Speaker "Speed"

[Penelinfi]

And quick decay/low overhang

 

[mhardy6647]

I just measured my speakers for speed. 0km/h.

Relative to the earth's surface, to the sun, or to the center of the galaxy? References are important.

 

[Cbdb2]

Most people dramatically over estimate the speed of the attack phase of musical instruments - even percussion. Typically cymbals are used as an example. You can download a cymbal clip here:

Free Cymbal Sound Effects | MP3 Download | FesliyanStudios

Free sound effects of cymbals including hits, crashes, crescendos, swells, scrapes and more! Highest HD quality MP3 downloads available.

www.fesliyanstudios.com

I've used : Crash-Cymbal-Hit-B
Opening in Audacity, it looks like this (one channel). The total attack phase (from start to peak volume) is about 0.17 seconds.

View attachment 364134

Zooming in to the attack phase, you can see it starts just before 0.14 seconds (actually around 0.139) The initial strike lasts until about 0.147 (around 8 thousandths of a second), before the lower frequency shhhh sound starts. The lower frequency shh fundamental is in the region of 500 to 700Hz

View attachment 364135

Then zooming in further to the start of the attack (The strike). See how low the initial amplitude is - and how slowly it ramps up. And the frequency of those first few cycles we are looking at is about 8.7kHz (the file sample rate is 48kHz) - less than half the usual minimum speaker bandwidth.

I don't think the average speaker is going to struggle to keep up here. Remember with a 20Khz sine wave, it is starting, getting to full speed, and stopping again before going in the opposite direction 40,000 times a second.

View attachment 364138

Not just music. As a sound fx editor I saw waveforms of gunshots and explos, nothing has a rise time of less than a few samples (at 44.1khz). Recorded sound is bandwidth limited (LP filtered) which means the rises time (speed) is also limited, most obviously in digital to 1/sample rate. As already stated many times speed and freq. response are the same thing. A fast sub is an oxymoron. What audiophiles use the word to describe I have no idea. I bet if I slowed down a "fast" speaker by LP filtering to 10khz (half as fast) it would still sound "fast". If its about no overhang why not call it that or damping?

 

[Basic Channel]

Not just music. As a sound fx editor I saw waveforms of gunshots and explos, nothing has a rise time of less than a few samples (at 44.1khz). Recorded sound is bandwidth limited (LP filtered) which means the rises time (speed) is also limited, most obviously in digital to 1/sample rate. As already stated many times speed and freq. response are the same thing. A fast sub is an oxymoron. What audiophiles use the word to describe I have no idea. I bet if I slowed down a "fast" speaker by LP filtering to 10khz (half as fast) it would still sound "fast". If its about no overhang why not call it that or damping?

I think people are probably describing a lack of inertia. At least when describing the speed of planars/etc. Hence "speedy" drivers tend to have poor/no low frequency response.

At least that's what I think I am describing. Detail is probably a better word.

 

[beeface]

Relative to the earth's surface, to the sun, or to the center of the galaxy? References are important.

relative to the ruler I placed next to it

 

[Dave Bullet]

I'm going to quote the late (great) Jeff Bagby on this one... (re driver size and speed). This does not cover group delay and enclosure related impact.

"There is still a lot of misinformation about this on the web, and this leads to a lot of confusion and misapplied physics. Larger drivers are not slower than smaller drivers, this is a myth. If the mass is greater and the motor is the same as the small driver then the sensitivity will be lower, but it won't be slower. If the motor is stronger and the sensitivity is the same, it will not become faster. What we perceive as fast and slow is generally a matter of bass extension, bass damping (Q) and room decay time. Larger woofers typically have a lower Fs and are able to extend deeper, this creates the perception of slower. If the smaller drivers are EQ'd to the identical extension and Q, then they will sound the same. PA drivers are generally designed to be very efficient, but have a higher Fs and do not extend as low. Still they can thump you hard in the chest. This is motor force vs mass. This topic comes up often and typically runs this course. So, at this time I am going to close commenting on the thread as there continues to be too much misinformation here. If someone has something relevant that they wish to post then message me and we will discuss it, and I may open the commenting up for that. - Jeff"

 

[Newman]

I'm going to quote the late (great) Jeff Bagby on this one... (re driver size and speed). This does not cover group delay and enclosure related impact.

"There is still a lot of misinformation about this on the web, and this leads to a lot of confusion and misapplied physics. Larger drivers are not slower than smaller drivers, this is a myth. If the mass is greater and the motor is the same as the small driver then the sensitivity will be lower, but it won't be slower. If the motor is stronger and the sensitivity is the same, it will not become faster. What we perceive as fast and slow is generally a matter of bass extension, bass damping (Q) and room decay time. Larger woofers typically have a lower Fs and are able to extend deeper, this creates the perception of slower. If the smaller drivers are EQ'd to the identical extension and Q, then they will sound the same. PA drivers are generally designed to be very efficient, but have a higher Fs and do not extend as low. Still they can thump you hard in the chest. This is motor force vs mass. This topic comes up often and typically runs this course. So, at this time I am going to close commenting on the thread as there continues to be too much misinformation here. If someone has something relevant that they wish to post then message me and we will discuss it, and I may open the commenting up for that. - Jeff"

Good on you Jeff.

I will repost here (notice the similarity in thread titles) my graphical attempt to illustrate the bit in bold above:-

Here is a Purifi illustration ( © Purifi, fair use claimed):-

The key point is that the sound pressure -- the bit we hear -- tracks the acceleration exactly, even with a perfectly instantaneous pulse. It doesn't look like the velocity, it doesn't look like the displacement.

Notice especially how quickly acceleration and sound pressure responded to the instantaneous signal: they responded instantly, and to their full value.

The velocity takes time to respond to the impulse, the displacement takes time to respond, but the sound pressure doesn't.

So let's look only at acceleration and sound pressure, when we add mass to the diaphragm:-

And notice what DID NOT HAPPEN:-

Perhaps this makes it a little clearer to the reader why adding mass doesn't change the speed and responsiveness of the sound pressure.

cheers

 

[Ze Frog]

I've always looked at it as the time it takes for the voice coil to return to natural resting position, which is probably completely wrong. It's kind of why personally I like sealed for low frequencies as there's a force waiting to pull the woofer back quicker after it's current excursion in a perfectly sealed cabinet because of the air pressure wanting to equalise.

 

[antcollinet]

I've always looked at it as the time it takes for the voice coil to return to natural resting position, which is probably completely wrong. It's kind of why personally I like sealed for low frequencies as there's a force waiting to pull the woofer back quicker after it's current excursion in a perfectly sealed cabinet because of the air pressure wanting to equalise.

You don't need that force. The current in the voice coil combined with the magnet (together the motor) brings it back. It doesn't just hang around waiting for the "spring" part of the spider to pull it back.

 

[Ze Frog]

You don't need that force. The current in the voice coil combined with the magnet (together the motor) brings it back. It doesn't just hang around waiting for the "spring" part of the spider to pull it back.

So I'm guessing BL factors into a woofer's speed combined with cone weight possibly?

 

[Keith_W]

You don't need that force. The current in the voice coil combined with the magnet (together the motor) brings it back. It doesn't just hang around waiting for the "spring" part of the spider to pull it back.

Are you sure about that? The Qts is the combination of Qms (mechanical damping) + Qes (electrical damping). The Qms or mechanical damping is influenced by the surround and the spider, but also by the air spring, i.e. the volume of the enclosure. If you have your subwoofer amps turned off and you push the driver in, it indeed hangs around waiting for the "spring" part of the spider to push it back.

 

[antcollinet]

So I'm guessing BL factors into a woofer's speed combined with cone weight possibly?

OMO, speed is just frequency. High frequency is high speed. Nothing else makes any sense to me.

 

[olieb]

If you have your subwoofer amps turned off and you push the driver in, it indeed hangs around waiting for the "spring" part of the spider to push it back.

Yes, but in this case the motor ("you") is pushing only - and never pulling back. That is not what is happening with a sound/tone.
If you would leave out the springs (open baffle, no spider and very soft suspension, i.e. a true ribbon) then the speaker will still work. But there are practical problems: Small forces (DC, air movement aka "door") might push the diaphragm away.

 

[antcollinet]

Are you sure about that?

No. Speakers are (by far) my weakest area.

The Qts is the combination of Qms (mechanical damping) + Qes (electrical damping). The Qms or mechanical damping is influenced by the surround and the spider, but also by the air spring, i.e. the volume of the enclosure

However, damping is not force, except in that it opposes motion.

If you have your subwoofer amps turned off and you push the driver in, it indeed hangs around waiting for the "spring" part of the spider to push it back.

And we don't turn off subwoofer amps while we are playing music. Question here, is how large is the spider force, compared with the motor force.


Quite happy though to be informed I am an idiot by someone who actually understands how speakers work in detail.

 

[olieb]

OMO, speed is just frequency. High frequency is high speed. Nothing else makes any sense to me.

There is a list of (well defined) terms that could be identified with "speed".
Diaphragm velocity, frequency, group delay,...
But in most cases it does not mean any of this.
It is a foggy word to describe some impression about the sound, connected to "attack", "detail", "dynamic", "loudness", "punch", and so on.
What it might mean and what it might correlate to is probably different in each case.
It is somewhat moot to discuss, if everybody means something else ;-)

 

[Tell]

Is this a thing? The upper is the input signal and the lower is the speaker output, so if there is a difference between speakers in how fast it is to get up to a given amplitude?

 

[Keith_W]

No. Speakers are (by far) my weakest area.

In all honesty and humility, I have to say I am in the same boat as you. My experience with "speaker design" is limited to designing a pair of subwoofers for myself and reading (well, skimming) Vance Dickason's book.

And we don't turn off subwoofer amps while we are playing music. Question here, is how large is the spider force, compared with the motor force.

The Qms (mechanical damping) varies from driver to driver, and from enclosure to enclosure, particularly ported designs and where the resonant frequency of the port is. In general, I believe that the Qes (motor force) is much higher than the Qms (mechanical force). Happy to be corrected by someone who knows more.

 

[Ze Frog]

There is a list of (well defined) terms that could be identified with "speed".
Diaphragm velocity, frequency, group delay,...
But in most cases it does not mean any of this.
It is a foggy word to describe some impression about the sound, connected to "attack", "detail", "dynamic", "loudness", "punch", and so on.
What it might mean and what it might correlate to is probably different in each case.
It is somewhat moot to discuss, if everybody means something else ;-)

Yeah, good point, a lot of the time it's merely batted around as part of a reviewer's word salad. I've even heard claims of a boost at say 150Hz giving the impression of 'speed', not really sure how that gives an impression of 'speed', not in the way I invisage it at least. That's not to say I'm right in my understanding, definitely a very complex area with so many potential variables that goes way above my limited understanding.

 

[Basic Channel]

Apologies if i am misreading some posts…..

Is the idea that higher mass takes longer to stop and start moving not really applicable to audio?

 

[Ze Frog]

Apologies if i am misreading some posts…..

Is the idea that higher mass takes longer to stop and start moving not really applicable to audio?

In my mind it is, but it's usually offset by stronger BL/motor force and other variables within a well designed driver. I'm no electrical engineer, and to be honest I'm thinking there's more than one correct answer as I can see merit to all points of view on this so far.