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COMPUTER HI-FI LOUDSPEAKERS YOU CAN CARRY

 

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Putting some natty ideas together, SoundScience have come up with this interesting portable hi-fi system that works from a computer's USB output. Each cube loudspeaker houses a BMR drive unit, meaning it's derived from NXT technology where hi-fi sound is produced by flat panels, driven by exciters.


With the QSB though, SoundScience also power the system from the USB link, meaning it works from the computer's power supply. That eliminates the usual 'wall wart' supply, plus a tangle of cables. If you run Vista, Windows 7 or Mac, just feed high resolution digital through this system for fantastic sound quality, at home, in the hotel or on the move.

 

Is that not natty? Even more so is a price of €99, meaning under £100 (we hope!). Plus a claimed power output of 15 Watts per channel for good volume.

 

Contact    -        www.soundscience-corp.com


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TECHNICAL BACKGROUND, from QSB

Low power consumption amp.

Power over USB is limited to 500mA at 5V.  Even assuming no losses, this only translates into a maximum continuous power of 2.5W. So: how do we achieve a peak output power claim of 30W?

 

Well, audio does not have a continuous power profile. Audio peaks are high power, but transitory. The average of audio content, and therefore output power, is at a much lower level. This new efficient amp is capable of outputting instantaneous peaks of 15W/channel, and burst power of 7.5W/channel so cleanly reproducing the audio peaks, when required; as well as sustaining the lower average output power required for the rest of the audio content.

 

Think of the system as a reservoir, storing energy from the USB supply in capacitors; ready to release that energy only when the audio signal actually requires it. Plus the amp and the BMR driver are designed to match each other perfectly. In this way, the system adapts to the audio content and the USB supply constraint to reproduce your music in a truly efficient way. Energy wastage is minimised, there are no delays and the amp delivers power to the driver only when needed - always resulting in clean audio with no distortions, even at maximum volume.

 

BMR Driver

The overriding design brief for the Qsb speakers was to have excellent audio performance across all frequencies , sound that can “fill the room” but with good dispersion and above all, a very compact form factor .

 

Conventional speakers present a problem here: the rigid piston loudspeaker becomes directional at high frequencies. To generate low frequencies the piston needs to be large, but to have good directivity at high frequencies it needs to be small. This intrinsic feature of the rigid piston means that we need one driver for low frequencies and a separate driver for high frequencies:

 

In turn this means that we need to introduce a crossover . Since our low power consumption amp is designed to present a constant impedance to the driver , and crossover introduces a phase shifting tendency giving rise to peaks and drops in impedance it is clearly not desirable.

 

Then we have off-axis problems: at higher frequencies you get pronounced directivity. Although the Sound Pressure Level  will be flat - the price for this is that the Sound Power Level (SWL) will start to fall i.e. the system will usually be optimised so that the optimum listening position will be restricted to a position between the two loudspeakers the  so-called “sweet spot”.

 

We began our search for super compact wide dispersion speakers with conventional drivers, mounting a small HF unit co-axially with the LF unit. But it wasn’t ideal- it wasn’t as small as we wanted, and besides, there were still acoustic problems.

 

Finally we decided BMR was the answer. For the theoretically minded, the basic theory is that if we start with a free, circular disc, which will naturally have circular modes and try to turn it into a loudspeaker, something extraordinary happens. For a perfect force, both the SPL and the SWL are flat. The BMR has a substantially flat SPL whilst also generating a substantially flat SWL, from a single radiating surface.

 

These are the characteristics which make it an ideal choice as a speaker driver .

 

Wider Dispersion –  even dispersion across all frequencies , avoiding the “sweet spot”

 

No Crossover – more compact- no separate woofer & tweeter, more matched load for the amplifier by removing peaks and drops in impedance .

 

Higher intelligibility – Because there is no crossover point, particularly in the critical 2-3K region, intelligibility is noticeably higher.

 

No Megaphone Effect – Because the BMR employs a flat diaphragm it gives a more natural acoustic output since it does not suffer the “megaphone effect”, intrinsic in cone loudspeakers.

 

Timing – Since the BMR is a single “full range” driver it exhibits perfect timing.

 

Audio Specs

 

Bandwidth (-6dB points) = 100Hz - 18kHz

Sensitivity = 83dB at 1W, 1m

Nominal impedance of drive unit = 8ohm

Minimum impedance of system = 8.2ohm

Quality factor of closed box passive acoustic system Qtc = 0.86

Theoretical maximum SPL = 96dB at 1m

 

...and Hi-Fi World says

BMR drivers are an extension of NXT panel technology and are appearing in Naim loudspeakers, for example. A few factories make them, in the Far East, and in Germany. BMR gives a great sound, with low distortion, little colouration, a smooth forward response and no crossover phase problems, just as QSB claim. In our experience mini BMRs sound lovely: bright, clean and open. This is an interesting product, especially at the price, that we hope to test.

 

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