Author: Karsten Hein
In autumn of 2022, I was asked to take part in the development of a loudspeaker. The design had been created by a friend in the industry and was based on Tang Band’s coaxial W8-2314 driver. The Tang Band chassis used a bamboo-paper composite to create a rigid light-weight midband diaphragm and a coaxially mounted inverse dome tweeter made of an aluminum-magnesium amalgamate. Powered by a neodymium engine, the combined driver unit was capable of producing an impressively wide frequency response that ranged from a low 38 Hz to an ultra-high 40,000 Hz. Instead of being mounted inside a ported cabinet, as recommended by the producer, the W8-2314 driver was built into a cloth-dampened open baffle design and its bass cut via crossover. Its bass was supplemented by an open-baffle dipole design featuring four dynamic 28cm paper composite drivers.
3 Nov 2022 — Listening Test 1: I set the speakers up in our spacious upstairs listening room that featured irregularly slanted walls and a 4.5m heigh ceiling at its centre. Setting the open back dipole up in the exact position of our Epicure EPI 500 speakers proved to be too close to the rooms front wall. Both soundstage and mid-bass seemed overly compressed. In steps of a few centimetres I pulled the cabinets forward until the sound stage seemed right and bass was tight. At this point, the Tang Band driver was 107m from the room’s front wall. The listening triangle was at a relatively short 2m. The provisional crossover could still be adjusted in three steps, and I ended up with step 3, which was most likely the highest cut-off frequency and seemed to offer the cleanest sound.
In this setting, however, it also became apparent that the bass cabinet was still suffering from resonances that interfered with the upper bass to lower midband creating some smear in this section. At this point, there was no inner bracing to support the cabinet construction, and since the four drivers required four large holes drilled into the sides, some rigidity was lost. It was difficult for me to judge what the speakers would sound like once these resonances were eliminated. On the other hand, I enjoyed the open-baffle bass sound that seemed very natural in our listening room. I could well imagine that a central bracing might have a positive effect. Perhaps bitumen matts could be applied to quiet the cabinet. Looking at the narrow gap between the left and right facing drivers, I thought that physically connecting their magnets in the middle somehow might cancel out cabinet vibrations. It might also be possible to provide an electronic filter to cut the most relevant resonance frequencies.
[Revision in progress…]
Test system: Marantz CD-17 via HiViLux Reference SP/DIF cable on Cambridge DAC Magic 100 via HBS Silver Solid-Core Interconnect on Dynavox VR-70 via Belden 9497 in Y-wiring on the loudspeakers
Test environment: 14m x9m listening room with irregularly slanted walls and 4.5m ceiling height at its centre. Listening distances in equilateral triangle of 2m. Midrange driver to front wall distance 107cm. Resonance absorption towards the floor: 8mm high and 40mm wide steel ronde + 4mm high and 40mm wide felt cushion. Resonance-to-midrange absorption via knobbed rubber acoustic isolation pads 12mm high and 40x40mm in square.
Tang Band W8-2314