So brain failing as usual on the name front. Malcom Hawksford was the lead on this one. But here it is.
A thin wire gauge is probably hitting some hard limits on manufacturability. So an extra long coil, and/or high diameter and rated for high power, is also easier to put together and more robust.
I disassembled my old 250 ohm Beyerdynamic headphones awhile ago. The near invisible gauge was amazing. IIRC, they did add a few ohms to balance the gain, so it was probably around 240 ohms, which is still very impressive for a ~10mm coil on a 30mm driver.
I disassembled my old 250 ohm Beyerdynamic headphones awhile ago. The near invisible gauge was amazing. IIRC, they did add a few ohms to balance the gain, so it was probably around 240 ohms, which is still very impressive for a ~10mm coil on a 30mm driver.
Well no: obviously no-one wants to overdo it. But if auditioning performance is benefitted by raising the amplifier's output impedance, then in my understanding the driver is not optimised for voltage drive, per se. Maybe it's pedantic and semantics, but I also think it may be misleading to suggest that "voltage-oriented" design effort has gotten to a point that going the extra mile with current-driven amplifiers is unrecommended for the "average" mid-woofer / mid-range or tweeter. Perhaps the recommendation should be more that current-drive could break things if you're not careful to avoid certain known pitfalls.
Well I am looking at it from an adoption perspective. Every woofer I've seen can be improved with current drive above Fs, but I know some exist that don't improve much or at all. I can use current drive in any of my projects if I want to because I know how and I can get the parts, but that doesn't automatically mean a business would survive the venture.
Thank you, but in the end I'm pretty sloppy and it is others who have the ability and resources to make hard advances. The best I can do is light my part of the road, but it usually only serves my own entertainment. And only as long as I can avoid saying something dumb on the internet.
Let's wind up the SPL for: 94dB @100Hz ~1m:
VOLTAGE DRIVE-
20V driven with 20ohm resistor in series, equalised for the same response.
Another view:
3.17V driven directly:
20V driven with 20ohm resistor in series:
Appendix: Impedance sweep with and without resistor in series.
CONCLUSION: LOWER HARMONICS, CURRENT DRIVE SHOWS PROMISE.
VOLTAGE DRIVE-
20V driven with 20ohm resistor in series, equalised for the same response.
Another view:
3.17V driven directly:
20V driven with 20ohm resistor in series:
Appendix: Impedance sweep with and without resistor in series.
CONCLUSION: LOWER HARMONICS, CURRENT DRIVE SHOWS PROMISE.
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HYPOTHESIS : Current drive can mitigate motor induced harmonic distortion, from H2 to H5 (and beyond- not shown), but cannot mitigate Sd modulation, which happens when excursion are significant ie. >1mm.
Thanks for the effort. May I sugest the use of "Overlays" with a particular harmonic ("Measure to plot") to be displayed for the different setup versions (EQ, non EQ, V or I drive etc) in one and the same graph for an easier evaluation?
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Is the 1mm excursion some kind of universal constant or is this limit different for different drivers ? If the latter is true then what fraction of Xmax is 1mm in this case ?
I use 1mm as an example of a small figure.
In practice, as the cone moves further backwards and forwards, non linearities of soft moving parts start to creep in and become more significant.
In the past it’s seems the surround was ignored. But the spider is also a moving part of the speaker, and has also been ignored by some manufacturers. Perhaps ignored is a harsh criticism, but certainly some pay more attention and some pay less attention to optimising them.
These distortion measurements so far continue to be consistent with past commentary- such “if you can see your speakers moving it’s distorting” and the preference for large woofers over small woofers. So we are not discovering anything new.
But as DIYers we probably need to learn to look at manufacturer data-sheets better, and inspecting drivers a bit better, rather than fawning over some fancy new shiny cone or phase plug. Like some, I’ve also been guilty of this, instead of paying attention to things that do matter, like a l smooth and linear frequency response AND impedance response over the anticipated range of the driver.
It’s impossible to acquire and measure everything
In practice, as the cone moves further backwards and forwards, non linearities of soft moving parts start to creep in and become more significant.
In the past it’s seems the surround was ignored. But the spider is also a moving part of the speaker, and has also been ignored by some manufacturers. Perhaps ignored is a harsh criticism, but certainly some pay more attention and some pay less attention to optimising them.
These distortion measurements so far continue to be consistent with past commentary- such “if you can see your speakers moving it’s distorting” and the preference for large woofers over small woofers. So we are not discovering anything new.
But as DIYers we probably need to learn to look at manufacturer data-sheets better, and inspecting drivers a bit better, rather than fawning over some fancy new shiny cone or phase plug. Like some, I’ve also been guilty of this, instead of paying attention to things that do matter, like a l smooth and linear frequency response AND impedance response over the anticipated range of the driver.
It’s impossible to acquire and measure everything
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Yeah, that was my first observation on your first post of the day, that it apparently did not help with even order distortion down low. The XXLS' surround is pretty large and has quite a bit of mechanical loss - this is probably dominant over any S_D variation. The spider is flat and should be fairly linear, at least at +/- 1 mm. I'd hazard that the air spring in a 27 l CB makes a relevant contribution, too.
This serves to show that in a subwoofer, one needs current drive and MFB...
This serves to show that in a subwoofer, one needs current drive and MFB...
So zero damping factor has some application. I wonder about the amplifiers ability to sink current. I really have never even thought about this before now. The reason why there is generally a different frequency response on a driver is related to there being a an amplifier driving the loudspeaker with a secondary impedance. When you think you know something, you find out you need to know more.
Current drive seems to have no effect on the PTT6.5X04NFA.
I suspect the massive copper sleeve and variable winding voice coil is responsible for this:
How about an other question: How does these compare....
Wrt to distortion?
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- Bare driver - why not a SB15 or SB17....
- Driver with a low ohmic inductor in series where the inductance makes up for a low pass at say Fo = 1k
- Driver again with same inductor but DSP compensated to retain original FR.
Wrt to distortion?
//
Well heat up the copper sleeve and take it off, reassemble and measure again.
I can simulate it with and without the copper. But there is nothing as good as making actual tests.
@TNT
My hypothesis goes something like this-
A bare driver like an alu cone with a full copper sleeve eg. SB15/17 N(B)AC may not minimal to no real improvement.
I have the SB17NAC-04 here so one fine day...
b) A driver with one (or two) air cored inductor in series will show some improvement. The level of improvement may depend on the total series resistance and how much it linearizes the impedance.
I have the Scan-Speak 18W/8535 with the SD-1 (3 copper rings) as part of the ProAc Response 2.5 clone, with 3rd order low pass filters using 2 air core series inductors, so one fine day...
c) To linearize the response back to original response without the inductor. Why would one want to do that?
2.
@Kravchenko_Audio
Dear Mark,
I agree.
In theory, there is no difference between theory and practice. But in practice, there is.
( Benjamin Brewster)
Unfortunately I will not be able to do that experiment. That picture is an old one, after I had to repair a damaged driver. I've since reassembled it, and it's in a completed speaker now. I won't be disassembling it again.
Re: simulation vs observation-
That reminds of the time I wrote to @jackocleebrown at ASR
https://www.audiosciencereview.com/.../kef-r-meta-series-release.41420/post-1487851
asking why he didn't have a fully copper sleeve in the TOTL Reference/Blade META drivers ie. coax and woofers.
He was curious and wrote to me directly. We compared notes. With thanks @5th element
In the end we did not reach a consensus. But we stand by our research and I shared with him our findings*.
Hopefully we can look forward to the next generation KEF Reference/META UniQ transducers to have even lower distortion from the MF unit. (IMHO the HF is already top of the class. He did complete a PhD on Phase Plug Design for compression drivers and applied that knowledge when he went to work for Celestion, and KEF, both subsidiaries of (OEM battery giant) GP (Gold Peak))
Full disclosure: "*In the interest of transparency, we confirm that no financial compensation, funding, or material support was exchanged in relation to the research findings presented. All conclusions and interpretations are based solely on objective analysis, independent data assessment, and professional integrity. This disclosure underscores our commitment to unbiased inquiry and the ethical dissemination of information."
My hypothesis goes something like this-
A bare driver like an alu cone with a full copper sleeve eg. SB15/17 N(B)AC may not minimal to no real improvement.
I have the SB17NAC-04 here so one fine day...
b) A driver with one (or two) air cored inductor in series will show some improvement. The level of improvement may depend on the total series resistance and how much it linearizes the impedance.
I have the Scan-Speak 18W/8535 with the SD-1 (3 copper rings) as part of the ProAc Response 2.5 clone, with 3rd order low pass filters using 2 air core series inductors, so one fine day...
c) To linearize the response back to original response without the inductor. Why would one want to do that?
2.
@Kravchenko_Audio
Dear Mark,
I agree.
In theory, there is no difference between theory and practice. But in practice, there is.
( Benjamin Brewster)
Unfortunately I will not be able to do that experiment. That picture is an old one, after I had to repair a damaged driver. I've since reassembled it, and it's in a completed speaker now. I won't be disassembling it again.
Re: simulation vs observation-
That reminds of the time I wrote to @jackocleebrown at ASR
https://www.audiosciencereview.com/.../kef-r-meta-series-release.41420/post-1487851
asking why he didn't have a fully copper sleeve in the TOTL Reference/Blade META drivers ie. coax and woofers.
He was curious and wrote to me directly. We compared notes. With thanks @5th element
In the end we did not reach a consensus. But we stand by our research and I shared with him our findings*.
Hopefully we can look forward to the next generation KEF Reference/META UniQ transducers to have even lower distortion from the MF unit. (IMHO the HF is already top of the class. He did complete a PhD on Phase Plug Design for compression drivers and applied that knowledge when he went to work for Celestion, and KEF, both subsidiaries of (OEM battery giant) GP (Gold Peak))
Full disclosure: "*In the interest of transparency, we confirm that no financial compensation, funding, or material support was exchanged in relation to the research findings presented. All conclusions and interpretations are based solely on objective analysis, independent data assessment, and professional integrity. This disclosure underscores our commitment to unbiased inquiry and the ethical dissemination of information."
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Give me a few days. I already owe Steve Mowry a simulation of the Borreson driver. When that is up and running I'll tackle this.