EMG/Expert/Astra soundbox measurements.

[emgcr]

A friend recently asked for measurements of the thickness of EMG/Expert/Astra soundbox platform springs for the purpose of reproduction. I also thought it might be interesting to record the lateral width of the stylus bars. These are the details I have come across over the years. Hopefully the attached schedule may help folk in the future who wish to make new items.

There is a great variation and it seems evident that there was no established norm and that experimentation was a continual process. There is no contemporary literature that has ever been found giving details of results so reproductions necessarily must now involve reinventing the wheel ! Good quality spring steel would seem to be appropriate to keep the platforms in place but the material and possible heat treatment for stylus bars is unknown---at least to me.

[CarlosV]

Thanks for posting, Graham, and mainly for having the patience to perform the measurements! Indeed there are variations - I was not surprised with variations across different models, but even the same model shows not insignificant variations in both dimensions from unit to unit. I guess it confirms the fame of cottage industry that both Expert and EMG had, although Expert seems more consistent, possible because it had a shorter life span and less models than EMG. Probably a consequence of low stock of parts, lack of quality control and variation of suppliers for these parts (it could also be that they manufactured these parts themselves). As you wrote, such measurements will not serve much as a guide to whoever endeavors to make new versions of these soundboxes, trial-and-error will be required, as you found out when making your outstanding EMG horns.

The fact is that, even with parts that were made in much higher production numbers and with better industrial processes and quality control, like HMV, we hear significant variation in sound reproduction from part to part, like, say, play different HMV5a's in the same machine, with same needles and same record and you will notice different sounds coming from each. Maybe they sounded alike when they left the factory, but time, wear and handling acted on all of them, and had their effects on making every one more or less a unique part despite looking identical to others.

[poodling around]

Thanks for posting, Graham, and mainly for having the patience to perform the measurements! Indeed there are variations - I was not surprised with variations across different models, but even the same model shows not insignificant variations in both dimensions from unit to unit. I guess it confirms the fame of cottage industry that both Expert and EMG had, although Expert seems more consistent, possible because it had a shorter life span and less models than EMG. Probably a consequence of low stock of parts, lack of quality control and variation of suppliers for these parts (it could also be that they manufactured these parts themselves). As you wrote, such measurements will not serve much as a guide to whoever endeavors to make new versions of these soundboxes, trial-and-error will be required, as you found out when making your outstanding EMG horns.

The fact is that, even with parts that were made in much higher production numbers and with better industrial processes and quality control, like HMV, we hear significant variation in sound reproduction from part to part, like, say, play different HMV5a's in the same machine, with same needles and same record and you will notice different sounds coming from each. Maybe they sounded alike when they left the factory, but time, wear and handling acted on all of them, and had their effects on making every one more or less a unique part despite looking identical to others.

Very interesting indeed CarlosV. Thank you for the comprehensive explanation.

This seems to make complete sense and I enjoyed very much reading it.

Another apparent mystery solved indeed !

[emgcr]

Thanks for your comments Carlos with which I entirely agree. Of course, one caveat, it should always be remembered that springs do get broken over the years---I have come across a number of heavily rusted items---and replaced, probably with whatever dimension material was available at the time. Stylus bars tend to be more long-lived.