Talk:Damping factor

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[edit] LCs restatement

I stand by my statement that this guy is talking thro his *****le. I reiterate my statement that:

voltage at speaker terminals does NOT determine the position of the cone. It is the voice coil current that does that. The voltage comprises a portion due to I*Z and a portion due to the emf generated by the moving cone.

I invite anyone to try to prove me wrong (or right if you so desire). Comments from other educated editors are welcome. :-|--Light current 02:05, 26 April 2006 (UTC)

I think YOU don't know what you are talking about. Instantaneous current (and position) will give you the instantaneous FORCE. Solving the equation of motion, you can find the position given the instantaneous force history, current history, or VOLTAGE history. It many ways its all the same thing. - TheShagg

For any value of steady current through the coil, a force is produced proportional to that current. THe force acts to move the cone until it is balanced by the stiffness of the suspension.--Light current 17:40, 12 October 2006 (UTC)

[edit] Critical damping

I think Im right in saying that what is required from a low frequency speaker system is critical damping. That is, not underdamping (where you get hangover) or over damping (where the cone just wont move fast enough in response to a step voltage input). Now it is my contention that a speaker is a mechanical system with a mechanical to electrical transformer (the voice coil) attached and this transformer is driven by an amplifier of usually very low output impedance.

[edit] Transformation analysis

Since the mechanical force on the coil, fm is given by:

fM=Bli

and the emf developed by the moving coil is

e= Bl dx/dt

It is therefore evident that:

ZEM = (Bl)^2/ZM

where ZEM is the electrical impedance due to motion, and is termed the 'motional electrical impedance'. The mechanical to electrical transformation ratio for impedances is therefore (Bl)^2 and is determined solely by the voice coil/magnet assembly.

Now in analysing such a system, one may choose to convert the mechanical components (mass, compliance, acoustic resistive or reactive loading etc) into electrical components or vice versa by referring the elements to one side or the other of the 'transformer'. It is usually easier to do the former and analyse the performance in the electrical domain. The mechanical/electrical transformer is of course an electric motor/generator. The transformation constant (Bl)^2 is a scalar and therefore does not change the phase angle of the impedance when transformed, only its magnitude. Therefore inductive components (masses) transform to inductances, and capacitive (compliances) transform to capacitors, whilst resistors (mechanical dampers) transform to resistors.

The total electrical impedance seen at the voice coil by the amplifier, Zen, is given by the sum of the damped electrical impedance and the motional electrical impedance ie:

Zen =Ze1 +Zem

Now Zen can be represented as a series combination of R,L and C. The L represents the transformed mass of the cone in the mechanical cct, and the C represents the total transformed compliance of the driver. The R represents the sum of the transformed motional resistance plus the electrical (DC) resistance of the voice coil.

This analysis appears to be original work. Wikipedia is not the place to publish original work. Tvaughan1 00:47, 15 October 2006 (UTC)

[edit] Damping methods

It should be evident that damping of this (essentially second order) system can be accomplished either by mechanical means or by electrical means or by a combination of the two. There is however an inherent limitation in the 'electrical only' damping method. That is the finite resistance and inductance of the voice coil. This can only be reduced by the use of a 'negative' resistance in the amplifier and this is usually not employed for stability reasons (ie it tends to turn the system into an oscillator)

The complete electrical equivalent circuit of a loudspeaker in a cabinet is shown in the figure.

For the system to be critically damped, we can see that in the electrical equivalent circuit, R must be of a certain (critical value.

To be continued... Please do not interrupt this post >:-{

--Light current 17:02, 26 April 2006 (UTC)

Yes. We do. Across the full frequency range of the speaker. But the article is about damping factor, so it needs to focus on how you design or evaluate an amplifier (which may have any speaker connected... cheap or well designed... in various configurations (alone, series, parallel), through wires with unknown length or resistance. Tvaughan1 22:38, 26 April 2006 (UTC)

OK then watch this space!--Light current 22:14, 27 April 2006 (UTC)

[edit] Holy bejesus, cleanup?

I can't believe this page! Its like 5 times as long as the article. Does anyone think this talk page needs some cleaning/archiving or something? Fresheneesz 04:17, 19 May 2006 (UTC)

Ive archived about 40k s worth but we're still in the middle of a heated discussion so I think the rest should stay for a while. Just having a cool off between rounds!--Light current 13:22, 19 May 2006 (UTC)

[edit] audio only?

Is this page only applicable to audio amplifiers? Comming to a page on the damping factor, I would expect a more general treatment. For example, I was looking for the definition of the damping factor in terms of any general circuit. Does the definition of source impedance vs load impedance work in general, or just for audio amplifiers? Fresheneesz 00:22, 5 June 2006 (UTC)

No, its not restricted to audio amps ATM! It should be a very general treatment.We could put a note at the top of the page saying this page only applies to audio and redirecting others to damping? The definition 'source impedance vs load impedance' is specifically reserved for audio amps and is not the general defn of damping factor. Please see damping 8-)--Light current 00:30, 5 June 2006 (UTC)

I think that perhaps this subject needs a bit of a reorganization. We could change the name of this article to damping (electronics), and have a little disambig for damping factor that can redirect to either page (damping or damping (electronics)) - since it seems like the damping page doesn't cover anything about circuits. Fresheneesz 02:43, 7 June 2006 (UTC)

Or.. yes it does have stuff about electronics. I didn't even see that. Fresheneesz 02:44, 7 June 2006 (UTC)

[edit] Zero electrical damping factor

Whoever wrote this nonsense doesn't understand how a speaker works.

Firstly, once you place a speaker inside a sealed box, there is less damping on the cone at resonance. The speaker has to overcome the air in the box, this is why the system Qtc is always larger than the Qts.

The cone excursion *is* controlled above resonance, thus it is linear until the Levc becomes significant. Below resonance it is reduced due to the order of the system.

The major issue about control is not due to the Levc, but at resonance. So even though a zero damping factor may correct for the inductance, we will be left with a huge cone excursion (and frequency response) peak at resonance due to the large electrical losses (very high Qts and Qtc). With a zero damping factor, the frequency response will not extend down to dc.

I believe you can model the effect of a very small damping factor in loudspeaker modelling programs, (such as Winisd Pro which you can download for free) simply by entering in a large value for the series resistance. Or you could go out and test it for yourself.

If you wish to correct for the second order roll off, you simply need to equalize the response with a 12db/octave filter. In reality, you won't want to do this all the way to dc because you will get negligible output. But you can use a filter that extends the response to a lower frequency (at the expense of efficiency) There are a few different filters that you can use, but you should consider the linkwitz transform filter as a possible solution, rather than this zero damping factor nonsense.

Arch.

What are your references? — Omegatron 13:40, 27 June 2006 (UTC)
This was based on my own understanding, I don't have time to sort this out properly. But if you want serious references for the article, then you should look at all of the usual sources - Richard Small's papers, books like "The Loudspeaker Design Cookbook" and so on.

There is information about the Linkwitz transform filter, http://www.linkwitzlab.com/filters.htm#9 and http://sound.westhost.com/linkwitz-transform.htm

The losses through Re are not critical as it is easily possible to design a driver so that the Qts is less than 0.5 (critical damping). (It has to be significantly less than 0.5, so you can account for the enclosure too...)
If you add series resistance, then you are dramatically reducing the electrical damping, thus raising the Q dramatically (obviously making things much worse).
Oh, and have a look at this page too: http://www.linkwitzlab.com/thor-design.htm --Arch 11:25, 28 June 2006 (UTC)
Firstly, once you place a speaker inside a sealed box, there is less damping on the cone at resonance. The speaker has to overcome the air in the box, this is why the system Qtc is always larger than the Qts.
Could the author explain why theres less damping in a sealed box? I thought there was more due to the reduced compliance of the air load at the back.--Light current 13:37, 27 June 2006 (UTC)
Yes, there is reduced compliance of the air load, so the resonant behaviour of the loudspeaker is increased. (Hence why the Qtc also increases) --Arch 11:25, 28 June 2006 (UTC)
Yeah So there is more damping. You said less! 8-(--Light current 11:32, 28 June 2006 (UTC)
there is less damping. Qtc > Qts. oscillations in the system don't loose energy as quickly, thus less damping. less air, more pressures. boxes smaller than Vas will have the suspension provided by the air volume instead of the speaker. as box volume increases to values much larger than Vas, Qtc approaches Qts by definition. —The preceding unsigned comment was added by 68.75.154.192 (talk) 01:37, 9 February 2007 (UTC).

[edit] Page name

I propose this page is called Loudspeaker damping factor to differentiate it from the other sort related to the detailed issue of damping.--Light current 15:46, 27 June 2006 (UTC)

Damping has a section about loudspeakers, too. Definitely need to either merge or disambiguate, depending on whether they're related enough — Omegatron 15:51, 27 June 2006 (UTC)

My initial reaction is that they are not related except by name. But Ive been meaning to make sure.8-|--Light current 20:14, 27 June 2006 (UTC)

THey cant be the same thing as audio damping factor is just a ratio, whereas real damping factor has dimensions of frequency.8-|--Light current 21:25, 27 June 2006 (UTC)


[edit] Critical damping of loudspeakers

I believe that critical damping of a loudseaker cone by electrical methods is, in almost all cases, impossible due to the non zero resistance of the voice coil.--Light current 10:30, 28 June 2006 (UTC)

it is possible. the poles are in the left half plane and can be canceled. many speakers have a Qts < 0.5, and will be overdamped unless put in a box that is not "large" compared to Vas. —The preceding unsigned comment was added by 68.75.154.192 (talk) 01:39, 9 February 2007 (UTC).
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