# Speaker cone designs and their effects



## strakele (Mar 2, 2009)

Hey guys,

Recently I've been wondering why certain speaker cones are designed the way they are, and what effects these designs have on the sound produced.

I really don't know how to describe other than to post pictures, so here goes:

First, a simple rounded speaker cone:









Next, the design that most readily fits the definition of a cone:









Then those with a rounded dustcap:









Flat dustcap:









A pointed dustcap:









Finally, speaker with phase plug in the middle of the cone. 









Since all of these designs are used in current production, I think it's safe to say that there isn't a 'superior' or 'better' design. So that being said, why are there differences? What are some of the benefits and drawbacks of each design?

This is more for my curiosity (and perhaps that of others?) than anything.


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## Redcloud (Feb 5, 2009)

strakele said:


> Hey guys,
> 
> Recently I've been wondering why certain speaker cones are designed the way they are, and what effects these designs have on the sound produced.
> 
> ...


Interesting topic! I am curious as well.


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## strakele (Mar 2, 2009)

I thought so 

Hoping someone with a lot more knowledge on the subject can enlighten us.


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## Electrodynamic (Nov 27, 2007)

strakele said:


> Hey guys,
> 
> Recently I've been wondering why certain speaker cones are designed the way they are, and what effects these designs have on the sound produced.
> 
> ...


Dish shaped cones are primarily used in subwoofers for aesthetics. A lot of the time you'll notice that most "dish" cones are simply a large dust cap while a normal concave cone rests underneath. The main reason for a "normal" concave, or V-shaped, underneath is for proper centering of the voice coil former to the main diaphragm, rigidity, and sometimes, mass reasons. 



> Then those with a rounded dustcap:


Most normal (i.e. rounded) dust caps are used to shield the gap from debris and to also provide a seal for cooling the voice coil via pushing air back over/around the pole on the inward stroke. The majority of speakers, whether it be home or car, use this type of dust cap due to cost and functionality reasons. The Dynaudio example you supplied is rather large for the size of the speaker because they use large voice coils.



> Flat dustcap:


See the explanation above. Making a dust cap flat has almost no acoustic benefits compared to a normal convex dust cap, especially when it comes to subwoofers.



> A pointed dustcap:


Pointed dust caps have been used to try to extend the high frequency response of a driver on the knowledge of the higher frequencies emanate from the center of the cone. The latter is no where near as efficient or successful as the following:



> Finally, speaker with phase plug in the middle of the cone.


Phase plugs do two things: extend the upper frequency response of the driver, and make the driver less directional. Since high frequencies are reproduced from the center of the cone first, if you have a bullet-shaped plug protruding from the center of the voice coil former, you can tailor the high frequency extension to a certain degree by the shape and length of the phase plug. 



> Since all of these designs are used in current production, I think it's safe to say that there isn't a 'superior' or 'better' design. So that being said, why are there differences? What are some of the benefits and drawbacks of each design?


In subwoofers, the shape of the cone/diaphragm means almost nothing. When you get into/above 1k Hz, things change a bit and the profile of the cone, type of dust cap, shape of dust cap / phase plug, etc, begin to have a an immediate impact on the sonic characteristics of the speaker. 



> This is more for my curiosity (and perhaps that of others?) than anything.


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## T3mpest (Dec 25, 2005)

Electrodynamic said:


> Dish shaped cones are primarily used in subwoofers for aesthetics. A lot of the time you'll notice that most "dish" cones are simply a large dust cap while a normal concave cone rests underneath. The main reason for a "normal" concave, or V-shaped, underneath is for proper centering of the voice coil former to the main diaphragm, rigidity, and sometimes, mass reasons.
> 
> 
> 
> ...


Technically sound is produced from all parts of the speaker. A phase plug is used to prevent this fact from
having a speaker lose output due to points on each edge the speaker cancelling out when wavelengths become small vs size of the cone. At least as I remember learning from Lycan's old threads on beaming.


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## Electrodynamic (Nov 27, 2007)

T3mpest said:


> Technically sound is produced from all parts of the speaker. A phase plug is used to prevent this fact from
> having a speaker lose output due to points on each edge the speaker cancelling out when wavelengths become small vs size of the cone. At least as I remember learning from Lycan's old threads on beaming.


Technically I never said that sound wasn't produced from all parts of the diaphragm/cone. High frequencies begin at and/or are more easily reproduced at the center of the diaphragm closest to the voice coil former. 

Vifa tried to combat what you mentioned when they made cones that had jagged edges under the surround-to-cone glue joint in order to minimize reflections from resonances that a normal equal-length cone supposedly caused. They only made a few small production runs of those speakers when they found out that wasn't the reason for high-frequency beaming and/or loss of HF output. If what you posted was true, the Hertz cone would be horrible because of cancellation or spikes from resonances due to higher frequency wavelengths combating each other since they would be exemplified from the inward curvature of the cone at its center.


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## T3mpest (Dec 25, 2005)

Electrodynamic said:


> Technically I never said that sound wasn't produced from all parts of the diaphragm/cone. High frequencies begin at and/or are more easily reproduced at the center of the diaphragm closest to the voice coil former.
> 
> Vifa tried to combat what you mentioned when they made cones that had jagged edges under the surround-to-cone glue joint in order to minimize reflections from resonances that a normal equal-length cone supposedly caused. They only made a few small production runs of those speakers when they found out that wasn't the reason for high-frequency beaming and/or loss of HF output. If what you posted was true, the Hertz cone would be horrible because of cancellation or spikes from resonances due to higher frequency wavelengths combating each other since they would be exemplified from the inward curvature of the cone at its center.


Well cone shape curve does help combat beaming some, beaming is always a function of the speaker diameter. When the speaker begins to beam is dependent upon diameter due to those being the outside edges of a circle, hence the frequency where one part of the cone will begin to be out of phase with itself. An inward curve puts those points closer together while keeping the SD the same. Lots of companies have attempted to use cone profile to control beaming. The only company I know that claims they found something that works well is AE. Apparently their TD15's don't beam nearly as early as expected due to some hyperbolic design nick found once on another strange speaker that he duplicated.

A phase plug is used to disperse this high frequency energy. Instead of the high frequency energy on each side summing togther near the center as out of phase, the plug bounces it back . This dispersion improves on axis response even though it's being thrown around basically, since it's at least not being cancelled out. The size of the phase plug I would assume then would depend on how big the speaker is, since the phase plug has to be large enough to be "seen" by each half of the wave.

A speaker in the real world does not operate as a point souce. The entire cone makes sound so there is a physical distance between the top and bottom of the cone. This PLD creates cancellation at certain frequencies. That's also why towers are usually arranged vertically isntead of horizontally in an array (at leats partially). It's like having a speaker that is only 6 inches across, but say 48 inches tall. The speaker beams horizontally at a high frequency compared to it's vertical dimesion. This eliminates reflections off the ceiling and you don't generally want alot of dispersion vertically, just horizontally. The center speaker in the array would then set the height cues as it's the one where output would sum too vertically.


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## Electrodynamic (Nov 27, 2007)

T3mpest said:


> Well cone shape curve does help combat beaming some, beaming is always a function of the speaker diameter. When the speaker begins to beam is dependent upon diameter due to those being the outside edges of a circle, hence the frequency where one part of the cone will begin to be out of phase with itself. An inward curve puts those points closer together while keeping the SD the same. Lots of companies have attempted to use cone profile to control beaming. The only company I know that claims they found something that works well is AE. Apparently their TD15's don't beam nearly as early as expected due to some hyperbolic design nick found once on another strange speaker that he duplicated.


An inward curve on the diaphragm actually increases Sd compared to a driver with a phase plug, which would actually work counter-intuitively to the larger surface area causing more beaming issues. A phase plug doesn't move with the diaphragm, so it's not considered part of the Sd of the driver.


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## T3mpest (Dec 25, 2005)

Electrodynamic said:


> An inward curve on the diaphragm actually increases Sd compared to a driver with a phase plug, which would actually work counter-intuitively to the larger surface area causing more beaming issues. A phase plug doesn't move with the diaphragm, so it's not considered part of the Sd of the driver.


It's not actually the SD of the cone that causes beaming, well not entirely. It's the maximum distance between any two points you can draw upon the cone. Technically if you could increase surface area, but keep the maximum distance between any two points on the surface area the same, it would beam at the same frequency.


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## Electrodynamic (Nov 27, 2007)

T3mpest said:


> It's not actually the SD of the cone that causes beaming, well not entirely. It's the maximum distance between any two points you can draw upon the cone.


So if it's not the Sd of the cone, and more of the maximum distance between any two points you can draw upon the cone, why did Vifa abandon their drivers that exemplified that exact principle almost a decade ago? And why don't more manufactures do the same thing today?

Beaming involves many factors which include cone material, curvature, mass, and inductance (positive and negative inductance variations over stroke). The maximum distance between any two points plays a role, but it's not the only determining factor.


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## T3mpest (Dec 25, 2005)

Electrodynamic said:


> So if it's not the Sd of the cone, and more of the maximum distance between any two points you can draw upon the cone, why did Vifa abandon their drivers that exemplified that exact principle almost a decade ago? And why don't more manufactures do the same thing today?


They do do the same thing.... That's the point of a line array as I mentioned above. Multiple drivers or one driver, it doesn't matter. IT's all radiating the same energy so you can simply view it as one cone, but with a square shape essentially. The surface area goes up and you can control the directivity by having it beam vertically since the tops and bottoms begin to cancel out very early, relative to it's horizontal dimension, which is only the size of one speaker.


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## T3mpest (Dec 25, 2005)

Electrodynamic said:


> So if it's not the Sd of the cone, and more of the maximum distance between any two points you can draw upon the cone, why did Vifa abandon their drivers that exemplified that exact principle almost a decade ago? And why don't more manufactures do the same thing today?
> 
> Beaming involves many factors which include cone material, curvature, mass, and inductance (positive and negative inductance variations over stroke). The maximum distance between any two points plays a role, but it's not the only determining factor.



It's basically the only determining factor, like 99% of it. Curvature can bring your furthest points in a little bit, so compared to flat surface, you can get the same SD, but beam slightly higher in frequency since the furthest two points are closer if we hold sd constant. Inducantance determines HFE,but not due to actual beaming, the driver simply isn't putting out the frequencies to begin with. If it's due to beaming, you could actually block off the bottom half of the driver and measure with a mic, the sound would be outputted, it's just being cancelled off. Or measure really close up. That's basically what a phase plug does, keeps something in between to disperse the higher stuff that it can control. That's why a phase plug does quite a bit, but everything else won't. A phase plug eliminates cancellation via reflection. After all, why else would you be able to reduce SD yet INCREASE effeciency at high frequencies? You said it yourself the phase plug isnt' going anywhere, yet it adds output up high. It goes this by bouncing around ouput from the edges that would normally be destroyed.

You can test it yourself. Go pick any random driver with no phase plug. It will begin to at a frequency of 13500/size of speaker in inches. That's because 13500 is the speed of sound in air inches. The size of the speaker is the maximum distance between any 2 points on the circle. Lol, had speakers been more commonly rectangles it been a rectangle, the plots would be different depending on what dimension you look at, like I mentioned with line arrays, which approximate the same thing.

here's a random fullrage off madisound. You'll note at between 5 and 6000hz the off axis response plummets. 13500/2.5=5400hz. Obviously the radiating surface area isnt' exactly 2.5inches part, but as always, it gets you close.

Vifa NE85W, 2.5" Fullrange Driver, 4 ohm from Madisound


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## splicer (Oct 4, 2008)

Electrodynamic said:


> Beaming involves many factors which include cone material, curvature, mass, and inductance (positive and negative inductance variations over stroke). The maximum distance between any two points plays a role, but it's not the only determining factor.


I think it's fairly obvious that mass and inductance can affect frequency response but the idea that they affect beaming is kind of out there. Two identically shaped cones moving identically are going to beam the same. The air does not care what is causing the cone to move, only that it moves.


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## splicer (Oct 4, 2008)

I keep wondering what the point of ring radiators is.
I thought it might be like a phase plug. but it looks like their high end dispersion is worse than a normal tweeter. I don't know why that would be, and why it would be desirable.


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## Electrodynamic (Nov 27, 2007)

splicer said:


> I think it's fairly obvious that mass and inductance can affect frequency response but the idea that they affect beaming is kind of out there. Two identically shaped cones moving identically are going to beam the same. The air does not care what is causing the cone to move, only that it moves.


The cone material, more importantly how strong it is, and shape of the cone have an impact on beaming because both of the latter can make the effective diameter smaller.

I was thinking about larger diameter drivers where inductance issues wouldn't even allow the driver to get to the point where beaming comes into play (as T3mpest pointed out).


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## Mr.Anonymous (Jun 12, 2011)

Sorry to dig at old topics, but what about a mid driver shaped like this?










They are not automotive speakers, the top are KLH and bottom are RCA...I'm assuming the KLH mid driver will throw higher frequencies/can not go as low as the RCA??


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## strakele (Mar 2, 2009)

Whizzer cones like those pictured above are designed to combat some of the issues discussed earlier in this thread regarding high frequencies being more easily formed closer to the voice coil. The additional smaller cone attempt to help the speaker play higher by taking advantage of that fact.

The speakers that came stock in my car look almost exactly like the one you posted.


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## Mr.Anonymous (Jun 12, 2011)

Would that put forward a downside over the bottom driver? It will help produce higher frequencies but...why? There is a tweeter there shouldn't the mids driver be focusing on throwing mids or are you talking about high frequencies within the mid-range?

Would the top driver technically have a wider fq range then the bottom? If it does better with higher fq does this mean it will suffer on low frequencies compared to the bottom driver??


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## Hanatsu (Nov 9, 2010)

Don't think it affects LF much at all. LF is all about moving air, cone area * Xmax. As long as Sd isn't affected the lows should be about the same.

Sent from my Samsung Galaxy 3 via Tapatalk.


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## Mr.Anonymous (Jun 12, 2011)

I am going to disconnect the tweeters then and go mid driver for driver and see if I can hear some differences. I am wondering if they will sound better stacked like this...granted each side will have two tweeters I will have two different style mid driver designs and possibly it will help with reproducing an even wider frequency range than any single enclosure by itself either top or bottom (although I did go one for one between them before with the tweeters connected as is and the bottom enclosures sounded wider and more crisp on the highs/symbols).

EDIT: "You may be surprised to learn that even many of the premium or "name brand" factory systems we've seen rely on these little paper megaphones to handle the highs. The result is sound that's dull and lifeless."<---from Crutchfield. Don't know why you would need "whizzer cone" when you got tweets."


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## minbari (Mar 3, 2011)

as others have said. beaming is all about diameter, period! you could take a 10" sub with massive LE that wont play effectively above 100hz and it will still beam at th esame freq as a 10" PA speaker. it may not be as evident, since it wont play high enough to hear it, but it is still doing it at the same freq.


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## Mr.Anonymous (Jun 12, 2011)

I'm just trying to make the best out of what I have around for a computer desk system I have a spare receiver around. 

Instead of just the bottom cabinets I'm trying to improve them with the tops, I think these might have passive in-line crossovers in the cabinets prob just for the tweeters. If so I could run the top driver at full range since it has a whizzer and solder in a crossover for the bottom driver to run a bit more like a mid bass?

They both have 3.5" drivers so they can be swapped from one enclosure to the other as well.


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## Brian Steele (Jun 1, 2007)

T3mpest said:


> Technically sound is produced from all parts of the speaker. A phase plug is used to prevent this fact from
> having a speaker lose output due to points on each edge the speaker cancelling out when wavelengths become small vs size of the cone. At least as I remember learning from Lycan's old threads on beaming.


Correct, hence the name PHASE plug. They're not only used on drivers, btw. Have a look at HF horns, even many tweeters (it's hard to find a mylar tweeter WITHOUT a phase-plug, for example). They might be implemented differently depending on the driver or system, but they're purpose remains the same. 

See Phase plug - Wikipedia, the free encyclopedia for more information.

I think some on this thread are confusing this effect with cone breakup, which is something else entirely, and is dependent upon things like cone material, surround material, etc., but also affects the high-frequency response of the driver.


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## Mr.Anonymous (Jun 12, 2011)

Brian Steele said:


> Correct, hence the name PHASE plug. They're not only used on drivers, btw. Have a look at HF horns, even many tweeters (it's hard to find a mylar tweeter WITHOUT a phase-plug, for example).


Not sure if my tweeter is mylar or not, but mine have no phase plugs:


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## Brian Steele (Jun 1, 2007)

Mr.Anonymous said:


> Not sure if my tweeter is mylar or not, but mine have no phase plugs:


That little grey thing in the middle? It's a phase plug .


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## Mr.Anonymous (Jun 12, 2011)

Brian Steele said:


> That little grey thing in the middle? It's a phase plug .


Oooh lol  kind of like a floating plug rather than physically attached? 

I have headphones and under the foam there is a round sticker in the center of the plastic grill I wonder if it acts similar as a floating plug?


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