Fast/Slow Speaker Article

[geolemon]

where should I start learning to get that base. [?]

Seriously - I'd spend some time pondering, rather than looking.

If you understand how a speaker works - it's an electromagnetic motor pushing a cone in and out.

Apply DC to the speaker, and it either moves out, OR in, and stays there until the DC is removed. How far out it moves depends on the amplitude (read: voltage). Well, OK, the suspension is going to stop it too.

Apply AC to the speaker, and the cone oscillates in and out, cycling at exactly the frequency of the AC signal. Music is all AC. A sine-wave test-tone is the simplest AC signal (your home electricity is 60hz AC), a complex waveform is simply... more complex, the additive average of numerous frequencies together.

The cone motion follows the shape of the waveform though - a sine wave, you can follow the cone out, as the waveform moves up. When the waveform moves down, you could witness the cone moving back in - passing "at rest" and heading towards rearward excursion until peaking at the bottom of the sine wave, where it begins to move back out. Simple, right?

The amplitude here is also - voltage. Higher voltage (read: power) = higher excursion, = louder music.

Now go ponder those questions from my post to you before.
The place to look is inside your own head - do you have an understanding yourself? I bet you can figure it out. And then you will, even if you don't now.

[GlassWolf]

and while you contemplate that, I'll be in geolemon's garage, goin thru his stuffs, lookin for a statement 15 prototype laying around unguarded
hahaha

[thnking]

I agree - but I think "attack" is where people get confused. ]Attack [/B]- the rise time of the speaker - and in it's most extreme form (and only in that extreme form), that would be the sudden presence of a waveform, requiring the speaker to rise to response at a given amplitude.
Ideally, the cone motion would follow the waveform exactly - and as such, the waveform will NEVER make the speaker move any faster than the highest frequency component of that waveform - and the highest frequency the speaker is capable of playing well is essentially dependent on the inductance of the speaker. (phew)
So, even in an idealistic sense, inductance DOES determine the "attack" (speed) of the speaker in this way.

Really though high frequency response is limited by acoustic resistance, excursion, and inductance…they all are limiting actual reaction speed of the woofer

However, there is an amplitude component to consider:
If you suddenly hit the speaker with a 100hz waveform, would the speaker actually reach full excursion right from cycle #1 [of those 100 cycles-per-second]? Or are there a few cycles worth of "rise time" before the cone excursion matches the amplitude of the waveform? There are some dynamics related to standard physics, such as momentum and inertia. But realistically, such a rise time is going to be inaudible, because of how many cycles really are happening "per second", and how few it takes to 'rise' - if there is any rise time. ]
But over damping can make an audible difference with the attack of the transient –of course depending on the amount of damping and type of signal.

The impulse response test of a speaker is interesting, both in the context of "attack" an "sustain". The speaker is simply hit with a DC pulse which is then sustained, and the cone motion is monitored. The speaker will rise at something less than "perfectly vertical" (the waveform does rise exactly vertical), and then does tend to overshoot that maximum peak and oscillate a bit. The 'rise' response is credited to the inductance of the speaker. The overhang/oscillation is both motor and suspension, and IMO doesn't really represent a scenario encountered with the speaker playing music - if the speaker is playing music, those are AC signals, and the speaker naturally will be oscillating - across the entire excursion range of the speaker. But it's a good segue into...
Sustain - I really don't think this is much of an issue. A Boss coaxial will "sustain" just as well as a Focal Utopia, once it's risen and is playing a sustained tone (That's NOT to say the Focal won't sound better ).
Decay - measured as per the waterfall plot, and here's where I believe oscillation matters. The speaker is played, and signal removed, to learn where the speaker fails to control its natural oscillations well enough. It's a very interesting plot, and one measurement where the speaker's natural resonance is it's own worst enemy.
Release - ...wouldn't really seem to be a function of the speaker, but rather the electronics. ]
Energy is being constantly changed, stored, opposed, and transferred through all of this F=MA stuff. These forces act to alter the entire transient envelope, ADSR. So I consider them all important.

"Static impedance" - ie. inertia (more recognizable physics term)

This is really the electrical impedance if the speaker was “static”. It has an angular frequency component.

"Motional impedance" - ie. momentum (ditto)

This includes Back EMF, inertia, suspension stiffness, and motional damping.

"External impedance (ie. air loading)" - by "external" you mean to the speaker, not "the outside of the box".

I mean the forces generated by the pressure developed when the diaphragm moves.

With most people, it's the impact of the bass - which is often the midbass component, not even played (I hope!) by the subwoofer.
Take away or EQ down the midbass in the car, and people are often tremendously disappointed, even describing the sound as slow and muddy.
Conversely, take a good system (with good midbass) and turn off the sub, and people describe the sound as having "great impact" - but "doesn't hit the low stuff".
It's interesting - but as they say... perception IS reality. :happy055:

I totally agree.