DIY soundbox / reproducer diaphragm - any tips ?

[mrrgstuff]

Absolutely fantastic ! I haven't seen all your video's yet but look forward to seeing them fully tonight.

How much do your blue soundboxes cost approximately to print / make I wonder ? Could they start to be sold ?

Such interesting videos too !

Thanks glad you liked the videos!

The actual material costs are really quite low. A standard kilogram roll of PLA plastic for the 3D printer will make a lot of sound boxes and other than that there is just the gasket material, various o rings, a handful of mainly M3 hardware, and some large washers for weight. The HDPE and Polystyrene diaphragms are also very cheap to make.

Other than that its just the time and labour to print them and put them together.

I hadn't considered selling them - but if there is a market for them - then I think I could make and sell them at a reasonable price If people are interested I'll work out what the price could be. Thanks

[mrrgstuff]

The videos are VERY interesting, and I especially like the idea of the 3-D printed sound box. Listening to the various diaphragms, I noticed the the upper register notes, in most cases, are dampened. One thing you might consider is redesigning the needle bar to accommodate a much smaller diaphragm connector-screw--one that is similar in size to the ones used on HMV, Columbia, etc. sound boxes. If the screw and bolt is too massive, it will impact the needle bar's ability to transfer the higher frequency vibrations from the needle's tip to the diaphragm--or so I have been told by a couple of restorers. Likewise, for diaphragms attached using solder, only a "whisper" of solder should be applied.
OrthoFan

Thanks - glad you liked the videos

Yes - the upper frequencies suffer and the needle bar could certainly be better. I've been using an M3 screw - but in the future will probably use something smaller to get the mass of the connection down

I did want to try to keep as many pieces 3D printed - at least to begun with however on a previous non 3D printed one I used a metal needle bar and I might well try this type on the 3D printed one as well (about 13m into this video):
https://youtu.be/qamaeL0585M

I'm also looking into improving my test kit so I can better objectively measure the frequency response of the sound boxes to make sure I am going in the right direction!

[mrrgstuff]

Very interesting and well done video!

May I suggest to add in the playing comparison one industrial soundbox like the 5a/b that is lying on the gramophone. It would serve as common reference to all the new developments.

Thanks - glad you liked the videos

Yes - in some of the videos I do compare to either a 5b or a 4 like in this one:

https://youtu.be/gCv5-lAIjvw

However for the comparison of the plastic diaphragms I decided not to include the No.4 so it was just a straight comparison between the different types of plastic

My next video on this will be a comparison of 3 different types of metal. I also have a mica diaphragm on order which I will them use to compare also. Once I have decided which material makes the best diaphragm I will then test it against the No.4 (and maybe the 5b)

Of course its an iterative process also - as I have plans to improve the design so there is more to compare than just the type of material for the diaphragm!

[mrrgstuff]

My next video on this will be a comparison of 3 different types of metal. I also have a mica diaphragm on order which I will them use to compare also. Once I have decided which material makes the best diaphragm I will then test it against the No.4 (and maybe the 5b)

My metal test video is now up

https://youtu.be/aMrX8tn-tYI

Thanks

[Inigo]

A suggestion for the next step... using the thin aluminium sheet of the food tray. Make the diaphragm larger, and practice using a burin ended in a small ball to make the concentric corrugations, ridges and valleys, passing softly the burin on the diaphragm making circumferences. You can use a towel underneath the diaphragm to make it bend when you draw the circles for the valleys. If you proceed gently you can make pretty high ridges. Then turn the diaphragm to the opposite face to mark the two valleys at both sides of a Ridge, and so on... This way I've achieved a very good imitation of a Meltrope diaphragm that indeed sounded very well. As the ridges and valleys make in the end the diaphragm diameter a bit shorter, that's why you must start with a plain circle of aluminium sheet slightly larger than the desired final size. You can practice several times, and you'll see how soon you get the trick of it. Don't forget to form the central dome!

Meltrope-3-Soundbox-Needle-Bar-Diaphragm-Ball.jpg

buril-doble-bola-de-3mm-y-de-8mm-n8.jpg

[Daithi]

A suggestion for the next step... using the thin aluminium sheet of the food tray.

Meltrope-3-Soundbox-Needle-Bar-Diaphragm-Ball.jpg

Its remarkable that you can achieve such uniformity.
Is the diaphragm in the picture made from a food tray?
Also do you anneal the sheet?

Thanks

[Lucius1958]

A suggestion for the next step... using the thin aluminium sheet of the food tray.

Meltrope-3-Soundbox-Needle-Bar-Diaphragm-Ball.jpg

Its remarkable that you can achieve such uniformity.
Is the diaphragm in the picture made from a food tray?
Also do you anneal the sheet?

Thanks

Another suggestion: you might be able to fabricate a set of compasses, by drilling spaced holes in a bar of some sort. Fix a center point at one end, and insert the burin in the other holes to create the rings.

-Bill

[Inigo]

Daithi, the one in the photo is an original Meltrope, not mine. But mine was pretty similar, although aluminium colour. It's not that difficult to make... I have no photos of my last copy at hand... Will take it from the storage and send photos to you later.
...
Here are three examples, made at free hands, no compasses... They're not perfect, but approximate enough. And they sound very well...

IMG_20200909_001606.jpg

IMG_20200909_001621.jpg

IMG_20200909_001626.jpg

[Daithi]

Daithi, the one in the photo is an original Meltrope, not mine. But mine was pretty similar, although aluminium colour. It's not that difficult to make... I have no photos of my last copy at hand... Will take it from the storage and send photos to you later.
...
Here are three examples, made at free hands, no compasses... They're not perfect, but approximate enough. And they sound very well...

Remarkable .... Is the original Meltrope the same material thickness as your examples and is it also made of Aluminium?
Also do you anneal the material while you are working it?
I can't imagine doing that much work to it without tearing it to pieces.

[Inigo]

Daithi,
I don't anneal the material. It's aluminium cut out from a food tray. Same thickness (apparently, I have no caliber to measure) as the meltrope original, but seems yet thicker than the aluminium used for the hmv 5a/b diaphragms. Believe me, if you go softly with the burin, deepening the grooves gradually as you go passing with the burin making the same circle time after time, softly and gently, and the diaphragm is placed on a thick cloth, etc... and you make a circular groove, then turn the diaphragm the opposite side and mark softly the two grooves at both sides of the ridge you've made, and go this way... It's easier done than explained! Just try it yourself... A set of burins of different sizes cost a mere 2 euro at a dime store (in Madrid these are big stores owned by the Chinese, selling everything for the home...) they sell them for women, for making i don't know what art or upholstery labour... or nail decoration!
https://www.amazon.es/dp/B074W5QN7L/ref ... wFbDR6V1HC

https://www.amazon.es/dp/B07M5W69YG/ref ... wFb6EGH62S