What's Left In Speaker Design To Reduce Distortion/Increase Detail Retrieval?

[JohnnyAudio]

Focus on box and baffle design. Think like a piano or Stradivari violin designer.
Have you seen " The Red Violin"

 

[Curvature]

30% distortion is most likely below human hearing threshold

Not really. There aren't too many studies about masking thresholds below 200Hz. I'm sure practically speaking the numbers change a lot. Music is the best masker anyway. High in-room decay times help with that.

Subwoofers: a need for lower distortion?

Gentlemen, I've enjoyed our conversation. However while citing a mgfr website and Wikipedia, none of it refers to the paper I introduced in the OP. No one has read the paper. I'm not quite convinced that you've got my argument right as intended. Last chance? You measure a speaker and then...

www.audiosciencereview.com

Subwoofers: a need for lower distortion?

Gentlemen, I've enjoyed our conversation. However while citing a mgfr website and Wikipedia, none of it refers to the paper I introduced in the OP. No one has read the paper. I'm not quite convinced that you've got my argument right as intended. Last chance? You measure a speaker and then...

www.audiosciencereview.com

15Hz is inaudible

15Hz is the lower limit of tonal hearing. Below that the sensations are uneven and rough.

I have some papers on infrasound. Long story short there is no lower limit for bass sensation. It's just that the minimum sensation thresholds climb rapidly and sit well above 100dB SPL.

Reason I write sensation and not hearing is that other senses beyind just the ear kick in, although I've never been able to find papers with clear thresholds for that. I attended an AES conference where a haptics engineer was presenting, and his company had private, proprietary research about tactile thresholds. I wish more about the topic was available.

 

[cavedriver]

I think that's an important point to think about though. If distortion only becomes audible to the human ear at 30%(maybe this is why they landed on this figure for the CEA2010A spec?), then 10% distortion vs 5% vs 0.5% distortion shouldn't really matter other than for academic purposes. In some ways, it seems similar to me to the people chasing perfect SINAD in there DACs well beyond the limits of human hearing.

BTW, I don't know of any studies in regards to the audible thresholds of distortion at 10Hz, 16Hz, 20Hz, etc, but maybe others that are more knowledgeable can help with that. I pulled that 30% figure from reading this article , but I was to cheap to pay the $90 to download the actual spec, so maybe that's not exactly correct. It looks like there are actually two specs(A and B). I think the B is a little more accurate in regards to human hearing(ie it allows more distortion before test fail at lower frequencies), but I'm not certain of that either.

Just to add my .02, I have the feeling I've read that our sensitivity to distortion declines as we go down in frequency below ~40 Hz, but I don't have a specific reference to base that on. But it would make sense given that in the range of around ~30 Hz we stop experiencing sound as "tones" that can be judged for their accuracy like musical instruments can be at higher frequencies. Once you lose the sensitivity to tone how would our brains interpret an inaccuracy in physical vibration? Idk.

edit: reading Curvature's post above, 15 Hz? really? I personally don't feel like I experience tone below about 30 Hz, maybe some people can. It does make me wonder - usually one encounters stable examples of those frequencies in the form of test tones, while examples of organ music and other stable low tones are less common. I don't know how much of an organ's character is overtones so it may be hard to use one to judge the limit of tonal hearing, but in the test tones is where I'm not hearing a tone.

 

[Curvature]

Just to add my .02, I have the feeling I've read that our sensitivity to distortion declines as we go down in frequency below ~40 Hz, but I don't have a specific reference to base that on. But it would make sense given that in the range of around ~30 Hz we stop experiencing sound as "tones" that can be judged for their accuracy like musical instruments can be at higher frequencies. Once you lose the sensitivity to tone how would our brains interpret an inaccuracy in physical vibration? Idk.

edit: reading Curvature's post above, 15 Hz? really? I personally don't feel like I experience tone below about 30 Hz, maybe some people can. It does make me wonder - usually one encounters stable examples of those frequencies in the form of test tones, while examples of organ music and other stable low tones are less common. I don't know how much of an organ's character is overtones so it may be hard to use one to judge the limit of tonal hearing, but in the test tones is where I'm not hearing a tone.

Collection of listening test results for thresholds.

If you read the individual papers there are notes from listeners about what 10Hz feels like, etc. As far as I understand below 15Hz you hear whooshing, rushing, things like that.

 

[richard12511]

Not really. There aren't too many studies about masking thresholds below 200Hz. I'm sure practically speaking the numbers change a lot. Music is the best masker anyway. High in-room decay times help with that.

Really? That's honestly surprising. I wouldn't have expected 30% to be audible at such low frequencies. I thought I remembered seeing a chart somewhere at some time that showed even like 60%+ wasn't audible down there at 20Hz, but it seems my memory has failed me. I chose 30% since that's what the CEA2010A spec seems to use as their pass/fail threshold. I do know the B spec is different, but iirc it allows an even higher % fail threshold down there. Maybe someone who already owns the spec can clarify on the B pass/fail thresholds?

Subwoofers: a need for lower distortion?

Gentlemen, I've enjoyed our conversation. However while citing a mgfr website and Wikipedia, none of it refers to the paper I introduced in the OP. No one has read the paper. I'm not quite convinced that you've got my argument right as intended. Last chance? You measure a speaker and then...

www.audiosciencereview.com

Subwoofers: a need for lower distortion?

Gentlemen, I've enjoyed our conversation. However while citing a mgfr website and Wikipedia, none of it refers to the paper I introduced in the OP. No one has read the paper. I'm not quite convinced that you've got my argument right as intended. Last chance? You measure a speaker and then...

www.audiosciencereview.com

At 4.8%, or ~2.4% - on the newer models - @20Hz(110db), the JTR sub is cutting it pretty close to audible amounts of distortion according to those charts. Maybe the servo technology is indeed a worthwhile pursuit, even down there. The servo Rythmik sub is at 1.5%, which allows for some breathing room.

Thanks for the links. You've given me another fun thread to read through

15Hz is the lower limit of tonal hearing. Below that the sensations are uneven and rough.

I tried this a few years ago with a 20Hz signal at really high volumes, but I remember feeling it more so than hearing it. I think my ability to hear tone stops somewhere in the 20-30Hz range. That said, it doesn't surprise me that other humans can hear it, since our physiology can differ quite a bit.

I have some papers on infrasound. Long story short there is no lower limit for bass sensation. It's just that the minimum sensation thresholds climb rapidly and sit well above 100dB SPL.

I can attest to this. There's a note in a pop song I tested with that's way down there(maybe even sub 10Hz) that you can feel at high enough spl. My guess is it made it on the track by accident, as it *feels*(hard to tell) like it's almost exactly an octave below the already super low note that's been playing on the track. I've got some floorstanders that are -3dB at 23Hz, and I can't feel it on those. It's only there when I run the subwoofer system, and only at super high spl. It feels kinda like dropping on a rollercoaster for a split second, and then it's gone. The wave is big enough that you can kinda feel it's rythm, or at least that's the way my body perceives it.

Reason I write sensation and not hearing is that other senses beyind just the ear kick in, although I've never been able to find papers with clear thresholds for that. I attended an AES conference where a haptics engineer was presenting, and his company had private, proprietary research about tactile thresholds. I wish more about the topic was available.

Would definitely love to see more research on the topic

 

[richard12511]

Do Velodyne still use the active feedback/feedforward distortion reduction mechanism, or have they abandoned it?
I can see no mention of it on their website.

I feel like at one point they built an F1 racer, but the market was limited so they dropped back to making trucks, as that is what there is the biggest market for!

I remember some mention of this on this site, but just barely, and I could be mistaken. I can't say I remember the company name, but in regards to motion feedback in F1, it does ring a bell. Maybe @Frank Dernie mentioned it?

Were the vintage velodyne claims, just marketing snake oil? or was there a better mousetrap made, that nobody needed?

Good question. 0.1% at 20Hz or below at high spl seems really hard to believe if we're talking reference level, but maybe it's possible. As JP from Angels in the Outfield would say "It could happen" .


There is in fact a disclaimer on the Velodyne measurements page: https://data-bass.com/#/systems/5b11c4aea201f10004e39d6b?_k=ol4zom under the distortion tests section.

"There have been some suggestions that the DD18+ distortion levels deflate Velodynes claims. Distortion test results will vary greatly depending on the drive levels used and the environment the subwoofer is in. In room the deep bass distortion is usually going to be reduced tremendously due to boosting of the fundamental frequencies relative to the harmonics. If you want to compare distortion results from subwoofers compare them to only those measured in the exact same manner. In other words compare Data-Bass results to Data-Bass or at minimum other ground plane results. Otherwise it will not be apples to apples in any manner. Looked at in that light compared with other sealed subwoofers and subwoofer alignments measured in a similar manner, the DD18+'s distortion results are good but not stellar in the deep bass range. As far as validating their claims of 1% THD under typical use I'm doubtful but as we have no way of knowing what Velodyne considers typical output levels and what environment the subwoofer might be in at the time, it is impossible to do that. Also consider that there are a lot of other offensive noises that speakers emit when driven hard in a reflection free environment that do not show up on harmonic distortion charts. The DD18+ was completely free from any of those mechanical or operational noises."

 

[Curvature]

Really? That's honestly surprising. I wouldn't have expected 30% to be audible at such low frequencies. I thought I remembered seeing a chart somewhere at some time that showed even like 60%+ wasn't audible down there at 20Hz, but it seems my memory has failed me. I chose 30% since that's what the CEA2010A spec seems to use as their pass/fail threshold. I do know the B spec is different, but iirc it allows an even higher % fail threshold down there. Maybe someone who already owns the spec can clarify on the B pass/fail thresholds?

I can't remember the numbers. The A thresholds are based on fairly old hearing research and have limits per harmonic.

The thing to remember is that these tests use a burst signal. So thresholds will be elevated vs. a continuous sound.