Bag End Infrasub, the latest subwoofer scam?

[Uter]

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.

 

[kemmler3D]

I guess to be fair, most subs won't even do 80dB SPL down to 8hz no matter how much DSP you shove at them.

 

[Uter]

I guess to be fair, most subs won't even do 80dB SPL down to 8hz no matter how much DSP you shove at them.

You're assuming this does?

 

[Vladimir Filevski]

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*‍

It is not a subwoofer scam! You got it all wrong.
It is not "only +6 dB shelv"! A single integrator has 6 dB per octave slope, so for equalizing a second-order sealed enclosure, two integrators are needed, producing 12 dB per octave slope. You can equalize it to 1 Hz if you want, but for practical reasons Bag End subwoofers are limited to 8 Hz. This type of subwoofer is patented by Edward Long and Ronald Wickersham and is licensed to Bag End company.
I built this type of subwoofer some 20 years ago, with 18" RCF pro driver - it works as advertised by Bag End company. I limited it to 15 Hz.

 

[KL....]

Noticed this Bag End InfraSub and thought it would be good for discussion and, in the video, the following was mentioned....

Most home-audio enthusiasts have never heard of Bag End InfraSub, even though its approach to deep bass is fundamentally different from the subwoofer designs found in most systems. We visually break down how Bag End InfraSub produces flat response down to 8 Hz, what the dual integrator actually does, and why this technology matters for high-performance music and home-theater systems. Instead of using cabinet resonance to create the impression of deep bass, InfraSub combines a sealed loudspeaker system with dual-integrator compensation. The system corrects the natural low-frequency roll-off below resonance while reducing the influence of the resonance itself. The result is not simply more bass. The goal is uniform low-frequency extension, accurate timing, controlled response, and bass that integrates naturally with the rest of the system.
In this explanation, you’ll see:

• How a conventional sealed subwoofer behaves around resonance
• Why response naturally falls below the resonance frequency
• How the Infra dual integrator compensates for that roll-off
• How the operating range extends from 8 Hz to the loudspeakers resonance point
• Why overload protection is built into the dual-integrator processor
• How different InfraSub cabinet and driver configurations use the same underlying principle
• An example signal chain using the Acurus ACT 4, Bag End Infra-MXB, Acurus M8X, and passive Bag End InfraSub loudspeakers
• Why deep, accurate bass can matter for both music and home cinema

This is a different way of thinking about subwoofers. It is not about exaggerated impact or one-note bass. It is about reproducing the lowest frequencies in their proper relationship to the rest of the soundtrack or recording. If you care about accurate bass reproduction, high-end home theater, two-channel audio, or the engineering behind truly extended low-frequency systems, Bag End InfraSub is a technology worth knowing about.

 

[Chrispy]

I've heard of them, haven't dug into them but various specs/measurements that I've seen take them into the higher performance area. Different designs and different drivers will more answer your questions.

 

[DWPress]

I too have heard of them but I'm not sure I need 8Hz extension. Even with Dirac ART I put a HP filter at 23Hz because bass lower than that (in my room) is annoying, not a lot of content with those frequencies except IBD and maybe pipe organs anyway.

 

[Chrispy]

I too have heard of them but I'm not sure I need 8Hz extension. Even with Dirac ART I put a HP filter at 23Hz because bass lower than that (in my room) is annoying, not a lot of content with those frequencies except IBD and maybe pipe organs anyway.

Why do you "need" 8hz extension and at what relative point to the general frequency response especially after eq to get there?

 

[Martin]

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

 

[Keith_W]

I too have heard of them but I'm not sure I need 8Hz extension. Even with Dirac ART I put a HP filter at 23Hz because bass lower than that (in my room) is annoying, not a lot of content with those frequencies except IBD and maybe pipe organs anyway.

My system can go down to 15Hz, but I high-pass it at 20Hz. Why? Because my house can't take it. If I let it go that low, something starts to rattle. I have long ago given up trying to find out what's causing the rattle and doing something about it, so I high-pass my system. I would rather do without infrasonics than to put up with that rattle. But it did make me look to see whether music had infrasonic content or not - and it most definitely does.

Aphex Twin, "Come to Daddy", Track 1. Note infrasonic content below 10Hz.

Bach Violin Sonata No. 1 BWV 1001, Allegro (Julia Fischer). Note infrasonic content below 20Hz. Why is there infrasonic content in an acoustic recording of a violin? That's where the ambience lives. If I turn off my subwoofers, the "concert hall" acoustic seems to disappear and she no longer seems to be playing in a large acoustic space.

Not to mention, all those home theatre enthusiasts who love explosions and stomping T Rexes will tell you that infrasonics adds a lot to the immersion.

IMO the real question is whether you are better off trying to get infrasonics via an infrasonic subwoofer, or whether you should install a tactile transducer. Since it is more felt than heard.

 

[kemmler3D]

I'd heard of them a long time ago, maybe just saw them in the stereo shop when I was a kid.

I think infrasound makes sense if you have recordings that aren't highpassed and also include full-spectrum transients. In that scenario you can get all the impact the recording has to give.

I don't think infrasound tones in music are a thing (they say pipe organs only go down to 16hz?) and if they are, I am not sure I want them.

My LCD-XCs will do clean infrasound... one time I put a 15hz tone on and turned it up to see if I could hear anything. I momentarily freaked out because some part of my brain thought there was an earthquake, no joke. I didn't really hear anything but I had a momentary panicked sensation because I basically tricked myself into thinking the room was shaking.

Also, supposedly haunted houses (including ghost sightings) are sometimes caused by loud infrasound from resonances in the house, or something. I guess infrasound can give you a general sense of unease and even cause hallucinations by resonating your eyeball?

Not sure about the latter... but in general I think infrasound sounds good on paper but is literally viscerally frightening on an instinctual level, and would actually not be fun to listen to on a sustained basis.

 

[Titurel]

I owned one for around a dozen years. It performed well and was in deed capable of 8 Hz (or so), provided I didn't crank up the volume. If I did crank it up and the signal fed to it had significant low end content, the infrasub guarded itself (and my lease) by dynamically rolling off the bottom end. It's best use (for me) was as an adjunct to systems that already had fairly strong response into the mid 30s.

I suspect the infrasub was designed with needs of mastering labs in mind, to help insure that unintended subsonic signals* DON'T end up on the final disc.

* Air conditioning transients, subway rumbles, etc.

 

[Keith_W]

I don't think infrasound tones in music are a thing (they say pipe organs only go down to 16hz?) and if they are, I am not sure I want them.

Since you ask, this is Bach's Trio Sonata BWV 525 for pipe organ, performed by Daniel Chorzempa. The spectro shows 0Hz - 200Hz. Plenty of content down there below 20Hz. If you listen to the recording with subwoofers on, you get a real sense of scale and authority. Turn the subs off, and it's like decaf coffee. Or a white shark with no teeth. Or Argentina without Messi.

 

[DWPress]

My system can go down to 15Hz, but I high-pass it at 20Hz. Why? Because my house can't take it. If I let it go that low, something starts to rattle. I have long ago given up trying to find out what's causing the rattle and doing something about it, so I high-pass my system. I would rather do without infrasonics than to put up with that rattle.

Never mind whatever content there might be in infrasonic land, I'm perfectly content with missing out on it for the exact same reason. There's a lot of things in my room that can resonate or rattle at any given time and I'd rather not have my tummy and throat keeping beat.

I'm just a stereo guy though, home theater people who go gonzo will probably want as many octaves as they can pull off...

 

[NotInYourHead]

View attachment 549545

Since you ask, this is Bach's Trio Sonata BWV 525 for pipe organ, performed by Daniel Chorzempa. The spectro shows 0Hz - 200Hz. Plenty of content down there below 20Hz. If you listen to the recording with subwoofers on, you get a real sense of scale and authority. Turn the subs off, and it's like decaf coffee. Or a white shark with no teeth. Or Argentina without Messi.

A little off-topic, Keith, but what about the other end of the spectrum, specifically beyond 16-20KHz? Do they have a significant contribution to the listening experience?

I was spurred because I recently saw Audio Smile (manufactured the LBM, reviewed by ASR) offering a planar super-tweeter which claims extension to 40KHz.

 

[101geo]

It's something anyone with decent dsp can replicate using a Linkwitz Transform filter with something like a Fabfilter Pro or TDR Nova vst to turn down the LT effect as volume rises. It wasn't a scam before DSP became freely available but the OP is right, any vst host can do this today for free in many cases.

 

[Keith_W]

A little off-topic, Keith, but what about the other end of the spectrum, specifically beyond 16-20KHz? Do they have a significant contribution to the listening experience?

I personally think the bottom octave is more important than the top, because (1) EVERYONE can hear bass, but not everyone can hear the top octave, and (2) there is simply more music down there. This doesn't mean I am willing to sacrifice the top end though! It is easy to choose a tweeter that goes up to 20kHz, and any speaker that does not do at least that IMO isn't worth considering.

But ultimately it depends on you - do you have hearing loss? Do you regularly listen to music with extension up to 20kHz? You can test this yourself by getting REW to play a test tone at standard listening level. Start at 1kHz and adjust the volume until it feels subjectively loud. For a sanity check, put a mic next to you and use REW's RTA. This is to confirm that your speaker is actually producing sound. Then 5kHz, 10kHz, 15kHz. When you get to 15kHz, increase the tone by 1kHz increments. At some point you will stop hearing it. I can barely hear a 16kHz test tone, which is good for my age (54). Needless to say, you will need a speaker that is flat to 20kHz to conduct this test.

 

[norman bates]

Meh.

Basically a strong magnet 18" woofer in a way too small sealed box, that rolls off 12db an octave below 80hz naturally.
Now apply a high pass filter that rolls of 12db an octave starting near 20hz.
Bam, flat output 20-80hz.
I think it rolls at 8hz but the knee the freq rolls off at increases as the volume is also increased.
Think f3 30hz if you are at 100db (I'm estimating).
However, you are boosting the low end by 24db.

See post #9 I did years ago when I was more into subs.

The magic crossover - How to reach below 17Hz at -3dB with ultra-low phase distortion

2 x 18NLW9400, 152 liters each closed box (or both in one box of 304 liters) - processing see MathCAD screenshot, next post. 2 x 15MI100, 91 liters each closed box, processing see MathCAD. NO ANY resonator, filter corner frequency, steep phase decay, helmholtz, etc. between 20Hz and 400Hz ->...

www.diyaudio.com

I would only make push pull subs (like perlisten), not isobarik.

Here is a huge thread on ppsl design (push pull slot loaded).

A Thread for those interested in PPSL enclosures

This is a new thread as suggested by Moray James. For Moray James: What I did was to simulate the enclosure with two speakers in Horn Response. I simulated it as you would an Altec A7 type of speaker but with a front chamber on the horn. This front chamber would be the plenum if I am doing it...

www.diyaudio.com

 

[jhaider]

Indeed, hardly new.

Way Down Deep II

In Part II of the perhaps most ambitious report on subwoofers ever to appear in print, Keith Yates gives you the lowdown on four more contenders, from one that uses a water-filled membrane in its design to a model popular for producing gut-wrenching rumbles on theme-park rides. Details on the...

www.soundandvision.com

IIRC their drive units only have about half the throw of the current SOTA “pro” devices.

 

[Beave]

A very differently-titled thread about the same video was posted here a couple of days ago:

https://www.audiosciencereview.com/forum/index.php?threads/the-latest-subwoofer-scam.72663/

@RickS , should the two threads be merged into one?