Frequently Asked Questions

A: It largely comes down to personal preference. There are four main points to using two, spaced speakers:

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• With a long locomotive and rear-mounted speaker, adding a second speaker in the front better localizes the sound, including the important horn and bell, so that all of the sound doesn’t emit from the rear end. It shifts the sound more centrally to the locomotive. This may not be a factor with some models depending on where the speaker is located and/or the locomotive’s overall length.

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• A smaller, front-mount speaker can sometimes increase a bit of the upper-mid spectrum (but sometimes not, as explained shortly).

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• The two speakers in the shell will acoustically couple at some points in the spectrum while nulling at others. This is called comb-filtering. It skews the overall frequency-response. These points will vary with speaker sizes, their positions and distance from each other in the model and the shell’s acoustics. Sometimes this addition sounds quiet desirable, sometimes not so much. Which is better or worse will again fall to personal preference.

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• Adding the second speaker will permit louder volumes (if desired).

 

Using the rear+front dual-speaker option will sound different for every locomotive. This is because different speakers vary in design, their shape, size and frequency-response and the distance they are spread apart depending on locomotive design/length. This results in unpredictable behaviors of coupling between the two, spaced speakers. One larger, single speaker will always result in the purest sound, but sometimes two combining in various ways can result in a bump of perceived “warmth”, even if technically the system frequency-response has been compromised. Combing two speakers will result in less perceived bass and high-frequencies due to the increased midrange of the two speakers combining. Some people perceive the mid-range increase as “more bass” when in reality, there is less perceived bass, but a “thicker” sound from louder mid-range. When combining two full-range speakers, you will never get “more bass” or “more highs”, only more mid-range, due to the laws of sound-propagation and summation.

 

Does adding a smaller speaker increase the high-frequency clarity? Not technically. Generally the larger the speaker, the deeper the bass, and shifting the enclosure smaller in size shifts the low-frequency response up. The smaller speakers don’t have more high-frequencies than the larger ones, simply less bass. The smaller speakers will place more emphasis on the mid-range, where the larger ones will have a smoother mid-response, but the higher-frequencies will be about the same.

 

You tend to get a more even response using two of the exact same speaker, identical in size, shape and all other specifications. There will still be uneven frequency-combining and canceling (comb-filtering) between the two, but the sound can be perceived as more “cohesive”.

 

What about close-coupled speakers? As explained in the technical white-paper and demonstrated with accompanying videos, close-coupling two speakers (or two drivers on one enclosure) still results in less lower and higher-frequencies and more midrange. However, since the speakers are nested together, the sound can be more predictable since the dual-speaker will behave more or less the same in any number of different locomotives.

 

I tend to only favor two, spaced speakers when the only speaker in the loco is all the way to the rear. Even if there are slight sonic detriments from the combination, I will take that compromise to avoid hearing all of the sound from the rear alone. The deepest, clearest, most detailed sound will always come from using a single speaker. My ultimate preference is one large speaker between the cab and motor. This offers the best technical sonics and places all of the sound pretty much right where it should be, but only a few locos use this approach.