Air horns are the upgrade path for any classic-MG owner who has experienced the limitations of the original electric horns. Where the original horns produce a modest sound level easily masked by modern traffic noise, a quality twin-tone or triple-tone air horn kit produces a clear, distinctive sound that carries through any traffic and reaches the attention of the driver being warned.
This is a genuine safety consideration on cars that share modern roads with larger, better-insulated vehicles whose drivers may not hear the standard horn above their own cabin noise, and is particularly relevant for the low-slung sports cars in the range that can be overlooked by drivers of larger vehicles at junctions and roundabouts.
What the Kit Contains
The air horn kit is supplied complete with compressor, trumpet horns, relay, air hose, and the supporting fixings for a complete installation. The horns are matched, a longer horn producing the lower tone and a shorter horn the higher tone, with the two together producing the characteristic two-note sound, while triple-tone sets add a third harmonised note for a more commanding effect. The horns are constructed from chromed brass or stainless steel, with the visible trumpet shape giving the installation its distinctive period-sporting appearance, and the compressor is a small electric unit that supplies compressed air to the horns within a fraction of a second of the horn-push being operated. The kits are compatible with both positive and negative earth vehicles, suiting the full range from the early positive-earth cars through to the modern MGF and TF.
Installation & Relay Requirement
Installation requires finding suitable mounting locations for the horns and the compressor, the horns mounted facing forward, typically through the grille area or behind the front bumper, where the sound is unimpeded, and the compressor in a sheltered engine-bay or front-compartment location protected from direct heat and moisture but with sufficient airflow for cooling. A relay is essential in the installation, because the compressor draws more current than the original horn circuit was specified for, and running the full current through the horn-push switch would damage the contacts. The relay is triggered by the existing horn push, so the standard horn control operates the air horn without modification to the steering wheel or column, and cars already fitted with direction indicators may have a suitable relay in the circuit while cars without may need one fitted.
Sound Character
The sound character of a twin-tone air horn is distinct from the original electric horn, louder, longer, and more melodious, the horn pair sounding for as long as the horn-push is held with the compressor maintaining air pressure throughout, so brief operations produce short pip sounds and sustained pushes produce the longer warning notes typical of a serious horn application. The dual-tone harmony gives the sound a distinctive quality that is unmistakeably an air horn rather than an electric one, appropriate to the period-sporting character of any classic MG and clearly heard above modern traffic noise, with the standard electric horns able to be retained as a backup or removed.