That Rectangular speaker comes manufactured in a baffle therefore another baffle is not needed. I know Because I have the exact same decoder and speaker. The the sound is great. So much so I had to turn down the volume because it was too loud.
The MRC speakers come in an enclosure. I've used several with good results.
On my hood units (Geeps) I use the mini-oval speaker and enclosure, and put it in the cab. That way I don't loose any weight. The shell also acts as an echo chamber.
I am not concerned if there is no cab interior.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
I sometimes use bird shot for weight.
I also have some metal that melts at the temp of boiling water. I pout this into molds made of styrene or old Lego's.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
You might give Athearn a call to see if you can't buy a new rear weight. Then replace the speaker with a 16 X 35 MM speaker.
I think the next DCC sound installation I do I will used simple round speaker cones and fabricate any encloures/baffles if I need them. I really didn't like removing the weight from my SD40. I had slowly reduced the size of the weight more and more trying to fit the enclosed speaker until I relaized that I had to eliminate it totally. Now I wish I could find an original replacement weight and install a plain speaker. This was my first DCC experience, so it's part of the learning curve :)
It looks very much like what I did with my Athearn SD40...removed the rear weight and located the enclosure with speaker in its place. I haven'tt got my layout wired up for DCC yet..worjking on that phase next...but Im eager to hear that SD40 roar to life :) Hopefully we'll get a rainy weekend soon and I can do that!
There is no need to have the shell sealed to the chassis. What we need is to seperate the front of the speaker from the rear of the speaker with as much distance as possable.
The speaker mounted to the under side of the grills will do this. The sound waves from the front of the will exit through the grill openings. The back side waves will exit through any and all holes in the chassis.
I have installed many just in this way. The sound is very good.
Here is another from the Google search using what looks like the 16mm x 35mm in a baffle. Don't know how yours compares for the frame.
http://www.modelrailroadforums.com/forum/showthread.php?t=12104
Take a look a the below link I did using a Google search for athearn sd40 tsunami install. Scroll down the page.
Looks like a 28mm round speaker firing up.
http://www.railfanreading.com/Layout/Prototype/KCS6106/KCS6106.htm
The MRC speaker IS inside the 16x35 enclosure. I bought it on the advice of the fellow at the train store, but now think i might have done better to have bought an un-enclosed speaker, fastened up under one of the open fan grills. If i did that and blocked the other open grills, or even somehow blocked the underside of the speaker cone, I could hahe retained the rear weight. I think if I run into a similar situation I might try that.
Some with the speaker in the fuel tank have reported metal stuff, spikes for one thing, being picked up from their layout. I believe there was a thread about that in these forums not too long ago. Some use a grill made from a coffee filter to protect the speaker and also run a car with a magnet attached to the bottom of a car to check for any metal particles in the roadbed.
Go to the below link and learn all about DCC sound. Store the link in Favorites. You will need it.
http://www.mrdccu.com/
He explains the Tsunami sound very well but it pretty much is the same for other decoder brands.
Below is an example of a 16mm x 35mm speaker in a styrene baffle I use in a Spectrum 44 to and 70 ton.
The shell is only 16mm wide inside.
My Stewart VO-1000 diesels do not need the baffles and they have the same 16mm x 35mm speakers. The speakers fire down though the opening in the frame which is over the trucks.
My BLI F7 nd PCM F3 have 28mm round speakers and do not need baffles. The spekers fire down though the opening in the frame which is over the trucks.
I am unsure about the MRC speaker. I think that it is in an enclosure. That is where the OP is running into problems with room. A 16 X 35 MM speaker (without enclosure) would fit, if it were glued to the underside of the grills. Seeing as that they are open, the sound waves would exit through the grills. The shell of the locomotive becomes the enclosure. There is no need for an enclosure. If by some chance the speaker will not cover all of the fan grill openings, these need to be blocked off with plastic or styrene plates. This will keep any sound waves from sneaking out.
A baffle is an airtight enclosure for either the back or the front of your speaker. It is necessary for good sound volume and quality. Baffles can be obtained from speaker suppliers or you can make your own out of styrene, etc.
Joe
Hmmmm...ok...but why do I need a baffle? Is the sound too crisp wihout one? What would work well...maybe cellulose sponge, or maybe cotton gauze?
I used the Tsunami TSU-AT1000. The circuit board was perfect, it fit right in place. I gradually reduced the size of the rear weight until the speaker fit, but by that time there ws so little left of it that I just left it out completely.
Yes, the fan grills are opened, and the speaker cone fits perfectly directly under one of them so it seemed a good location for that reason as well.
I hope to get my layout wired up soon with the Digitrax DB150 and DT400 throttle so I can try it out. Thanks for your input :)
I have several loco's (8) with the speaker in the fuel tank (Factory installed) and don't have any problems with them.
Springfield PA
Which decoder did you use- A TSU-1000, the GN-1000 or the At-1000?
I have used a 16 X 35 MM speaker mounted over the rear weight facing down. I machined off the top of the weight so when the speaker was mounted to it, it was the same height of the original weight. Then I openned up the weight so the sound could come out the bottom. There was still a weight in the rear.
Are the fan grills open on this loco? If not, facing the speaker down like I said will give you better sound.
Yes, I lost some weight, but I don't think that will efect the pulling power that much.
The typical location for the speaker is in the fuel tank. Sometimes there is already a spot milled out of the weight if the manufacturer offered it in sound. Otherwise you would have to mill it out yourself.
Has anyone installed a Tsunami sound card in an Athearn SD40?
I just finished installing one...and it wasn't like I had hoped it would be as far as being a good "fit" I had to totally remove the rear weight to put the speaker facing upwards out one of the fans. I used an MRC 16mmx35mm rectangle speaker..and there was no other place to fit it. That is going to cause loss of traction I fear. There was very little room anywhere in there. I hope it works out all right. I haven't wired my Digitrax control to the layout yet so I can't try it out just yet.
Would ovoe to hear some comments