Equalize your Soundtraxx Speaker Output
One of the great features that Soundtraxx carried over from the Tsunami to the Econami and Tsunami2 decoders is the 7-band equalizer. This is a neat feature that allows you to customize the sound output frequencies of the decoder to better match the capabilities of your speaker. Sound is generated by pushing air out from the speaker cone. The larger the cone the more air you can move and those low frequency bass tones that we love to hear are located down in the lower frequency range below about 500Hz. So speaker size is an important consideration if you want the best bass sounds. However, we just can’t squeeze a 4″ speaker into an HO switcher much less an N-scale locomotive. This creates trade offs for getting the best sound.
One common method modelers resort to is turning up the volume in hopes of getting more bass. However this doesn’t really work all that well since it can create distortion. If a speaker is too small to actually move enough air to produce the bass you want, turning up the volume can result in an effect called clipping–we hear it as crackling sounds. The 7-band equalizer gives you the ability to alter the frequencies put out by the decoder so you can turn up the volume without leading to clipping and distortion.
So how does that work? The 7-band equalizer is similar to the sliders on many stereo systems that allow you to alter the output of given frequencies in 7 distinct frequency bands or ranges. Each band can be set through a range of 0-255 with 127 being “0 dB”. A value of 255 gives you +12 dB and 0 gives you -12dB. These values are programmed into CVs 226-232. Notice in the figure that the frequencies overlap, so when you change one it will affect adjacent ranges, requiring a stepwise approach to get it just right.
Another useful feature is that Soundtraxx includes preset values for 4 sizes of speakers. Programming a value of 1-4 into CV 225 will set the frequency range values to correspond to speakers ranging from <1″ to >4″ in diameter. A value of 7 will allow you to use the custom values entered in CVs 226-232. As a test I set the CV settings to correspond to the micro speaker values to see how they would work with a 13×18 mm sugar cube speaker. I then started making slight modifications to the CV values to see if I could improve on the preset values–I couldn’t, so I guess Soundtraxx did a pretty good job. So once you start installing new Soundtraxx decoders don’t forget to at least set CV 225 to one of the preset speaker sizes.