Large Scale Central

Stack Speakers

Electronics Power and Sound
#1

One of the most annoying things about sound-equipped steam locos is hearing the chuff and other engine sounds coming from under the tender. I have solved this problem on my Bachmann Shay and Climax locos by adding a second speaker in the stack.

Of course this negates the possibility of using the smoke units, but I never use them anyway. My imagination works much better.

If you want to try out a stack speaker, it’s a simple and inexpensive way to get a tremendous improvement in the sound. Here is how I did it:

I used the optional diamond stacks on both locos to allow using the largest possible speaker. The speaker is a 50mm diameter, 8 Ohm, 5 Watt unit. Here’s a front and back view and a link to the speaker on Amazon.

Amazon link to speaker

Just for comparison, here is the new 50mm speaker (right) beside the original Bachmann Climax speaker (left) that goes in the bottom of the fuel bunker.

I began by removing the top portion of the diamond stack. The two parts are glued together with the standard Bachmann plastic adhesive and can be easily pried apart.

I soldered leads to the speaker and ran the wires down through the stack. I use quick disconnect pins so that I can easily remove the stack if needed. I placed a bead of silicone caulk around the rim of the speaker and dropped it into the lower part of the stack.

I stuffed a small plug of fiberglass insulation into the bottom of the stack. This makes the lower stack a sealed speaker enclosure and intensifies the amount of sound from the top of the stack. You can also leave out the plug and let the sound behind the speaker reverberate in the smoke box. Try it both ways and see which effect you prefer.

I reattached the top of the diamond stack with a semi-permanent adhesive (Ailene’s Tacky Glue or equivalent) just in case I ever need to replace the speaker.

I ran the speaker wires through the boiler and connected them to the sound card. Some sound cards can support two 8 Ohm speakers in parallel (like the Phoenix P8 in my Shay) or have additional outputs for a second speaker (like the QSI Titan in my Climax.) The big advantage with the QSI is the ability to direct different sounds to either speaker or to mix them in any proportion between the two.

Fire it up and listen to the chuffs coming out of the stack! I think you’ll like the effect. My next experiment will be with smokebox mounted speakers for my locos with straight stacks. I’ll let you know how that works out.

Bob

#2

Bob, I’ve got a smokebox-mounted speaker in my Climax. At only 1" diameter, it’s not got a ton of bass to it, even with an enclosure, so I balance that with the 2.5" speaker in the bunker. (QSI Titan has 2-channel outputs, so you can balance sounds to one speaker or the other.) Still, it does sound better close up to hear the chuffs coming from the stack. I’ve been thinking about doing something like that with my other steamers whose boilers are large enough for a decent-sized speaker and proper enclosure. (That’s the key!)

Question - on your installation here, is the 2" speaker the only speaker in the locomotive? If so, how does it sound for bass relative to a more “traditional” tender-mounted speaker? If it’s not, are you running the 2nd speaker in series for 16 ohms total?

Later,

K

#3

Kevin,

I have two speakers in both the Shay and the Climax. The Shay uses an Airwire G3/Phoenix P8 combo with a 3"diameter QSI hi-bass speaker in the fuel bunker and the 50mm stack speaker. The two speakers are wired in parallel.

The Climax uses a G-wire/QSI Titan combo with the stock Bachmann 2 1/4" speaker in the bunker and the 50mm stack speaker. I have the chuff directed about 80% to the stack and 20% to the bunker.

Bob

#4

Bob, I see you have discovered Aleens Tacky Glue, great stuff!

I drilled a hole between the cylinders and faced the speaker down. That allowed the retention of the smoke unit, and the sound is still pretty close to the stack.

It also allowed a larger speaker with an enclosure.

Greg

#5

I just re-did my Bachmann K-27 with a new decoder, putting a 3" (?) speaker in the boiler; hot-glued facing forward just behind the smokebox, so the boiler essentially creates a long speaker tube enclosure. (Sorry, I forgot to take a picture. It was late and I’m on cold medicine.) I also upgraded the tender speaker to a 3.5" speaker. Soundtraxx Econami decoder, so both speakers are wired in series, playing the same sounds.

Yeah, I think I’ll be adding boiler speakers to more of my locos now. Dangit, another project!

Later,

K