Bowers & Wilkins 808 User's Manual
Contents
1. AAA net Urna Kant a Honzontal response asymme ncal 1kHz characteristic to enhance stereo imagery Specification Frequency Response 30Hz 1o 20kHz 2d8 Low Frequency Bass rellex employing Two 300mm drive units Helmholtz box resonance 22H Midrange System Acoustic line taading employing two 100mm units Bass Drivers BT300 Ckaphragm 270mm thermoplastic cone wih PVA compound coating Ultra long throw suspension voice cod Sor dia high temperature Kapton magnet system 4 5kg ceramic Thus unl i a high power handling development of the bass unit used in 801 Midrange Drivers MT100 Diaphragm 100mm aromatic polyamide Fibre matre cone cntically lormed and PVA impregnated following a laser interleromeiny computer iinked pattem Voice cod 26mm high temperature Kapton This unit es a high power handling version ol the midrange unit used in Harmonic Distortion LT pear Marga EA 1 mida Kr bmc Fu N _ len RE 4 1 I 1 Hs aperi aeu Ld High Frequency Driver TX32 Diaphragm 32mm polyamide formed to critical contour determined by computer linked laser inlerlerometny Coil aluminium former with high power Ipead out terninahons and immersed in ferra fluid or state otHne artr performance Magnet system lernte employing reversed held technology for increased flux on Vertical 0 1 5 dB over 10 arc Hornzantak 0 2dB over AC arc ZO0H2. Connect the loudspeaker to your amplifier by means of either the screw terminals or 4mm plugs The red terminal on the loudspeaker should be connected to the red terminal on the amplifier or the connection marked positive Correct phasing of stereo loud speakers is extremely important and incorrect connection will produce a loss of bass and a poor stereo image This will be rectified by reversing the connections to one of the loudspeakers itis good practice to keep the connecting leads between the power amplifier and speakers as short as possible and to use a heavy gauge wire to keep the DC resistance to a minimum It will be appreciated that the input to the laudspeaker is of complex impedance and when your system is operating at high levels very high currents will be carried by the inter connecting cables Considerable work has been carried out in recent years on the effect of different cables and there is fairly conclusive evidence to show that although subtle these differences are apparent We would recom mend therefore that if cable lengths exceed 2 metres care should be taken over their choice and in any event it is good engineering practice to employ really heavy gauge cables of the highest quality Bi and tri amplification In order to facilitate bi or tri amplification the inputs to each individual filter section low frequency midrange high frequency have been brought out to three separat
3. Instruction Manual Introducing Model 808 Model 808 is B amp W s response to the demand for a system capable of safely delivering sound pressure levels up to 120dB The same basic sophistication of BO1F S now regarded as the professional standard monitoring loudspeaker worldwide but incorporating a whole range of new design concepts and techniques 808 is a five driver three way system with sensitivity double that of 801F S and overall frequency linearity free from colouration and distortion providing both the professional recording engineer and the dedicated home user with the particular requirements for producing realistic sound levels in a large environment WARNING Because Model 808 is capable of such high sound pressure levels permanent hearing damage can result from a daily exposure duration longer than these examples 120dB 30 seconds 110dB 4 minutes 100dB 30 minutes 9098 8 hours Unpacking To avoid damaging the loudspeaker when removing from the outer case itis important to follow these instructions carefully 1 Stand the case on its bearers Remove the strapping unscrew the lid and lift off 2 Remove the three foam packing pieces from loudspeaker sides and bottom but leave the packing at the top 4 Gently ease the loudspeaker from the case and remove plastic cover Electrical Connection
4. occur over a narrow band of frequencies Rooms where all dimensions are different give the most even and natural bass response Protuberances and larger items of furniture tend to break up these resonances and where practical varying the position of such items can often favourably influence sound reproduction Soft furnishings wall coverings and even pictures influence middle and high frequencies ideally you should aim to avoid discrete resonances or ring ing and an easy test for this problem is a simple hand clap if resonances exist there will be a distinct overhang or sustain ing of the response which could last between 0 5 and 1 second A bookcase placed on a wall opposite a reflective surface such as a window will often help to alleviate the problem outlined above Alternatively a panel of acoustic tiles placed on a wall can produce a remarkable improvement In all B amp W designs the config uration of the drive units and the characteristic of the crossover network are So designed that the horizontal dispersion of the sound is broader than the vertical dispersion thus ensuring wider freedom of seating with accurate stereo information Figs 4 amp 5 The actual position of your loudspeakers within the listen ing room can widely influence sound reproduction Two typical positions are shown in figs 647 The environmental measure ments fig 8 show the wide variation which can be achieved by
5. e terminals No electronic crossover is required With normal operation using a single amplifier shorting links are provided which parallel the input terminals and the ampli fier may therefore be connected to any of these terminals Obviously with tri amplification separate amplihers will be used for each section but the more usual and recommended sys tem would be bi amplification where the larger of the two amplifiers is used for the bass section and the smaller ampli fier for the midrange and treble sections which are then con nected in parallel with one pair of the shorting links provided The Listening Room and Positioning Your Loudspeakers Environmental Controls In professional applications the acoustics will be well controlled Domestic listening rooms however da vary widely both in their acoustics and in the positioning preferred to operate the loudspeakers For this reason control has been provided for both the midrange and high frequency sections with precision switched attenuators The resulting characteristics are shown in the plots below fig 1 In terms of professional application Model 808 provides linear extension of free field response to 30Hz as this characteristic is ideal for a controlled environment with particular reference to digitally recorded material In less well controlled domestic environ ments however some attenuation of the ba
6. eaker will then automatically retum to normal operation The voice coils in 808 have been designed to withstand temperatures in excess of 250 Mechanical clearances also ensure that peak excursions cannot damage the bass driver voice coils Therefore to reduce insertion loss APOC is omitted from the bass section However some caution should be observed with amplifiers of over 600 watts per channel Ancillary Equipment As a discriminating listener you will not have chosen your 808 loudspeakers without thorough preliminary listening tests You will have discovered that far from being the weakest link in the chain as loud speakers are so often described the performance of the 808 warrants the best ancillary equipment available in order to realise its full potential While we cannot of course recommend specific equipment manufacturers there is a wide range of top quality components available Since you have already invested in one of the world s finest speakers you should therefore pay equal attention to your choice of pickup arm cartridge amplifier tuner tape recorder or CD player Differences between them may be subtle but they do exist and your own listening experience is an invaluable quide Because of its high power handling capability and protection circuits no damage can result to your 808 system by using an adequately high powered amplifier This is preferred as it allows sufficient headroo
7. loudspeaker positioning We cannot emphasise too strongly that time spent in experimenting with the position of your loudspeakers is invariably worthwhile u gt a tpt ites sw Sao A Wa gt eee So e Ss Switch position Midrange 0 High frequency 1 0 T Switch position High frequency 0 Midrange 1 0 1 amp 8 58 EN Bs PAS T9 RES gt UR am a a 4 imo in p as d p 4 ai ag J x Jj x lt TS im E ng gt dE OU Trete FIG 8 Mr ee ee Et Lr breer am mii AHE jsem iun ert m Tr E E O ETE an CE S va eee 2 SEP CITIES Wa wr fuer HE TEE fein uim zs de LEE Overload Protection B amp W were the first major loud speaker manufacturer in the word to introduce full electronic protection against damage and overload to their loudspeakers APOC audio powered over load circuit In Model 808 this protection is fitted individually to the midrange and high frequency drivers Should a thermal or transient overload condition occur drive will be automatically removed from the appropriate unit and the LED will show until the fault condition is removed The loudsp
8. m for the high level of transient information available and our minimum amplifier power recommendation is 200 rms per channel into 8 ohms Reliable advice is always avail able irom a reputable hi fi specialist and our own specially appointed B amp W dealer will be pleased to give you expert assistance Natu rally if itis possible to carry out a listening test in your home using familiar recordings this is the best way to ensure lasting satisfaction Free field Frequency Response OE E E OE WON EO BOE WO 5 8 OH OH OE O8 B OR Om OE E OW W W W OE BON B NON EON EON HON EH NON WOW m L x hang um Taken in Europe s largest anechoic chamber at Garston E Fault Finding Service Model 808 has been specifi Throughout the world BAW cally designed to withstand Loudspeakers have appointed high power levels With the distributors who are respon combination of APOC ferro sible for service Should you fluid tweeter high temperature experience any difficulty Kapton coils and polyester please contact the dealer from capacitors it is perhaps the whom you purchased the loud world s most reliable loud speakers speaker and should give years of trouble free service Polar Response wt of loudspeaker _ 8 dd amp od 4 4d cea er eet a 4 4 4 1 1 1 eier 4 4 414 i 34 4 4 Fit 6 ne 1 Ta uae HE LI TIN ala
9. ss extension may be desirable and an electronic bass contour control unit is in the process of development The driver configuration in Model 808 has been deliber ately conceived as a mirror image pair with the midrange high frequency assernblies offset from the vertical centre line of the cabinet This con figuration gives an asymmetrical polar characteristic relative to the centre axis of the loud speaker and can help in improving stereo imagery It is perfectly acceptable to position the loudspeakers so that these assemblies are more closely or more widely spaced As general rule if the loud speaker placing is relatively wide then the pairing should be such that the assemblies are adjacent fig 2 Conversely i closely spaced they can be further apart fig 3 Both the listening room and positioning your loudspeakers within the room will widely influence the tonal balance and stereo information you receive Choice of a listening room is often restricted but if you are able to choose the following points may be helpful All enclosed volumes exhibit resonances which in the case of the listening room will be essentially determined by the distance between parallel surfaces The strongest res onances will lie between 30Hz and 180Hz in average domestic room sizes The most unsuitable listening room would be one where all dimensions wall spacing and ceiling height are similar since all resonances
10. z 15847 Distortion 20Hz to 100Hz 100Hz to 20kHz 2nd Harmon 1 00 140 10008 Vm Sr Harmonic 1 00 0 79 nd Harmonie 0 50 0 64 9600 Im 3rd Harmonic 0 70 050 Max mum figuras at each teve Impedance Bohms nominal not ess than 4ohme al amy Sensitivity 1 Wall into amp ohms load lora sp or tdg al Tm Sinewave input at 1kHz Power Handling No upper limit on midrange and tweeter due lo automalic protection cifctats Bass FW continuous sinewave polw 400Hz Crossover ath order Bulterworth squared cantiguratian with crossover hequ ncos of 400Hz and with line delay correci n between midrange and tweeter by means all pass network Bi and tri ampinc 5 made easy hy separate terminals for each unit No electrolytic capacilors are used Dimensions Height 1050mm Van 113mm 43un with ninth 11 22mm 44 Vain with wheels and pnt Width samm 25 Depth 510mm 20m without gre 542mm 21 in with grille Weight 7Bkg 1801b MSN o Peme Ta E fies Fe
Download Pdf Manuals
Related Search