Those interested in performance of speaker drivers at subsonics might check out Active Impedance Control, where a separate static winding in the voice coil gap can be driven and controlled so as to manipulate lf behaviour. Requires custom drivers and control circuits, but if one is into extraordinary subsonic performance from realistic domestic speakers, this might be the bag.
I've heard systems based on this method, and was thoroughly impressed. Perhaps the only viable alternative to TL loading for proper sub bass extension in domestic cabs (I use TL).
Check it out, there's an AES convention paper 118th Convention May 2005, "An alternative approach to minimise inductance and related distortions in Loudspeakers" Carlisi, Cola & Manzini.
I've heard systems based on this method, and was thoroughly impressed. Perhaps the only viable alternative to TL loading for proper sub bass extension in domestic cabs (I use TL).
Check it out, there's an AES convention paper 118th Convention May 2005, "An alternative approach to minimise inductance and related distortions in Loudspeakers" Carlisi, Cola & Manzini.
Jan,
I didn't know that Belgium uses the US Constitution, first amendment!
We don't, but there is a link (putting on my Dutch hat now).
In around 1568 the Dutch decided that they had had it with a Spanish king ruling the Netherlands. A bunch of smart guys got together and wrote a 'Plackaet van Verlatinghe', translates roughly as 'Declaration of Independence'
It started as follows: 'We, the people of the Netherlands....'.
A couple of centuries later it was picked up by a bunch of ex-Britisch convicts in what is now the United States of America, and the rest, as they say, is history.
And no, I'm not very impressed by the heavy battles these so-called Americans had to fight for their independence.
Our independence war, which started in that year 1568, lasted till 1648. Yes, that's an 80-year war - how's that for stamina??
History is sooo underrated!
Jan
OK, bad choice of words on my side.
But honestly, I often wonder whether you state something because you honestly believe it, or whether you just want to stoke the fire. Because there is a dichotomy when someone as accomplished as you, obviously as intelligent as you, sometimes comes up with something that for all intends and purpose comes across to many of us as pure BS.
Sometimes you're a mystery John....
Jan
One of my perceptive heydays, somewhere end of the 90-ies, was a demo at my house of my new speakers. Had half a dozen audio friends invited, playing all the usual music and awing about the sound stage, balanced reproduction, the works.
After about half an hour I switched off the Bose fake stereo that had been playing in the bookshelf and switched to the speakers.
I think it took over a year before my friends trusted me enough to come visit again.
But you are right, it's all about perception.
Jan
if you accept the anecdotal subjective "evidence" of "believers" for "preferring the sound of wide bandwidth amplifiers" that's fine as far as it goes
when you start with engineering signal theory specific terms like TIM, PIM and their interaction with circuits, feedback then you are stepping into a thoroughly examined world in theory, sim and measurement which leaves no room for the claims that "wide bandwidth" is the only or even a preferable choice to reduce TIM, PIM
to keep reasserting that TIM, PIM "explains" "the preference for wide bandwidth designs" is to ignore how EE "constructs" knowledge
DVV you have said yourself that you have not given Cordell et al a fair reading on the subject and express no interest in doing so
that's a free choice - but the consequence is that you should quit making "fact claims" on the subject
To be honest, we did take out a decade here and there from the 80-year war to do some business - after all, someone has to pay the soldiers.
Jan
That was then, but now is now, in the meanwhile I did catch up, thanks in good part to this forum and the links supplied.
After that, my view remains the same. I cannot turn a deaf ear to what I hear at home, day in, day out, including the borrowed amps. Remember, I did not and would never claim that a wide bandwidth, low GNFB amp will by default sound better than a low opam loop amd with loads of GNFB - I said that in my view a low GNFB amp has a better chance of sounding good. In my experience, this is indeed so.
My current working amp is a Harman/Kardon PA 2400, nominally 170W/8 Ohms, bandwidth quoted as typically 400 kHz at rated power output, using they say 12 dB of GNFB. It is one of the best amps I have ever heard on my system, no matter which of the three pairs of speakers I choose to use. I do not claim that it is the best amp ever, it may be that only in terms of Hamarn's production, and I have heard at least 90% of what they made. It's a significant step up in comparison with Citation 24, which I also have, and is a clear evolution of the basic circuit as found in Citation 24. Clean as a whistle, with oodles of power reserves. And I haven't got around to refreshing it yet, it's still playing with full original factory parts now some 18 years old.
OTOH, you may remember that I mentioned several models from other sources based on much greater GNFB factor which I did like and wouldn't mind owning, such as say Yamaha M-4, the cheaper version of M-2. What may well have irked some people here, I also mentioned Toshiba/Aurex SB-45, a very cheap model from the early 80ies, which makes some excellent music at a standard well above its price point and general class. I own one, so I should know. And after beefing up its PSU with larger caps, it expectedly sounded even better.
To me, the GNFB should be the icing on the cake, something one adds to sort of iron out a freshly washed drip-dry shirt, not a method to cover the imperfections. Therefore, it is only one of many aspects of making a good amp, and in fact, applicable only to already well designed circuit. Lastly, I believe that the threshold of hearing classic THD, assuming no subsequent irreguarities, such as an odd decay rate, sudden jumps of THD at some point, etc, is 0.1%. If so, then it would be advisable to get it down to less than that, say 0.05%, up to its rated power into even complex loads.
So what's wrong wih that philosophy, unless you believe we need THD to be below 0.001% to be inaudible?
Remember that Denssen Beat 200 (I think it was) power amp delivering nominally 100 WRMS/8 Ohms which used zero GNFB. In its time, it was highly acclaimed, not least by the British audio press, as exceptionally clean and clear. I had it for two weeks at my home, and frankly, I was underwhelmend, somehow it sounded unfnished to me, a little too loose for my liking. I accept GNFB as a useful tool, in fact I think it should be used, but in moderation.
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1- I suppose, if you are an 'audio' designer, that your knowledge is wider than the one you can find in such vulgarization books, or, at least, equal. Specially when opinions expressed in some of this books are very partisan. (Bob, it is not for you ;-)
3- I was taught at school to verify everything by myself and not be a "believer", because it is the only right scientific method.
2- Nothing replace real experience. And, on this subject, based on my own experiences, i have the same feeling than dvv: better the slew rate, better the distortion factor, better the sound. Now, if you ave a recipe to find the best compromise between those two goals, you are welcome.
3- On a theoretical point of view, it seems obvious than, keeping the feedback ratio (when using feedback) and phases as constant as we can in all the audio band is better for "coherency".
4- We are dealing with imperfect components. Each amp i have listened to have his own personality (imperfections). This let the door opened to listening and subjective preferences. The blind faith in words (theories) or simulations is just a very naive position. The kind of position that can lead-you to believe our planet is the center of the universe. Are-you sitting in the Inquisition court ?
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The purpose of a book is to let you make great steps in building your own understanding and knowledge.
Nobody wants to reinvent every wheel ever invented. The phrase 'standing on the shoulders of giants' is very appropriate here.
A good reader understands that any book is a personal perspective backed up by facts and figures. Blindly accepting everything you read is as daft as thinking you know it all because it all seems so right to you.
Jan
Nobody wants to reinvent every wheel ever invented. The phrase 'standing on the shoulders of giants' is very appropriate here.
A good reader understands that any book is a personal perspective backed up by facts and figures. Blindly accepting everything you read is as daft as thinking you know it all because it all seems so right to you.
Jan
Our natural laziness protects us from this risk ;-)
But, sometimes, it helps for discovering new things, to look at the things upside down.
Jan, we are not building amps to provide the best measurements numbers on our bench tables. But to feed VERY imperfect speakers in order they reproduce imperfect recordings in the most convincing way. I use to say "A make believe game".
Imagine you got this terrific bad amp that present the exact opposite distortions that your speakers will create, cancelling them. You will never buy-it, according to its *specifications*.
It will measure bad ... and sound good in your system.
You will lost something if you don't refer to what you hear.
According to what seems your usual 'objective' positions, you will just say "You like distortion" and don't even try.
On my side, i had spend a lot of time in my yet long life to figure out all those "feedback" behaviors, trying to make *my* religion.
And, yes, I tend to prefer CFAs, high slew rates, and don't believe in this "If you use GNFB, use a lot" witch seems to be a religion in this forum. Because it contradicts my own experiences and (it seems) some other's experiences. And I don't try to impose-it to anybody else.
And i'm not sure at all that some of the violent opponents had spend even a second of their time to listen to a good enough CFA amp, and, thus, tried to figure out the reasons of the difference (if any) they felt, see what i mean ?
Jan, speaking for myself only, I do not deny in any manner Mr Cordell's work, which to is represented by his book on amplifiers and the two texts on another look at TIM, both of which I have and will keep. I wholeheartedly applauid him for his work, never mind whether I agree with all of or not, I believe his book on amps is the best I have ever seen from anyone.
However, while not denying him, I keep my point of view simply because over the decades it has taught me that I will gett pleasing results with it easier than with his approach. He is not wrong and I am not right, those are simply two approaches to the same problems, both of which are known to work.
Just one detail regarding Christophe Esperad0's 4 point list: my upper range is generally set, as THE objective, to have the "natural" (i.e. open loop) slew rate at the point where it satisfies the 1V/us/Vpeak of the amp, i.e. say 40V/uS for a nominally 28.3 Vrms of output, or at least as near to that point as possible That implies an OL bandwidth of around 110 kHz. Good PCB esign and carefol parts positioning can get you as high as 120 or even 130 kHz, although it assumes very closely matched transistors on no more tha a 2% difference - meaning a lot of work, and having good device populations at hand to choose from. Since one of biggest local salesmen of parts is a good and old friend. so I always have a solid population to choose from. Nelson Pass was right to mention once somehwere that for a close match of two discreets you need a population of around 100 devices.
However, while not denying him, I keep my point of view simply because over the decades it has taught me that I will gett pleasing results with it easier than with his approach. He is not wrong and I am not right, those are simply two approaches to the same problems, both of which are known to work.
Just one detail regarding Christophe Esperad0's 4 point list: my upper range is generally set, as THE objective, to have the "natural" (i.e. open loop) slew rate at the point where it satisfies the 1V/us/Vpeak of the amp, i.e. say 40V/uS for a nominally 28.3 Vrms of output, or at least as near to that point as possible That implies an OL bandwidth of around 110 kHz. Good PCB esign and carefol parts positioning can get you as high as 120 or even 130 kHz, although it assumes very closely matched transistors on no more tha a 2% difference - meaning a lot of work, and having good device populations at hand to choose from. Since one of biggest local salesmen of parts is a good and old friend. so I always have a solid population to choose from. Nelson Pass was right to mention once somehwere that for a close match of two discreets you need a population of around 100 devices.
In a live rock music (or something like that) event, the thump in the chest is due to raw acoustic power within the acoustic bandwidth (the bass low note is 41Hz)
.
There are subsonics present and they are powerfull. They are produced due to the acoustics of the space where the event takes place and the reactions from the crowd.
But there are no subsonics coming out from the speakers there.
There is serious frequency band limiting applied at these audio installations. If not, there would be no amplifiers and no speakers left operational.
I am aware of it and I respect the technical aspect of your work as I respect the work of anyone else here.
That is one more reason for the disappointment I had reading your previous post.
Thank you for the information.
I found it but I don’t see that system doing anything at low or very low frequencies. Do you mean something else?
http://www.eighteensound.com/Portals/0/Img/Img_tech/doc_tech/18_Sound_AIC.pdf
George
Convicts? I think you're mistaking us for Australia.
He has certainly managed to change my mind about that.
... Too, in huge halls, the structure can be exited by the high acoustic level and generate some very low frequencies... that we try to remove from live recordings because they are just parasitic, muddy and eat space in the usable dynamic...
As "the tax kills taxes", extreme basses kill the basses ;-)
I remember a concert of "Dire Strait" in Paris. We had a backstage pass with a friend, and were bored rapidly by the show. We moved to the roadies rooms, two stages down in the building, playing pingpong with some of them during the end of the show. A very strange experience, with all the building resonating at low frequencies with the music on stage. One of the most strange sonic atmosphere i ever heard.
As "the tax kills taxes", extreme basses kill the basses ;-)
I remember a concert of "Dire Strait" in Paris. We had a backstage pass with a friend, and were bored rapidly by the show. We moved to the roadies rooms, two stages down in the building, playing pingpong with some of them during the end of the show. A very strange experience, with all the building resonating at low frequencies with the music on stage. One of the most strange sonic atmosphere i ever heard.
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Well the Pilgrim Fathers were convicted. Of heresy. They did come from the UK before settling in Holland, then moving to Massachusetts when they were convicted here too. Or maybe it was 'just' persecution, could be. But they were considered bad people, at the time.
Edit: they had religious freedom in NL but moved to Plymouth because they were concerned to lose their British identity in NL.
Jan
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