Hi biffo.

I too wonder about the missing bass in model loco sounds.

Years ago I used to work from a book called "More about Loudspeakers" by G A Briggs, who was the design engineer for Wharfedale speakers BEFORE they were sold to Rank. And became Rank!

There were quite a few tricks to "fool" a little speaker into making more bass, including;

1. Reflex enclosures, where the speaker sits at the front, but the air BEHIND it is in a zig-zag path. The longer the path, the bigger the enclosure "appears" to be.

2. Filling LOOSELY, or partially, loosely , the enclosure with a sort of wooly foam. The sides were lagged with it and any hard surface.

3. Venting the enclosure: it needs a vent so it can move air, the more the better. Completely sealing it will just stop any air moving and add to the tinny sounds..

Can I suggest Googling loudspeaker design?

Jeff

Jeff,

Years ago I bought a copy of Designing, Building & Testing Your Own Speaker System by David Weems and have referred to it regularly ever since. I've built more than one set of hi-fi speakers and experimented extensively (and successfully) with the designs you've outlined in 4mm and 7mm scale models.

In the case of the 50, I was attempting to build an infinite baffle design of a larger volume using two drive units in phase. I've since realised the mistake I made was electronic and not a speaker design issue at all; I had wired the speakers in series rather than in parallel as intended. Since I've corrected this error the volume is much louder and the fall off in bass is much less obvious.

My experiments have shown that increasing the cubic capacity of the enclosure makes a significant improvement to volume. Gains of 50% are not unusual. Using the body or underframe of the loco or unit as the enclosure is highly effective. The improvement in bass is measurable and audible but not quite as dramatic. My most effective gains in bass have come from large bass reflex designs with long reflex tubes, employed successfully in my 56 and HST. I'm beginning to wish I'd gone for this with the 50.

Bif

I reckon this would make a good thread/discussion on the main board. I'd like to see what you've done, certainly.

I agree Jeff, I for one would be more than interested to see how Ian gets the best out of the restrictions placed on space & speaker size/performance.

It is especially important for exhibitions where the level of bass & volume is more important, something we are all striving to improve on in the limit of 4mm.

Jeff / Paul,

I have made a start on a table detailing my recommended speaker fit for each class of loco or unit. The aim is to have this on a website in the fullness of time. It will also be added to the 'helpsheet' for my range of chips. The helpsheet is here;

www.dckits-devideos.co.uk/doc/6.doc