Electronics patent of the month: Loudspeaker bi-wiring optionality
GB Patent Number: GB2477295
Granted to: GP Acoustics
As I was perusing some recently granted UK patents, a wry smile began to spread over my face when I came across this month’s choice. To me, it captured a quintessential part of British culture, which has been immortalised in many cinematographic productions over the years, namely the traditional ‘pub debate’.
So, the issue of critical importance over which we will deliberate today is: whether the audio aficionados amongst us should, or should not, bi-wire our speakers.
For the uninitiated, bi-wiring means that when you connect your amplifier to your speakers you provide a pair of two-conductor cables to each speaker, one to carry the low-frequency audio signals and a separate cable to carry the high-frequency audio signals.
This means that within the speaker the high-frequency signal is fed to the high-frequency drivers, known as ‘tweeters’, and the low-frequency signal is independently fed to the low-frequency drivers, the more familiarly named ‘bass’. This is in contrast to the standard wiring arrangement, whereby a single two-conductor cable drives each speaker, and the different frequency components are split off within the speaker by means of a crossover network.
At this point I will hand over to the patent draughtsman:
“Some within the audio community hold that this improves the sound quality of the system as a whole, by electrically separating the high- and low-frequency signals via the amplifier, which in turn leads to less interference. Others deny this, arguing that the two ways of making connections are electrically equivalent.”
And so, our storyteller continues:
“This debate over the merits of bi-wiring places loudspeaker manufacturers in a difficult position. If they provide only a single pair of terminals then the loudspeakers are made unsuitable to those who wish to bi-wire. If two pairs of terminals are provided in order to cater for bi-wiring, then opponents of bi-wiring can be offended that the manufacturer is (seemingly) indicating its approval of bi-wiring and must make arrangements to short the respective terminals via a suitable wire link.”
I am delighted to report that peace can now descend on these warring parties thanks to the innovation of our heroic patentee, GP Acoustics (UK) Ltd, whose UK patent no. 2477295 was granted on 2 October 2013. More importantly for the patent owner, it can avoid becoming embroiled within this skirmish.
GP Acoustics have developed a loudspeaker which has a low- and high-frequency signal input, both comprising two terminals of a first polarity and a second polarity, a network connected to the terminals of the signal input, and a driver connected to the output of the network.
The arrangement also includes a switch which is electrically connected to the two terminals of both the low- and high-frequency signal input. The switch comprises at least one element moveable between at least two positions.
In the first position the terminals of the low-frequency signal input are isolated from the terminals of the high-frequency signal input to please the anti-bi-wirers, and in the second position, one terminal of the low-frequency signal input is connected to one terminal of the high-frequency signal input and the other terminal of the low-frequency signal input is connected to the other terminal of the high-frequency signal input, to keep the bi-wirers happy.
And so, by placating both sides in this debate, silence may now reign.
Michael Jaeger is a patent attorney at leading UK patent and trade mark attorneys, Withers & Rogers LLP.
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