Another DIY Ribbon thread

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#261
Originally posted by Audiophilenoob I can send you some Dhenry I just ordered some...
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I just got the foil you sent me. Many thanks! It's wonderfully wonderfully thin and precisely the right width for what I want to do. I'm so happy I won't have to cut it at all. Thanks also for the 4.3 micron samples -- boy, those are fragile.

In other news... I got a test amp from apexjr.com that I'm more comfortable using than the household stereo... I wired a few toroids -- fun stuff. Seems to work fine. My magnets should arrive today... and I've decimated the steel supply at the local hardware store.

The last item on my initial TODO list is to find something to corrugate the foil with. I guess I could get a couple of those gears from BG Micro and glue them together carefully? They need to be fairly wide. What other methods have people used? My friend and I, long long ago, used some conveniently shaped bottle cap, but those seem less common than they used to be.
 
#262
Zell said:




The last item on my initial TODO list is to find something to corrugate the foil with. I guess I could get a couple of those gears from BG Micro and glue them together carefully? They need to be fairly wide. What other methods have people used? My friend and I, long long ago, used some conveniently shaped bottle cap, but those seem less common than they used to be.
Click to expand...


I have 8 of those gears sitting here 🙂

I matched all the teeth and glued them to make a annealing tool that supports up to 2.5" wide ribbons...

I used a dowel I shaped to run through the 1/4" Inner diameter of it and so they turn
 
#263
Audiophilenoob said:



I have 8 of those gears sitting here 🙂

I matched all the teeth and glued them to make a annealing tool that supports up to 2.5" wide ribbons...

I used a dowel I shaped to run through the 1/4" Inner diameter of it and so they turn
Click to expand...

Audiophilenoob - What a great idea! I've been wondering where I would be able to get much wider gears. I'm following your other thread with great interest. It looks like you have killer magnets (I hope that is not literaly true 🙂 )


Zell - I'm happy to hear you are building ribbons too. The more, the merrier. Keep us informed.
 
#264
dhenryp said:


Audiophilenoob - What a great idea! I've been wondering where I would be able to get much wider gears. I'm following your other thread with great interest. It looks like you have killer magnets (I hope that is not literaly true 🙂 )


Zell - I'm happy to hear you are building ribbons too. The more, the merrier. Keep us informed.
Click to expand...

unfortunately that term killer is truer than you think 🙁

I let two of those pole pieces with all the magnets attached come together with my index finger in the way...

OUCH!!!! it more than hurt a little... 🙁
 
#266
dhenryp said:
Audiophilenoob - I got the foil. Thanks!
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I've been annealing 4.3 micron foil and it holds it well

it doesn't even tear actually...

I've also been able to get a piece over 70" long off the roll of 4.3 without tearing... I think the humidity lately helped...

I would say that if you have the patience to trim and anneal and possibly have to do it a few times cause of mess ups... that the 4.3 micron is thick enough to use for long ribbons... once annealled it is sturdy enough for a decent amount of abuse... I could not get it to tear with small breathes... with a lot of air force though I could rip it
 
#269
Could you measure the response from off-axis too (like 30 and 60 degrees), often it's the most important measurement in practise. Also sometimes a line-level crossover is the best solution (I think a direct-driver ribbon might be a such case as the amplifier is specific for the driver element type with a very low impedance).

Btw. How tightly the left and right diy ribbons can be matched, do they often differ in response?
 
#271
mhelin said:
Could you measure the response from off-axis too (like 30 and 60 degrees), often it's the most important measurement in practise. Also sometimes a line-level crossover is the best solution (I think a direct-driver ribbon might be a such case as the amplifier is specific for the driver element type with a very low impedance).

Btw. How tightly the left and right diy ribbons can be matched, do they often differ in response?
Click to expand...

My original plan was to build active crossovers and gain-clone type amps. I hope to eventually get to that but I realized if I wanted to listen to the speakers in the next year or two I needed an interim passive.

The two ribbons are pretty closely matched on-axis. I've not measured them off axis yet.


Regards,

Denis
 
#274
Ok,
I'm getting into building a pair of 10 cm (4") long tweeters. How big magnets would I need? I've already got 50x10x4 mm N40's, are these efficient enough? Obviously some steel frame is needed to make the field stronger. I hope these could be used >1500 Hz (with 24 dB/oct xover).
~Mikko
 
#275
mhelin said:
Ok,
I'm getting into building a pair of 10 cm (4") long tweeters. How big magnets would I need? I've already got 50x10x4 mm N40's, are these efficient enough? Obviously some steel frame is needed to make the field stronger. I hope these could be used >1500 Hz (with 24 dB/oct xover).
~Mikko
Click to expand...

It all depends on what type of magnets they are. If they are Neodymium (say N35) they would end up being about 67% as strong as mine - still pretty good. If they are ceramic magnets, they are probably too weak for anything but initial experimenting. 1500 hz is certainly in the ballpark for a crossover frequency for this kind of driver.

Sounds like you might want to follow the path I described at the beginining of this thread. You could also take a look at my web page for a condensed version of this thread:

http://home.comcast.net/~hendentures/

Good luck and have fun!
 
#276
Denis,
Yes, I've gone through your pages (and some other like the swedish ribbon threads on both forums). The magnets are Neodymium (N40), I'll make first a proto using whatever parts I found (some U-shaped steel like the shelf holder
here ). I have also downloaded FEMM and start experimenting with it.

On some ESL thread they suggested using toroid 230V / 12V (or so) power transformers. Do you think they could work with ribbons? I haven't calculated any resistances, but I think my is gonna be ~10 mm wide and 10 cm long. I've also considered using the Dahlberg's design ribbon - a stripped aluminium on mylar. That way the resistance could be increased a little bit though not enough for direct-drive. With a 0.01 ohm resistance (impedance) about 400:1 impedance ratio is needed, that's 20:1 voltage ratio (230V/12V seems to be ok).
 
#277
Hi mhelin,

I've got no experience using ready made transformers for impedance matching. The topic was discussed briefly in this thread but I'm a pretty hard core DIYer so I made it myself.

I'm not sure this any advantage to going with the foil on Mylar approach if you are still going to need a transformer, certainly not of you have to build a transformer. I would probably not go with the mylar unless you can get significantl more than .01 ohm. You could probably come close to that with pure aluminum.

Regards,

Denis
 
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