I would bet a pint, as that is my maximum wager, you are correct that a standard bridge with snubbers, proper filtering, and proper dress, is just as good and $10 cheaper. I have seen only subjective babble and it is a simple thing to test. I put 4X the reserve as well as lower esr caps in the 120, so I thought it prudent to put in a larger bridge anyway, so why not? If I see a difference in the level and quantity of line harmonics in the output, we will know. If I don't, we will know. The wiring is not bad, but not optimum either. So second question, it is a worthwhile band-aid for an existing unit?
With a scope, look at the amp input and the output from the mic.
Feed a steady 4K tone.
With a delay, you can basically overlay the traces.
Now, feed a computer generated 10 cycle pulse that starts at zero crossing.
Capture the result.
You will see the acoustic trace start later and basically look like it is a bit behind the drive. The first half wave is looks compressed in time and amplitude as it is told to reverse before it got going. Undersoot and slow. Within a few cycles, they are in sync. Of course, as you have the mass moving and all the spring-damping effects in place. This makes sense. BUT, how much is effected by different amps is what I noticed.
I am going to try to reproduce this so I can publish a picture. It was easiest to see on my analog scope, but no way to capture. I got it on Zalescope but it was not clear.
I also did some tests with a half wave and found how the driver behaved varied with different amps. My thinking was these are contrived and not realistic to music, but they are a dynamic test. It is a test that showed a difference. Relevant? I can't say as I have not done enough to correlate with my wife's super ears.
Off the wall thought. Could the delay be related to the slinky delay? This has been studied recently and confirmed as being caused by traveling waves within the spring. Probably not but who knows.
Thanks for the details, TVR. It just sounds like you're talking about phase, but I'd like to see what you've got. 10Hz is pretty low.
If you can measure at the amp output terminals (with speaker attached) it might be easier to see the effect than with a mic. And that would allow you to test into a resistive load, as well. If you can show that this difference corresponds to some of your subjective evaluations of the amps, that's worth something.
If you can measure at the amp output terminals (with speaker attached) it might be easier to see the effect than with a mic. And that would allow you to test into a resistive load, as well. If you can show that this difference corresponds to some of your subjective evaluations of the amps, that's worth something.
I don't get a broken penny for what is going on outside of my wires. Even if devils jump on that wires, I do not care, if what I get after power supply is pristine clean (relatively, of course!)
However, if somebody connects ground wire of a mic pre directly to the ground wire of the bridge it means he or she better go to sell used cars.
Wavebourn, your self-assurance will sometime catch up with you. I felt the same way, more than 20 years ago about high speed diodes, until I changed to them, though the efforts of a friend and future business partner, and then I MEASURED with a current probe and I KNEW I had overlooked something. It was embarrassing. It is now my D mod for the Vendetta Research. I don't like to do it, it is too difficult for myself to do, and I have to bring in a tech to do it, but I do offer it as a service in order to update 20 year old equipment, on occasion.
I have found that I don't know 'everything', that I will never know 'everything', and that is why I like to correspond with Russians, E-Germans, etc. because their background is DIFFERENT from mine and sometimes I learn something new, even while approaching 70 years of age.
I have found that I don't know 'everything', that I will never know 'everything', and that is why I like to correspond with Russians, E-Germans, etc. because their background is DIFFERENT from mine and sometimes I learn something new, even while approaching 70 years of age.
John;
Acceptance that I use models of reality that do work, but have no clue about reality itself how it works, looks and is organized, helps me to learn something new no matter how old I am and what others think about my knowledge, and where that models come to me from.
Once again, I don't care what currents flow outside of my loop, if that loop is connected with mine in the single point only. In order for current to flow 2 minimum points are required. If to deny that, the world as we know it does not exist anymore, and we can do nothing.
In order to be able to do something real I have to stick with models that work and leave alone musings that do not.
Acceptance that I use models of reality that do work, but have no clue about reality itself how it works, looks and is organized, helps me to learn something new no matter how old I am and what others think about my knowledge, and where that models come to me from.
Once again, I don't care what currents flow outside of my loop, if that loop is connected with mine in the single point only. In order for current to flow 2 minimum points are required. If to deny that, the world as we know it does not exist anymore, and we can do nothing.
In order to be able to do something real I have to stick with models that work and leave alone musings that do not.
I have to question the whole notion of a "Sound Quality Index", if by that you mean taking a variety of different types of measurements, combining them together with some weighting or algorithm, and then producing a single scalar value like a 0 to 100 scale covering "awful" to "outstanding".
The problem with this is that it assumes that different types of flaws can counter balance each other, when they can't. For example does a more extended bass response (which is a desirable trait on its own) make up for a harsh resonance in the midrange ? Any sort of weighted Sound Quality Index would imply yes, but I say no.
Does an ultra flat frequency response make up for a lack of dynamic range ? Not in my opinion. Conversely does an extremely good dynamic range make up for an extremely non flat frequency response ? No, not in my opinion.
I don't see how its possible to have a single scalar value like a "Sound Quality Index" to rank speakers with various differing deficiencies against one another, without of necessity incorporating the individual listeners preferences.
By preferences I mean the relative importance you give to various aspects of performance. Some people might place more emphasis on tonal accuracy, some on dynamic performance, some frequency extension, and so on. Based on these differing priorities the same set of speakers may be ranked differently by differing listeners, because you're comparing Apples to Oranges. There isn't necessarily a clear order of precedence.
Some of the tests performed by Toole do seem to suggest that there is a universal ranking order for speakers regardless of listener preference based on a fairly limited set of measurements, but as far as I can see, radically different topologies of speakers were not compared in his tests, nearly all being typical 2/3 way cone and dome designs, with only one token electrostat dipole, no horns, either CD or non CD, and no line arrays either, let alone other more exotic topologies.
From this the only conclusion I can draw is that speakers of a similar overall design topology can perhaps be ranked in linear preference order (using a single scalar value) but that says nothing about comparing radically different topologies, so I think its dangerous to over-generalize his conclusions beyond the limited topologies tested. (EG cone+dome designs will all tend to have the same sort of failings to greater or lesser degrees)
As an analogy, how would you go about defining a "Picture Quality Index" for the picture on Televisions ? Unlike hearing, what we can see is a lot better defined and understood, and a lot less subjective than hearing.
There are a ton of measurements that can be taken and there are a ton of different ways in which pictures can be deficient. For example:
Convergence errors, geometric distortions (barrel distortion etc) grey scale tracking, black level, banding on gradients, colour balance, (highlights and lowlights) update rate/ghosting, resolution and sharpness, motion compensation processing, noise, halo effects, the list is nearly endless. Some screen technologies suffer from some problems, some from others, just like certain speaker topologies tend to suffer more from certain problems.
All these things can be measured fairly easily with the right tools, most can be seen individually with the naked eye with the right test patterns, they are all well understood, but could you measure them all numerically (without any visual inspection) and calculate a single quality index figure that would agree with the subjective ranking of TV sets by individuals ? Maybe, maybe not, but should we even be trying ?
Clearly in audio we still don't even really know what measurements correspond well with what we hear, beyond the obvious ones like frequency response, which are important, but don't tell the full story.
I'm all for finding out which measurements do matter and which don't, and having a rough idea of their importance, but I don't see any particular benefit from trying to merge a set of measurements into a "Sound Quality Index", or even that it's possible when you're comparing such radically different potential flaws to each other.
A Sound Quality Index rating doesn't help you improve the design of a speaker, only individual measurements will do that. Lets figure out what those measurements are...
PS yes I know much of this thread is focused on amplifiers not speakers, but speakers are a much more 3 dimensional problem than amplifiers, with far more potential for complex flaws, especially considering they are transducers whose input and output are not even in the same domain.
At lest with an amplifier you have voltage in and voltage out, two quantities that are directly comparable, with scaling. You have no such luxury with speakers.
A 10 cycle pulse of 4kHz, starting from zero, has a lot of transient high frequency components - not just 4kHz. Reproduction will depend to some extent on the HF rolloff of the amp, so it is possible that this is some or most of what you are seeing. If this correlates with perceived audio quality on music then it could be interesting.
Also, HF rolloff may have two components: voltage gain, and output impedance. To what extent is your tweeter sensitive to driving impedance?
Also, HF rolloff may have two components: voltage gain, and output impedance. To what extent is your tweeter sensitive to driving impedance?
As mentioned in my previous post, I think trying to find a weighting to provide a single figure result, even if we knew which measurements to weigh, is futile.
Bingo. That's what I do too
Let's call it "willing suspension of disbelief". Your rational mind knows the sound is not real, your eyes confirm its not (clearly you're in a room with speakers, not somewhere else) and yet when you close your eyes, you have to work hard to convince yourself that it's not real. That's when you know you're getting close.
Sometimes the set-up that produces this result measures "well" with conventional measurements, sometimes it doesn't. This alone suggests that we still don't know everything that matters in the measurements, or we misunderstand something about our hearing perceptual mechanisms.
I think its one of those things that can happen as a Eureka moment. Not many speakers will convince you of the realness of the sound, until you have heard some that do, you will always assign "speaker sound" to speakers, and have no frame of reference to what is possible beyond that.However, such measurements require some calibration. Untrained people eager to judge experienced designers can't use them.
As soon as you hear a system that is convincingly real with your eyes closed you have a "Eureka!" moment where you see what is possible, what you previously thought was impossible, and you then spend the next xx years trying to understand how it happened, and define (unsuccessfully) which measurements led to that result...
Once heard its hard to un-hear it as well, which leads to being disappointed with anything less than perfection, a problem no doubt many of us face when we're now disappointed in the sound of a system that many years ago we might have thought was pretty good, simply because our expectations have been raised so high.
Last edited:
Who is after a single figure? My guess is that as a minimum you would need four or five figures just to cover the basics of what we know now: harmonics, IM (two measures of non-linearity, perhaps with both as function of frequency), LF/HF rolloff (or, equivalently, bandwidth and LF/HF balance), noise. Let's assume we can choose a set of figures which capture what matters - we would still find that different people attach different importance to each of them, partly through taste and partly through environment. That is not a reason not to look for the figures, though.DBMandrake said:
People like to knock THD etc. but they need to remember that originally nobody knew what mattered, so careful experiments were conducted on distortion, frequency response etc. We need better experiments, not attempts at 'proof by assertion' from either side of the debate.
Pano, with his "Sound Quality Index" ?
Toole, with his speaker ranking studies ?
Note: not a single measurement, but a single aggregate figure of merit derived from a group of measurements. That's what I'm saying is futile, because I think you simply can't boil down so many competing and largely orthogonal factors into a simple scalar figure of merit, especially if personal preference is indeed a factor.
And there's not much reason to, unless your goal is to replace controlled listening tests with measurements to see how speakers rank against each other in listener preference. A single boiled down figure of merit gives no guidance into what needs improving in each speaker, so doesn't help the designer.
I'm 100% with you there, you're arguing the same side of the argument as I did in my longer post...?
I want to find those things that most matter too, however I don't see any point in a single figure of merit for ranking purposes. Keep the handful of important measurements (whatever they are) separate.People knock THD because it doesn't correspond well, if at all, with what we hear. Yes gross distortion like clipping or a voice coil going out of its gap is audible but below gross levels its very unclear what's going on.
I used to believe strongly in trying to get vanishingly low levels of distortion at mid/high frequencies in particular, but in recent times I've been having a "crisis of faith" in this area where experimental measurements and listening tests keep pointing in the direction that once below a modest threshold, the audible difference between low and ultra low distortion on music is nill. (At least for low orders)
Of course Earl Geddes has been beating this drum for years, somewhat on his own, and I have reluctantly come to the conclusion that he may just have a point after all, although I perhaps wouldn't go quite as far as he does.
Rather than trying to achieve ultra-low distortion at modest SPL it seems to be more important to maintain modest distortion levels to very high SPL levels - eg a large well specced driver sounds good not because distortion may be ultra low at modest levels, but because its distortion is still only moderate at much higher than necessary levels.
THD also doesn't take into account what order products are present or in what proportion, and its clear that this relationship does hugely affect how audible distortion is. For this reason alone THD is meaningless. At the very least we need to talk in terms of how far down each individual distortion product is, preferably in dB rather than percent.
Distortion matters, but probably not as much as we think and not in the ways we've traditionally thought about it, and THD as a figure of merit is pretty much meaningless due to the lack of information contained within it.
Last edited:
Hi Simon,
Actually I was the Technical Lead and electron optic designer for the 32V HDTV real flat CRT for Philips in 1998-2000. We did have two quality metrics QK(color) and Qr(rastor) In simulations ( a 3D Greens function of the electron magnetic field and its interaction with the RGB electron streams) we spent months balancing Qk against Qr we then moved these design to prototypes for another 4 months of development . We had minimum accptable values for both Q's and in the end without simulation's and metrics the dipole through 18 pole analysis would have been impossible.
Yes othere are other metrics as you mentioned, BTW we also had a non quantifiable element, we called it "sparkle" similar to "live" in audio , but I see nothing wrong with a couple of q's e.g
Q speaker & source load ( ability to handle reactive loads without delay or distortion and handle phono->Digital loads)
Ql(live) ability to amplfy and "maintain" or "enhance" the live experience, QLoud and Q finesse ( perfect RIAA, dynamic Loudness)
and finally most important QWAF (wife/partner acceptance factor)
Lou
Folks,
One issue is that even with weighting applied and all we can mostly only make negative determinations.
For example we can make an aggregate distortion metric that allows us to class the effect of the distortion as "no effect", "small effect, not objectionable", "small effect objectionable" and so on onto major effects.
So we can determine when distortion will influence what is heard and when it will become objectionable.
Note, this is not a positive determination as in "number so and so on this index guarantees good sound".
As much of the research (naturally) focuses on determining what kind of degradation is tolerable (perceptual coding research is a goldmine of information on that topic) it does not actively pursue anything that is deliberately positive.
I know for example that using very minor manipulations of frequency response I can make a system sound ridiculously spacious, but distant, equally I can get an effect that creates more "presence" and many others, by smal frequency response manipulations.
I do know that a lot of 2nd HD (usually more than I allow my commercial circuits) can also enhance the sense of spaciousness and of detail (likely the "lost fundamental" effect comes to play).
So, if I can take some modest liberties (within the boundaries of what is not perceived as objectionable) with traditional measurements I can create a sound that is immensely appealing and enjoyable. The "UltraFi"crowd (read Horn Speakers, SE Amp's, Vinyl etc.) is majorly on this kick. Much of their gear measures revoltingly bad by traditional standards, yet it makes musik come a-live like little else in the mainstream of HiFi and High End can...
So, where does this leave us?
Is the extant approach to characterising audio equipment by certain measurements even defensible or sensible? Or is it just Captain Slater (Witchlocator) continuing to mumble "But we have this here ducking stool...".
Ciao T
One issue is that even with weighting applied and all we can mostly only make negative determinations.
For example we can make an aggregate distortion metric that allows us to class the effect of the distortion as "no effect", "small effect, not objectionable", "small effect objectionable" and so on onto major effects.
So we can determine when distortion will influence what is heard and when it will become objectionable.
Note, this is not a positive determination as in "number so and so on this index guarantees good sound".
As much of the research (naturally) focuses on determining what kind of degradation is tolerable (perceptual coding research is a goldmine of information on that topic) it does not actively pursue anything that is deliberately positive.
I know for example that using very minor manipulations of frequency response I can make a system sound ridiculously spacious, but distant, equally I can get an effect that creates more "presence" and many others, by smal frequency response manipulations.
I do know that a lot of 2nd HD (usually more than I allow my commercial circuits) can also enhance the sense of spaciousness and of detail (likely the "lost fundamental" effect comes to play).
So, if I can take some modest liberties (within the boundaries of what is not perceived as objectionable) with traditional measurements I can create a sound that is immensely appealing and enjoyable. The "UltraFi"crowd (read Horn Speakers, SE Amp's, Vinyl etc.) is majorly on this kick. Much of their gear measures revoltingly bad by traditional standards, yet it makes musik come a-live like little else in the mainstream of HiFi and High End can...
So, where does this leave us?
Is the extant approach to characterising audio equipment by certain measurements even defensible or sensible? Or is it just Captain Slater (Witchlocator) continuing to mumble "But we have this here ducking stool...".
Ciao T
Here is a thought..
Can a TV produce a picture that cannot be distinguished from reality...
Can a HIFI produce a sound stage that cannot be.....
What are the limiting factors....
The limiting factors are distortion....<<<<not true to reality
How do you measure the difference....forget everything else...
If it can be measured it can be controlled?
Regards
M. Gregg
Last edited:
here is another thought..
If someone plays a trumpet in a room it will sound like a trumpet..
If they play in a different room it will sound like a trumpet
Take a HIFI to a different room it sounds like a HIFI..is the soundstage the same?
What makes a trumpet sound like a trumpet in any location?
Regards
M. Gregg
If someone plays a trumpet in a room it will sound like a trumpet..
If they play in a different room it will sound like a trumpet
Take a HIFI to a different room it sounds like a HIFI..is the soundstage the same?
What makes a trumpet sound like a trumpet in any location?
Regards
M. Gregg
Metrics get more complicated when the possibility of making something 'better' than reality is included, whether brighter-than-life TV pictures or 'appealing and enjoyable' sound. If 0 is perfection, 1 is barely discernible difference, 2 is tolerable, and 3 is horrid some people may prefer 1.2 - especially if they rarely hear live music. For example, some brass instruments can make quite an unpleasant noise when played loudly - hear it at home and you suspect a tweeter fault, but in the concert hall it is reality.
- Status
- Not open for further replies.