Hi Sergiu
I tried for a long time to source the A37 steel specified by the designer, but in the end gave up. It doesn't seem to be available in N. America. After playing around with FEMM for a while, I realized that there wasn't much of a flux difference between the theoretical optimum material and a commonly available low carbon mild steel. I just went ahead and bought some 1018 mild steel bars.
I'm still wondering why you're using such thin paper. Unless I'm mistaken, the original design and even the commercial versions, use paper in the 180-200g range. Obviously, there are gains to be made from lighter membrane weights or by reducing the magnet gap, but my gut tells me that regular paper is just too thin.
I tried for a long time to source the A37 steel specified by the designer, but in the end gave up. It doesn't seem to be available in N. America. After playing around with FEMM for a while, I realized that there wasn't much of a flux difference between the theoretical optimum material and a commonly available low carbon mild steel. I just went ahead and bought some 1018 mild steel bars.
I'm still wondering why you're using such thin paper. Unless I'm mistaken, the original design and even the commercial versions, use paper in the 180-200g range. Obviously, there are gains to be made from lighter membrane weights or by reducing the magnet gap, but my gut tells me that regular paper is just too thin.
I was thinking about that steel too, or steel 416 (has slightly more carbon typical 0.15%) but didnt test them.
I want to use thinner paper because my magnets 40*10*10 will have 15kg force, and the original ones 40*20*10 had about 25 kg of force. I didnt buyed them yet. Next month i'll place an order (48pcs)..
Another considerent for using a thinner paper is that if you look at the patent bellow you can see that they used a thinner material, polyvinyl fluoride film (better than mylar) for the membranes and damping pads on the frame for reflections and damping tapes on the membranes for smoothing up the frecvency.
Also if i use thinner paper i can easily lower the magnetic gap without touching the steel.
I want to test these things on rice paper..
Brevet US4903308 - Audio transducer with controlled flexibility diaphragm - Google Brevete
I want to use thinner paper because my magnets 40*10*10 will have 15kg force, and the original ones 40*20*10 had about 25 kg of force. I didnt buyed them yet. Next month i'll place an order (48pcs)..
Another considerent for using a thinner paper is that if you look at the patent bellow you can see that they used a thinner material, polyvinyl fluoride film (better than mylar) for the membranes and damping pads on the frame for reflections and damping tapes on the membranes for smoothing up the frecvency.
Also if i use thinner paper i can easily lower the magnetic gap without touching the steel.
I want to test these things on rice paper..
Brevet US4903308 - Audio transducer with controlled flexibility diaphragm - Google Brevete
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Can you compare these two please:
steel 1018
AISI 1018 Mild/Low Carbon Steel
steel 416
Stainless Steel - Grade 416 (UNS S41600)
Wich one do you think is best?
The 416 steel seems to have a more controlled dosage of carbon (fix 0.15%) wereas the 1018 is between 0.14 and 0.20%..
Thanks in advance.
steel 1018
AISI 1018 Mild/Low Carbon Steel
steel 416
Stainless Steel - Grade 416 (UNS S41600)
Wich one do you think is best?
The 416 steel seems to have a more controlled dosage of carbon (fix 0.15%) wereas the 1018 is between 0.14 and 0.20%..
Thanks in advance.
stainles wont work at all its not magnetic as far as i know (or at least some forms). as for menbrame i tried some different materials so far (nomex, plain paper thin pcb). and the lighter the better. main pitfall i think is the fact that sound bounces of the magnet structure back into the menbrame. this creates peaks and valleys. also they change when you move the mic. wich makes it hard to compare results.
effficiency is a problem i have as well, i should redo my magnet structure. as i mentioned i use to much steel compared to magnets. but i want to keep cost down as well. my goal first is to get a speaker to play well with decent ouput, and bandwith. with the use of 4 or max 6 magnets. with this size menbrame the cutoff fequency is around 1 Khz. still rather high. it drops like a brick. adding a baffle dont seem to do anyhting maybe, because the speaker itself is big enough baffle for a speaker at 1khz and up. so the limiting factor is not the baffle but the size of the menbrame.
its not magnetic as far as i know (or at least some forms). as for menbrame i tried some different materials so far (nomex, plain paper thin pcb). and the lighter the better. main pitfall i think is the fact that sound bounces of the magnet structure back into the menbrame. this creates peaks and valleys. also they change when you move the mic. wich makes it hard to compare results.effficiency is a problem i have as well, i should redo my magnet structure. as i mentioned i use to much steel compared to magnets. but i want to keep cost down as well. my goal first is to get a speaker to play well with decent ouput, and bandwith. with the use of 4 or max 6 magnets. with this size menbrame the cutoff fequency is around 1 Khz. still rather high. it drops like a brick. adding a baffle dont seem to do anyhting maybe, because the speaker itself is big enough baffle for a speaker at 1khz and up. so the limiting factor is not the baffle but the size of the menbrame.
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Thanks Wrine. So the 416 steel is out of discussion?
stainles womt work at all
stainles wont work at all
Thank you very much for the input Wrine. I really appreciate your effort.
Brevet US4903308 - Audio transducer with controlled flexibility diaphragm - Google Brevete
Here is a frase from the patent i posted earlier (and above) :
"The length of cord on each side of the expanse as indicated at 65 in FIG. 2 determines the low frequency below which the frequency response of the diaphragm is attenuated. Such attenuation is desirable because the lower frequency response in a diaphragm has a greater amplitude and must be attenuated to improve the overall response. It has been determined that a cord length of 1/2 inch, with the cord fastened 1/4 inch away from each side of the expanse, satisfactorily attenuates frequencies below 100 Hz.
Affixed to each side of the central portion of members 18 and 20 is a means for damping the frequency response of the diaphragm above a predetermined cutoff frequency. This means may comprise felt pads 66, 68, 70, 71 mounted, respectively, within the arc of each web portion 24a, 24b, 26a and 26b. More specifically, a pair of felt pads 66, 70 or 68, 71 are located inside the cylindrical surface of each web 24, 26 and are attached at one edge to one side member 18 or 20 of the frame and at its opposed edge to the stacked magnets. The pads are each preferably sized to match the web height and extend substantially from the diaphragm central expanse to each of the remote frame locations 18a, 18b, 20a and 20b. The damping pads 66, 68, 70, and 71 damp sound waves that are generated within each cylindrically shaped web above a predetermined cutoff frequency. These sound waves otherwise interfere with the waves in the web material, acting to reinforce and cancel different waves. However, below a predetermined frequency, such internal sound waves are desirable to reinforce low frequency waves. The pads 66, 68, 70, 71 are chosen to slow the wave velocity to a rate at which such reinforcement occurs. It has been determined experimentally that felt of at least 80% wool content damps the frequency response above 500-700 Hz while slowing the wave velocity sufficiently to reinforce the lower frequency response.
The present transducer as best seen in FIG. 1 will have a resonant frequency dependent on the specific transducer size and the material employed. As shown in FIGS. 1 and 5, parallel strips of damping tape 73 are adhered at predetermined locations on the inside of each web end portion 24a, 24b, 26a and 26b. The strips of tape, preferably made of a woven fiberglass such as is found in strapping tape, aids in flattening the amplitude response and reduces harmonic distortion resulting from the device's resonant frequency and its multiples. Best results have been obtained with a damping tape mass of about 1/3 of the mass of the diaphragm 22, divided into strips spaced equidistantly apart from near the end of each web portion to the edge of the central diaphragm expanse. While three parallel damping strips are shown, it will be appreciated that an increased number f parallel damping strips spaced equidistantly but closer together also works well. "
PS: THE PATENT IS ONLY FOR DIDACTIC USE AND NOT FOR COMERCIAL USAGE.
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hahaha, yeah i used this technic with esl at some dergee to get rid of the peak. i have some felt behind it now, and it helps , but i does not reinforce low frequency's. i gues because the whole thing is not big enough to go any lower then 1khz ,i will post some measurements later on. i must get some thinner paper if posible today
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btw i indeed saw later on i am repeating what already has been mentioned in the patent sorry for that. i noticed it to late
i must get some thinner paper if posible today \
btw i indeed saw later on i am repeating what already has been mentioned in the patent
sorry for that. i noticed it to late
No problem Wrine.
You can post your findings too. There's got to bee someone to confirm and test whats been written there. You are the pioneer here my friend.
What kind of paper do you use now and how heavy is it?
I have for now a role of 30 meters 50g/sqm paper and i think that it can barely keep the bobin in place without bending (didnt test it yet--i will start the tests at the end of the month when i'll order the magnets). I think that this is the limit without bending it with on the weight of the bobin or tear it apart with the elastic.
Cheers
Sergiu
You can post your findings too. There's got to bee someone to confirm and test whats been written there. You are the pioneer here my friend.
What kind of paper do you use now and how heavy is it?
I have for now a role of 30 meters 50g/sqm paper and i think that it can barely keep the bobin in place without bending (didnt test it yet--i will start the tests at the end of the month when i'll order the magnets). I think that this is the limit without bending it with on the weight of the bobin or tear it apart with the elastic.
Cheers
Sergiu
hahaha, yeah i used this technic with esl at some dergee to get rid of the peak. i have some felt behind it now, and it helps , but i does not reinforce low frequency's. i gues because the whole thing is not big enough to go any lower then 1khz ,i will post some measurements later on.
\
btw i indeed saw later on i am repeating what already has been mentioned in the patent
If they say in the patent that if you have a bigger surface you can go lower with the frecvencies why not try this trick to lower the resonances?
If you have now on your ruban, lets say 10 cm height and 5 cm diam per cilinder, why not try 20 cm hight with 5 cm diam pe cilinder? We are doubling the surface here, so this bigger surface should have also a bigger dapening...
What do you say? Did you test this, combined with some sponge dampening inside the cilinders?
Sergiu
If you have now on your ruban, lets say 10 cm height and 5 cm diam per cilinder, why not try 20 cm hight with 5 cm diam pe cilinder? We are doubling the surface here, so this bigger surface should have also a bigger dapening...
What do you say? Did you test this, combined with some sponge dampening inside the cilinders?
Sergiu
hahaha, yeah i used this technic with esl at some dergee to get rid of the peak. i have some felt behind it now, and it helps , but i does not reinforce low frequency's. i gues because the whole thing is not big enough to go any lower then 1khz ,i will post some measurements later on.
\
btw i indeed saw later on i am repeating what already has been mentioned in the patent
i used some felt, and it work a bit. but still wonder about filling the entire cabinet of one cylinder. go bigger is not really an option my steel is only 180mm, my menbrame is 100mm at the moment. tomorow i will get rid of the wooden structure and replace it with 6 mm thick HPL. this way i win 2 x18mm and 2 x 12, so a 50mm in total more room for membrame. i might just add 2 magnets. since they can fit in if i make some room .
im still toying with the idea of using XPS foam as well, because this was one of the go to materials in the diy exciter/nxt area. itds light stable and pretty strong.
the paper i use now is pretty heavy, no clue how heavy. i used 80 grams printer paper and that is way to thin. it deforms where the coil is attached, and scrrews everything up. it did measured better.
.im still toying with the idea of using XPS foam as well, because this was one of the go to materials in the diy exciter/nxt area. itds light stable and pretty strong.
the paper i use now is pretty heavy, no clue how heavy. i used 80 grams printer paper and that is way to thin. it deforms where the coil is attached, and scrrews everything up. it did measured better.
Here a small video of the thing playing fullrange with some eq for baffle rolloff, and introduces some highs. measurement was with eq on close miced approx 25 cm.
im getting the hang of the tuning, and i see great potential, but as you can see i changed the design a bit. and will change it even more, i think there is much more to gain!
http://youtu.be/vdQwG9lFOIo
i used 6 magnets of 40-20-05, efficiency is still rather low. think its the weight of my paper and to small compared to the frame and magnet structure.
im getting the hang of the tuning, and i see great potential, but as you can see i changed the design a bit. and will change it even more, i think there is much more to gain!
http://youtu.be/vdQwG9lFOIo
i used 6 magnets of 40-20-05, efficiency is still rather low. think its the weight of my paper and to small compared to the frame and magnet structure.
Interesting. Please say more about those orizontall strips and how did you improved your design.
I was busy searcing for some good paper and look what i found. It has all the propreties that we need.
Its exactly as the one used at the Janus 50:
Buy tedlar sheet at Best tedlar sheet Price| Aliexpress Mobile
I looked on the pictures of other rubanoides on the net and they look exactly like they have the same texture and glossiness..
Cheers
Sergiu
I was busy searcing for some good paper and look what i found. It has all the propreties that we need.
Its exactly as the one used at the Janus 50:
Buy tedlar sheet at Best tedlar sheet Price| Aliexpress Mobile
I looked on the pictures of other rubanoides on the net and they look exactly like they have the same texture and glossiness..
Cheers
Sergiu
You can double up the magnets for the iron problem and do a 3mm gap. That way you will have allot of juice available.
well getting the thing together is no joke. these are smal magnets of 8 kg pull. together they pull 24 kg, enough to break ur finger if they come together at high speed, or at least injure urself. so im not loooking forward to increase the thickness haha well the stripes at bot and top supress allot of unwanted resonances. they eminate from the edges of the paper. ill take a look a tthe paper. i also gone do some shopping today at the local hobby shop
haha well the stripes at bot and top supress allot of unwanted resonances. they eminate from the edges of the paper. ill take a look a tthe paper. i also gone do some shopping today at the local hobby shop
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I understand.. What tape do you use for the stripes?
Thanks
Thanks
well puttin getting thing together is no joke. these are smal magnets of 8 kg pull. together they pull 24 kg, enough to break ur finger if they come together at high speed, or at least injure urself. so im not loooking forward to increase the thickness
i ordered some aluminum wire to get the weight down, its self bonding so i hope i can skip the glue crap. so its gone be a chalange to get a good righ to wind a bobine then heat it up. and the wires should bond.... well we will see. at least its thinner and ofc 3 times lighter then copper.
i made aversion with even thicker paper. it has less resonances , and plays from 200 hz, but it does need more eq specially in the higher regions.
i made aversion with even thicker paper. it has less resonances , and plays from 200 hz, but it does need more eq specially in the higher regions.
i ordered some aluminum wire to get the weight down, its self bonding so i hope i can skip the glue crap. so its gone be a chalange to get a good righ to wind a bobine then heat it up. and the wires should bond.... well we will see. at least its thinner and ofc 3 times lighter then copper.
i made aversion with even thicker paper. it has less resonances , and plays from 200 hz, but it does need more eq specially in the higher regions.
Why do you need equalisation? Do you have nasty spikes (resonances) in the hight frecvency range?
Did you stuffed the cillinders with dumping cloath?
This aluminium wire is interesting but i think you still need to put some glue on the edges of the coil to stick well. I think of that because of the vibrations and dont know how hard will get that wire adhesive..
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