pdan said:
There is a volume control.
But the fact remains that problems become most evident at higher SPLs. Hence, like the reviewers, I always audition unknown loudspeakers at well above average levels. Then when I know what problems to expect, I lsiten at more reasonable levels. You should try this as it is a good technique to showing up flaws.
tinitus said:Gerdlee, it may have been very unclear, but I very strongly question your position about who is unbiased and who isnt
The fact is that I did not know any of those reviewers prior to their coming to my home. The test is not like one that is completely blind, I agree, but these are not my own words of praise, like so many other DIYers, but those of people who had nothing to gain or loose from expressing their opinions. I asked them to post their impressions but gave them no suggestions of words or opinions to use. Thats why they all differ substantially and yet all say the same thing.
Well, I suppose I owe you an explanation
The guys who made it to your home came with the expectation of hearing something spectacular AND they hoped to buy them ... furthermore your own person, personality and reputation is not insignificant either
Sure, if they werent good they wouldnt have bought them ... but I do think they were biased nontheless ... but no doubt they liked your Summas, and thats good enough
Still, I dont think you can say that anglotaire is biased and your listeners not
The guys who made it to your home came with the expectation of hearing something spectacular AND they hoped to buy them ... furthermore your own person, personality and reputation is not insignificant either
Sure, if they werent good they wouldnt have bought them ... but I do think they were biased nontheless ... but no doubt they liked your Summas, and thats good enough
Still, I dont think you can say that anglotaire is biased and your listeners not
tinitus said:
I said in my response that the only way for the test to have been completely unbiased would have been for it to be blind and for me not to be involved. But that is a bit inconvenient. Hence, the procedure that I used is as unbiased as its going to be reasonably possible to do.
I think its safe to say that ones personal opinion of their own system is of less value than that of several other independent reviewers.
Bias is a matter of degrees. Its not a black and white situation. The brightness of the lights and if its raining or not biases the listeners. Its important to remove as much as is reasonably possible to do and I do that, but as of yet, I can't control the weather.
gedlee said:
It's a shame topics quickly head off track so fast.
If people actually read the above, Earl hadn't yet said coaxial drivers are terrible, he said he prioritizes maintaining a more optimium waveguide first. That's a design priority which he has, not a complete dismissal of coax's.
A more interesting discussion would have probably been about the limitations vs. the potential benefits of a coaxial driver executed with a 3-5" diameter VC...
gedlee said:
The asymmetric waveguide topic was brought up with a good question about height vs. width. An argument can be made for either case of the axial dimensions being proportional to the nominal angle, as well as the for the axial dimensions being inversely proportional to the angle. The choice or preference will of course depend on the original reason why an asymmetric horn is desired for a given use, and then complicated by the requirement to mate to low frequency devices, as well as the limitations of the driver of the horn.
While I wouldn't expect any larger horn to be inexpensive, a proof at a smaller size might not be too expensive, or being a little less stringent on the material integrity to initially form the shape opens many options. Rapid prototyping and direct-digital manufacturing make the execution mostly just a matter of drawing the profile, which shouldn't be hard with any modern 3D parametric CAD program. I'm not suggesting it's pocket change, but it shouldn't have to be many 10s of thousands.
Back to your regularly scheduled, virtual tennis match.
I would like to emphasize that I am not against compression drivers as such, it is just that no one seems to make one that is really suitable to the task.
What I would like is something like the front radiating compression driver intended to produce spherical waves that Celestion described in a AES paper
http://professional.celestion.com/pro/rd/pdfs/AESPAPER.pdf.
Let us not forget that the screw spigot on the typical compression driver is a design that is very old, and is basically a standard fitting that is there for servicing convenience and not acoustic excellence.
If it only slightly mismatches the horn entry in terms of diameter and concentricity, then any fancy horn contour you might have after that counts for naught and from what I have seen in various forums a bad fit is the norm.
An of course there is the basic technical aesthetic that taking a spherical wavefront coercing it into a semblance of a flat one, and then re bending it into a semblance of a spherical one, and then stuffing the gadget with foam to mop up the errors in the spherical /plane/spherical transitions, seems to be a rather round about and over complex way of doing things, the dome tweeter plus conical horn is positively zen like in comparison.
rcw
What I would like is something like the front radiating compression driver intended to produce spherical waves that Celestion described in a AES paper
http://professional.celestion.com/pro/rd/pdfs/AESPAPER.pdf.
Let us not forget that the screw spigot on the typical compression driver is a design that is very old, and is basically a standard fitting that is there for servicing convenience and not acoustic excellence.
If it only slightly mismatches the horn entry in terms of diameter and concentricity, then any fancy horn contour you might have after that counts for naught and from what I have seen in various forums a bad fit is the norm.
An of course there is the basic technical aesthetic that taking a spherical wavefront coercing it into a semblance of a flat one, and then re bending it into a semblance of a spherical one, and then stuffing the gadget with foam to mop up the errors in the spherical /plane/spherical transitions, seems to be a rather round about and over complex way of doing things, the dome tweeter plus conical horn is positively zen like in comparison.
rcw
rcw said:
I'm trying to be reasonable in this discussion but your last paragraph is pretty negative and entirely incorrect.
I don't and wouldn't use a thread-on compression driver.
The diaphram of a compression driver is concave with the apex at about the throat aperature, basically an ideal situation. Thus what you are saying is entirely incorrect. The larger wavefront (low power compression) converges on the aperature and with a little phase adjustment yields an extremely good approximation to a plane wave.
The foam would even improve upon the dome source in a cone. I would suspect it would improve it quite a bit since the dome is a poor fit to the conical section and the wavefront mismatch will generate a great deal of HOMs which the foam will help to attenuate. This device might then be tolerable.
Stop being so negative and condescending and we will get along better.
gedlee said:
Not in the near future, but I try to not rule out possibilities. I have almost a dozen product designs to finish up myself, with another dozen waiting behind that with plenty of my own ideas to get around to...
If I was going to put a lot of effort into waveguides, I'd probably want to come up with a better option than a conventional compression driver, where you yourself note that a source closer to a conical point source would significantly reduce the headaches of the planar-conical transition.
My suggestions about prototyping was more a heads up that if you haven't looked or priced things in a while, things have been quickly changing for the better, and it's rare that a little manual re-inforcement, assembly, or finishing touches can't get plenty close enough to a concept for a proof at very reasonable cost (~= a few of the kits you are starting to sell). In my experience, a tangible proof gets a lot more interest from potential investors or licensees as most won't realy "see" the benefits until at least some crude example can be demonstrated.
I will likely be very near you later this summer/fall visiting two of my customers near you. A meet over coffee or adult beverage might be fun.
Cheers,
Mark Seaton said:
You don't want to come and hear my system!? I would think that would interest you more than coffee. I have coffee too you can do both.
I am more than aware of the options for prototyping, having been an engineer for a couple of years now. The real point is that I see this as being a small incremental improvement at best. And since I make my own tooling, its more the hours than the dollars.
The kit sales pay the mortgage.
a FDM ribbed shell of Summa waveguide size would likely be in the $2K+ ballpark
http://home.att.net/~castleisland/rp_int1.htm
it could be reinforced with epoxy resin concrete on the ribbed backside for rigidity/damping
may need hand sanding - the FDM filament gives a "stepped" contour at 1/6-1/10 of a wavelength @ 20KHz that could give diffraction grating effects?
certainly most significant directivity/HOM/mouth diffraction effects could be measured without special finishing
virtually any geometry you could describe in an appropriate CAD format could be explored – subtle ellipticity or maybe “aperiodic” eccentricity to fill the 20KHz hole? How about integral phase plug? Right/Left speaker asymmetric mouth flare/radius?
http://home.att.net/~castleisland/rp_int1.htm
it could be reinforced with epoxy resin concrete on the ribbed backside for rigidity/damping
may need hand sanding - the FDM filament gives a "stepped" contour at 1/6-1/10 of a wavelength @ 20KHz that could give diffraction grating effects?
certainly most significant directivity/HOM/mouth diffraction effects could be measured without special finishing
virtually any geometry you could describe in an appropriate CAD format could be explored – subtle ellipticity or maybe “aperiodic” eccentricity to fill the 20KHz hole? How about integral phase plug? Right/Left speaker asymmetric mouth flare/radius?
I think unbiased reviews should contain both good points and points where more were wished for. Here is a very openminded way of doing things:gedlee said:
http://www.diyaudio.com/forums/showthread.php?postid=1560034#post1560034