Would ANC Work Better With 2 Separate Drivers? - Page 2

Quote:

Originally Posted by khaos974 

The signal isn't really more complex, otherwise white noise would be irreproducible by speakers, it's a combination of every single frequency given a equal amplitude.

 

 

Well, I mean it still produces a decent approximation of it, but it doesn't do it perfectly. I'd be surprised if you could pick out the individual frequencies from white noise, which is essentially the same as what I'm describing. And the way you described white noise is actually physically impossible, as that would require an infinite number of different frequencies, etc...

"An infinite-bandwidth white noise signal is a purely theoretical construction. The bandwidth of white noise is limited in practice by the mechanism of noise generation, by the transmission medium and by finite observation capabilities." It's from Wikipedia sure, but there you are.

So let's say you had some sort of hearing filter, that allowed you to only hear certain frequencies at a given time, kind of like a high-/low pass filter on your ears or something. So If i played a white noise sample for you, I'm pretty sure that picking out just that frequency from white noise would give you a less-accurate sound reproduction than if you had just played that pure tone. Likewise, if you were to play 2 different songs over each other through the same speaker, and were able to completely ignore the other one, it would still sound worse than if you just played that one song by itself, because the driver can't keep up. That's essentially what I'm saying.

Quote:

Originally Posted by khaos974 

Let me quote you what I think speed is for a driver:

 

Thus as long as the ANC signal rests within the frequency limits of the driver, that is to say in most cases 20 to 20,000 Hz, it doesn't not impact the reproduction, adding an ANC signal is not different than adding a drum to a band, or adding a base beat to a song.

 

Well, while we're quoting other threads... Take a look here: http://www.head-fi.org/t/579137/good-treble-detailed-no-really

Bear with it, it might not seem related at first, but it gets to the point later on. Basically, we're discussing how what is perceived as transient response and bass impact is actually affected by complex harmonic overtones that exist within what we hear as a drum impact and whatnot. This is mainly dependent on how accurately the driver can follow the waveform of the signal. The place where the driver would have the most trouble following the signal waveform would be in the case of areas with high frequency waves, or basically when it has to change directions very quickly. This is what affects its ability to produce those subtle little dips and peaks of a complex waveform. This is the reason why people like electrostatic drivers; since they're extremely light, it's easier for them to change directions, and they can do it much faster than a comparatively heavy dynamic driver. This is why they're perceived as being very "fast" and having good transient response. So here's where I challenge your fundamental assumptions on the relative speed of the driver. A very good example in that thread is the frequency graph Armaegis provided of a low cello note, but still had smaller waveforms in it. These overtones are what give the impression of timbre and allow us to identify different instruments based on how they sound; otherwise, they'd all sound like pure sine waves, and that's definitely not what music sounds like. And just think about it, if you try to play more and more different sounds through your headphones, each of the individual sounds gets muddled a little bit more, because the driver has trouble conforming to all those waves that keep getting added on top of the existing sound. In this case, the ANC adds another set of frequencies that makes the waveform that much more complex, and the driver has that much more trouble producing the combined sound. 

EDIT: I read the OP for your quote and I can tell you'll start talking about his rebuttal to electrostatic drivers, since I discussed that a little bit. However, before I talk about that, I'm confused as to his definition of a "transient response." First, he talks about transients in sine waves, which is fine, but what we hear as the transient response, i.e. bass impact, is never a pure square wave. In fact, transients are more like square waves, and as he admits later on, "If it went faster, there would be higher frequency harmonics - like in a square wave." Also, he makes no sense when he says "It's not like how we hear - the note doesn't just start and all of a sudden the transducer has to rapidly accelerate - it's no faster than the note at the same amplitude in steady state." That's exactly what a square wave is, and what gives you tight bass response, transients, etc, and if you read the rest of his post, he starts talking about the exact same thing that I am: that is, how driver speed, and how quickly the driver changes directions, are factors of how "fast" the driver is. And after this point, he's spot-on, in talking about how you can either increase the force or decrease the mass to get the same effect in acceleration. But if anything, this really contradicts the tone of the first half of his post, because he now admits that how fast the driver can move and change direction actually is important. I think his problem is that he doesn't have a good understanding of what transients are, and he's just misrepresenting how it factors into headphones. /rant

EDIT #2: Ok, I looked up this critical damping he was talking about, and I'll admit, he's not as off as I thought at first. What he says about damping is true to, that is, how quickly you can get the driver to stop moving, which is also a component of a transient. However, that's still a component of driver speed, and my point still stands.

EDIT #3: Also, just being able to produce a 20kHz sound doesn't mean you can control the driver accurately at that frequency. For example, pretty much every low-end earbud on the planet quotes a 20kHz upper limit, and even if they can produce some sort of 20kHz sound, it won't be controlled or clean. If we assume that you're right, and that you can reproduce anything within your frequency response range, we wouldn't need Head-Fi, because all the issues with sound quality could simply be fixed by damping the drivers on our $2 earbuds.

Originally Posted by khaos974 

 

That thread is full of misinformation and circular logic, what "good treble" is is never explained, it basically goes like details is good treble, good treble is when treble is reproduced faithfully, faithful means it doesn't erase the details, not erasing details is good, thus good treble is details.

 

 

The point everybody seems to miss is that no transient, regardless of how fast it goes needs a faster movement of the diaphagm than a full volume 20 kHz sin wave, and anything faster than that is inaudible. Those complex squiggly littles waves within the large large wave? those harmonics of the cello? hose of the cymbals, all are inferior to 20 kHz. As for change of orientation for the diaphragm, it never changes faster tahn when the diaphragm reverses it course at the summit of a 20 kHz sinwave either.

 

 

First, what kind of misinformation and circular logic? You're sounding like a politician here, giving me these claims, but not backing them up. If you clarify this, I'll be happy to discuss your issues with the thread. And did you not see the discussions we had about driver speed? That was like the main discussion and clarification of the thread, and we pretty much all came to an agreement at the end.

And the problem with transients is not the frequency response of the driver, it's how quickly it can get to that speed. Think of it like a car. Sure, you can probably get a sedan up to 90 mph, but it takes it a while to get to that speed. Compare that to a Ferrari, which can get up to that same speed many times faster. Sure, they both end up at the same speed, but one accelerates a heck of a lot faster than the other. Such is the case with driver speed. It doesn't matter if you get a 20kHz freq eventually, it's all about how quickly you can accelerate up to that speed. It's admittedly not the perfect example, but it gets the point across I think. And in fact, that's pretty much the whole point of that post you quoted: that driver speed is dependent on how quickly it can accelerate. And even if individual waves are each less than 20kHz, the way that the add to each other, i.e. if they're out of phase also creates changes and peaks that can all be around 20 kHz. If you driver can't accelerate well enough, it might gloss over some of those peaks, and then that's where you lose detail.

And just look at some square wave frequency response graphs, for an example of this. They're all fed the same perfect square wave with steep sides, but if you look, many of the phones perceived as "muddy" seem to have a fairly shallow slop on the side of the square, because they can't get their drivers to move fast enough. And notice that the more high-end you get, and you get to the summit-fi headphones that are all very fast and have excellent transients, you start to see very straight sides and they look a lot more like sine waves.

And again, remember that under your characterization of driver speed and whatnot, any cheap headphone with a 20-20,000 Hz quoted response could sound amazingly detailed with just the right damping.

Quote:

Originally Posted by khaos974 

You are strawmanning, first it's not easily to get a good flat 20-20,000 kHz range, especially since no one really agrees on what flat is, then you have to deal with distortion, where harmonic or IM, then you still have to ensure the phase response is correct, then you still have the nodes of the driver, the thermal aspects, and then you also have to deal with the consistency of the manufacturing process, lest you get differing left and right drivers...

 

That's quite different from simply getting the right damping, and even so the right damping isn't trivial to get.

Hmm... I guess I was oversimplifying the issue a bit too much, huh? I'll have to read up more on that. Regardless, I still stand by my assertion that playing the more complicated signal would be detrimental to the driver's ability to produce the sound. All those factors affect how fine a control you have on the driver, and that consequently has an effect on the sound. However, I now realize that I probably don't know nearly enough about this stuff for now, so I'll drop the issue ftm