The Talking Machine Forum — For All Antique Phonographs & Recordings

I see that there is an Expert 2 spring soundbox currently up for auction on ebay.uk. Sorry am not sure how to post the link.
It is similar design to the soundbox that has been a very expensive 'buy it now' for months on end however I see there are a number of differences between the two.
It appears to be in much better condition, does not have the engraved horizontal bar protecting the diaphragm and also the knife edge on which the needle bar pivots on is on different sides of the body in each case. Could one of these soundboxes be of much later construction than the other?
Iain

Sold for £701.

I think that's the most we've seen an Expert 2-spring sell for - they seem to have been strangely (relatively) undervalued in the past and sold for around the £500 mark. The price of the other one is utterly ridiculous of course, especially given the condition! This one is a little odd, lacking the protective bar as you say Iain. The knife-edge points are dissimilar to each other and appear uneven - I'm not sure I understand about being on different sides of the body though. It appears to me as if the needle bar platform has jumped out of its groove slightly and is therefore not sitting parallel in the photos.

In my honest opinion the 2 spring soundboxes are much better than the 4 spring type for most types of music. There was a good reason an Exhibition only had 2 springs and not 4. The additional 2 springs don't really do anything apart from limit the free movement of the needle bar, which is far from ideal and not really what you're looking for.

The extra springs were a slightly perverse and counter intuitive addition to soundbox design. I do think they were at least partly a bit of a folly, introduced to no doubt create a mystique around the art of "tuning" and the whole exclusivity of the EMG / Expert approach to gramophone design, maintenance and performance.

Andy, Looking at the photo above, of the two pivots the needle bar sits against the knife edge is to the right side of the body and the point is on the left side. In the case of the tatty 'Buy it Now' example these pivots are the other way round with the knife edge to the left.
I suppose, because the soundbox sits at an angle of around 60 degrees, which type of pivot is at the leading edge may make some sort of difference but it is beyond me to work out what.

The few examples, that I have seen, all have the knife edge on the right side of the body. It is the tatty 'Buy it Now' example that seems to be unusual. I'd be very surprised if the swap would make any difference to the performance. I also have an EMG soundbox which has no point and two knife edges.

I'm not an expert in expert soundboxes nor in exhibitions, which I have yet to learn and master. But I see a difference in all them.
The exhibition has two springs that fulfill a double function: 1) supporting the balance plate against the knife points, and 2) limit/dampen the needlebar movement. This is clear.
The expert 2-spring model...? I've never seen one except in the photos all you have been sharing here many times. These two springs with sharp ends seen to fulfill function 1 alone, letting the needlebar free for vibration, with the only constraint of the attachment to the diaphragm. But this is so only if the two sharp ends are placed exactly on the rotation axis, defined by the two knife edge supports. As soon as the spring points are displaced from that axis, they work also in function 2, dampening and limiting the rotation of the plate somehow, depending on the displacement of the spring points from the axis, and the pressure exerted by them. I don't know if the intention in design was this or not, neither I know if the theoretical centered positions of the spring points on the plate are marked somehow, or the plate has any built-in nips where the spring points must be placed. But you see where I want to go ...
The expert 4-spring soundbox, under this view, would be a refinement, separating the two functions: one couple of springs centered, for function 1, and the other couple expressly added for function 2, thus placed intentionally displaced from the rotation axis. Or the four springs may be spring both functions ina duplicated fashion.
Anyway, what is the desired arrangement for the 2-spring model? This has always fascinated me...