Installing Just a Speaker in a Non-Sound Loco for Lashup with Sound Loco?

[craigolio1]

This is something was considering doing in a pair of RDCs I’m building. They will always run as a pair. I’m not concerned with horn and bell sounds coming from both speakers, and I can hide a connector in the diaphragm.

I’m a ways away from finishing but if I beat you to it I’ll post my results.

 Craig.

[nickelplate759]

The weird phasing effect everybody is describing here occurs when 2 locos with their own decoders are running the same sound file, but since the electronic components are not identical on both decoders, the sound played from one of the decoder is delayed by few milliseconds.  It is a reverb. Standard stadium PA systems (where all the speakers are fed from the same audio source), where the speakers are positioned hundreds of feet apart exhibit an extreme reverb where you can actually hear the distinct sounds from each of the speakers.  At that point it becomes an echo.

But if the speakers fed directly by the same source (which is what Russ was asking for), and placed just few inches apart should not produce any appreciable phasing or reverb.

I think the phasing comes from the fact that the speakers are moving relative to the observer and they are not moving identically relative to the observer (they can't be, since they are in at least two places).

A simple, extreme, example is a Leslie speaker : https://en.wikipedia.org/wiki/Leslie_speaker
Both cones have the same input, but are always moving in a different direction and speed relative to the listener.  In the Leslie case the phasing effect is the entire point of building the speaker, but in the model train world  of course it is NOT what we are after.

[peteski]

If you look at at all the posts in this thread, they all discuss "phasing", they are describing the effect caused  by 2 locos equipped with identical decoders playing the same sound file.  Because of the slight differences in each decoder's oscillator clock frequency, or slight difference in their initialization timing, those decoders are playing the same exact sound file with couple milliseconds of playback time difference.  When the sound waves from both decoders' speakers reach the ear, they results in a very unrealistic phasing effect.

Nobody here seems to have mentioned hearing the results of 2 speakers separated by couple few inches, running from a single decoder.  There will not be any phasing, because those speakers are too close together for any phasing effect to take place.  In an earlier post I compared this setup to setting a stereo system at home or in the car to monophonic mode (which would be the closest example to what we are discussing here).

If you have your stereo system playing in monophonic mode you won't hear any phasing, regardless of whether you are staying put or moving between both speakers.

[nickelplate759]

If you look at at all the posts in this thread, they all discuss "phasing", they are describing the effect caused  by 2 locos equipped with identical decoders playing the same sound file.  ...

... If you have your stereo system playing in monophonic mode you won't hear any phasing, regardless of whether you are staying put or moving between both speakers.

Ah - I misunderstood the situation.  Two independent sources of the same sound are indeed almost certain to be slightly out of phase, and that can skew the apparent frequency spectrum of the sound so it it sounds off.   But your comment about a 2 speakers in "mono" is technically wrong - that's exactly what the tweeters of a Leslie speaker are (2 speakers in mono).  Although what makes the sound so distinctive is the fact that the phasing changes as the speakers rotate.    That said, after thinking about it, I realize that unlike Leslie tweeters, model train speakers don't/can't move fast enough for the effect to be noticeable.  So effectively you are right.

[peteski]

Ah - I misunderstood the situation.  Two independent sources of the same sound are indeed almost certain to be slightly out of phase, and that can skew the apparent frequency of the sound so it it sounds off.   But your comment about a 2 speakers in "mono" is technically wrong - that's exactly what the tweeters of a Leslie speaker are (2 speakers in mono).  Although what makes the sound so distinctive is the fact that the phasing changes as the speakers rotate.    That said, after thinking about it, I realize that unlike Leslie tweeters, model train speakers don't/can't move fast enough for the effect to be noticeable.  So effectively you are right.

Exactly.