Tannoy HPD-385A
The following data has been obtained by dismantling and inspecting the HPD-385A low frequency cone:
| Tannoy HPD 385 | ||
| Voice Coil Measured Parameters | ||
| August 2000 | ||
| Depth | 13 | mm |
| Layers | 4 | |
| Turns | 128 | approx |
| Inside Dia | 53 | mm |
| Outside Dia | 54 | mm |
| Wire Gauge | 0.313 | mm |
| 12.30 | thousandths of an inch | |
| based on counting turns per mm | ||
| includes insulating enamel thickness | ||
| 29 | gauge | |
| 11.26 | thousandths of an inch | |
| rounded to nearest standard wire gauge | ||
| with allowance for enamel thickness | ||
| Wire length | 21.51 | m |
| 70.58 | feet | |
| Resistance/foot | 81.3 | Ohms/1000 feet for #29 gauge wire |
| Resistance | 5.5 | Ohms |
| measured | ||
| Resistance | 5.74 | Ohms |
| calculated from wire resistance per 1000/feet | ||
| Magnet Plate Depth | 9 | mm |
| Turns in Magnetic field | 69.23 | percent |
| Wire length in field | 14.89 | m |
| B*L driving factor | 19 | Tesla-meters = Netwons per Amp |
| Published by Tannoy | ||
| Magnetic Gap Flux | 1.28 | Tesla |
| (average) | calculated using estimated wire length in field |