Beyond the Ariel
- Thread starter Lynn Olson
- Start date
It's not hugely dissimilar from something like this (horizontally).
FaitalPRO - Neodymium Professional Drivers
The TAD ET-703 is a very wide dispersion super tweeter.
I suspect that the TAD, while having a very high freq. crossover, is using a first order design - increasing the combined off-axis response above the treble horn's loss in pattern control.
In other words I think it's a high/wide dispersion design with some narrow-band diffraction around 4 kHz (..that likely ripples "upward" in freq.)
Last edited:
'rainbow' like color maps are not very good representing data. Adding many different colors to a graph just makes it a perceptual mess. Taking visual perception in mind, a graph combining saturation and luminance variation could make a simple, very detailed representation of data.
summary on the topic:
Why Should Engineers and Scientists Be Worried About Color?
Last edited:
Hadn't considered the LV Vox Olympian might be using a diffraction horn, but it seems plausible. Kind of nasty diffraction delay time, though ... the HF horn looks like it's maybe 12" or so long, which would give delayed pulses just a little less than 1 mSec apart. Not pretty, but then, no diffraction horn is, at least in the time domain. Not much attention is paid to diffraction on any of the horns, so I imagine there might be some tradeoffs in image quality.
As for the overall subjective goal for this long-running project, it is coming into view. Sonics in the general vicinity of the Altec Model 19, the JBL Everest series, and the 15" Dual-Concentric Tannoys. The crossover is not as complex as the modern JBL's, with their multiple notch filters, but higher efficiency (the JBL is 94 dB/metre). Low diffraction and clean time signatures remain a priority, as it was for the Ariel back in 1993. Rapid settling times are unusual for large-format drivers, so I'm curious how this aspect turns out.
Still strongly considering an Altec/GPA version with Alnico 416's (notch filter retuned for this driver) and Alnico 288's. There is a certain quality to Alnico-magnet drivers with underhung voice coils that I like. I've asked Alexander of RAAL what might be responsible, and he mentions the gaps of the classic Altecs operate quite close to saturation, and this changes the sonics.
My version may well have the resistive-vent cabinet looking like a scaled-up Fonken, or the full-scale Jensen. Gary's real-world results will guide what I do with my version. One thing I like about resistive-vent enclosures is they are relatively insensitive to dynamic Q variations, so the bass has a somewhat different quality than classical T/S closed or vented boxes.
As for the overall subjective goal for this long-running project, it is coming into view. Sonics in the general vicinity of the Altec Model 19, the JBL Everest series, and the 15" Dual-Concentric Tannoys. The crossover is not as complex as the modern JBL's, with their multiple notch filters, but higher efficiency (the JBL is 94 dB/metre). Low diffraction and clean time signatures remain a priority, as it was for the Ariel back in 1993. Rapid settling times are unusual for large-format drivers, so I'm curious how this aspect turns out.
Still strongly considering an Altec/GPA version with Alnico 416's (notch filter retuned for this driver) and Alnico 288's. There is a certain quality to Alnico-magnet drivers with underhung voice coils that I like. I've asked Alexander of RAAL what might be responsible, and he mentions the gaps of the classic Altecs operate quite close to saturation, and this changes the sonics.
My version may well have the resistive-vent cabinet looking like a scaled-up Fonken, or the full-scale Jensen. Gary's real-world results will guide what I do with my version. One thing I like about resistive-vent enclosures is they are relatively insensitive to dynamic Q variations, so the bass has a somewhat different quality than classical T/S closed or vented boxes.
Last edited:
The perceptual research, some of which is referenced in the old IBM paper linked in Daniel's post, is that changing hue does not work well for expressing amplitude variations. A hue change is a good indicator for data that has a clear threshold (for example, indicating sea level in cartographic elevation model data) but otherwise it is better to vary the luminance and saturation. Key is to ensure that the luminance variation for the hue(s) chosen are monotonic as that has been found to give the best results. That is not trivial, but is certainly possible and is used. Blue makes the smallest contribution to luminance, its variation has the lowest perceptibility, so hues made from red and green are better. There has been a lot of research into this for visualisation of medical and seismic data, googling will turn up various papers on it.
Superb paper - thanks: Just what I was looking for.
Thanks Dan!
After settling on the values for the Zobel, I added the low pass filter using calculated values for a 2nd order Bessel at 700 Hz. Of course, the lift from 1.5 kHz to 4 kHz was still there with all its ripples, but the whole thing was rotated clockwise. The next step was to knock down the first big bump with a narrow notch filter. I experimented with various notch tunings, widths and depths. Best results were achieved with a filter centered at 1,720 Hz. IR improved as well.
There was still a problem, though: I wasn't reaching -6 dB until about 900 Hz. Experimentation with added capacitance and inductance eventually resulted in a curve that hit the target rolloff and had the desired shape. The filter was now electrically tuned for -6 dB at 420 Hz! Thank goodness for Arta.
Best of all, the IR and CSD plots looked better than ever. The 2.5 ms wrinkle, while still present, is now a tiny fraction of its former self. I am very pleased with where it ended up. I think it's as good as I'm going to get with a 2nd order filter on a 15" woofer.
Here's the FR curve:
Here's the impulse response:
And here's the CSD:
Finally, here is the crossover schematic:
Gary Dahl
Thanks Gary!!!
Was there any on and off axis response measurements done yet?
Ditto! Most excellent. I hope it's something you can use, Earl.
I did not take long last night fooling around with a dozen or more color gradients to discover pretty much the same things the IBM crew did. Luminance and saturation are key. And most color gradients don't show subtle variation well. The 2 below are the best I could come up with quickly, and you can see they aren't great. Better then JET , tho IMO.
The IBM stuff is superb.
Attachments
Hello Panomaniac,
Your upper colormap is quite similar to the one used for the spectrogram in Adobe Audition (it also inspired from the Hot colormap...).
I doubt the usefulness of your second as our eyes (and our computer screens) are weak inside the green range.
See here attached, a screen shot of a spectrogram from Adobe Audition.
Best regards from Paris, France
Jean-Michel Le Cléac'h
(I am probably more accustomed to Matlab Jet and HSV colormaps and prefer them. I must add that I am not at all bothered by the fact that their luminosity variation isn't linear. I guess that each different application needs its own colormap).
Your upper colormap is quite similar to the one used for the spectrogram in Adobe Audition (it also inspired from the Hot colormap...).
I doubt the usefulness of your second as our eyes (and our computer screens) are weak inside the green range.
See here attached, a screen shot of a spectrogram from Adobe Audition.
Best regards from Paris, France
Jean-Michel Le Cléac'h
(I am probably more accustomed to Matlab Jet and HSV colormaps and prefer them. I must add that I am not at all bothered by the fact that their luminosity variation isn't linear. I guess that each different application needs its own colormap).
Attachments
Last edited:
Hello Panomaniac,
Yes, there is some noise on the spectrogram (purple on black) and the pulse is designed "by hand", in order to show all the colors.
Best regards from Paris,
Jean-Michel Le Cléac'h
Yes, there is some noise on the spectrogram (purple on black) and the pulse is designed "by hand", in order to show all the colors.
Best regards from Paris,
Jean-Michel Le Cléac'h
I'm on page 100 of Bob Cordell's Power Amplifier book. My comments are here. As a former technical writer for Tektronix, I feel it is one of the best technical books I've ever read, even if your interest is limited to loudspeakers or tube amps. Get it, read it thoroughly, and learn a few things about that mysterious black box you've been listening to for all these years.
Last edited:
It's a short list:
Bob Cordell Designing Audio Power Amplifiers
Morgan Jones Valve Amplifiers, Third Edition
Morgan Jones Building Valve Amplifiers
Ben Duncan High Performance Audio Power Amplifiers
Ralph Morrison Grounding and Shielding Techniques
Newell and Holland's Loudspeakers - For Music Recording and Reproduction
Earl Geddes, "Audio Transducers" (order direct from Gedlee)
These are the books on my reference bookshelf, along with old-timers like the RCA Radiotron Designer's Handbook (4th edition), Valley and Wallman "Vacuum Tube Amplifiers", HF Olson's "Acoustical Engineering", every issue of Sound Practices, Vacuum Tube Valley, and Speaker Builder magazines, along with Audio Amateur going back to 1971. Also the AES Journal from 1971 through the early 80's.
Unless you are researching the history of audio, the books in the top list are the ones to get. Yes, they are pricey. If that's an issue, start with Newell and Holland, and then get either Bob Cordell's book (if you're into transistors), or Morgan Jones' book (if you're into vacuum tubes). If you are a beginner, get the Loudspeaker Design Cookbook by Vance Dickason.
Bob Cordell Designing Audio Power Amplifiers
Morgan Jones Valve Amplifiers, Third Edition
Morgan Jones Building Valve Amplifiers
Ben Duncan High Performance Audio Power Amplifiers
Ralph Morrison Grounding and Shielding Techniques
Newell and Holland's Loudspeakers - For Music Recording and Reproduction
Earl Geddes, "Audio Transducers" (order direct from Gedlee)
These are the books on my reference bookshelf, along with old-timers like the RCA Radiotron Designer's Handbook (4th edition), Valley and Wallman "Vacuum Tube Amplifiers", HF Olson's "Acoustical Engineering", every issue of Sound Practices, Vacuum Tube Valley, and Speaker Builder magazines, along with Audio Amateur going back to 1971. Also the AES Journal from 1971 through the early 80's.
Unless you are researching the history of audio, the books in the top list are the ones to get. Yes, they are pricey. If that's an issue, start with Newell and Holland, and then get either Bob Cordell's book (if you're into transistors), or Morgan Jones' book (if you're into vacuum tubes). If you are a beginner, get the Loudspeaker Design Cookbook by Vance Dickason.
Last edited:
How could you leave out Toole's book? Granted Earl's book has some information on psychoacoustics, but Toole's book has tons of valuable information in it. If you don't know how your brain interprets what the speakers produce, then you have little basis for effectively applying information in any of those other books so in my world it's at the top of the list.
Thanks Lynn... I'll start with one or two of the ones you suggested.
This is the first product sheet (for this tweeter) I've seen:
https://www.madisound.com/store/product_info.php?cPath=45_229_236&products_id=8954
https://www.madisound.com/store/product_info.php?cPath=45_229_236&products_id=8954
That's some FR plot. I take it that it was done sans baffle.
Cool!
I just noticed this new compression driver from radian.
http://www.radianaudio.com/components/com_virtuemart/shop_image/prod_files/745NEO.pdf
RAAL has also recently announced a dipole ribbon tweeter. I found this early documentation. Personally, I would minimize the baffle area by separating the ribbon's transformer off of the front mounting plate.
www.solen.ca/pdf/raal/DIPOLE140-15D.pdf
A DIY dipole ribbon tweeter is simple to construct from 0.5" x 0.5" NdFeB N50 magnets and some 0.5" square 1018 steel. I build 4" long x 0.7" wide dipole ribbons which can easily be crossed at 1,500Hz, and mount it on top of no-baffle Lambda TD15D or Tang Band W8-1808 mids. Material cost ~ $50. A no-baffle dipole ribbon tweeter has modest area required for good dispersion.
I wonder if a Fish Speaker would sell well in the Pacific North West.
www.solen.ca/pdf/raal/DIPOLE140-15D.pdf
A DIY dipole ribbon tweeter is simple to construct from 0.5" x 0.5" NdFeB N50 magnets and some 0.5" square 1018 steel. I build 4" long x 0.7" wide dipole ribbons which can easily be crossed at 1,500Hz, and mount it on top of no-baffle Lambda TD15D or Tang Band W8-1808 mids. Material cost ~ $50. A no-baffle dipole ribbon tweeter has modest area required for good dispersion.
I wonder if a Fish Speaker would sell well in the Pacific North West.
