Dynamic capabilities of Loudspeaker

[reins]

Hi,

after reading many threads, I wonder what the important parameters are in regard of the dynamic capabilities of a speaker.

First of all, every speaker is capable to reproduce sound in the bandwidth he is designed for. This is simply shown by the response curves.

What I understand, there occurs compression when a very loud signal has to be reproduced. To my understanding the peek of the output signal (sound) isn't as high has the peak of the input signal (voltage).

Is is possible to predict compression from the drivers parameters?

Often mentioned are parameters like force factor Bl, moving mass mms but also inductance Le and resistance Re.

What does high sensitivity mean in regard of low compression?

Any input?

Best regards
Stephan

 

[DcibeL]

Well, low compression at high output cannot be determined by T/S parameters. You can get some sort of an idea though by looking at the driver's construction

If you look at things like the BL curve, and how various parameters change (BL, inductance) over the excursion of the driver, you can get some idea of how the driver will perform under stress. Better motors consisting of adequate ventilation, phase plugs can often help greatly with heat removal, and that the driver is very linear (it's parameters do not change much) in it's excursion range, all lead toward a driver that will perform under high power input.

High sensitivity drivers have the edge in power compression due to several factors. Since they are highly sensitive, to create a high output they require much less power input, meaning less heat dissipation of the voice coil. Also, high sensitivity drivers generally have a larger voice coil diameter than low sensitivity drivers, which does a lot for heat dissipation as well.

Apart from that, often you will see that high sensitivity drivers are an underhung motor design, so they are more likely to be more linear within their excursion limitations.

 

[454Casull]

Apart from that, often you will see that high sensitivity drivers are an underhung motor design, so they are more likely to be more linear within their excursion limitations.

On the contrary, I see that most high-efficiency drivers (e.g. pro woofers) are overhung.

 

[badman]

Most drivers in general are overhung. But underhung is more common amongst pro mids, where power handling within a low-excursion bandwidth is more important than 'hifi' midwoofs, where they need to go lower. Underhung within its excursion evacuates heat better since the copper has metal to conduct heat away along its entire winding height, as opposed to a 'regular' overhung which has only air along much of the coil. Air is a poor heat conductor.

 

[reins]

With speaker dynamic, there is often discussed about high Bl or low inductance. Do they really influence the dynamic?

Stephan

 

[sreten]

Hi,

A drivers published parameters are small signal and tell you nothing
about large signal behaviour, for this you need technical details and
/or modelling and/or testing. Klippel is into large signal parameters.

http://www.multimediamanufacturer.com/articles/mowry607.pdf

http://klippel.de/pubs/papers.asp

http://klippel.de/pubs/Klippel papers/Loudspeaker Nonlinearities–Causes,Parameters,Symptoms_06.pdf

/sreten.

 

[gedlee]

The biggest factor in dynamics for large signals is going to be thermal compression. Clearly higher efficiency is going to be a major advantage as it takes less current for the same SPL and hence less heating. But the seond closely related factor is going to be the voice coil thermal mass, which is basically the same as its mechanical mass since most VC materials have about the same thermal characteristics. Hence, it basically comes down to the size of the voice coil. Bigger voice coils will have less thermal modulation for a given SPL.

 

[reins]

I worked through some of the Kippel papers.

In essence I understood, that most non-linear behavior comes from displacement and current. The second one goes with Mr. Gedlees reply.

Another problems seems to be the strain of the cone itself. Here the parameters suggest, that a thicker cone material might be more stable for large signals.

My conclusions so far:
1. small displacement -> lager cone area
2. short ring, while absolute inductance seems not important.
Is a flat impedance curve a indicator of more linear behavior?
3. over/underhung construction
4. not too light cone material
5. moderate sensitivity, the heat itself might not be a problem in a home setup, where high dynamic pulses are normally short.
6. This is more critical in the bass range then in the midrange

 

[gedlee]

I worked through some of the Kippel papers.

In essence I understood, that most non-linear behavior comes from displacement and current. The second one goes with Mr. Gedlees reply.

Another problems seems to be the strain of the cone itself. Here the parameters suggest, that a thicker cone material might be more stable for large signals.

My conclusions so far:
1. small displacement -> lager cone area
2. short ring, while absolute inductance seems not important.
Is a flat impedance curve a indicator of more linear behavior?
3. over/underhung construction
4. not too light cone material
5. moderate sensitivity, the heat itself might not be a problem in a home setup, where high dynamic pulses are normally short.
6. This is more critical in the bass range then in the midrange

Sorry, but I have to disagree with your list (I assume its in order of priority for good sound dynamics) I would order as

1) large VC for high BL and low thermal modulation
2) large diaphragm area for low displacement and high directivity
3) shorting ring for flux stabalization

Thermal modulation is probably more important at higher frequencies than lower ones - the voice coils tend to be smaller, but the power inputs aren't. Thermal modulation happens for any sound levels whether in a home or not - it doesn't matter. Thermal failure is not an issue in a home as it is in pro, but thermal modulation is a completely different thing that occurs for all signals at all levels.

Note that for the most part displacement nonlinearities are not a major factor and if a large cone area is used such that the displacments are minimized then displacement nonlinearities are virtually irrelavent.