Beyond the Ariel

[ScottG]

Originally posted by John_E_Janowitz



We are talking about "speed" and Bl/Mms ratio once again tells nothing. Testing shows that inductance increases the time to both positive and negative peaks. I don't see how this is irrelevant. Again look at the results in the paper. With double the mass, the impulse response occurs at the same time, meaning same speed. With 78% increase in inductance, it is shifted later in time. Clearly this tells which is more critical in terms of "speed".


John

Once again the subjective sense of "speed" under discussion is NOT with regard to how quickly the driver can oscillate (or by result, how high the freq. extension is near the average).

That Adire paper is not only useless in this instance, it actually is a disservice to the discussion. (..and one in which I've admonished the author for here in this forum.) The paper was specifically an attempt to say "Hey look here, our woofers can oscillate quickly thereby *proving* that our high mass high excursion low eff. subwoofers are "fast"!". Of course he knew fully well that what people were describing as "fast sound" had nothing to do with it's ability to oscillate quickly.

As for the rest - again, its a general guide to achieve specific subjective sound. In this respect:

A. you don't seem to recognize what people are describing when saying a driver sounds "fast" or "not".

B. you are arguing a topic that "A" you appear not to fully comprehend, and that you are arguing that a "guideline" is inaccurate because the underlying principal is incomplete at best - which is irrelevant. The guideline isn't there to say the guideline is correct, rather it's there to say you are more likely to achieve sound "x". (..fundamentally that's a rather substantial difference - think about it. )

[john k...]

Originally posted by gedlee


...I'd still claim that the impulse response has to change if the cone mass changes.

Hi Earl,

We basically agree here. Increasing mass has to change the drivers Fs and thus the impulse response, although it won't be seen in the initial rise, and is probably difficult to see in the impulse tail. However, there is also the possibility of a resonance at the high frequency cut off of the driver where the of the driver mass may resonate with the voice coil inductance. I don't know how significant this is, but in theory it is possible. This could be apparent in the initial rise of the impulse.

[gedlee]

Originally posted by ScottG
Still, it's always argued, and yes - the argument doesn't make any sense.

At last, a statement that I can agree with. It's not that I don't agree or disagree with the others, it's just that with terms like "speed" and "impact" - that clearly mean entirely different things to different people - whats being said doesn't make enough sense to agree or disagree with.

[soongsc]

Originally posted by John_E_Janowitz



The best way IMO to do this measurement is to take the same driver with and without the shorting ring. Take a TD15M for example. One driver with the copper sleeve and one without the copper sleeve. Matching Re to be within better than 1% tolerance between coils. Matching suspension so Fs is within 1% between both drivers. Check impulse response and you will see that the one without the shorting ring has delayed positive and negative peaks the same as shown in the other paper.

John

With and without copper sleve. Which one is better?

[john k...]

My take on this is the the idea of speed and impact as related to a driver are pretty much nonsense. Adding a series inductor is not the same as changing VC inductance. The series connection acts more like a shelving filter, lowering only the amplitude of the signal applied to the driver starting at about f = Rc/(Ls + Lc)/2/Pi where c = coil and s = series. But the effect is the same, increased group delay, attenuated high frequencies.

So what would the impulse look like if the woofer were low pass filtered as it would be in actual use? (rhetorical question) That is what is relevant. If the woofer is to be used only to 200 Hz or whatever, what matters is what the impulse of the filtered woofer looks like. That will be a function of the filtered response. If the filter is designed to a specific acoustic target, then any woofer with the same Fs and Q will have the same impulse when filtered to the same low pass acoustic target. So all that so called "speed" is irrelevant since it is an artifact of what the raw driver is doing above the corner of the LP filter. The woofer LP filter sets the "speed" of the impulse rise as used in a speaker.

It seems the audio will forever be a discipline where science is treated as the enemy rather that the path to progress.

[john k...]

Originally posted by John_E_Janowitz



The best way IMO to do this measurement is to take the same driver with and without the shorting ring. Take a TD15M for example. One driver with the copper sleeve and one without the copper sleeve. Matching Re to be within better than 1% tolerance between coils. Matching suspension so Fs is within 1% between both drivers. Check impulse response and you will see that the one without the shorting ring has delayed positive and negative peaks the same as shown in the other paper.

John

And if you check the frequency response you will see that the one w/o the shorting ring has the high frequency response rolled off sooner than the one with the ring. All this is saying is that "speed" = extended frequency response. I'm not at all concerned if a woofer goes out to 10 K Hz or 1 K Hz if it is to be used only below 500 Hz. That 500 Hz LP filter is going to set th "speed" of the woofer in the system.

[john k...]

Originally posted by soongsc

With and without copper sleve. Which one is better?

Put a 200 Hz LR4 LP filter on them both and look at it again.

[soongsc]

not exactly sure how to do that in SE.

[gedlee]

Originally posted by john k...
It seems the audio will forever be a discipline where science is treated as the enemy rather that the path to progress.

John, as much as we disagree, I can whole heartedly agree with you here. While we argue about the difference in mass between a proton and a nuetron these guys are arguing about if "the would is flat". "Speed" and "impact" - give me a break!

[serengetiplains]

Originally posted by gedlee


John, as much as we disagree, I can whole heartedly agree with you here. While we argue about the difference in mass between a proton and a nuetron these guys are arguing about if "the would is flat". "Speed" and "impact" - give me a break!

Science forever an enemy? I personally see a complex field of opinions on the usefulness of today's current crop of measurements and measuring tools, but rarely, if ever I should say, have I heard someone say science is forever an enemy (absolutely useless, presumably) to audio advance. Just being scientific about what I see and perceive ...