Hi again people,
This is perhaps a bit of a newbie question.
Is there a generalised 'effect' on breakup characteristics of a driver, depending upon its cone profile?
I am aware that a curved cone will perhaps break up in a more controlled fashion than a straight 'cone', but what occurs in drivers using 'bowl' or parabolic hemisphere type cones?
Such as these:
It isnt easy to see from the picture, but the larger of the woofers is a 6" with a cone depth of 35mm and the other woofer is a 5" with a cone depth of 15mm. I was rather surprised there was such a large difference, the 5" 'cone' really is very shallow indeed, and conversely the 6" cone is very deep.
This is perhaps a bit of a newbie question.
Is there a generalised 'effect' on breakup characteristics of a driver, depending upon its cone profile?
I am aware that a curved cone will perhaps break up in a more controlled fashion than a straight 'cone', but what occurs in drivers using 'bowl' or parabolic hemisphere type cones?
Such as these:
It isnt easy to see from the picture, but the larger of the woofers is a 6" with a cone depth of 35mm and the other woofer is a 5" with a cone depth of 15mm. I was rather surprised there was such a large difference, the 5" 'cone' really is very shallow indeed, and conversely the 6" cone is very deep.
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figure out the effective radius or diameter for each of the cones, you may find that the section of a sphere that they represent has the same aspect ratio.
Of course it may not actually be a section of a sphere, and is another similar shape.
The issue of breakup is complex and afaik it can not be determined by any simple means...
_-_-bear
Of course it may not actually be a section of a sphere, and is another similar shape.
The issue of breakup is complex and afaik it can not be determined by any simple means...
_-_-bear
This subject has received extensive discussion i papers at AES over the years. As one may expect, there is no "right" answer. I know SEAS did a lot of work recently on some of their Mg cones changing the curvature to move the breakup much higher up where it would not cause much trouble. If I have read the papers correctly, the state of the art is a rather complex curve that is not quite a negative hyperbolic. The reason the bowl shape is not optimum is it tries to couple the voice coil to the cone at the weakest part. A straight side cone will go into bell mode too easy. Much past that, I just look at the response and breakup for myself to determine if the designer was successful, not try to second guess him by looking at it.
thanks for your replies guys. I figured it wasnt clear cut. These drivers are cheap paper cone Mission woofers. I have been unable to find any fr graphs for them. Is it really the weakest point? If it were a sphere and another point exactly opposite is drawn. Those are the 2 strongest points arent they? Maybe im missing something. But yes, similarly to the fullrange drivers i havda used, they have a voice coil cup. But it is vented, as is the rear of the spider, and rear part of former also vented. The 6inch driver sounds like it rolls off very smoothly, no twangy 2-4khz presence like breakup. The 5inch sounds like it has a more ballooning midrange, going alot higher, but with some breakup. I just wondered if there was anything good about this type of 'cone'. The drivers themselves seem to tick alot of good cheap woofer checkboxes.
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Yes, the cone is basically perpendicular to the coil at that point unlike a straight cone or better yet, a curvlinear shape. The closer the cone is to parallel with coil, the more inherently strong and resistant flexing it will be.
This contribution is more in the way of 'interesting trivia' than a scientific contribution to a sensible question. I have an article from the UK mag' "Wireless World" (now called something else) which goes back many moons; 60's perhaps. It describes how Ted Jordan made the cone for the driver he manufactured after his pioneering work on the Jordan-Watts module, of which I have two. Th JW's cones were aluminum and the newer ones (the brand of which I forget) were formed from Titanium. Titanium is very awkward to work with. They wanted a particular cone profile and to their surprise (and relief, I suspect) they found that placing a sheet in a circular clamp (4" dia' I think) and then forcing the centre down with the appropriately sized rod (prob' 1.5") and stretching the metal automatically gave them the curve they wanted.
I'll try and find the article and get the actual function they were after.
Cheers, Jonathan
I'll try and find the article and get the actual function they were after.
Cheers, Jonathan
Btw mondogenerator there have been serious attempts at flat cones. The KEF B139 being well known. Technics did a line of flat "honey cones" drivers for bass and mid units in the '70's. The JAES paper of their work in available on the net. saw it last month somewhere.
May be interesting reading. JB
May be interesting reading. JB
Sorry, I thought we were discussing the cones you had posted and subsequently asked if that was the strongest point. My bad.
Hi,
FWIW for the inverse curve (bowl shaped) drivers the voice coil is hardly
ever directly connected to the cone except for inverse dome mids and
tweeters, where the voice coil diameter is large compared to the driver.
For bass/mids generally a cone shaped coupler used, sometimes with
also direct voice coil coupling as well, its very hard to generalise "bowls".
rgds, sreten.
FWIW for the inverse curve (bowl shaped) drivers the voice coil is hardly
ever directly connected to the cone except for inverse dome mids and
tweeters, where the voice coil diameter is large compared to the driver.
For bass/mids generally a cone shaped coupler used, sometimes with
also direct voice coil coupling as well, its very hard to generalise "bowls".
rgds, sreten.
The titanium cone speaker was known as Audio & Design and the process described by Jonathan Bright to form a naturally induced shape from a clamped sheet of titanium included an oscillatory action to aid the formation.I always wondered what the rejection rate amounted to.In adding to unusual profiles,the lampshade cone of the Hartley Turner(England) 10'' speaker surely was innovative,in that it conveniently corrected the weak coupling at the apex that is a problem with a pure concave shape,by starting out with a convex section and progressing to the reverse shape nearer to the periphery.
Thanks VaNarn.....have you seen/owned an A&D unit? I can't recall even seeing an ad' for one in OZ. Btw I had just finished reading a book on the Whoppi-do US spy plane the SR71 (Blackbird) which was built by Lockheed in the 60's. It had a large proportion of titanium in it and they had a steep learning curve manufacturing it. Apparently it reacts badly with chlorine and cadmium (I think) amongst other things. Anyway parts would fracture in the summer but not in winter and eventually they found that the local reservoir had a blue/green algae problem in the hotter weather that the authorities contained with chlorine! The tool cooling water was destroying the Ti. Some nuts would shear off the bolts until they found there was enough cadmium in a chrome plated spanner to react with the Ti.....
Very expensive job. JB
Very expensive job. JB
The A&D speaker looked virtually the same as the Jordan-Watts,which is not surprising.I am not sure if it was imported via an agent into Australia or obtained directly from England. I only recall coming across one pair and I have no opinion an about how they sounded.My interest at that time was the A&D pickuparm,M9BA,a unipivot arm with a mercury bath contact arrangement.This arm ,after the A&D consortium dissolved,was handled by the Keith Monks company.Hopefully someone else can offer information about these 'firsts' in the use of titanium cones.
When looking at this. What comes to mind is........an egg, what are the strongest parts of an egg ?
I see why you want to make that connection but the speaker cone is not supported at all points like the egg shell 'sphere'. The cone has no support to transfer the pressure created at the voice coil into a 'structure.' The edge has only a surround which offers almost nothing.
If the material is stiff and the surface of the cone is such that impact of air pressure does not compromise its integrity and exculsion doesnt go too far...its pretty close 😉
Hi,
Nobody is really answering the original question. Straight cones are stiff
radially but circularly not so as they are straight. Curved cones reduce
circular stiffness but improve radial stiffness due to the curved profile.
The terms here are interchangeable and can cause confusion, straight
cones have higher frequency radial modes but lower frequency circular
modes, curved cones lower radial and higher circular.
Whatever, inverse (bowl) drivers don't follow the same rules.
rgds, sreten.
Nobody is really answering the original question. Straight cones are stiff
radially but circularly not so as they are straight. Curved cones reduce
circular stiffness but improve radial stiffness due to the curved profile.
The terms here are interchangeable and can cause confusion, straight
cones have higher frequency radial modes but lower frequency circular
modes, curved cones lower radial and higher circular.
Whatever, inverse (bowl) drivers don't follow the same rules.
rgds, sreten.
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Hi Mondogenerator,
Peter Larsen did a nice paper on cone breakup modes that included the inverted dome type IIRC. It's at the bottom of the list here -
Loudsoft.com
entitled "Geometrical Cone Stiffness - A FEM Study by Peter Larsen, LOUDSOFT 2003"
Regards
Peter
Peter Larsen did a nice paper on cone breakup modes that included the inverted dome type IIRC. It's at the bottom of the list here -
Loudsoft.com
entitled "Geometrical Cone Stiffness - A FEM Study by Peter Larsen, LOUDSOFT 2003"
Regards
Peter
You may have seen the vidos of cone breakup modes on youtube. Many have been done with non-newtonian fluids. Here is one very interesting one done with rice to show how the breakup patterns vary with frequency.
rice resonance - YouTube
Maybe you could do this if you have a function generator an amp and some rice and compare results with different cones. Not sure it will work though with slope-sided cones but you may find a different way other than rice to visualize the break up modes.
rice resonance - YouTube
Maybe you could do this if you have a function generator an amp and some rice and compare results with different cones. Not sure it will work though with slope-sided cones but you may find a different way other than rice to visualize the break up modes.
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