70-Volt Distributed Speaker Line
Tap-wattage budget, reflected line impedance (Z = V^2/P), remaining taps, and run line-loss for a constant-voltage 70 V / 100 V audio line (NEC 640 / 725).
Formula and source
Constant-voltage line: total tap load = sum of tap watts; budget verdict total <= rating*(1 - headroom); reflected impedance Z = V^2 / P_total; line loss from wire resistance and the line current I = P_total/V.
Constant-voltage (70 V / 100 V) distributed-audio line design - tap-wattage budget, reflected line impedance Z = V^2/P, and run line-loss - per the standard 70 V distributed-system practice and NEC Article 640 / 725 (Class 2/3 audio) wiring, by name; first-principles Ohm's law.
Audience
This tile is built for electricians and the adjacent professions in the Electrical group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.
Related tools
Posture
Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.