I am going to experiment with a Soundtraxx DSD DSX sound only decoder set up as a stationary unit and wired via their suggested amplifier circuit (well, its a circuit needed to connect to an amplifier)and plug it in to my stereo/computer amplifier and subwoofers.
I tested the sample soundfiles for the DSX from the Soundtraxx web page, by playing them through my paired of 15" subwoofers and satellite speakers. It was pretty impressive. (The subwoofers [on the bottom] are my own design and play sound waves longer than a locomotive anyway...even if it is only Johnny Cash on the disc.) Seemed like I was standing beside the loco when it started up.
Does anyone have any experience using this little circuit connected to an amplifier as Soundtraxx recommends? If the sound through the decoder carries all the fidelity of the sample file on the web, and it is supposed to, it should be quite realistic.
- Harry
Yes, that would be just fine for general sound, background or ambient, albeit loud.
But I plan to put a subwoofer in the layout room with a satellite speaker as an experiment. The Soundtraxx DSXs are fully programmable decoders that are MU'd with the motion decoder of the selected loco. The definitive rumble from the subwoofers will match the startup and speed settings of the loco, and the satellite speakers will do the job for the higher frequencies, bell, whistle, dynamic brake fans, flange etc.
Very low frequencies are not very directional....a person can't really tell the point of origin...that's why you can put a home theatre subwoofer under the sofa etc.
It is an experiment alright....the bell and whistle etc. might not be directional enough to realistic from a stationary speaker, but at the fidelity I am getting in the test, it will be hard to beat in the layout room.
If you search this website, using my name and "sound" there's a book or two here already written on this subject, all except the circuit.
I think you can skip the circuit. I've plugged 8 ohm speaker outs directly into a pre-amp or mixer many a time and never seen problem one. Plug it in, bring up the amp gain slowly, and be ready to back off if things sound weird, I think you'll be okay.
If you're real worried, use a beater amp and speakers first time out.
Very interesting. I have been thinking about putting a sound system in the layout room as well. I would be interested to hear how you make out.
I would use a matching transformer circuit myself...just to make sure the different impedances don't eventually fry the decoder or the amp...
hmmmm....this is exactly the kind of thing I need to know for sure. Thanks Cacole. Soundtraxx support / return email seems non-existent (Digitrax reply time is excellent BTW).
I am going to phone them..
Anyone else have info on this low frequency possibly missing in the decoder sample?
Even the SoundTraxx Sierra G-scale sound decoder manual does not indicate the available frequency range, but just says that the largest speaker possible will provide the best bass response, and that a suitable enclosure is critical.
A look through the Mouser Electronics catalog listing of miniature speakers indicates that there is only one speaker from Kobitone with a response below 200 Hz, with most of them in the range of 200 to 450 Hz. The lowest (only one) is rated at 80 Hz, so it would probably be safe to assume that a decoder is not programmed at anything below 100 Hz.
Well, I'll let you know. This will be fun. When I start dialing in the active crossover and use a frequency generator I can see the subwoofers continue to move, but they drop out of hearing. If I turn up the volume, I can feel them moving!
The enclosures I built (on purpose) are of 1" medite and each has an 8 foot kd 2 x 4s for bracing. They weigh almost as much as I do...and I weigh a shocking amount.....
...but they transmit a lot of sound to the room and seem suited to loco sounds....not that I would play them that loud because it would not be realistic matched with the 1/87 perspective of the loco in front of me.
As I say, it is just an experiment.
Otis wrote:But I plan to put a subwoofer in the layout room with a satellite speaker as an experiment.
Anyway, I've posted this a zillion times. I was working on similar sorts of things. I was making my own crossover for in-loco multi-speaker systems. I needed data so I wrote to Soundtraxx and got the frequency response for their sound processors - NONE of them produce frequencies in the sub-woofer range (see e-mail below). So technically the sub-woofer should sit silent. If it doesn't then 1. It isn't really a sub-woofer or 2. There is some corruption or distortion of the signal introduced into or produced by your system.
The DSX is not a high fidelity unit. They are made specifically to work with tiny 1.25" speakers. They are engineered and produce an output signal accordingly.
If you really want high fidelity train sounds you need to get a high fidelity recording such as, possibly the best ever, "A Decade of Steam" (If you can find the vinyl version it was pressed with KC-600 audiophile grade vinyl). Some others not quite as good are "Journey to Yesterday Volume 1 & 2" or if you prefer diesel sound "First Generation Diesels" and "First Generation Diesels Volume 2". In my railroad sound collection I also have "The Rattel and the Roar!" - narrow gauge. "Greenboard South" - Southern RR steam. "Sunday Only" - CB&Q steam.
The sounds that come off these quality recordings are nothing like the stuff produced by today's sound processors.
----e-mail quote directly from Soundtraxx----
Our decoders work in the range of 1kHz to 25kHz. Somewhat on the high sideof the amp. Speakers that we use are small.Larry LarsenCustomer Service
Thank you for the response Texas Zephyr
That is what I was concerned about...website sample not being the decoder sound. Yes the subwoofers I tested with are truly subwoofers, but as I posted, I tested all the sound samples for the DSX from the internet website as a preliminary step....not the decoder.....that come next when my son brings up the output transformers from the city so I can make the little circuit. Also, the Paradigm active crossover coupled with my subwoofers enables me to dial in a range of frequencies, so I can bring in even the midranges to the 15" woofers...down to inaudible 15 Hz and lower....so I can make the most out of whatever there might be on the decoder.
The use of simple recordings, no matter how great the fidelity, does not have the ability to match the startup, throttle up, and ancillary sound effects of whistle, bell, flanges, brake fans etc. as the DSX does when it is MU'd with the loco on the track. I am not interested in background sound at the moment. I'll let you know what it sounds like after the experiment....if anyone is interested.
For near side start-ups, coupler tightening, and pullouts, we use the MRC Synchro Sound units, and dial them out of the sound mix as they disappear into tunnels on the far side of the layout.
Whistles, bells and some coupler crashes are CD quality digital samples triggered off the PC (via Superkeys and Winamp) through the same (Logitech 51. sub/satellites with 580 watts peak) sound system, by means of a small Behringer 12x2 mixer.
On reapparance of these trains on the near side, CD quality digital samples are triggered for bypass sound effects, which include not just the prime mover sounds but also the creaking and clanking for every car in the train.
We had to tweak the samples using a digital audio editing program (we use Cakewalk, but there are several free ones available online) for fade-in, total duration, spacialization (right to left, front to back) and fade-out rates, but the effect is stunning. Well worth the time involved match the samples to our layout and learn the lag between triggering the bypass sample and closest point of approach, to make the sound match the visual reality.