Heavy Metal

PA RT 7

E q u a l i z a t i o n , Pa r t 1
B Y A L E X CA S E

Th e l at es t in s t al l men t in o u r s er ies f o r t h e n o v ic e is al l ab o u t t o n e s h apin g an d h o w t o d eal wit h it .
Th e E q u a lize r. You may we ll won d e r : wh a t soun d s in a st ud io ne e d to b e m a d e e q u a l? E qu a l to wh at ? A m ore d e s c r i p t ive te r m for e qu a lize r would b e sp e ct ra l mod ifie r, or fre q u e n cy-spe cific a mp litu d e ad j u ste r. Th e n a ga in , some t ime s a ve ry sim ple t er m will do—eve n some t h ing a s m un d a ne a s t on e con t ro l s ,l i ke “ Ba s s ” a n d “ Treb l e ” o r “ L ow ” an d “ H i g h .” Th e a u d io j ob of a n e q u alize r is t o ch a n ge t h e fre q u e ncy con t e nt of a n a ud io sign al. If t he a udio sign a l is du ll, l a ck in g h igh fre q u e n cy sp a rk l e , th e e qu a lize r is th e t ool u sed t o fix th is—p rovid e d th a t th e re is som e high fre q u e n cy con t e n t in t h e sign a l in th e first pla ce t h a t t h e e q u a l i ze r ca n b rin g ou t . If t h e sou n d is p ain fu lly b righ t, h a r s h ly assa u lt in g ou r e a rs wit h too mu ch h igh fre q u e ncy s i zzl e , t h e e q u alize r aga in offe rs t h e solut ion , t his t im e by re d u cin g th e offe n d in g p or t ion of th e sou n d ’s h igh fre q u e n cy con t e n t. You’ll se e t ha t com m on se n se a n d you r e a rs h ave a t le ast a s mu ch to d o wit h good u se of e q ua lize rs a s t he t h e o ry be h ind t h em . Ye t it p ays t o k now t h at t h eory ; you’ll d o b et te r wo rk k n owin g t h e th e ory wh e re com m on se nse would on ly get you so fa r. E n g i n e e rs u se e q u alize r s to a d ju st th e a mp lit ud e of a sign a l wit h in sp ecific a n d con tro l l a b le fre q u e n cy ra n g e s . Th e m a st er fa d e r on you r con sole a d ju st s t h e am p lit u d e of t h e en t ire a u dio sign a l. Th ink of a n e qu a lize r a s a fre q u en cy-spe cific fa d e r; it in cre a se s or de cr ea se s t h e am plit ud e of a sign a l a t cer t a in freq u e n cie s on ly.
RECORDING JANUARY 2000

Looking high, looking low Th e fre q u e n cy re sp on se of a device d e scr ib e s it s ab i l it y t o cre a t e ou t p ut sign a ls t h a t a re con sist e nt a cross t he e n t i re a u d io fre q u e n cy ra n g e . Fi g u re 1 shows at yp ica l ex a m p l e , in t his ca se a d evice with a n ou t p ut t h at e m p h a s i ze s t h e low fre q u e ncie s a n d d e -e mp h a size s t h e h igh fre q u e n c i e s . It crosse s 0 d B a mp litu d e cha n ge (u n it y g a i n , n e it he r m ore or le ss a m plit ud e ) at ab ou t 1 k Hz. M u s i c a l ly sp ea k ing 1 kH z is a ra t h e r h igh p it ch , a l m o s t t wo oct aves ab ove mid dle C. But ke ep in m in d t h a t m a ny in st r u me n t s p layin g lowe r n ot e s will h ave some h a rm on ic cont e n t a t t his fre q u e n cy, w h i ch we m ay n e e d t o alt e r. Im agin e r ou t in g a cou p le of sin e wave s int o t his d e v i c e . On e is se t t o a 1 kH z fre q u e n cy, a n d t h e ot h e r we ’ll m ove up a n d d own t o var iou s freq u e n cie sin com p a rison t o our 1 kH z re f e r e n c e . We ’ll u se m e te rs t o a s s u re t h a t b ot h sin e waves a re ke pt a t t h e sa m e am p lit u de (t o ou r e a rs , h igh e r pit ch ed sine wave s sou n d mu ch loud e r th a n eq u a l-a m p lit u d e wave s a t lowe r fre q u e n cie s). Wh e n you m e a su re th e out p u t of t he d evice th a t is se t u p t o b oost low fre q u encie s a n d re d u ce h igh fre q u e n c i e s (a s p e r Fi g . 1 ) , a 100 H z t on e (a b it m ore t ha n a n oct ave b e l ow m id d le C) will m e a su re lou d er t h an a 1 k H z t on e in pu t a t e q u al a mp lit ud e . And a ve ry high fre q u e n cy sin e wave (say 10 k H z) will me a su re soft e r. If yo u ’ve eve r h ad t o liste n t o sin e waves for ve ry lon g— a s in th e...