Thank you Bob!
Thanks for calling out this new TB module.
That speaker is a brute! It has a bit lower bass response than the 1828SD module I’m installing in P&D F units. Because it is 5mm narrower, I might be able to fit one in an N&W 4-8-0 tender. Must make a wood mockup for space planning.
Sorry dear readers, I’ll try to recompose myself. It is just that I’m still looking for my lower jaw somewhere on the floor.
Well done, Mario! Those are awesomely gutsy chuff sounds. Crowd pleaser, indeed!
Watch out near maximum volume because the Lionel sound board may not have been designed to drive a 4 ohm speaker at full volume without distortion (some distortion was audible after you cranked up the volume potentiometer.) If Lionel designed the sound board for 8 ohm speakers it might ruin your day over time. Take an ohm meter to the Lionel OEM speaker and see if it is about 4 ohms or 8. That huge TB speaker module can take pretty much whatever an in-form-factor decoder can throw at it without complaint. The decoder may not. If that is the case, add a 4 ohm 1 W resistor in series with the TB module and you should be good to go.
Anyway, that is seriously delicious steam sound!
O-scale. There is no substitute!
Not even Porsche.
Amazing sound, Mario. Makes me wish I was in the steam era. Good work.
Thanks for sharing your journey with us.
What you don’t see is the 4ohm neodymium laptop speaker tucked in under the electronics and on top of the gear box (which I rebuilt to eliminate slack) that points down and out of the bathtub shell. This small speaker adds what the Tang band cant; high end nuances to the whistle and chuff, which now sound like their coming from the steam chest. The human ear really can’t tell directionality of low frequency sounds, like the chest-thumping speaker in the tender.
Even with an iPhone 7+ and 4K camera, you really can’t tell how low it goes.
Now you can tell how low it goes…
Finally works with the shell on, too.
Spectacular sound, Mario! I imagine folks in the club were wowed when they heard it run on the layout.
Alas, I measured my N&W 4-8-0 tender and the T1-1828 won’t fit due to the way the bottom of the brass tender shell is reinforced. Looks like I’ll have to drop back in size to a 1931 module.
The Loksound V4L decoder has two speaker outputs (presumably it uses a class-D stereo amplifier chip) and I’ll see if I can install a second speaker, possibly a 1925SB loose driver, if room in the smokebox permits.
When you get the 1931 module in the F-unit fuel tank running, please let us know.
I recently bought an inexpensive but individually-calibrated external iPhone microphone for sound measurements from Parts Express, a Dayton Audio iMM-6. Currently I have the same analyzer app that you have.
Now I haven’t yet set up an amplifier to drive a TB speaker with pink noise, to measure the speaker frequency response in an install, but like you I did measure the SPL of a TB speaker driven by a Loksound decoder.
In this case the speaker is the huge 1828SD module, which I can fit firing up, behind the cab, in P&D F3 units after milling a hole through the brass frame, with a V4L decoder loaded with the 76311 EMD 567-16 BC (FT) file. So this is a measurement of the ESU file + speaker + install Sound Pressure Level (SPL.) It is not a system frequency response plot.
It is known that ESU adds some bass boost to many of their diesel files. But I didn’t expect to get this much bass down at 70 Hz. The TB data sheet says the speaker response alone drops about -8 dB at 70 Hz.
Here is an SPL plot of the decoder+speaker+shell running at idle, measured from 1 foot away, a common viewing distance on the A&O.
In LokProgrammer one can assign a throttle function to “Fade out sound.” By assigning it to a “Not function key” I can set a low, default operating session volume and a separate “bring down the house” loud volume for demos during clinics.
By the way, a bass peak at about 70 Hz corresponds to a 2-stroke V16 engine idling at about 260 RPM.
I was digging around the Tang Band site tonight, looking for some specs. I stumbled onto a speaker module that I have not seen before. It may be applicable to carbody style locomotives.
The module isn’t all that much shorter in height (about 8mm), but it is significantly narrower than the 1828SD module (about 17mm). The trade-off of course is in the bass response. 95 hz in the new speaker, 75 hz in the 1828SD.
I really need to send them an email requesting the rectangular modules with a max width of 1.25" or possibly even 1.375".
Parts Express has been selling the T1-2025SC for for a while. Both in width and height it might just fit vertically in a single-tower P&D F-unit, although the front motor mount may require modification if the cab detail kit is installed.
That said, there would be little clearance between the bottom passive radiator and the brass frame. The P&D shell is 1.65" from frame to outside edge of the roof while the 2025 is 1.47" tall. The roof has an arch shape so it might be possible to take advantage of that for a little more vertical clearance.
Since you mention a max width, TB has a T1-1925S module that is only 29mm / 1.14" wide. That’s my go-to speaker for O scale narrow hoods like GPs. They have a smaller module, the T0-2008S at only 24mm / 0.95" wide that I use in Atlas SWs. Both of these are in stock.
I’ve got both the 1925 and 1931 on hand. I’ll be using one or the other in my sw1500 project and other hood units (the sw1500 style radiator isn’t as deep as the early sw’s like you model).
I thought the 2025 might be new as I hadn’t noticed it before and I only recalled you talking about the 1828, which would require frame milling and several other mods to fit into an F unit. It sounds like you already have it covered.
Thanks for the heads-up about the 2025. Frankly if the 2025 had been stocked some years ago, I might have initially purchased them. But because I already have in stock 1828s, I’ll intend to follow through with planned chassis/frame/underframe modifications.
All the best!
Wow Bob. That is telling isn’t it. It isn’t overly boosted so I imagine it would sound really good. Thanks for sharing! This is getting good
There was discussion earlier in the thread about the viability of the Tang Band 1931S module for use with hood type locomotive shells. I had been hoping to use the 1931 in my switcher project based on an Atlas mp15dc, but there was definitely going to be some grinding or cutting needed to make the speaker fit without causing displacement of the shell. I finally bit the bullet and started modifying parts, knowing that I might mess up the speaker module or breach the enclosure while removing material. Here are the results.
My goal was to remove some material from the sides of the speaker module and also from the inside of the Atlas shell, making the speaker narrower and the shell wider. The speaker enclosure began at about 1.420" width at the top face. The sides are generally slightly narrower than the top, but there are ribs spaced along the sides that match the width of the top face. The Atlas hood began with a width of about 1.372", with a wall thickness of about .085", but there is a problem where the recess for the hand brake on the left side protrudes into the cavity behind. The back side of the hand brake recess can not be thinned, so most of the material was removed from the right side of the shell.
I started out on the speaker module with a bastard file applied to the sides. Whatever type of plastic is used is pretty tough. I wasn’t making much progress, so I switched to a Dremel with a cutting tool. I was hesitant to do this as I was worried about controlling both the shell and the Dremel, and not slipping up and cutting a big hole in the speaker module. A mill would be ideal for this operation, but I don’t have one, so the Dremel would have to do. Taking light cuts and being as firm as possible, I was able to remove material from both sides of the enclosure to the point where it now measures about +/- 1.395" along it’s length. I was even able to remove additional material in the area of the hand brake recess, which falls between the primary driver and the radiator section, so that the width is about 1.375". I didn’t try to remove any more material anywhere else as it wasn’t required for my use and I didn’t want to risk an error. But further experimentation might reveal that the enclosure could be narrowed to 1.375" along it’s entire length. I’ll cross that bridge when I need to. I cut the end mounting tabs off with a compound miter saw. This might not be necessary in a larger locomotive, but my switcher will be a tight fit so the tabs came off and I will use double sided tape for attachment.
On the shell, I cut to the chase and went straight to the Dremel. It was easier to be confident as I knew the wall thickness of the shell, where on the speaker I would only know if I had gone too far after it was too late. Taking light cuts and checking often, I removed about .028" of material from the engineer’s side of the shell. The open width inside the shell is now +/- 1.400" in the area where the speaker will reside. With the speaker installed, I put a straightedge along the sides of the shell to check for any bowing, and was pleased to see that the edge lay flat along the length of the shell.
My only concern now is whether there will be vibration issues if the speaker enclosure is touching the shell. I won’t be able to tell until I get everything wiredc up and tested. Fingers are crossed. The other issue is that even with the mounting tabs removed, the 1931 eats up a lot of space inside the shell. Coupled with the Loksound L motherboard and decoder, it makes things pretty tight in there. I’ll deal with it for what I hope will be awesome sound.
I would like to think that based on the results here that the 1931S module could be made to work with other hood type locomotives. I will certainly be trying the same installation on another Atlas loco in the future. I would like to be able to modify the speaker with more precision, ideally with a mill. I’d like to have cleaner looking results, only because I’m compulsive, even though nothing will be visible… And I may discover that the sound isn’t satisfying or there are other issues once everything is tested. But for now I’m pretty stoked with how things turned out.
I thought there was plenty of room inside my P&D Fs to put it in above the motor, wrong! So I made up 3 mounts tonight. I replaced the step screw with 1" long ones and slipped 1/8" tubing over them high enough to clear the drive. Various other styrene shapes leftover from other projects completed them. Used canopy cement to hold in place and just a dab where the rod touches the chassis. Canopy cement is great stuff if you have never tried it before.
Very interesting, and a nice clean install. I didn’t expect that a 31 would fit there; obviously I was wrong. If you have not yet assembled the shells, may I ask how much vertical clearance there is from the peak of the round speaker cone to the bottom of the roof?
I haven’t used canopy cement. Can the 1" screws can be backed-out to remove the speaker mounts for drive train access and repair?
Disclaimer: I’m not an audio engineer, nor do I play one on TV.
So… I ordered a calibrated USB microphone from Parts Express and purchased trueRTA software. I don’t have access to an anechoic chamber like those used audio experts, but I do have a glass desk top, which might substitute for the track and roadbed.
My first victims are a Tang Band 1931S module and a QSI 2.077" “High Bass” speaker I built into a Red Caboose GP9 fuel tank. Both were held above the desktop at proper heights they would be sit above the rails.
Subjectively, to my ears the TB module had more bass, but was not as loud. It sounded better being driven by a LokSound V4 decoder. Confirmation arrived in the frequency response plots.
The green trace shows the TB 1931, and yellow, the QSI. Note that the QSI is louder, but the TB has a flatter bass response. One can click on the plot to enlarge it.
Here are photos of the measurement conditions.