Quick question

Cost.

Art is good if someone will (willingly) pay for it. Like real estate, it is only as good as someone pays for it.

It's dead, Jim.

You need to get off work earlier >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Wuz at work. ;-)

l force more power into the speaker, making a boom peak at that frequency.

difference to a current drive, which would force exactly the same current through the coil as at any other frequency (if it could apply enough volts across the coil).

tion. Loudspeakers are notoriously inefficient so it won't be anything acoustic, and the voice coil's inductance is generally swamped by its resistance.

There are three response curves listed - presumably for the three different enclosures mentioned, and one impedance curve for which the enclosure does n't seem to be specified. A 7" woofer is pretty big and it can be mounted t o give significant acoustic resonance, but the single impedance curve peaks at 32R, not exactly a high-z resonant peak for 5.65R speaker.

h much of the useful bandpass (e.g. 100 to 2000 Hz), and rises to above 32 ohms at 50 Hz (which is approximately the F3 frequency of the driver when u sed in one of the suggested vented-cabinet alignments).

If used with a voltage-output driver. There's nothing magic about the desig n of the vented cabinets - you'd tune them to suit the driving amplifier yo u planned to use.

you'd see a big bump in the SPL graph at around 50 Hz, as the power deliver ed into the driver would roughly quadruple at resonance.

Probably. But you wouldn't use a current output driver with an enclosure tu ned to match a voltage output driver.

nd tweeters as well.

Only if you don't know what you are doing. A fairly common condition with a udiophiles.

--
Bill Sloman. Sydney

observe, not DEFINE it.

That is the problem with the subjectivist point of view - their descriptions weren't reliable or reproducible when carried out under double-blind controlled conditions.

--
Bill Sloman, Sydney

On 01/07/14 17.29, RobertMacy wrote: ...

That is correct - with a but:

If the seller prepare the testing with music from some specific media:

• do you trust the seller is neutral? Do he want to sell some specific hifi system?

That was what I meant with "your perception, that the test was conducted well?". In other words you have to notice the context in which the tests are conducted.

I have for many decades tried to find out what makes sound systems sound better or worse.

I have read a lot of articles, both scientific and from hifi/audiophile magazines. I have also heard many systems, and most of them sounds terribly. Some sounded good, but was at the time to expensive for me.

I have built my own PA ("The End" with TIP35 TIP36, DC-coupled), and pre(phone,line,tape input) amplifier (BC413, BC414, 2SC2240, 2SA970) both from a danish magazine "High Fidelity", but the end result was not good according to my ears, but the speakers was maybe not expensive/good enough?

The PA and amplifier was built with standard components (transistors, capacitors). I did not have enough money for ring emitter power transistors, specially "blessed" capacitors - especially if/when I would burn some of then. And I did burn some transistor :-)

-

The (missing) quality of the audio system was easily tested; hear birds and everyday sounds and compare them with the audio system. The audio system was ditched. I still have the system, but I do not use it. :-)

Now, some of the electrolytic capacitors are possibly dried out.

-

Some time ago I when to a danish exhibition "Eksperimentarium" (

) and one of the experiments was to compare to sinus tones to find out how good (or not) you was to hear the difference.

When I focused on the sinus tones, I could not hear the difference at say 1...2%, but when I focused on the resonances of the speakerbox I could discern 0.1%? (perfect pitch according to the scale) - it is some years ago.

What is right? Do I have perfect pitch or not? It depend on what I focused on... so what is scientifically correct? I do not know; that is why you have to mix science and the good measurement of your ear, to be so objective as possible.

University of Chicago (2013, June 11). Perfect pitch may not be absolute after all. ScienceDaily:

Quote: "... When tested afterward, people with perfect, or absolute pitch, thought notes made out of tune at the end of a song were in tune, while notes that were in tune at the beginning sounded out of tune. ... Heald changed the tuning to make the music a third of a note flatter than it was at the beginning of the song. Hedger never noticed the change, which was gradual, and was later surprised to discover the music he was playing was actually out of tune at the end. ..."

Jan 31, 2013, Human hearing is highly nonlinear:

Quote: "... People can simultaneously identify the pitch and timing of a sound signal much more precisely than allowed by conventional linear analysis. That is the conclusion of a study of human subjects done by physicists in the US. The findings are not just of theoretical interest but could potentially lead to better software for speech recognition and sonar. ... Oppenheim and Magnasco discovered that the accuracy with which the volunteers determined pitch and timing simultaneously was usually much better, on average, than the Gabor limit. In one case, subjects beat the Gabor limit for the product of frequency and time uncertainty by a factor of 50, clearly implying their brains were using a nonlinear algorithm. ... Mike Lewicki, a computational neuroscientist at Case Western Reserve University in Ohio, says the research is "a nice demonstration that our perceptual system is doing complex things ? which, of course, people have always known ? but this is a nice quantitative demonstration by which, even at the most basic level, using the most straightforward stimuli, you can demonstrate that the auditory system is doing something quite remarkable". ..."

From the danish magazine "High Fidelity", and I only have copies, not an internet link - sorry.

On 02/07/14 04.58, Glenn wrote: ...

...

More articles about hearing:

Cell Press. (2009, March 20). Language Of Music Really Is Universal, Study Finds. ScienceDaily:

Cell Press (2010, May 21). What makes music sound so sweet (or not). ScienceDaily:

Quote: "... Whether you would get the same result in people from other parts of the world remains to be seen, McDermott says, but the effect of musical experience on the results suggests otherwise. "It suggests that Westerners learn to like the sound of harmonic frequencies because of their importance in Western music. Listeners with different experience might well have different preferences." The diversity of music from other cultures is consistent with this. "Intervals and chords that are dissonant by Western standards are fairly common in some cultures," he says. "Diversity is the rule, not the exception." ..."

Institute of Physics. (2010, May 21). Get rhythm: Why the key to finding music you like is rhythm, not genre. ScienceDaily:

BioMed Central. (2011, January 24). Creating simplicity: How music fools the ear. ScienceDaily:

Quote: "... For a composer -- if you want immortality, write music which sounds complex but that, in terms of its data, is reducible to simple patterns. ..."

Max-Planck-Gesellschaft (2012, November 29). Making music together connects brains. ScienceDaily:

Glenn

You sound like a guy I used to have arguments with, about his lottery winning software. It recorded all the previous winning numbers. Basically he thought that if there were then an excess of 9's, say, then that made a 9 less likely in the future!

He also insisted that a result say 3456097 was more likely than 9999999 or 1234567.

In fact the only reason (I can see) to bet or not on some particular number is if prizes are shared, because you then need to consider how many *other* people made the same choice. So out of several million people you might well have 10 contrarians choose 9999999 and you would only get 1/10 the prize you "would have" got with a randomly chosen number. (Which is in fact therefore the best strategy, apart from not betting at all of course).

--

John Devereux

[...]"

This is incorrect: the force on the moving coil of the transducer will be proportional to the current through the coil (if the magnetic field is constant). It does not follow that the rest of the mechanical system will convert that force into sound waves in a proportional manner. The author of the paper is under a fundamental misapprehension (assuming that the summary has not suffered from misrepresentation or mis-translation).

This appears to be substituting mechanical damping for electrical damping. There is nothing wrong with good mechanical damping (as long as it does not reduce the efficiency too far), but electrical damping is usually more effective. Removing the electrical damping on a loudspeaker which was designed to be electrically damped (most of them are) will not give an improvement and usually makes it a lot worse. Removing electrical damping on a loudspeaker which is designed to be mechanically damped will not give an improvement, although it may not make it a lot worse if the mechanical damping is exceptionally well done.

Some loudspeakers (pressure horn drivers) are both electrically and acoustically damped. The electrical damping is often unintentionally reduced because they are used on the ends of long high-impedance lines, but there are so many other problems associated with the horn loading that the presence or absence of electrical damping is rarely significant.

*** *** This is utter nonsense. Motional impedances are not generated by movement and do not have any effect on current, they are inherent mathematical properties. It sounds as though the authors are confused about how back-EMF works and do not have a clear grasp of the meaning of the word 'impedance'.

Did nobody challenge this paper? (...and if they did, why is it still being quoted?)

The result of these heating effects is a slow change in the sensitivity of the loudspeaker, they do not cause waveform distortion.

What the authors do not say is that as the voice coil heats up, the power delivered by a current-controlled amplifier *increases*, so there is a similar but opposite effect. The easy answer is to use a more efficient speaker or a larger one for the same power or just turn down

material.

--
~ Adrian Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk

the

year: 2012:

No. Current driven is all full of bad pseudoscience. Make no mistake though, dynamic coil speakers are current responding. Stiff voltage drive makes the speaker driver and enclosure physical resonance largely self canceling, which explains why it is so popular.

?-)

Hi Joseph

Some reading for you:

Current driving:

Quote: "... Frequency responses, at 1 meter with sinusoidal signal. In theory, we will expect to find in the response of the system, current-driven, the same 3 peaks of the impedance at low frequency; the entity is instead very lower. The peaks appear also in the measure of the system when is voltage driven. Comparing the two frequency responses, one can note that the first and the third peak have substantially the same entity in the two cases, while the central one is around 4 dB more pronounced in the case of current driving. In substance, there is not great difference; if the measure instead than at

1 meter were taken at 3 meters (that is, in typical listening conditions), the two curves at low frequency would be substantially identical. Things are different at high frequency, where the difference is of 10 dB: whereas the response begins to lower because of the inertia, with the current driving we obtain a kind of automatic equalization, with consequent notable extension of the operating limits. Differently from what could be thought, therefore, in the examined case (dynamic woofer characterized from notable variations of impedance at low frequency) the alterations in frequency dominion interest more the middle-high range that the low one: [] *generally, the alterations in low frequency are lower than those due to a different room positioning.* ... The system, if current-driven, has a much better impulse response: impulse is narrow, is more linear and, above all, has a shorter decay. The woofer get faster (it seems like a tweeter); all this with damping factor zero. ... The loudpseaker has some irregularity in the 3 - 5 kHz region; the low extension is 50 Hz, whereas inertia not allows a complete response at higher frequencies (the speaker has a whizzer, but the moving mass is around 13 grams). When current driven, the speaker become a full range, with 20 kHz well aligned. ..."

October 22, 2013, Loudspeaker operation: The superiority of current drive over voltage drive:

Quote: "... This force, then, determines the acceleration (A) of the diaphragm, which in the main operation area (the mass-controlled region) is got from the Newtonian law F = mA. The radiated pressure, in turn, follows the instantaneous acceleration and not the instantaneous displacement, as many mistakenly imagine. ... There cannot be found any scientifically valid reasons that justify the adoption of voltage as the control quantity - it is only due to the historical legacy originated almost a century ago, most likely by cheapness and simplicity; the quality and physical soundness of operation have not been considerations in this choice. Engineers are also more accustomed to identifying electrical signals as voltages rather than currents. ..."

Glenn

Hi Joseph and others

How do you drive an electrostatic loudspeaker? Voltage driven of cause:

Quote: "... As a result a uniform electrostatic field proportional to the audio signal is produced between both grids. This causes a force to be exerted on the charged diaphragm, and its resulting movement drives the air on either side of it. ..."

.

How do you drive an electrodynamic loudspeaker? Current driven of cause:

Quote: "... By driving a current through the voice coil, a magnetic field is produced. This magnetic field causes the voice coil to react to the magnetic field from a permanent magnet fixed to the speaker's frame, thereby moving the cone of the speaker. By applying an audio waveform to the voice coil, the cone will reproduce the sound pressure waves, corresponding to the original input signal. ..."

Glenn

Just to stick my oar in, one more time: if you want to damp series resonances, current mode does that. If you want to damp parallel resonances, voltage mode does that. If your speaker is really resistive (and mainly, they are), both offer good rendition of sound: after all, a current into a resistance IS a voltage, and a voltage across a resistor IS a current. If you want to damp a bunch of unknown resonances, why not use a resistance in the same range as the speaker impedance? We don't NEED critical control of damping, our ears have been hearing resonances all our lives, including as part of music!

Verbum sapiente.

If you want to learn some basic facts about this, read "Transients and Loudspeaker Damping" by J. Moir. (Wireless World, May 1950 pp.166-170) and "Output Impedance Control" Letters to the Editor by Thomas Roddam and Peter J. Baxandall ( Wireless World, April 1950 pp.155-156 ). That shows how long ago this current-drive nonsense was totally disproved - the physics of magnetism and electricity hasn't magically changed since then.

The accurate measurement and informed reasoning of real engineers like Moir, Roddam and Baxandall carries far more weight than all the pseudo-scientific gobbledeygook spouted by the gurus of audiophoolery.

--
~ Adrian Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk

If you want to listen to loudspeakers, current drive them; I prefer to listen to the music without the colourations of the loudspeaker and cabinet, so I voltage drive mine.

I shall no doubt be able to recognise you at a concert - you will be the one with sea-shells strapped over your ears.

--
~ Adrian Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.