Cone tweeters

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454Casull

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Joined 2004
#1
I am interested in the current situation wherein the vast majority of hi-fi tweeters have dome diaphragms. Of course, there are ribbon and ring diaphragms too, but the overall market share is quite low. The reason for my interest is that the dome, especially the fairly shallow ones commonly seen, is not as geometrically "stiff" as a cone, given the same overall height. At least, intuitively that is how it seems to me; the near-flat region at the peak of the dome has little stiffness on its own, whereas a cone or inverted cone should be significantly stiffer and therefore capable of playing up higher in frequency while remaining pistonic.

Thoughts? Is this a manufacturing issue or one of tradition?
 
#2
... i am not shure concerning "stiffness" being "lesser" in a dome.

There are some inverted dome teeters having a voice coil diameter smaller than the dome itself:

http://vintage-audio-laser.com/photofo/hornman/div/t120k-01.jpg

The "traditional shape" in making a tweeter is - in fact - the cone tweeter:

http://www.conrad.com/medias/global/ce/3000_3999/3300/3330/3330/333077_BB_00_FB.EPS_1000.jpg


But there are also modern versions, this one is from Davis:
http://www.parts-express.com/Data/Default/Images/Catalog/Original/277-350_HR_0.jpg

There has been a review of this tweeter in "Klang + Ton, Heft 3/2012 (April/Mai)"
 
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#6
LineArray said:
... i am not shure concerning "stiffness" being "lesser" in a dome.

There are some inverted dome teeters having a voice coil diameter smaller than the dome itself:
Click to expand...
Crudely speaking, if you put your finger on the tip of a dome, it is obviously rather easy to deflect (and dent, in the case of a metal dome). However, if that dome were coming to a peak, as if it were almost like an inverted cone with a rounded tip, would it not be much more resistant to deflection?

Yes, reducing the amount of cantilevered material does seem to be a good approach to increase the overall stiffness. Focal's driver designers have historically appeared to be quite competent, though I can't quite say the same for their cabinet people.
 
#7
Peerless used to have (no longer in production) an excellent little cone tweeter,
the CT62-H. PP cone with ferrofluid, useable from 3.5-4 kHz. In my memories their sound was better than most run-on-the- mill soft domes. With some luck you might be able to get some NOS stock if you look hard enough.
 

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#8
dragonweed said:
Peerless used to have (no longer in production) an excellent little cone tweeter,
the CT62-H. PP cone with ferrofluid, useable from 3.5-4 kHz. In my memories their sound was better than most run-on-the- mill soft domes. With some luck you might be able to get some NOS stock if you look hard enough.
Click to expand...
Unfortunately the size of cone tweeters is typically larger than for domes, and off-axis response suffers as a result.

I would love to see a 1" cone tweeter built with a contemporary motor.
 
#9
Bottom of page 4:

http://resources.prismsound.com/tm/LOUDSOFT_Cones_stiffness_ALMA_2003.pdf

The 3D plot in Fig. 7 of the mode at 1700 Hz reveals that the outer edge of the cone + surround is breaking up and moving out of phase with the main part of the cone above 1700 Hz. This behaviour is causing the well-known “Edge hole” due to lack of geometrical stiffness along the flat cone edge.
Click to expand...

A flat cone edge is not completely different than the flat peak of a dome.

Also see page 7 here:

http://www.loudsoft.com/artikler/1 in Tweeter + System Design _VOICECOIL_2.pdf
 
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#11
454Casull said:
I am interested in the current situation wherein the vast majority of hi-fi tweeters have dome diaphragms. Of course, there are ribbon and ring diaphragms too, but the overall market share is quite low. The reason for my interest is that the dome, especially the fairly shallow ones commonly seen, is not as geometrically "stiff" as a cone, given the same overall height. At least, intuitively that is how it seems to me; the near-flat region at the peak of the dome has little stiffness on its own, whereas a cone or inverted cone should be significantly stiffer and therefore capable of playing up higher in frequency while remaining pistonic.
Click to expand...

Why is this necessary? 1" aluminum domes are already pistonic to above 20khz, and few adults can even hear above 16khz - and as far as markets go, few children / teenagers can afford hi-fidelity loudspeakers.
 
#12
There is a proverb in my country saying: "you can feed the goat and save the cabbage". This is unfortunately not quite true in audio, but there is a solution to this problem, the ring radiator tweeter, which is neither a dome or a cone but has the advantages of both of them.
Since it is a "bending mode" transducer it is free of the oil-can mode of the tweeters, and the edge reflection resonance of cone tweeters. The SB29 RDC and the Satori tweeter from SB Acoustics are excellent examples of this kind of transducer, having very low resonance, super linear response well beyond 20kHz, and no trace of any kind of resonance in their upper range. If you had the chance of hearing them, you will know what I am talking about. The 29RDC has a very reasonable price for its quality (around 50USD).
 
#14
454Casull said:
Also see page 7 here:

http://www.loudsoft.com/artikler/1 in Tweeter + System Design _VOICECOIL_2.pdf
Click to expand...
Only did a quick scan through mostly reading the pics and captions. This looks like a very good paper to learn about the limitations and compromises of speakers.

It also shows a FEM prediction of 1.9T in the gap.
A recent design by another Member claimed that using a neo magnet in the pole could not get above ~0.5T.
How wrong was his modeling?

Edit.
Post9 is the original link location.
I quoted the original post but deleted the wrong half. I corrected that error by:
I copied the two lines in one copy action and pasted them into my post edit.
It seems the Forum software corrupts the copy and pastes in a shortened version of the address.
Separate copy location for the address and paste in that copied address solves the problem
 
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#15
I guess you meant 1000 Hz, or 1 kHz...... For a TWEETER (dome or cone or anything else) 1kHz is technically rather difficult, since that frequency is midrange territory.
There are some smaller size -3-4"- widerange drivers (mostly cone types, like Jordan, Alpair or Fostex) that can handle that range, but they are not dedicated for tweeter role. To reproduce 1 kHz without distortion AND having good dispersion is pretty difficult -as far as I know. Some exotic types, like widerange ribbons or the Manger drivers are able to do that but with a very high price tag.
 
#16
Hahah yes of course... even my dog can not ear 1000 K !

I saw one or two of SB and SS can be xo at 1000 hz but agree : too much close of the Munson-Fletcher 2k to 5 k hz danger zone for the Xo.... But maybe modern active devices with slope higher than LR4 ?

Today if I would use a dome I XO it at more than 5 K or 6K hz because of that and the XO interactions with the M-F zone.... In theory of course because many speakers using the two drivers you spoke about seem to have a beautifull sound...
 
#17
AndrewT said:
Only did a quick scan through mostly reading the pics and captions. This looks like a very good paper to learn about the limitations and compromises of speakers.

It also shows a FEM prediction of 1.9T in the gap.
A recent design by another Member claimed that using a neo magnet in the pole could not get above ~0.5T.
How wrong was his modeling?
Click to expand...

Hi Andrew,

The link doesn't work : I surmise an error of paste & copy in the post !
 
#19
In my speakers I have aluminium cone but no rear chamber as the tweeter is a original Boston acooustic which use partially the rear wood chamber of the cabinet. The driver have lateral open holes but no cavity just Under the dome like the best ScanSpeaks.

After readed Troels link you gave some months ago : i puted a little medical cotton Under each dome taking care to not sealed the round gap with ferrofluid in it ! A big luck as the sound had a big jump in quality !

I surmised placebo & psychological but maid a sound test with my family and close friends who know my systeme very well : no doubt, the sound is better !

What is better for mid-tweeter than the best dome of ATS, Dynaudio instead cone like the Scan Speak 10 F or small Mark AUdio e.g. used in this spirit ?

@t Andrew :sorry for false alert, the link works now... I surmise a break in my home wifi for few minutes...verry poluted wifi environment at home !
 
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