What explains better/stronger perceived bass when the frequency responses are identical?

The title sums it up. We all know that some amps produce better bass while they measure flat pretty much like every other amp starting with the cheapest receiver. Why do you think that is? What's the factor at play?

 

There's also the fact that headphones that measure with similar bass levels or even *higher* levels can still sound weak and lifeless.

 

Added harmonics and low damping factor can both affect the bass sound.

 

I heard the teory that lower DF can sound better with some speakers. Is that what you mean? Alos, do we know if thee's some distortion profile that improves the bass? I remember reading once that mids/highs distortion can alter the perception of bass.

 

If you subscribe to the notion that 2nd and 3rd order harmonics can be pleasurable distortions, it might help to think about what those distoritions actually do to affect a sinusoidal wave. This is all kinda handwaving in terms of relating to subjective perceptions, but a 2nd order distortion blunts the waveform, effectively smoothing the fundamental and extending it in the time domain. A 3rd order harmonic moves the constructive distortion forward in time and essentially sharpens (increases the rate of change of) the transient. Combining the two orders in various magnitudes can potentially increase perceived "quickness" (3rd order) and/or "fatness" (2nd order). However, in amplifiers we're talking about levels around -40 to -50dBu/1%-.05% THD.

 

@yotacowboy not of a fan of fat bass - comes off as fuzzy to me once I heard skinny bass

The 3rd order thing is interesting. Do those characteristics apply to higher order harmonic distortions (e.g. 6th order is a bit fat and quick, 4th twice as fat, 9th triple fast)?

 

The phase of the distortion matters for how the waveform looks. I wonder if it changes the sound.
For example amplifier distortion and transducer distortion may be in opposite phase.

 

Coincidently a few days ago while fine tuning some cabling work I thought about what would cause one cable to have less microdynamics and 'energy' in lows vs another.
Making playing field equal by removing the obvious variations - resistance, capacitance, inductance; massive question marks still remain.

Seasoned SBAF people know, there are significantly different ways how bass is handled by dacs- all this frequency response, SINAD and THD can be binned, these explain nothing as all competent DACs have these properties order of magnitude or more above the threshold that would matter for our hearing.

With amplifiers I sort of know what causes one to have great bass and other not so great on construction/design level - but the mechanisms of this 'distortion' are not so clear to me on concise mathematical level. As of now I would not know what to measure - that would be specific to that effect.

With DACs it is even less clear to me, but it has probably a lot to do with the filtering and sampling on top of analog circuitry and the dna and stacking (paralleling) of the architecture.

My thoughts are it has something to do with microdynamic and pitch (perhaps even timing) resolution. Our hearing is not that great at dissecting dynamic graduations in highs at narrow pitch ranges, as the spectra is so dense - on the contrary bass tones would be boring if it wasn't for the fine graduations in pitch and microdynamic. My thought is this explains the bass thing to some extent. Lack of strength in this would leave the bass feeling hollow and weak, no meat!
The ones who have played with the early days of DAWs (like Fruity Loops) or early soft synths know, the bass sucked on these instruments compared to analog or mic'ed acoustic instrument. The simple archaic soft synth likely had not enough correct content (data bandwidth) to have perceptible substance, to have meat!

Some people have found correlations with second and third harmonics. This could be incorporated in the above hypothesis - second or third harmonic would add stuff to the bass in that it would selectively fill (or delete, depending on phase) the dynamic spectra and pitch graduations.
The systems that I know to have significant 2 and 3 harmonic distortion in bass range feel sloppy or veiled to me - not more 'dense' or 'meaty' vs similar systems that have insignificant levels of these distortion components.

 

Fun vid to add to the confusion;

It's aimed at live production, but there are some great visual aids I'm sure a few of us can appreciate.

 

I'm an idiot so take my opinion with a grain of salt.

I think the decay of the lower frequencies has something to do it. I believe you could see this in a CSD/waterfall plot.

 

I think you'd be less an idiot than me cuz this makes sense. I've been playing with cheaper IEMs lately cuz those have gotten remarkably good in recent years (I just wish they didn't all gravitate towards the same upper-mids heavy voicing AAAAGH) and a friend was recently sponsored by this brand called Tangzu which elicited some curiosity on my part. I'd owned the Salnotes Zero:2 that lots of folks here like but gave them to my kid brother cuz the voicing was too fatiguing for me, and I think the BIG bass was a big part of that (because otherwise the FR is almost exaclty the same from the low mids up to the mid treble).

Here's a spectrogram of the Wan'er Studios (which with some different tips I actually enjoy) up top with the Zero:2s on the bottom. Normalised peaks to frequency and this tracks with my perception of the low bass of each; the Tangzus are honestly a bit weak in the bottommost octave but the Salnotes on the other hand make my eyeballs and throat ache a bit when something very low-bass heavy comes on.

Note the absolute SPL bar on the right. I do think my SPL calibration was messed up with the Zero:2 measurements cuz I recall just barely avoiding clipping during measurements, those ought be higher. Measurements of the Zero:2s are from March this year, will need to see if I can borrow them to re-measure some time.

Wan'er Studio


Zero:2

 

You could look at the group delay instead. Basically the deeper the extension, the less delay there will be.

 

Interesting. What would good vs bad group delay look like?

 

Personal experience + science makes me think a lot of it is the current delivery capability of the amp. More current produces a stronger electric field around the wire, which *should* cause the alternating EM field emitted by the voice coil to react more strongly to the static field from the magnet. Damping factor should dictate the quality of that bass. My two cents, but I'm no expert.

 

So louder is better?

For speakers I think it helps to be close to minimum phase. Laggy bass and bad pitch differentiation can be the result of phase shift.

This also means closed box should rule. But in my experience it's not so simple. Closed box with good extension usually means very large boxes. Which are often not feasible. Large and low tuned is much easier to do.

Another thing is the crossover part quality. And it's not just the quality of the inductors that play a role here, the capacitors play a major role here, too.

 

Not louder, better control while you're using an alternating EM field within a static EM field to move the cone and air. I'm thinking of this from a physics perspective. You need enough power (current) to push against the woofer's EM field and move the cone/air. The stronger the alternating EM field, the more easily, quickly, and accurately it should move the woofer and push/pull the air in the room.

Like a car with more power, the higher current/power should allow the woofer to accelerate more like the tweeter helping to maintain the phase relationships on something like a rock kick drum which prominently has both ~80 Hz and ~2.5 kHz components. This ties in with your phase angle. Pun intended.

I completely agree that a sealed box sounds best, unfortunately the market provides few high quality options (and they all seem to have hard domes, which I don't like). They also measure differently than other bass loading methods.

Your comment about sealed speakers and enclosure size reminded me of something from 30+ years ago - add a 12 dB/octave boost in the crossover where the speaker starts its' 12 dB/octave roll-off. Bag End made a ton of subs on this principle back in the day (E. M. Long was a smart cookie who came up with the idea, his speaker company was Calibration Standard Instruments). Might be fun to make a LS3/5A clone on this principle without a high pass filter and see how far you can launch the woofer with a ~5 Hz impulse and a couple thousand high current Watts.

 

Since some people were asking how do harmonics affect the waveforms, here is a simplified spreadsheet where you can punch in some numbers and see how that changes the shape of the sine wave:
https://www.dropbox.com/scl/fi/2c45...ied.xlsx?rlkey=w5g3wicizs4xibdgubg83iv7l&dl=0

It's an excel file, you may need to download it to be able to edit.

edit: I forgot I also have a google drive version:
https://docs.google.com/spreadsheet...ouid=102821999456903661246&rtpof=true&sd=true

 

I was listening a mixing podcast where they artificially added 2nd and 3rd in a way to greatly increase the perceived loudness of the 1st. Why? Suppose the pedal tone is 30 Hz - on most systems it's barely audible. However, adding 60 Hz and 90 Hz makes the perceived sound at 30 Hz much louder.