Tracking Weight of acoustic gramophones.

[VanEpsFan1914]

Can I just say I love the new soundboxes, and would love to know when someone makes the rest of the gramophone? These are great!

[mrrgstuff]

If you could please discuss briefly the differences in diaphragm materials.
If you have not already done so.
I think you did talk about this in a previous post

Any previous discussion was not mine. Forgive me if in re-stating the obvious.

That might have been me I too have been experimenting with 3D printed soundboxes and tried a variety of different materials. I have documented it all in YouTube videos - mainly these ones:

https://youtu.be/pw9DoCmvl9s
https://youtu.be/XqAlJVpN3ZM
https://youtu.be/aMrX8tn-tYI
https://youtu.be/GwkSmJzJ_bU
https://youtu.be/mK1bGhanqf4

I must admit I am very impressed by the Expert inspired ones physicist has created. These look excellent and I would love to see/hear them play.

I had considered that making a 3D printed clone of an Expert soundbox was the closest I was ever going to be to having one (and I am sure there would be a market for them). In the end though I went for a freelance design based around the dimensions of the No.4 - made in PLA with a variety of different diaphragm materials including mica and corrugated aluminium, which were the best performing though other materials could also be considered acceptable

In the end I did have fairly good success but also intend to revisit the project as I have a few more ideas

Its great also to see others experimenting with this technology

[Daithi]

If you could please discuss briefly the differences in diaphragm materials.
If you have not already done so.
I think you did talk about this in a previous post

Any previous discussion was not mine. Forgive me if in re-stating the obvious.

That might have been me I too have been experimenting with 3D printed soundboxes and tried a variety of different materials.

Yes, you are correct Mr Stuff. And I would also invite you to discuss same. Your opinion is as valuable as your data. I sometimes find data confusing when too many parameters and caveats are involved. Despite an interest in science, I would make a bad scientist.

[Daithi]

Greg Bogantz makes the following point on another thread which I think informs the conversation here.

I would be cautious of using too little tracking force. ......Using too little force will result in the needle not being able to stay in contact with the accelerations of the groove wall during high modulation. This is because ALL acoustic reproducers of ALL brands have very high moving mass of the diaphragm and stylus bar and linkage as reflected at the stylus tip. When the needle is allowed to leave the groove wall temporarily, it slams back into the wall slightly later with even more instantaneous acceleration which will nick or gouge the groove wall. This is the classic definition of mistracking and it will result in permanent record damage. It is a common belief and misunderstanding that "lighter is better". So it is often the case that users, particularly of modern playback equipment, get their tracking force set too low which results in actually MORE record wear than when the tracking force is optimum for that particular pickup and stylus. Most acoustic reproducers are designed to operate at around 100 grams of tracking force at the needle tip. Much less than this amount will produce mistracking which will be heard as distortion, blasting, and/or buzzing when playing loud passages. Continued use of this too light tracking force will permanently damage the records.

[mrrgstuff]

Yes, you are correct Mr Stuff. And I would also invite you to discuss same. Your opinion is as valuable as your data. I sometimes find data confusing when too many parameters and caveats are involved. Despite an interest in science, I would make a bad scientist.

Well, I suppose in the end the results were not too surprising. The mica (new diaphragm for an HMV No.4) did very well and surpassed most of the other materials. Thin aluminium sheet did very poorly when flat, but when corrugated with stiffening rings, did much better and at least for some people sounded better than the mica. Flat steel and flat copper did OK, but polystyrene sheet from a CD jewel case performed well, and would make an acceptable diaphragm if mica wasn't available and has the added bonus of looking like mica.
I am sure there are many other materials and combinations/laminates which would perform adequately, but there is no doubt in my mind why mica and then corrugated aluminium were used as they perform the best.
Interestingly, shortly after performing these tests, I found an analysis written in an old book (pre orthophonic era), which basically said that lots of things work but there is a reason all the major manufacturers use mica despite spending lots on R&D, and that's because it works so well.
Obviously personal preference does play a part, and my videos show the comparison for anyone who wants to hear the differences. Thanks

[mrrgstuff]

Greg Bogantz makes the following point on another thread which I think informs the conversation here.

I would be cautious of using too little tracking force. ......Using too little force will result in the needle not being able to stay in contact with the accelerations of the groove wall during high modulation. ....

This is also a very good point. My soundbox is only about 70g as I didn't really design it with higher weight in mind. Although it performs quite well, my next design will incorporate more weight, I aim to get it up over the 100g mark. Due to it being 3D printed, the main body has very little intrinsic weight, so has to be designed so weight can be added internally.