silver foil caps for ribbon membrane
ive been thinking about doing a diy ribbon for a while now and have started researching membrane material
i saw that someone mentionefoil from caps and i remenbered i have some mundorf silver in my garage so i decided to check them out
here is what i found Attachment 213948
seems to be thin mylar with vapour deposited silver,is silver suitable for a ribbon or does it have to be aluminium
its very thin but suprisingly strong
The metalized layer is so thin that it will have way too high impedance to function a at ribbon membrane...
i just put a multi meter on a length of this foil and it was fluctuating too much to get a acurate reading
238 ohm was about it over a 1m length
it is coated on one side only and is silver
i am trying to choose the best material i can to build a true ribbon but i need some help to understand a few things
what is the reason people use foil glued to mylar ? why not just the foil
i presume to make it easy,er to handle
corrigated vrs non corrigated ,why corrigate if it results in more distortion
is there a general rule regarding this like if its run down to a certain frequency it must be corrigated or over a certain lenth perhaps ?
aluminium foil and thickness ,some say that general household foil is to thick but others that have used it say its fine and being thicker can have some benefets ,eg stronger and smoother frequency responce are a couple i,ve read
ribbon width , is wider better for output(more spl) if your not concerned about beaming or is there a golden rule say like normal box speaker dimensions
the above are just a few i can think of for now all oppinions and advice is welcome
You need to have an idea of how wide the gap between the magnets should be. The wider, the weaker magnetic field, less output. The length (height) of the driver? A long one gives you a higher impedance/resistance and no need for an impedance transformer. If the impedance for a single piece of aluminium is too low, you will need to make more traces and have them connected in series. For that you will need some form of backing material. If your diaphragm of aluminium is very thin, you can do like Magnepan, just a single piece of aluminium with a suitable resistance, 3 to 4 Ohm. As the radiating area will be small, it can only be used for high frequencies. Your questions calls for a lot of answers, you will have to have an idea and work from there. Want do you want to build, what shall it do?
I hope too address some of these issues as started here http://www.diyaudio.com/forums/plana...n-tweeter.html
And when I get farther along in my construction and have more pictures ready, I will start a new thread so I don't get accused of thread hijacking. jer
dont worry about thread jacking as id love this thread to cover all aspects of true ribbons inc where to get materials ,what type to use and also construction
i,m using the dahlberg audio design "the tall neodymium ribbon" as a starting point as i think its the best documented example to use and the engineering behind it seems to be sound
i will copy the above design as close as possible exept i will be using the 2um mylar i have and normal household foil (as thin as i can find )
i have not yet found magnets the same ,it calls for 70x10x6 but the closest i can find is 2"x1"x1/4 which will work fine and still fit in with the original recipee using a single row per side instead of 2 rows i am however concerned they may be hard to work with at 37 pnds pull per unit
the magnets are from cms magnetics i will need 100 (25 per side of each ribbon))at a cost of $2.30 each
the mylar i got from ebay just type in esl mylar and it comes up ,they supply 2,6 and 12 um 40 m cost me only about $30 so good value
Very well then I will finnish posting the project here with your permission.
Tommorrow I will post a picture of the magnet structure I built in 1992 that was inspired by the very apogee's I now have.
Back then the net was called AOL or PRODIGY and very little too no information could be found magnet types and strengths.
I have found way more info just yesterday than I did a year ago.
The magnets I used were from radioshack and I had at least more than 100 of them.
The ones I have left are super glued together and I can't get them apart.
From what I can tell they are the same magnets used in my apogee's only half the thickness.
My structure seems to have about the same field strength as the apogee's
Therefore they are ceramic 5 and it took me 15 years to find this information.
They have (supposed to) a gauss strength of 3800 gauss.
Knowing this I can now make an aproximate estimation of the effeciency and neo's would be very sweet indeed.
I found a 2" X 2" x 4" neo with over a 750lb. pull WOW !
Two of those you should be able to drive the thing with a 1 watt amp and still blow you right out of the room.
Anyway I have found some on line calculators for this project and I will compile them for you and post them here.
Aswell as some early threads discussing the theory and math behind it,this will take some time though.
The magnets from radioshack were 1 7/8" X 7/8" X 3/8"
The ones I am using for the 4" structure are half the width at 1 7/8" X 3/8" X 3/8" and a single layer or two of some 1/8" thick neo's would increase the feild strength tremendousley.
But, I couldn't find any when I was shopping for them 2 years ago as they were sold out and never restocked.
The confusion that happened in the last thread was due to my excitement and compyling data 24/7 with little to no sleep for four days straight.
I was just about to give up the project due no interest or appericiation to what I was trying to accomplish.
You have revived my enthuziasim, Thanks. jer
i look forward to seeing your design so far
magnets are the hardest thing for me to find ,well for a resonable price anyway
the ones i have found are $2.35 each so 100 is not so bad considering you would pay this or more for just 1 normal pistonic driver like scan speak
steel should cost no more than $100 so $400 should be about right for the total cost which considering the price/performance should be very good value
I just found these they seem a little more reasonabe in price considering 4 times the strength of a ceramic 5 type which is what I have at the moment.
The 1 7/8" X 7/8" x 3/8" magnets are about $.89 each I paid $.99 back in 1992.
This is a start , but ,I will do complete search and price comparison.
The otherday I found company near me that does custom stuff for the big 3 and such for motors and whatever,and they might be alot cheaper for big batch of them.
Two of these will have 5 times the field strength of one of my ceramics and one 1/3 the thickness with the same footprint.
Even though the per piece cost is alot it is actualy cheaper considering field strength and size. jer
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