H om e N ews Conta ct Sa les
Bass Rig
Bass Rig – A h ig h qualit y s peaker s ys tem for my bas s-gu it ar and do uble-b ass
T hi s spe ak er sy stem is de si gne d to be fle x ibl e in use , li ght-we ight a nd have high sound quali ty as it is to a mplify the a co ust ic upr ight bass. I hav e gigs i n ma ny di ffer ent lo catio ns v ary ing fro m re ce pti ons i n sma ll pl aces wher e onl y ba ck-gro und musi c is re qui re d, to lar ge r outdoo r liv e pe rfo rma nce s a t ja zz fe sti va ls so the se t- up must be fle xible e nough tha t I do n’t ha ve to tra nspor t a la rge syste m whe n I wil l only be play ing back gro und but it still must have eno ugh po wer a nd thro w whe n bei ng use d a t la rger ve nues. T hese cri ter ia le ad to a two piece sy ste m co nsisting o f a 15” woo fer with twe ete r that ca n be used as a full -ra nge
stand-a lone a nd a seco nd cabinet conta ining a single 18” wo ofer tha t ca n be a dded for m or e po wer a nd ev en stro nge r ba ss. I n the past I ha ve ha d many bass-sy ste ms ranging fro m m ultiple smal ler woo fe rs, se pa rate midr ange dr ive rs, to si ngle l ar ge wo ofe rs. I hav e found tha t for m e the onl y way to get r ea listic ba ss, e spe cial ly a mpli fi ed a coustic ba ss, i s to ha ve a t l ea st a 15” wo ofer. As in hi- fi the re is no substitute for a si ngle l ar ge driv er i nste ad of m ultiple smal ler ones. Pla yi ng technique s l ike “ slappi ng” can cal l fo r multi ple sm all size d wo ofer s, but they stil l will nee d a n a cco mpa nyi ng lar ge woo fe r to produce true l ife -l ike de ep no tes. I choo se a 15” midwoo fer with a re la tiv ely l ight- weight co ne and str ong mo tor to ensure a rticula te mi dra nge . T he co mbinati on with a twee ter give s cry stal cle ar tr eble a ll the way to 16 k Hz givi ng the ba ss- note s a we ll de fined edge a nd al so lets yo u he ar the tr ue cha ra cter o f a bass. Also both woo fer s use a neo dy mium ma gne t tha t m ak es the m ve ry l ight-we ight co mpa re d to standar d ferr ite ma gne ts – I do n’t wa nt to ge t back pro ble ms!
Let’s ge t funky !
Th e t weeter
T he Cel estio n H F- 50 i s a com pa ct bulle t twe ete r with a 60 degre e conica l radia tio n patte rn. It has a high e fficie ncy of 103dB’s and can be cr ossed fro m 3kH z upwa rds if a 3rd or de r netwo rk i s used. It has a stur dy thi ck pla stic face -plate and ca n found in some EBS bass-ri gs. I used i t for i ts re la tive ly l ar ge bandwidth, ve ry co mpa ct size and lo w pr ice.
Th e midwo ofer
T he Cia re 15.00N dw1 is a 15 i nch / 39cm paper co ne woo fer with a usable fre que ncy range up to a bo ut 1 kH z official ly but whe n used wi thout a cro sso ve r it ca n be stre tche d up to 3 kH z which i s the cro sso ve r po int to the twee te r. It has a stro ng alumi nium and ma gne si um bask et with a smal l but ve ry stro ng neo dy mium ma gne t pro ducing a B l of m ore than 25T m. T his m ak es a ve ry li ght we ight syste m; the whol e dr ive r onl y wei ghs 6,3kg’s. Othe r positiv e para me ters ar e the v ery hi gh Qms o f 14,47 le ading to a ve ry lo w R ms o f 2,2kg/s. F inal ly with an Xma x o f 7mm; a n SP L of 97dB and 500wa tts of po wer ha ndli ng this dri ve r ca n pla y lo ud.
Th e w oofer
T he Cia re 18.00N dw i s a n 18 i nch / 46cm paper co ne woo fer with a usable fre que ncy range up to a bo ut 1500H z. It has a str ong a luminium a nd magnesium ba ske t wi th a sma ll but v ery str ong ne odym ium magnet pr oduci ng a Bl o f mo re tha n 28Tm . Thi s ma ke s a v er y light we ight sy ste m; the who le driv er o nly we ighs 6,6k g’s. Other positi ve par ame ter s a re the v er y high Qms of 10,5 lea di ng to a l ow Rms of 3,6kg/s (Rm s is pr opor tiona l to the cone a re a) . Fi nall y with an Xma x of 5mm; an SP L of 100dB and 800watts of powe r handling this dr ive r can pla y v er y loud. Bo th woo fe rs use Ka pton vo ice- co il for mer s with 4-inch / 100m m dia mete r.
T he dr ive rs.
Th e c abin et in side an d out
Bo th box es ar e made fro m 18mm thick B alti c Bi rch ply woo d and are ide ntical e xce pt fo r the driv er cut-o uts a nd de r efle x po rt tuning a nd po sitio n. Bo th cabine ts me asure 566x 506x 386mm with a n inter nal net v olume of 70 litr es. T he 15.00N dw1 cabinet uses one M ona co r MB R- 110 r efle x po rt with an inter nal diam ete r of 110mm a nd a le ngth of 50mm giv ing a tuning fre que ncy of a bo ut 54H z – this results in a mor e full-bodie d ba ss char acter co mpa re d to a l owe r tuning frequency. This por t i s place d in the centr e of the re ar wa ll fo r ma xim um e fficie ncy. The 18.00Ndw ca bine t use s two M ona co r MB R-110 r efle x po rts with an inter nal diame te r of 110mm a nd a le ngth of 300mm givi ng a lo w tuning fre que ncy of 45H z. T hese por ts a re pla ce d in the bo tto m pane l and ra di ate the ir e ne rgy to wards the flo or. T he ca bi net stands on 30mm high rubbe r fee t cre ati ng a cav ity to l et the do wn-firi ng po rts ra di ate . The co upli ng of the air -ma ss unde r the wo ofer ca bine t l owe rs the tuni ng fr equency mo re to war ds 40Hz so that to ge ther with the lo w-pass cro ssove r o n the 18.00N dw i t wo rk s li ke a subwoo fe r addi ng mor e we ight, e spe cial ly whe n using a 5 or 6- str ing bass. Also a n a coustic do uble -bass be ne fits fro m this subwo ofe r se t-up i n ma ki ng the instrume nt sound l ar ge r co mpar ed to the top cabine t o n i ts own. The ca bine ts a re stre ngthe ned wi th 40x 40m m wo od on all i nt erna l edge s a nd acr oss the to p a nd bo ttom panel s to give mor e stre ngth. T he la rge ci rcula r woo fe r cut- outs ar e glue d to the i nside o f the re ar pa ne ls to gi ve the se pa nels mor e stre ngth and mi nimize vibra tions. A ll ex ter nal com er s ar e fitted with sta cka ble pro te cti ve pla sti c cor ners and e a ch cabinet has a la rge pa ir o f sturdy meta l re cessed ha ndle s. T he fi ni sh is bla ck semi -gloss pa int wi th bla ck pro tectiv e gril les. A ll the har d- ware is a ttached wi th ma tching black cro ss- hea d screws. Inte rna l da mpi ng consists o f Pr ite x wedge moulded fo am o n a ll inte rnal wa lls e xcept fo r the inside of the fr ont ba ffle . Inter nal wir ing is 4mm2 OFC coppe r wir e. On the r ea r pa nel I have use d pr ofe ssio nal N eutr ik Spea ko n co nne ctor s for durable co ntact.
T he top ca bine t witho ut dam pingm ate rial.
Cros so ver and lis tening
T hi s bass-ri g is de si gne d with fl ex ibi lty in mind. Fo r smal l gigs I use only the top ca bine t i n which the 15-inch i s conne cted dire ctly to the a mpl ifier w ithout any for m of cr ossov er. Irr egul ar itie s in the fre que ncy curv e a re cor re ct ed by the 11-band e qua lize r on my Tra ce -Ell io t a mp- hea d. The twe ete r has a 3rd or de r cro sso ve r in i ts signal path co nsisting of two high quali ty po ly pr opyle ne capacito rs and a n a ir- cor e inducto r in a T-configurati on. N o damping r esistor s a re used to ma intain the ma xi mum o utput le ve l that a ga in ca n be da mped o r bo oste d by the equali zer. The use o f a n e qua lize r is a must whe n play ing i n a ll types of ve nue s beca use the ro o m a coustics ca n be so ex tre mel y di ffer ent ea ch ti me and y ou nee d to a djust the to nal bal ance to ma tch the situa tion of the mo ment. Also e lectr ic bass-guitar ne eds a sl ightly differ ent se tting co mpa re d to my double –ba ss and diffe re nt pla ying t echnique s can call for differe nt EQ- settings.
Fo r la rger gigs I add the 18” subwoo fer cabine t tha t ca n be conne cte d dire ctl y for ma xi mum o utput le ve l, but m ost o f the ti me it is conne cte d with a first-o rder l ow- pa ss crossov er. Two cor re ct ion netwo rk s r un para lle l to the wo ofer : the LCR-ne twor k flatte ns the upper of the two typical bass-re flex impedance pe ak s so tha t the low- pa ss inducto r can do wha t i ts me ant to do at lo wer
fre que ncie s. F ur ther mor e ther e is an RC-ne twor k to com pe nsa te the inducti ve r ise of the vo ice- coil so tha t the l ow-pass inducto r can do wha t its m ea nt to do at higher fre que nci es. On the pho to the y ell ow capacito rs mak e up the 68uF nee de d, I ha ppene d to hav e these ca pa citor s fro m a pr ev ious pr oject – y ou can also use a single capa ci tor o f the cor re ct va lue for the sa me r esult. N ow do wn t o be ing “o n t he roa d”. F ir st o f al l the hav ing two separ ate r el ativ el y compact enclo sur es mak es tra nspor t a nd set-up ve ry fle x ibl e and e asy. Li fti ng them in and o ut o f a ca r do esn’t bre a k yo ur ba ck and a t ho me the y sta ck nicel y in a corne r be hind the bedro om cupboa rd – they ha ve to be ca rri ed up a nd do wn the sta ir s! Al so the y fit pe rfectly o n m y thre e-whe el ed tr anspo rt bicycle . So und qua lity i s ve ry r ea listic re -pro ducing the char acte r’s o f the di ffe rent instrume nts – a Ja zz Ba ss sounds lik e a Ja zz Ba ss, a Musicma n Sti ngra y sounds li ke a M usi cm an Stingray. A coustic bass is pro duced “a co usticall y” with a na tural lo w-e nd and midra nge . T he top-e nd cl ar ity ma ke s the o ve ral l so und nicely ar ticulate . Othe r qua litie s a re the i mme nse r ese rve of pow er, giv ing plenty o f dyna mic he ad-r oo m. T hings nev er get congested or com pr essed; I ha rdly e ve r have the vo lume k nob o f my 150wa tt a mpli fi er past se tting 3 on a scale of 1 to 10. Any furthe r just ge ts to o lo ud. T he 15”/ twee ter to p cabine t o n it s own produces a we ll ba la nce d sound tha t sa tisfi es fo r most occasio ns a nd woul d be a ve ry goo d ba ss- spe ak er o n its own. But wi th the a dditio n of the 18” woo fer the botto m-e nd becom es po werful and str ong a nd the ov er all sy ste m efficiency r ises. M y do uble -bass so unds lik e a doubl e- ba ss and no t lik e an el ectri c upr ight.
T he cro sso ve r sche matic.
Cros so ver co mponen ts :
L1 = 0,33 m H ai r-co re inductor, 1mm wire , R = 0,35 ohms
L2 = 6,8 m H high-po wer iro n-cor e or ste el- la mina ted inductor, R = 0,50 o hms
L3 = 10 mH a ir- core inducto r, 1mm wir e, R = 1,55 o hm s (the hi gh re si sta nce her e is i mpo rta nt) C1 = 300uF bi-po lar ( 3x 100uF pa ral lel bypassed by 1,5uF MKP )
C2 = 68uF M KT o r standard MKP
C3 = 4,0uF MK P (3,9uF standa rd MKP bypasse d with a 0,10uF M undor f M- Ca p Suprem e) C4 = 4,7uF MK P (3,9uF standa rd MKP bypasse d with a 0,82uF M undor f M- Ca p Suprem e) R1 = 4,7 ohms / 20 wa tts ceme nt resisto r
R2 = 4,7 ohms / 20 wa tts ceme nt resisto r
Ha rdwar e.
N OTE: T hi s design is strictly fo r the home DIY e nthusi ast and no t to be used pro fessiona lly without my per missi on!
Tony Ge e, The N ethe rla nds August 2006, update d Apri l 2007
