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Choi loa toan dai

Doi voi mot so nguoi choi audio, nhung thiet bi am thanh co cach day ca the ky nhu dau dia than, ampli den dien tu 3 cuc (single-end triod-SET), loa dong truc hay toan dai... lai chinh la he thong giup ho den voi niem dam me am nhac mot cach don gian nhat.

Khac voi loa nhieu dai, su dung 2 hoac 3 loa con trong mot thung de phat ra cac dai am thanh hoac loa dong truc duoc thiet ke co mot loa treble nam trong long loa trung tram, loa toan dai su dung duy nhat mot loa con nham the hien toan bo cac dai am thanh. Vi chi co mot loa duy nhat nen loa toan dai khong can su dung mach phan tan, tin hieu dien di thang tu ampli toi loa. Day co le la mot trong nhung dac diem duy nhat chi co o loa toan dai.

Loa Lowther dong thung kieu Mauhorn.

Loa Lowther dong thung kieu Mauhorn.

Ve cau tao, loa toan dai cung khong khac may loa dien dong thong thuong. Dieu khac biet de nhan biet nhat la loa toan dai thuong co them mot non loa phu, nho hon nam ben trong mang loa chinh nham muc dich tang cuong kha nang the hien tan so cao.

Cung giong nhu hau het cac loai mang loa khac, mang loa toan dai co the lam bang giay, nhua, soi tong hop hoac bang kim loai (chu yeu la nhom). Tuy nhien, pho bien nhat van la mang loa lam bang giay. Dac biet, nhung hang san xuat loa toan dai rat noi tieng nhu Lowther (Anh), Foster (Nhat) su dung nhung loai giay rat nhe, duoc che tao dac biet de lam mang loa. Thay vi dung ky thuat dap mang thong thuong, mang loa Lowther duoc cat va dan tu giay cuon cuc nhe. Trong nhung series loa gan day, hang Foster dung loai giay lam tu vat lieu la soi cua than cay chuoi de che tao mang loa. Vat lieu nay giup cho mang loa rat nhe nhung lai co do on dinh be mat tot.

Mot dac diem cua loa toan dai chat luong cao la nam cham rat lon va manh. Nam cham cua loa Lowther co tu luc len toi 20 nghin gauss, gap doi cac loa thong thuong. Nhung dac tinh nay doi hoi ky thuat che tao phuc tap va chi phi san xuat lon, kho co the ap dung cho dong loa pho thong. Co le vi the so luong cac hang lam loa toan dai khang dinh duoc ten tuoi tren the gioi cung khong nhieu, co the ke den Lowther, Goodman, Jordan (Anh), PHY-HP (Phap), Telefunken (Duc), JBL (My), Fostex, Diaton (Nhat)...

Loa Coral Flat-10MKII.
Loa Coral Flat-10MKII.

Tuy nhien ngay nay chi con rat it hang tiep tuc san xuat loa toan dai. Tren thi truong hien nay, Lowther va Foster la hai nha san xuat loa toan dai duoc dan choi audio biet den nhieu nhat. Hai hang nay hien dang san xuat rat nhieu dong loa toan dai voi kich co va thiet ke khac nhau. Trong khi hang Lowther noi tieng voi cac dong loa PM/EX cao cap (PM6A/PM6C/EX3...) thi Fostex lai duoc biet den voi nhung series loa FE voi gia ca mem hon (FE206E, FE208EZ...).

Co nhieu kieu thung cho loa toan dai voi nhung dac diem khac nhau. Kieu thung ho (Open Baffle Enclosurer): kieu thung nay kho co the tai tao tieng tram o tan so thap, dac biet voi loa toan dai. Chi co mot so it loa doi co cua PHY-HY va Altec su dung kieu thung nay.

Kieu thung phan hoi tieng tram (Bass Reflex Enclosurer): day la kieu thung pho bien nhat, thiet ke don gian, kich thuoc vua phai, no giup lam tang tieng bass nho che do phan xa am tram trong thung loa co lo thong hoi. Cac doi loa toan dai nhu Goodman 80s, Diatone 610, Fostex 207E, Jordan JX... duoc thiet ke cho kieu thung nay.

Fostex FE-208.

Fostex FE-208.

Kieu thung Ken sau (Back-Loaded Horn Enclosure -BLH) duoc thiet ke theo nguyen ly cua loa ken nham muc dich nang do nhay va kha nang tai tao am tram cua loa toan dai. Do tan so cang thap thi buoc song cang dai nen thung loa Ken sau thuong co kich thuoc kha lon de dam bao chieu dai cua ken. Vi kich thuoc lon, thiet ke va gia cong rat phuc tap, gia thanh lai cao nen kieu thung Ken sau it duoc cac hang ap dung cho cac model thuong mai. Tuy nhien, day lai la kieu thung ma dan choi audio ua chuong. Thay vi mua san cua hang, ho thuong tu dong lay theo thiet ke de giam chi phi va thoa man thu vui cua minh. Kieu thung Ken sau duoc hang Lowther ap dung cho hau het cac doi loa toan dai cua minh, trong do phai ke den mot so thung loa rat noi tieng nhu Acousta, TP1. Mot so doi loa toan dai cua Fostex nhu FE206E, FE208EZ cung duoc thiet ke cho kieu thung nay. Ngoai ra con co mot so kieu loa toan dai khac nhu TQWT (Tapered Quater Wavelength Transmission Line Speaker), Ken truoc (Front Horn)...

Moi kieu thung loa toan dai co nhung uu nhuoc diem khac nhau: loa nho gon, chi phi thap thi thuong bi han che o tieng tram va do nhay. Nhung loa to, dac biet la loa ken thi khac phuc duoc nhuoc diem tren nhung lai chiem dien tich, kho gia cong va chi phi san xuat cao.

(Con tiep)

(Theo Nghe Nhin)