Are your speakers in phase
Since sound decoders are such a popular topic, let’s talk a little about speakers. When installing more than one speaker in a locomotive it is important that they be wired together so that their polarity is the same. If you wire them in reverse polarity they will produce sound waves that are out of phase resulting in poor sound quality.
Although some speakers have polarity markings on them next to the solder contacts. Note that the speaker in the photo does have polarity markings below the ohm and watt ratings, but many do not. If the speakers are both the same type and from the same maker then it is usually safe to assume they have the same polarity contacts. However if they come from different sources that is not a safe assumption. So how can you tell which contact is positive and which is negative?
The easiest way to check polarity is to take a plain old 9 volt battery and connect a couple test leads to it. Next touch one lead to one contact on the speaker and the other lead to the other contact while watching the speaker diaphragm. If the diaphragm pushes outward then you have the correct polarity, so note which leads from the battery are positive and negative and mark that on the speaker. Repeat this test for the other speaker(s) and you are ready to wire them up.
For more tips on how to install speakers see the May 2016 DCC Corner column. I’ll have a lot more to say about speaker selection and wiring, so dig out you back issue.