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Xmax, does it kill?
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luthier View Drop Down
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Points: 271 		Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 01 February 2019 at 12:53am
Originally posted by ceharden ceharden wrote:

The cones drivers designed for 2-way mid tops etc are designed to flex such that at higher frequencies only the centre of the cone is moving and the outer section effectively stays still.  This gives a better midrange performance but has an impact on cone strength.

As above, if you put too high an air load on any driver, asymmetric as you get on many bass horns is even worse, what you end up building is a confetti cannon!




Very interesting, never knew that! 

Also not too keen on making an expensive confetti cannon! 
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Originally posted by ceharden ceharden wrote:

The cones drivers designed for 2-way mid tops etc are designed to flex such that at higher frequencies only the centre of the cone is moving and the outer section effectively stays still.  This gives a better midrange performance but has an impact on cone strength.

As above, if you put too high an air load on any driver, asymmetric as you get on many bass horns is even worse, what you end up building is a confetti cannon!



Agree to a point in that a curved cone designed for use into the upper mids are often designed to flex so as to decouple as frequency increase effectively creating a smaller radiating area and increasing dispersion, it also has the effect of stiffening the cone laterally reducing the severity of bell modes.
A straight sided ribbed cone for example can be lighter for a given stiffness and the ribs arranged to decouple the centre from the edge of the cone and also to reduce bell modes but tend to break up less gracefully ie bell modes tend to be more extreme.
Curved cones also tend to be stiffer at the neck as the coupling to the VC is more direct, less of a change of angle between the two.
I have seen straight sided cones concertina at the neck.
For mid use the angle verses speed of sound through the cone also comes into play with regards upper mid response but not an issue here, I guess what I'm trying to say is not to write of a cone just because it has a curved profile.
Re the PD.153er, I'm a little surprised that it self destructed, could it have been driven past xdam (xlim), the old Fane 15L and 15B's IIRC had an xmax of around 5mm and an xlim of only 11mm, compared to a lot of modern drivers, that does not leave a lot of margin for error.
 
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Originally posted by fatfreddiescat fatfreddiescat wrote:

Originally posted by ceharden ceharden wrote:

The cones drivers designed for 2-way mid tops etc are designed to flex such that at higher frequencies only the centre of the cone is moving and the outer section effectively stays still.  This gives a better midrange performance but has an impact on cone strength.

As above, if you put too high an air load on any driver, asymmetric as you get on many bass horns is even worse, what you end up building is a confetti cannon!




Re the PD.153er, I'm a little surprised that it self destructed, could it have been driven past xdam (xlim), the old Fane 15L and 15B's IIRC had an xmax of around 5mm and an xlim of only 11mm, compared to a lot of modern drivers, that does not leave a lot of margin for error.
 

They were not run that hard, i doubt they were pushed past xlim, high passed at 90hz. We swapped out to 15nd930, done maybe 80 shows with them and run them harder. Literally zero problems. 


Edited by citizensc - 01 February 2019 at 8:28am
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Crashpc View Drop Down
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Good points. It depends how much is this cone function offset or eliminated with putting it into the horn. Direct radiation must be quite different topic one would guess. B&C bass drivers are often specced as curved cones, while these look pretty straight to me. After measurements I found they are not straight, but the curve is very subtle. "Obviously", there are compromises to be made on the cone - Frequency range and directivity, strength, standing waves, modes and flexing suppression etc.

I would always vote for stronger cone for horns, and then finding driver with closest best parameters I need rather then vice versa.
Nikon and Canon people should not be married to each other. Why did you let this happen?
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Originally posted by Crashpc Crashpc wrote:

Good points. It depends how much is this cone function offset or eliminated with putting it into the horn. Direct radiation must be quite different topic one would guess. B&C bass drivers are often specced as curved cones, while these look pretty straight to me. After measurements I found they are not straight, but the curve is very subtle. "Obviously", there are compromises to be made on the cone - Frequency range and directivity, strength, standing waves, modes and flexing suppression etc.

I would always vote for stronger cone for horns, and then finding driver with closest best parameters I need rather then vice versa.

After reading of your experiences with the PD, I too would be nervous about trying it in this instance.
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Points: 11776 		Post Options Post Options   Thanks (1) Thanks(1)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 01 February 2019 at 11:35pm
Maybe saying that curved cones are the issue might not be correct since very few are actually straight.  However there is definitely a difference in cones designed for high air loads, especially at lower frequencies.

A cone that isn't stiff enough will be caused to flex by the air load, especially if it's not even, e.g. letterbox throats and eventually you'll get fatigue failures, tearing etc.

The angle of the cone may be a useful indication.
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