Bag End Infrasub, the latest subwoofer scam?

[Flaesh]

my paper "Simple Bass Equalizer for Closed-Box Loudspeaker Subwoofers":
https://ieeexplore.ieee.org/document/4588104

Not available without a subscription.

 

[Vladimir Filevski]

Yes, true, but I posted it only as a reference. It is a simple Sallen-Key OpAmp second order Q=0.707 low-pass filter, for a Qtc=0.707 sealed loudspeaker.

 

[KL....]

Ascendo Infrasub/s, for discussion and comparison (w/ Bag End & others)....

Have you ever experienced bass so deep you feel it in your bones before you even hear it? An exclusive interview with Geoffrey Heinzel of Ascendo Immersive Audio. Ascendo is widely known as the undisputed king of infrasonic bass, building some of the most massive, physics-defying subwoofers on the planet. But they are much more than just brute force! In this video, Geoffrey breaks down the science behind their earth-shattering infrasonic subwoofers, their incredibly efficient horn speakers, and the insanely high signal-to-noise ratio electronics that make their systems sound so effortless and dynamic.

 

[puntloos]

This uses 14 minutes of AI CGI to describe a below resonance operated sealed subwoofer with a correction EQ and excursion limiter. You have to buy their "Integrator" to do worse (only +6 dB shelv) what any 10$ DSP would do *facepalm*‍

Could have just posted free field frequency response & CEA-2010 graphs of the thing and we would have known everything we needed to know. I doubt we will ever see either.

Yea I don't quite see what's special here, almost any piddling sub will move their cone a little at 8hz, it's just that to actually hear/feel it you need it to be huge.

Here they claim good dsp down to 8, just don't look at the spl

 

[Vladimir Filevski]

No, they claim flat frequency response down to 8 Hz - which is very rare. In the same time they warns: when demand is on higher SPL, that corner frequency F3 is moving from 8 Hz to higher frequency (more SPL - higher F3).

 

[ElJaimito]

I asked if anyone following or involved in this thread had any hands-on (first person) experience with the product.

Not the Bag End product, no. But the product type, yes, built a pair using the identical principle back in '93 or so (AFAIR). They still work. They are particularly effective in small rooms that approximate to a sealed condition, whereas bass reflexes suck (or rather, suck and blow) in that condition. I'm building a new set with bigger than 10" drivers for my new studio (3x15). This to keep up with louder mains but will need about 1 kW of peak drive at 30 Hz.

 

[Curvature]

You may be guilty here of comparing sensory apples to bagels. 8Hz can be felt at much lower signal levels than it can be heard. There is no need for infra tones to be perceived (exclusively) aurally for them to be telling in a performance. As has been mentioned, low sonics and sub-sonic can induce feelings of discomfort, dread, or awe, while not being perceived (heard) as sound. Why do you think church organs frequently have 32' registers, a few even have 64s? Resultants can produce even lower pitches. E.g., 32'C and G played simultaneously - Awesome! - we hear C and G and feel the sub-octave resultant pitch as it rattles our thoraxes.

Say what?

120dB SPL is required to meet the vibrotactile threshold if we are talking about sound for 8Hz.

https://www.researchgate.net/publication/8436733_Hearing_at_low_and_infrasonic_frequencies

While the audible threshold is some 10-20dB lower:

 

[Titurel]

Say what?

120dB SPL is required to meet the vibrotactile threshold if we are talking about sound for 8Hz.

View attachment 559680

https://www.researchgate.net/publication/8436733_Hearing_at_low_and_infrasonic_frequencies

While the audible threshold is some 10-20dB lower:

View attachment 559681

Conspicuously missing from the the charts are things like transmission medium (e.g., via air versus direct contact). How does one even assign an SPL value to signals transmitted directly to a test subject via an oscillating surface, like a floor. I can manually detect my pulse rate, presently 50 beat per minute or .833 Hz. How loud must it be for my fingers to hear it?

 

[norman bates]

Link to 21” bag end subwoofer test/review with graphs. Distortion skyrockets as frequency goes lo and loud, expected from a sealed subwoofer to me. A ported acts like a brake lessening the excursion at tuning, but then unloads below.

Way Down Deep II Bag End S21E

Bag End S21E

www.soundandvision.com

 

[Curvature]

Conspicuously missing from the the charts are things like transmission medium (e.g., via air versus direct contact). How does one even assign an SPL value to signals transmitted directly to a test subject via an oscillating surface, like a floor. I can manually detect my pulse rate, presently 50 beat per minute or .833 Hz. How loud must it be for my fingers to hear it?

SPL can be mathematically converted from vibration (measured in terms of acceleration) and vice versa.

You can measure the SPL of the pulse at your wrist either acoustically (in an incredibly quiet anechoic chamber) or using an accelerometer. It would be a very low number in any case. But the pressure receptors in your fingers require direct contact for meaningful energy transmission to happen. The intensity of the pulse is simply too low to transfer by air to your ear due to the drop in impedance.

 

[Titurel]

SPL can be mathematically converted from vibration (measured in terms of acceleration) and vice versa.

View attachment 559688

You can measure the SPL of the pulse at your wrist either acoustically (in an incredibly quiet anechoic chamber) or using an accelerometer. It would be a very low number in any case. But the pressure receptors in your fingers require direct contact for meaningful energy transmission to happen. The intensity of the pulse is simply too low to transfer by air to your ear due to the drop in impedance.

Of course, the issue I raised was one of perception, not audibility. Also, whatever conversion you perform should include the potential impedance mismatch between the emitter and sensor. Just for ducks, you might want to compute the emitted volume of my .833 Hz pulse measured at the standard 1M from my wrist.

Not everything readily perceived is readily converted to a meaningful (i.e., useful) metric. The argument to that is "Well I can do it." To which I answer, "Okay. Now what?"

 

[Curvature]

Of course, the issue I raised was one of perception, not audibility. Also, whatever conversion you perform should include the potential impedance mismatch between the emitter and sensor. Just for ducks, you might want to compute the emitted volume of my .833 Hz pulse measured at the standard 1M from my wrist.

Not everything readily perceived is readily converted to a meaningful (i.e., useful) metric. The argument to that is "Well I can do it." To which I answer, "Okay. Now what?"

I quoted your earlier post where you claimed that you can feel low frequency sound before you can hear it. Well, in what sense? The research shows that sound would always be heard first, before it triggers sensation. Sound, specifically, through air.

The body is bone and wet tissue held together, so it acts like a damped system, absorbing or reflecting low SPL. High SPL overcomes the damping and eventually leads to perceptible vibration, as seen in the thresholds chart.

Like you said, the transmission medium matters. If there is a source of vibration, it will trigger mechanoreceptors in the body, through a series of solids. But that's not sound.

 

[Titurel]

I quoted your earlier post where you claimed that you can feel low frequency sound before you can hear it. Well, in what sense? The research shows that sound would always be heard first, before it triggers sensation. Sound, specifically, through air.

The speed of sound is computed in various media. Clearly it is not limited to transmission via air (at some temperature and pressure).

The body is bone and wet tissue held together, so it acts like a damped system, absorbing or reflecting low SPL. High SPL overcomes the damping and eventually leads to perceptible vibration, as seen in the thresholds chart.

Who do you suppose designed this damped system or that it is the only system by which we can perceive vibration? The sensors (nerves) are at various depths in the human body and connect to the central nervous system through a number of schemes. You seem stuck on perception of vibration (sound) as being limited to the tympanic or pneumatic. Nope.

Like you said, the transmission medium matters. If there is a source of vibration, it will trigger mechanoreceptors in the body, through a series of solids. But that's not sound.

That's mighty zen. And it leads us (inevitably) to...

If Helen Keller were to fall over in a forest, would it make a sound?

 

[Curvature]

Who do you suppose designed this damped system or that it is the only system by which we can perceive vibration? The sensors (nerves) are at various depths in the human body and connect to the central nervous system through a number of schemes. You seem stuck on perception of vibration (sound) as being limited to the tympanic or pneumatic. Nope.

For any subjective sensation to be registered, it has to breach thresholds. For vibration to be perceived as sound, it has to breach thresholds. For sound to be perceived as vibration, it has to breach thresholds. All of these things are measurable.

You may be guilty here of comparing sensory apples to bagels. 8Hz can be felt at much lower signal levels than it can be heard. There is no need for infra tones to be perceived (exclusively) aurally for them to be telling in a performance. As has been mentioned, low sonics and sub-sonic can induce feelings of discomfort, dread, or awe, while not being perceived (heard) as sound. Why do you think church organs frequently have 32' registers, a few even have 64s? Resultants can produce even lower pitches. E.g., 32'C and G played simultaneously - Awesome! - we hear C and G and feel the sub-octave resultant pitch as it rattles our thoraxes.

"For 8Hz can be felt at much lower signal levels than it can be heard." If the signal is acoustic, the answer is no. If it is a mixed vibratory and acoustic signal, still no, because it takes a huge amount of energy to trigger vibrotactile perceptions at all, and we know this because we can convert vibrational energy into SPL.

 

[KSTR]

I've already mentioned it in this thread: I found that the dominant perception mechanism for ULF (<25Hz or so) is background noise modulation, with the rest of the music also being the background noise. Static pressure change modulates the sensitivity of the ear as the ear drums stretches and stiffens until the ear-to-nose canal allows to establish a pressure equilibrium on both sides of the ear drum, after some time. Think of fast elevator in skyscraper effect.

 

[Jac.H]

Could have just posted free field frequency response & CEA-2010 graphs of the thing and we would have known everything we needed to know. I doubt we will ever see either.

Agreed.

 

[Curvature]

I've already mentioned it in this thread: I found that the dominant perception mechanism for ULF (<25Hz or so) is background noise modulation, with the rest of the music also being the background noise. Static pressure change modulates the sensitivity of the ear as the ear drums stretches and stiffens until the ear-to-nose canal allows to establish a pressure equilibrium on both sides of the ear drum, after some time. Think of fast elevator in skyscraper effect.

I think that holds below 15Hz or so, particularly below 10Hz, when the ear starts begins locking onto individual peaks and tonal perception collapses.

Main way to test this is to crack a window in a moving car. Sounds exactly like LF modulation.