Bag End Infrasub, the latest subwoofer scam?

[Waveform Fidelity]

The lowest note on a church organ is 8Hz, and at sufficient volume, you can actually feel it. Because it's the lowest note the instrument produces, it's often considered the benchmark for subwoofer capability.

A church is also a very big space!

 

[Chrispy]

Answering your first question: it is not (just) a few organs nor special pipes.

Pairs of pipes, played together create "resultant" pitches. A resultant can be the product of a stop, that couples the pipes (electrically or mechanically), or by a player actually playing them simultaneously. Even modest sized organs with 16' pipes can readily produce 32' pitches; likewise, moderately large to very large organs with 32' stops can produce 64' pitches (down to 8Hz). Last time I checked, there were only 2 actual, full-length 64' stops equipped organs, which I suppose would qualify them as special, but as to 8Hz response they are not.*

I have no interest in finding a sub 16Hz recording, but I have little doubt they exist, unless CD mastering hardware or software precludes such. That may the correct or more relevant question.

* If you wanted 4Hz, these 2 organs are the best equipped to give it you.

My understanding is few organs even do 16hz, let alone 8hz. Whether they actually record to that level I was just curious what you'd run into. Takes a lot of sub(s) to do 8hz at an appreciable spl, tho.

 

[Titurel]

My understanding is few organs even do 16hz, let alone 8hz. Whether they actually record to that level I was just curious what you'd run into. Takes a lot of sub(s) to do 8hz at an appreciable spl, tho.

16Hz is bottom C in a 32' rank, which is fairly standard gear in serious pipe organs. Play that bottom C in conjunction with the G above and the "result" is a 64' C (8Hz). And yes, that would require a fair, serious amount of woofing. Don't get trapped in the SPL question. You'll feel 8Hz (even 16Hz) long before you'll unambiguously hear it, i.e., be able to detect its pitch.

 

[Chrispy]

16Hz is bottom C in a 32' rank, which is fairly standard gear in serious pipe organs. Play that bottom C in conjunction with the G above and the "result" is a 64' C (8Hz). And yes, that would require a fair, serious amount of woofing. Don't get trapped in the SPL question. You'll feel 8Hz (even 16Hz) long before you'll unambiguously hear it, i.e., be able to detect its pitch.

I've chased ULF, thanks. You need sufficient spl to make 8hz worth it is more the point.

 

[Blockader]

How loud does 8Hz need to be before you can actually hear it and can real subs get you there?

Watanabe & Møller 1990. This is the measured threshold of hearing curve down to 4Hz (Watanabe & Møller 1990), showing SPL needed just to detect a tone at each frequency.

for 8Hz:

~100 dB SPL = threshold, barely detectable, this is the graph's curve.
~103-105 dB SPL = clearly audible tone. Loudness compression at low frequencies means it doesn't take much: Yeowart et al. (1967) found that near 4 Hz, about 1 dB was enough to go from inaudible to clearly detectable.
~120-125 dB SPL = 'vibrotactile sensation' begins (felt, not just heard), per Møller & Pedersen, that's roughly 20-25 dB above threshold.

I sit and did the math with Claude, here's the table of how many subwoofers needed in a sealed room to reach audible levels of 8Hz.

Config	Sd total	Excursion (peak)	Room volume	SPL
2×18", Sd≈0.12 m² each	0.24 m²	15 mm	50 m³	~111 dB
3×18"	0.36 m²	15 mm	50 m³	~115 dB
3×18", long-throw	0.36 m²	25 mm	50 m³	~119 dB
3×18", long-throw	0.36 m²	25 mm	30 m³	~124 dB

The critical detail is that the room has to be sealed. Once it is, pressure chamber conditions take over: SPL is determined by cone displacementrather than the acceleration of the moving air. So, only 3 capable 18'' drivers are 'enough' to make 8Hz audible.

 

[Titurel]

How loud does 8Hz need to be before you can actually hear it and can real subs get you there?

View attachment 550128
Watanabe & Møller 1990. This is the measured threshold of hearing curve down to 4Hz (Watanabe & Møller 1990), showing SPL needed just to detect a tone at each frequency.

for 8Hz:

~100 dB SPL = threshold, barely detectable, this is the graph's curve.
~103-105 dB SPL = clearly audible tone. Loudness compression at low frequencies means it doesn't take much: Yeowart et al. (1967) found that near 4 Hz, about 1 dB was enough to go from inaudible to clearly detectable.
~120-125 dB SPL = 'vibrotactile sensation' begins (felt, not just heard), per Møller & Pedersen, that's roughly 20-25 dB above threshold.

I sit and did the math with Claude, here's the table of how many subwoofers needed in a sealed room to reach audible levels of 8Hz.

Config	Sd total	Excursion (peak)	Room volume	SPL
2×18", Sd≈0.12 m² each	0.24 m²	15 mm	50 m³	~111 dB
3×18"	0.36 m²	15 mm	50 m³	~115 dB
3×18", long-throw	0.36 m²	25 mm	50 m³	~119 dB
3×18", long-throw	0.36 m²	25 mm	30 m³	~124 dB

The critical detail is that the room has to be sealed. Once it is, pressure chamber conditions take over: SPL is determined by cone displacementrather than the acceleration of the moving air. So, only 3 capable 18'' drivers are 'enough' to make 8Hz audible.

What such charts like those miss (not purposefully) is that low and sub sonics are infrequently encountered absent other tones, except in test environments. That is, the charts do not account for the effect of low sonics on each other and on other, higher sonics.

I return to resultant pitches. They are not just difference tones (signal A minus signal B) but also sum tones (signal A plus signal B). Play two pitches simultaneously, they will produce other pitches both higher and lower in pitch. For example, 16Hz (C) played simultaneously with 24Hz (G) produces 8Hz C AND 40Hz, somewhere between D# and E. (That out of tune sum-tone is part of the aural funk you hear in resultant stops. - intermodulation or, you prefer, timbre).

Pitches beat against each other in space and it is possible to detect low frequencies by their modulation of higher-pitched readily hearable frequencies long before they are detected in isolation. We hear not just directly but also by implication. Leave out the sub and infra sonics and you may leave out intended IM (timbre) as well as the cues about the recording venue's dimensions.

(BTW, what are wow and flutter if they are not infrasonic modulation of the intended frequencies.)

Tuning a piano (without tuning aids other than one or two tuning forks) employs beat frequencies (0Hz & 1-1.5Hz) the former to set unisons, the latter to set temperament. This is all accomplished well below the thresholds suggested by the charts. Otherwise, piano tuning would have to be classified an hazardous profession.

 

[levimax]

This is all accomplished well below the thresholds suggested by the charts. Otherwise, piano tuning would have to be classified an hazardous profession.

Can you link or point to a reference on SPL levels for the audibility of these beat frequencies? No one is saying that in theory reproducing 8 Hz is not interesting or fun or maybe even helpful with realistic music reproduction in some very limited cases. It is also well known that our brains can "fill in" the LF fundamental frequencies from the harmonics in some cases. The objection I have is with the original video which uses a lot of scientific facts and jargon to make it seem like "flat" response to 8 Hz is possible with a "magic" small enclosure and driver. While true at some extremely low output level, this level is going to be 50 dB or more below anything you can hear or even feel. This makes it very misleading.

 

[Titurel]

Can you link or point to a reference on SPL levels for the audibility of these beat frequencies?

I really don't need to, as beat frequencies are in common use both for tuning and to produce expanded timbre and pitch compass. Ask anyone who tunes piano or organs.

Resultant tones, sum and difference tones, beat frequencies, et al. can be either (or both) physical or psycho-acousic. The wiki article on combinations tones should get you pointed in the right direction.

I think part of the problem is confusing the ability to hear with the ability to perceive. Imagine two strings (on a piano or acoustical guitar or whatever) that are supposed to be tuned to the same frequency. But one string is flat by a fraction of cent. The resulting sounds will beat against each other, and, depending on the tuning error, could be perceived as a slow wavering of pitch, the perceived rate can be below 10 Hz. Now did we just hear 10Hz or simply perceive it as the product of 2 very similar pitches? We perceived it, of course, but that doesn't make it any less real. (The audibility threshold is near that of the individual strings.) We heard two pitch we might not hear as differing if sounded sequentially, but when heard simultaneously, produce a clearly audible slow beat, that shows us they are not in tune. Why do you think "honky tonk" pianos sound like they do? It's because the out-of-tunedness of the unisons beats the living daylights out of our built in acoustical software.

Next week: Vibrato - Ornament or Pathology?

 

[KL....]

You Are Missing A HUGE Part Of Your Bass Experience Without BAG END Infrabass

What happens when an engineer who designs audio electronics finally gets to experience fourteen 18 inch subwoofers working together in one theater? This video, Rick Santiago , Co-Founder of Indy Audio Labs explains what made that experience so powerful, and why true infrasonic bass changes the entire feeling of a sound system.

This is not just about making bass louder. Rick breaks down why deep bass below the range of a typical subwoofer can make music, movies, and live recordings feel more real, more physical, and more emotionally convincing. When a system can reproduce the lowest energy in a recording cleanly, the room stops feeling like a speaker system and starts feeling like the actual space where the sound happened.

Rick also explains how Bag End’s electronics help make that possible. From control and timing, to low frequency extension, to keeping the system clean and natural instead of boomy or exaggerated, the electronics play a huge role in making bass feel believable. After hearing fourteen 18 inch subs in one theater for the first time, Rick shares what stood out, what surprised him, and why infrasonic performance can be the missing piece in a truly immersive audio system.

In this video:

• Why infrasonic bass feels different from normal bass
• What fourteen 18 inch subwoofers can do when properly controlled
• Why deep bass is about realism, not just impact
• How Bag End electronics help create clean and natural low frequency sound
• Why the best bass can be felt without sounding bloated or overwhelming
• How proper subwoofer design changes the entire listening experience

Featuring Rick Santiago of Indy Audio Labs and Bag End. If you care about home theater, live sound, recording accuracy, or simply want to understand why great bass feels so different from ordinary bass, this conversation will help explain it in a way you can actually hear and feel.

 

[KL....]

what are the bag end infrasub specs
Bag End Infrasub systems (utilizing Extended Low Frequency / ELF technology) feature an ultra-flat rated frequency response of 8Hz to 95Hz (±3 dB). Two of the most popular models are the Infrasub-18 (18-inch driver) and the Infrasub-12 (12-inch driver), both powered by built-in 400-watt amplifiers.

Infrasub-18 Specifications

• System Type: Forward-firing, sealed-box powered subwoofer
• Low Frequency Transducer: 1 x 18" INFRA cone driver (Kevlar-impregnated paper cone)
• Frequency Response: 8 Hz to 95 Hz (±3 dB)
• Amplifier Power: 400 W RMS
• Inputs: Left/Center/Right line-level (RCA), 1x pair speaker-level inputs
• Outputs: High-pass line-level outputs (12 dB/octave at 95 Hz)
• Dimensions: 23.5" H x 21.25" W x 18.25" D (59.7 cm x 54 cm x 46.4 cm)
• Weight: ~92 lbs (41.7 kg)

Infrasub-12 Specifications

• System Type: Sealed-box active subwoofer
• Low Frequency Transducer: 1 x 12" EL-12P cone driver
• Frequency Response: 8 Hz to 95 Hz (±3 dB)
• Amplifier Power: 400 W continuous sine wave
• Inputs: L/C/R line level (RCA) or balanced XLR (Pro model), L/R speaker level
• Outputs: L/C/R high-pass line level (12 dB/octave, -6 dB @ 95 Hz)
• Dimensions: 15.5" H x 18" W x 16" D (39.4 cm x 45.8 cm x 40.7 cm)
• Weight: 56 lbs (25.4 kg)

 

[prerich]

I'm surprised they are still around. I was looking at Bag End infra-subwoofers in 2000 when I put together my first real home theater audio system. I think they've always been more of a professional manufacturer with a few home products. They make an interesting product.

Martin

I've always wanted a bag end sub. I've actually owned 3 M-6 concentric driver studio monitors finished in automotive "Mercedes Benz" black. One of the few speakers I regret selling. They make very good products and their subs were the truth back in the day (early 2000's). They're a professional market speaker company.

 

[Mnyb]

I have to wonder about music production at frequencies below or above human hearing how do you monitor that and set correct levels for the production ??

Ultrasound basically impossible . For infra sound, the studio control room must have immense subs ,well done acoustics and EQ to work properly ?

 

[levimax]

Infrasub-12 Specifications

• Frequency Response: 8 Hz to 95 Hz (±3 dB)

This is a bogus and misleading spec. If the company was on the up and up as some claim they would not publish something like this. It "may" be true at some ridiculously low SPL level but not at any useful level.

 

[smygolf]

This is a bogus and misleading spec. If the company was on the up and up as some claim they would not publish something like this. It "may" be true at some ridiculously low SPL level but not at any useful level.

well they also spec "true" values
As seen below it is nothing special about them

SVS Sub 12 NSD has similar spec and that is in free air at 2 met

 

[Titurel]

This is a bogus and misleading spec. If the company was on the up and up as some claim they would not publish something like this. It "may" be true at some ridiculously low SPL level but not at any useful level.

This is a bogus and misleading criticism. (see SMYGOLF's post above) Bagend is a well respected company aimed at the professional market. Both the marketing materials and user documentation supplied with their gear makes lucidly clear the SPL limitation of the infrasubs. The spec. you objected to, assumes that you've read and understood the documentation. The sub will be flat (+ or - 3db) as long as you stay below the SPL limit dynamically set by the amp/controller. In plain language, the bottom end is purposefully rolled off when the SPL limit (for a given frequency) is exceeded. In other words, the amp/controller limits the user's ability to do something stupid - over drive the transducer at low frequencies.

The main reason I gave away my infrasub was that it violated an important WAF guideline: A speaker is allowed to be inconveniently big or pug ugly, not both.

 

[levimax]

This is a bogus and misleading criticism. (see SMYGOLF's post above) Bagend is a well respected company aimed at the professional market. Both the marketing materials and user documentation supplied with their gear makes lucidly clear the SPL limitation of the infrasubs. The spec. you objected to, assumes that you've read and understood the documentation. The sub will be flat (+ or - 3db) as long as you stay below the SPL limit dynamically set by the amp/controller. In plain language, the bottom end is purposefully rolled off when the SPL limit (for a given frequency) is exceeded. In other words, the amp/controller limits the user's ability to do something stupid - over drive the transducer at low frequencies.

The main reason I gave away my infrasub was that it violated an important WAF guideline: A speaker is allowed to be inconveniently big or pug ugly, not both.

For the 12" sub the SPL level to be "flat to 8 Hz" is absurdly low. Assuming their specs are correct and taking 3 dB off their 81 dB 10 Hz spec for 8 Hz would give 78 dB and this would be with massive distortion. At 8 Hz 78 dB is ~25 dB below the threshold of hearing, at 20 Hz it is barely the threshold of hearing and 78 dB at 95 Hz can easily be produced by a 6" woofer. Why do they have to resort to misleading specs and a video which twists the science to support their "flat to 8 Hz" claim for a 12" subwoofer? I am sure they sound more or less like any other relatively large 12" sealed sub but why not chose to support a company that isn't purposefully trying to mislead people in order to stand out? This site promotes science in audio so people can be better informed, not science twisted to intentionally mislead them.

 

[KSTR]

I found that ULF is usually not heard as a tone proper (unless it is very loud) but rather as background noise modulation. The ULF sort of impresses a level envelope on everything else.

 

[Titurel]

For the 12" sub the SPL level to be "flat to 8 Hz" is absurdly low. Assuming their specs are correct and taking 3 dB off their 81 dB 10 Hz spec for 8 Hz would give 78 dB and this would be with massive distortion.

You know this how? Would you kindly show us your personal measurements or those of a qualified, disinterested 3rd party. You might also include references laying out the aural significance of distortion in moderate level (i.e., lower than 80db) dynamically band limited sub-sonic transducers. Remember, compare apple to apples.

My opinion, I admit, is based mostly on 20 years using an 18" infra-sub. Distortion from it, at my preferred SPLs, was in my experience negligible.

 

[levimax]

You know this how? Would you kindly show us your personal measurements or those of a qualified, disinterested 3rd party. You might also include references laying out the aural significance of distortion in moderate level (i.e., lower than 80db) dynamically band limited sub-sonic transducers. Remember, compare apple to apples.

My opinion, I admit, is based mostly on 20 years using an 18" infra-sub. Distortion from it, at my preferred SPLs, was in my experience negligible.

I used their own published spec of 81 dB at 10 Hz to estimate 78 dB at 8 Hz, it will be close in any case. I am talking specifically about the 12" sub claims. Threasholds of hearing are well documented as is the capability of 6" woofers. I am sure subs work fine, I just don't like their 8 Hz marketing claims.

 

[Titurel]

I used their own published spec of 81 dB at 10 Hz to estimate 78 dB at 8 Hz, it will be close in any case. I am talking specifically about the 12" sub claims. Threasholds of hearing are well documented as is the capability of 6" woofers. I am sure subs work fine, I just don't like their 8 Hz marketing claims.

If you truly understood their documentation and the design goals, you might feel differently.