tl;dr -- aside from the point about fuel, you mostly don't disagree with him. You have different definitions for the same terms he uses, and you draw your system in a different place than he draws his. Both of you make reasonable choices. A youtube video is not an academic paper, and cannot start by rigorously defining the system under discussion.
> he called oxygen the fuel for the fire... it's not the fuel for the fire
I think you're correct here, from chemistry definitions oxygen is not fuel, because breaking its bond consumes energy rather than releasing it. However, I don't think the host is trying to give perfectly precise chemistry definitions here, he's trying to explain how fire burns, and calling oxygen 'fuel' makes it clear to his audience that oxygen is required for combustion. I think your objection here is similar to objecting that voters in the US elect electors rather than candidates -- it's correct, but not necessary if you're explaining the concept of democracy.
> the port actually decreases the efficiency of the speaker by letting the negative bass note sine waves cancel out the positive sine waves from the front of the speaker, but this is done to tone down the "boominess" of the speaker at its resonant frequency, thus making the speaker more "neutral" sounding
I don't know much about bass reflex speakers, but I read the wikipedia page in decent depth, and it appears to me that you are wrong, or perhaps using a different definition than the field itself uses. From the wiki page: "This port enables the sound from the rear side of the diaphragm to increase the efficiency of the system at low frequencies as compared to a typical sealed- or closed-box loudspeaker or an infinite baffle mounting... Depending on the exact relationship between driver parameters, the enclosure volume (and filling if any), and the tube cross-section and length, the efficiency can be substantially improved over the performance of a similarly sized sealed-box enclosure." [0]. I bet I can see where your disagreement comes from though -- I think you're arguing that adding the reflex speaker cancels some of the power going through the main speaker, and therefore must result in decreased total_power_out/total_power_in (forgive me if I misunderstand). This is a sensible way to define efficiency, and I think you're correct that total_power_out is strictly decreased. However, there are also other sensible ways to define efficiency, eg, instead of total_power_out you might care about the perceptually-weakest frequency the speaker generates, to ensure the sound is "balanced" to a human ear. You might then define efficiency as num_spectral_bins*min_weighted_spectral_power_out/total_power_in. I have some experience optimizing perceived smoothness, and we used a metric very similar to this. Without fully knowing what you mean or what he means, I think you're disagreeing over terms, not correctness.
> but in any case, what he says about the "bulk" movement of air (he should probably call it net, i mean all air is bulk by nature) there is no way that the speaker pumping air in and out of the cavity could turn into net movement in one direction... the air coming out was directionally focused from the cone? and sucking back in was amorphous and somehow not detected by his device?
I think you're agreeing with him here, his explanation matches yours. We can break a full period of oscillation into two sections: a high pressure section (the air molecules being pushed away from the speaker), and a low pressure section (air being pulled back). The high pressure section travels _coherently_ through the air cannon, mostly moving air molecules in a single direction (as you say, it is "directionally focused from the cone"). The low pressure segment pulls air back into the air cannon, but it is _not_ coherent (as you say, it is "amorphous"). During the low section, molecules can flow towards the air cannon from the side of the cannon; they do not have to come from directly in front of the air cannon. If you rewatch that section I think you'll see you're not disagreeing with him. To be fair, more drawings would help communicate it more clearly. You're correct that if you draw your observation box big enough, there can be no net movement from something wiggling back and forth, but I think he's drawing his observation box over the fire. If you look at that system (the air above the fire), you will see net movement.
what you are calling agreement between me and him I don't see at all. I'm not going to watch that video again. I could watch another one and tell you what's wrong with that one, that would be more interesting.
I know the field of loudspeakers/acoustics very well, what I've said so far and will say now is all off the top of my head, and it's unlikely that it's in his head at all. We're not going to research a number like 5% more efficient because that's a complete waste of time, let me explain. "We" measure loudness of sound on a decibel scale, that is tenths of a Bel, and the Bel scale is a logarithmic scale, more or less because that's how human hearing perception works, I guess because that's how sounds occur in nature (evolution). But what that all translates to is, to be perceived as "twice as loud" requires a 10 decibel increase; that corresponds to an increase of 10 times the power. On a smaller scale, a 3 dB increase requires doubling power. 3dB is perceptible, but minimally so. So for a tiny 3db increase in loudness requiring 2x the power, is anybody interested in an 5% inefficiency increase taking us to needing 2.1? no, nobody is interested in that, they don't make power amplifiers with ".05 times more power!"
(maybe I should add, the decibel scale is a comparative scale, not an absolute scale, and the hearing/sound phenomenon is not linear to begin with, so it works best and most intuitively on smaller ranges; to put it a different way, a power amplifer can go from zero (off) to 10 Watts, 100 Watts, 1000 Watts, but there is no "log of 0")
now, as to the comparison of tuned ported/bass reflex compared to acoustic suspension (which is what sealed box refers to): acoustic suspension is NOTORIOUSLY ineffient; it is also notoriously good sounding, and in a compact amount of space like an apartment living room the inefficient power is not important to achieving high sound volumes to create a symphony listening experience.
But that is not true of infinite baffles (consider a speaker mounted in a wall), so to lump together infinite baffle with acoustic suspension and call something else 5% more efficient is just plain wrong, but who cares because 5% is nothing on a logarithmic scale.
(space efficiency btw is very important in most people's living spaces, and that's where acoustic suspension really wins. I don't know the "efficiency" of acoustic suspension, but people did need to upgrade their power amplifiers, say from 3 watts to 10 watts or to 20. This was in a period of time where electronics were still transistorizing and shrinking so people would notice "hey, I need to buy something, can't keep using the old thing" more than %ages)
the goal is not efficiency, it's good sound. bass reflex improves its sound by cancelling the resonant frequency which would be overly loud otherwise. acoustic suspension also tames the resonance, but with an entirely different method, the speaker box is small enough that the compression of the air acts as a spring, where the entire surface of the (paper) cone is supported by the sealed air cushion; the acoustic supsension loudspeaker driver itself does not need a spring in that setup, but it is required for other applications of loudspeakers.
he didn't ask himself any questions about the difference between the air cannon and his bass reflex port plus air cannon setup. The frequency of of audio, even very low bass notes would be minimum 20 Hz (that is unrealistically low for most sound systems), and the normal air cannon "balloon snap" is not really comparable. A test he could do would be to keep the speaker cavity filled with smoke and see if a 20 Hz signal blows 20 smoke rings a second: guarantee, it does not, but it might do something interesting. the relatively slow swirl of the smoke ring is a turbulence after effect phenomenon
but lets go back to why I wrote my original comment. incels here were making fun of a mexican high school girl and using that video to point out she had accomplished nothing. so to give her the same credit every high school student deserves for their science fair project, I thought I'd point out that this youtube genius could also be made fun of.
> I know the field of loudspeakers/acoustics very well, what I've said so far and will say now is all off the top of my head, and it's unlikely that it's in his head at all.
The wikipedia article (linked above, linked here for your convenience) [0], disagrees with your claim, and matches what the action lab says. Perhaps you can reconcile the difference, or you can correct the wikipedia article. The article says the bass reflex improves "the efficiency of the system at low frequencies", and "the efficiency can be substantially improved over the performance of a similarly sized sealed-box enclosure". My best guess is that are defining efficiency as something other than total_power_out/total_power_in.
I also just asked the AI [1], and it too states that you are wrong, fsckboy. Quote (translated to english):
--- start quote ---
This system is precisely tuned so that the air mass within the tube resonates — acting like an additional diaphragm — at the resonant frequency. This delay inverts the phase of the sound wave from the rear of the diaphragm, causing it to exit the enclosure in phase with the sound from the front. Instead of cancelling each other out, the sound waves reinforce one another. This significantly increases efficiency in the bass range.
Efficiency:
A bass-reflex enclosure increases efficiency in the low-frequency range compared to a sealed box of the same size. At the resonant frequency, the speaker requires less amplifier power and less cone excursion to produce the same sound pressure level.
Boominess and Neutrality:
The first user claims the port is there to reduce boominess. The opposite is often the case: poorly tuned bass-reflex speakers are prone to "booming" or imprecise ("boomy") bass precisely because of the resonance. A sealed enclosure often sounds more "neutral" and precise by nature, though it does not extend as deep into the low frequencies."
with a bass reflex port, the design tunes it acoustically to work with the chosen speaker (and cabinet size blah blah). Given how acoustics work, that means you could tune it to be out-of-phase at the resonant frequency, or you could tune it to be in-phase at the resonant frequency. It would not surprise me at all if modern boom box speaker design was tilted to the in-phase mode in order to get a BOOM-BOOM room sound for hip hop, EDM etc. It could be a cheap way to achieve boominess that skateboarders or whoever would find appealing.
my information comes from the past where I come from. In the 1960s and 70s, bass reflex port design (which had only just bugun to be understood) was tuned toward out-of-phase tuning to accomplish the taming of the resonant frequeny hump in the frequency response, and the audiophile goal was generally regarded as recreating the classical music concert hall experience in your living room without sound coloration, and which music does not have boom-boom elements, except for the occasional timpani thump. The subwoofer had not even been invented yet.
as to the efficiency claims, see the cousin-to-this-comment i just made. In brief, wikipedia is talking about comparing different designs, and I (and the original youtube video) were talking about the efficiency effect it would have on the self-same system, not compared to other different systems. You can surely see that out-of-phase resonance might be likely to decrease the sound level, and in-phase reinforcement would be likely to increase the sound level. That is what I was talking about.
(it's not actually as simple as what it seems on its face, the acoustic feedback of the sound waves (bass reflex) will be transmitted back through the electronics to the feedback loop in the amplifier itself. Think of it like a conservation of energy type argument, shifting gears on your bicycle does not give you more energy but it can increase the efficiency-kind-of-sort-of of the transfer of energy from you to your bicycle, so comparatively speaking shifting gears on your speaker. I say kind-of-sort-of because what energy gets wasted where (in the form of wasteful heat) isn't completely intuitive. systems have their lowest impedance at their resonant frequency, thus highest energy transfer, but feeding back to change the behavior at the resonant frequency will change the impedance rather than simply "hey free efficiency" or something, because we are changing frequency dependent impedance rather than removing resistance/friction.)
the musical problem with choosing a "resonance reinforcement" technique is that it works at the same resonant frequency all the time (same for that speaker, different for other speakers). What's pleasing about music is the artists choices of musical notes. Different songs have different note choices, but the speaker's resonant frequency is always the same so a song in the key of, e.g., G will always be emphasized in the key of C which does not make musical sense.
the opposite is not the case, if you use bass reflex to demphasize the resonant frequency, you are making all songs sound better.
in the particular case of the youtube video, he would still be wrong because he is measuring/testing right at the bass port, which for bass notes with a long enough wavelength would still be reinforced by the sounds from the front of the speaker, but not in the directed way that he is trying to capture with the smoke ring cannon because the reinforcing waves would be arriving from elsewhere and not coherent with the (hypothetical) smoke rings. also the smoke ring cannon is tuned for a much lower bass note, if you pumped 20Hz through it (an extremely low note, the limit of human hearing), that would imply 20 smoke rings a second. Does anything about the smoke ring cannon seem to indicate that it could put out 20 smoke rings a second? highly doubtful, they would interfere with each other. notice that the bass port is much smaller than the smoke ring cannon, probably a bad impedance match, though I doubt the smoke ring cannon is operating at all on frequency, just simply the turbulent movent of air (and smoke)
addendum, in fact by attaching the smoke cannon cone to the bass port, he is changing the resonance of the entire system, and you can no longer be sure he is reinforcing or cancelling particular frequencies.
my statement was that the bass reflex design decreased the efficiency of that system itself (as in "it could be more efficient in itself, which is what the youtube video was saying). Cancelling some frequencies decreases the efficiency of it's own components, but that it did so by choice in favor of accuracy of sound and beneficial compromises toward space-efficient form factor.
I did NOT say it was more or less efficient than any other design, nor did the youtube video, which is what wikipedia has successfully attempted to delude you into talking about, and unsuccessfully at being correct because it conflates infinite baffle with acoustic suspension which with absolute certainty have vastly different efficiencies and tonal qualities and therefore the wiki simply wrong.
On another dimension you have left out, different loudspeaker acoustic cabinet designs are optimized by coupling with completely different drivers (I'm using the term driver to refer to the metal-frame/paper-cone structure itself, not any wooden enclosure) With acoustic suspension, the air in the cabinet privates a taut springiness, and thus the spring built into the driver is more or less eliminated making the speaker cone on its own "floppy". You can't use that driver in a different design, the components must be designed together to work together, matching impedance, so it is silly to naively compare efficiency, and as I already pointed out, any 5% efficiency difference is dwarfed by other considerations.
I'm happy to educate you, but you don't know what you are talking about, so arguing against your uninformed reading of wikipedia is tedious.
> he called oxygen the fuel for the fire... it's not the fuel for the fire
I think you're correct here, from chemistry definitions oxygen is not fuel, because breaking its bond consumes energy rather than releasing it. However, I don't think the host is trying to give perfectly precise chemistry definitions here, he's trying to explain how fire burns, and calling oxygen 'fuel' makes it clear to his audience that oxygen is required for combustion. I think your objection here is similar to objecting that voters in the US elect electors rather than candidates -- it's correct, but not necessary if you're explaining the concept of democracy.
> the port actually decreases the efficiency of the speaker by letting the negative bass note sine waves cancel out the positive sine waves from the front of the speaker, but this is done to tone down the "boominess" of the speaker at its resonant frequency, thus making the speaker more "neutral" sounding
I don't know much about bass reflex speakers, but I read the wikipedia page in decent depth, and it appears to me that you are wrong, or perhaps using a different definition than the field itself uses. From the wiki page: "This port enables the sound from the rear side of the diaphragm to increase the efficiency of the system at low frequencies as compared to a typical sealed- or closed-box loudspeaker or an infinite baffle mounting... Depending on the exact relationship between driver parameters, the enclosure volume (and filling if any), and the tube cross-section and length, the efficiency can be substantially improved over the performance of a similarly sized sealed-box enclosure." [0]. I bet I can see where your disagreement comes from though -- I think you're arguing that adding the reflex speaker cancels some of the power going through the main speaker, and therefore must result in decreased total_power_out/total_power_in (forgive me if I misunderstand). This is a sensible way to define efficiency, and I think you're correct that total_power_out is strictly decreased. However, there are also other sensible ways to define efficiency, eg, instead of total_power_out you might care about the perceptually-weakest frequency the speaker generates, to ensure the sound is "balanced" to a human ear. You might then define efficiency as num_spectral_bins*min_weighted_spectral_power_out/total_power_in. I have some experience optimizing perceived smoothness, and we used a metric very similar to this. Without fully knowing what you mean or what he means, I think you're disagreeing over terms, not correctness.
> but in any case, what he says about the "bulk" movement of air (he should probably call it net, i mean all air is bulk by nature) there is no way that the speaker pumping air in and out of the cavity could turn into net movement in one direction... the air coming out was directionally focused from the cone? and sucking back in was amorphous and somehow not detected by his device?
I think you're agreeing with him here, his explanation matches yours. We can break a full period of oscillation into two sections: a high pressure section (the air molecules being pushed away from the speaker), and a low pressure section (air being pulled back). The high pressure section travels _coherently_ through the air cannon, mostly moving air molecules in a single direction (as you say, it is "directionally focused from the cone"). The low pressure segment pulls air back into the air cannon, but it is _not_ coherent (as you say, it is "amorphous"). During the low section, molecules can flow towards the air cannon from the side of the cannon; they do not have to come from directly in front of the air cannon. If you rewatch that section I think you'll see you're not disagreeing with him. To be fair, more drawings would help communicate it more clearly. You're correct that if you draw your observation box big enough, there can be no net movement from something wiggling back and forth, but I think he's drawing his observation box over the fire. If you look at that system (the air above the fire), you will see net movement.
[0] https://en.wikipedia.org/wiki/Bass_reflex