What does the term "Speed" mean in a speaker?

i think speed in a speaker mostly refers to the mid and upper bass 50hz-250hz region which are the power frequencies where the music lives. vocals, drum kits, pianos, cellos, horns.....they all fall down or rise in this area.

leading edge precision and the presence or lack there of ease and refinement in these frequencies either impart flow and energy to the music and maintain the timing or muddle and restrict that flow and energy.

this is a speaker-amplifier-room issue, not just the speaker. and typically you see a crossover right here, amps struggle controlling the drivers here, and rooms have most of their worst bass nodes in this area. as you increase the dynamics and SPL’s this will be where things go to hell first as the combination of the speaker’s limitations, the amp and the room acoustics all rear their ugly heads.

but get the crossover out of this region, have sufficient driver surface to limit the need for much excursion, and appropriate amplifier for the speaker draw, solve the room issues, and you can get the ease and effortlessness and the speed and precision of the music will result in that speed that serves the music, the music breathes and soars.

Has anyone heard Martin Logan speakers? The electrostatic panel plays the mid and treble while the woofer plays the low frequencies.

I always felt like the woofer was slightly lagging behind as if the bass and the upper frequencies were playing slightly different tune.  The bass was in effect "slower" vs. the mids and high frequencies.

Also, most of the time, speaker frequency responses are measured in steady-state response which more or less erases the transient response, but the "speed" lies in the transient response.  So two speakers can have the same freq. response but one may be faster than the other.

May be a step response measurement can tell you the "speed" of different speakers because it preserves the transient information.

Mass and inertia guys. Transient response is how fast the driver starts and stops. Lets say you have 6 inch speakers with identical voice coils and magnets. In one the cone weights 1 oz and in the other the cone weights 2 Oz.  When I play a transient sound like a drum stick hitting a steel plate the 1 oz cone will start moving fractionally before the 2 oz cone because it has less inertia. It will also stop faster with fewer oscillations (ringing). Things are really more complicated as the Transient response of a driver is not only determined by the mass of its moving system but also by the power and damping capability of its motor. So an 8 inch woofer does not necessarily have better transient response than a 12" driver. Speakers with better transient response have a crispness to their sound missing in speakers that don't. This becomes quite evident when listening to ESLs, well designed horns, ribbons and to a slightly lesser extent planars. Speakers with better transient response are more revealing and can easily be made to sound crappy with bad or poorly set up equipment which I think is why some people have a jaundiced opinion of them particularly horns which are also not easy to design. 

I think a lot of what you are writing about, mijostyn is actually related to room interactions.

Your writing, while accurately portraying how dynamic drivers work makes a leap I don't feel comfortable following.

A dynamic driver can have a lot more dynamic range, smoother frequency response, better low frequency and lower distortion than a planar speaker attempting the same. What it won’t do is interact with the room the same way. Genesis got around this by making towers of 12" drivers. :)


Snell mounted the woofers as close to the floor as possible.

The final result is always a matter of speaker and room interactions, but the idea that planar speakers are measurably faster is not true.


Best,

Er

mass and inertia matter, but you missed one parameter, driver surface area, which determines the amount of excursion for a particular level of volume, which goes a long way determining the linearity of the response.

mostly in the mid bass you find one driver, maybe two. or two crossed over. my speakers each have -4- 97db, 7ohm, 11" ceramic matrix woofers. covering 40hz--250hz. with all that surface area and a very stiff light ceramic membrane, the need just a tiny bit of excursion so they stay linear. and the amplifier is not stressed by the load with 97db efficiency.

so you get planar or horn type speed, but dynamic cone impact. images have weight and authority. tonality is maintained and not washed out.