Tang Band speakers

Pete -

When the round speaker gets too close to the top of the shell, a very strong resonance sets in causing frequencies ~1KHz and a bit lower to suddenly become a lot louder. It is possible that you might get a better balanced frequency response with a 1925 mounted much lower.

Here’s a quick and easy experiment to do. Enable drive hold, and fire it up. Now take the flat palm of your hand and hold it horizontally over the speaker. This simulates the top of the shell. Now slowly bring your hand down and towards the speaker. At some point, probably around 1/2 inch or so, you will hear an abrupt increase in high frequencies. I just tried this on my LokProgrammer with a 1931 connected. The emphasized frequencies sound almost like a steam hiss, perhaps accompanied by a loss of bass.

You might also try this with a 1925.

All the best.

Link to example video

Thanks for the suggestions. I’ve found the same symptoms you describe with TBs from 2008 up to 1942. The only way it seems to work is if you have almost all-grille above the driver, or at least 1.5" clearance in front of the driver. I’ve also had issues when I got the driver too close to the motor magnets.

One of my other C&LS RS 11s has the 1925, as do all my other locos. I do find the sound more open and relaxed with the 1925s but it just feels light on bass after hearing the 1931 and 1942. I do seem to be obsessed with trying to get more bass. Maybe it’s a fool’s errand. :slightly_frowning_face:

I’ve got a 1942 in that P&D F7B where the speaker can lay on its back in the middle of the floor thanks to the truck-mounted coreless gearhead motors. TBH that’s the only one where the bass still works pretty good with the shell on.

I did cut away the plastic under my MP15DC grilles and replace with black loudspeaker fabric which got rid of the hiss of the 1925s in them.


I think I’ll make this RS11 the last one I try to improve before I go back to the trusty 1925…

Hey Pete,
Bob and I had discussions previously about removing material from the sides of the 1931 modules. Bob then preceded to cut one open, which he chronicles in this linked thread. You’ll see that wall thickness runs about .078", so I would think that you could remove 1mm from each side and be safe.

I did something similar on the 1931 for my sw1500, but my efforts were with a dremel tool and are far less elegant than Bob’s machine work. However, the point is that I was able to remove a fair amount of material and not breach the module enclosure. Between narrowing the enclosure, and grinding away some of the shell thickness, I was able to get the 1931 into the mp15dc shell. You can see the results of that exercise in my sw1500 kitbash thread.

Now for a little thread drift…if I’d realized at the time that it was you showing slides at the beginning of the Chicago p48 meeting, I’d have made a point to say hello and introduce myself. Maybe next year.

I do have a question about the install you showed that night. I’m curious why you didn’t turn the truck mounted motors around and hang them off the mounting bracket cantilevered over the truck kingpin, instead of toward the middle of the loco? This would seem to address the truck swing issue you mentioned, and alleviate the need to frame mount the motors. Although now that I think about it, maybe there was an issue with the cab interior? Just something I thought of after the show.


Hi Jim,

Thanks for the update on removing material from the 1931. I’ll take another look at those posts.

It would have been great to meet you at March Meet. Maybe next time!

Re the motor mount, Jay does offer an “over the kingpin” version.

But in the end my combo of chop-nosed RC GP9s, the need to go round 36" radius, and have a cab interior made the chassis-mount version a better compromise. We did shorten the drive shafts quite a bit so the TB1925 can sit low down between the motors and facing up. I took the backing off all the long hood fans and the sound is decent at least.


Here is a short iPhone video (poor microphone instead of my Shure MV88, which I forgot) during the April 20 op session. The Alco C425 served at times as a helper engine up the grade from Union Gap to Linnwood. I was glad I endured the pain of installing 24 LEDs in this locomotive, including the white and red class lights. The engine still needs air hoses.

An EMD 567 Roots blower whine heard at the start of the clip came from Craig Linn’s beautifully-weathered C&NW chop-nose GP9 running on the point of this train.

Link to short video

I am new to O scale, I am wondering where you got that motor and drive parts (belt and cogs). I am trying to repower a few O scale Shay locomotives and I was considering using timing belts like that orange one, however mine will have to be about 2.5mm wide.

Welcome to O scale! The motors and drive parts in my locos came from Jay Criswell at Right-O’-Way.