15B&C喇叭单元_2009Catalogue

C a t a l o g u e 2009Find your local distributor at ®Località VallinaItalia220 W. Parkway Unit 11USAA r t L c d s r l , F i r e n z e P h o t o L e o n a r d o D .I ., S t u d i o P r o t o , F i r e n z e P r i n t e d b y I n d u s t r i a G r a f i c a V a l d a r n e s e , S a n G i o v a n n i V a l d a r n o P r i n t e d i n I t a l yB&C Speakers Catalogue 2009Each year, our sales and engineering departments work closely togetherto develop a comprehensive catalog. While this catalogue reflects thelarge majority of our technologies, it only represents a small portion of our product line. With over 60 years of industry experience, B&C Speakers has designed and built thousands of unique drivers and woofers. Please refer to our web site (www.bcspeakers. com) to get the latest new product updates throughout the year. There you will also find more detaileddata for all models (including older ones). Our web site is by far our most up-to-date and complete information resource.B&C SPEAKERS IT’S ALL ABOUT THE PERFORMANCEPower HandlingB&C’s specified Nominal Power Handling is measured according to AES2-1984 standard. The transducer under test is driven for a two hour period with pink noise signal, having a crest factor of 2 (i.e. 6 dB) and filtered to the working range of the transducer itself (for instance, a 50-500 Hz range is typical for woofer testing). Cone loudspeakers with ferrite magnets are tested in free air, while neodymium magnet speakers are mountedin a box whose characteristics (volume and tuning) are describedin their technical specifications. Compression drivers are coupled totheir recommended horn. Power iscalculated using the RMS value ofapplied voltage – averaged over thetest period – and the minimum valueof electrical impedance within theworking range of the loudspeaker.After the test, the transducer must bein working order, without permanentimpact on its technical preformance.Due to the transient character of mostmusical programs, whose crest factoris commonly above 8 - 10 dB, it iscustomary to specify a “ContinuousProgram Power Handling”, doubleof the Nominal Power Handling, asa recommended amplifier powerin order to fully exploit the thermaland mechanical capabilities of thetransducer without any clipping in theamplifier stage. On the contrary, whenthe amplifier is pushed to its limits andshows frequent saturation, its powerspecification should be less than therated Nominal Power Handling of theloudspeaker.Excursion LimitsEvolution is a process that affectsnot only products, but also theirtechnical specifications. Constantadvances in research provide moreand more precise methods to measurethe performance of loudspeakers,and describe their features. Thiele –Small parameters have become theuniversal language for describingloudspeaker behavior in the smallsignal domain. Nevertheless, theycomment little on the working limitsof loudspeakers in the large signalregime. These limits are customarilyindicated by Xmax, the maximumlinear excursion. This value, measuredin our catalogue according to AES2-1984 standard, corresponds to amaximum of 10% total harmonicdistortion (THD) with a sinusoidalsignal. Recent research shows thatthis method can yield ambiguousresults, and even different numericalvalues for the same loudspeaker.The main limit of this measurementis that it looks at the output signalinstead of the physical features of thedriver itself. On the contrary, the mostup-to-date instruments for distortionanalysis can measure the variationsin loudspeaker parameters whenthey are fed with high-level signals.In this way, an excursion limit can befixed, beyond which the parameter’svariation becomes excessive. The“X var” value reported in our data(generally after the traditional “Xmax”value) is measured this way. Beyondthis excursion limit, the magnetic fieldseen by the voice coil, or the totalsuspension compliance, or both, dropsto less than 50% of their small signalvalue, producing high distortion levels,strong variations from small signalbehavior and power compression. Thenew technique yields different resultsfrom the standard measurementbased on THD. B&C Speakers believesthat this added information gives amore accurate and reliable descriptionIntroduction®on loudspeakers behavior in actual operating conditions.Quality ControlEvery product from B&C Speakers is 100% tested for quality control before it is packaged and shipped to our customers. Each product is guaranteed and supported with a 3 year warranty. For cone loudspeakers, with ferrite or neodymium magnets, a lowfrequency, high-voltage acoustical test is performed to check for vibrations or noises (rub and buzz). In addition, we perform a set of measurements including frequency response and electrical impedance on a defined percentage of each production run to ensure that each batch is within our established tolerance windows. For compression drivers, a sinusoidal sweep in the low frequency range is used to check for vibrations or noises. In addition, a complete measurement of frequency response and electrical impedance is performed on 100% of the drivers, and compared to the approved samples in our database. Coaxialunits share the QC procedures of both cone loudspeakers and compression drivers.DC OffsetA known issue of the dynamic loudspeaker is the instability of the average working position for frequencies above the resonance frequency. In this range, because of the phase relationship between force and position, the variations of force factor Bl vs position drive the moving assembly away from the Bl maximum. Intuitively, the loudspeaker tends to “slide” down the slopes of the Bl(x) curve. This is referred to as DC offset.Since the rest position is the optimal average working point, DC offset leads to several bad consequences: reduced excursion capabilities, increased mechanical stress, and increased distortion.This is due to the loudspeaker working in a region where nonlinearities are larger, and thermal dissipation and power handling are lower. Generally speaking, a large amount of DCoffset leads to poor performance and shortened loudspeaker life.All B&C loudspeakers are designed with DC offset reduction in mind,especially long throw subwoofers. Our motors are designed to have a large plateau around the rest position, both through magnet assembly optimization and voice coil design. Reducing the slope of the Bl curve, especially in the central region, will reduce instability and therefore the amount of DC offset. A special winding technique has been adopted in the most critical cases. Our suspensions are also designed to counteract DC offset before it degrades performance.B&C Speakers reserves the right to change specifications of the products without notice.x [m m ]21-0-1-2-3-4-5-63*104*105*106*107*108*10’9*10’10Frequency fl [Hz]B l [N /A ]252015105<<coil in X [mm] coil out>>-15 -10 -5 0 5 10 15DC component XDCForce factor Bl (x)(01:05:40)u n s t a b l es t a b l eo r n s L i n e A r r a y S o u r c e s H F N d D r io r n s L i n e A r r a y S o u r c e s H F N d D r iH o r n s L i n e A r r a y S o u r c e s H F N d D r i 0,5 kHz 1 kHz 2 kHz4 kHz 8 kHz 16 kHzH o r n s L i n e A r r a y S o u r c e s H F N d D r i v e r s H F D r i v e r s C o a x i a l s L F N d D r i v e r s L F D r i v e r s0,5 kHz 1 kHz 2 kHz4 kHz 8 kHz 16 kHzH o r n s L i n e A r r a y S o u r c e s H F N d D r i v e r s H F D r i v e r s C o a x i a l s L F N d D r i v e r s L F D r i v e r s0,5 kHz 1 kHz 2 kHz 4 kHz 8 kHz 16 kHz0,5 kHz 1 kHz 2 kHz 4 kHz 8 kHz 16 kHzH o r n s L i n e A r r a y S o u r c e s H F N d D r i v e r s H F D r i v e r s C o a x i a l s L F N d D r i v e r s L F D r i v e r s。