I looked at that "econowave" thing, and it doesn't look like an OS waveguide, to be honest. Nor does it use Geddes' foam coating to reduce reflections.
-
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
Dagogo interview of Earl Geddes
- Thread starter Ilkless
- Start date
It's not a coating, it's a solid foam plug, (I have one on mine) and the econowave is a QSC 1 inch horn (or one of the 3 or 4 replicas available) that, like the SEOS is extremely close to the OSWG profile, but just different enough to get away without patent infringement.
Earl published the Oblate Spheroid without patenting it. I use a wooden Oblate Spheroid waveguide in one of my models, though without his patented open-cell foam plug.
I also use SEOS waveguides and have used the Pyle/JBL waveguide which Zilch used in the original Econowave.
Interestingly, I heard that the OSWG doesn't scale to larger size/lower cut off as it looses pattern control up high if you extend the low end. I don't know if anyone can confirm this.
I am looking to make a CD horn to cover 500hz-20khz, for a 1.5 inch compression driver.
The horn needs to be conical though, and would ideally have a roundover on the mouth.
I have yet to find anything that would meet the criteria that I can purchase.
- Joined
- Mar 3, 2018
- Messages
- 48
- Likes
- 148
This thread deserves pics...
Best,
Anand
Best,
Anand
OP
- Thread Starter
- #26
Hi Anand,
Amazing speakers. I first saw your modded NA12s on Audiocircle. Do you know if Earl is still making speakers, or who he has handed production over to? Earl's website says he's still making the NS15 on "special request" after his retirement and someone else is gearing up to take over, but I haven't seen any updates in years.
- Joined
- Mar 3, 2018
- Messages
- 48
- Likes
- 148
Ilkless,
Honestly I know as much as you do. Earl does respond to my emails and he does participate on diyaudio from time to time.
Best,
Anand.
Honestly I know as much as you do. Earl does respond to my emails and he does participate on diyaudio from time to time.
Best,
Anand.
I am not aware of an oblate spheroid "losing pattern control up high" as you increase its size to extend the low end. There may however be a mild bandpass filter effect which reduces the top end energy a bit.
At some point the compression driver will beam enough on its own that the waveguide is no longer controlling the pattern. Imo what frequency this starts to happen depends on the specifics of the compression driver and waveguide.
Earl's data shows his largest 1" throat waveguide still has pattern control at 20 kHz. The challenge is the bandwidth of the compression driver. The B&C DE500 compression driver needs a bit of lift in the top half-octave or so to "keep up" with the 15" woofer he uses. Comparing the top ends of the NS15 with the New Abbey 12 (which uses the same compression driver), the larger waveguide of the NS15 seems to have a little bit less top end.
It's not that Oblate Spheroid waveguides result in less top-end energy; rather, it's that the energy is spread thinner because of the wide coverage angle at high frequencies. Most horns exhibit pattern narrowing in the top octave, so the on-axis SPL is correspondingly higher in the top end. The horn on the JBL M2 has a very wide pattern (for a large-format horn) all the way up, so its top-end energy is spread over a very wide area resulting in reduced sound pressure level within the pattern. This may have played a role in the arguably fairly modest 92 dB system efficiency.
About eighteen years ago Earl made me a one-off 2" throat Oblate Spheroid waveguide for a TAD TD-4001 compression driver. It DID beam badly in the top octave or so, but I'm pretty sure this was a function of the long, narrow-angle throat inside of the oldschool-format TD-4001, which was long enough to constrain the radiation pattern into a narrow angle at short wavelengths. I do not think a modern short-throat large-format compression driver would have the same issue to the same extent, but it would probably still start beaming at a lower frequency than a comparable 1-inch-throat compression driver.
I plan to experiment with a couple of 1.4" throat Oblate Spheroid waveguides later this year, but nothing large enough for pattern control all the way down to 500 Hz.
Duke
Last edited:
Man, they look nice! No wonder you don't want to send them to me.
Fascinating. I didn't ever see what the GedLee Metric was. Does anybody know of have a reference to it?
They are on his website: http://www.gedlee.com/Papers/papers.aspx
Virtins MI has it as a built-in feature.
Vuki
Senior Member
@Poseidons Voice - wonderfull!!!
A lot of good things to read there. Is there one in particular that will discuss the "GedLee Metric"?
Two in particular.
Auditory Perception of Nonlinear Distortion - Theory, and
Auditory Perception of Nonlinear Distortion
I read the paper "Auditory Perception of Nonlinear Distortion" and I can see some potential flaws. Does anyone know of further discussion of the GedLee metric, examples of files or FR plots that further explain/demonstrate it?
Personally, I have done some research on product acceptance where multiple variables were required to predict preference/acceptance, however, any one of them did not have clear explanatory value on their own. Let me give a simple example. In food products, overall taste acceptance is required but not predictive (lots of good-tasting products fail; products with very high scores are not more successful than moderately high-scoring products). Uniqueness can be for both good and bad reasons (e.g. no one wants highly unique fish-flavored breakfast cereal). But a product with both high uniqueness and acceptance above a threshold has a good chance of success. However, neither of those measures on their own would have a correlation to success.
I can imagine a hypothesis involving FR, distortion, and directivity (to pick just three candidates for independent variables) where the explanatory algorithm required some combination of those three that was not simply linear.
Personally, I have done some research on product acceptance where multiple variables were required to predict preference/acceptance, however, any one of them did not have clear explanatory value on their own. Let me give a simple example. In food products, overall taste acceptance is required but not predictive (lots of good-tasting products fail; products with very high scores are not more successful than moderately high-scoring products). Uniqueness can be for both good and bad reasons (e.g. no one wants highly unique fish-flavored breakfast cereal). But a product with both high uniqueness and acceptance above a threshold has a good chance of success. However, neither of those measures on their own would have a correlation to success.
I can imagine a hypothesis involving FR, distortion, and directivity (to pick just three candidates for independent variables) where the explanatory algorithm required some combination of those three that was not simply linear.
You might try diyaudio.com. Earl participates there. Here's a thread on the subject from a few years back:
https://www.diyaudio.com/forums/software-tools/287291-gedlee-metric-demystified.html
I tried to go through it. Unfortunately, I still haven't found a description in words of what the GedLee metric captures and why that's related to preference or even accuracy.
Here's an article Keith Howard wrote, it's over my head but probably not over yours:
http://www.gedlee.com/Papers/THD_.pdf
http://www.gedlee.com/Papers/THD_.pdf
