The LF damping applied to the speaker is dependant on the total of the resistances in the speaker circuit.
The amplifier output impedance is but one small (or not so small) contribution to that total.
The speaker designer will design their Driver + other internal components to work with a range of external resistances to give the "damping" that speaker designer decides is best for "His Speaker".
The range of external resistances that a particular speaker will tolerate could be large or small.
These external resistances would be some or all of, cables, terminals, fuse, amplifier inductor, amplifier output impedance, amplifier cable, amplifier R in parallel to the inductor.
Amplifier output impedance could be as much as 30%, or as low as 5% of the "total external resistance" in a speaker circuit.
The difference between a DF of 1000 (Zo=0r008) and DF=100 (Zo'=0r08) in a total of around 0r15 to 0r5 is actually quite small. And if the speaker requires, or will tolerate, a part of that range say 0r2 to 0r25, then tuning the total by fiddling with Zo is a waste of time. Change the "cables, terminals, fuse, amplifier inductor, ........, amplifier cable, amplifier R in parallel to the inductor."
The amplifier output impedance is but one small (or not so small) contribution to that total.
The speaker designer will design their Driver + other internal components to work with a range of external resistances to give the "damping" that speaker designer decides is best for "His Speaker".
The range of external resistances that a particular speaker will tolerate could be large or small.
These external resistances would be some or all of, cables, terminals, fuse, amplifier inductor, amplifier output impedance, amplifier cable, amplifier R in parallel to the inductor.
Amplifier output impedance could be as much as 30%, or as low as 5% of the "total external resistance" in a speaker circuit.
The difference between a DF of 1000 (Zo=0r008) and DF=100 (Zo'=0r08) in a total of around 0r15 to 0r5 is actually quite small. And if the speaker requires, or will tolerate, a part of that range say 0r2 to 0r25, then tuning the total by fiddling with Zo is a waste of time. Change the "cables, terminals, fuse, amplifier inductor, ........, amplifier cable, amplifier R in parallel to the inductor."
Finally. Its a sort of measure of damping factor vs frequency. Great that you think this correlates in your experience. Good luck finding someone who will design against your preferred curve. I think you'll have to roll your own.
You can't design against a curve, the curve changes depending on driver. So the measurement basically tells you how it reacts with the load. As you can see in the plot I posted is actually two amplifiers with the same driver.
I just received mail from Klippel announcing their solution to driver linearity. They have been at it for a few years now. Really doing great work in measurement solutions, and now technology that can be integrated into amplifiers.
I just received mail from Klippel announcing their solution to driver linearity. They have been at it for a few years now. Really doing great work in measurement solutions, and now technology that can be integrated into amplifiers.
Yes.
And we had experienced issues with just 45cm of speaker internal wiring that tests had to be conducted to find the baseline type to use.
Tom, while going through Mod86 documentation, I noticed a change in zobel resistor value. V2 has the same as what is used in the data sheet.
Yeah... The Zobel and Thiele networks were further optimized between R1.0 and R2.0. This to ensure better stability and better transient response, in particular with a capacitive load. MOD86 R2.0 is a further development of MOD86 R1.0. I'm not sure why it's a surprise that some component values changed.
You swept my note about mains hum in your DF setup completely under the rug, by the way. You also neglected to address Bill's request for a description of what the plot was showing and how the result was derived. Care to comment?
~Tom
You swept my note about mains hum in your DF setup completely under the rug, by the way. You also neglected to address Bill's request for a description of what the plot was showing and how the result was derived. Care to comment?
~Tom
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First of all, I feel I have provided the information Bill is looking for, unless he asks anything more specific, the information is there even though it is not consolidated into one nice package.
Second, about the Hafler XL280 built from a kit, I have never heard any hum. The only thing built differently was that speaker output fuses were not used. Otherwise, everything came from Hafler. I am not sure what else you are expecting me to answer. I never did anything with the amp after the measurement. Focus was on the MyRef during that time which is shown as the red curve.
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And this is the real problem with your delusional requirments. You randomly point at sections of huge threads expecting us to read 100 pages to understand even where you are coming from let alone why you are coming from there. You DON'T WANT what Tom is offering so why are you even bothering?
You may not have heard any mains hum, but you sure did measure it. That's what causes the 60, 120, 180, 240... Hz all the way past 1 kHz crud on the green line in your plot.
~Tom
That is also an unknown in the Mod86, but if you also look at the higher frequencies, the MyRef performs better than the XL280. I am wondering what the Mod86 does.
Well, I already purchased his boards, and I also explained why. Have you?
One post explains how damping is measured and one post showing the first MyRef sim? How do you get 100 pages? What are you looking for?
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Soong, after a lot of head scratching on the links qne measuremens you provided, I gather you measure Zo by driving a separate amp through a load into the output of the DUT.
This is quite valid as Zo is usually much smaller than the load. If the load is a pure resistance, this is nearly as good as measuring Zo using a constant current source.
But I believe your 'improvement' to this method is to use a speaker instead of a pure resistance as the load.
Can you confirm this please?
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I'm still wondering why you are bothering with dis Zo < 0R1 sh*t when you are using current drive in your speakers 🙂
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BTW, Tom is right that you have some serious problems with your measurement setup including but not limited to grounding & earthing.
What soundcard are you using?
Has it got balanced inputs & outputs?
This is quite valid as Zo is usually much smaller than the load. If the load is a pure resistance, this is nearly as good as measuring Zo using a constant current source.
But I believe your 'improvement' to this method is to use a speaker instead of a pure resistance as the load.
Can you confirm this please?
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I'm still wondering why you are bothering with dis Zo < 0R1 sh*t when you are using current drive in your speakers 🙂
________________________
BTW, Tom is right that you have some serious problems with your measurement setup including but not limited to grounding & earthing.
What soundcard are you using?
Has it got balanced inputs & outputs?
kgrlee, your description of the test method seems accurate. The curves I show are measuring two amplifiers using the same setup. I really cannot see how it would be a test jig setup issue. If it were, it would show up in both measurements.
But since I have found good correlation between the measured result and sound characteristic during listening, certainly looking at this data of the Mod86 will give me some idea what to expect.
But since I have found good correlation between the measured result and sound characteristic during listening, certainly looking at this data of the Mod86 will give me some idea what to expect.
I see. You are using a non-linear & heavily microphonic device to generate a a non-linear & heavily microphonic current to measure Zo.
On that basis, it is the MyRef measurement that is suspect.
and on top of that, Tom is right that you have some serious problems with your measurement setup including but not limited to grounding & earthing.
What soundcard are you using?
Has it got balanced inputs & outputs?
There's also excellent correlation between the rise in crime and the rise in sale of refrigerators. 😱
I think it is important to see how an amplifier responds to real load conditions which are more reactive. This is more realistic. From the measurements I see no issue with the setup as clearly the same setup measuring two amplifiers do not show similar issues. All I can say is Tom can decide on his own if he wishes to provide the data. Providing more information about my setup really will not change his mind.
Actually Soong, you have now provided enough information for us to put your measurements in their proper context.
The extra info I've asked for is in case you might want to address some of your measurement issues. eg the earthing on your Dynaco is obviously different from your MyRef and also how you've connected your measuring gear. Those versed in the art can deduce that from your measurements alone.
Your sound card and whether it has balanced in/outs determine how easy it is to sort out these problems but if you feel there are no problems, there is nothing else to be said. 🙂