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Speaker Sound Holes

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  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 12,118 posts
Posted by wjstix on Thursday, July 24, 2008 2:05 PM

Well it's somewhat like a speaker for a stereo system, the wood enclosure behind and around the speaker helps focus the direction of the sound. If sound is coming out both sides of the speaker (like if you didn't have an enclosure) the sound waves kinda cancel each other out and result in a thinner, tinny sound. An enclosure eliminates a lot of that problem.

In a model, if you have the speaker and enclosure set so the sound only comes out thru the bottom of the engine, rather than some of it leaking from the top and coming out the bottom, it also helps the sound quality because it helps eliminate that cancelling out situation. I had one diesel engine where I had the cab side windows open, I found when I put glazing in the windows the sound quality increased because sound apparently was leaking out the cab windows!!

Stix
  • Member since
    August 2004
  • From: Amish country Tenn.
  • 10,027 posts
Posted by loathar on Wednesday, July 23, 2008 11:46 PM

Thanks all! I guess what was throwing me was looking at pics of an SD 60 installation. The shell had open (see through) fan grills and the guy placed the speaker against them facing down.Confused [%-)] The more I read about it though, everyone says they sound better facing down and reflecting off the track/roadbed than just blasting up through the fans into the air. Guess it pays to read and ask questions before breaking out the Dremel.Wink [;)]

I'm attempting my first sound install in a standard Bach F 9. Plenty of room inside. Now I have to decide if the 28mm speaker is good enough or if I should spring for the 20x40 rectangular speaker. I've also read that putting some poly fiber in the baffle helps cut down on bass distortion. Anybody try that?

  • Member since
    October 2004
  • From: Richmond, Texas
  • 393 posts
Posted by RDG1519 on Wednesday, July 23, 2008 3:35 PM

I placed a speaker in the long hood of two ATLAS RS-3's facing down but on one I drilled about ten thousand holes in the fan grid, on another I placed it facing down no holes. Both sound the same. If you are worried about volume try first before drilling holes. I have to turn the volume down on every one I own so far.

Chris

Great grandson of John Kiefer, Engineman Philadelphia and Reading Railroad, 1893 to 1932
  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 12,118 posts
Posted by wjstix on Wednesday, July 23, 2008 1:37 PM
To an extent, the more the sound is enclosed, the better the bass response will be. I usually put a speaker inside a switcher or road switcher facing down towards one of the trucks, there's enough room for the "sound to get out".
Stix
  • Member since
    August 2005
  • From: S.E. Adirondacks, NY
  • 3,246 posts
Posted by modelmaker51 on Tuesday, July 22, 2008 11:48 PM
Generally, if the speakers are mounted face down there's enough space around the trucks for sound to get through, this of course depends on how much space is occupied by the weight or frame casting. Some P2K's would definitely be better with the speaker firing up through the rear cooling fans, but they're already open. What engine(s) are you talking about?

Jay 

C-415 Build: https://imageshack.com/a/tShC/1 

Other builds: https://imageshack.com/my/albums 

  • Member since
    August 2004
  • From: Amish country Tenn.
  • 10,027 posts
Speaker Sound Holes
Posted by loathar on Tuesday, July 22, 2008 10:51 PM

Is it really necessary to drill sound holes for your speakers? I know it's EZ to do in a steam tender, but my diesels will be another story. I've seen people put etched fan grills in and point the speaker up through them. I'm not up to doing that though. I've seen them mounted in the shell point up. I've seen them mounted to the frame pointing down. Is there any rule of thumb? Any good sites with pics showing speaker installations?

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