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Finding the low notes

2580 Views 15 Replies 11 Participants Last post by  jlinde
I am full of questions today and just posted one on the R/C board about extending the range of CSS by use of an external antenna. Here's a question about sound.

I've heard pretty good sound on the few G engines I've seen in operation, but there's one thing missing - the low notes. Anyone who's stood near a diesel engine has FELT the vibrations. But you're not going to get the low frequency vibes from a one-inch speaker. I'm wondering if it'd be possible to run the audio output through a fairly powerful amplifier into a subwoofer. Admittedly it'd be stationary, but low notes are non-directional - you can't really tell where they're coming from. It might be fun to actually feel the rumble of a diesel idling on a yard track.

It doesn't sound too hard to do. Would it be worth it?

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Funny you should mention that. This month there is an add in Model Railroader for a DCC sound system that works by sending sound to a series of speakers hidden along the layout (I assume indoor is what is intended). But I can immagine this working with those outdoor speakers hidden in rocks. The sound system is not in the locomotive per se but responds to the DCC signals somehow. If your interested let me know, I'll dig up the add.

Check the archives ... Rayman4449 had an arrangement where he turned the better part of a tender into a bass tube for some of his engines..... and remember you can get a lot bigger than 1" worth of speaker into most large scale engines! The trick is usually to seal up the enclosure well, and insulate around the box.

Additionally, you might try your "stationary" sound system with a microphone so that passing trains would make the area they were in "rumble" as they passed.... I've considered using an old reverb unit in a tunnel in much the same way (would also work for folks deciding to shout down the tunnel to see if they got an echo....)

Mostly, I'd take a look at some computer and personal music appliance approaches to delivering full spectrum music from small enclosures, and either imitate or borrow from that group, so you could keep the sound all "on board."

Matthew (OV)
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iPod accessories are another source of small speakers with wide range frequency responses.
No reason you could not fit in a 4 inch speaker and passive radiator in a trailer car. Some of the better sound cards put out 5 watts (?) or you could install a small separate amp (Ii have seen 11 watt ones around). Maybe not earth shaking but pretty good.

On another forum I posted the results of my experiment with "porting" the enclosure. I'm a semi-pro bass player, and while I'm not a speaker designer I have a lot of experience with speaker cabs. If you want good bass response and efficiency in a small enclosure, your best bet is to port the enclosure. Nearly all small bookshelf sized speakers are ported for exactly this reason.
I put a Phoenix sound speaker in the boiler of an aristo Pacific, and then drilled a hole in the backhead and inserted a brass tube as a port.

You can hear the result in these two files
First, unported


Second, with the port installed


Speaker design/porting is a science, and to really do it right you need the specs of the speaker and the interior volume of the enclosure. But my guestimate produced noticeably better bass response, which you can especially hear in the above samples if you have decent headphones or run the sound into decent speakers

This would be extremely easy to do in a steam engine tender--the port is just a tube made of cardboard or PVC or whatever, and it can face down

On a side note, this is probably the worst forum software I've ever used. It took me 20 minutes to post this and I still can't get the sound fiels to show up as clickable links. Sorry!
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You may find the following topic from the archives of interest.

Speaker rear enclosures make all the difference

Additionally, you may find this web site of interest.

FantaSonics Engineering
JackM, Gary Raymond had the same interest and wrote an article about putting a speaker in a box car that appeared in the Feb/Mar 1995 issue of Outdoor Railroader. He has the best sounding diesel rumble I've ever heard in a model. You might want to contact him; look for his ads for his wheels in Garden Railways magazine.
Long story shortened?: I have had an experience that may tell you something, but don't try (risk)it. I also am into sound systems and noted the lack of realistic rumble. I heard a Dallee system in a sd45 at the ECLSTS a few years back and thought it sounded good. I bought and installed it. It did not impress me. It sounded off. I have the 22w amp upgrade and no matter how I adjusted the volume it sounded distorted. I fried the original speaker just sounding the horn. I tried three different speakers, but the enclosure suffers (sd40 fuel tank w/ back opened through shell).
While going through this my G gauge MTH Challenger was sounding distorted. It later toasted the onboard amp.
I had hooked up a forth speaker to the dallee and thought I'd try it with the MTH. It was 8 ohms. The stock MTH says 4 ohms. It's a small KLH 911B home surround speaker. I put it on a flat car and when I hooked up the challenger, WOW!!! The frequency range, and the clarity, never heard any toy train sound so good. That MTH sounded digitally perfect thru all the frequencies. Then... the board's amp fried. Oh (shoot). Was it going anyway??
The enclosure made the difference. Well I had the best bass response I ever heard for those fleeting seconds...... It's fixed now and I don't have the kahunas to ever try it again. I have bought better QSI high bass speakers but they don't match that KLH, and I'm a JBL nut, or infinity, or polk, or.... You should have heard it. Maybe I'll add trucks, Joe
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My condolences to your wallet. I'll file your story away for future use when I have time to play with the rumble question.

Hello, all - I installed the QSI aristo system in my E-8 last night and was darn unimpressed with the bass response. I'm going to try and build an enclosure as described here but was wondering whether any one here had already installed an enclosure in this particular engine. Many thanks, Jon
Have an E8 with the QSI, the speaker sounds poor and pretty low in volume compared to my other QSI's... probably replace the speaker is first priority.

Also, Aristo often uses 1 watt speakers, QSI will overdrive a 1 watt speaker.

Regards, Greg
Thanks, Greg. My 3-year-old daughter and I installed an ad hoc enclosure cut from a plastic cup (of the carry beer around Key West variety) and the results were noticable. Much nicer bass response. Of all the modifications I've performed, this had by far the best cost-benefit ratio!
I have not even looked at the speaker, I guess I should.. is it round or oval? I'll probably order a couple, have a second E8 coming in a month.

Regards, Greg
Hi, Greg - the speaker is oval. Cheers, Jon
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