Many university libraries subscribe to the AES E-library, so you can get papers for free. Or of course, you can copy directly
from the journal on the shelf, if available. A new AES feature I just found out about is below. There is an author fee, though.
Here are the papers currently available for free: http://www.aes.org/e-lib/online/search.cfm?type=elib&title=&oa=yes
"A growing number of countries require Open Access to the results of publicly-funded research. After surveying AES authors
it was found that a majority were interested in having the option of publishing their work in Open Access (OA). Authors who
choose this option will receive greater visibility and ease of access to their AES publications. The AES has therefore introduced
an OA policy. If an AES paper has been made OA it will have the OA logo next to it and will be freely downloadable from the
AES E-Library by anyone, even if they are not an AES member or E-Library subscriber."
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Maybe the symmetry of the part cancels the second, and the symmetry in operation is reduced with a DC bias.
The two parts of the bipolar cap would no longer have similar voltages across each.
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Just for you, this one time....... for a TT infrasonic freq filter....
I got my info from one of the ref I gave --- "Communication Acoustics....." were it was stated --> 4-5 msec..... elsewhere is 2.5 ms at 100hz.
This ref within was to Patterson, R.D. (1987) J. Acoustical Soc. of Am, 82, 1560-1586. "A pulse ribbon model of Group Delay'.
For $30 USD you can down load the J.A.S.A. Myself, I have not read it but go by the statement of 'across the whole audio..." Which i take to mean 20-20KHz.
Now if you have a better source for what ever number you have in mind, I am all ears. There may be better sources. I'll keep looking... but I tend to use the lowest value and not the highest value of GD.
Again, making only one piece of gear be good in a particular metric, doesnt mean much over-all. Esp with GD, the accumulated amount is what counts -- thru all the gear. Better to have the sum total be under the JND. Dont you agree?
THx-RNMarsh
JND = Just Noticeable Difference
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I dont know. They are all different brands. Bennic, Nichicon, Panasonic... etc.
can you do test and let me know what you find. call me, if you like. i'm up 'til midnight every night. Then do back to back and parallel with polars.
-RNM
Waly
Based on the plot you've provided will Elvees 3.33 Hz HP filter work?
Everyman
Would someone explain, or demonstrate what this GD would sound like
and where to look for it?
From this discussion this is specifically a low frequency phenomenon
that affects LPs and not CDs?
How low and where to find?
Hopefully not some obsucre piece of music. I have two candidates:
1. Christina Aguilera, Stripped. Track two, Can't Hold Us Down.
beginning 30 seconds and through out the track.
2. Pink Floyd, Man and the Machine. Track ? Welcome to the Machine.
Can't find it, borrowed, or lost. I can go get another CD.
Would the GD filter removed the bass of these tracks?
What should I listen for?
I've got Cornwall's which are ported.
These are the later versions that our own RichEEM revised for
Klipsch. I've done extensive mods to cabinet and horns to
mitigate their known weaknesses.
I'm open to be edumacated!
Of course. It's analog. I delved further into it. Fast linear servos for each laser -
nothing digital (except for the tracking display/ optional remote).
OS
Can't edit my post.
I may have been unclear.
OS, only $8K for that?
Almost, except the laser would read an analogue disc
similar to a digital CD disc, rather than Vinyl.
Think of the old style 12 inch laser discs.
The challenge then was CAV/CLV (constant
angular velocity/constant linear velocity).
The Audio Cyclopedia, 2nd ed, has a full section 18 discussing
optical film recording techniques. Why not just lay it down
on a glass master and make discs from it. Keep a pure analogue
source throughout the process.
Should be pretty easy now to scale it all down with the lasers available.
I guess now it's kind of late to the game...but surprising as the goal
is more bits...for greater resolution into the music.
In reality the music is analogue, however we can go infinitely
far into anything right? Just keep dividing it into halves....
Does/do Maxwell('s) equations have to do with digital or analogue
or both?
Waly,
I was really surprised at your comment about your speakers
being the "American Mini Monitor" or something. That got me
thinking wasn't that really made by the good folks on your side
of the pond? I kept thinking BBC & KEF kind of developed
those.
AES and other research at University Libraries... thanks Rayma.
didn't want to pay for the $145 database subscription.
I almost forgot there were paper journals any longer. : )
Cheers,
Sync
I may have been unclear.
OS, only $8K for that?
Almost, except the laser would read an analogue disc
similar to a digital CD disc, rather than Vinyl.
Think of the old style 12 inch laser discs.
The challenge then was CAV/CLV (constant
angular velocity/constant linear velocity).
The Audio Cyclopedia, 2nd ed, has a full section 18 discussing
optical film recording techniques. Why not just lay it down
on a glass master and make discs from it. Keep a pure analogue
source throughout the process.
Should be pretty easy now to scale it all down with the lasers available.
I guess now it's kind of late to the game...but surprising as the goal
is more bits...for greater resolution into the music.
In reality the music is analogue, however we can go infinitely
far into anything right? Just keep dividing it into halves....
Does/do Maxwell('s) equations have to do with digital or analogue
or both?
Waly,
I was really surprised at your comment about your speakers
being the "American Mini Monitor" or something. That got me
thinking wasn't that really made by the good folks on your side
of the pond? I kept thinking BBC & KEF kind of developed
those.
AES and other research at University Libraries... thanks Rayma.
didn't want to pay for the $145 database subscription.
I almost forgot there were paper journals any longer. : )
Cheers,
Sync
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Well obviously the filter MUST have some audible effect, otherwise you wouldn't use it. How do we know that the audible difference we DO hear is what we want, or if there is an aspect of the audible difference we do not want? How can we ever know what the difference is? Do we have an idea of what the difference is in sound between a low GD or high GD or nonlinear GD HP filter?
If as I suspect from all the posts here avoiding the beef, we indeed have no clue what it is we are wishing to hear - or not to hear.
It reminds me of a statement my boss once made at an air operations planning session: if you don't know where you're going, any road will take you there.
Jan
I did have a great day in France, great hosts, including the Veuve Clicquot at the end
I still have to arrange my findings into some coherent report, but I can give some prelims.
- speed: variation over a turn seemed about half of all the others I have been measuring. Since the main cause appeared to be the eccentricity of the record hole, this might mean that the spindle of the ELP was slightly larger. Did not measure it unfortunately, will try to have it done.
The ELP has a fine control for speed, and the two nearest settings were either 0.02% fast or 0.02% slow ....
- distortion: appears to be around 10-15dB lower than any of the traditional players.
- crosstalk also some 10-15dB better than the others.
- freq response: saw the SAME ripples towards the end of the audio range so that may also be a record artifact...
- tone arm, cartride, tonearm/cartridge resonance of course totally absent, BUT we did measure a substantial channel difference in this test, of which I have no theory at the moment.
- big issue: an abundance of clicks and pops, MUCH louder and sharper than I have ever heard! They were greatly reduced in number after the record was cleaned with compressed air so it appears to be specks of dust, maybe the dust caused reflections in the laser beams in some way.
The laser assembly was a closed aluminum cast box with numerous set screws - this thing must be a nightmare to adjust. I don't know if it was airtight, but obviously it must be open above the record read section. One idea we discussed briefly was to provide some means for slight overpressure in the assembly as to keep dust out, similarly as they do in clean rooms.
Sound quality (the important thing): fully subjectively: never in my life heard such a clean, detailed, lifelike reproduction from a record. Caveats: you really had to listen 'through' the pops and clicks to enjoy the music; and the speakers were Fertin surround-less full range drivers in a marble reflex, and I don't know what their contribution was.
So lots of things to contemplate and I at one point probably have to go back again...
Jan
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Quite wrong, Waly. I spent hunders of hours playing with that subsonic filter because on ona occasion, I received a powerful subsonic signal from an FM station via my tuner. I heard only it's like third harmonic. but that was enough to make me look up and seemy bass drivers trying to get out of the enclosures. Gave my liver quite a fright. Almost by reflex, I pressed the subsonic filter and switched it on, and the problem was perhaps not quite gone, but was at least very minimized.
I would never have expected that from an FM station, I'd think it would be the TT/cartridge/LP that would cause something like that. Anyway, switching the filter on practically eliminated the key problem and cleand up the bass lines, with perhaps a tad less volume. Nevertheless, this prompted me to investigate, so I used my signal generator plugged into the preamp to create some subsonics, fiddling around with the filter in on/off positions. And eventually reached the same conclusions Richard did, so similar in effect that I might as well have signed Richard's text.
You are free to believe or not believe this, and the point was not in your agreeing or disagreeing, i.e. not in what you said, but in HOW you said it. Come now, we are all grown men here, some decorum should be observed, itcosts us nothing but makes it easier to breathe. Less infighting, more real substance.
Thank you luckythedog for explaining.
Is there any difference btn a certain analog filter and it’s digital IIR implementation?
Pages 71-76
http://www.americanradiohistory.com/Archive-Poptronics/80s/1981/Poptronics-1981-03.pdf
I located it thanks to forr input http://www.diyaudio.com/forums/analogue-source/122129-solid-state-phono-preamp-design-philosophy-7.html#post1518394
Thank you Richard
I quote from KEF’s paper:
"Initial experiments, carried out using program material recorded using the equipment described earlier, suggested that lowering the cutoff frequency produced the subjective effect of less bass. This at first surprising result may be due to the fact that the ear is assessing the overall bass response more in terms of the frequency- dependent time delay at low frequencies, which imparts a "boomy" characteristic to the sound, rather than on spectral content."
I would like to have the underlined (by me) text confirmed as being really a "fact" before rushing out for a linear phase capable DSP package.
For some more JND GD numbers and experimental results for x-overs
Sections 5.4.2, 5.4.3, 5.4.4
http://lib.tkk.fi/Dipl/2008/urn011933.pdf
This one too
http://www.conforg.fr/acoustics2008/cdrom/data/fa2002-sevilla/forumacusticum/archivos/psy03001.pdf
George
Yes.
A 2nd order min phase lpf eg Sallen-Key with fc = 20Hz, has peak group delay c 9.2mS.......a simple 1st order min phase lpf c 4.0mS.
Digital filters are not necessarily equivalent to analog filters in the time domain. The simplest digital filter is to take an FFT of time domain samples to yield values in frequency 'buckets', modify the values, then take the inverse FFT to restore the time domain. But this does not produce the same time domain result as a minimum phase analog filter. To emulate a natural min phase filter digitally requires specific time domain correction.
In the case of RIAA de-emphasis, certainly for older vinyl recordings, the filter used during cutting was analog and very probably min phase. Then playback using a digital RIAA network is only correct if it correctly emulates an analog playback filter in the time domain. The devil is in the detail, and it's not easy to tell from specs how the digital filter works I find.
That's a bit farfetched - we all know (don't we) that the harmonics of inaudible low bass notes give us a perception of bass notes. Some manus even use that - if there is say 50Hz in a piece of music, synthesize 100 Hz and 150 Hz and you can leave out the 50 Hz with no bad effects.
So why is KEF disredarding this and come up with an outlandisch story? Occams' Razor comes to mind.
Jan
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