What's the point of floorstanding when we have subwoofers?

[Oddball]

ALL SUBWOOFER OWNERS — PLEASE READ THIS

Over the last week I achieved more progress in aligning my subs with my mains (and rear surrounds) than I had in the previous five years.

And I’ve tried everything: Audyssey MultEQ-X with custom PEQ filters, REW with a UMIK-1, different crossover frequencies, different phase settings… you name it.

But this week I did two major things:

1) I inverted the polarity of my subs from positive to negative in the SVS app.

Turns out this is not the same as applying a 180° phase shift. (If in doubt, ask AI why.) My Revel F208 speakers and subs were aligned in positive polarity when running full-range, but not when crossed over. Again, ask AI why a crossover often introduces an effective 180° shift (roughly +90° on the speakers and –90° on the subs). After inverting polarity, the sound improved A LOT.

2) I plugged the ports on my Revel speakers when crossing them over to the subwoofers. This also made the sound noticeably cleaner. I “lost” around 2 dB of bass between 50 and 140 Hz according to REW, but AI says that I am “not "losing" 2 dB of bass. You are successfully removing 2 dB of resonant, slow, boomy port bloat”. Like I said it definitely sounds cleaner and I am not hearing any less bass after plugging the f208 speaker ports when they are crossed with subs @60Hz.

I cannot begin to describe how much the overall sound improved. The bass is super tight - more massive but never overbearing. Just pure joy. (Of course, I still used PEQ on individual speakers, but I had done that before too.)

P.S. Audyssey cannot and thus will not flip subwoofers polarity for you even if needed, so that was the reason I was stuck. But AI says that Dirac Live Bass Control (DLBC) does this, and “it's the entire reason DLBC is a "magic" technology”. Or you can save a few hundred bucks and do it (at least try if you haven’t) like I did: manually.

(It’s kind of bewildering now that I see the effect to think that after so many years and so many millions of AVRs sold Denon have not incorporated this simple test for subs polarity in their auto calibration - which way subs play better with main speakers - and will rather do insane things like putting crazy distances to subs to try to compensate for polarity, and as an effect will create more problems and solve none)

If this helps your system as well, feel free to donate a like or something!

Did you check how that looks in REW? Phase shift might work better as you can control it more granularly to achieve the right balance. Also, if you have 2 subs, you might want to have one in phase and the other one out of phase. But also you might have just gone lucky and stroke the gold with the first tweak.

I would not ask AI anything complicated though. If feeds from forums mostly where people post all kinds of stuff and then you have AI hallucinating on top of that. Example would be that losing bass between 50 and 140hz should have nothing to do with the port on your Revels. They are also not so big to be crossed at 60hz - unless you have some humongous room gain. My 2c...

 

[Oddball]

It has always been all over the place. One example...

Low frequency harmonic distortion is almost inaudible. So what’s the point of low distortion drivers?

Putzeys, Dec. 2019

purifi-audio.com

But I don't overly care about the % we can universally agree upon. Just making the point complete linearity in extended bass shouldn't be something we obsess about.

50% THD in 20-40hz range? Then we must be really mad buying those bigger subs when a small subs could get us there in their SPL range?

 

[pablolie]

50% THD in 20-40hz range? Then we must be really mad buying those bigger subs when a small subs could get us there in their SPL range?

I have even worse news :-D
“For a 20 Hz tone, listeners tolerated up to 100% distortion before they complained about the sound.”

That is a direct, literal quote from a respected published source:

How Much Distortion Can We Hear With Music?

How much distortion can we hear with music? An experimental study at Axiom.

www.axiomaudio.com

 

[Oddball]

I have even wrote news :-D
“For a 20 Hz tone, listeners tolerated up to 100% distortion before they complained about the sound.”

That is a direct, literal quote from a respected published source:

How Much Distortion Can We Hear With Music?

How much distortion can we hear with music? An experimental study at Axiom.

www.axiomaudio.com

Not sure I or my neighbours would agree with 20hz point. But 40hz is one octave up?

EDIT: I don't really understand 100% distortion point. What that really means and what do you hear or not hear at that point? The way I would interpret it in layman's language that there is nothing you can hear from original signal so you hear - what?

 

[sigbergaudio]

Yes that is true but compared to below 200 Hz, above 200 Hz is a dream, both the actual output of the speaker and the way it interacts with the room.

What do you think the biggest above 200 Hz issues are? Even something like Neuman KH 80 or similar do very well over 200 Hz with on and off axis FR response and smooth directivity and even put out a fair amount of SPL above 200 Hz.

I'm not sure what your definition of "solved problem" is, mine is that basically every product in the category solves this problem well and solves it in a well known / predetermined way. This is not what we see.

High frequencies interact in a problematic way with rooms as well, I would say it's often even harder to control in a domestic environment. It also cannot be solved by EQ but must rather be solved with acoustical treatments, which can be easier or harder depending on your situation.

That a speaker measures well above 200hz does not necessarily mean that it solves above 200hz well in-room in real life situations.

 

[pablolie]

Not sure I or my neighbours would agree with 20hz point. But 40hz is one octave up?

EDIT: I don't really understand 100% distortion point. What that really means and what do you hear or not hear at that point? The way I would interpret it in layman's language that there is nothing you can hear from original signal so you hear - what?

The key takeaway is simple: our hearing is very tolerant of high distortion when it comes to bass. That shouldn't be news to anyone, really.

My personal take: if I play a 28Hz test tone (this is where my system reaches its +/-3dB) it's kind of a rumble, I have no idea what the reference would be. So my interpretation is that whatever true musical content of 20hz-ish tones is not particularly relevant, because it still seems to be there even when quite distorted. And that bass gets relevant structure and meaning and context because of other elements.

In the end, it's clear from threads like this we audio aficionados like our bass like we may like our steaks... we all have different preferences and different opinions on what matters and why. Bass-heads need not listen to me, because I have always stated sub-bass is not that important to me (nor is linearity at SPLs over 100dB, either).

 

[Oddball]

The key takeaway is simple: our hearing is very tolerant of high distortion when it comes to bass. That shouldn't be news to anyone, really.

My personal take: if I play a 28Hz test tone (this is where my system reaches its +/-3dB) it's kind of a rumble, I have no idea what the reference would be. So my interpretation is that whatever true musical content of 20hz-ish tones is not particularly relevant, because it still seems to be there even when quite distorted. And that bass gets relevant structure and meaning and context because of other elements.

In the end, ti's clear from threads like this we audio aficionados like our bass like we may like our steaks... we all have different preferences and different options on what matters and why. Bass-heads need not listen to me, because I have always stated sub-bass is not that important to me (nor is linearity at SPLs over 100dB, either).

Right - but that's not the perfect answer and sorry to grill you but would really like to understand the 100% distortion point. That seems to be the point where nothing is left so just interested what happens then. Have never been to the edge of flat Earth.

I am a bass head of some kind but not for infrasonics. Having great response at 20hz is still what I aim though.

Check my recent post and would be glad if you could contribute.

Let's see what you have under (and around) the hood - bass management and DSP challenge

In @ban25 `s post #8 in this thread, there’s an attached picture showing two KEF R3 speakers as SL/SR placed directly on the floor, which is in contradiction with the recommendation in the user manual at p. #11: “Always place the bookshelf loudspeakers on shelves or stands. Do not place them...

www.audiosciencereview.com

 

[Anton S]

Right - but that's not the perfect answer and sorry to grill you but would really like to understand the 100% distortion point. That seems to be the point where nothing is left so just interested what happens then. Have never been to the edge of flat Earth.
...

Does 100% distortion really imply that nothing is left or that the distortion components are of equal intensity to the signal?

 

[levimax]

but would really like to understand the 100% distortion point.

100% distortion means that the distortion products are just as loud as the fundamental. A simple case would be 100% 2nd order distortion of a 20Hz tone would mean a 40 Hz distortion tone is also generated which is just as loud as the 20 Hz tone. It's not that you would not hear the 20 Hz tone rather you would hear both the 20 Hz tone and the 40 Hz tone and yes it would sound both different and louder than a "clean" 20 Hz tone.

 

[Oddball]

100% distortion means that the distortion products are just as loud as the fundamental. A simple case would be 100% 2nd order distortion of a 20Hz tone would mean a 40 Hz distortion tone is also generated which is just as loud as the 20 Hz tone. It's not that you would not hear the 20 Hz tone rather you would hear both the 20 Hz tone and the 40 Hz tone and yes it would sound both different and louder than a "clean" 20 Hz tone.

Sorry, but still not getting it. Never dealt with a concept of 100% distortion so just curious. And will appreciate the help, although interest is purely academic. And why would they be louder that a clean 20hz?

 

[Oddball]

Does 100% distortion really imply that nothing is left or that the distortion components are of equal intensity to the signal?

Well in simple terms if your bank send you a statement that your investment account has been 100% distorted, means you have zero cents left, so game over. That's the common language. There is obviously more here but let's see.

 

[Marc v E]

Good to read that I'm not the odd one out.
Even though my speakers distort quite early in the bass region, it never bothered me in real life.

I do miss bass though if it's not there, like in most cars or even high-end monitors that cut of the bass quite early.

 

[Anton S]

Well in simple terms if your bank send you a statement that your investment account has been 100% distorted, means you have zero cents left, so game over. That's the common language. There is obviously more here but let's see.

That is a false analogy. It simply doesn't apply.

 

[pablolie]

Right - but that's not the perfect answer and sorry to grill you but would really like to understand the 100% distortion point. That seems to be the point where nothing is left so just interested what happens then. Have never been to the edge of flat Earth.
...

I am not sure what you mean with that. This is not my theory I need to defend, it's clearly widely understood in the audio world. You chose to interpret it negatively, but that's you - you might as well complain nature punhished us with limited 20Hz-20kHz hearing.

From what I can tell, the study seems well put together: They evaluated distortion thresholds at 20 Hz, 40 Hz, 80 Hz, 200 Hz, 1 kHz, and 10 kHz. They reported percentages of THD that listeners found acceptable before complaining. And the results align with well-known psychoacoustic masking curves and low-frequency sensitivity curves - that means the study underscores something that was already well known, it isn't a new scientific breakthrough.

Because the ear is extremely insensitive at 20 Hz, and harmonic distortion products fall into 40 to 80 Hz where masking is massive, humans often cannot distinguish 20 Hz distortion from the fundamental tone - even when the distortion exceeds the level of the fundamental. This is why many subwoofers show 30–50% THD at 20 Hz and still sound subjectively “clean.”

I am not trying to convert anyone here.

 

[levimax]

Sorry, but still not getting it. Never dealt with a concept of 100% distortion so just curious. And will appreciate the help, although interest is purely academic. And why would they be louder that a clean 20hz?

The reason it would sound louder is because you have all the sound energy of the 20 Hz fundamental tone plus all the energy of the 40 Hz distortion product playing at the same time. Harmonic distortion adds sound that doesn't exist in the original signal. I think the 100% is distracting you from the concept. Distortion could be even higher like 200% or 300% which would just mean the distortion products are playing louder than the fundamental.

 

[NTK]

Does 100% distortion really imply that nothing is left or that the distortion components are of equal intensity to the signal?

Depending on the definition. For definition 1 (IEC method), THD will never exceed 100%.

Source: https://www.ap.com/blog/thd-and-thdn-similar-but-not-the-same

 

[Oddball]

Depending on the definition. For definition 1 (IEC method), THD will never exceed 100%.

View attachment 491006
Source: https://www.ap.com/blog/thd-and-thdn-similar-but-not-the-same

Right - so that is what is making me confused. So what are we really talking about?

 

[pablolie]

Well in simple terms if your bank send you a statement that your investment account has been 100% distorted, means you have zero cents left, so game over. That's the common language. There is obviously more here but let's see.

I don't think it works that way. In your example, the distortion impacts your check book. In the 20Hz example, it clearly does not - you still hear 20Hz bass, it's just you can't identify high distortion in it. There is no negative side effect - mother nature decided that not hearing it is not a big issue for you.

It's more like our human inability to taste most amino acids. They simply have zero flavor. So adding twice the amount doesn't alter the flavor, since the quantity is not the reason why we can't taste that.

 

[Oddball]

I don't think it works that way. In your example, the distortion impacts your check book. In the 20Hz example, it clearly does not - you still hear 20Hz bass, it's just you can't identify high distortion in it. There is no negative side effect - mother nature decided that not hearing it is not a big issue for you.

It's more like our human inability to taste most amino acids. They simply have zero flavor. So adding twice the amount doesn't alter the flavor, since the quantity is not the reason why we can't taste that.

Now that is the interesting approach. You hear the signal distorted beyond recognition, you discard it and only hear the one that your are supposed to do?

No negative side effect brings us posts up - so we are mad to buy good subs?

 

[pablolie]

... so we are mad to buy good subs?

You said you're a bass head, so it's your god given right to hear bass as low and loud and distortionless as you want - and just like with any piece of audio gear, we're free to over-engineer to our liking.

Also, 20-40Hz is not the only thing subwoofers are for, and the correlation between bass frequency and our inability to detect distortion falls rather quickly as said frequency rises - I think 10-20% at 80Hz (we'd probably all pick 10% as the more desirable choice when buying a sub :-D).

I said I am not a bass head, but I own a good sub and invested time in integrating it into my environment - and to me that's foundational for my listening environment going forward.