With over 70 years of
industry experience, B&C Speakers has designed and built thousands of
unique transducers. Each year, our sales and engineering teams work together to
develop a comprehensive catalogue. While this catalogue reflects the large
majority of our technologies, it is primarily designed to feature more recent
additions to the product range.
B&C Speakers - All about the Performance
B&C’s specified Nominal Power Handling is measured according to the AES2-1984 standard. The transducer under test is driven for a two-hour period with a pink noise signal having a crest factor of 2 (or 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 are tested in free air. Compression drivers are coupled to their recommended horn. Power is calculated using the RMS value of applied voltage – averaged over the test period – and the minimum value of electrical impedance within the working range of the loudspeaker. After the test, the transducer must be in working order, without permanent impact on its technical performance. Due to the transient character of most musical programs, whose crest factor is commonly 12 dB or more, it is customary to specify a “Continuous Program Power Handling”, double of the Nominal Power Handling, as a recommended amplifier power in order to fully exploit the thermal and mechanical capabilities of the transducer without any clipping in the amplifier stage. On the contrary, if the amplifier is pushed to its limits and shows frequent saturation, its power specification should be less than the rated Nominal Power Handling of the loudspeaker.
Evolution is a
process that affects not only products, but also their technical
specifications. Constant advances in research provide more precise methods to
measure the performance of loudspeakers and describe their features.
Thiele-Small parameters have become the universal language for describing
loudspeaker behavior in the small signal domain. Nevertheless, they comment
little on the working limits of loudspeakers in the large signal domain. These
limits are customarily indicated by Xmax, the maximum linear excursion. In
a typical measurement, this value corresponds to a maximum of 10% total harmonic distortion (THD) with
a sinusoidal signal (though most manufacturers, including B&C, now
typically provide data for Linear Mathematical Xmax, not measured Xmax). Recent
research shows that this method can yield ambiguous results, and even different
numerical values for the same loudspeaker. The main limit of this measurement
is that it looks at the output signal instead of the physical features of the
driver itself. On the contrary, the most up-to-date instruments for distortion
analysis can measure the variations in loudspeaker parameters when they are fed
with high-level signals. In this way, an excursion limit can be fixed beyond
which the parameter’s variation becomes excessive. The “Xvar” value reported in
our data (generally after the traditional “Xmax” value) is measured this way.
Beyond this excursion limit, the loudspeaker force factor (Bl), or the total
suspension compliance (Cms), or both, drops to less than 50% of their small
signal value, producing high distortion levels and strong variations from small
signal behavior. This new technique yields different results from the standard Xmax
measurement. B&C Speakers believes that this added information gives a more
accurate and reliable description of loudspeaker capabilities in actual
Every product from B&C Speakers is 100% quality tested before it is packaged and shipped. We perform a set of measurements on every component to ensure that its frequency response, harmonic distortion, and electrical impedance fall within established tolerance windows. Each cone loudspeaker is additionally tested using a low frequency, high-voltage acoustical sweep to check for vibrations or noises (rub and buzz). Each product is guaranteed and supported with a 3-year limited warranty.
A 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 in 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 undesirable consequences: reduced excursion capabilities, increased mechanical stress, and increased distortion. These are 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 DC offset leads to poor performance and shortened loudspeaker life.
loudspeakers are designed with DC offset reduction in mind, especially our
large excursion 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