Designed in 1958, these Lowther Acousta 115 designed folded horn enclosures are housing a set of PM6A drivers that are in perfect working order and in excellent physical condition. The cabinets themselves are in very good condition. There are some surface scratches and marks, but they present themselves very well. The binding posts look to be made by Cardas. The cabinets were constructed for the original owner that we acquired them from. Included in the sale from the original owner are two "Sound Practices" magazines. There is a feature about the Acousta 115 cabinets in the magazines, including detailed construction plans that were used to construct these cabinets, as well as a write up about Lowther. Grills are included but they do not fasten to the speakers, they just sit in the front panel cavity of the cabinet while the speakers are not in use.
Electrical Q QES 0.51
Mechanical Q QMS 4.25
Total Q factor QTS 0.46
Suspension equivalent air volume VAS 56.001 litres
DC resistance RE 7.4 Ω
Voice coil inductance LE 0.12856 mH
Force factor B·l 7.283 T·m
Suspension mechanical resistance RMS 0.8 N·s/m
Suspension mechanical compliance CMS 894 µm/N
Moving mass MMD 11 g
Moving mass (including airload) MMS 12.75 g
Surface of the diaphragm SD 210 cm²
Effective diaphragm diameter Ø 16.4 cm
Maximum linear excursion Xmax ± 1 mm
Displacement volume at Xmax VD 21 cm³
Efficiency η₀ 1.106 %
Efficiency bandwidth product EBP 87
Overall depth 105 mm
Mounting depth 96 mm
Diaphragm material Twin Paper
Voice coil diameter 39 mm
Magnet Alcomax 3
Magnet diameter 91 mm
Air gap height 5 mm
Flux density 1.75 Tesla