Theo Verelst Local Diary Page 25

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June 18 2003, 14:35

Lots of 'stuff' on this page, not earthshattering per piece, but interesting materials.

One section contains very strong material which is an electronics challenge at high level, and a fun idea: making a sound synthesis machine by simulating strings using a hundred meters electrical coax cable as electronic delay element. Interesting, and supposed to at least bring forward a unique and challenging electronics project which maybe doesn't contentwise challenge the great ones all too much, but the thinking line probably is a real challenge, especially when more then one string are supposed to interact at high speed 'simulation' time. Piece the la resistance? Probably, but: I didn't make it yet, I just 'claim' the subject and the ideas, and make credible the implementation is possible, hopefully also on a small budget.

Stereo in the park

I fitted the small portable speaker set with new (decent) Visaton dome tweeters, and tested then the day before a festival in the park, that went succesfull.

(click on some images for a little movie)

Next day:

somewhere else in amsterdam (after my Rock 'n Roll page...)

Some window:

Go to the jimmi concert, but pass death first ?

A little later, I tried the new powered, bi-amped electronically filtered speakers out in the park also, which appeared after a little trying out not to be permitted by the police... But was fun anyhow.

The car battery is on the back of the bike, the converter behind the left speaker. It was LOUD, but not extreme, but extremely good quality. Better then most people ever hear.

A super real-time electronics string simulator with 100 meter coax cable

Some time ago I presented my longer existing idea of a string simulator as implementation of the 'physical modeling' idea from recent sound synthesis algorithm advances based on the latest DSP and technolgy being available.

I tackled the problem from a physicists point of view with a straightforward sampled model where a string, suspended between two points, like the bridge and the comb of a guitar

A wave in a string suspended on both ends

is divided in a number of points (lets say a hundred) which are simulated as coupled mass-spring elements, see my (unfinished) page on the String Simulator Sound Synthesis Program.

Here I want to bring forward and claim the idea of using a long coaxial cable which is driven by contemporary electronics very fast DA convertors to contain a wave (like a string) with a wavelength of lets say a hundred meters, corresponding to a fundamental standing wave of 3 MegaHerz.

A handy roll of 250 meter low loss coax for Euro 99,-

Fast AD converters available from for instance AD and TI like the ADS5423

80 MegaSample per second 14 bits accurate Analog to Digital convertors can be bought on evaluation board and are fast enough to measure a significant number of harmonics of a 3 Megaherz fundamental accurate enough to downspeed to audio speeds, maybe with a few averaging samples to get to 16 bits effective.

So the setup is more or less like this:

The drivers contain DA converters in the 100 MegaHerz range, preferably 14 or 16 bits with good buffers, which also allow cross-coupling the string simulating coax cables, the signal can also be read back from the end point of course, couling the AD converters there.

The termination electronics should represent a fixed point (full reflection) unless (maybe with a cmos switch) the strings are to be 'emptied' or silenced, and it is required that the end of a guitar string is simulated by a short length but gradual medium change, like is partly responsable for the characteristic sound of the string simulator I made in software, and where in software the guitar string axial sampling easily becomes an accuracy limiting factor.

Cable ohmic impedance and frequency dependent damping are an issue which might limit the resounding time of the guitar string simulation, but that's interesting research, electronic signal reenforcement at these frequencies is possible at reasonable quality with modern opamps for instance.

This spartan-3 FPGA can be used to produce and read 100MHz signals from its connectors, I've worked with it a bit already, and it can beconnected to for instance the Blackfin 561 32 bit bus dual cire 500MHz EZ-LITE DSP board I can use, like I did with the (less powerfull) CoolrunnerII CPLD for the synthesizer I made with the BF533 EZLITE board, or maybe the serial connection can be used to transfer data at higher speeds then 9600 bps to a PC, and possibly I could make an optical audio link to the USB AD/DA converter for getting a good audio signal.

The memory on the starter kit can be used to store waveforms, though it might have to be used wisely for high quality signals.

The most important idea in the setup is the coupling of the strings, which is hard because the result of the coupled simulation is not at all the same as the seperate simulation of two strings with different lengths, because of the continuous interaction.

To make this setup wolk as an instrument, some way will have to be found to dynamically change the string/coax lenths... !

Very complicated, and therefore challenging and interesting.

This setup is not up to the beginnings even I think of machines like this:

The HP E4440A PSA Series Spectrum Analyzer , 3 Hz to 26.5 GHz (from US$ 55,091)

but the price tags aren't very compatable either, nor the research labs which invented them...

Tony Joe White

At "het plein" the North Sea Jazz Heats The Hague offered a free performance of Tony Joe White, which is a famous blues singer / composer, amoung others for Elvis Presley and Ray Charles (Rainy night in Georgia). I knew 'so hard to handle' which is more like a rock song.

This was my registration setup, including my own made microphone setup on the trashcontainer.

The above recordings were made using only the Sony digital handycam with buildin microphones. These aren't perfect, and there is more than a bit compression, but then again they certainly aren't bad.

The reason I didn't use the seperate mics is that they with the cam 'fantom' viltage (which is low) distorted from the PA sound level, just like that my own preamp which I fed into the high quality USB AD converter into the notebook didn't have a low enough sensitivity to not destort except for one of the first (indonesian) bands, of which I made this little

example computer audio recording

In CD quality. Very much worth listening to on my full range personal PA system, where I use the 2 4-way speakers on the 2x100W amp together with a 15 inch (pretty large that is) subwoofer (see previous diay page ): the orginal HiFi (High sound Fidelity) adagion is honored by getting pratically the same sound in the living room as during the concert: living and heavy low, not so grwat high (...) and driving (bit pronounciated) midrage. Most of all: very close to the concerts sound, so the microphones, the analog the digital converter, the hard disc recording (no processing whatsoever), the digital to analog converter, the amplifier and the speaker setup are very close to recording exactly the sound and reproducing it without much coloring or distortion, though of course to have the same sound impression as at the concert, the 100watts and the 200 wats sub power must be used to significant extend...

But then it actually sounds the same as the concert PA system. That cannot be achieved with any home stereo, and quite franlly not with many studio monitoring systems that I know of. To much frequency and low-distortion low frequency reproduction, to powerfull and controlled midrange and to accurate high frequency response and lack of AD/AD filtering effects are needed for that. And more raw power than an average home system can produce in practice over the whole audio range. And expensive Hifi Systems usually sound to meek or weak, frankly...

And the 'brutal' milkpackahe size speakers with more than little power rating are waaayyyy to ugly in their bass response to be any good with their sucking bass reflex and everything, and even with that simply don't push enough well controlled (distortion poor!) air through a medium or low quality acoustics environment. Maybe in a small, damped room close to the ears.

Then again this setup requires almost a few square meter speaker front area to look at, ut than again, I don't mind seeing speakers in front me, that's fine for me. I'm sure the amps power and quality don't come cheap either for consumers or pros to buy, so it's not possible to communicate live music to great audiences yet, unfortunately, at the moment!

So, work can be done.

North Sea Jazz 2005

I was lucky to be sponsored again to the NSJ festival which I enjoy most of the time, and this was for a part dedicated to seeing and hearing Mr. Weather Report: Joe Zawinul, see picture (on the left behind the keyboards):

The keyboard setup contained most visibly of a Korg Prophesy, a Korg M1 (well know but older), a rack full of for me unidentifyable gear, and probaly a brandname taped prophet 5 well known sort of vintage but still completely valid synthesizer

Wonderfull sounds. Sometimes almost stupid world music stuff from some other band members but never over the line, great listening.

On the big stage too, with a big round pile of PA speakers right in front of me on the stage the siz of my own, we saw mr Robert Cray and band perform, with very good sound except for the sideway (where I wasn't) hung semi circular speaker arrays which sounded lousy, but then again not too ugly or wrong either.

My self made picture.

Halfway the show the hammond B4 organ was screwed open with its open back visible:

Funny.

Late a t night there was a jam session in principle of considerable standing (except for the lame audience) with mr Zawinul, mr John Scofield (on guitar) and mr Toots Tielemans (harmonica).

3 great moment at least, the last probably being just before the in session ending of Zawinuland demontaging his rig by the roadies when he placed a well sounding prophet brass stab trhough the powered speaker pile. Great.

The synth setup in the basement before the gig started.

I'd imagine it isn't nice to have somebody look you 2 meters aeway over the shoulder during performance. Well, the dutch are crude at times.

Scenery pictures

Scheveningen (the Hague beach):

From the ocean view apartment, cross the boulevard, into the quiet morning (picture was in the evening) pool. MM, that sounds like the better life....

And now for something completely different:

This is at the spot where there used to be another statue, not a buddah but a Moloch Monster Head, see diary page 10

The standholder asked me to come down and make a picture and inquired wether I liked the statue, and I said well, it's of a certain beauty maybe, but I don't like the buddah idea.

Snapshot from Amsterdam:

The badkuip revisited

Sort of literally, I taped a small piece of the cafe's sunday jazz session, without playing myself, that's been some years.

Maybe I should try my powered speakers and the synth module out here some day in the sunday session, or would that be pushin it, what do you think?

Bible Translation hasn't even really started yet

That sort of my idea about it, since I've been mainly on my own in the subjects for years, and no one offering their greek or hebrew skills or a nice university project I guess I'll be my own leader and manager.

And the leader sais: the christian world is full of rubbish so much that it's not funny and all those countless bible translations too, that at best it is proven that some higher instance has not given the subject away or that people have nit been willing or able to go really further in lines that I've been thinking about, unless maybe to steal and destroy.

I have been fortunate to get my hands on another Benjamin Davidson hebrew lexicon, what amazon.com is good for...

(View the Moog film trailer in quicktime from here. )

random example page:

Years ago already I wanted to research

my own hypothesis for pictorial hebrew character meaning.
hebrew letter based translation examples

Ezechiel 7:10

Now will I shortly pour out my fury upon thee, and accomplish mine anger upon thee: and I will judge thee according to thy ways, and will recompense thee for all thine abominations.

And mine eye shall not spare, neither will I have pity: I will recompense thee according to thy ways and thine abominations [that] are in the midst of thee; and ye shall know that I [am] the LORD that smiteth.

Behold the day, behold, it is come: the morning is gone forth; the rod hath blossomed, pride hath budded.

Violence is risen up into a rod of wickedness: none of them [shall remain], nor of their multitude, nor of any of theirs: neither [shall there be] wailing for them.

The time is come, the day draweth near: let not the buyer rejoice, nor the seller mourn: for wrath [is] upon all the multitude thereof.

For the seller shall not return to that which is sold, although they were yet alive: for the vision [is] touching the whole multitude thereof, [which] shall not return; neither shall any strengthen himself in the iniquity of his life.

They have blown the trumpet, even to make all ready; but none goeth to the battle: for my wrath [is] upon all the multitude thereof.

'pride':

HGEDIT.TCL, the fonts are in this zip file: hgedit

I received a free copy of this CD at last years Fosdem conference.

Where is it going with dutch universities, I saw this anouncement on the board at the language department recently, what a ripof of my work, and what a dreadfull fascist level. Tsk Tsk, shame on you all.

Le Monde still on it's track

"Why foreign countries ignore french artists":

Unbeatable Physics

from 'science':

A black hole is a mass which is concentrated so much that its gravity keeps pulling it smaller.

The small PCB USB High Quality AD/DA finished

except for the optical out link, which I've used on the other prototype I made (and blew the chip to pieces of, recently..).

Texas Instruments was kind enough to in spite of a sample request status escalation (I should have checked the company name in my registration) send me replacement prototype AD/DA chip samples. So I must be into tiny wire desoldering without wrecking my self cut prototype circuit board, and soldering a new chip in. Brrr.

Loudspeaker technology

From a book on loudspeaker measurements:

That's like a section of the string simulator...

So we have a piece of paper which can be pulled back and forth by applying an electrical current to a coil which then magnetically pushes ore pulls the cone back or forth, guided by a spring type construction and the rubber or paper rim of the cone, with a certain amound of friction and a certain spring constant.

For normal speaker use, the excursion (how far the speaker moves) is determined as a result of the amount of voltage coming out of the amplifier onto the speaker connectors because the coil moving in the magnetic field generates a counter electromachnetical voltage until that is as large as the applied voltage minus the current flowing though the coil needed to excert the force coming from the voltage difference over the speaker impedance.

And the dynamics (the acceleration and deacceleration of the weight of the cone) and the weight of the air being pushed and the dynamics of the airflow around the cone (back and front) contribute to the motion of the cone while stable state isn't reached, and the latter of course determines to sound decibles and waveforms being emitted from the cone.

In an enclosure the airflow is also not simple, because the (average) pressure changes when the cone pumps air in or out, and the waves emitted into the enclosure to some extend are bounced back at it. Damping material will change how much that happens.

The damping of the cone takes pace either only trough air (gives resonance) or also by the excursion dependent friction of the speaker suspension rim. The non-linear distortion is influenced by the spring constant linearity and magnitude of both the backside gaze and the front rim excursion dependent force.

And then there is the question of how much power is given to moving air after all this goes in to action, and in which directions.

This is very different per frequency, basically, at least there are 3 main cases: sound wave wavelengths of much larger size than the speaker cone diameter (low frequencies) sound waves about the same size or just a bit longer then the speakers's size, and sound waves which are (much) shorter than the speakers overall moving part size.

The latter is to be prevented usually to great extend, waves will become directed and usually distortion increases as it might happen the cone material breaks up and deforms.

Around the wavelength speaker size is often desirable for tweeters, which can't be much smaller than the highest normal audio frequency wavelength corresponding to 20 KHz which is abour 1.5 cm, the size of a small dome tweeter. Looking at radiation graphs of dome tweeters, it becomes clear that already with this size for high frequencies the radiation pattern starts to become oneven because of wave patterns (possibly in combination with surrounding geometric considerations).
See for instance this visaton tweeter DMS25 directional radiation graph:

For woofers, usually the main range of frequencies they reproduce is such that the wavelengths of the generated sound are much larger than the cone size, though in principle a 30 cm woofer could reproduce a few kiloherz corresponding to 10 cm or so wavelength, which however usually is not such a good idea unless you have very stiff cone material and strong amplifier damping and sufficuent power.

The large wavelengths for the lowest tones makes it hard for most woofers at some point to reprodce the very lowest frequencies, the air resistance become more or less proportionally smaller with lowering the frequency so less power for the same amount of cone motion results. The bigger the cones the later this effect becomes bad, large speakers will still move a lot of air at low frequencies.

The other factor here is called the self resonance of the woofer (or mid toner of tweeter), under which the is little air driving or output power. Self resonance is determined by the spring weight approximation of the speaker system, and it boosts low frequency reproduction up the graph of the self resonance untill the peak. Under self resonance, which is also determined by the speaker air content, output decreases rapidly.

Bass ports and reflex constructions are never an excellent idea in general for HiFi sound: there is always a doubling of low frequency wavefronts, which is always, predicable not perfect sound reproduction, sorry. And even worse: it cannot really be compensated for in the signal, like frequency dependent errors and even to some extend non-linearities can in principle be countered through signal processing.

The only proper high end use for reflex or 'port' constructions is the construction of a pathways through the speaker box with an effective length longer than normally the air column size in that speaker cabinet, to make sure standing waves between the opposite sides are made different, to fit lower frequencies, and to possibly make a labyrinth construction with long way damping. That may actually do good to fight in cabinet reflections.

For the rest: bass ports are evil for high quality, distortionless bass response. Period.

Not that disco speakers can't be fun with them, and like in the past, low amplifier power can be compensated by them, but they all sound the same after a little while (to trained people: after half a minute...) and especially those very small speakers pump and compress air and suck bad in their bass response, even though at first sight the 'big' bottom end might seem attractive. Don't fall for that: your daily listening experience will suffer, and after a little while your speakers might start to annoy you.

Anyhow loudspeaker practice of mine recently made me put the 4 channel amplifier (!) and active filter (with the best audio opamps in the world) into the not too big speakers with its supply unit, and the woofer/midtoner and the the tweeter and the isolation material.

Works very well, and the technical specs of this machine are excellent, probably better preamp/filter and end-amp quality than most people ever hear (or get from a hifi store).

Now maybe I'll use the software from here to test things, like I've tested filters and speaker responses.

Web analysis from the magazine library

It seems engineers read the least of all, or more condensed...

I'm reading the latest sandford I could get luckily short after it came out via the americal bookstore, the digikey catalog came for free, the library bool was with the 'new books' section and caught my attention, and of course I was lucky to keep up with my professional field of interest trough main magazines from the pro sound/music field.

Illuminati, what are they good for?

A war? Possibly Has happened before.

This stuff can also be found on university poster boards, which I find dreafull a sign:

A site exposing free masons and their fake christ:
http://www.ephesians5-11.org

And the web encyclopedia concerniong rosicrucians (what a name):
http://en.wikipedia.org/wiki/Rosicrucian

I'd put some videos of the main guru of free software Mr Richard Stallman on the belgium FOSDEM conference site, but their servr seems not up to the video bandwidth...
http://fosdem.3ti.be/Theo.Verelst/2005-weekend/

At I think Europes largest open source software conference theor was a plenary speach about the (large) free wikipedia project:

wikipedia.mpg 1megabit/sec mpeg1 video (cannot be uploaded completely realtime, server is 33 percent too slow)

Well, I guess the illus are not too smart about the essence of life, anyhow:

Parrots in the park

With a book, a mobile, and a camera I've been studying birds in a park, these are the most exquisit plumage around: lots of parrots!

I'm sure ducks and pigeons and other birds have complicated knowledge about social ongoings, and wave patterns, for isntance, which at times is great fun.

They don't like veiled moslims either, just like I don't.

Coils

A chapter on coils, that's new, the picture shows some samples I received from coilcraft.

Shown are a 7th order high cut filter, small USB intended emi filters (I've used similar ones on the USB AD/DA converters) and a big shoke filter for main filtering.

Living white copied Audio CD collection

From the library (legally rented) I made copies for my own use of various important audio CDs, wanna see the list?

Don't ask me for mpegs, I don't have them and I am not going to make them! CD Quality is nice, but hopefully the super audio CD will be usefull soon to overcome limitations.

I've put my Rock and Roll page link on the wikipedia, on the rock and roll page.

I found The Comets on the nasa website, from Bill Haley (who's deceased) with rock around the clock footage combined with the destructive comet research...

The secure server message possibility

Well, it used to be there all the time, not used so much, only now and then: this link https://www.theover.org/guest to leave a message to the server I am running, over a secure link.

Since a hard-disc renewal of the server machine, you have only http://82.168.209.239/guest at your disposal as alternative to the email channels because I have to put some certificates in place which I haven't (yet), or maybe generate new ones...'

So no secure messages till further notice. Don't hesitate to push me to do so over email of course!