LE, not MMS determines woofer "speed"!

Edited by asaa00 - 15 September 2016 at 3:14am

This is knowledge gained from electric motors. 

Acceleration = Force/Mass

So if the motor assembly (VC & Magnet) stays the same and the amount of power being put into the speaker stays the same, a driver with lighter cone will accelerate faster (will have better transient response and better response at higher frequencies)?

EV for a long time used a single magnet design from 18" through to 10" (with two different 2.5" VC options, Edgewound Aluminium or a Conventional Copper VC) and most of the difference between the "bass" drivers and the "mid" drivers was just a lighter thinner cone as the "mid" driver wasnt expected to be asked to push as much air and so, didnt need to be as strong

The author of that paper seems to be confusing frequency response with transient response a little in some places, or if they are not then it isn't very clearly written. Getting my science hat on the paper is written enthusiastically and it is clear the author knows a few things, but could be tidied up a lot with a few redrafts. No offense intended, was just the way it read to me. The conclusions are probably valid, but a lot more testing and proper analysis of data is needed for a really watertight conclusion. (I.e. more than just visual graph comparison). No strong evidence is presented for why Le is more significant than added mass, a single data point of comparison is presented for each. How do you relate the effectiveness of each change such that the test is fair?

Anyways from the top of my head I would hazard that increasing Le does two basic things. It is an electronic change after all. Larger inductances give increasing impedance for a given frequency, which means your frequency response will fall off quicker because current reduces and so does the ability of the voicecoil to generate magnetic force which is linearly proprtional to current.

The second is that when you have a series RL circuit, current no longer leads voltage by 90 degrees as it does in a pure inductor circuit. The phase shift will be spread out from 0-90 degrees as the inductor moves from being a short (0 phase) at DC to infinite resistance relative to R (90 degree phase) at high frequencies.

I strongly suspect that it is this variable phase shift (depending on the bandwidth of the driver and additional effects on phase of the cabinet design) that most causes poor time alignment and 'time smearing' of an input signal that was originally time aligned.

With added mass, I would expect a phase shift to beconstant over a driver bandwidth, not so with an Le change. Damping would also change as a result of added mass.

odc04r wrote: The second is that when you have a series RL circuit, current no longer leads voltage by 90 degrees as it does in a pure inductor circuit. The phase shift will be spread out from 0-90 degrees as the inductor moves from being a short (0 phase) at DC to infinite resistance relative to R (90 degree phase) at high frequencies. I strongly suspect that it is this variable phase shift (depending on the bandwidth of the driver and additional effects on phase of the cabinet design) that most causes poor time alignment and 'time smearing' of an input signal that was originally time aligned.

so does this mean that they should have rather built a second driver with identical specs except for a longer voicecoil with higher Le to make the research valid?

kevinmcdonough wrote: And given stronger inductance in the coil, it will also react faster to the changes.

isn't that exactly the opposite of what he is stating?

kevinmcdonough wrote: Or if they have the same breaks, but one car is a steel body and one carbon and aluminium and so much lighter. Again, the lighter one will stop quicker, even if the reaction time was slightly longer at the start.

That's exactly what I was referring to with my comment about overshoot.....