KNOP lathe DIY build

[2bitcomputer]

markrob, grooveguy thanks for the replies.

Those exciters are available and in stock at Mouser.
After reading the datasheet
https://www.visaton.de/downloads/pdf/visaton_exciter_principles.pdf
I can see some potential problems with these:

"The excited surface is, compared to a lightweight
cone membrane, very large and heavy, and thus unable to oscillate coherently. That means, not every point of
the surface moves into the same direction with the same amplitude at the same time. The exciter generates a
bending wave which propagates towards the edge of the excited plate, where it is reflected back towards the exciter."

As Mark said the moving mass might be too great.
But the reflection of the wave off the edge of the plate might also cause echo-like problems?

[grooveguy]

I tend to agree. In its intended application, as a driver for a loudspeaker (of sorts), the plate is screwed to the cone/diaphragm and moves that plate and what it's screwed to simply against the inertia of the magnet, etc. mass. I like better the idea of securing the high-mass element, the magnet, and coupling to the cutting stylus in as simple and low-mass means as possible, as indeed Balázs did in his most recent photos on the previous page. His drivers appear to differ from the ones in the datasheet in that Balázs made direct mechanical connection to the voicecoils, his square mounting plate seemingly attached to the magnet structure.

I saw this Dayton exciter that seem to work this way, their DAEX25FHE-4...

Snap1.jpg

...that's rated at 25W and looks like a possibility. It's small enough, too, so that two could be mounted 90° apart without too long a throw to the stylus holder.

[xrc]

Dear All,
excuse me for being lost: i didn't get notifications but now i turn this option on.
Since august, I burnt a lot of EX 30S with high power, looking for higher gains on the record, and then I decided to switch back to KNOP's original setup with the Visaton BF32 membrane speakers. They work only with cutter stylus (engraving needles only jumps on the surface), and with them they have better results on audio power. It needs more play with the EQ in order to compensate the acoustics of the aluminium funnel.

grooveguy: (Tue Jan 19, 2021 6:20 pm )

Balázs, I'm assuming that your test used the diamond cutting stylus and an appropriate blank, not the embossing stylus shown in your photo.

yes, it's true. the post is telling about the myshank (462) but the photo shows the dental drill - sorry.

Just wondering what quality you can achieve with embossing and this head. Can you confirm this and possibly tell us what your drivers (transducers) are? Good work!

Embossing sylus didn't worked with vinyls for me, i used therefore only polycarbonate and axpet. They sound lo-fi, but i liked them because the stylus is very cheap:)
some demo: http://mumia.art.pte.hu/mami/kbalazs/temp/vinilkut/exciter-mono-50degrees_860012SF-needle.wav (original: https://www.youtube.com/watch?v=iaa-Vj85Pdo)

Summarizing my results:
Exciter + embossing stylus + vinyl = not o.k. reason: vinyl is too hard (???)
Exciter + embossing stylus + axpet/polycarbonate = o.k. - i experienced a lot with this, and some -random- results were pretty good
Membrane-based speaker + embossing stylus + axpet/polycarbonate = jumping on the surface, no grooves are being created


2bitcomputer (Tue Jan 19, 2021 8:55 pm )

Hello, I have a question about which exciters to use if I build a head like this.
The exciters xrc used are 10W but this company (visaton) also makes one that is rated for 50W:
https://www.visaton.de/en/products/drivers-accessories/structure-borne-drivers/ex-80-s-8-ohm
Is there an advantage to using the 50W version?

For me it was too big and heavy to experiment with.

grooveguy (Thu Jan 21, 2021 4:20 am )

Thanks for that insight, Mark. I'm still in the dark as to the bracket-spring that connects the stylus-holder to the backplate. Balázs's photos show a definite anchor wire to prevent fore-to-aft (Z-plane) movement of the stylus, but I'd like to understand the compliance of the leaf-spring part and how it is able to allow angular movement in all X/Y directions. I usually just bury everything in rubber but am rethinking that. Others who have posted in these pages have boasted of how lightweight all driven assemblies are, but in this latest iteration, Balázs seems to have a lot of metal to move, and it certainly doesn't seem to compromise performance. Comments?

Yes, it's true. The metal parts are eating a lots of bass, therefore they need more power resulting overheating... Now i'm also lost in this question. I just followed KNOP's instructions about the steel rod. I tried it and it works well.

Thanks, grooveguy, for the Dayton link - i'm interested about the results!

+ a question: there are also people who realized KNOP's project? would be great to hear about it.

Best wishes
Balázs