Hi everyone. A friend recently let me know that Digikey had started carrying a new line of small cell-phone type speakers from a company called Soperton, Inc. including an 8mm x 12mm. I've been on the lookout for an OEM 8x12mm speaker for a while, because this is an ideal size to mount in an N-scale narrow-hood diesel. Both Star Micronics and Knowles Acoustics used to make them, but they are no longer available to the retail market (unless you want to pay for a custom run of 2500 units). I purchased a couple of the new Soperton speakers, and decided to do a comparison between it, an 8x12mm "sugar cube" speaker available from Streamlined Backshop in Indiana (other DCC dealers also have variations of these 8x12mm sugar cube speakers) and a Star Micronics 8x12mm from a "stash" that I bought a few years ago when they were still available. The comparison was done using an ESU LokSound Select Micro sound decoder with sound file #73436 - the EMD 567C V16 non-turbo prime mover. Each speaker was mounted in a sealed enclosure with an internal volume of about 550 cubic mm. In the case of the Streamlined Backshop speaker, the speaker was mounted face-down in the enclosure, as is correct for this particular application. The other two were put face-up in a custom enclosure made from .030 styrene. I used the factory default volume settings for the LokSound. Here are the results: All three of these speakers sounded excellent for their size, IMHO, and I can't really tell any significant differences in sound quality. All of them would be ideal for a narrow-hood diesel sound installation. I'm impressed enough with the Soperton speaker that I will order a couple-dozen to have on hand. John C.
Nice comparison, John. Without doing a full spectrum analysis, I would say they are "the same". It is possible the Star had a bit less bass, but that might be the styrene enclosure not being quite as sealed as the other two.
John, do you have a recommendation for the depth of a speaker enclosure? Would the enclosure you made be suitable size-wise for mounting in a locomotive? Tiny is good for mounting, but I imagine too tiny would compromise sound quality.
Funny you should ask. While playing around with my 8x12mm speakers, I decided to do a test of the speakers with two different enclosure sizes. Streamlined Backshop makes two different enclosures: one that is 3mm deep, and a "double deep" enclosure that is . . . you guessed it, 6mm deep. So I tried both (with their speakers). In addition, I built two enclosures around two of my Star Micronics 8x12mm speakers. One of the enclosures used .250-wide (6.3mm) by .040-thick styrene strip with an .020 stryene bottom; the other used 5mm-wide by .040 thick strip with the same .020 bottom. The larger enclosure is about 6.8mm high; the smaller one is about 5.5mm high. In the case of my home-built enclosures, the internal volume is roughly 6.3mm x 8mm x12mm (approximately 600 cubic mm) for the larger one, and 5mm x 8mm x 12mm (approximately 530 cubic mm) for the smaller one. The actual internal volume is a bit less, because the speaker itself takes up some space (but you don't lose the entire speaker width - you only lose the width in front of the diaphram and any solid parts, like the sides and back plate). In the case of the Streamlined Backshop enclosures, the smaller one probably has a floor depth of about .7mm (it is 3D printed, and I think this is about the smallest thickness dimension you can use). So let's say that the smaller enclosure has an internal volume of 2.3mm x 8mm x 12mm (about 220 cubic mm) while the larger one would be 5.3mm x 8mm x 12mm or about 510 cubic mm. The only problem with this larger enclosure is that the overall height with the speaker is about 8mm, and that's too high for most N scale diesel installations - as I note below, about the best you can hope for is something on the order of 6.8mm overall height, and that's only if you mill down the frame where the speaker goes as much as possible. Here are the results of my experiment: I think that in order of sound quality, you have the SBS "double deep" enclosure and my Star Micronics in the "larger" enclosure pretty much tied, followed by the Star Micronics in the smaller enclosure, followed by the SBS in the small enclosure. I think all four are "acceptable", but the small SBS enclosure produces sound that is noticeably "thinner" than the other three. My "smaller" enclosure is a bit thinner, I think, than the larger one, but I don't think you lose a whole lot going from my 6.8mm high enclosure to my 5.5mm one - not nearly as much as you lose with the smaller SBS enclosure. In my view, this experiment shows that you should try to get as much internal volume in your enclosures as is possible given space constraints. I'm working right now on putting sound in an older Atlas/China GP9 chassis, and by grinding the front of the chassis down as much as possible, I can use an enclosure that is 6.8mm high (this is an enclosure made from .250-wide styrene strip for the sides with an .020 styrene bottom). This 6.8mm height is the absolute maximum I can get in most hood diesels by grinding down the chassis; I've typcially used a similar overall height (about 6.5mm) in my RS11's and SD9's. If you don't want to do all the chassis grinding, you can get away with an enclosure that is 5mm high overall, which would mean 4.5mm sides with an .020 base and an internal volume of about 430 cubic mm. The sound won't be quite as good, but should be decent. In fact, this is about the size I used in my RS3 installation, which sounds pretty good once the shell is on and the sound reverberates inside the shell. Here's a video of that installation: John C.
John, thank you for that comparison. I have several RS3, RS11, and GP7 I would like to install sound. I would prefer not to mill the frame but will if I have to. I found a supplier on Shapeways that I will follow up to see what he can build. If I spec the enclosure for the larger volume I believe I can easily trim it down smaller. I have admired your various 4 axle installations. You have shown what is possible and provided excellent directions.
If you are planning on using the Soberton (I just realized that the manufacturer's name is "Soberton" with a "b" and not "Soperton" with a "p") 8x12mm, here is a 3D printed enclosure that was designed specifically to work with that speaker, with an overall height of 6mm: https://www.shapeways.com/product/5L4ZXWA28/8x12-soperton-encl-4pk The internal volume of this enclosure is about 5.3 mm (6mm less the thickness of the base, which is .7mm) x 8mm x 12mm = 508 cubic mm (not counting the loss from the "hard parts" of the speaker). The speaker fits on a "shelf" inside the enclosure and there are dimples on the outside of the enclosure for drilling holes for speaker wire exit. I've ordered a 4-pack of these to test them. In theory, you should be able to put a thin bead of gel-type CA around the shelf, feed the wires from the speaker through a drilled-out hole, drop the speaker on the shelf and wait for the CA to dry, giving you a sealed enclosure (you might have to use a dab of CA to seal off the wire hole, too). Once I get these, I'm going to do another video test with this particular enclosure. It's overall dimensions come out to 6mm high (since the speaker fits inside), by 9.6mm wide, by 13.6mm long. This should be a relatively easy fit for a GP7/9 or RS11 chassis, although some milling will be necessary. For the RS3, you'll need something with less height, and you can't really sand this one down from the top because of the shelf for the speaker. John C.
John, I appreciate all your hard work and testing of the various speaker types, and enclosures. Once the new ESU decoders are available, are you thinking of setting up a side business to install sound in locos for folks who don't have the tools or expertise?
Hi Peter. I might do a little bit of this. I officially retired from the University of Illinois in May (I am now officially the Albert E. Jenner, Jr. Professor Emeritus - the "Emeritus" part being the key!), and might have a bit more time to do these sorts of things, though I'll still be teaching some. I ordered a small milling machine yesterday which in theory will allow me to more easily mill frames down for the speaker enclosure. It also, in theory, should allow me to more carefully sand down the inside of a shell if I need to do that for a particular install using the current ESU LokSound decoder. I intend to practice for a while on my own stuff, and then I'll see how comfortable I feel about working on other people's stuff. I'm not sure how much of a market there would be for this, though, because it would be expensive. The current ESU LokSound Micro runs $80; add another $10 for a speaker and enclosure, another $5 or so for LED's and dropping resistors to do front and rear lights, and another $5 for some tantalum keep-alive caps, and you're up to $100 just for parts. Now throw in a reasonable labor charge (say $25/hr for a 6-hour project from start to finish) and you have a $250 minimum ticket for installing sound (I haven't checked on what 3d-party installers charge; I'm just making estimates off the top of my head based on my experience in doing my own units; I'm hoping that the milling machine will make things go faster). I'm not sure how many folks out there are really interested in investing that kind of cash in an after-market sound installation. But . . . I might do some if there is demand and I get comfortable enough with my milling machine to work on other people's engines. Right now, I just don't want to be responsible for other people's stuff; but I've learned over the years that saying the word "never" will make one a liar in short order . John C.
John, I have enclosures and speakers on order. Is there a reason why some speakers get mounted with the wires on the outside vs the inside? This will be my first foray into exploring the why's and wherefores of sound. I don't have a mill but I do have more than a few files and dremels. Do you have a suggestion for which 4 axle locomotives are easiest to install?
Remember that all these speakers were originally designed for cell phones or tablets. Most of them (actually, all of them I've seen other than the Soberton) have "spring" clips that are the speaker wiring leads. In their original application, the speakers would have been placed face down in an enclosure, with the spring leads on top, touching circuit board traces. This is how you'd do it to manufacture a million iPhones or iPads - no soldering; just a robotic arm placing the speaker on the lower half of the enclosure, then slapping a circuit board on top of it. When I started using these speakers for sound installations in N scale diesels, I made custom enclosures out of styrene that "wrapped" around the speaker, and preferred to have the speakers face-up, with wires coming out of the enclosure. I'm always worried about having exposed solder joints, even if there really isn't much chance they would contact anything metal and create a short. So there's no "right" or "wrong" way to do this: speakers by their nature emit the same sound wave from the back side as they do in the front. The key to best sound for a conventional diaphram speaker is to make sure that one of those waves (either the front wave or the back wave) is fully enclosed and sealed off from the other. As for which locomotives to start with - I'd probably start with a high-hood unit, like an SD9, GP7/9, RS-11 or something like that. The reason for this is that with a high-hood, the component layout is pretty straightforward - the speaker goes on the shorter "shelf" of the frame, and the decoder goes on the longer shelf. You have to mill down parts of the frame to give enough depth for a decent-sized speaker enclosure and for enough depth to mount the decoder. Once you've done a couple of high hoods and have a feel for how the components fit together, you can tackle a low-hood, which generally requires a bit more ingenuity in how to place the components since you can't use all of the front "shelf" (because part of it is up against the front of the low-hood part of the shell). I've posted "how to" threads both here and on The Railwire forum about how do to an install in an RS-11, a GP7/9, an SD9, a GP30, an RS-11, and even a VO-1000 switcher (not the one you should start with). An SD9 is an ideal starting place, because the frame has more length, and you won't be stressed about finding room for your component layout. Here's a link to a thread on The Railwire that lists my various installation threads as links at the bottom of the first post: http://www.therailwire.net/forum/index.php?topic=31981.0 If you visit some of the links at the bottom of the first post in this thread, you'll see how I did my installations (many of these installs I also posted here on Trainboard - if you do a search on posts by "jdcolombo" you'll find them). And if you have questions, send me a private message or just e-mail me directly at jdcolombo at gmail. Always happy to help folks work through what they are doing. John C.
Thanks, John, for the pointer to railwire. I have read all your threads here. Having a pointer to your installation threads is very helpful. It makes sense that the speaker produces equal sound out of either side and the mounting choice relates to the exposed wiring. I have enough information now to be dangerous.
