DCC Choosing a speaker... what affects the result?

[Dog Star]

Just a simple one-liner, "you can get better speakers" - although "better" than what is not clear.

A rare outing of a favourite diesel and the sound is burbling nicely. The host for the day offers the thought that maybe a different speaker might be worth considering - fair comment, just how do we proceed to source a speaker that is likely to offer a "better" sound?

Apart from asking what constitutes a better sound - and I would like to see suggestions on that idea - the comment set me thinking as to what characteristics of a DCC-sound-fitted-7mm-diesel affect the sound that we hear. For example:- what is the impact of "shape" on the sound from a speaker? or, assuming that the sound project is a reasonable recording, what is the impact of the sound decoder manufacturer / decoder size on the speaker sound?

After a short spot of navel gazing... the current diesel is a JLTRT Cl.37/4, the decoder is a Loksound V4 with a Howes sound file, the speaker is a DCC-Supplies bass reflex speaker of size circa 20mm x 55mm.

Please discuss!

thanks, Graham

 

[ZiderHead]

You may well have just opened Pandora's Speaker Cabinet

This is how I'm going at it: Impedance and power match the decoder and speaker (e.g. both 4ohm and 3W), and the biggest and most efficient speaker you can fit. Big because its the only way to get bass, and for a tractor you really want bass Efficient because that bass uses power and you don't want the decoder amp clipping.

Mount the speaker in a solid cabinet. Sealed or ported cabs are almost universal (and even weird pushmepullyou arrangements) but the maths to get it right is tricky and unreliable, and at this scale pointless. So an open back cab is the way to go; the dimensions are far less important, they are shallower, and the sound surrounds the enclosure rather than just going out the speaker. The depth should be less than the diameter of the speaker and the back opening at least the same area (shape doesn't really matter.)

RS or Farnell have a bunch of speakers which could fit the bill

 

[Yorkshire Dave]

I just use the largest speaker compatible with the decoder I can fit into a loco. In O scale I plan the sound into the loco build so I end up with most of the boiler barrel as the speaker chamber. This is the approach I'll be taking when I build my O scale GP9 - the long hood will effectively become a speaker chamber.

I have retro fitted speakers into Canadian HO locos and, again, I built the speaker chamber into the long hood which meant hacking part of the chassis to create the largest space possible.

 

[TheSnapper]

Graham

My JLTRT '37 was used as a test-bed for various speakers & speaker combinations. I've come to the conclusion, empirically, that IMHO etc open backed installations sound better than enclosed speakers, if its possible to use them. For the frequencies we can expect from the small units we use, bass cancellation is not a problem, but the advantage to my ears is that the overall sound is less "boxy". This chap seems to agree:

The loco currently has a Cliff Williams large round speaker on an open baffle, firing downwards through a hole in the tanks.

Tim

 

[Cliff Williams]

I have my own speakers now.
Best advice from my trials are to avoid Mylar speakers and buy mine....
This is a Mylar speaker on an old XL V3.5 chip, then swapped out to a CJW 35mm round 8ohm speaker

Ok plug over!

To add to the mix I am now collecting sounds for Bryan Robertson to work on.
The first I did was 37401 over a year ago, followed by another couple of 37s and numerous kettles.
What I have learnt is the position of the microphone influences the end product immensely.
I have recordings that are good and others that are WOW. The next thing is getting the loco to perform on load too, I have a recording from this year which was a dream day out and resulted in amazing sounds of pure effort.

I am lucky to have numerous serving drivers who review the finished product and the 37 comes out on top. It runs two of my speakers with brass enclosures.
Running them outside behind a hedge in a friends very large garden brought a fascinating result with two new visitors. As they walked down the garden they got excited and said where is the mainline?
"That's a 37! Show us quick....."
A few minutes more walking and all was revealed.
Now that sums it up for me.