Audibility of low frequency distortion in speakers

[mcdn]

Not Spanish Harlem ? NNOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

I think the way to play it for bass tests is to LPF at 400Hz

 

[Mnyb]

The mask is the fundamental in this example.

View attachment 98485

Yes it certainly less audible with music as I mentioned above.

That was a very clear illustration , thanks

 

[March Audio]

A naive reading of that graph would be "play these exact tones aparft from those at 400Hz and 450Hz and you won't be able to tell it apart from a pure 100Hz tone". Is that what the source claims?

Essentially yes.

 

[Mnyb]

Not Spanish Harlem ? NNOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

Attend hifi demos much ?

 

[March Audio]

Attend hifi demos much ?

Just need Jazz At The Pawnshop to top it off.

 

[mcdn]

Essentially yes.

What's the source? Just checking whether it's a graphic illustration or a researched claim.

 

[March Audio]

What's the source? Just checking whether it's a graphic illustration or a researched claim.

Its just a crude illustration just to demonstrate the principles. I grabbed it some time ago I think from an article on the subject, i will try and find it.

 

[Mnyb]

Just need Jazz At The Pawnshop to top it off.

Being at the Pawnshop listening to Jazz live, is actually not so bad . listening to that recording out of context out of time at every trade show must sure become a joke eventually .
I get that feel when i hear "Money for Nothing" when i was 17 every hifi dealer and his brother was using Dire Straits to sell CD players

 

[March Audio]

This was another table I had grabbed.

Fielder and Benjamin study I believe

 

[March Audio]

Being at the Pawnshop listening to Jazz live, is actually not so bad . listening to that recording out of context out of time at every trade show must sure become a joke eventually .
I get that feel when i hear "Money for Nothing" when i was 17 every hifi dealer and his brother was using Dire Straits to sell CD players

Honestly I actually love the record, I have so many versions of it, but its almost like saying you like Genesis in public.

Is Stampen still a Jazz venue?

 

[Mnyb]

Honestly I actually love the record, I have so many versions of it, but its almost like saying you like Genesis in public.

Is Stampen still a Jazz venue?

I do like Genesis (especially selling England by the Pound).

Stampen is still a Jazz venue (and Blues ) I just hope they survive Corona .
I try to go there when in Stockholm .

The freaky and spooky thing with that recording is how it actually sounds like the venue and the limited resources it was done with, a couple of microphones and a Nagra IV ? I think it bit out of context as a demo disc . It's for local Swedish jazz fans in the 1970's and works very well at that . It's second life as hifi demo disc is a bit harder to get.
I have all 3 discs actually not just the first one

 

[March Audio]

I do like Genesis (especially selling England by the Pound).

Stampen is still a Jazz venue (and Blues ) I just hope they survive Corona .
I try to go there when in Stockholm .

The freaky and spooky thing with that recording is how it actually sounds like the venue and the limited resources it was done with, a couple of microphones and a Nagra IV ? I think it bit out of context as a demo disc . It's for local Swedish jazz fans in the 1970's and works very well at that . It's second life as hifi demo disc is a bit harder to get.
I have all 3 discs actually not just the first one

Toss up between Selling England and The Lamb for me

Ever tried air drumming along to Apocolypse in 9/8 (Foxtrot)?

 

[andreasmaaan]

@Mnyb that's what was confusing me, where is the masking tone? For dummies like me I'd love to have a sequence of test tracks like:
1) pure tone
2) pure tone with distortion profile X
3) pure tone with masking tone
4) pure tone with masking tone and distortion profile X
5) music programme (@mitchco likes a Rebecca Pidgeon track I think)
6) music programme with distortion profile X

Sorry I'm not sure if this was answered already. It's the "pure tone" that is the masker.

So let's say we play a 200Hz sine wave at 80dB with 10% 2HD and 3% 3HD. The masker will be the 200Hz sine wave, and the "maskees" (as they're called) will be the 2HD (which at 10% will be at 400Hz/60dB) and the 3HD (600Hz/50dB).

 

[mitchco]

Not Spanish Harlem ? NNOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

Haha. Not a fan actually. The only reason I use it from time to time is because I know the frequencies of the fundamental notes of the bass melody being played in its 1, 4, 5 progression: 49 62 73, 65 82 98, 73 93 110. Can be useful while listening and knowing what frequencies are being played.

 

[March Audio]

Haha. Not a fan actually. The only reason I use it from time to time is because I know the frequencies of the fundamental notes of the bass melody being played in its 1, 4, 5 progression: 49 62 73, 65 82 98, 73 93 110. Can be useful while listening and knowing what frequencies are being played.

I'm only kidding I play it myself.

Actually sounds like it could be a very useful track for looking for timbre changes due to distortion

 

[tvrgeek]

My experience completely reflects the basic premises and that one should strive to keep LF harmonics below 300 or 400. It is for this reason I am rebuilding my subs from sealed to BP-4 alignments to filter the harmonics, both electronic and mechanical. Then planning to upgrade my main drivers with more modern ones. From test results, it looks quite possible to get a end to end distortion below 2% across the entire audible range. 1 1/2 maybe if really careful.

I do note, seems the current implementation of class-D amplifiers do have rising distortion as frequency drops. Just saying as our friend here is a manufacturer of very sweet class D amps. It is actually reasonable to describe how this is not a bad attribute. When I first saw some graphs I was really wondering as the only "high end" class-D I had heard were the original Rotels and , well not impressed is being kind. As any dealer with decent modern equipment is at least 300 miles away, I have not heard the current generation. That is why I chickened out and bout yet another Parasound. Also looking at the graphs, I was able to understand how an amp spec @ 1% could he "hi-fi". Guess that is a standard from when Bose put them in cars. Kind of the same as specking a class AB at clipping. Advertising "500W @ 1%" I guess sells more than advertising "480W @.01%" People really are funny.

 

[andreasmaaan]

I do note, seems the current implementation of class-D amplifiers do have rising distortion as frequency drops.

What are some examples of this? In general, class D amps I'm familiar with do the opposite.

 

[March Audio]

So looking at this table at first it seems a little odd and inconsistent, however there are a few things to note which explain this.

As percent is probably what most are familiar with I will refer to those numbers.

First thing that catches my attention are the figures for 10Hz frequency. At a 100dB volume level 11, 2.2, 0.6 and 0.3% distortion for harmonics 2 to 5 respectively are required to be audible. Yet at 80dB volume 110, 22, 6 and 2.8% distortion is required. Seems odd to be that radically different but its not really.

Our hearing sensitivity changes with volume. We can see this effect if we look at the Fletcher Munson curves.

So at lower volumes the distortion simply needs to be relatively much louder before we hear it.

Second thing to note is how the effect of masking changes with volume. If we look at the figures for 100Hz frequency we see that at 80dB volume level, 1.6, 0.7, 0.4 and 0.22% are required to be audible, yet at 100dB volume level this increases to 3.2 , 1.8, 1.2 and 0.9%.

This is due to the fact that as the volume of the masking signal increases, so does its masking effect. Simply put, the louder the signal the more difficult it will be to hear the distortion.
This increase however is relatively small.

The table generally indicates that surprisingly low levels of distortion are audible with using tones. Tones are the worst case scenario, easiest to hear distortion. Music is different.

The first video I posted was a gross example with obvious distortion audibility. I will post another at much lower levels for interest.

Yes, as pointed out that isnt highly scientific, however the videos are the easiest way to demonstrate for most readers. Best will in the world relatively few will participate in the more scientific tests coming later.

 

[andreasmaaan]

So looking at this table at first it seems a little odd and inconsistent, however there are a few things to note which explain this.

View attachment 98582

As percent uis probably what most are familiar with I will refer to those numbers.

First thing that catches my attention arecthe figures for 10Hz frequency. At a 100dB volume level 11, 2.2, 0.6 and 0.3% distortion for harmonics 2 to 5 respectively to be audible. Yet at 80dB volume 110, 22, 6 and 2.8% distortion is required. Seems odd to be that radically different but its not really.

Our hearing sensitivity changes with volume. We can see this effect if we look at the Fletcher Munson curves.

View attachment 98583

That's interesting. I guess 10Hz is a special case in that the harmonics themselves need to be quite loud to pass the absolute threshold of audibility.

So at lower volumes the distortion simply needs to be relatively much louder before we hear it.

True, but only for a fundamental of 10Hz! At 20Hz, you can see that the thresholds stay relatively stable as SPL changes, and by 50Hz, sensitivity is already increasing as SPL decreases.

It's actually this latter trend that is true for most of the audio band at most SPLs, that is, at moderate and low SPLs, distortion needn't be as loud (even relatively) for us to hear it. Our sensitivity decreases as SPL increases.

 

[March Audio]

That's interesting. I guess 10Hz is a special case in that the harmonics themselves need to be quite loud to pass the absolute threshold of audibility.



True, but only for a fundamental of 10Hz! At 20Hz, you can see that the thresholds stay relatively stable as SPL changes, and by 50Hz, sensitivity is already increasing as SPL decreases.

It's actually this latter trend that is true for most of the audio band at most SPLs, that is, at moderate and low SPLs, distortion needn't be as loud (even relatively) for us to hear it. Our sensitivity decreases as SPL increases.

Indeed.