Group Buy: Feastrex clone - 42mm diameter HiperCo 50 solid rod

Rewind

Member
2009-01-18 7:42 pm
Oslo
Hi,
I am going to try to make an electronagnetic motor similar to the Feastrex D5e and D9e. I have found a rod the can be used for the pole in the middle. When using iron the pole needs to be larger, but with Permendur that diameter can be smaller. HiperCo50 is another name for Permendur and contains Fe 48%and Cobolt 48% and 2% vanadium, for easier machining.


The rod I have found is 12 kg, 1.05 meters long and cost $1530. Usually minimum order quantity is 100kg and cost tens of thousands of dollars. Smaller quantities are impossible to find, so I need help to share the cost. Two drivers would need two poles that are about 10cm in length. I will use iron for the rest of the electromagnetic motor beacuse it is just too expensive for a type iii Feastrex. You can easily shape it with a simple metal lathe, or hire someone to do it for you.

I am hoping to reach more than 2 tesla. A permament magnet can achive 1.6T.

Insulated copper wire can be found for cheap on fleabay.
The rest of the iron can probably be found locally, but Permendur is more rare.
It also needs vaccum casting, to preserve magnetic properties and not mix with air.

After you are done with machining it can be a good idea to anneal it. Feastrex uses hydrogen annealing, but I am not sure how important this step is. There are simpler annealing methods that can work almost as good.

Anyone interested in their own hand built feastrex with 42mm voice coil?
 
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Rewind

Member
2009-01-18 7:42 pm
Oslo
Of course. I have some washi paper now that I am playing around with. It is not impossible to make something similar. I found an even cheaper source of permendur in the states and the UK so group buy can be closed I guess. I think it is too advanced and expensive for most members. And risky.
 

Rewind

Member
2009-01-18 7:42 pm
Oslo
I have not decided yet on regular front and rear suspension, or if I go for leather, cotton, wool, copper fingers, carbon tubes, or rubber.
Winding the voice coil and machining the magnetic gap with high tolerance will for sure be the trickiest part of this venture.
Thank you for your support.
 
Some construction details: Feastrex uses custom sources for their metals in the type I and above drivers. Not open market bar stock. Another thing is that the washi paper is specifically formulated for use in Feastrex cones. Feastrex also has a respectable pile of cones that didn't make the cut. None of these details should deter you from experimentation with full range drivers, its just that I do think calling it a "clone" could be a stretch, IMO. "Another perfectly awesome field coil full ranger? Sweet! Naturally, I'd be happy to see/hear it! I love full range!
 

Rewind

Member
2009-01-18 7:42 pm
Oslo
Exactly. Well, the magnetic material for a type ii will cost me about £3000 for a pair. The seller insisted that if I don't heat treat with H2 (rather explosive if air is present) after machining the permendur and iron (they need seperate heat treatment cycles which double the costs) I may loose up to 50% in strength. I don't think there is anything magic about the permendur that Feastrex uses, it was just a very good choice of magnetic material to reach 2.1-2.2 Tesla in the magnetic gap. I wrote clone because I would have liked to try and duplicate everything including the washi, but also try a few other things (Fertin). Of course a clone will still just be a clone and sound different. Until I will be able to cough up £3k I will put this one on hold.
 
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ultrakaz

Member
2004-10-20 11:32 pm
This may sound like a dumb question, but have you heard the Feastrex that you are trying to copy? If you have not, what commercial drivers have you heard that have left you wanting for more/different sound? Usually, you start with a driver (Lowther, Feastrex, etc.) and identify what is not to your liking and then search for a driver that does not have those faults. If no drivers exist, then think about how you can "improve" on all the drivers you have heard (or maybe a different amp, source, etc.). Not trying to discourage your endeavor but without some specific sonic goal and not just using electromagnetic permendur motor, you may find out that you never needed a permendur electromagic motor in the first place.
 

Rewind

Member
2009-01-18 7:42 pm
Oslo
No, I have not. Norwegian stores are more into Sonus Faber, Tannoy and MBL. I have seen youtube videos and it sounds very crisp. I have also read descriptions of the sound in comparison to Lowthers.
Until I can afford the electromagnetic motor I will continue experimenting on regular drivers, To at least learn how to make a nice cone and voice coil. My reason for doing this is that I am not pleased with the paper used in the drivers I have heard. Vintage fullrange drivers are better, like the Saba Greencone, but the magnet is tiny and voice coil diameter is very small. I have a 2" voice coil Eminence Delta Pro 8a that I am building a cone for. My first attempt with washi was a failure because I did not understand how thick the paper needs to be. I knew it would not work with 25gr paper, but what if :) In my next try I will use 100gr art paper.