Garden Railway Forum

I wasted a little of my time making a video of the performance of small (2” - 50mm dia) speakers.
I had two different speakers – a ‘cheap’ one which costs around $1-$2, and one that costs a bit more (maybe $4) and really looks more ‘robust’.
So I made a couple of cardboard ‘enclosures’ to sort of replicate a larger diesel body and a smaller, squeezed in speaker in say a tank loco’s bunker. And played diesel and steam sounds from my computer through them.

Maybe someone else is interested in how the speaker type and enclosure size really affect the sound.

I certainly wouldn't call that "wasting" time, it's been very informative and I for one am very appreciative of your efforts in sharing. Just a small point that has occurred to me, is using cardboard for the sound boxes truly representative of our models? I would think that it might absorb sound rather than reflect it with the more usual loco building materials i.e. plastic card and metal. I realise that your intention was to compare speakers but the material could possibly have skewed your results slightly. Also, please don't think that I am being critical, far from it I hope that this will open up a lot of views and encourage debate on a subject rarely mentioned.

Fascinating stuff, Greg. I tend to use small encapsulated speakers inside my little locos. I must try some similar comparisons of the various types I have used over the years.

Rik

Very interesting Greg, thanks.

I've only got sound in a couple of mine and although I had sort of got the general feeling that bigger is better (!) my limiting factor has been space rather than cost, both in terms of enclosure size and depth of speaker.

Helpful to know what to aim for in future though.

pandsrowe wrote: ↑Sun Mar 17, 2019 7:59 am I certainly wouldn't call that "wasting" time, it's been very informative and I for one am very appreciative of your efforts in sharing. Just a small point that has occurred to me, is using cardboard for the sound boxes truly representative of our models? I would think that it might absorb sound rather than reflect it with the more usual loco building materials i.e. plastic card and metal. I realise that your intention was to compare speakers but the material could possibly have skewed your results slightly. Also, please don't think that I am being critical, far from it I hope that this will open up a lot of views and encourage debate on a subject rarely mentioned.

All relevant questions but I wasn't going to waste a lot of styrene sheet making a more solid box - not that styrene is all that solid without some stiffening. (the cardboard is in the bin now!)
I doubt that the results are skewed the 'bigger is better' would still apply, I'm sure.
The video was just to illustrate that a smaller box sounds worse than a bigger one and a bigger speaker sounds better than a small one, with the other variable (box material) constant. These are pretty obvious BUT I wanted to hear the sounds 'side by side'.
As to cardboard absorbing sound - sure that's likely. (and my boxes weren't air-tight, just taped together) But loco bodies usually aren't empty either - mine are full of batteries, and electronics, and who knows how that affects the sound in any given installation. But from my different locos, it does seem to me that what's in the box didn't make a lot of difference to the sound. A loco body that looked to me to be crammed full 'with no air left' still sounded similar to an empty one before the batteries were put in. The main thing is to have the front of the speaker unobstructed to the outside.
I've also tried leaving relatively small openings in the loco bodies 'to let some sound out' but that didn't seem to make much difference either.

Anyone with different experiences, please let us all know.

gregh wrote: ↑Sun Mar 17, 2019 9:10 pm

Anyone with different experiences, please let us all know.

Not exactly a different experience, but I did experiment with an elliptical speaker instead of round, because it better fitted the space I wanted to use. The problem was that it just sounded tinny. The narrow width presumably emphasising the higher notes and the long dimension not really being big enough to give decent low note production. In the end I went for a round one, which although somewhat smaller gave a better overall sound.

The round one is mounted in a shallow tight fitting circular plasticard enclosure, underneath the loco footplate, pointing down, which definitely helped with volume and removed any muffled sound.

All subjective of course.

philipy wrote: ↑Mon Mar 18, 2019 7:27 am
Not exactly a different experience, but I did experiment with an elliptical speaker instead of round, because it better fitted the space I wanted to use. The problem was that it just sounded tinny. The narrow width presumably emphasising the higher notes and the long dimension not really being big enough to give decent low note production. In the end I went for a round one, which although somewhat smaller gave a better overall sound.

Interesting. Never thought that an oval speaker would be worse than round. I assumed the longer dimension would be 'better'.

gregh wrote: ↑Mon Mar 18, 2019 7:36 am
Interesting. Never thought that an oval speaker would be worse than round. I assumed the longer dimension would be 'better'.

My guess is that overall the face area of the speaker was probably smaller. It was slightly longer than the round diameter but also smaller in width than the round diameter. Probably, if the narrow dim was as the round diameter and the length then greater, it would have sounded better, but that of course would be a physically bigger speaker, so you'd expect it, as you say.