Thirty years ago an engineer from a large loudspeaker company called with a problem: His customer was insisting on better performance from an existing speaker design. The speaker was to go into production in a few weeks; the “hard” parts, the magnet, pole piece, and outer ring had already been manufactured. To improve the performance the engineer had to have more turns on the voice coil, while holding the same DC resistance, but in the existing design the round wire already filled the gap.
To accommodate this customers’ requirements, we utilized a wire that was one gauge larger and flattened to a 2½:1 ratio, with this we were able to give him just what he needed—more wire in a given space than possible with round wire, in this case 15 more turns of wire (5%). In addition, since it was larger wire we were able to keep the DCR the same. The speaker company was able to satisfy their customer without the time and expense needed to redesign the speaker and without changing or scrapping any existing parts.
The voice coils that we replaced using flat wire had a 1.016” inside diameter, 6.8 ohms DCR, .950” winding width, and a 1.120” outside diameter. The original coils were composed of 285 turns of #29 AWG round wire wound in 4 layers. The new coils used 300 turns of #28 AWG flattened wire wound in 6 layers.
From this initial request many years ago we have wound tens of thousands of this type of voice coil without changing any physical dimensions or electrical parameters. As a matter of course, over 30 years, we have refined the process extensively; as a result our flat wire manufacturing skills are unmatched in the industry. These processes utilize cutting edge systems such as laser micrometers, which provide precision monitoring of both the width and the thickness of the wire as it exits the rolling mill. These two dimensions combined with a reading of the ohms per foot give us the ability to target precisely the customer’s requested specifications. We are also equipped with precision wire payouts that feed wire at controlled tension to the winding machines by turning the horizontal spool of flat wire at the correct speed to match the winding machine.
