Hello, all. Laurie had given me the idea of using Sugar Cube speakers in the "Speaker Enclosure" thread and I finally had a chance to experiment extensively with them, and they sure do sound amazing. I compared the sugar cube speaker to several Soundtraxx speakers (I had previously purchased every speaker Soundtraxx makes so that I could make and sell enclosures for them). I set up a lab by making an enclosed box lined with acoustic panels where I placed the speakers and a professional microphone. I used graphical frequency-response software and a pink-noise generator to get as close to a flat line as possible. I made a baffle and glued it to the speaker and got to work.
I would have to say that sugar cube speakers sound better than every speaker except the Mega Bass line of speakers, which are often too big to be practical. I was amazed how much better they sound than the ubiquitous 28mm(1") round speaker. Another popular speaker, the 35x16mm oval speaker, seems to be the closest in comparison. Although it has a lower frequency response, producing more in the ~750Hz range, it is hampered by less high end than the sugar cube. It really takes a nasty dip in the 4kHz range, and also it does not seem to produce quite as much volume as the sugar cube.
I further experimented with the physics of the speaker. I tried putting it in close proximity to a piece of paper, where I was able to create different shapes such as flat and curved surfaces. Of course I also experimented with a loco shell. I have reached the following conclusions:
Vastly different sounds can be achieved simply by placement. For example, placing it inside an HO diesel shell with some empty space will sound quite a bit different than an enclosed mounting. Some guys put it under/in the gas tank of a diesel facing down, which in my opinion should yield the loudest results because the sound waves will reflect off the layout. However, in such a case driving over a level crossing will produce noticeably different sound than over a trestle or even a heavily ballasted section.
Just like my other speaker enclosures, I have confirmed that the "baffle" acts as a method to prevent sound wave cancellation. Interestingly, the sugar cube is as near an example of an omni-directional speaker as I have ever experienced. At first I thought that somehow sound was emanating from the baffled side, but I realized that because of the high loudness-to-size ratio, sound waves are able to project in all directions within a short distance. What is nice about this is that you could use minimal mounting points or attach it from the side leaving most of the space around it open thus retaining it's omni-directional characteristics, if desired.
Laurie, I was not able to verify that "hard mounting" made any appreciable difference. Touching the speaker's baffle side to the outside of the loco shell should have made a difference in sound, but it did not. Only by placing it inside the shell and the sound waves thus reverberating was a difference heard. I even touched the speaker to my microphone which did not result in any change in frequency or amplitude.
My advice for mounting these speakers is if you are particular about the sound, do not decide where you are going to mount them until you hook them up to a decoder or amplifier and experiment. The speakers are small and the mounting options are numerous (at least in my scale of choice, HO), but they will sound a little different in every spot you place them. Personally, I am going to try mounting in the gas tank facing down next.
I realized that these things are better, smaller, and cheaper than pretty much anything you can fit in a HO or smaller gauge locomotive. Having been motivated thus, I immediately set out to acquire a bulk amount of those speakers and also make baffles for them. So in addition to my Soundtraxx speaker enclosures, I now have a sugar cube speaker/baffle kit available on my ebay store.
http://www.ebay.com/sch/jond5/m.html?_ipg=50&_sop=12&_rdc=1