Should be
".. show little or no advantage of hyperboloids compared to slightly curved cones."
See also: FINECone - Speaker Design software - Products - loudsoft and open the tutorial. his will give bout coen and dome geometry, materials and surrounds.
And for PAFEC: diyAudio server HTTPS page under : PafLS- PAFEC loudspeaker design tool. The examples and graphs on both sites provide a wealth of insight in cone shape and material plus surrounds in relation cone behaviour and break-up.
Good Luck.
Eelco
And for PAFEC: diyAudio server HTTPS page under : PafLS- PAFEC loudspeaker design tool. The examples and graphs on both sites provide a wealth of insight in cone shape and material plus surrounds in relation cone behaviour and break-up.
Good Luck.
Eelco
A hyperboloid is a sort of curved cone, or to be accurate, a cone is a sort of limit case of a hyperboloid.
So I wouldn't expect any miraculous properties, only that it would be easy to fabricate with composites.
Interested to learn that you tested it however.
I have a few questions about the cone breakup, raised by the Button paper.
I will ask them in the other thread where Button has already been referenced.
I knew FINEcone but not this one so thanks for the links.
I can't really justify the expense of this sort of professional software, and it is such a small market that they don't do "non-commercial" licenses for dabblers like me.
What is your involvement in this area?
Best wishes
David
Thanks for this Boden. I'm amused that Peter Larsen & Bob Harris have set up in business. 😀
https://www.youtube.com/watch?v=nlaGb67RPwc&feature=youtu.be
This sorta shows what happens with PAFEC. But Finecone (and Larsen) would appear to be unaware of some important niceties of cone design.
I'm pleased that Mica filled PP is still available. I specified & got ICI to make a batch of Mica filled PP sheet in the 80's and we were the first to use it commercially in speakers.
The main improvement that Larsen shows with the dust cap is in fact sticking it directly to the coil former.
His final 'real life' blue curve shows a surround resonance which implies Finecone doesn't do surrounds properly which is a big failing.
I wish I still had my SCAnned Laser animated Plots from the last Millenium of this type of work. 😡
_________________________
None of this is really of use to you Dave. It's about midrange performance which IMHO, is still black magic. Da giarnomous JBL type subs are really Civil Engineering 😀
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There is good free software around for structural vibration such as Salome+CodeAster. It is not as easy to use as expensive commercial software but is not too bad either. After you have invested some time writing a few scripts to do roughly what you want things can speed up quite nicely.
The acoustics side is less well served but there is some free software out there. There are number of FEM codes that can solve the 3d Helmholtz equation. The one or two BEM codes that are around like Acousto tend to use only the lowest accuracy elements (which avoids having to handle a whole bunch of numerical issues). This can be an issue for realistic geometries given the number of elements is fairly small before BEM starts to require too much memory and CPU time to solve.
I don't know how old that website is given it talks about PAFEC-FE being an "established tool for well over 25 years" and yet I recall using PAFEC software 35 years ago. They seem to be in the same location as when I briefly had something to do with them. This article claims they had 350 employees in the 80s but that does not look like the website of a software company with 350 employees. The company also seems to have changed it's name more than once. Interesting to see how the company evolved.
This is a very old thread by now, but just wondering after all those years: @Dave Zan: did you finally found what you were looking for?
I'm not a transducer designer but voice coil magazine is good to subscribe to for information about driver design and manufacturers of loudspeaker components:
Voice Coil Magazine | audioXpress
The impression I get is that if your making a low frequency speaker you can make almost anything from a selection of off the shelf coils, magnets, frames, spiders etc. The black art seems to be Adhesives that can withstand high temperature and dry quickly enough for assembly line usage.
Voice Coil Magazine | audioXpress
The impression I get is that if your making a low frequency speaker you can make almost anything from a selection of off the shelf coils, magnets, frames, spiders etc. The black art seems to be Adhesives that can withstand high temperature and dry quickly enough for assembly line usage.
Yes, "Voice Coil" does have useful information, thanks for the reminder.
But I had hoped for a systematic explanation in a book, similar to Cordell for amplifiers.
There is indeed quite a selection of off-the-shelf stuff but I suspect I would have to place a minimum order that was quite expensive to have them make what I want.
I don't think adhesives are such a black art, the state of the art seems to be thermoset polyimides, just expensive and not consumer orientated.
Actually, one of my ideas was for a driver optimised for Multiple Entry Horns.
I know you have done some work on these, Interested to discuss it?
Not really, sorry to say, do you have any new recommendations?
As I wrote above, I think some of what I want could be obtained, if I wanted to spend serious money for a minimum order.
I have started to mess around with the freeware Boundary Element Model acoustics in the search for a better horn.
The Kolbreck book on horns looks excellent, I await a paperback edition.
If my next contract pays well maybe buy the expensive hard cover.😉
Best wishes
David
The horn book is very good, there is also some information about drivers (particularly the Axi2050) but its not driver design orientated or the main focus of the book.
A drive optimized for MEH? do you mean a midrange driver? for me this would have the following features:
1) low total height so that even for smaller horns the box holding the horn doesn't have to be larger than the horn
2) inverted dust cap to simplify phase plug design
3) ~4" diameter cone
4) inverted surround
5) Sealed back chamber without damping material and good thermal path
6) very stiff and light cone, damping not very important as resonance should be filtered by bandpass chamber, Perhaps carbon fiber? should also avoid breakup behavior from the cone until at least 3kHz
7) Very powerful motor to push mass break frequency as high as possible, perhaps ironless motor is possible?
8) I don't think much excursion capability is required the SH-96HO which is quite an extreme MEH with 15" woofers has a crossover frequency to the 4" mids of 500Hz.
A drive optimized for MEH? do you mean a midrange driver? for me this would have the following features:
1) low total height so that even for smaller horns the box holding the horn doesn't have to be larger than the horn
2) inverted dust cap to simplify phase plug design
3) ~4" diameter cone
4) inverted surround
5) Sealed back chamber without damping material and good thermal path
6) very stiff and light cone, damping not very important as resonance should be filtered by bandpass chamber, Perhaps carbon fiber? should also avoid breakup behavior from the cone until at least 3kHz
7) Very powerful motor to push mass break frequency as high as possible, perhaps ironless motor is possible?
8) I don't think much excursion capability is required the SH-96HO which is quite an extreme MEH with 15" woofers has a crossover frequency to the 4" mids of 500Hz.
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Nice list, many are more or less in accord with what I had in mind, some are points I hadn't considered.
Just to reply to a few that I'd like to work thru.
3) The 4" diameter seems suitable for a 3 way but for my own use I had in mind a 4" voice coil 1.5" exit compression driver crossed pretty low - so I could perhaps use a 10" (or thereabouts) and cross directly to the subs.
JBL have some drivers optimised for line arrays, essentially linear MEH horns.
The parameters look excellent so I am surprised no DIYer seems to have used them.
They are expensive, of course, but there's usually someone who buys "cost no object".
the latest iterations are the -
2163 (3")
2164 (4") there's an AES paper on this one, has copper pole caps, aluminium Faraday face-plate, aluminium anti-flux-modulation at the pole base, extra copper shorted turn on the pole faces - more or less every trick known to science and the measurements look excellent.
This does seem to fit your specs so if you didn't already know about it then I think you should buy one to satisfy your curiosity (and mine)😉
2165 (5.5") A Dual Differential Drive so should be even less prone to 2nd harmonic distortion than the 2164. There's an AES paper that compares the two but I haven't read it yet.
2169 (8") Another DCD driver, most BL/Re that I have seen for a driver this size.
5) Sealed back chamber is a nice convenience to isolate the driver.
It doesn't help the actual performance AFAIK, most of the thread on the "best MEH driver" appears to be based on a misconception.
6) Yes, stiffness would be nice.
That carbon driver has a fairly nasty break-up.
I know the bandpass will help filter it but better if it was not even there.
As I said in post #18, these pressed loom woven fabrics always look sub optimal to me, should be radially braided or filament wound or some such.
Or a laminated cone would be nice.
7) Definitely a powerful motor, the JBL's are excellent, not sure why there seems to be almost no others that really try hard here - sub-optimal VC and pole dimensions.
But I don't see why an ironless motor would help?
8) Yes, I don't understand why no one seems to exploit this fully.
If the excursion is limited then it makes practicable the better VC and pole dimensions mentioned above.
Best wishes
David
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I'm most interested in 3 way because obtaining good loading for compression drivers below 1kHz is difficult without a horn contour that beams high frequencies. Check out these horns:
ATH - CE Series
as they increase in size the corner of real radiation resistance is not moving down in frequency very much.
These JBL drivers seem interesting do you know where the datasheets are located I can't find any info with a cursory search?
I'm not sure on back chamber sizing if its anything like a FLH the optimal size can increase sensitivity (efficiency?) around the low frequency corner. There needs to be one regardless for a mid though as almost all MEH apart from two ways need to isolate the mid drivers.
Stiffer cone means lower distortion in the pass band though and some very stiff and light materials (ideal to reduce cone mass) have poor damping so its all a trade off.
After a bit of reading around ironless motors I think I got confused as I thought they offered a path to greater gap flux but this is not the case. I've never designed a loudspeaker motor but if compression drivers can get 2.2T in the gap why can't a mid-range achieve this? is it simply what is possible with the larger gap?
ATH - CE Series
as they increase in size the corner of real radiation resistance is not moving down in frequency very much.
These JBL drivers seem interesting do you know where the datasheets are located I can't find any info with a cursory search?
I'm not sure on back chamber sizing if its anything like a FLH the optimal size can increase sensitivity (efficiency?) around the low frequency corner. There needs to be one regardless for a mid though as almost all MEH apart from two ways need to isolate the mid drivers.
Stiffer cone means lower distortion in the pass band though and some very stiff and light materials (ideal to reduce cone mass) have poor damping so its all a trade off.
After a bit of reading around ironless motors I think I got confused as I thought they offered a path to greater gap flux but this is not the case. I've never designed a loudspeaker motor but if compression drivers can get 2.2T in the gap why can't a mid-range achieve this? is it simply what is possible with the larger gap?
Yes, I follow that thread attentively.
I was also surprised by this, on the other hand Earl claims it hardly matters.
I respect his expertise but would like to understand this better.
It's partly that thread that makes me think that it may be possible to fix most of the upper frequency beam width problems of a 1.5" exit CD.
That would allow the use of a 4" VC driver - with the capacity to cross fairly low and make a 2 way practicable, for home hi-fi any way.
They are for internal use in the JBL branded line arrays, not intended as a separate sales product so no datasheet as such.
Most are included in the Thiele/Small parameter list that JBL publish so you can at least find the important specifications.
As mentioned above, some details published in the AES if you have access to their library- Author = Voishvillo (from memory, can find links if you need them)
The low frequency corner use in classic FLH horns is not applicable to typical MEH, as far as I can see.
In a FLH it can interact with throat reactance to help response.
I suspect with a typical MEH that it's not useful but I'm not absolutely sure.
But it doesn't help with the top end, which is what people seemed to think in the "Best MEH driver" thread.
The isolation is useful, of course.
I have an idea for a laminated cone that would be both stiff and well damped.
It's the piece that I think I could order if I wanted to put up serious money up front. Not sure of the demand.
It is certainly possible but the manufacturers don't bother, presumably don't think there's much demand or that people know the difference.
Except the JBLs, I can't find any drivers built the way that seems obviously best - ribbon aluminium VC in an extended, ~ 2T field with copper pole caps and anti flux modulation (Faraday) components.
It needn't be so much more expensive.
Best wishes
David
Hello Dave,
Much of what is written here is or has been on my mind as well: both cone and motor musings. But how and where would you obtain a single or couple of laminated cones?
Also, I have been thinking about optimizing or improving existing motors. The main hurdle -as I see it - is how to take an existing motor apart without destroying or demagnetizing it. The Purify 2-3 layer voicecoil is another trick that deserves further study.
Furthermore, I would love to see a proper phase-plug design for a 2" wideband cone-dome driver such as e.g. the Peerless PLS-P830983 to mate it with an 1.4" waveguide a la Mabat.
Much of what is written here is or has been on my mind as well: both cone and motor musings. But how and where would you obtain a single or couple of laminated cones?
Also, I have been thinking about optimizing or improving existing motors. The main hurdle -as I see it - is how to take an existing motor apart without destroying or demagnetizing it. The Purify 2-3 layer voicecoil is another trick that deserves further study.
Furthermore, I would love to see a proper phase-plug design for a 2" wideband cone-dome driver such as e.g. the Peerless PLS-P830983 to mate it with an 1.4" waveguide a la Mabat.
I am reassured to have someone else in accord.😉
Because the speakers I have seen look less than optimal and I don't understand why no one does better, except perhaps JBL.
Maybe I over estimate the demand, or maybe it's just "that's the way everybody does it" and laziness.
Kurt Müller company make both paper and metal speaker cones and will make to order so I assume they would make a laminate.
Probably other companies also could do this, not sure who else does both metal and paper cones.
The problem is that I suspect there would be some minimum order, and not cheap, especially an EU company like KM.
Some of the smaller manufacturers would probably built what you want for not totally unreasonable money.
And some speakers come apart with less trouble, Alnico is a problem.
Some of the coax speakers have a nicely modularised construction, made from a pre-built assembly joined to a woofer.
For instance - Macauley used to do this, haven't checked lately if they are still in business.
So the sub assemblies may be usable.
Best wishes
David
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Curious to learn about Kurt Mueller offering small quantities. My experience with Chinese vendors is that they are helpful, but it was extremely difficult to communicate at detail level: I never got exactly what I asked for.
Some 10 years ago there was another German firm claiming to have come up with super break up free cones made of some polymer composite, but they never responded to any sample request and nothing was ever heard of them later on. Forgot the name.
Some 10 years ago there was another German firm claiming to have come up with super break up free cones made of some polymer composite, but they never responded to any sample request and nothing was ever heard of them later on. Forgot the name.
Their website indicates they do custom production but I don't know what their minimum order is.
You are in Europe, not far from them, call them up and satisfy both our curiosities😉.
There has been some recent claims for UHMW polythene.
Looks to be a reasonable possibility for home hifi, maybe softens at too low a temperature for loud PA/concert use.
Best wishes
David
I have frequent problems to access DIYaudio, response too slow and the browser times out, sorry for any slow responses to posts.