Excursion related distortion in drivers is also due to the nonlinearity of the magnetic field in the gap. The use of copper rings to lower inductance will have a large impact on linearity overall, improving both THD and IMD performance.
so despite the wisdom of the larger personalities on this forum that thd and imd are insignificant how does one prove that they are insignificant to performance ....????
"insignificant" is an opinion. Improving the ability of a transducer to more accurately replicate the input signal is a measurable and audible thing.
Speakers from the 1930s don't sound as good for a reason.
Speakers from the 1930s don't sound as good for a reason.
linkwitz showed how to make a small wedge micrometer out of a small piece of paper to be used to measure cone excursion accurately
Well they are insignificant; if the are already insignificant (ie. low). Does that make sense?
People who say distortion doesn't matter are already low-enough distortion drivers; and that all depends on the design target.
It’s about SPL. Like if I want bass down to 50Hz at my ear; I can get away with a 1.5” if the driver is next to my ear (headphone/earphone)
But if I want life-like levels (80-100dB) in my home theatre room and I want everyone to hear it without headphones, if I’m sitting at 3m, or 30m, we’ll that that 1.5” driver won’t go far.
Earl did say that. But then again his smallest speaker is probably already an order of magnitude (10x) bigger as your typical consumer speaker that are selling by the thousands every day eg. Amazon, Sonos, in the store. It uses a Pro-sound 8” midwoofer; at a minimum. Ask him to design a speaker with a 4” driver and he will say it doesn’t go loud enough. Well it could; but it would just distort! Well that’s just the different side of the coin!
It’s like saying distortion doesn’t matter; but my smallest subwoofer I would use is multiple 18” inches, not 8”…
Why distortion matters:
Nonlinear distortion testing of loudspeaker driver units
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Celef, would it be better if I measured the voltage during the IMD test? excursion could be back calculated with modeling software.
I just recently tested the Dayton Epique E180HE-44 7" and I spliced the results with the Purifi PTT6.5X04-NFA-01 results I took a few months ago.
The Dayton Epique is an impressive driver it's IMD results are just slightly worse than the Purifi at a reduced cost. With it's dual voice coils it's also versatile. I ran it for a week as a computer sub with just one voice coil connected in a my .5 cu ft. sealed test box. In this setup it's modelled f3 is around 39hz, I found this to produce low bass with no danger of port chuffing which many small sub designs have. One impressive thing about the Epique was that I could get a 40 and 96hz IMD result at 90db, the Anarchy and Purifi were started to complain mechanically by this point.
To be picky the Epique had a issue in the 50hz and 210 hz IMD test when raising the volume from 80 to 90 db the level of the 210 hz fell around 2db lower than 50hz (see graph). I speculate that the inductance difference of the the long stroke required to hit 90db at 50hz is causing a low pass on the 210hz. I did not have this issue with the Purifi.
I tested the Epique with only voice coil driven and with both coils in series. I found voice coils in series to have lower IMD so that is what is in the graphs.
Special thanks to Chris Perez and Lars Risbo they are both very helpful and solid members of this group.
If the group has any driver testing requests or if you have something on the shelf you would like to have tested let me know. I'm on the lookout for a Wavecor SW182BD03.
The Dayton Epique is an impressive driver it's IMD results are just slightly worse than the Purifi at a reduced cost. With it's dual voice coils it's also versatile. I ran it for a week as a computer sub with just one voice coil connected in a my .5 cu ft. sealed test box. In this setup it's modelled f3 is around 39hz, I found this to produce low bass with no danger of port chuffing which many small sub designs have. One impressive thing about the Epique was that I could get a 40 and 96hz IMD result at 90db, the Anarchy and Purifi were started to complain mechanically by this point.
To be picky the Epique had a issue in the 50hz and 210 hz IMD test when raising the volume from 80 to 90 db the level of the 210 hz fell around 2db lower than 50hz (see graph). I speculate that the inductance difference of the the long stroke required to hit 90db at 50hz is causing a low pass on the 210hz. I did not have this issue with the Purifi.
I tested the Epique with only voice coil driven and with both coils in series. I found voice coils in series to have lower IMD so that is what is in the graphs.
Special thanks to Chris Perez and Lars Risbo they are both very helpful and solid members of this group.
If the group has any driver testing requests or if you have something on the shelf you would like to have tested let me know. I'm on the lookout for a Wavecor SW182BD03.
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Sorry for the wait Pida. but I was able to test a Wavecor SW182BD03. The Wavecor is a fun driver to listen to. It has a low loss suspension that will reproduce the attack of a kick drum well. This combined with a relatively high moving mass and stiff cone gives a good tactile feel to the bass. A natural competitor is the Anarchy. In listening tests I found the Wavecor to sound cleaner at reasonable listening levels but the Anarchy can get louder without blowing up.
I've added quite a few other IMD tests since my last chart.
I've added quite a few other IMD tests since my last chart.
if you do proper and accurate THD /IMD measurements, excursion is unintresting really - as I see it. If the IM is low it may "excurse" however it want - if it has high IM - low excursion don't matter to me anyways...
Excursion is mitigated with Sd if one has problem with doppler...
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Excursion is mitigated with Sd if one has problem with doppler...
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Are all the Epique images labeled correctly? Over 31 volts needed to hit 100dB@100Hz vs only 4.25V for the Purifi? I know the Epique is low efficiency and it's 8 vs 4 ohms, but that seems excessive.
shrub)> would be great to see the Misco 6502 compared to this round up: https://store.miscospeakers.com/6-5-xbl-2-high-excursion-ultra-low-distortion-woofer-82141 From Klippel comparisons I've seen, the motor is a bit better than the Anarchy, but the soft parts are much better optimized. Voice Coil shows considerably better HD performance compared to the E180HE, but I'm more interested in the IMD with changing SPL you are doing.
Thanks for the feedback Augerpro, I enjoy looking at your results on drivervault. Misco is actually down the road a few miles from me here in Minneapolis and I've been in contact with them about testing a 6502. Hopefully it works out.
I recently tested some Dayton RSS and RS 8" subs and woofers but it takes a while for me to compile the data.
I recently tested some Dayton RSS and RS 8" subs and woofers but it takes a while for me to compile the data.
7 times the voltage for drivers within 3dB sensitivity does seem unusual. Do you recall the duration of the testing?
The voice coil is definitely heating up. As I run a pure sine wave for a few seconds to adjust the levels. The Epique impedance curve is at it's lowest at 100hz as well.
Next up is a three tone IMD test. This is done in a similar fashion to the Linkwitz midrange distortion test. https://www.linkwitzlab.com/mid_dist.htm
There is a center frequency at 150, 300 and 800 hz for the three tests with side bands 1/10 times the center frequency above and below that is 5 db quieter.
I made a mistake and used 175hz above the 150hz but I have just used this from here on out.
Attached are graphs of the Dayton Epique and the Purifi in this test measurement conditions are the same as stated in post #1. This test shows that the Purifi is more suited for midrange duties than the Epique.
There is a center frequency at 150, 300 and 800 hz for the three tests with side bands 1/10 times the center frequency above and below that is 5 db quieter.
I made a mistake and used 175hz above the 150hz but I have just used this from here on out.
Attached are graphs of the Dayton Epique and the Purifi in this test measurement conditions are the same as stated in post #1. This test shows that the Purifi is more suited for midrange duties than the Epique.
Attachments
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Yes, I have been waiting for the Misco BWX-6502 to be tested, as well. It would be interesting to see how it differs from the Anarchy.
I have a Purify 6.5TT; if anyone is able to help me procure a Misco (they don’t ship to AU); I can do some comparative testing.
or send a pair to Yevgeniy @HiFiCompass
or send a pair to Yevgeniy @HiFiCompass
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I was able to pickup the Misco BWX-6502 on Tuesday. It is a little smaller than the Purifi so I will have to cut a new baffle for my test box. I then do a one week break in period and testing after that, so I hope to get some results posted here in a couple of weeks.