Bag End Infrasub, the latest subwoofer scam?

[levimax]

Comparing max SPL at 15 Hz for all sealed subwoofers with single driver in this table, it follows that Bag End S21E is somewhere in the middle. Not bad for a subwoofer described as "doesn't seem to be anything special".

What is special about middle of the road output at 15 Hz for a 21" driver sub? Nothing wrong with it but certainly nothing special. Again these subs seem competent enough, it is to me a shame they have to resort to a "flat to 8 Hz" claim for a 12" model.

 

[waynel]

What is special about middle of the road output at 15 Hz for a 21" driver sub? Nothing wrong with it but certainly nothing special. Again these subs seem competent enough, it is to me a shame they have to resort to a "flat to 8 Hz" claim for a 12" model.

Could be worse, Kef claims that the kc62 is flat to 11hz with a pair of 6.5" woofers but cea-2010 testing shows no meaningful output at 12.5hz or 16Hz and only 80dB at 20Hz

 

[Vladimir Filevski]

That is at 2 met so ad 6dB

... and substract 6 dB because they are ground-plane measurements (half-space). The reported numbers are equivalent to full-space anechoic at 1 meter.

 

[Vladimir Filevski]

What is special about middle of the road output at 15 Hz for a 21" driver sub? Nothing wrong with it but certainly nothing special. Again these subs seem competent enough, it is to me a shame they have to resort to a "flat to 8 Hz" claim for a 12" model.

Special is flat response at 15 Hz (or maybe 8 Hz). There are other subwoofers with higher max SPL at 15 or 20 Hz, but their frequency response may be not flat at or below 20 Hz.
Their 12" model maybe indeed is flat to 8 Hz, but certainily with low SPL output. You can call it marketing (or worse), but it is true.

 

[Titurel]

What is special about middle of the road output at 15 Hz for a 21" driver sub? Nothing wrong with it but certainly nothing special. Again these subs seem competent enough, it is to me a shame they have to resort to a "flat to 8 Hz" claim for a 12" model.

You seem kind of hung up on size. Seriously, it's the integrator (not the box) that separates this system from most (if not all) of its (home use) competitors. Rather than compressing or limiting potentially damaging infrasonic signals, the bag end products dynamically raise (and lower) the cut-off frequency. That makes them more or less set it and forget pieces of gear,* highly desirable for environments where the user can't afford to be constantly tinkering - e.g., in the (for profit) studio, not in a rumpus room.

* Also pretty much bullet proof, compression artifact free, and relatively inexpensive.

 

[levimax]

Rather than compressing or limiting potentially damaging infrasonic signals, the bag end products dynamically raise (and lower) the cut-off frequency.

Dynamically raising and lowering the cut off frequency is a type of limiting and results in compression. There are various methods that can be used for subwoof protection, why is the Bag End method better?

 

[norman bates]

Way Down Deep II Bag End S21E

Bag End S21E

www.soundandvision.com

This was a test of a 21" bag end.

"The 21-inch-diameter driver used in the S21E was the largest in the survey, offering nominally 36% more radiating area ("bore") than the 18-inchers that will appear in Part 3. In this case, the increase in sheer driver real estate does not necessarily transfer directly into pants-flappage factor. In a system that rolls off at 12dB/octave throughout its operating range, it takes a considerable low-frequency boost to produce the same sound pressure at the lowest frequencies that 1W produces at 64Hz. At 32Hz, the power required to perform this feat is 16W; at 16Hz, the power required is 256W and at 8Hz the power is a sobering 2kW—well beyond the manufacturer's recommended limit of 800W. And at frequencies where one feels bass as much as hears it—below roughly 25Hz—the aforementioned electronic boost, and the ear's natural insensitivity to bass at low to moderate playback levels, combine to impose excursion demands that a single driver—even a 21-incher—simply can't meet."

"Inspection of the frequency-response graphs produced by the dozen subs in the survey reveals that the Bag End plumbed the infrasonic range deeper than even its largest competitors, reaching an honest 10Hz. But those familiar with the curves of equal loudness will view the frequency-response graphs knowing that just because the microphone shows flat response down into the deepest bass doesn't guarantee the listener will experience it that way. For example, getting the 10Hz T. rex temblor in "Jurassic Lunch" to be just barely audible in dead quiet surroundings requires something like 100dB at the listening position. Even if you have a power amp with the grunt to get it to that level, and factoring in the inevitable low-end boost, or "room gain," that comes along for free in typical domestic settings, the 10Hz component may still be below the threshold of audibility in most rooms."

I prefer push pull slot loaded as woofers, think perlisten.
Shorting rings don't help harmonic distortion until more than 150hz.

PiSpeakers Forum - Push-pull versus shorting rings - Wayne Parham, June 21, 2006 at 16:18:33

 

[smygolf]

... and substract 6 dB because they are ground-plane measurements (half-space). The reported numbers are equivalent to full-space anechoic at 1 meter.

And Bag end uses half space so i would still ad 6dB to ground plane measurements

 

[Flaesh]

Can anyone explain how, in practical terms, an integrator differs from a first-order low-pass filter in terms of frequency response?

 

[norman bates]

It low passes from maybe 8hz.

It counteracts the 12db roll off of the sealed box rolling from 80hz down at 12db/octave.

I believe there is a big notch to take care of the fsb peak probably near 65hz from having the sealed design being way smaller than a .707.

 

[Titurel]

Dynamically raising and lowering the cut off frequency is a type of limiting and results in compression. There are various methods that can be used for subwoof protection, why is the Bag End method better?

It's the most benign form of compression, if that is even the correct term for its operation, Plus, the scheme is relatively fast and has near zero (audible) effect other than curtailing output below the inflection point. In other words, you almost surely would never hear it operate.

Your mind seems to be fixed on this matter. Okay, you were offended by their ads. I wasn't. I understood what they were doing and owned an infrasub for a couple of decades, during which I never heard any of the compression artifacts you imagine you might hear from it.

 

[Vladimir Filevski]

And Bag end uses half space so i would still ad 6dB to ground plane measurements

All subwoofers placed on the room floor uses half-space. For practical purposes, to avoid confusion, all SPL frequency measurements are referenced to full-space, anechoic, at 1 m. If used on floor, add 6 dB for all subwoofers.
SPL in Data-Bass are measured with ground-plane technique (half-space) at distance of 2 m - that is equivalent to full-space, anechoic, at 1 m.

 

[Vladimir Filevski]

Can anyone explain how, in practical terms, an integrator differs from a first-order low-pass filter in terms of frequency response?

Integrator is equivalent to a first-order low-pass filter with corner frequency of 0 Hz. Because such low-pass filter is not possible, double integrator applied to 0.707 Qtc sealed box is smart solution to get flat frequency response down to "0 Hz". To avoid problems with infra low frequencies, high-pass filter is applied to the double integrator, like 8 Hz at Bag End.

 

[Wolf11Man]

That is totally different effect from Bag End double integrator. Limier is just squashing dynamics, double integrator preserves all dynamics.

You simply don't understand how the frequency dependent limiter works and that "double integrator" is just a fancy word for a kind of 12dB equalizer.
There is absolutely nothing innovative about "Bag End". You can do it with every good DSP. If itis stillanalog, it is technology from the past. The whole video is a boring add, made to impress people without basic acoustic/ electronic knowledge.

 

[FrantzM]

That is at 2 met so ad 6dB

THANK YOU!
That would put that $5k Jit at 114 dB .. at 10 HZ@1m .. this is a Whopping 33 dB more SPL than the Bag' end and at those frequencies, the THD, 20% THD is not noticeable ...

Despite some attempts, my opinion has not changed. IMO those specific Bag's End subwoofers are Nothing Special, clever marketing. I am still waiting to be convinced otherwise.

 

[Vladimir Filevski]

You simply don't understand how the frequency dependent limiter works

Probably I've forgotten more than you know now about loudspeakers.
All limiters, including frequency depended ones, do reduce dynamic range. Double integrator and simple 12 dB equalizer do not reduce dynamic range.
I am using frequency dependent limiter in my professional line-array system which I designed and build.

and that "double integrator" is just a fancy word for a kind of 12dB equalizer.

In a broad sense, yes - it is "just" a 12 dB equalizer... with a twist.

There is absolutely nothing innovative about "Bag End". You can do it with every good DSP. If itis stillanalog, it is technology from the past.

When the patent for double-integrator was applied (1982), it was innovative - nothing similar exist on Earth. Back then, DSP didn't exist, all have to be done in analog.
Now, probably it can be fully realized in DSP... with that pesky time delay, albeit...

The whole video is a boring add, made to impress people without basic acoustic/ electronic knowledge.

I didn't watch the video, I never watch YouTube videos. But I did check who made this video - it is not Bag End company, but companies Acurus/Aragon. Blame them, not Bag End.

 

[KSTR]

There are several ways to dynamically reduce ULF output to fight the iron law of excursion of a sealed sub going with 1/f^2.
Based on having the FR EQ'd to flat down to x Hz for low levels, and on having some kind of excursion estimator you can

• simply use the excursion estimator signal directly, soft-clipping it, and turn it back into a feed signal (inverse transfer function),
• or shift the corner frequency of a 2nd order highpass up,
• or reduce (compress/limit) the level of the lowpass output of a band-split (ideally 2nd highpass linear phase),
• or soft-clip the level of the lowpass output of a band-split (ideally 2nd highpass linear phase),
• or combine the last two methods so that the ULF signal is soft-clipped for a short time until the limiter sets in.

The combination approach is the most complex one to realize (we did that in pure analog back in the day) but sounded best, most natural, best compromise of apparent transient distortion vs apparent loss of level/dynamics. Dealing in the proper time constants was a challenge.
The corner frequency shift method produced some very annoying unnatural character hard to ignore once you figure out what sounds wrong with it.

 

[Vladimir Filevski]

THANK YOU!
That would put that $5k Jit at 114 dB .. at 10 HZ@1m .. this is a Whopping 33 dB more SPL than the Bag' end and at those frequencies, the THD, 20% THD is not noticeable ...

Despite some attempts, my opinion has not changed. IMO those specific Bag's End subwoofers are Nothing Special, clever marketing. I am still waiting to be convinced otherwise.

Don't thank too soon - you overlooked my answer to that post. Here it is, again:

... and substract 6 dB because they are ground-plane measurements (half-space). The reported numbers are equivalent to full-space anechoic at 1 meter.

Also, this might be of interest to you:

Special is flat response at 15 Hz (or maybe 8 Hz). There are other subwoofers with higher max SPL at 15 or 20 Hz, but their frequency response may be not flat at or below 20 Hz.

I think Bag End do cut the mustard, at least for their 21" model - here is measured frequency response at various SPL (test from Sound&Vision):
View attachment 552546
As we can see, Bag End S21E can reach about 98 dB at 15 Hz (and 104 dB at 20 Hz), which is very good for a sealed enclosure and a single driver. There is a reason why some manufacturers are using sealed enclosures for their subwoofers.

Actually, max SPL output of JTR Captivator 4000-ULF is 108 dB at 10 Hz, with 20% THD. But it is a ported design and it has two 18" drivers.
From your table, there are 22 sealed box subwoofers and just 12 ported subwoofers. In general, ported subwoofers may have higher max SPL than sealed subs. But, as I said before, there is a reason why some manufactures are using sealed box subwoofers instead of ported ones. Comparing max SPL at 15 Hz for all sealed subwoofers with single driver in this table, it follows that Bag End S21E is somewhere in the middle. Not bad for a subwoofer described as "doesn't seem to be anything special".

 

[smygolf]

All subwoofers placed on the room floor uses half-space. For practical purposes, to avoid confusion, all SPL frequency measurements are referenced to full-space, anechoic, at 1 m. If used on floor, add 6 dB for all subwoofers.
SPL in Data-Bass are measured with ground-plane technique (half-space) at distance of 2 m - that is equivalent to full-space, anechoic, at 1 m.

I guess it did not come thru
I am comparing Bag ends measurement result vs data-bass result

 

[KL....]

Thank you, @Vladimir Filevski, Yes, to ask... do you know if the accurate timing (indicated in the video) suggests accurate/absolute phase/timing (ie low/very low group delay and distortion)?

Yes, that is true.

Thank you, @Vladimir Filevski, Yes, to ask.... is it reasonable to suggest that the Bag End Double Integrator is Encapsulateing the Driver, that is in the Analogue Manner/Process of GFB/NFB, PFFB, or perhaps Pre Driver FB?

That is totally different effect from Bag End double integrator. Limier is just squashing dynamics, double integrator preserves all dynamics.