Again, I think we should go back to the basics as to what kind of driver is used in a WG/Horn. Basically, Air Motion Transformers always seemed to have a wave guide of some sort. So it's nothing new, and the technology of doing that kind of dipole/bipole with an AMT really is not relying on the wave guide to maintain a response without 6db roll off, but rather relying on the different power response in an AMT. If you changed that to a flat rectangular moving coil driver, the response would fall with a 6db roll off.
Now, the tradeoff with an AMT is that it has some characteristic similar to a modal vibrating driver. This is going to create coloration in the WG. Whether one like the sound or not is going to be subjective.
Now, the tradeoff with an AMT is that it has some characteristic similar to a modal vibrating driver. This is going to create coloration in the WG. Whether one like the sound or not is going to be subjective.
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As for the first sentence you are definitely wrong – as for the rest IMO too.
Besides, the B&G NEO 3 the measurements were taken with, is a magnetostat not an AMT.
Even *if* you were right - the beauty of having CD and no 6dB slope to equalise remains – or do you think its only of value if I'd issue by a bunch of patents?
Besides that, it was stated several times that it simply cant be that way – kinda "proven by simple physics" – well, as said and measured this does not hold.
Just another "Waterloo" for Earl I'm afraid...
Again as for the first sentence you are definitely wrong – as for the rest IMO too.
Michael
I agree in almost all respects – though not about discarding my contour as not to be CD.
As said – CD isn't sharp spec'ed for the simple reason that *if*, no single horn on world would be CD - as easily can be seen at the EV ST350 tweeter I've referenced.
So all comes down to "a little bit more CD" or "a little bit less CD" and within *that* my contour definitely falls into the term CD.
As said - I don't care if it's in the "a little bit less CD" corner within the CD family, simply as even higher in my list was to keep sound field as intact as possible – and being after CD behaviour as good as it gets.
What immediately distinguishes the polars of a CD horn and a direct radiator is that no direct radiator ever will split polar SPL low in its bandwidth and then keep roughly the same SPL difference up to where directivity control gets lost.
This behaviour you clearly can see in my measurements and also that – for the off axis angles shown – parallelism is as perfect as any ones else.
Sure at increasing off-axis angles parallelism gets lost more and more – but hey – that's true for any other so called CD-design out there as well.
Its definitely not a secret that the Gaussian MinPhase contour has its strength around axis and its weakness (only in terms of directivity control – mind you) past 30-40 deg – anyone can dig up the directivity sonogramms I've shown some pages back.
Bottom line :
" ... appears to have pretty good CD behavior between ..." is enough !
To argue about "better" CD is lost time IMO as I really was not after a simple "one spec optimisation"!
Michael
Half and half, Markus.
I answered at the http://www.diyaudio.com/forums/multi-way/159731-beautiful-swingin-speaker.html#post2093536 thread as I think the details of my contour might not be of interest here whereas the discussion about CD or not CD seems not to bee too far off topic around here.
Michael
I was going to start a new thread to ask this question, but I think this may be the best place to post it?, as it does have a waveguide hf horn? What would you guys think of the potential of this driver ? http://www.greatplainsaudio.com/downloads/212_8A.pdf
Thanks Dave
Thanks Dave
You are getting to sound more like Earl in your choice of words.As for the first sentence you are definitely wrong – as for the rest IMO too.
Besides, the B&G NEO 3 the measurements were taken with, is a magnetostat not an AMT.
Even *if* you were right - the beauty of having CD and no 6dB slope to equalise remains – or do you think its only of value if I'd issue by a bunch of patents?
Besides that, it was stated several times that it simply cant be that way – kinda "proven by simple physics" – well, as said and measured this does not hold.
Just another "Waterloo" for Earl I'm afraid...
Again as for the first sentence you are definitely wrong – as for the rest IMO too.
Michael
From what the description of the B&G NEO 3 shows, it's probably a very thin flexible diaphragm with conductive traces on the film. The impedance characteristics should be very flat, and T/S parameters would not be measureable most of the time. This type of driver has a limited dynamic range due to the little volume displacment restricted by film tension. They are greate tweeters if you don't get too close of the lower end of the spectrum, otherwise, they will ring quite miserably with large percussion instrument sound (like a heavily played pian) in that frequency range. I have used drivers like this for super tweeters. The power response curve is very different from a moving coil driver, not quite as AMT either.
The B&G NEO 3 also vibrates like a modal type of driver, and the vents are an array of sources. The response will vary with angle due to the interaction between vents like a speaker array does. The WG helps reduce this effect though.
Be aware that most drivers covered under the guide/horn are moving coil drivers, and that is what they assume when referring to the 6db dropping slope.
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Here is an example to demonstrate that acoustic loading of a horn/guide could vary significantly.
An externally hosted image should be here but it was not working when we last tested it.
It seems funny; since Earl addressed the importance of Contant Directivity (he hated the term Controlled Directivity I proposed), everyone is trying to fit thier design into the term. Good work Earl.
It's because the phrase is ambiguous. Even each word involves ambiguity, and in combination even greater ambiguity.
Directivity Index and Directivity Factor: These are phrases that have a commonly accepted meaning, and specifically a "technical meaning".
Constant Beamwidth (acoustically) is however another phrase that lacks acceptance, though ironically is often considered synonymous with Constant Directivity, yet is more succinct. Constant Coverage is generally considered even less succinct than Constant Directivity.
When Michael used the phrase "technical meaning" (a.k.a. a "term of art"), the simple fact is that there is no "technical meaning" for the phrase. *Technical* implies specialized knowledge or field of study *that is commonly accepted among those specializing in that field*, (..or rather something that is not "lay"). This isn't to say that an ambiguous phrase might not be used by someone in the field and deemed as a term of art, but rather until many others accept the meaning for the phrase - it must be defined each time the phrase is used.
..and again, if anyone has claim to what is and is not Constant Directivity - it's ElectroVoice. They "coined it" and registered it as a trademark.
..in other words this is something of a pointless tangent. If there is disagreement with respect to communication, just ask for a definition of the phrase that is causing problems. You certainly don't have to accept that definition as your own, even if it is commonly accepted. Just accept the definition as an aid to communication. Arguing about what it "is" and "isn't" correct word usage really isn't productive to the original discussion.
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Interesting Scott, because trademarks can't protect phrases that are meaningful. You can't use a trademark to prevent people from describing a meaningful attribute. And "constant" and "directivity" clearly have physical meanings, even if they are not precisely defined. You can trademark Kleenex, you can't trademark "facial tissues". If they did manage to get a trademark on that, I doubt if it could be defended, except to prevent someone else from using it as a trademark.
Sheldon
edit: from Wikipedia: Trademark is subject to various defenses and limitations. In the United States, the fair use defense protects uses that would be otherwise protected by the First Amendment.[6] Fair use may be asserted on two grounds, either that the alleged infringer is using the mark to describe accurately an aspect of its products, or that the alleged infringer is using the mark to identify the mark owner. One of the most visible proofs that trademarks provide a limited right in the U.S. comes from the comparative advertising that is seen throughout U.S. media.[7]
An example of the first type is that although Maytag owns the trademark "Whisper Quiet", makers of other products may describe their goods as being "whisper quiet" so long as these competitors are not using the phrase as a trademark.
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Well having a Trademark and defending one are 2 different things. (..Beyond Fair Use you also have the question of if it's use has become "generic". You could argue either in this instance, but you could equally argue in favor of the trademark holder.)
Note that "facial tissues" is considerably more specific than "Constant Directivity".
Predicate "facial": concerning the face - modifying "tissue": thin fabric or paper. A thin piece of paper for use with a face.
Predicate "Constant": unchanging - modifying acoustic "directivity": a radiation pattern from a source indicating how much of the total energy from the source is radiating in a particular direction.
What's unchanging? How is the pattern referenced? etc..
In fact these ambiguities probably are the reason why the trademark could be established in the first place.
Note that "Time Aligned" (for Loudspeakers) is also a trademark, and is also ambiguous.
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You are getting to sound more like Earl in your choice of words.
.
I better should keep an eye on that – thanks !
Sure – its nothing else like a mini ESL driven by a flat coil
This I don't think is the case –the flat coil acts the same way as in a standard coil – otherwise we possibly would see a huuuuuge peak in the FR
So – no peak in FR – no ringing IMO
Have measurements to show its otherwise?
Yes that might be so to some extent – just like an ESL – but I'd rather subsum it under break-up – so I do not see why it should perform any other than a standard diaphragm *expecially* on a horn.
As for AMT which definitely is excellent regarding breakup due to the small physical size involved for each pleat– comparing the two on horns, I didn't find them sound much different.
Well besides - beyond which one would expect for drivers 10 times the price difference of course – meaning both have great resolution and airyness the AMT in addition to that a breathtaking invisibility.
This would indicate that this 6dB slope is introduced by the impedance rise of a conventional compression driver – which I find is not the case. Or what are you referring to?
Simply put – it any driver has a decent flat FR without horn why should a horn in front change that any different for planars versus compression drivers ?
BTW all of above may not be the best to discuss exactly here....
Michael
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It seems funny; since Earl addressed the importance of Contant Directivity (he hated the term Controlled Directivity I proposed), everyone is trying to fit thier design into the term. Good work Earl.
Not necessarily - but I easily admit that its been to a great extent Earls influence to think about the importance of constant directivity and when John lifted some veils I had regarding MinPhase - well - I was lost
Michael
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ScottG, Sheldon - you bring up that we seem to lose words and terms to express ourself with all that "protection" ** - at least this is my feeling...
Should be more often mentioned IMO
On the other hand I find CD (as terminus technicus) pretty clear *in combination* - because if you keep something "constant" - whatever it might be - is telling you that it does not change - and thats also the culprit as obviously no real world item would ever fit the term CD (as terminus technicus) *perfectly* ...
Michael
Should be more often mentioned IMO
On the other hand I find CD (as terminus technicus) pretty clear *in combination* - because if you keep something "constant" - whatever it might be - is telling you that it does not change - and thats also the culprit as obviously no real world item would ever fit the term CD (as terminus technicus) *perfectly* ...
Michael
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The issue is not the coil, but the mass distribution vs force distribution. You don't need my data since you can measure your own. You can also increase the test signal and see what happens. One driver I used was the Beston RT003C. Manger driver also has this characteristic. Basically, you cannot extract T/S parameters with these kinds of drivers.
Jack
One should never measure a 12" waveguide at 1 meter. You need to be much further back than that.
The level of expertise is quite different, so its not quite the same thing.You are getting to sound more like Earl in your choice of words.
George, I not only never said that, but the opposite is true. (Half of what I am claimed to say and believe here is simply not the case.) I prefer the term "Controlled Directivity", but as stated here often, none of these terms are solidly defined.
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