Speaker "Speed"

[audiofooled]

I'm sorry but I have to ask what is the discussion about?

If we talk about pressure, then radiation impedance should be accounted for. For example, in an anechoic chamber impedance that the driver sees would be mass-like, where flat acceleration would then result in flat pressure.

In rooms we get into a much more complex situation as far as phase relationships between acceleration, velocity and displacement in that measuring the pressure at one point is insufficient, especially in low frequencies.

 

[Tell]

PLUS the driver phase which is what you are not showing. Do the same simulation and use LINFIR you can see the effect of the driver phase and crossovers phase and play with these parameters and watch the resulting step response. You can also se how using an FIR filter to flatten the phase response affects the impulse response.

And then as always is the question about audibility

Personally I'd say that a speakers "speed" is more or less about frequency response, the higher the frequency the "faster" a sine wave is.

 

[Skyra]

Driver mass (both low and high freq.), driver Qts, and transient response contribute more to subjective "speed" (attack and decay) than wide frequency response. At least this is what I can conclude from many years of building and listening loudspeakers.

 

[NTK]

If big woofer is slow, does that mean JBL's new 4369, 2-way with a 15 inch woofer (i.e. big, heavy cone), is never going to give "fast" bass?

 

[Philbo King]

Isn’t group delay the time it takes to start playing (“lag”), not a measure of how it plays it for (“hang time”)?

Group delay generally refers to delay differences across frequency. Not absolute delays.

 

[Skyra]

The lowest moving mass for a 15" woofer is around 70 grams. To get this mass moving requires a considerable electromotoric force AND time. Just check out the transient response in the availble speaker measurements on different sites and you will see. There are many things and parameters you can play around in driver design, but you cannot trick or ignore inertia.

 

[DavidEdwinAston]

Apologies in advance if this turns out to be a silly question.

Are there any metrics for the transient response or "speed" of a speaker? Subjectively, certain ribbon speakers I've heard have reproduced cymbals and strings with a faster attack than otherwise comparable tweeters.

I've seen it being described on other forums as the ability to accurately follow a square wave, but I've no idea if this is an accurate definition. I'm also not sure if the relevant metrics are already present in Amir's measurements.

I must ask, have you read Piranesi?

 

[voodooless]

Just check out the transient response in the availble speaker measurements on different sites and you will see

Compared to what? A 15” woofer will have a totally different bandwidth vs a small woofer. Obviously that will yield a different transient response.

 

[Waveform Fidelity]

Compared to what? A 15” woofer will have a totally different bandwidth vs a small woofer. Obviously that will yield a different transient response.

What is your reasoning that a small woofer and big woofer can’t have the same frequency response?

 

[voodooless]

What is your reasoning that a small woofer and big woofer can’t have the same frequency response?

They can, but that is pretty unusual. You can EQ them to be equal. Then compare the transient response. That would be fair.

 

[antcollinet]

Lets not forget that frequency/phase response and transient response are one and the same thing. One can always be derived from the other.

 

[bmc0]

To get this mass moving requires a considerable electromotoric force AND time.

If we define "speed" as "rise time of the acoustical step response", mass has no effect. All else equal, increasing moving mass will do three things: 1) reduce passband sensitivity, 2) decrease bass resonance frequency (Fs), and 3) increase bass resonance Q-factor (Qts). Alternatively, increasing suspension compliance (Cms) and reducing force factor (Bl) will give exactly the same result.

 

[Waveform Fidelity]

They can, but that is pretty unusual. You can EQ them to be equal. Then compare the transient response. That would be fair.

So I am curious to what you meant in your earlier post about big and small woofers have totally different bandwidths? Thats suggesting that diaphragm diameter, somehow affects the bandwidth/frequency response - clearly this cannot be because a headphone diaphragm is typically around an inch, but it still can produce SPL down to very low frequencies.

Here is the equation for SPL assuming a rigid piston. I invite you to study this and ask clarifying questions if needed. Just look at the constants in the left part of the equation.

 

[voodooless]

So I am curious to what you meant in your earlier post about big and small woofers have totally different bandwidths? Thats suggesting that diaphragm diameter, somehow affects the bandwidth/frequency response - clearly this cannot be because a headphone diaphragm is typically around an inch, but it still can produce SPL down to very low frequencies.

Here is the equation for SPL assuming a rigid piston. I invite you to study this and ask clarifying questions if needed. Just look at the constants in the left part of the equation.View attachment 532708

Generally, it’s a mix of very many factors. Large drivers have large voice coils. High frequency extension is naturally limited by inductance. Never mind that such a driver will beam a lot.

As to headphone drivers: great, use those for your next subwoofer… see how well that works…

 

[antcollinet]

clearly this cannot be because a headphone diaphragm is typically around an inch, but it still can produce SPL down to very low frequencies.

Perhaps consider the SPL needed at those low frequencies at a listening distance of 3m compared to perhaps 1cm. I suspect you would struggle to hear - say - 30hz from a headphone at 3m.

Or say filling a space of 75m^3 with those bass frequencies compared with about 9cm^3 (A factor of over 8 miliion)

You need to consider not only the frequency range but also the actual SPL that can be developed by the driver over that frequency range. There is no replacement for displacement.

 

[Holmz]

The lowest moving mass for a 15" woofer is around 70 grams. To get this mass moving requires a considerable electromotoric force AND time. Just check out the transient response in the availble speaker measurements on different sites and you will see. There are many things and parameters you can play around in driver design, but you cannot trick or ignore inertia.

Where are those links?

 

[Holmz]

So I am curious to what you meant in your earlier post about big and small woofers have totally different bandwidths? Thats suggesting that diaphragm diameter, somehow affects the bandwidth/frequency response - clearly this cannot be because a headphone diaphragm is typically around an inch, but it still can produce SPL down to very low frequencies.

Here is the equation for SPL assuming a rigid piston. I invite you to study this and ask clarifying questions if needed. Just look at the constants in the left part of the equation.View attachment 532708

I’ll suggest that you look at post #67 and let us know if there are differences between the steady-state equation you show and the post on acceleration.

 

[Waveform Fidelity]

Both are correct

 

[Holmz]

Both are correct

That’s true.
But here the person says “force and time”:

The lowest moving mass for a 15" woofer is around 70 grams. To get this mass moving requires a considerable electromotoric force AND time. Just check out the transient response in the availble speaker measurements on different sites and you will see. There are many things and parameters you can play around in driver design, but you cannot trick or ignore inertia.

There is no time involved with acceleration, assuming that we ignore inductance.
As soon as there is motor force, then there is instant acceleration.

And the acceleration produces the pressure.

That Rayleigh derived equation sort of obfuscates what is happening… especially with the wavenumber thrown in.

 

[NTK]

So I am curious to what you meant in your earlier post about big and small woofers have totally different bandwidths? Thats suggesting that diaphragm diameter, somehow affects the bandwidth/frequency response - clearly this cannot be because a headphone diaphragm is typically around an inch, but it still can produce SPL down to very low frequencies.

Here is the equation for SPL assuming a rigid piston. I invite you to study this and ask clarifying questions if needed. Just look at the constants in the left part of the equation.View attachment 532708

Unfortunately, you're betrayed by AI. You can run a dimension analysis, without needing anything knowledge of acoustics, and see that AI was giving you wrong info.
The dimension (unit) of the quantity inside the log₁₀ operation must be unit-less (as it must be a ratio). But AI gave you a formula that resulted in a dimension of L (length), and therefore oops.

The correct formula is this. You can substitute U₀ = π a² v⟂ (volume velocity = piston area × velocity normal to surface) into the correct one and find out that the AI formula had an extra "a" (piston radius) in the numerator and the 4π below should be 2π.