phc v cho nhng di tn nht nh. Thng thng di tn ca mt loa s c chia nh v c th hin bi nhiu loa con khc nhau. (sohoa)

Mc d nguyn tc hot ng nh nhau, nhng loa vn c chi thnh 3 loi chnh da theo kch c v cng sut, l loa trm, cao v trung.

Loa trm (woofer)Loa cao (tweeter)Loa trung (mid-range)

Loa trm c kch c ln nht, c thit k ti to cc m tn s thp. Loa cao thng nh hn, c thit k ti to nhng tn s cao. Cn loa trung ti to di tn nm qung gia. Vic phn chia thnh cc loa khc nhau thc cht cng nhm mt s mc ch nht nh. Chng hn, to ra cc sng tn s cao, mng loa phi rung ng nhanh, v th loa chuyn tn s cao khng th c kch c ln v mng loa s c trng lng ln. Ngc li, kh c th lm cho mt loa nh rung chm to ra cc m c tn s rt thp bi n vn chuyn p ng tn s nhanh.

Di tn

B phn tn c bn ca mt loa: tn s c chia bi cun cm v t in v c gi n cc loa trm, loa tweeter v loa trung.

c cht lng m thanh trong mt di tn nht nh t hiu qu mong mun, ngi ta chia ton b di thnh nhng di nh hn cho mi loa ring bit. Cc h thng loa cht lng cao v th thng c c loa trm, trung v tweeter trong mt thng loa. Tt nhin, mi loa con chi ch mt di tn c th, h thng phi tin hnh chia nh cc tn hiu m thanh thnh cc di khc nhau gm di tn s thp, tn s cao v tn s trung. Cng vic ny c thc hin bi b phn tn (crossover). Hin nay ph bin nht l b phn tn th ng, c ngha l b ny hot ng ch da trn cc tn hiu m thanh i qua m khng cn bt k ngun nui c lp no. Loi phn tn ny s dng cc cun cm v t in, hoc i khi c th thm cc thit b mch. C ch hot ng ch yu da trn nguyn l c t in v cun cm tr thnh cht dn ch trong mt s iu kin nht nh. V d, t phn tn l cht dn hon ho khi tn s mt mc nht nh, thp hn mc ny s dn km i, trong khi cun cm li ngc li, ch dn tt khi tn s thp hn mt mc nht nh. Khi tn hiu in t qua dy ti loa, n s c i qua b phn tn. ti loa tweeter, dng in s i qua t in. ti loa trm, dng in i qua cun cm. Tn hiu in ti loa trung s qua mt b phn tn chy qua c t in v cun cm, t xc nh im giao ct trn v di ca di tn cho loa. B phn tn cng c th c ch to dng phn tn ch ng. Phn tn ch ng gm cc thit b in t c th p cc di tn khc nhau ca tn hiu m thanh trc khi cc tn hiu ny ti b khuch i (trn tng loa con). Phn tn ch ng c li th hn phn tn th ng ch c th d dng iu chnh di tn. Di tn ca phn tn th ng ph thuc vo tng mch ring r, v th mun thay i ngi ta s phi thay t in v cun cm. Tuy li th hn nhng phn tn ch ng khng thng dng bng phn tn b ng do chi ph cho thit b s lm i gi thnh ln nhiu. Cc loi thng loa

thit k thng loa kn, khng kh trong thng lin tc b nn khi mng loa chuyn ng.

Trong hu ht cc h thng loa, loa con v b phn tn c b tr trong cng mt thng. Vic b tr tt c trong mt gip cho vic sp xp loa c d dng hn. Thng loa thng c lm bng g hoc cc vt liu cng v nng o bo trit tiu cc rung ng qu trnh hot ng. Thit k thng th no cng c nhng nh hng nht nh ti cht lng m thanh c to ra. Thng thng ni n loa, ngi ta thng ch tp trung vo vic mng loa rung ng s ti sng m pha trc mt. Nhng mng loa khi chuyn ng ngoi vic lm cho khng kh pha trc chuyn ng, n cn to khng kh bn trong thng cng chuyn ng theo. Chuyn ng sng m ny gi l sng ngc v cc loi thng loa khc nhau s c cc cch x l sng ngc khc nhau. Loi thng loa thng dng nht l dng thng kn, hay cn gi l thng trit m, thng c bc kn khng kh bn trong khng th thot ra ngoi. Do cc sng ngc ch quanh qun trong hp nn khi mng loa chuyn ng, p sut khng kh trong v ngoi thng lun b thay i theo. Lung khng kh c trong v ngoi v th lun c xu hng b p sut, y mng loa tr li v tr "cn bng bn", v tr m p sut trong v ngoi loa bng nhau. Thit k thng loa dng ny km hiu qu hn cc kiu thit k khc bi b khuch i s phi gia tng tn hiu b lc tc ng. B li, nh c cn bng p sut m mng loa lun c tr v v tr ng, to nn mt cht m cht v chnh xc hn.

Chuyn ng p khng kh ni ti ca mng loa s y sng ngc ra ngoi l thot, t gia tng thm cho mc m thanh tng th.

Mt s cch tip cn khc li thit k theo kiu b sung thm mt l nh trn loa. Trong nhng h thng loa di (bass reflex), chuyn ng p khng kh ni ti ca mng loa s y sng ngc ra ngoi l thot, t gia tng thm cho mc m thanh tng th. Li th chnh ca loa di l tnh hiu qu. Lc chuyn ng ca mng loa con c th tc ng to hai lung sng m thay v ch mt. Tuy nhin, im bt li ca thit k ny ch do khng c s cn bng p sut nn m thanh khng c chnh xc bng. Mt kiu thit k khc l kiu phn m th ng, vn rt thng dng trong vic ch to cc loa trm. Sng ngc khi chuyn ng trong thng loa, thay v thot ra ngoi qua l s y mng loa th ng chuyn ng. Loa th ng c cu to tng t nh loa chnh, ch khng c cun m v khng c ni vi b khuch i. Mng loa v th ch chuyn ng da trn sng ngc sinh ra bi loa chnh. Loi thng loa ny hiu qu hn loa kn v chnh xc hn loa di. Mt s loa phn m th ng c thit k vi loa ch ng mt ny v loa th ng mt kia. Kiu thit k hai mt s tn m ra mi hng, rt thch hp trong vic ch to cc loa sau trong h thng rp ti gia. Tuy nhin, y ch l mt vi kiu thit k c bn v thng dng nht. Thc t trn th trng c v vn kiu ch to thng vi cc cu trc v cch sp xp c trng ty thuc cng ngh ca tng hng. Cc cng ngh loa khc

Cc loi loa tnh in c thit k theo kiu mng loa c p ln lt in m v dng da trn s bin i tn hiu in t. Khi c nhim in dng, n s dao ng v pha tm in tch m v ngc li. Nh th, mng loa s ti to chnh xc s dao ng m thanh. Cc loa truyn thng thng thng trn thng c gi l cc loa in ng (dynamic). Ngoi ra cn mt cng ngh ti to m thanh khc na l cc loa tnh in (electrostatic speaker). Cc loa ny lm rung ng khng kh nh mt tm mng rng, mng c kh nng dn in. Tm mng ny c treo gia hai tm vt liu dn c nh to nn mt trng in t vi mt bn cc m v mt bn cc dng. Tn hiu in t khi c p vo tm mng s thay i lin tc in cc. Khi nhim in dng, n chuyn ng v hng cc m v ngc li. Chuyn ng lin tc ny lm rung ng lp khng kh xung quanh to nn sng m. Do c trng lng rt nh nn tm mng hi p rt nhanh v chnh xc theo tng thay i nh ca tn hiu m thanh, to nn cht m rt trong v chnh xc. Tuy nhin, do bin chuyn ng khng ln nn cng ngh ny khng thch hp to cc loa siu trm. V th, loa tnh in thng c ch to lm cc loa trung hoc tweeter v c kt hp vi loa trm ci thin di m tn thp. Mt dng thc khc tng t l cc loa t phng(planar magnetic). Cc loa ny s dng mt di ribbon kim loi treo gia hai tm nam chm v hot ng tng t nh loa tnh in, ngoi tr vic dng xoay chiu lm mng loa chuyn ng trong t trng thay v trong in trng. Cng nh cc loa tnh in, loa t phng p tn tt vi cc m tn s cao, trong khi km vi cc m tn s thp. V th, chng thng c dng ch to loa tweeter. Mc d c hai kiu ang dn tr nn thng dng vi gii nghe nhc nhng loa in ng truyn thng vn l cng ngh ph hp nht tnh n thi im hin nay. Ngi ta c th tm thy dng ny khp mi ni, trong mi thit b, t loa ti ng h, TV, in thoi, my tnh, tai nghe..., a dng chng t d ch mt cng ngh n gin cng c th to nn cuc cch mng trong th gii hin i. (sohoa)

Tm hiu v loa khng dy Trong cc h thng loa khng dy, cn mt b pht (transmitter) v mt b nhn (receiver) khng dy.

Loa khng dy trong h thng HTIB. nh: Crunchgear.

Loa khng dy thng gp trong cc h thng rp ti gia gn nh HTIB (Home Theater-in-a-Box), trong , loa khng dy thng l loa surround. Trong trng hp ny, b phn trung tm c tch hp sn mt ampli u ni trc tip vi loa trc tri, trung tm, phi, cn cc tn hiu m thanh surround s c b pht pht ring ti ampli th cp. Ampli ny s chuyn cc tn hiu ny thnh tn hiu m thanh v gi ti cc loa surround khng dy thng qua dy ni trc tip. Nh vy, ni loa khng dy y c ngha cc loa surround thay v phi ni dy trc tip vo b phn trung tm (u c chnh v ampli) th ch cn ni dy vo b nhn khng dy. Nhng b nhn khng dy ny cng vn cn phi c dy ni ngun nui n hot ng. V th, vi mt h thng loa khng dy, ngi s dng ch bt c cng vic ni dy long ngong t ngun pht chnh n cc loa surround pha sau, cn cc loa ny vn phi ni n ampli th cp, hoc nu hin i hn, ch phi ni vi cm ngun trong trng hp ampli th cp tch hp ngay trong loa. Vic ph thuc vo ngun in c th khin cho vic sp xp loa khng c linh hot nh mong mun nhng d sao cng hn l ko dy t ngun pht chnh.

Mt s kt ni trong h thng hometheater c cc loa surround khng dy. nh:Hometheaterssystem.

Mt gii php mang tnh thc t hn v ang dn tr nn thng dng trong thit k h thng loa khng dy hin nay l tch hp b truyn nhn trong loa siu trm ch ng. L do l bn thn loa siu trm ch ng lun cn mt ngun nui c lp nn vic tch hp thm mt b nhn khng dy v mt ampli th cp khng lm thay i thit k cng nh khng phi l cng vic kh khn. Thit k h thng khng dy dng ny ang ngy cng tr nn thng dng, nht l cc h thng loa thanh (soundbar) do thng ch c 2 thnh phn: loa thanh chnh v loa siu trm ri. Mc d c loa thanh v loa siu trm vn cn phi c dy ni ngun c lp nhng sp t h thng tr nn d dng hn nhiu nh vic loi b c cng on ni dy t loa thanh ti loa trm cng nh bn cht linh hot ca m trm t ph thuc vo v tr c nh. V tt nhin, h thng ny ch yu cu c 2 v tr cm ngun, thun tin hn nhiu so vi cc h thng 2, 5 hay 7 loa nh cc h thng m thanh ti gia hin nay. V th, khi chun b mua mt h thng m thanh khng dy, cn nh rng "khng dy" khng ng ngha vi vic "khng cn dy", ch l nh phng thc truyn nhn khng dy gia cc loa m vic b tr phng trong mt s trng hp s hp l v d dng hn l phi chy dy khp phng. (sohoa)

Loa tnh in khc g so vi vi loa thng thng? Loa thng thng s dng nam chm in t ko/y mng loa hnh nn, loa tnh in to m thanh bng cch rung mt tm mng ln v mng, c treo gia hai tm in cc.

Loa tnh in to m thanh bng cch lm rung mt tm mng ln v mng, c treo gia hai tm in cc c nh. nh: Howstuffworks.

Thay v s dng nam chm in t, cc loa tnh in to m thanh bng cch lm rung mt tm mng ln v mng c treo gia hai tm in cc c nh. in t ngun in chnh c chy qua nhng tm in cc ny, to nn mt trng tnh in vi mt mt m v mt mt dng. Khi tn hiu m thanh (di dng cc tn hiu in t) chy qua tm mng loa, tm mng ny c i cc lin tc. Khi nhim in dng, tm mng s b ht v pha cc m ca trng tnh in, khi b nhim in m, n li b ht v cc dng. Bng cch ny, tm mng s chuyn ng ko/y lin tc gia hai cc, khin cho khng kh xung quanh b rung ng, t to ra m thanh. Do c trng lng rt nh nn n c kh nng hi p gn nh ngay tc th, k c vi nhng xung nh nht. V th c th ti to m thanh mt cch rt chi tit v chnh xc, rt thch hp cho cc m trung v m cao. Tuy nhin, do khong chuyn ng khng ln nn cc loa tnh in khng thch hp vi cc m tn s thp. c c mt b loa hon chnh, cc loa tnh in thng c kt hp vi mt loa trm ring chuyn tr cc m tn s thp. Thm vo , chng cn ngun nui ring nn vic b tr trong phng khng c linh ng bng loa thng thng. (sohoa)

Lp t loa surround khng dy "Ti c dn 5.1 vi receiver Denon AVR-2310CI, ti mun lp thm hai loa surround lp thnh h thng 7.1 nhng mun dng gii php loa khng dy". Tp ch Electronic House a ra mt trng hp t vn m ngi dng trong nc rt c th s gp phi. c gi ca Electronic House hi: "Ti c dn m thanh 5.1 vi receiver Denon AVR-2310CI. Ti mun thm hai loa surround lp thnh h thng 7.1 nhng vn l pha sau ch ngi li l khng gian m vo bp, v th khng th chy dy trn tng c. Liu c th dng gii php lp t loa khng dy trong trng hp ny khng". Chuyn gia ca tp ch ny tr li: "Thc ra, loa khng dy khng hn l s khng c mt si dy no, bi l cc loa khng dy cng cn c ngun nui, v th vn phi c dy ngun cm vo ngun in trn tng. Ri cn phi ni dy t u nhn khng dy n cc loa. Nu ch mun trnh trng hp chy dy pha tng hu th c th la chn gii php b chuyn khng dy, trong u pht cm vo u Denon, u nhn pha sau ni vo cc

loa surround. Nu mt hu khng phi l tng m l mt khng gian m, ngi lp t s gp kh khn trong vic tm cm cho u nhn khng dy pha sau ny. Thm vo , dy ni t u nhn n loa s vn phi chy trn sn nh, tr phi bn li dy cng thit k n di sn. C nhiu hng bn cc b thu nhn khng dy v hu ht u s dng sng tn s 2,4GHz. B nhn thng c tch hp sn ampli cho mt hoc 2 loa. Ampli trong h thng khng dy ny thng c cng sut nh ch khng nh cc b receiver nh Denon. Mt trong nhng b kh thng dng l KEF Wireless System ca KEF vi cng ngh nhy tn gip tn hiu truyn dn n nh v khng b nhiu bi iu kin mi trng bn ngoi. Polk cng c mt b F/X vn l mt loa n tch hp sn 4 loa ton di v mt loa trm 5,25 inch. Tuy nhin, b ny vn c thit k thay th loa surround bn ch khng nhm cho cc loa hu. Ngoi ra cng c th la chn b WEB-1 Wireless Speaker ca hng JBL. B ny gm u pht v u nhn nhng h tr hai knh ti 50W. JBL cng c nhng b loa tch hp sn u nhn nhng cng sut kh nh, ch 15W v c th s khng ph hp vi mt s nhu cu nghe nhn nht nh. Nu khng mun u t cho cc b kit khng dy, trong trng hp ny c th ngh n vic s dng loa trn. Vi cc loa ny, ngi dng vn c th chy dy nh bnh thng, li khng lo b nh hng do khng gian m pha sau gh ngi nghe. Tuy nhin, gii php ny mt thi gian v cng sc hn v cn phi ci to li phng nghe".

Hiu ng set-up ng h thng home theater Hiu mt cch n gin, h thng home theater ti gia ch cn mt mn hnh ln, mt h thng m thanh vm v vi cp ni. Nhiu ngi c th ngh mt h thng rp ht ti gia ti c chc ngn USD i hi s lp t chuyn nghip. Tuy nhin, khng phi b dn no cng nh vy. N c th rt n gin ch vi mt vi thnh phn c bn nh mn hnh, cc loa ti hin m thanh, b x l v ngun pht v cch set-up n gin, min l ngi dng hiu ng v n. Tp ch Electronic House tng hp 12 iu c bn v mt b dn xem phim ti gia cho nhng ngi mi bt u chi h thng ny.

Mt h thng home theater 5.1. nh: Caraudiosystem.

Hnh nh 1. Mn chiu cng ngh no hay kch c no l ty ngi mua, nhng quan trng l n phi ln. Ni chung, mt mn hnh t nht l 50 inch (tnh theo ng cho) l hp l, vi nhng phng b th kch thc nh hn cng khng c vn g. phn gii tt nht nn l Full HD 1080p, nhng nu cha c iu kin th 720p cng chp nhn c. Khi chun b sm mn hnh cho h thng xem phim ti gia, cn lu khong cch ngi xem. Thng thng khong cch ny bng t 2 n 3 ln rng mn hnh (theo chiu ngang thay v ng cho). 2. TV s dng trong h thng xem phim ti gia c th l Plasma, LCD, DLP hay LCoS. Cng ngh no d u c mt hay v d nhng u c

kh nng hon thnh tt nhim v ca mnh ty thuc vo s thch cng nh ti tin ch nhn. 3. Cng ngh hin th ca mn hnh ty thuc vo kh nng ti chnh ca bn. Mc ch s dng cng nh khng gian ni bn s thng thc phim nh. C rt nhiu la chn cho mi nhu cu, v th, khi xc nh c nhu cu chnh xc ca mnh, vic la chn s tr nn d dng hn. 4. Hy lu n cng ngh trnh chiu 3 chiu (3D) ang ngy tr thnh mt cng ngh thi thng, ng thi cht lng cng ngy mt ci tin. Mt mn 3D thc th c th khin dn xem phim ti gia nng tm ng cp khng thua g rp. TV 3D th h mi cn c nhng cng ngh mi gip xem ni dung 2D cng cht lng hn.

Mt h thng m thanh vm phi c t nht t 5 loa tr ln. nh:Homeaudiosystem.

m thanh 5. Mt h thng m thanh vm (surround sound) phi c t nht t 5 loa tr ln, trong , 3 loa trc c b tr bn mn hnh v t nht l hai loa sau b tr mt bn hay mt sau ca ch ngi xem. 6. H thng 3 loa trc ph trch phn ln lng m thanh ca phn hnh nh trnh chiu. Hai loa trc, thng gi l knh phi v knh tri, c t hai bn, loa trung tm thng t di hay trn mn hnh. Cc loa bn thng c gi l cc loa surround. Trn mt s h thng cao cp cn c mt s loa knh cao to trng m rng ln hn. 7. Loa trung tm ng vai tr l loa quan trng nht trong vic thit lp h thng m thanh. Loa ny ph trch phn ln lng m thanh trong mt b phim, nht l cc li thoi, to cm gic nh tt c nhng t, nhng cu trong phim c pht ra trc tip v r rng t ming ca nhng din vin vy. 8. Cc loa surround ng vai tr ti hin li m thanh mi trng xung quanh nh m thanh nn, ting ng ca mt chic t hay my bay vt qua. Loa surround gip m rng khng gian m thanh cho b phim. Tuy nhin, cc m ny thng khng phi l m chnh nn trnh ng loa qu gn hoc qu to, s khin cho cht m mt t nhin. 9. Bn c th chn nhiu kiu lp t loa surround, hoc c th ch cn hai loa t hai bn ch ngi xem. Ngoi ra, chn 3 loa vi mt loa t pha sau, ci thin thm mt cht ting ng chy vng quanh cho tht hn nh ting ca t hay on tu chy pha xa chng hn. Hay c th chn 4 loa hay nhiu hn, hon ton ty thuc vo kh nng u t ca bn. 10. Mt loa khng km phn quan trng trong h thng l loa siu trm ti to m trm gip bn nghe c nhng hiu ng nh ting n hay ting gm ca ng c. Loa siu trm ni chung c th t bt k u, gc nh, sau chu cy hay di gm bn Loa ny chnh l loa s ".1" trong cc h thng 5.1, 6.1 hay 7.1 m vn thng qung co. Nhng b m thanh cu k hn c th c ti 2 loa siu trm, to nn cc h thng 5.2 hay 6.2 11. m thanh chuyn ti loa v hnh nh hin th trn mn hnh cng lc, cn c cc thit b x l chng. c th l receiver hay ampli v cc u c ri. Mt b receiver thng tch hp sn ampli v bn khng cn phi c ampli ri na, nhng khi nhu cu cao hn, c th ngh ti vic u t nhng thit b x l c lp ri nhau. Hy tm nhng receiver c nhiu u vo HDMI (m hin chun 1.4 l mi nht) c th kt ni ti nhiu ngun thu pht. Cng nn ch ti cc tnh nng ph tr nh kh nng kt ni vi my nghe nhc c nhn, nghe radio Internet, kh nng kt ni mng hay tnh nng t cn chnh m theo phng c c mt b m thanh hp thch. 12. Hu ht mi ngi xem phim t hai ngun chnh l truyn hnh v a (DVD hoc Blu-ray). Tuy nhin, hin nay c nhiu ngun phim khc, nh t cng hay t mng Internet vi ngy mt nhiu nh cung cp ni dung trc tuyn. Hy ch ti nhng b dn rp ti gia tch

hp sn nhng tnh nng ny khng cn phi nng cp nu nhu cu xem phim nghe nhc ca bn m rng hn. (sohoa)

t loa trung tm u V tr l tng cho loa trung tm thc ra l phi gia mn hnh, tuy nhin v tr ny ch thc hin c khi dng mn chiu trong.

V tr l tng ca loa trung tm l t st ngay di hoc trn mn hnh. nh:Hifix.

Theo chuyn gia Rob Schultz ca trang web Electronichouse, ngoi v tr l tng l gia mn hnh (c v khng my kh thi vi cc h thng hometheater hin ti) th c th t loa trung tm c t ngay st pha di hoc trn ca mn hnh. V knh trung tm thng cha li thoi, do tnh c hng ca cc tn s cao (khc vi m trm khng c hng) nn tai ngi c th nhn c v tr ca cc m ny. Chnh v th, s rt v l khi m ng l t ch ny li n t ch kia. t loa trung tm ngay trn hoc di mn hnh l gn khng qu to nn s khc bit. i khi ngi ta cng c th neo cc loa tri, trung tm, phi v cc loa surround trn trn trong mt s trng hp c th. Khi thc hin, phi m bo chng c t hng thng v pha ngi nghe nhm m bo m thanh c v nh n thng t pha mn hnh v hng m khng i xung sn nh gy long. Tuy nhin, sp xp nh vy, loa phi c t cng xa v tr nghe cng tt, nu khng, tai ngi s nh v ngay c ngun pht n t trn cao. Vic b tr loa trn xt v gc cu ton th khng phi l v tr l tng, nhng t quan im thit k ni tht th vic b tr ny cng c nhng hp l nht nh. Cng cn lu rng, mt s hng m thanh ang th nghim vi cc knh trn cao, nn ngoi h thng thng thng s c thm cc loa tri v phi c t cao hn truyn thng. Cc nh sn xut tin rng vic thm cc knh cao s m rng m trng, em n mt khng gian m thanh rng ln hn hn so vi cc cch sp xp trc y. V tt nhin, nu neo cc loa tri, phi, trung tm trn tng th vic th nghim cc loa knh cao s khng cn ngha g na c. Cng c kin cho rng loa trung tm hon ton c th t trn trn nh v thc t l kiu b tr loa "tng hnh" ang dn tr nn mt xu hng mi ngy nay. Rt may l c nhiu hng loa ang p ng yu cu ny vi nhng thit k c bit chuyn lp trn trn nh hoc trong tng. Cc loa trn trc y vn khng c a chung bi ngi nghe phi hy sinh mt phn cht lng i li mt thit k ni tht p mt v sch s. Tuy nhin, khong cch gia cht lng m v b tr phng ang ngy mt thu gn nh nhng cng ngh gn loa mi chng phn m cng nh nhng loa c sn b iu hng gip m c th ti thng v tr ngi nghe. Mt vi nm trc y, hng Boston Acoustics cng th nghim m hnh lp loa trn bng cch trnh din quy trnh ti to m thanh t c cc loa ng truyn thng tri, trung tm, phi ln m t cc loa trn. Trong qu trnh trnh din, hng ny chuyn i gia hai h thng loa v n cui bui hi khn gi liu h c nhn thy s khc bit cng nh thi im h chuyn ngun pht hay khng. Kt qu khng mt ai nhn ra c thi im ny. iu trn cho thy cht lng ca mt h thng loa gn trn hin cng tin trin nh th no. (sohoa)

Tm hiu v loa tnh in Loa tnh in s dng mt tm mng mng lm chuyn ng khng kh sinh ra m thanh nhng hot ng trn nguyn tc tng tc tnh in. Tng t nh cc loa ribbon, cc loa tnh in s dng mt tm mng mng lm chuyn ng khng kh sinh ra m thanh. Nhng khng nh cc loa in ng v loa ribbon vn hot ng da trn bin thin in t trng, ngha l s tng tc t trng do dng in gy nn, loa tnh in hot ng trn c s nguyn tc tng tc tnh in hon ton khc. Ni ti loa tnh in, khng th khng nhc ti phin bn Quad ESL-57 do Peter Walker pht trin vo nm 1957. Phin bn ny thc s l mt cuc cch mng trong vic to ra cc loa trong sut v thit k ny hin vn c duy tr ti nay. Rt nhiu th h audiophile khi nng cp trnh nghe u t nhiu tri qua nghe phin bn ESL-57 ny. V rt nhiu nh thit k loa hin i sau ny vn gi cho mnh mt i ESL-57 lm loa tham chiu cho sn phm mi. Mc d khng h tr di m trm qu thp, cng sut khng ln, khong im ngt li hn ch, nhng khi th hin nhc trong ng tm di m ca mnh, cht m ca ESL-57 ch c th ni l tuyt ho.

Cu trc loa tnh in.

Trong cc loa tnh in (thng c gi l cc loa ESL, vit tt ca t ElectroStatic Loudspeaker), mng loa thng c lm bng vt liu Mylar mng v trong sut, c cng gia hai cc stato nh hnh trn. Mng ny c np mt dng in th rt cao. Khi tn hiu m thanh tc ng vo stato s to nn trng tnh in xung quanh stato bin thin theo mc ca tn hiu m thanh . bin thin tnh in ny tng tc vi trng tnh in c nh ca mng loa, t ko hoc y mng chuyn ng, sinh ra m thanh. Trong hnh l mt h thng loa tnh in lai, nn ngoi mt stato ng vai tr ko, mt stato ng vao tr y mng loa, cn c thm mt loa trm in ng kt hp, chuyn x l cc tn s thp. in p trong loa tnh in thng rt cao. in th phn cc p trn mng c th ln ti 10.000 Vn (10kV). Thm vo , tn hiu m thanh cng c tng bc t khong vi chc Vn ti khong vi nghn Vn nh mt b chuyn i bn trong cc loa tnh in. Cc mc in p cao ny chnh l sn sinh ra cc trng tnh in xung quanh mng loa v cc stato. trnh hin tng nh la in ln nhau gia cc thnh phn (hay cn gi l cung la in arcing), cc stato thng c c ph mt lp vt liu cch in. Mc d vy, nu mt loa tnh in hot ng qu cng sut th trng tnh in s ht cc ht in t t do t khng kh, lm n b i-n ha; qu trnh ny s to nn mi trng dn gy nn hin tng nh la in. Nu mng chuyn ng mnh qu, nh l khi m lng qu to, chng s b y gn vi cc stato v hin tng ny cng s gy ra nh la in. Hin tng nh la in c th ph hy cc tm tnh in do qu trnh ny s c thng cc l nh trn mng. Hin tng s cng ti t hn nu mi trng t loa m thp, bi khi , hi m lm cho lp khng kh gia cc stato tr nn d dn in hn. Trong loa tnh in, cc tm tnh in thng c chia nh nhm gim thiu hiu ng cng hng mng loa. Mt s cn c un cong gim thiu hiu ng lobing (hin tng pht m khng u) ti cc tn s cao. Hin tng lobing thng xy ra khi bc sng m nh hn so vi mng loa. Lobing thng to ra bi mo tn s cao ca loa tnh in m nh sng lp tp ch Stereophile J. Gordon Holt gi l hiu ng mnh dc (vertical venetian-blind effect), theo cn bng tng m sc b thay i nhanh chng v lin tc mi khi ngi nghe dch

chuyn u sang bn ny hay sang bn kia. Mt trong nhng c trng ca loa tnh in l cc tm tnh in c trng lng v cng nh. Khng ging nh loa ribbon vi mng loa mang dng tn hiu m thanh, cc mng tnh in nht thit phi nh vy. Chnh v th, chng c th rt mng, kch thc thng thng cn mng hn 0,001 inch. Vi trng lng siu nh ny, chng s rung v dng rt nhanh chng, nng tc hi p vi tn hiu gn nh tc thi. Tng t loa ribbon, loa tnh in cng khng cn ti thng loa v th khng lo b gim cht lng m thanh do thng. Cng vi c tnh l dng loa pht lng cc vi tm mng c treo trong mt khung m, loa tnh in pht m vi cng sut nh nhau c mt trc ln mt sau.

Loa tnh in cn c t ng v tr, xa tng hu th mi pht huy li th. nh:Instablogsimage.

Do kt cu tng t vi loa ribbon nn ngoi mt li th, loa tnh in cng c nhng nhc im nht nh. Do bn cht l cc pht m lng cc nn vic tm c mt v tr ti u t trong phng khng phi l iu n gin. Chng cn c t ng v tr nht nh, nht l phi xa tng hu mi c th pht huy li th trng m rng ca mnh. Loa tnh in thng khng nhy, tr khng thp, v th thng i hi ampli cng sut ln. Ni chung, khi cp n cng ngh loa tnh in, ngi ta khng trng ch l cng sut cao, di m ln, m trm su m cc loa ny ni ting ch yu nh vo trong, mm mi, hi p tc thi, chi tit cng nh gn kt cht ch ca m thanh. Chnh do nhng u v nhc nh vy m loa tnh in thng c b sung thm mt loa trm hoc mt siu trm in ng c lp tng cng cht m ti tn s thp, t ci thin ton b di m. Vi thit k kinh in gm loa trm in ng trong thng loa ring kt hp vi cc tm tnh in, mt s phin bn c th t ti cht m ng cp do tn dng c li th ln nht ca c hai cng ngh. Tuy nhin, cc loa lai kiu ny cng d b hin tng ngt qung khi chuyn i gia di m trm do loa trm in ng ph trch vi m trung cao do loa tnh in ph trch. Cc bn nhc vi tit tu piano lin tc t thp n cao cng nh cc a jazz acoustic l nhng a thuc tt ngi nghe c th th tnh nng th hin lin tc gia cc di tn ca nhng loa lai kiu ny. Mt trong nhng li th ln ca loa ribbon ton di hay loa tnh in ton di l chng khng c tn s giao ct do ton b tn hiu m u c th hin qua chuyn ng ca mt mng loa. iu ny trnh c hin tng ngt qung do mi di tn s c pht bi mi loa khc nhau trn cc loa in ng. Thm vo , khng c b iu khin tn s giao ct vi cc in tr, t in hay cun cm m sc trn cc loa ny trong, mm mi v chnh xc hn. Thm ch ngay c vi cc loa lai gia tnh in v in ng, tn s ct cng thng mc rt thp (thng di 800Hz), v th gn nh l khng c s ngt qung khi chuyn i gia cc loa trn hu nh ton b di m. Cui cng, do loa tnh in v loa ribbon hot ng da trn s chuyn ng ca ton b tm mng ln thay v ch mt phn nh din tch tip xc gia mng loa v cun m trn loa in ng, nn cc loa ny cng hn ch ti a hin tng v ting (breakup) nh i vi cc loa in ng. (sohoa)

Tm hiu v loa di bng Mt trong cc cng ngh loa khng km thng dng khc l cng ngh t phng (planar magnetic), hay cn gi l cc loa di bng (ribbon). Mc d nhiu ngi hay dng ln t ribbon (di bng) vi t phng (planar magnetic), nhng v mt k thut, loa ribbon thc ra l mt nhnh con ca th loi loa t phng. Thay v s dng nn loa ni vi cun m treo trong t trng, loa ribbon s dng mt di vt liu (thng l nhm) lm thnh mng loa treo gia cc bc v cc nam ca hai nam chm.

Cu trc loa di bng.

Di ny thng c gp np tng vng chc. Tn hiu m thanh i qua di bng c kh nng dn in to nn mt t trng xung quanh. T trng ny tng tc vi t trng vnh cu khin cho di bng chuyn ng ra/vo to nn m thanh. y, di bng ng vai tr va l cun m va l mng loa. Trong hu ht cng ngh bin thin t phng, mt mng phng hoc hi cong c iu khin bi mt cht dn in t. Cht ny c gn vo mt sau ca mng, tng t nh cun m loa in ng nhng y c tri di theo chiu ca di bng. Trong hu ht thit k, mng loa thng l mt tm nha v c ph mt lp dn in trn b mt. Phn ph lp cht dn ny to nn chuyn ng ca mng loa d ch chim mt phn ca mng loa. Cc loa ny thng c gi l loa bn di (quasi-ribbon). Hai hnh di th hin s khc nhau gia loa ribbon v quasi-ribbon.

Loa bn di (quasi-ribbon).

Loa ribbon.

Cc loa phng c coi l loa ribbon thc s nu nh mng loa l cht dn v tn hiu m thanh i qua n, trong khi cc loa quasi-ribbon, tn hiu m thanh i qua cht dn gn vo mng loa. Cc loa ribbon nh trong hai hnh trn thng c gi l loa ngun pht di (line-source) so vi cc loa in ng l ngun pht im (point-source). Thm vo , khong tn m ca loa ribbon thay i theo tn s. Vi tn s thp, nu di ca di bng ngn so vi di ca sng m, chng s ng vai tr l ngun pht im v to ra khong tn m hnh cu xung quanh di, tng t nh cc loa trm in ng. Khi tn s tng v di sng m tin dn ti di di bng, khong tn m thu hp dn thnh mt dng hnh tr xung quanh. Do , vi cc tn s rt cao, di bng s tn m theo chiu ngang tt hn chiu dc. y l mt li th ln ca loa ribbon trong cc phng nghe chuyn dng, bi s ngi nghe c th nghe c m sc trc tip t loa nhiu hn thay v nghe cc m di t trn hay tng, t m pht n tai ngi nghe chun xc hn, th hin tt hn nhng c trng m hng ca mt dn nhc nh th ngi nghe ang trc tip hin trng. Mt li th khc ca loa ribbon so vi loa in ng l trng lng ca di bng rt nh. Thay v s dng mng loa, nn loa, ri cun m, li m to nn chuyn ng khng kh, vt duy nht chuyn ng trong loa ribbon ch n gin l mt di nhm rt mng. Nh li th ny, cc loa tweeter ribbon c trng lng d ch bng nhng c th to ra vng tn m rng hn 10 ln so vi mng loa tweeter dome. Do nh nn mng loa ribbon hi p cc tn hiu m ngn rt nhanh trong khi li c th dng chuyn ng gn nh tc thi khi tn hiu m tt. V th cc loa ribbon c th truyn ti m thanh chi tit v trung thc hn.

M hnh pht m ca loa nguyn

Cc loa ribbon thng c gn ln mt khung phng v h c th pht m thanh ra c mt trc v sau. Mt loa c th pht m ra c trc v sau thng c gi l loa lng cc (dipole), ngha l c hai cc pht m. Hnh trn th hin m hnh pht m ca loa ngun pht im (bn tri) v loa lng cc (bn phi). Loa ribbon cng c li th kh quan trng so vi loa in ng l do khng c hp hay thng nn cht lng m thanh khng b tc ng bi cng hng thng loa, cc loa ribbon d dng t c m sc trong v tht hn.

y l minh ha v mt loa quasi-ribbon ton di.

Trn l minh ha v mt loa quasi-ribbon ton di. Tm mnh ln cho thy h thng loa c th biu th m trm tt, bi l khi kch c trung bnh ca tm mnh bng khong na di sng m, s trit tiu sng trc v sau s lm gim cng sut m trm. V th, loa c tm mnh cng ln th m trm cng su. c trng ca cc loa ribbon l kh nng ti to cc m sc trong v ngn rt n tng, nh ting bng ca n guitar hay ting g ca mt nhc c. Cc m ny loa ribbon s ngn ln v kt thc rt nhanh, rt mnh m v tc thi trong khi khng b kh hay qu chi, nh th c nghe t chnh cc nhc c trc tip vy. Thm vo , m thanh nghe rt m, rt r v trong, vn l cc c tnh kh t c vi cc loa in ng (tt nhin cng cn ty thuc vo cht lng ca cc microphone ribbon na). Cui cng, bn cht lng cc t nhin ca loa ribbon to nn mt cm gic m trng rng ln v su, to cm gic nh th thu c c khng gian m nhc ti hin trng d cng c nhng ngi cho n l gi to.

Loa ribbon thng c nhy thp. nh: Hometheaterhifi.

Mc d c cht lng m thanh kh tuyt ho nhng loa ribbon cng c vi nhc im nht nh. Th nht, loa c nhy kh thp, v th i hi loa cng sut tt mi ko c. Th hai, loa ribbon r rng c tr khng rt thp, thng ch dao ng trong khong 1. V th hu ht loa ribbon c tr khng kt hp vi b chuyn i (transformer) ti tn s ct nhm to mt tr khng cao hn i vi ampli cng sut. Thit k b chuyn i v th rt quan trng sao cho nh hng ti cht lng m thanh c gim thiu nht. Thm vo , v mt thc tin, cc loa ribbon kh t trong phng hn. Ch mt s thay i nh v v tr cng c th dn ti thay i cht lng m thanh do kiu pht m lng cc trn. Kiu thit k pht m lng cc i hi cc loa ribbon ny phi c t xa khi tng hu c cht m t nhin hn. Nu cc loa ribbon c chiu cao ngang tai ngi th s rt d to ra cc m treble khc nhau r rt nu nh ngi nghe ngi hi cao hoc hi thp d ch vi centimet. l v cc loa ribbon c khong tn m dc kh nh, ngha l ch c rt t m thanh c pht trn v di di bng cc tn s cao. V th, nu ngi nghe ngi qu cao hoc va ng va nghe nhc, s ch nghe c rt t m treble. Tuy nhin, mt s loa ribbon c th chnh nghing, cho php ngi nghe iu chnh cn bng trp nghe mt s cao nht nh. Cc loa ribbon cng c mt tn s cng hng nht nh m nu ti hn s sinh ra cc m chi tai t cc l nhm. Do chng thng c dng vi nhng gii hn di tn c nh. Mt yu t cng nh hng khng nh n cht lng ca loa ribbon l cng ca cc di bng. cng ny vn c cn chnh ngay ti nh my sn xut. Nu b cng qu mc, chng s sinh ra m yu hn, nhng nu qu chng, cc di ny li sinh ra hin tng mo m nh th b v ting. iu ny tng t nh i vi n piano, nu b chng dy cc m s d b v v mo. Vic tng nhit phng t ngt cng c th khin cho cc di bng ny gim cng v gy mo ting. Nu bt u thy hin tng trn, ngi nghe cn lin h ngay vi nh sn xut h c th cn chnh li. Hin nay, cc nh sn xut kt hp c hai loa in ng v loa ribbon tn dng li th ca c hai cng ngh ny. Cc loa ny thng gi l cc loa lai, s dng loa trm in ng trong mt thng ring, cn cc m trung v cao th dng loa ribbon. Cng ngh lai mang n nhiu li th cho loa ribbon do h thp c gi thnh (bi cc loa ribbon trm thng to v t tin). Hin thch thc ln nht ca loa lai l lm sao t c s chuyn tng m i gia di trm ca in ng vi di cao ca ribbon m m thanh nghe vn lin mch, khng c mt cht ngt qung d ch nh nht no. (sohoa)

Tm hiu v loa in ng Loa in ng l cng ngh loa thng dng nht hin nay nh di m rng, cng sut ln, nhy cao, thit k n gin v rt chc chn. T hng nm nay ngi ta b cng nghin cu nhng c ch bin tn hiu in thnh chuyn ng khng kh to nn m thanh. Tuy nhin, tu trung li, c ba phng php to m thanh c bn t ra p ng tt vai tr ca mnh mt cch hiu qu c v mt k thut cng nh thng mi ha. l loa in ng, loa mnh ribbon v loa mnh tnh in. Cc loa in ng thng c gi l loa hp do cc thit b c t ton b vo mt dng thng hay hp loa, trong khi cc loa ribbon v loa tnh in thng c gi l loa phng bi chng thng thng c ch to di dng mt tm mn phng v mng. Tp ch nghe nhn AVGuide gii thiu s lc v ba loi loa trn cng nh cch thc hot ng ca chng. Kin thc trong bi c trch t

cun sch Cm nang v m thanh cht lng cao (The Complete Guide to High-End Audio) ca tc gi Robert Harley.

S cu to loa in ng. nh: AVguide.

Loa in ng l cng ngh loa thng dng nht hin nay vi c trng l cc mng loa hnh nn. S d cc loa ny tr nn ph bin bi c rt nhiu li th: di m rng, cng sut ln, nhy cao, thit k tng i n gin v rt chc chn. Mt h thng loa in ng thng gm nhiu loa vi cc kch thc khc nhau. Cc tn s thp thng c ti to t cc loa trm. Tn s cao c ph trch bi loa tp (hay cn gi l tweeter). Mt s h thng cn s dng thm loa trung, dng ti to tn s m thanh nm gia di tn cao v di tn thp. Mc d c thit k khc nhau, nhng cc loa ny u hot ng da trn cng mt nguyn tc. M hnh hot ng ny c n gin ha nh sau: Dng in t ampli chy qua cun m ca loa to nn mt t trng dao ng xung quanh cun m, rng ra hay hp li theo mt tn s ng bng tn s tn hiu m thanh. Cun m thng thng lun c gi c nh nh t trng vnh cu ca cun nam chm loa. T trng vnh cu tng tc vi t trng do dng in chy qua cun m, v s y cun m tnh tin ra hoc vo. Do cun m c gn vi mng loa nn s tng tc t trng ny cng khin cho mng loa chuyn ng ra/vo, t to ra m thanh. Gii thch mt cch k thut hn th cun m l cun dy qun vng quanh mt trc mng gi l li cun m (voice-coil former). Li ny c gn vi mt mng loa hnh nn (cone) hay hnh vm (dome). Dng in t ampli s chy qua cun m c neo c nh trong t trng vnh cu (c to ra bi dng t trng tng tc gia hai nam chm vnh cu) trong c loa. Theo quy tc bn tay phi, dng in xoay chiu chy qua cun m s to ra lc t trng chuyn ng dc theo trc ca cun m. S tng tc gia trng bin thin ca cun m v t trng c nh to nn mt lc hng trc y cun m ra hoc vo, ko theo l chuyn ng ca mng loa. Tn hiu m thanh cng nhanh, mng loa chuyn ng cng nhanh, dn n tn s m c pht ra cng cao. Chnh do cu to ny m cc loa in ng cn c gi l cc loa cun dy ng (moving-coil drivers). Ngoi cc thnh phn trn, loa in ng cn c mt s thnh phn khc nh mng nhn (spider) dng gi cho cun m duy tr v tr khi cun ny chuyn ng ra/vo; khung cho loa (basket hoc frame), thng c lm bng kim loi c hoc hn, l ni c nh ton b thnh phn ca loa (trong khung c thng c ch to cho cc loa cao cp, t tin, cn khung hn thng cho nhng phin bn bnh dn hn). Bao ph b ngoi ca khung v mng loa l mt vin, thng bng cht liu cao su tng hp, gi l surround. Vin ny gi cho mng nn loa c gi cht vo khung trong khi vn rung theo tng chuyn ng ca cun m. Khong khng ti a cho mng nn loa chuyn ng ra/vo gi l khong lch (excursion).

Loa in ng ph bin bi c rt nhiu li th: di m rng, cng sut ln, nhy cao, thit k tng i n gin v rt chc chn.

nh: Nganu. Cc vt liu dng ch to mng loa nn c th l giy, giy ph cc cht ha cng, cc loi nha tng hp nh polypropylene, cng c th l kim loi (nh titanium), cc vt liu tng hp mi nh si cc-bon, si Kevlar (c dng trong o gip chng n) hay cc vt liu tng hp chuyn bit khc. Nh thit k loa c th chn mt loi vt liu hoc pha trn nhiu loi vt liu vi nhau sao cho chuyn ng ca mng loa c dn hng hon ho, ch tnh tin mt chiu nh kiu chuyn ng pit-tng thay v b v ting (breakup) do chuyn ng theo cc hng khc nhau. Hin tng breakup xy ra do mng loa nn gn vo cun m ch vi din tch nh hp, v th khi cun m chuyn ng, mng loa lun c xu hng dao ng a chiu gy nn hin tng mo m. Thm vo , ngoi yu t cng, mng loa cn i hi phi nh. Mng cng nh th loa cng nhy vi cc tn hiu v cng dng nhanh hn khi tn hiu tt. Mng loa rng v li c khi lng nng hn s khng th chuyn ng nhanh v nhy kp vi tn s dao ng, ng thi khi dao ng ri m tn hiu th mng loa vn chuyn ng theo qun tnh, to nn hin tng cng hng. V th, thit k mt mng loa va cng m bo hng chuyn ng, hn ch ti a hin tng breakup, va mm nhy vi chuyn ng ca cun m l mt nhn t v cng quan trng. Do cc loa in ng n mt tn s nht nh no s xy ra hin tng breakup nn cc nh sn xut thng ch to p tn ca loa lun thp hn im gy nn hin tng breakup. V d, nu mt cht liu cu to loa trm xy ra hin tng breakup di tn 4kHz th cc nh sn xut s thit k sao cho loa ny ch hot ng n di tn 2kHz m thi.

V d v mt dome loa tp (tweeter). nh: Techpower.

Cc loa tp (tweeter) hot ng cng vi nguyn tc tng t nhng thng s dng mt loa vm kch c khong mt inch thay v mng nn. Vt liu ch to loa vm ny thng gm c nha, si dt ph cao su, titanium, nhm hoc hp kim nhm hay thm ch l nhm trng vng. Xu hng gn y l ch to vm loa tweeter bng cc vt liu cao cp hn nh beryllium hay thm ch l kim cng trn nhng phin bn xa x ca cc hng danh ting. Khng ging nh loa dng mng nn (cone) to m thanh theo c ch chuyn ng phn trung tm ca mng loa, cc loa dome to m trn c ch chuyn ng phn vnh ngoi. Hu ht cc dome tweeter u s dng mt cht lng nhit thp c tn Ferrofluid nhm gii nhit cho cun m ca loa tweeter. Hin nay, cc loa tweeter cht lng cao t ti di tn 25kHz, vt ra ngoi m thanh nghe c ca tai

ngi. Loa trung v c bn c cu to ging nh m hnh loa trm nhng kch thc nh hn. Hu ht chng u l dng mng nn, nhng c bit c nhng loa cng c thit k dng vm. (sohoa)

Tm hiu v loa in ng Loa in ng l cng ngh loa thng dng nht hin nay nh di m rng, cng sut ln, nhy cao, thit k n gin v rt chc chn. T hng nm nay ngi ta b cng nghin cu nhng c ch bin tn hiu in thnh chuyn ng khng kh to nn m thanh. Tuy nhin, tu trung li, c ba phng php to m thanh c bn t ra p ng tt vai tr ca mnh mt cch hiu qu c v mt k thut cng nh thng mi ha. l loa in ng, loa mnh ribbon v loa mnh tnh in. Cc loa in ng thng c gi l loa hp do cc thit b c t ton b vo mt dng thng hay hp loa, trong khi cc loa ribbon v loa tnh in thng c gi l loa phng bi chng thng thng c ch to di dng mt tm mn phng v mng. Tp ch nghe nhn AVGuide gii thiu s lc v ba loi loa trn cng nh cch thc hot ng ca chng. Kin thc trong bi c trch t cun sch Cm nang v m thanh cht lng cao (The Complete Guide to High-End Audio) ca tc gi Robert Harley.

S cu to loa in ng. nh: AVguide.

Loa in ng l cng ngh loa thng dng nht hin nay vi c trng l cc mng loa hnh nn. S d cc loa ny tr nn ph bin bi c rt nhiu li th: di m rng, cng sut ln, nhy cao, thit k tng i n gin v rt chc chn. Mt h thng loa in ng thng gm nhiu loa vi cc kch thc khc nhau. Cc tn s thp thng c ti to t cc loa trm. Tn s cao c ph trch bi loa tp (hay cn gi l tweeter). Mt s h thng cn s dng thm loa trung, dng ti to tn s m thanh nm gia di tn cao v di tn thp. Mc d c thit k khc nhau, nhng cc loa ny u hot ng da trn cng mt nguyn tc. M hnh hot ng ny c n gin ha nh sau: Dng in t ampli chy qua cun m ca loa to nn mt t trng dao ng xung quanh cun m, rng ra hay hp li theo mt tn s ng bng tn s tn hiu m thanh. Cun m thng thng lun c gi c nh nh t trng vnh cu ca cun nam chm loa. T trng vnh cu tng tc vi t trng do dng in chy qua cun m, v s y cun m tnh tin ra hoc vo. Do cun m c gn vi

mng loa nn s tng tc t trng ny cng khin cho mng loa chuyn ng ra/vo, t to ra m thanh. Gii thch mt cch k thut hn th cun m l cun dy qun vng quanh mt trc mng gi l li cun m (voice-coil former). Li ny c gn vi mt mng loa hnh nn (cone) hay hnh vm (dome). Dng in t ampli s chy qua cun m c neo c nh trong t trng vnh cu (c to ra bi dng t trng tng tc gia hai nam chm vnh cu) trong c loa. Theo quy tc bn tay phi, dng in xoay chiu chy qua cun m s to ra lc t trng chuyn ng dc theo trc ca cun m. S tng tc gia trng bin thin ca cun m v t trng c nh to nn mt lc hng trc y cun m ra hoc vo, ko theo l chuyn ng ca mng loa. Tn hiu m thanh cng nhanh, mng loa chuyn ng cng nhanh, dn n tn s m c pht ra cng cao. Chnh do cu to ny m cc loa in ng cn c gi l cc loa cun dy ng (moving-coil drivers). Ngoi cc thnh phn trn, loa in ng cn c mt s thnh phn khc nh mng nhn (spider) dng gi cho cun m duy tr v tr khi cun ny chuyn ng ra/vo; khung cho loa (basket hoc frame), thng c lm bng kim loi c hoc hn, l ni c nh ton b thnh phn ca loa (trong khung c thng c ch to cho cc loa cao cp, t tin, cn khung hn thng cho nhng phin bn bnh dn hn). Bao ph b ngoi ca khung v mng loa l mt vin, thng bng cht liu cao su tng hp, gi l surround. Vin ny gi cho mng nn loa c gi cht vo khung trong khi vn rung theo tng chuyn ng ca cun m. Khong khng ti a cho mng nn loa chuyn ng ra/vo gi l khong lch (excursion).

Loa in ng ph bin bi c rt nhiu li th: di m rng, cng sut ln, nhy cao, thit k tng i n gin v rt chc chn.

nh: Nganu. Cc vt liu dng ch to mng loa nn c th l giy, giy ph cc cht ha cng, cc loi nha tng hp nh polypropylene, cng c th l kim loi (nh titanium), cc vt liu tng hp mi nh si cc-bon, si Kevlar (c dng trong o gip chng n) hay cc vt liu tng hp chuyn bit khc. Nh thit k loa c th chn mt loi vt liu hoc pha trn nhiu loi vt liu vi nhau sao cho chuyn ng ca mng loa c dn hng hon ho, ch tnh tin mt chiu nh kiu chuyn ng pit-tng thay v b v ting (breakup) do chuyn ng theo cc hng khc nhau. Hin tng breakup xy ra do mng loa nn gn vo cun m ch vi din tch nh hp, v th khi cun m chuyn ng, mng loa lun c xu hng dao ng a chiu gy nn hin tng mo m. Thm vo , ngoi yu t cng, mng loa cn i hi phi nh. Mng cng nh th loa cng nhy vi cc tn hiu v cng dng nhanh hn khi tn hiu tt. Mng loa rng v li c khi lng nng hn s khng th chuyn ng nhanh v nhy kp vi tn s dao ng, ng thi khi dao ng ri m tn hiu th mng loa vn chuyn ng theo qun tnh, to nn hin tng cng hng. V th, thit k mt mng loa va cng m bo hng chuyn ng, hn ch ti a hin tng breakup, va mm nhy vi chuyn ng ca cun m l mt nhn t v cng quan trng. Do cc loa in ng n mt tn s nht nh no s xy ra hin tng breakup nn cc nh sn xut thng ch to p tn ca loa lun thp hn im gy nn hin tng breakup. V d, nu mt cht liu cu to loa trm xy ra hin tng breakup di tn 4kHz th cc nh sn xut s thit k sao cho loa ny ch hot ng n di tn 2kHz m thi.

V d v mt dome loa tp (tweeter). nh: Techpower.

Cc loa tp (tweeter) hot ng cng vi nguyn tc tng t nhng thng s dng mt loa vm kch c khong mt inch thay v mng nn. Vt liu ch to loa vm ny thng gm c nha, si dt ph cao su, titanium, nhm hoc hp kim nhm hay thm ch l nhm trng vng. Xu hng gn y l ch to vm loa tweeter bng cc vt liu cao cp hn nh beryllium hay thm ch l kim cng trn nhng phin bn xa x ca cc hng danh ting. Khng ging nh loa dng mng nn (cone) to m thanh theo c ch chuyn ng phn trung tm ca mng loa, cc loa dome to m trn c ch chuyn ng phn vnh ngoi. Hu ht cc dome tweeter u s dng mt cht lng nhit thp c tn Ferrofluid nhm gii nhit cho cun m ca loa tweeter. Hin nay, cc loa tweeter cht lng cao t ti di tn 25kHz, vt ra ngoi m thanh nghe c ca tai ngi. Loa trung v c bn c cu to ging nh m hnh loa trm nhng kch thc nh hn. Hu ht chng u l dng mng nn, nhng c bit c nhng loa cng c thit k dng vm. (sohoa)