Hi Nick,
yes the glue tends to ovalize it but once you fit the surround should be fine. The paper might also be too thin.
I only use on cut in cones, i know you might think that more glue joints will strengthen it, actually it doesnt. with one joint it will preserve its shape alot better.
Hi Frank,
I did try the decoupling between main cone and whizzer. While in theory looks like a great idea in reality wasnt really happy. Maybe i didnt do it right but also if you study alot of the old drivers you will see many full ranges without this decoupling compliance but with the main and whizzer cone firmly glued.
Mmd=18g
My personal ultimate cone will be full paper with surround made of paper as well.
yes the glue tends to ovalize it but once you fit the surround should be fine. The paper might also be too thin.
I only use on cut in cones, i know you might think that more glue joints will strengthen it, actually it doesnt. with one joint it will preserve its shape alot better.
Hi Frank,
I did try the decoupling between main cone and whizzer. While in theory looks like a great idea in reality wasnt really happy. Maybe i didnt do it right but also if you study alot of the old drivers you will see many full ranges without this decoupling compliance but with the main and whizzer cone firmly glued.
Mmd=18g
My personal ultimate cone will be full paper with surround made of paper as well.
Hi Hentai,
I haven't measured it but its got a good thickness too it. Its very strong.
Its thicker then a d130 cone.
Yes I do agree, when the cone and surround are both paper its the best. But Those are made from pulp aren't they?
I have a jbl 2220 cone. The thickness and weight of my diy and the 2220 cone feels close. Though I haven't measured the diy cone. I will have to bring it to work and check the weight.
How are you figuring the impedance of your voice coils? Are you strictly going my inductance reactance, or some other method?
Thanks,
Nick
I haven't measured it but its got a good thickness too it. Its very strong.
Its thicker then a d130 cone.
Yes I do agree, when the cone and surround are both paper its the best. But Those are made from pulp aren't they?
I have a jbl 2220 cone. The thickness and weight of my diy and the 2220 cone feels close. Though I haven't measured the diy cone. I will have to bring it to work and check the weight.
How are you figuring the impedance of your voice coils? Are you strictly going my inductance reactance, or some other method?
Thanks,
Nick
Hi Nick, when you design the voice coil you take in consideration Re (aka Rdc or dc resistance or impedance at 0 Hz if i can call it that)
Nominal impedance is a term for domestic consumers and in most cases is the average value of impedance between 200 and 1khz for most woofer, fullrange drivers. You have to look at impedance curve to the right of the resonance peak, you will find a flat area and then start to rise again. That flat area should determine the nominal impedance.
Nominal impedance is a term for domestic consumers and in most cases is the average value of impedance between 200 and 1khz for most woofer, fullrange drivers. You have to look at impedance curve to the right of the resonance peak, you will find a flat area and then start to rise again. That flat area should determine the nominal impedance.
Well, not at 0hz. No impedance there just straight resistance, LOL. But I know what you meant. I don't think that nominal impedance was created for the domestic consumer. If that were the case you wouldn't have impedance rating on pro audio gear.
But I understand what your saying. 200 to 1k average. That works, thanks.
Nick
But I understand what your saying. 200 to 1k average. That works, thanks.
Nick
Hi Nick, i dont know what you are talking about.
Investigating the resonance around 1k.
Leo Beranek in his "Acoustics" said that it is possible for a second resonance to appear after the mass controlled region of the spectrum. The resonating circuit would be formed by inductance Le and the mass elements (Mmd and air load). Now condition to avoid resonance ( altho it was also described as helpful if you want to extend the range) was that (Rg+Re)^2 to be much higher than (w*Le)^2
Now taking a Re between 9-12 ohms, Le around 1.5mH and w=2*pi*f with f=800-1000Hz we can see that the values are pretty close.
It can also be caused by transition from main cone to whizzer.
Investigating the resonance around 1k.
Leo Beranek in his "Acoustics" said that it is possible for a second resonance to appear after the mass controlled region of the spectrum. The resonating circuit would be formed by inductance Le and the mass elements (Mmd and air load). Now condition to avoid resonance ( altho it was also described as helpful if you want to extend the range) was that (Rg+Re)^2 to be much higher than (w*Le)^2
Now taking a Re between 9-12 ohms, Le around 1.5mH and w=2*pi*f with f=800-1000Hz we can see that the values are pretty close.
It can also be caused by transition from main cone to whizzer.
First attempt at a diy cone. only 28 grams. The thickness of the paper is 17 mils. It was fairly out of round where the glue joint is. But it's seemed to have straightened out over time.
I did a test with the coatings. I tested both pva and damar varnish. With a single coat of pva I couldn't tell the difference. One coat of damar should a definite increase in stiffness. Now I didn't do any quantitative test. Just flexed the paper in my fingers and compared it to a non treated piece. I have 4 other cones cut out but not glues. I will try and glue them tonight and treat them with damar. These will be my first cones. Don't really care for the white color. But color isn't really a concern at the moment. I have not decided if Im going to buy stock voice coils or try and make my own. I bought a winding machine off ebay. So winding my own will be pretty easy compared to the field coils. It is a manual machine though.
Nick
I did a test with the coatings. I tested both pva and damar varnish. With a single coat of pva I couldn't tell the difference. One coat of damar should a definite increase in stiffness. Now I didn't do any quantitative test. Just flexed the paper in my fingers and compared it to a non treated piece. I have 4 other cones cut out but not glues. I will try and glue them tonight and treat them with damar. These will be my first cones. Don't really care for the white color. But color isn't really a concern at the moment. I have not decided if Im going to buy stock voice coils or try and make my own. I bought a winding machine off ebay. So winding my own will be pretty easy compared to the field coils. It is a manual machine though.
Nick
Attachments
will keep you updated soon. Still haven't go the basket yet, and I need it to get that last things in order.
I glued together another cone last night. I found that it was my method of securing the joint for drying that pulled the cone slightly out of round. I used 2 pencils and some spring clamps. Worked like a charm. The glue is aleen's tacky glue.
Just 3 more to go. I m trying to find some info on the coil dimensions for a jbl 150 bass horn driver. It will dictate the size of voice coil i'm going to put on these cones.
Just 3 more to go. I m trying to find some info on the coil dimensions for a jbl 150 bass horn driver. It will dictate the size of voice coil i'm going to put on these cones.
Hi
I have been trying to find another way to make spider suspension, and I came up with this.......Please feel free to comment.
As I see it a normal spider has two thing that I would like to do better. The first thing is the mass and second is that it has a piston areal which produces an unwanted sound. I have seen some that uses a thin solid material with a spring like patten, this one way to reduce the areal, but I would like to make it less than that.
My idea is to use four torsion springs, see picture. This would give a minimum of areal and the weight is very low. If the loop on the spring is made small it will also provide a horizontal stabilisation to help the voice coil to stay in the magnetic gab.
If any of you have an idea to where I can get thies springs, please let me know.
Take care
I have been trying to find another way to make spider suspension, and I came up with this.......Please feel free to comment.
As I see it a normal spider has two thing that I would like to do better. The first thing is the mass and second is that it has a piston areal which produces an unwanted sound. I have seen some that uses a thin solid material with a spring like patten, this one way to reduce the areal, but I would like to make it less than that.
My idea is to use four torsion springs, see picture. This would give a minimum of areal and the weight is very low. If the loop on the spring is made small it will also provide a horizontal stabilisation to help the voice coil to stay in the magnetic gab.
If any of you have an idea to where I can get thies springs, please let me know.
Take care
Attachments
Frank found a mistake on the voice coil spreadsheet in the formula for the total number of turns. Thanks Frank.
Attached is the modified version.
The spider idea is sound but i guess you wont escape the added mass issues because you will need a metal ring anyways to attach it to the former. Very thin steel could do the trick.
Original spreadsheet earlier in thread has been replaced with the version linked here.
Attached is the modified version.
The spider idea is sound but i guess you wont escape the added mass issues because you will need a metal ring anyways to attach it to the former. Very thin steel could do the trick.
Original spreadsheet earlier in thread has been replaced with the version linked here.
Well it looks like I'm not going to be able to convert the woofers to field coils like I had planned. I will have to re design the magnet structure to do it. The reason, I forgot about clearance for the voice coil going into the magnet. With the field coil in there the voice coil would hit it.
So there out of the picture for now. But I'm still going to try and convert my jbl 2440 compression drivers.
Thanks for the help you guys gave me.
I'm not giving up on the project, just trying another option. But I'm still going to test out my cones in the jbl drives.
Nick
So there out of the picture for now. But I'm still going to try and convert my jbl 2440 compression drivers.
Thanks for the help you guys gave me.
I'm not giving up on the project, just trying another option. But I'm still going to test out my cones in the jbl drives.
Nick