Can someone translate this for me please?

[James90012]

I have a HJ 47 with legomanbiffos sound chip - I have sealed the speaker with blu-tac and the result was a much improved sound. I did a Google search and I found this link - http://www.dccconcepts.com/index_files/DCCsoundinstalltips.htm - but I don't understand what this paragraph is telling me to do:

 

 

''USE the BIGGEST BOX YOU CAN.

That’s usually the body shell itself. A flat “baffle” along the axis of the loco from side to side, sealed at the ends if possible (and using the body itself as the other three sides) will be the most effective box you can build… bigger is better with diesel speaker installs, as we really do want to get the depth and “mass” of the sound as big as we can, because a big diesel gives off huge energy which takes a LOT of reproducing. No need for a perfect shape if its hard to do - just use BLU-Tack or modelling clay/Plastiscene to fill any gaps.''

 

I get it's suggesting sealing the body but how? where? Thanks in advance.

 

P.s. I have a 23mm large round speaker facing downwards over the gear towers - is this the best set up?

[trisonic]

Sounds like it. Only he would know for sure. I wonder how he "treats" the bottom of the body where it meets the chassis? Rather than just a sealed box a true "tuned" bass reflex system would seem to be the answer with small speaker installations (somewhat similar to what Bose do).

 

Best, Pete.

[legomanbiffo]

By sealing your speaker you achieved 'a much improved sound'. A similar improvement can be gained by increasing the cubic capacity of the loudspeaker's enclosure. However, fitting bigger, sealed enclosures into the awkwardly shaped spaces inside loco bodies can be very difficult. One way around this is to use the body itself as the enclosure. It's not ideal, because there will inevitably be holes where the bogies sit so it won't be fully sealed, but despite this the gain can still be very worthwhile. To achieve best results from this method there are two important provisos;

 

1. The back of the speaker must be open into the loco body, so it can vibrate the air mass inside, and

 

2. Air from the front on the speaker must not be allowed to easily reach the rear of the speaker or the two will cancel out and your sound will be very thin. So, your speaker must be 'set into' the body and form a continuous surface with it (the baffle your man was referring to). This is why you have to block as many of the holes in the body that you can.

 

Using this method can bring massive increases in sound volume, especially in models with big empty bodies like the Hornby 73, 90, 92, Eurostar etc. A logical extension of the method is to use one loco in a double-headed pair as a 'mobile loudspeaker', gutted to provide the space, and connected in parallel with the first loco's speaker via two-pin micro connectors. I have used this to great effect with my 25's and 86's, which sound for all the world like two locos.

 

Hope this helps,

 

Bif

[trisonic]

Yes you have to be careful of phase interference with multiple speaker installations too.

 

Best, Pete.