Thanks kindhornman and snup. If flexing is criteria these Goodmans Axiette have good cone geometry. In the center the cone is almost parallel to movement which would damp and resist flexing. Would be interesting to listen these.
It appears so, that would be effective in increasing transverse rigidity without adding mass.
The cone can bend for itself, so the displacement wave radiates outwards within it. Where there is a boundary with another component such as the rim suspension, there is a change of mechanical impedance and so the wave is (partly) reflected and the reflected wave propagates 'inwards' toward the voice coil until there is another impedance mismatch at (say) the spider and another reflection begins. So the displacement wave rings around the cone, being refected at impedance boundaries and aborbed by losses.
In the B&W page, one driver appeared to show a round trip was c 0.6mS, or a 1/2 wave frequency of c 1700Hz. Presumably that would be a resonance, and perhaps the transition frequency for onset of breakup.
I was trying to avoid the term 'transmission line', because it seems to rain poo whenever it crops up. But it is exactly that, and if the rise time of the driving waveform is much longer than the propagation round trip, one can safely ignore wave behaviour. In this case it seems to depend on the driver and the crossover, and is a far closer affair than (say) TL effects in audio cables. Impulses don't crop up in real programme material, but do serve to illustrate the behaviour of the driver.
I think wave/bending behaviour is probably an audible factor for the octave or two below breakup frequency. Below that, the cone can probably be safely considered to move as a single body. Just my 2p worth.
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The problem is not the same at all. Distortion from horn in PA come for two reasons: Poor conception and distortions due to high pressure non linearity of air.
I believe your enclosures suffer from the first point. Cheap driver end cheap horn, too little to match the diameter of the boomer. But if you can accept the sound of your valve amp with-it, the improvement is may-be due to the little damping factor of those kind of amps. Why don't you try to add a little resistance in serial with the horns ?
[Edit] I can see Steven made yet the same answer in between ;-)
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Richard, you have shown a bunch of phase noise graphs but I'm pretty sure
these are not the same fundamental frequency oscillators. A fair comparison
the fundamental freq must be same.
As freq goes up, phase noise gets worse. You can't compare a 5 to 10MHz
OCXO to say a 45MHz one.
There are some slight exceptions to this rule and the Crystek 957 is such
where the 45/49MHz XO's are slightly better than the 22/24MHz ones.
Terry
I posted that B&W page just because I though some visualizations might help, I think the different opinions are interesting.
Wonderful demonstration of how complex this can get, yes different boundary conditions but same mechanical principles.
https://www.youtube.com/watch?v=GtiSCBXbHAg
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Hehe, we used-it to help-us to find the best places to put internal reinforcements in our enclosures (back to 1970 ;-).
What about this:
Wild Burro Audio Labs - Fullrange Speakers - The Betsy & Betsy-K Drivers
It looks like there breakups starting at 4k. Do you think they are the whizzer or the cone?
Wild Burro Audio Labs - Fullrange Speakers - The Betsy & Betsy-K Drivers
It looks like there breakups starting at 4k. Do you think they are the whizzer or the cone?
Do they really try to explain or to impress through confusion?
A healthy dose of theory as a remedy (very useful for positive experimentation)
http://publications.lib.chalmers.se/records/fulltext/154618.pdf
The predecessors on bending wave mode exploration on loudspeakers:
A. Hegeman
Loudspeaker
L. Walsh
COHERENT-SOUND LOUDSPEAKER
Notice the early adoption of controlled impedance sectioning, slits, ribs on diaphragms:
Phonic diaphragm
Acoustic device
Acoustic diaphragm
Thanks! Helping one the other here.
Would you like some more Retsina ?
George
George,
You are the virtual guru of information here, I don't know how you have all of this information so easily at hand but it is greatly appreciated.
I think the bottom line is that the dynamic driver is still the best option we have in the majority of cases, whether in a box or mounted to a horn/waveguide.
I guess that we can place an electrostatic speaker in the DML catagory as that would seem to describe the function as close as I can understand to the mode the diaphragm is functioning under, barring the much greater distribution of the driving forces.
As that U-Tube video that Scott just posted shows a non terminated membrane with a single central driving force will never and could never have some of the properties that some manufacturers want to attribute to a flat membrane hanging in space.
If the NXT is supposed to be one of the best DML types speakers I haven't heard much to recommend that flat membrane technology. Having personally helped with the development of one of these DML type of speakers, though rather small to sit on a desk, I can say I personally would never go down that road. As Scott pointed out, though they are not taking up much space in depth, they do require a large area in the horizontal plane, so where is the advantage?
The speaker I am currently developing was premised originally on trying to stay within a very narrow horizontal space. As I developed it I just couldn't help but increase the width, I couldn't help myself but did limit the maximum width to 6" at the widest point of the enclosure. This of course says that I have compromised some edge diffraction but every speaker has some critical compromises, I know of no speaker that can achieve perfection in every aspect, physical reality makes us choose our poisons.
You are the virtual guru of information here, I don't know how you have all of this information so easily at hand but it is greatly appreciated.
I think the bottom line is that the dynamic driver is still the best option we have in the majority of cases, whether in a box or mounted to a horn/waveguide.
I guess that we can place an electrostatic speaker in the DML catagory as that would seem to describe the function as close as I can understand to the mode the diaphragm is functioning under, barring the much greater distribution of the driving forces.
As that U-Tube video that Scott just posted shows a non terminated membrane with a single central driving force will never and could never have some of the properties that some manufacturers want to attribute to a flat membrane hanging in space.
If the NXT is supposed to be one of the best DML types speakers I haven't heard much to recommend that flat membrane technology. Having personally helped with the development of one of these DML type of speakers, though rather small to sit on a desk, I can say I personally would never go down that road. As Scott pointed out, though they are not taking up much space in depth, they do require a large area in the horizontal plane, so where is the advantage?
The speaker I am currently developing was premised originally on trying to stay within a very narrow horizontal space. As I developed it I just couldn't help but increase the width, I couldn't help myself but did limit the maximum width to 6" at the widest point of the enclosure. This of course says that I have compromised some edge diffraction but every speaker has some critical compromises, I know of no speaker that can achieve perfection in every aspect, physical reality makes us choose our poisons.
One bending wave driver I am familiar with is the Dicks driver. It's an interesting concept, using a cone in all modes in different frequency bands.
From the literature:
'The lower frequency end of its operating range can be described with Small/Thiele resonant parameters; in the next frequency band up to the Coincidence Frequency, it works like a pistonic driver; next an overlapping band follows where pistonic movement is progressively replaced by bending waves until all radiation is generated purely by bending movement in the cone - due to dispersion and the cone’s special shape, the Coincidence Frequency is spread over an extended frequency range, rather than occurring at a single frequency like the Dipole Frequency; the last mode of operation commences above the bending wave band at the Dipole Frequency when the first standing wave occurs and where modal break-up begins.'
Mr. Dicks has had an interesting career which I may or may not divulge; but I believe his driver has some interesting ideas behind it.
What I heard sounded well but I don't know how it would measure. Being an omni driver makes it hard to judge, imho.
Jan
From the literature:
'The lower frequency end of its operating range can be described with Small/Thiele resonant parameters; in the next frequency band up to the Coincidence Frequency, it works like a pistonic driver; next an overlapping band follows where pistonic movement is progressively replaced by bending waves until all radiation is generated purely by bending movement in the cone - due to dispersion and the cone’s special shape, the Coincidence Frequency is spread over an extended frequency range, rather than occurring at a single frequency like the Dipole Frequency; the last mode of operation commences above the bending wave band at the Dipole Frequency when the first standing wave occurs and where modal break-up begins.'
Mr. Dicks has had an interesting career which I may or may not divulge; but I believe his driver has some interesting ideas behind it.
What I heard sounded well but I don't know how it would measure. Being an omni driver makes it hard to judge, imho.
Jan
In the first edition of the AES Loudspeaker Compendium there is a nice paper on decoupled cone concepts. The accordion pleats used to decouple the center of the cone from the outer portion of the cone to increase the FR bandwidth of the device. While on a theoretical basis this is true and can be demonstrated it comes at the cost of other problems. The reference to the Goodman's speaker shows this taken to an extreme with multiple pleats and decoupled regions. History seems to show this wasn't the best direction to go with a dynamic driver.
Unbeknown to any here I have been helping one of the members on this site to develop a version of the MBL speaker. I have been helping behind the scenes to develop that technology using some tweaks and changes that I hope will help him to have a successful product. I have some materials here to make him some patterns for his molds so we can tests some ideas, it is an interesting mental project for me though I started out just trying to mentor him in some basic concepts. He is very young and I encourage him as he really seems to have a passion for speakers. I myself am not a real big fan of omnidirectional speakers but it has been interesting and it looks like we will apply for some joint patents on these new ideas.
No efkharisto, George.
I have fond memories of drinking Ouzo:
* Scaling the walls of the Acropolis at night.
* Drinking with two beautiful French ladies in Athens.
* Seeing a photo of the all the world's tyrants/dictators
in one composite B&W photo...I never could get a print of it.
* Hearing some band play "Sultan's of Swing" in small club in
Athens and thinking it was the best I'd ever heard. Then my friend
telling me it should be, because it is Dire Straights. As we know them
here in the States, but in Europe they were Sultan's of Swing.
* Being stranded in Athen's with no money after the Ferry
to Brendisi almost capsized, was canceled due to storms in the Adriatic.
Then, being taken care of for a couple of weeks by an Australian gal.
Playing piano for the director of a small music school by the bus station.
Yes, George More Ouzo Parakalo.
George,
If you could find a copy of that picture I would really be impressed.
It was being distributed by the communist party back in 1979-1980.
There were about 20 people in it, Marx, Stalin, Mau, Lennin,
Hitler, Franco, Castro, Musilini, and others. It looked like
they were all posing for a photograph together.
Cheers,
If you could find a copy of that picture I would really be impressed.
It was being distributed by the communist party back in 1979-1980.
There were about 20 people in it, Marx, Stalin, Mau, Lennin,
Hitler, Franco, Castro, Musilini, and others. It looked like
they were all posing for a photograph together.
Cheers,
Steven, I enjoy reading so I read a lot.
When an interesting question arises, my peculiarly-operating memory gives me a coded signal to use a certain ‘retained snapshot’ from a part of a document that has a relevant answer and I should start searching. It is a strong compulsory feeling.
It is this way that I am searching in my books, my hard drivers folders or in the web sea.
It would be a relative efficient method but it ends taking up a lot of my time because during the search process, I read many new to me documents.
On the other hand, this is the way the circle of memory enrichment and technical ideas comparison remains alive.
Mentoring gives back a rewarding feeling
Oh, oh! It could have been really worse
Easy with this deceptive sweet taste ( a real Trojan horse)
George
That is a wonderful gift George, to be able to keep all of that information sorted in your brain and recall the relevant information. Sometimes my daughter will ask me about a movie she says we saw together and I don't even remember seeing it until some prompting! I never was one to read much fiction when I was younger, I was to busy reading technical information and trying to learn. It wasn't until maybe 10 years ago that I actually took the time to read many of the classics, I have Moby Dick on my desk now to complete. I think I need to spend some time organizing the many bookmarks I have saved to my computer so I to can find the articles that I found interesting or needed to return to to read in more detail. I am looking to go back to the local college and take a course in MasterCam, I have mastered CAD design and now I need to move my machining knowledge from manual machining to advanced CNC machine programming.
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