Thanks for the PAF decipher.
I noticed that the Fryer paper you mentioned is reference [11] in the Keele paper on wavelet analysis.
AES E-Library >> Time-Frequency Display of Electroacoustic Data Using Cycle-Octave Wavelet Transforms
http://www.xlrtechs.com/dbkeele.com...ES Preprint) - Time-Freq Display Wavelets.pdf
The AES paper/presentation (with link for free download) under the CLIO section below is perhaps the gentlest introduction to wavelet analysis.
Two other important AES papers on the topic are:
AES E-Library >> Decomposition of Impulse Responses Using Complex Wavelets
AES E-Library >> A Spectrogram Display for Loudspeaker Transient Response
Also…
(PDF) Wavelets and signal processing
Popular measurement systems with this capability
ARTA:
http://www.artalabs.hr/download.htm
Good summary and mathematical description of different time-frequency analysis methods can be found in sections 6.4 & 6.5 of manual.
www.artalabs.hr/download/ARTA-user-manual.pdf
CLIO:
http://www.audiomatica.com/wp/
Free download of AES paper and presentation on wavelet use can be found on their knowledge base page
http://www.audiomatica.com/wp/?page_id=350
www.audiomatica.com/wp/wp-content/uploads/audaesny2007.pdf
www.audiomatica.com/wp/wp-content/uploads/ALMA_2011.pdf
REW:
https://www.roomeqwizard.com/
Summary of time-frequency analysis capability can be found in manual or online help file
https://www.roomeqwizard.com/help/help_en-GB/html/graph_spectrogram.html#top
I’ve also seen some postings here on diyAudio using APLs TDA software, but have not personally used it.
http://aplaudio.com/conc2/products/tda/
http://aplaudio.com/downloads/Introduction-to-TDA.pdf
Be sure to see that (free) reprint just for the beautiful illustrations*.
B.
*sadly, that's the only aspect I could profit from. But the link to Bolserst's REW manual is quite informative for me
Thanks for you great reply about the advantages of full range ESL's.
Regarding the high frequency resonances of ESL panels, your model is superb. I'm very inexperienced. Can I ask how you would suggest managing the high frequency resonances of panels without dust covers eg the Martin Logan panels as measured in Stereophile? Are wire stators better? I think the only ESL panel Stereophile measured without high frequency hash was just one Sanders panel. It seem almost universal to have membrane resonance over 10kHz in commercial ESL's? Thanks.
Hi
I should have been more specific - we can model the acoustic resonances quite well - mechanical resonances are a different problem.
To minimise acoustic resonances there are some obvious things that come straight out of the models - no dust covers or grills, small membrane-stator distance, high open area stators, thin stators, small holes rather than slots. Of course not all of this is practical - compromise is always necessary. Yes wire stators are better than slotted stators of the same thickness because of the round edges on the holes between the wires.
Mechanical resonances come about from Newton's 3rd law - for every action there is an equal and opposite reaction. When the electrostatic motor pushes the membrane forward, say - it does so by pushing back against the stators - so membrane moves forward - stators move back. The stator movement is small, but it can excite mechanical resonances - in which case the stator motion persists for some time afterwards.
I've not thought about this stuff very hard, but it seems the trick is probably to find someway of including damping material to soak up the stator and frame movement. If the resonances are at high frequencies, making the thing stiffer does not help. My guess is that laminated or layered materials, e.g PCBs, wire stators with insulation on the outside, are better than perforated metal - mounting the stators on viscous material should help too.
Thanks for your interesting anti-resonance ideas.
I was thinking about how common the high-freq resonances are in ESL panel measurements and if that implies it isn't a problem after all. I wonder if resonances over 10kHz are audible? Its hard to hear anything meaningful over 10kHz but I imagine high frequency resonances could create IHD in the mid-range?
Hi,
to avoid reflections back from the fixed membrane rim You either need damping or a non stretched membrane ... or a combination of both.
I know from a quite old patent that described a method to do away with the stretching, but the method introduces too much damping at the same .... at least with the materials I had at hand.
It showed though that the method could work and -at least in theory- should improve the ESL behaviour in other aspects also.
jauu
Calvin
to avoid reflections back from the fixed membrane rim You either need damping or a non stretched membrane ... or a combination of both.
I know from a quite old patent that described a method to do away with the stretching, but the method introduces too much damping at the same .... at least with the materials I had at hand.
It showed though that the method could work and -at least in theory- should improve the ESL behaviour in other aspects also.
jauu
Calvin
Thanks Calvin. Thats very interesting.
Am I right in thinking your considering high frequency resonances from a different model to Golfnut, as being boundary membrane reflections rather then air wave back reflections?
Like this fun visualiser?
Rectangular Membrane Applet
Attachments
Hi,
I´d assume similar to how a Manger driver, a anechoic room or a RF-chamber is built.
They all feature rather large damping elements of mostly conical or pyramidal shape.
Unfortunately all these measurements are either large or not as effective as wanted.
I wonder if it is a real, a audible problem in first case.
jauu
Calvin
I´d assume similar to how a Manger driver, a anechoic room or a RF-chamber is built.
They all feature rather large damping elements of mostly conical or pyramidal shape.
Unfortunately all these measurements are either large or not as effective as wanted.
I wonder if it is a real, a audible problem in first case.
jauu
Calvin
I did experiment with eliminating boundary reflections (to a large degree, not completely). Doesnt affect detail reproduction IMHO. It seems that human hearing can still pick out the details even with spurious resonances added. Though it sounded more relaxing, like instuments on a more black background. No measurements , just my subjective experience.
Thats fascinating. I'm curious how you managed to damp the membrane boundary reflections?
What's your real life experience with NO DUST COVERS?
I've heard one pair of ESL63s with no dustcovers and they did have less of the mid/HF delayed resonance that is their main audible fault.
But Peter Walker said they would need cleaning or even new diaphragms after a month .. sometimes after a week.
On the dust cover note
I picked up a pair of old 1980 Soundlab R-1,s in real bad dirty shape.
Pulling the wood latice/black grill cloth off, the wire stators and mylar were perfectly clean and absolutely no dust could been seen on any of the segmented strip segments. They looked like new !
Maybe this dust cover on the Quads could be illuminated or maybe its overstated too much as a worry. I get it that it affects 20k response a little
A simple stretched fabric might be enough if its tight enough and at the same time can pass 20k without attenuation
Is pcb construction vs wire that much more dust attractive ?
I picked up a pair of old 1980 Soundlab R-1,s in real bad dirty shape.
Pulling the wood latice/black grill cloth off, the wire stators and mylar were perfectly clean and absolutely no dust could been seen on any of the segmented strip segments. They looked like new !
Maybe this dust cover on the Quads could be illuminated or maybe its overstated too much as a worry. I get it that it affects 20k response a little
A simple stretched fabric might be enough if its tight enough and at the same time can pass 20k without attenuation
Is pcb construction vs wire that much more dust attractive ?
hmm funny they used hot glue and a very dull cutter for the frame
never knew anyone would use hotlgue. i think it might work rather well to keep wires in place. i did it once years ago. but thought .,... it was to much scapbook style. but aparantly it holds well.
This was their first commecial offering I believe and well, effcient manufacturing has a learning curve for any company.
Looking at all the wood pieces, its easy to see this wasn’t the easiest way and they probably lost money on this model
Their next model did away with all the wood lattice pieces for good reason.
Regards
David
Looking at all the wood pieces, its easy to see this wasn’t the easiest way and they probably lost money on this model
Their next model did away with all the wood lattice pieces for good reason.
Regards
David
Do you use these speakers daily ?
I'm really after real life experience with ESLs without dustcovers.
On ESL 63, the dustcovers seriously affect response & delayed resonances above 5kHz.
The poor delayed resonance performance above 5kHz is the major audible fault of ESL63 and the reason why there are many cone speakers which do better in DBLTs