Damping factor is not a idea, it is a scaled characteristic - simply a measure of output impedance. It does not imply that an amplifier can see two impedances. Dividing one impedance by another serves the purpose of scaling. I can only assume that because you do not understand DF you assume that everyone else misunderstands it too.Joe Rasmussen said:
Again, this is not entirely correct if we're talking speaker designer nerd level talk. What the impedance correction network does is that it establishes always the same (flat) voltage response on the speaker terminals regardless of driving impedance, and equal speaker terminal voltage means equal SPL output (frequency response).
But the actual *acoustical* box alignment has changed because the termination impedance the driver sees has changed, how much depends on the amp drive impedance. Sounds like a paradoxon, but it's not:
At resonance, where a Re=4Ohms driver will peak at 40Ohms or so, the parallel network impedance must be 4.4Ohms so that total impedance level is held at 4Ohms. So, when using a current drive amp which provides no damping, the effective damping the driver sees is now its own Re plus the external impedance in series which sums up to 8.4 Ohms. The system Q will now be larger than 0.71 if was at 0.71 with zero ohms drive impedance. The back-EMF is then working into a higher termination impedance.
Tap test will confirm this, cone motion is a bit less damped with that higher impedance. This has some (non-critical) impact on distortion, large-signal and overload recovery behaviour and any external exitation.
With pure current drive, no compensation network and amp input EQ'd to give the same terminal voltage response as with voltage drive the effects are way more drastic, the true alignment changes dramatically (undamped, to the point of being unusable, sometimes) whereas the apparent alignment, as judged by frequency response, stays the same.
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Dan, you try make sense of him, I have decided just to ignore him. He thinks I have a fan club. I think I would know if I had one. Maybe he is envious? He doesn't need to be.
No, I shall just ignore him. I won't keep a grudge, so if he changes, I will change. It is gangrene of the soul, I have no need for that.
I see that he is English. I'd better not tell him I am a Manchester United fan and with my luck he is a Liverpool fan? Sigh.
I actually am a bit of an anglophile, much of English humour is aligned with Danish humour. The other Scandinavians don't know how to have fun. They have no sense of irony. Makes me wonder if he has Swedish blood? Does he have a Swedish name? I wouldn't know, he doesn't have the courage of using his own name? I do.
His last post was totally EE contradictory. DF was denied by Langford-Smith who regretted coining the phrase because he realised it was meaningless. It is not EE, it is folklore. Why would you need a DF number when you can just state the output impedance. By being given a number, DF, and then you need another number, the speaker, then undo the DF calculation to figure out the output Z.
That is the very definition of EE madness. Not EE at all.
Does he even know who Langford-Smith was?
Nah, ignore him, He just wants to troll me. He should at least have the courage to tell me his name.
One should not reply to ghosts.
Can we respectfully discuss this? You might be surprised.
I think there are a number of things you have addressed that does require thoughtful response. I would like that.
So? Let me know. Late evening now. Bonne nuit.
No, I shall just ignore him. I won't keep a grudge, so if he changes, I will change. It is gangrene of the soul, I have no need for that.
I see that he is English. I'd better not tell him I am a Manchester United fan and with my luck he is a Liverpool fan? Sigh.
I actually am a bit of an anglophile, much of English humour is aligned with Danish humour. The other Scandinavians don't know how to have fun. They have no sense of irony. Makes me wonder if he has Swedish blood? Does he have a Swedish name? I wouldn't know, he doesn't have the courage of using his own name? I do.
His last post was totally EE contradictory. DF was denied by Langford-Smith who regretted coining the phrase because he realised it was meaningless. It is not EE, it is folklore. Why would you need a DF number when you can just state the output impedance. By being given a number, DF, and then you need another number, the speaker, then undo the DF calculation to figure out the output Z.
That is the very definition of EE madness. Not EE at all.
Does he even know who Langford-Smith was?
Nah, ignore him, He just wants to troll me. He should at least have the courage to tell me his name.
One should not reply to ghosts.
Can we respectfully discuss this? You might be surprised.
I think there are a number of things you have addressed that does require thoughtful response. I would like that.
So? Let me know. Late evening now. Bonne nuit.
You'll have to go back and look (George has finally lost interest in this discussion). The tape was marked with an industry standard spec number for HVAC duct work similar to UL approval I suppose.
@Jakob My comment about ideal voltage amplifiers was not meant to be taken literally, the concept of output impedance being cancelled no matter what it is is wrong here, you should know that. Saying otherwise is disingenuous.
Loving SET amplifiers with high output resistance and tweeking their response with cables and shunt networks for your choice of speakers is as old as the hills. It all yields to some pretty old fashion engineering. I have a text book on network synthesis from the 50's. Complex parallel/series conversion of impedances, etc. is not taught that much anymore. Cables always have R, L, and C nothing you do in the speaker will change that.
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I've found the article from 1986 in the archive and the stereoplay (german mag) measurement crew used the combination of Sondek LP12 with Ittok LVII and Karma cartridge (all together used as reference model for turntable reviews) and found the sympathetic resonances that seemed to be responsible for the overall very exciting sound, when placed on the famous Ikea table inside of the listening room.
If placed outside of the room, no sound advantage compared to another TT (in this case a Micro Seiki) was detected.
Your observations seem to be inline with their findings; the resonance support helped allegedly against some weaknes of the Karma cartridge.
@Max Headroom,
it is/was 367-17
The inside pic was included in this post:
John Curl's Blowtorch preamplifier part III
it is/was 367-17
The inside pic was included in this post:
John Curl's Blowtorch preamplifier part III
Yes it is UL listed, typically an inspector would expect to see this when they do a walk through rather than some packing tape.
367-17 - Nashua 367-17 FOILMASTIC - UL 181B-FX LISTED Foil Sealant Tape
Given the semantic difficulties in this ongoing discussion, I have doubts that the "should not be taken literally" approach will help to clear it. 😉
But seriously if amplifiers would really behave like ideal voltage sources there would no output impedance exist.
I don't know if I decode it correctly, but maybe there is some consistency albeit usage of established terms in different meanings.
If you decode "cancel" of the output impedance with "take it out of the game" (not perfectly of course) it IMO makes some sense.....
I think I've mentioned this cycling around "problem detected, solution found, ..............solution forgotten" in the past and you did too; remember what you've said about the topic of dither in the beginning of widespread digital audio usage.
There are all sorts of dimensionless numbers used in engineering... Poisson's ratio, Reynold's #, etc come to mind that provide valuable insights into the problem(s) at hand. I don't see how damping factor is of no use... seems clear that it represents the ability of the amp to deliver adequate drive to the load under conditions with demanding reactive loads, among other things.
Sure DF is a measure of how well an amp delivers energy but it says nothing about how an amp can't cope with return energy.
Just like the term hi-fi. Some have their own definition of it and try to push it.
Damping Factor is how well an amplifier can control returned energy. In practice once it exceeds 10 it is not usually perceived. The AES standard as a result requires test setups to have a minimum damping factor of 20.
Damping factor is usually limited by the cable connecting the audio amplifier to the loudspeaker.
Many manufacturers like to express it at low frequencies as it drops with frequency. So amplifiers may have a rating of (Crown ma5000i) in excess of 5,000. This requires a cable to have a resistance of less 1.6 milliohm to keep it above 2,500. That would be about six inches of 10 gauge loudspeaker cable!
I mean the spectral nature of the control/dumping of return energy, and yes I understand the maths and yes the MA-5000 spec has always been moot.
PS - How do you get 5kW down the 240V/15A AC cord ??.
PS - How do you get 5kW down the 240V/15A AC cord ??.
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It is of questionable merit because it is most often not known under which conditions it was measured. Which frequency, which level?
Usually it is spec'ed wrt to an idealized loudspeaker impedance of 4 or 8 Ohms without any relation to a reactive load.
As you already know, this is audio device so the audible aspect is the core issue, which brings up the following question. What about the listening test?
Of course, it is a single number. It still has a useful meaning that people understand
Not necessarily, nothing prevents from measuring a frequency dependent plot. Even more interesting is measurement of output impedance as a function of both frequency and amplitude, which displays a non-linearity of the output impedance. Serious designer would make so, though it is seldom published.
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