So in a wayyou took the "easy" path
You just built a "dedicated magnetizer" and made it part of the speaker.
Yes, I have assembled motors with already magnetized PM and it is a pain to precisely align it. This way, it could be done but to no real value. For DIY especially tho, field coil is the way.
Thank you for posting about magnetizers. Before starting this project i looked after information and couldn't find any and then i looked after field coil information and couldn't find much on these either. You are right, magnetizers are a dangerous things.
Would sure like to hear more about the 30" speaker and your current works.
Well, all work on those monsters was lost long ago. (around '82/'84 or thereabouts)
My personal contribution was designing the fieldcoil and the PSU.
All done with paper, pencil, graphs and calculators
No computers (original PCs had *just* appeared, with whopping 128KB of memory, no hard disk and only 1 or 2 360KB floppies), so no software and even less simulation.
And Gauss could not be measured directly, for lack of proper sensors.
So measurement was tedious total flux (in maxwells) measuring with a scanning coil which fed an Op Amp integrator, and dividing said flux by gap area.
The first idea was that these would sell like hot cakes.
It didn't happen, so second best was to *rent* them to dance clubs to provide "thump".
Fine, but their checks bounced.
Combine that with fired employees suing , banks trying to collect loans, etc. , and you'll have a pale idea of what a mess it was.
I was happy to leave without personal debt and having signed no contracts.
Oh well.
But the Bass was gut-wrenching
As of today I just make perfectly standard Guitar and Bass speakers (think Jensen/Celestion/Eminence) for my own commercial use; I also supply small custom builders and export a little to neighbouring Countries.
My personal contribution was designing the fieldcoil and the PSU.
All done with paper, pencil, graphs and calculators
No computers (original PCs had *just* appeared, with whopping 128KB of memory, no hard disk and only 1 or 2 360KB floppies), so no software and even less simulation.
And Gauss could not be measured directly, for lack of proper sensors.
So measurement was tedious total flux (in maxwells) measuring with a scanning coil which fed an Op Amp integrator, and dividing said flux by gap area.
The first idea was that these would sell like hot cakes.
It didn't happen, so second best was to *rent* them to dance clubs to provide "thump".
Fine, but their checks bounced.
Combine that with fired employees suing , banks trying to collect loans, etc. , and you'll have a pale idea of what a mess it was.
I was happy to leave without personal debt and having signed no contracts.
Oh well.
But the Bass was gut-wrenching
As of today I just make perfectly standard Guitar and Bass speakers (think Jensen/Celestion/Eminence) for my own commercial use; I also supply small custom builders and export a little to neighbouring Countries.
I always assumed that the Aura NeoRadial had to be assembled with the magnet already at full force, so a similar requirement for a reversed pole structure didn't seem too impractical. Now you have made me wonder if I was correct.
Thanks for the information from real, practical experience. Sorry it did not turn out better.
Best wishes
David
Thanks for the information from real, practical experience. Sorry it did not turn out better.
Best wishes
David
Just checked the Aura Radials.
Yes, in that case, it *has* to be magnetized "outside".
But because of the 90º magnetic angle, it's not that difficult to mount it in the iron structure, I imagine a "guide tube" to lower it straight, centered, into its place so magnetic force sort of self-equalizes.
Sometimes I have to re-glue shifted ferrite rings, obviously magnetized, and it is murder because pull force is axial, and the iron disks are exactly in the path.
Talk about nicked fingers and cursing!!!
Worst is that you have to work in a hurry, because epoxy is already applied and curing fast
As of the commercial aspects, the only way of avoiding failure is not trying
Yes, in that case, it *has* to be magnetized "outside".
But because of the 90º magnetic angle, it's not that difficult to mount it in the iron structure, I imagine a "guide tube" to lower it straight, centered, into its place so magnetic force sort of self-equalizes.
Sometimes I have to re-glue shifted ferrite rings, obviously magnetized, and it is murder because pull force is axial, and the iron disks are exactly in the path.
Talk about nicked fingers and cursing!!!
Worst is that you have to work in a hurry, because epoxy is already applied and curing fast
As of the commercial aspects, the only way of avoiding failure is not trying
Oh, I have tried so often and so many times that I have been continuously successful on something for the last 43 years or so.
Paid houses, cars, factory, machines, trips, etc., everything out of my successful products.
And sank a lot of money on bad moves too.
Never betting everything on a single card.
Never ever worked for anybody or got/needed a salary since I was 16 , always living from building and selling Electronic products.
The balance was always positive , although many times not wide enough.
Now and then old friends/colleagues visit my shop, to drink a few "mates"
Al dream about "grabbing the soldering iron " again.
One good principle was letting go something when it became unsalvegeable.
Trying to fill a "black hole" is MUCH worse than trying something else.
And yes, that speaker was more than "inspired" in the EV, but with much larger VC (100 mm/4") which forced us to use a field coil.
It also had much higher power handling, about 200/250W RMS which at the moment was groundbreaking.
Roundwire VC on an anodized aluminum former.
Never measured it.
Technology-of-the-day mandated Brüel&Kjäer equipment inside an anechoic chamber.
A BIG one at that.
As I said, no easy simulation way back then ... but it could hold its own and integrate with 15" PA woofers which now we know were around 95/96dB efficient, so it must have been close to that.
Couldn't agree more.
Thanks for sharing your thoughts, very helpful for a youngster like me.
Hi, Hentai
Wonderful work! I would be interested to know your critical opinions of the driver you have made here: an impression, if you will. You know, strengths and weaknesses, what you like and dislike about the sound of them, and the like.
Also, I would be entirely grateful if you would be kind enough to post a bibliography of sorts. I also am interested in making my own field coil (and with paper cones) but information is seemingly impossible to come by. When info is found, it is broken fragments of disconnected gibberish: nothing comprehensive, no "Bibles of the craft".
There was once a sight where more than several persons were involved in such craft, but I can not find it anymore.
The first request, of a first impression, I am asking of you. The second request, a list of 'must reads' I am asking of everyone who has it to offer here.
I hope this isn't to be considered a hijacking of the thread, but I must say, I can't think of a better place for it. I wwould really like to read what you have studied in the process of originating this really Beautiful work. ciao
Wonderful work! I would be interested to know your critical opinions of the driver you have made here: an impression, if you will. You know, strengths and weaknesses, what you like and dislike about the sound of them, and the like.
Also, I would be entirely grateful if you would be kind enough to post a bibliography of sorts. I also am interested in making my own field coil (and with paper cones) but information is seemingly impossible to come by. When info is found, it is broken fragments of disconnected gibberish: nothing comprehensive, no "Bibles of the craft
There was once a sight where more than several persons were involved in such craft, but I can not find it anymore.
The first request, of a first impression, I am asking of you. The second request, a list of 'must reads' I am asking of everyone who has it to offer here.
I hope this isn't to be considered a hijacking of the thread, but I must say, I can't think of a better place for it. I wwould really like to read what you have studied in the process of originating this really Beautiful work. ciao
Hello nottolkien,
Thank you for your words.
My impressions, hmm i stayed away from that as i tried to keep it things objective as ofc i cannot show how it sounds on a forum but since you asked...
The best thing this speaker does is dynamics and is something i always crave for in sound. I belive it is one of the most important characteristics that gets you closer to the "live" sound. When i play Pink Floyd "More Blues" and Nick Mason hits that snare drum like there's no tomorrow i get goose bumps, it just bites you. Aphrodite's Child "The Four Horsemen" disables gravity field, the sound is full, tons of impact. Another thing i enjoy is the midrange, it really captures the meat of the instrument. I like Japanese music and that Japanese flute sounds really good. Van Morrison "Stranded", Archie Shepp "Thrill is gone", New American Orchestra's take on Vangelis' "Blade Runner Blues", Hugh Masekela "Stimela" and Mike Figgis "Leaving Las Vegas" sounded thin and unconvincing in the midrange on most 6.5"-8" reflex systems. Mine plays it with a great tonal balance and low distortion at low or loud levels.
It lacks a certain precission in timbre as of yet, even if keeping balance in tone. I've been working on designing the cone, a new cone that will bring me closer to a certain neutrality. On the upper midrange there are some rather abrupt changes in response (4-5 dBs but over a short frequency range) and anything abrupt is not good.
Another aspect that one should consider is that this driver should be horn loaded. OB is a choice but i found lower current through field coil to achieve higher Qts muddies the sound, easily noticeable from songs with rather busy and lots of instruments, they all get lost in a cloud somewhere. So horn loading is the way to go. Now, to some, this might be a weakness, to some it might be a strength.
For classical music the high frequency extension and sound might please many. I had some friends, lovers of classical genre and no one felt the need of supertweeter, in fact they disliked it when it was added but i do admit it might not have been the best implementation. For blues/rock/jazz i think a ST is a good addition.
To compile a bibliography is a pretty difficult and time consuming task. I've been interested in designing drivers for many years. The work on this project started in december 2011. In my research i found so little about the design of drivers themselves unlike the tons of info on loudspeaker design. So basically you need to return to physics and work it up from there. Very useful is modeling and analogies to electrical circuitry. You can take the whole electro-mechano-acoustical assembly and model it as an electrical circuit and then run analisys just like normal filters. It helps to see transfer function of the system and model it to suite what you desire.
The first recommendation would be my bible: Acoustics by Leo Beranek. Something less technical but offering some interesting information and insights is High Performance Loudspeakers by Martin Colloms.
Papers published by manufacturers like JBL,EV or from people like Don Keele offer good information as well. Studying market drivers that are close to what you have in mind will provide perhaps more information than anything else though.
In closing my comments, some pics of the frame parts:
Thank you for your words.
My impressions, hmm i stayed away from that as i tried to keep it things objective as ofc i cannot show how it sounds on a forum but since you asked...
The best thing this speaker does is dynamics and is something i always crave for in sound. I belive it is one of the most important characteristics that gets you closer to the "live" sound. When i play Pink Floyd "More Blues" and Nick Mason hits that snare drum like there's no tomorrow i get goose bumps, it just bites you. Aphrodite's Child "The Four Horsemen" disables gravity field, the sound is full, tons of impact. Another thing i enjoy is the midrange, it really captures the meat of the instrument. I like Japanese music and that Japanese flute sounds really good. Van Morrison "Stranded", Archie Shepp "Thrill is gone", New American Orchestra's take on Vangelis' "Blade Runner Blues", Hugh Masekela "Stimela" and Mike Figgis "Leaving Las Vegas" sounded thin and unconvincing in the midrange on most 6.5"-8" reflex systems. Mine plays it with a great tonal balance and low distortion at low or loud levels.
It lacks a certain precission in timbre as of yet, even if keeping balance in tone. I've been working on designing the cone, a new cone that will bring me closer to a certain neutrality. On the upper midrange there are some rather abrupt changes in response (4-5 dBs but over a short frequency range) and anything abrupt is not good.
Another aspect that one should consider is that this driver should be horn loaded. OB is a choice but i found lower current through field coil to achieve higher Qts muddies the sound, easily noticeable from songs with rather busy and lots of instruments, they all get lost in a cloud somewhere. So horn loading is the way to go. Now, to some, this might be a weakness, to some it might be a strength.
For classical music the high frequency extension and sound might please many. I had some friends, lovers of classical genre and no one felt the need of supertweeter, in fact they disliked it when it was added but i do admit it might not have been the best implementation. For blues/rock/jazz i think a ST is a good addition.
To compile a bibliography is a pretty difficult and time consuming task. I've been interested in designing drivers for many years. The work on this project started in december 2011. In my research i found so little about the design of drivers themselves unlike the tons of info on loudspeaker design. So basically you need to return to physics and work it up from there. Very useful is modeling and analogies to electrical circuitry. You can take the whole electro-mechano-acoustical assembly and model it as an electrical circuit and then run analisys just like normal filters. It helps to see transfer function of the system and model it to suite what you desire.
The first recommendation would be my bible: Acoustics by Leo Beranek. Something less technical but offering some interesting information and insights is High Performance Loudspeakers by Martin Colloms.
Papers published by manufacturers like JBL,EV or from people like Don Keele offer good information as well. Studying market drivers that are close to what you have in mind will provide perhaps more information than anything else though.
In closing my comments, some pics of the frame parts:
Attachments
Recommended texts for Nottolkien
Yes, Beranek is the place to start! I like Olsen too.
Not too much published information on driver theory. Journal of the AES would be my second recommendation.
The JBL papers are helpful but seem to contain a few errors. At first I assumed that JBL was too reputable to have made these mistakes so I must have misunderstood, but eventually decided it was not due to me. Were the papers written by trainees while the real experts did the more important work on actual production? A little misinformation for competitors or just carelessness? There is a handbook by an ex-JBL employee that repeats some of these mistakes.
Don Keele is practically always excellent. The "horn mouth size" paper in JAES is fairly suspect but he is very open about the problems of such old papers.
I believe there are some works in Deutsch and Japanese that are excellent but haven't tracked these down yet.
Best wishes
David
Yes, Beranek is the place to start! I like Olsen too.
Not too much published information on driver theory. Journal of the AES would be my second recommendation.
The JBL papers are helpful but seem to contain a few errors. At first I assumed that JBL was too reputable to have made these mistakes so I must have misunderstood, but eventually decided it was not due to me. Were the papers written by trainees while the real experts did the more important work on actual production? A little misinformation for competitors or just carelessness? There is a handbook by an ex-JBL employee that repeats some of these mistakes.
Don Keele is practically always excellent. The "horn mouth size" paper in JAES is fairly suspect but he is very open about the problems of such old papers.
I believe there are some works in Deutsch and Japanese that are excellent but haven't tracked these down yet.
Best wishes
David
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VoiceCoil magazine had many articles with insights into driver manufacturing most written by Steve Mowry.
F. Fahy - Foundations of Engineering Acoustics, pretty indepth talk about how wave behave when traveling through different materials and shapes. A good study on mechanical and acoustical impedances.
There are many books, none gives a straight forward recipe for designing drivers (probably because there isn't or there are too many).
F. Fahy - Foundations of Engineering Acoustics, pretty indepth talk about how wave behave when traveling through different materials and shapes. A good study on mechanical and acoustical impedances.
There are many books, none gives a straight forward recipe for designing drivers (probably because there isn't or there are too many).
When I studied Engineering in the early 70's, in the whole Career there was only 1 "Electroacoustics" , which was basically learning Beranek's book, cover to cover.
The University library also had an old copy of Olson's book, which I kept for so long that they fined me.
Oh well.
There were also a couple other books, but mostly concerned with Architectural Acoustics.
What I found most useful were articles in British Audio magazines, written by real hands-on guys, such as the Fane Design Chief.
I remember a very clever trick (by Fane) on how to *actually* measure VC resistance increase with temperature, which directly indicated power handling (knowing adhesive performance vs temperature).
Mind you, they read it real time, while playing music !!!
I also read there fror the first time about epoxy-fiberglass formers, pioneered by them.
They were the first to achieve 100W RMS power handling (standard for Celestions, etc. was around 20/30W) *and* real 101dB/W/M efficiency.
When People asks me "what did the University give you" ? my answer is : "50% the formal training, 50% shared between free access to their Library and contact with bright people"
"You can find anything in the Net" is a myth; lots of info (the juiciest part) is NOT published, but can be found in real books and specialized magazines.
The IEEE publications are invaluable, but don't waste time on the "modern" ones, at least for speaker stuff; the best parts are in 50's and 60's magazines, maybe something in the 70's, but not further.
The University library also had an old copy of Olson's book, which I kept for so long that they fined me.
Oh well.
There were also a couple other books, but mostly concerned with Architectural Acoustics.
What I found most useful were articles in British Audio magazines, written by real hands-on guys, such as the Fane Design Chief.
I remember a very clever trick (by Fane) on how to *actually* measure VC resistance increase with temperature, which directly indicated power handling (knowing adhesive performance vs temperature).
Mind you, they read it real time, while playing music !!!
I also read there fror the first time about epoxy-fiberglass formers, pioneered by them.
They were the first to achieve 100W RMS power handling (standard for Celestions, etc. was around 20/30W) *and* real 101dB/W/M efficiency.
When People asks me "what did the University give you" ? my answer is : "50% the formal training, 50% shared between free access to their Library and contact with bright people"
"You can find anything in the Net" is a myth; lots of info (the juiciest part) is NOT published, but can be found in real books and specialized magazines.
The IEEE publications are invaluable, but don't waste time on the "modern" ones, at least for speaker stuff; the best parts are in 50's and 60's magazines, maybe something in the 70's, but not further.
True, thats the period of intensive research in the field. Nowadays R&D engineers have to give up space to copywriters, salesmen, so on and so forth... the known issues.
I had my mind on building instrument that can plot VC temp rise in order to use precise electrical models. Thinking of ways to measure the half-inductance parameters. I might get back on that.
I had my mind on building instrument that can plot VC temp rise in order to use precise electrical models. Thinking of ways to measure the half-inductance parameters. I might get back on that.
Well, they were incredibly simple and clever.
Just quoting from memory (37 years ago), they built an impedance bridge , similar to a Wheatstone bridge , and, watching the V to I phase relationship on a scope, they found a frequency at which the speaker phase shift was 0 , so it could be considered a pure resistor (at that frequency).
It was then easy to directly measure its DC resistance, while actually playing at high volume.
Knowing the copper thermal resistance factor, they could calculate the temperature in real time within 1%.
As a side note, it was a very safe power rating, because at that frequency (which usually was between 250 and 350Hz for a 12" speaker) the impedance was at its minimum (close to rge DC resistance value) and so the speaker was both the heaviest load for the amplifier and at the same time it received maximum power.
At any other frequencies, the reactive component worked as an attenuator.
Clever chaps.
And yes, that was a time of intensive research and they published papers about it.
I do not doubt that today there's research too, but it usually is kept under covers.
Just quoting from memory (37 years ago
), they built an impedance bridge , similar to a Wheatstone bridge , and, watching the V to I phase relationship on a scope, they found a frequency at which the speaker phase shift was 0 , so it could be considered a pure resistor (at that frequency).It was then easy to directly measure its DC resistance, while actually playing at high volume.
Knowing the copper thermal resistance factor, they could calculate the temperature in real time within 1%.
As a side note, it was a very safe power rating, because at that frequency (which usually was between 250 and 350Hz for a 12" speaker) the impedance was at its minimum (close to rge DC resistance value) and so the speaker was both the heaviest load for the amplifier and at the same time it received maximum power.
At any other frequencies, the reactive component worked as an attenuator.
Clever chaps.
And yes, that was a time of intensive research and they published papers about it.
I do not doubt that today there's research too, but it usually is kept under covers.
Hello again
I read some where at the membrane has to flex from the voice coil to the edge at high frequency, due to the low wave length. Is that relay true?..... The speed of sound in solid materials is much higher than air, this means a longer wave length. The speed of sound in solid materials is directly to the density of the material, more dens mean higher speed.
Here is a link that shows the velocity in different materials.
Material Sound Velocities / Olympus
Take care
I read some where at the membrane has to flex from the voice coil to the edge at high frequency, due to the low wave length. Is that relay true?..... The speed of sound in solid materials is much higher than air, this means a longer wave length. The speed of sound in solid materials is directly to the density of the material, more dens mean higher speed.
Here is a link that shows the velocity in different materials.
Material Sound Velocities / Olympus
Take care
Hi Frank, what you are describing is called cone breakup and will happen to all cone drivers.
Once wavelength is smaller than cone diameter, the cone will stop moving like a piston and wave will start traveling from the voicecoil to the outer edge of the cone and back. This so called flexing will cause some specific portions or areas of the cone to move out of phase with the voicecoil and this in turn cause dips and peaks in response.
A higher density material will be stiffer and will push this cone breakup frequency higher but usually its magnitude will be higher also. You will see many aluminum and kevlar cones on the market having a high peak in the 4-5kHz region.
It will need some care when designing filters and failure to do so might result in that sound some call "metalic".
Other manufacturers try to damp these resonance by adding a specific voice coil collar that attenuates the high frequency energy but to me it doesnt seem a natural process, solving something that could very well not be there.
Sound speed in paper how ever is very close to that in air and this probably is what gives this naturalness in timbre. Cone breakup still exists but not so evident as with stiffer materials and with proper cone termination much of the waves traveling through cone can be absorbed without adding mass to voice coil.
So as far as cone drivers are concerned for me there is no other material than paper.
Once wavelength is smaller than cone diameter, the cone will stop moving like a piston and wave will start traveling from the voicecoil to the outer edge of the cone and back. This so called flexing will cause some specific portions or areas of the cone to move out of phase with the voicecoil and this in turn cause dips and peaks in response.
A higher density material will be stiffer and will push this cone breakup frequency higher but usually its magnitude will be higher also. You will see many aluminum and kevlar cones on the market having a high peak in the 4-5kHz region.
It will need some care when designing filters and failure to do so might result in that sound some call "metalic".
Other manufacturers try to damp these resonance by adding a specific voice coil collar that attenuates the high frequency energy but to me it doesnt seem a natural process, solving something that could very well not be there.
Sound speed in paper how ever is very close to that in air and this probably is what gives this naturalness in timbre. Cone breakup still exists but not so evident as with stiffer materials and with proper cone termination much of the waves traveling through cone can be absorbed without adding mass to voice coil.
So as far as cone drivers are concerned for me there is no other material than paper
.
Thanks Hentai, you sure know some good stuff. I have leaned allot from this thread... Thanks.
Some notes:
It was noted that the surrounding of the my unit was to thick, so I removed most of it. There was no audible changes ta all, (I have not access to any measure devices).
I added a aluminium cone to the membrane, this give a higher output at high frequency, more or less logical...... It increases the areal in the centre of the membrane. Buy the way the cone was made from the bottom of a beer can
I have decided not to try to make the unit without a spider.....due to the softness of the edge of the membrane. Instead I will bend the edge abut 90 degrees, to make it mechanical stiffer.
At the moment I am trying to make a wizzer with integrated voice coil. Here is some pic's.
Any new on your project Hentai.
Some notes:
It was noted that the surrounding of the my unit was to thick, so I removed most of it. There was no audible changes ta all, (I have not access to any measure devices).
I added a aluminium cone to the membrane, this give a higher output at high frequency, more or less logical...... It increases the areal in the centre of the membrane. Buy the way the cone was made from the bottom of a beer can
I have decided not to try to make the unit without a spider.....due to the softness of the edge of the membrane. Instead I will bend the edge abut 90 degrees, to make it mechanical stiffer.
At the moment I am trying to make a wizzer with integrated voice coil. Here is some pic's.
Any new on your project Hentai.
Attachments
Hi Frank,
As test you can have a surround like that (if you are just testing high frequency) for low and mid frequency you need to have some kind of separation from the front side of cone to the back side of cone otherwise you will have shortcircuit.
I like your concept and the pictures, if you can make the whizzers like that from paper i want a pair.
Will update on Ryu soon.
As test you can have a surround like that (if you are just testing high frequency) for low and mid frequency you need to have some kind of separation from the front side of cone to the back side of cone otherwise you will have shortcircuit.
I like your concept and the pictures, if you can make the whizzers like that from paper i want a pair.
Will update on Ryu soon.