Speakers and Speaker Mounting

SPEAKER MOUNTING

Speaker(s) should generally be mounted so that the sound can actually "get out" of the locomotive. A hole in the floor or fuel tank is acceptable, but open grills or a doorway may be a better choice as the sound can exit upward or outward rather than down towards the track. In some cases, particularly with some body shells, just mounting the speaker against the shell will be adequate as the vibrations of the shell can enhance the sound.

In general, the larger the speaker, and the better quality the speaker, the better the sound will be. And low frequency speakers ('woofers') are better suited to the mainly low frequency diesel sounds. And using multiple smaller speakers often produces better sound than a single higher power speaker at higher volume, and sometimes easier to find space in the loco to put the smaller speakers.

Enclosing the speaker in a chamber will also enhance sound reproduction. A very simple enclosure can be made with a tube. The longer the tube the better the speaker will reproduce low frequency sound which is inherent in diesel prime movers. It is usually best to seal the end of the tube, so there are no air passages to the rear of the speaker, thus creating a sound chamber. By carefully sealing all openings it may be possible to use the entire body shell as a sound chamber. A simple wall behind the speaker may be all that is possible or perhaps all that is needed.

The speaker should be mounted as per available space bearing in mind that sound reproduction is enhanced when a speaker is properly enclosed and baffled.

The speaker impedance should be kept near or above 8 ohms. Speakers of a lower impedance may damage the unit, and speakers of a higher impedance will work OK, but at a reduced volume level. Series, parallel or series/parallel connections are acceptable, provided the total impedance is 8Ω or more.

Different methods of connecting multiple speakers

Where to get speakers?

There are literally 100s or 1000s of speakers available, from the lowest quality, 'tinniest' and cheapest to the most expensive high quality hi-fi ones. As stated above, the biggest speaker that will comfortably fit, or even several smaller ones are the best for this application. It is recommended that you obtain good quality speakers, there is no need for the very expensive ones. You can either buy just the speaker only, or sometimes already mounted in an enclusure for PA work, or outdoor speakers from the marine/boat accessories people.

Two companies in Australia/NZ which offer a comprehensive range of speakers, amongst other electronic goodies, are Jaycar and Altronics. Both offer online internet sales in addition to having stores and resellers across the contry.

For garden railway equipment, Dallee Electronics have an excellent range of miniature speakers available, and can be ordered with the sound module.

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