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Deleted member 375592
Hallo Michael
Thank you for all your measurements. These measurements are a bright highlight for me on diyAudio.
What is extremely interesting is that just 5dB less SPL makes the avalanche problem practically disappear.
At 75dB SPL with the 12R and 24R series resistor there is sweet nothingness.
At 80dB/24R hell breaks loose.
The
looks very good
Best regards
Bernd
Thank you for all your measurements. These measurements are a bright highlight for me on diyAudio.
Here I see the collapsing saturation of the iron parts. High SPL needs high current in the voice coil. This high current demagnetizes the iron pole piece. The flux in the iron breaks down in avalanches.
What is extremely interesting is that just 5dB less SPL makes the avalanche problem practically disappear.
At 75dB SPL with the 12R and 24R series resistor there is sweet nothingness.
At 80dB/24R hell breaks loose.
That is like me postulating: Long live the 20R series resistor ;-)
The
looks very good
Best regards
Bernd
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On the graphs, which is the ferrite and which is the neo version of the same driver?
Sorry, but it's not clear to me.
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Deleted member 375592
Marked "SB12CAC-R" - ferrite, "DM75A-R" - neodymium. Not the same driver, the first is SB Acoustic SB12CACS, and the second is HiVi Research D7500, R is a series resistor, generally equivalent to the depth of the current drive feedback loop.
It's still apples to oranges comparison in some way, because the 4 Ohm version SB12CACS have a nominal voltage sensitivity of 88dB and the D7500 have 94dB. This means that 4x electrical power needed for the SB for the same SPL as in the case of the HiVi. That's a lot of difference.
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i doubt that ferrite and neo are much different. They are both fully saturated and free from hysteresis and Barkhausen. Its the iron and how much copper shorting there is
Two off-topic questions: What is the correct term to name this "Mozart-Real-Music-Input-Signal" measuring method? And where is it desctibed more in-depth?
And another question, maybe slightly more on-topic, but rather for fun and last not least for the sake of apples vs. oranges: Does this midrange bunch show the same values/ranking when measured with a different input signal, e.g. such as with Gustav Holst / Planet Mars, Ry Cooder / Paris Texas, Klaus Schulze / Cocooning or John Cage / Branches?
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Hallo Lars
[...] It’s tempting to do so (as some do) by using a bigger magnet to saturate the pole. That works, but only at low signal levels. For any realistic magnet, it won’t take much drive current to take a saturated piece of iron back out of saturation. [...]
[ https://purifi-audio.com/blog/tech-notes-1/some-speaker-problems-that-needed-solving-1 ]
This is proven by @mikets42 measurements.
Best regards
Bernd
It is certainly true that the magnetic material has no influence. At least as long as one builds classic dynamic drives with ring magnet, top plate, bottom plate and iron pole piece. With the voice coil wrapped around the iron pole in the center.
So you personally support the ubiquitous saturation myth ?
[...] It’s tempting to do so (as some do) by using a bigger magnet to saturate the pole. That works, but only at low signal levels. For any realistic magnet, it won’t take much drive current to take a saturated piece of iron back out of saturation. [...]
[ https://purifi-audio.com/blog/tech-notes-1/some-speaker-problems-that-needed-solving-1 ]
This is proven by @mikets42 measurements.
Best regards
Bernd
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Deleted member 375592
I developed a mathematical instrument that can also be used for the analysis of LTI distortions. I tested it on a collection of real drivers on real music (I happen to like) and presented the results. That's it.
1. see the "Do measurements matter for sound" thread.
2. Of course not. It's way more complicated. Ferrite is not one specific material, it's a class of magnets, each one with its own specific composition, chemistry, and technological process. Same for neodymium. The same way of thought for music.
I do not have a complete collection of all drivers ever produced. I do not have time (no desire) to test all of them on all kinds of music. There is music that I can listen to hundreds of times in a row, and others (like Cage), that I can not listen to even once. Based on the limited sample size, I noticed some trends and came to certain tentative conclusions, see above. Well, maybe they are invalid generalizations. Try by yourself, and add the results of your testing to the pool of knowledge.
I don’t believe in myths. I was talking about the magnet material it self and not the rest of the motor. A permanent magnet is fully saturated almost per definition.
yes. I happen to be coauthor of that article😀
cheers,
Lars