Damping?
03-15-2009, 08:50 PM
#21
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In Negative FeedBack design, where amplifier compares speaker's impedance vs. actual state(position in VC gap) and applies appropriate gain to control motion.
It would vary in accordance to frequency and voltage
So is the damping factor always fluctuating as well? If the driver's voice coil position sends a different negative feedback, depending on where it is situated in the gap and the rate of speed at which it is moving, then the amp will respond accordingly with the appropriate gain.
I need to dumb this down a little. When a subwoofer is being driven in a given direction, inertia makes the mass of the driver want to continue moving in that direction even when the force ceases. At this point it is driven in the other direction in order to reproduce the frequency from the source. The higher the damping factor, the easier it is for the amp to maintain control of the driver at that point.
So the mass of the moving parts must be critical too? A heavier mass would result in a stronger Back-EMF, no? More mass would require a stronger damping force to control it?
Originally Posted by TragicMagic View Post
All audible or non-audible arguments aside; what does an amp's damping factor indicate about the design/quality of the unit, if anything at all. Is there anything that can be assumed if amp 'A' has a DF of 250 @ 4 ohms, while amp 'B' has one of 100?
All audible or non-audible arguments aside; what does an amp's damping factor indicate about the design/quality of the unit, if anything at all. Is there anything that can be assumed if amp 'A' has a DF of 250 @ 4 ohms, while amp 'B' has one of 100?
Just trying to learn.
03-15-2009, 09:24 PM
#22
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If a driver is a DVC 4 ohm, it has a nominal impedance of 4ohm + 4ohm (at least that's what it'll show on a spec sheet...) Depending on how the VC's are wired, you can either put a 2 or 8 ohm load on the amp. I've seen that higher loads result in greater damping factors. Yet I still don't know what the driving impedance would be.
Not really. "Enough" damping factor is easy to achieve these days. With transistor amps anyway. What you consider to be enough is up to you.
03-15-2009, 09:43 PM
#23
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Driving impedance, that is the amp's output impedance, varies very little with frequency. The voltage is irrelevant.
03-15-2009, 10:46 PM
#25
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what's not being taken into account is the most important part...the dc resistance of the speaker itself. Given that all speakers have their own DC resistance on the order of 3ohms or so for a 4 ohm speaker, and, which has to be added to the output impedance of the amp in order to get the EDF or effective damping factor. This changes the effect of the amplifier's control significantly. It is what makes an amp with a DF of 400 essentially the same as the amp with a DF of 40. For example:
if you take a 4ohm speaker and use an amplifier with a relatively high output impedance of say..0.1 ohms, you'll get a DF of 4/.1= 40, and one rated at .010 output impedance will yield a DF of 4/.010=400. This may seem like a hugh difference, but when EDF is calculated with the DC resistance of the speaker at approx 3ohms...then we get 4/3.1=1.29 EDF, and 4/3.010=1.32 EDF...not such a big difference anymore is it?? ....and that's why it's not nearly as important a spec as some would like to make it out to be!
if you take a 4ohm speaker and use an amplifier with a relatively high output impedance of say..0.1 ohms, you'll get a DF of 4/.1= 40, and one rated at .010 output impedance will yield a DF of 4/.010=400. This may seem like a hugh difference, but when EDF is calculated with the DC resistance of the speaker at approx 3ohms...then we get 4/3.1=1.29 EDF, and 4/3.010=1.32 EDF...not such a big difference anymore is it?? ....and that's why it's not nearly as important a spec as some would like to make it out to be!
03-15-2009, 10:48 PM
#26
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ok even i am getting a headache now, and it seems i started this mess.
an amplifiers damping factor will be forever changing as the speaker it is driving moves.
speakers are reactive loads and their impedance can vary many, many, many ohms while it operates.
this is why an amp's base damping factor, basically doesnt mean .
an amplifiers damping factor will be forever changing as the speaker it is driving moves.
speakers are reactive loads and their impedance can vary many, many, many ohms while it operates.
this is why an amp's base damping factor, basically doesnt mean .
03-15-2009, 10:49 PM
#27
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what's not being taken into account is the most important part...the dc resistance of the speaker itself. Given that all speakers have their own DC resistance on the order of 3ohms or so for a 4 ohm speaker, and, which has to be added to the output impedance of the amp in order to get the EDF or effective damping factor. This changes the effect of the amplifier's control significantly. It is what makes an amp with a DF of 400 essentially the same as the amp with a DF of 40. For example:
if you take a 4ohm speaker and use an amplifier with a relatively high output impedance of say..0.1 ohms, you'll get a DF of 4/.1= 40, and one rated at .010 output impedance will yield a DF of 4/.010=400. This may seem like a hugh difference, but when EDF is calculated with the DC resistance of the speaker at approx 3ohms...then we get 4/3.1=1.29 EDF, and 4/3.010=1.32 EDF...not such a big difference anymore is it?? ....and that's why it's not nearly as important a spec as some would like to make it out to be!
if you take a 4ohm speaker and use an amplifier with a relatively high output impedance of say..0.1 ohms, you'll get a DF of 4/.1= 40, and one rated at .010 output impedance will yield a DF of 4/.010=400. This may seem like a hugh difference, but when EDF is calculated with the DC resistance of the speaker at approx 3ohms...then we get 4/3.1=1.29 EDF, and 4/3.010=1.32 EDF...not such a big difference anymore is it?? ....and that's why it's not nearly as important a spec as some would like to make it out to be!
03-15-2009, 10:53 PM
#28
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Alphadawg, you're right. I was looking at my TypeR's spec sheet. Its a daul 4 ohm, while the DC resistance of each coil is 3.7.
An amp with a higher output impedance will have a lower DF? Due to the way its calculated....
The DC resistance of the speaker has nothing to do with its mass, correct?
So where, if at all, does the mass of moving parts of the driver come into effect?
An amp with a higher output impedance will have a lower DF? Due to the way its calculated....
The DC resistance of the speaker has nothing to do with its mass, correct?
So where, if at all, does the mass of moving parts of the driver come into effect?
03-15-2009, 11:09 PM
#29
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the speaker's mechanical properties have much more to do with controling it's inertia than the DF of the amp. That's why sloppy suspensions sound sloppy, and tight ones sound tight...if the DF was such a big factor, both subs should exibit similar sound qualities in terms of tightness....of course there's other factors and trade offs there as well, but it's a pretty obvious thing to hear when you have a "bouncy" sub compared to a Type X for example (very stiff suspension...very tight sound). Anyway, like doublexl and i have been saying from the get go...DF is essentially a useless spec these days as any decent amp will have more than enough to do the job so as not to be an audible factor.
