FinkTeam’s Borg is two-way floor standing design featuring a 10.25 inch high-power mid/bass driver and an Air Motion Transformer (AMT) tweeter.
Borg is a significant design exercise as knitting a 10.25 inch mid/bass, albeit an extremely fine one, with a HF unit is never easy. To combine the two drivers to achieve a flat frequency response and, more importantly, a slow even mid/HF roll off in the power response is a significant feat of engineering. There is no off-axis hole in the middle effect.
Borg is designed as a more domestic friendly loudspeaker than the WM-4. Borg’s low frequency tuning is designed to deliver weight and drama to music but without making it a total diva when it comes to room positioning.
Of course, it isn’t as good overall as the WM-4 but then neither does it demand a huge room and the finest amplifier and sources. Believe us when we say that Borg will rise to the challenge of the finest electronics, but they are not essential to enjoy Borg’s talents.
Cabinet
Typical loudspeaker cabinets have pronounced structural resonances which are very audible and reduce the speaker’s ‘signal-to-noise ratio’. At FinkTeam, we take this aspect of loudspeaker performance very seriously because we know that a quiet cabinet allows the reproduction of low-level detail in a recording that is otherwise swamped by spurious cabinet output. Listener fatigue is avoided by reducing colouration and time smear. Stereo image focus is improved.
The design emphasis is on panel damping. It is impossible to force all the panel bending resonances above the passband, so instead, they are damped to reduce their amplitude to below audibility. This damping is achieved using a multilayer construction that combines multi-thickness MDF panels with a damping layer whose internal friction converts vibration into heat. FinkTeam developed algorithms help specify ideal material thicknesses to achieve the best results, but the ultimate determination is made by subjective assessment.
Enthusiasts spend thousands buying quieter equipment – products that seem to generate (or not in fact) more space between notes to have the effect considerably reduced by noisy loudspeaker cabinets. FinkTeam’s COMSOL modelling and Laser Scanning allow prediction and measurement of the results of cabinet designs.
An example of this was the cabinet opening to mount the 10.25 inch mid/bass driver. Even with the drivers rigidly mounted, there was some unwanted vibration. Almost invisible to the touch test, it was obvious under the laser scanner. A solid metal ring behind the driver mounting solved the problem and increased the signal to noise ratio.
AMT HF Unit
The tweeter is an Air Motion Transformer (AMT) operating according to the principles established by its inventor Oskar Heil.
Developed by Mundorf together with FinkTeam and manufactured specifically for FinkTeam by Mundorf, the AMT has a strong 25um-thick pleated Kapton diaphragm with 50um aluminium strips.
This material has extremely good internal damping, resulting in particularly low distortion. A special etching process was developed to produce it and the diaphragm configuration optimized through a large number of tests.
Given the 10.25 inch mid/bass unit and a lower than average crossover frequency of 1600Hz, a larger AMT driver with a 6464mm2 surface area was ideal. Frequency response easily reaches up to 30kHz while distortion is very low and mainly second harmonic. The AMTs almost constant impedance also facilitates simplified crossover design.
