C-1 is for cookie. that's low enough for me.
August 28, 2022 8:10 PM   Subscribe

I support this technology and this post.
posted by latkes at 8:32 PM on August 28, 2022 [1 favorite]

There's a song I always use to test systems like this. Chemical Brothers - Under the Influence. The link skips to the relevant part. On powerful systems it really curves your brain. Even people who've had their system for a while tell me that this song revealed it's true power.
posted by adept256 at 9:09 PM on August 28, 2022 [3 favorites]

"Why would you overload the bass like that? You can't even hear the music!"
'It's not about the music. It's about the hair trick'.
posted by bartleby at 10:09 PM on August 28, 2022 [5 favorites]

Came here to suggest that tune but adept256 beat me to it.

If played on a loud enough system, it can act as a replacement for dusting.
posted by happyinmotion at 10:16 PM on August 28, 2022 [1 favorite]

I'm just going to leave this good ol' electrofunk booty bass test thingy right here just in case anyone needs to test their subs: THX - Ultimate Subwoofer Test

Honestly I think Cookie Monster needs more total displacement and surface area and less fun fur. Those 36" square kickers are sweet and all but you could fit like four of those in there or augment it with a handful of 18 inchers and some more ports so it's less choked up.

And I sure hope that young person has some nice earplugs in their head.

This is reminding me of my favorite 90s LA rave sound systems.

There was this soundsystem crew called Tonka that had like 16 Cerwin-Vega L-36 Earthquake ground hog scoops, each one paired with I think dual 12 or 15" EV full range mids or kickers with loaded horn and JBL turbosound bullet tweeters, and the whole rig was painted and trimmed in a really fun black and saftey yellow industrial or Tonka Toy themed paint scheme, all nicely tri-amped with something like 15-20k watts of real big iron Crown class A/B analog amps all tied together with a DBX DriveRack PA crossover and delay timer.

And that rig was so fucking loud and deep it could blow your shirt right off and steal your wallet.

Imagine, if you will, two pairs of walls of speakers like 8-10 feet high and 20+ wide out in the middle of nowhere in the Mojave desert like someone dropped off a bunch of brightly colored Tonka toys or even looking very serious industrial equipment just pumping out the beats for 2-3 days on end, day or night.

Back to Cookie Monster?

Honestly I'm kind of surprised I never saw a sound system covered in fun fur and googly eyes like a bunch of blocky and freaky muppets. Even if only as a temporary sound system costume. It would get filthy as a permanent thing, but as a temporary thing or removable covers or something it sure would please the speaker huggers and put a smile on their face.
posted by loquacious at 12:46 AM on August 29, 2022 [4 favorites]

I know I have finally turned the corner and am heading into 'teh olds' officially, because all I could think about while watching this - and the other links in-thread - was.... "permanent hearing damage"

(Says the guy who has rarely been to concerts, never worked in an industrial facility, but now has 7% hearing loss in one ear due to 'early 90's Sony discman' abuse...)

But that was fun, cute and silly - so, loved it anyways.
posted by rozcakj at 4:51 AM on August 29, 2022 [3 favorites]

Easy subwoofer test: Edge of Tomorrow opening sequence. Don't do it too loud; it's a ~10hz sine(-ish) wave.
posted by GCU Sweet and Full of Grace at 5:49 AM on August 29, 2022 [1 favorite]

My opening track on a playlist I just called "Bass Terror" - Blvck Ceiling's mix of Psychic Rites' 'Killer', best played at a volume that makes your teeth buzz in your skull
posted by FatherDagon at 7:01 AM on August 29, 2022

One doesn't have to be old to be wise with regards to hearing damage. I've always carried earplugs and eschew over-amplified live music. I'm 55 and still have excellent hearing and no tinnitus. It's possible to live in this modern world and not gradually edge towards deafness. It just requires constant vigilance.
posted by seanmpuckett at 7:02 AM on August 29, 2022 [2 favorites]

Anyway, the nice thing about bass is that you can still enjoy it while you've got earplugs in saving your actual hearing from shatteringly loud mids and highs.
posted by seanmpuckett at 7:04 AM on August 29, 2022 [1 favorite]

I've thought about sharing this as a post but it's also relevant here:
Rotary Subwoofer

Pretty novel invention from the last 20 years. Mount a speaker coil on a fan hub, and use a linkage to make the coil drive a pitching motion on the blades. Add in a little post processing to get the math right, and you can produce bass you can hear, bass you can hear and feel, and bass you can only feel because it's too low. Single digit hertz with very high SPL.
Here's a short video of the blades moving
And here's a video of the whole thing running
Having a video of the demonstration is pointless from a sound perspective. But you can see things like doors moving inches.
posted by shenkerism at 9:16 AM on August 29, 2022 [4 favorites]

Interesting idea. I wonder if you could achieve the same thing with a mechanically simpler build: two fans in the partition wall, one blowing in, one blowing out, with servo-controlled apertures in front of each fan. You don't have to vary the fan speed or blade pitch, you just vary how much air you let pass through the apertures, opening/closing them in opposition.
posted by seanmpuckett at 9:59 AM on August 29, 2022

This won't test the bass on anything, but I do always look for a reason to post Cookie Monster (and The Count) doing (If I Knew You Were Coming) I'd Have Baked A Cake.

And yes, CB - Under The Influence is a total bass burner. (I'm overly fond of CB generally, really.)
posted by hippybear at 1:44 PM on August 29, 2022

> Rotary Subwoofer

i actually found that link the other night but i still don't really understand how it works
posted by glonous keming at 2:14 PM on August 29, 2022

It's a subwoofer... and it rotates. That's pretty simple?
posted by hippybear at 2:16 PM on August 29, 2022

Okay, I'll provide an actual answer.

A loudspeaker functions by making pressure waves in air. Usually this is by pushing a diaphragm in and out by using an electromagnet wound within a regular magnet. Think of it as a linear motor if you want. Positive voltage pushes the diaphragm forward (say), making higher pressure in front of the speaker. Negative voltage pulls it back, reducing the pressure. Do it fast enough, you get sound humans can hear.

The rotary fan speaker also generates pressure waves. Most fans have angled blades and push air in one direction, increasing pressure in front of them as they run.

Now imagine a fan running at a constant speed with blades that are flat. It spins but it doesn't move any air. If you change the angle of the blades in real time, you can change the pressure the fan generates. Angled one way, pressure builds in front of the fan, angled the other way, pressure builds behind it.

The blades in the rotary subwoofer are angled back and forth in realtime by a linkage to a linear motor (like the one in a regular diaphragm speaker). Positive voltage tilts the blades one way, making the fan push, negative tilts them the other way, making the fan pull. in effect it creates pressure waves just like a diaphragm speaker, but the force is provided by the fan blades, not a flexible moving surface.

The advantage to the rotary fan subwoofer is that there is a minimum speed a diaphragm speaker can effectively operate and still produce sound, otherwise it's just slowly shoving the same air back and forth, wasting energy in the form of heat. The fan speaker actually moves air into and out of the listening area, increasing and decreasing the pressure dynamically, with very little loss as heat.

Another advantage is that a diaphragm speaker has a limited amount it can move, called the excursion. Even very expensive, large subwoofers don't have excursions over 3-4 inches, as the diaphragm material itself cannot sustain that much stretching and still resist the air pressure it generates without rapidly disintegrating. The rotary fan speaker has essentially unlimited excursion, as it can add pressure in one direction for an unlimited amount of time. Thus the believable claim that it can reproduce very deep, sub-audible frequencies effectively.

I hope this was clear?
posted by seanmpuckett at 3:20 PM on August 29, 2022 [2 favorites]

I will add one note -- that the "math" required to make the rotary speaker work without distortion is based on the fact that when the fan blades are tilted in one direction, pressure is constantly added. Whereas when a diaphragm is pushed in one direction, a specific amount of air is moved.

This is the difference between velocity and position; the rotary fan speaker should get the derivative of pressure change over a given time, while a diaphragm speaker gets an actual amount of air to move over a given time.

OK back to cars that go wub wub wub
posted by seanmpuckett at 3:29 PM on August 29, 2022 [1 favorite]

I've thought about sharing this as a post but it's also relevant here:
Rotary Subwoofer

I've been fascinated by that system for years now, but as I understand it a major challenge to that system is that it only works with a treated, sealed listening room or theater and it can't be used for something like a mobile sound system or PA.

It essentially turns your listening room or home theater into a giant bass bin.

Which implies a lot of things, like it won't work right if you leave the door open or open any windows because that would mean you just changed up the natural resonance and port size to your room-sized subwoofer.

While may audiophiles have no issues with acoustically treating or tuning their listening rooms or home theaters the rotary "paddle" subwoofer is on a whole different level of architectural modifications, and I would reckon and reason that the rotary needs to be tuned and tailored to the size of the room it's built into.

Another unique and still fairly rare option for super deep sub-bass articulation is servo drive bass, also sometimes called direct servo drive and other names.

This kind of system replaces the normal electromagnetic voice coil and magnet system pushing/pulling on a speaker cone or plate with a purely electromechanical drive system that moves a cone or plate mechanically. You can get more accurate bass extension and articulation in the really low frequencies because of how voice-coil-driver cone speakers and tuned enclosures work.

The problem with voice coil drivers is they absolutely must resonate and be able to oscillate and cycle through their positive and negative displacement cycles to make noise or move air. Every time that coil and cone moves forward it also has to move back in a sinusoidal manner, and the larger and slower those excursions are the more watts it takes to keep it moving.

The traditional voice coil subwoofer or bassbin is tuned like an acoustic or analog instrument and uses the natural resonant frequencies of the enclosure, porting and size/power of the coil/cone speaker to mitigate these power requirements. Think of a bassbin as a guitar or piano string. If you want a string that will resonate loudly and at high amplitudes at something totally ridiculous like 1 hz - and be acoustically efficient, tuned and self-resonanting - it's going to need to be absolutely huge and massive, and it would take a lot of energy to pluck it or move it just once, and it would also need a huge resonant structure or acoustic enclosure and sounding box to be an efficient instrument.

This is why subwoofers can't reproduce mid or high range tones very well even without a low-pass crossover or filter that eliminates anything above a certain frequency range. The enclosures, ports and driver are all tuned to resonate more at specific frequencies to help save amplifier energy and require less peak watts to drive and move.

The rotary subwoofer concept gets around all of this resonance and excursion problem - if only in the driver/enclosure and energy requirements - and it is effectively a type of servo drive system that really only pushes air and doesn't have to also pull to resonate and cycle at the cone and driver level. It uses sheer horsepower and rotational mass with rotating vanes to basically slap the air at you and into your listening room like some kind of bonkers overpowered industrial tool or construction equipment.

In the audio and sound world getting good bass articulation is a very well known problem.

Traditional voice coil and driver cone systems struggle a lot with super deep bass because of how the power requirements ramp up exponentially the deeper you try to go, which leads to major mechanical issues like electromagnetic voice coils overheating, melting or even expanding in their sleeves inside the permanent magnets or simply just requiring far too much amplifier power to keep them moving at lower and lower frequencies.

This is one of the reasons why mastering and producing bass music can be so technically challenging. It might make sense to a music creator or producer to want to create music or a mastered mix that contains frequencies below 30 hz, but even most high end audiophiles or bass heads don't normally have speakers or sound systems that can efficiently reproduce anything that low.

Paradoxically one of the recipes for mastering music for good bass is a combination of using a conservative high pass EQ or shelf that cuts off everything below about 30-40 hz, and combining that with a technique where you add or include tones that are second order harmonics above your root bass tones.

IE, if you have a 30 hz bass tone in your mix you'll want tones or semitones at 60, 90 and/or 120 hz or even secondary/tertiary tones so there's a more acoustic energy at higher tones more likely to be able to be reproduced by a given set of speakers or headphones and there's a little bass for everyone whether or not they have a true sub-bass speaker or a crappy little bluetooth speaker or soundbar with tiny speakers and less available watts than an LED light bulb.

This also all maps to the professional sound system and reproduction world on systems whether they are small or very, very large.

Part of the basic science of high fidelity, broad spectrum audio reproduction is the use of things like crossover filters. A crossover filter is basically a multi-channel, multi-band equalizer or high/low pass filter or other frequency shaping filters.

In a traditional passive home hi-fi speaker with multiple drivers that you hook up to an amplifier/receiver from, say, a single amp and audio source, the "crossover" is a physical, electronic frequency filter that divides the frequencies and distributes them to the correct drivers that can efficiently reproduce and resonate at those frequencies.

But part of how a well designed crossover works is that it completely eliminates or mutes frequencies below or above what a given driver and enclosure design can efficiently resonate at. A good passive crossover doesn't just send 0 hz to, say, 150 hz to the woofer or sub, it only sends or permits everything above and/or below a given frequency, within the efficient resonance of that speaker.

For bass this typically means cutting off everything below as low as 20hz or even as high as 70-90 hz, depending on the speaker.

On the larger end of the spectrum at, say, a huge electronic, dance or bass music festival with truckloads of speakers and dozens of large bass bins, they do the same kind of thing with programmable DSPs, crossover filters and other ways to control and shape the sound and frequency response, all in the name of maximum efficiency as measured by sound amplitude, frequency and energy efficiency.

The paradoxical part and punchline and point to all of this nerdy audio engineering stuff is that by eliminating the frequencies that a given speaker can't efficiently reproduce - as well as the frequencies most people can't hear anyway - it leaves more energy for the for the speaker-enclosure-amplifier system to work more efficiently at the frequencies we can hear, thus paradoxically making the bass feel and sound louder, cleaner, tighter and more responsive.

I've experienced and messed around a lot with both sides of this in the process of making and mixing electronic music as well as tuning the crossovers and DSPs of some fairly large and loud sound systems.

I've seen some really bonkers stuff like large rave/party sound systems doing nothing but play pure analog synth bass tones making desert sand vibrate and levitate 50 feet out in front of it.

I've heard bass so low and loud that it makes it difficult to breath and starts messing with your heartbeat like you're getting CPR.

I've even seen someone blow pairs of 18" speaker cones right out of a pair of DIY subwoofers because the ports were too constricted and they decided to hook up their synth to it, crank the gain path all the way up and throw pure sinusoidal 1-5hz tones at it as a bass test. It sounded something like boom-woof-riiiiiip as the cones exited the driver basket and cabinet.

I once more or less accidentally used these techniques to tune a fairly modest, traditional and rather beat up tri-amped mobile techno sound system in the 5-10k watt range and somehow got it so tight with the DSP controller/crossover unit that it was rattling things to pieces hundreds of yards away and you could hear it and feel it 3-4x farther than normal.

It was so much louder and bassier that I was politely but firmly requested to never use those settings indoors at our warehouse ever again and de-tune it a little just so it didn't unduly annoy every last one of our neighbors within a half mile radius and force SFPD to show up to have a "please don't do that we can clearly hear you on the other side of a major freeway interchange wtf how" sort of chat with us for the first time in a few years when they had previously expressed they'd rather leave us alone and not have to deal with us at all.

When you get these frequencies right - specifically the lack of certain frequencies - it's magical.

A given song being produced and mixed, or a home audio system, or an entire pro audio speaker system will go from sounding mushy, muddy and washed out in the bass frequencies to amazingly tight, much louder sounding, much more noticeable bass mainly because - technically speaking, and paradoxically - you merely turned down some of the bass in the right frequencies so the easier to reproduce part of the bass has more room to play and soak up the watts and resonate freely and more efficiently.

The science of audio engineering is fascinating and wild, but it gets super weird especially when you start dealing with bass and sub-bass and how speakers work.
posted by loquacious at 3:52 PM on August 29, 2022 [1 favorite]

Oh, and I meant to talk about servo drives and why they're not more popular.

It's mostly because they don't inherently resonate, therefore they're not - generally speaking - acoustically or electromechanically efficient, thus they take even more energy. They're also mechanically more prone to wear than a voice coil and magnet setup because there's more moving parts and more mass involved.

Despite the limitations of a tuned, resonant voice coil and cone driver bass bin, the beauty of it is that it's acoustically and mechanically efficient. There is very little mass even in very large speaker cone. Technically speaking there's no wearing parts experiencing friction, as it's a flexible speaker cone surround and the base of the cone where the electromagnetic coil or transducer is floating within the field of the permanent magnet with no physical contact.

Barring severe electrical abuse or physical, environmental damage the main part of almost any given modern coil-cone kind of speaker is the chemical or material breakdown of the flexible baffles that support it in the speaker structure and basket.

That resonance actually improves frequency change responses within it's given, tuned frequency range whether it's a bass bin or full range speakers. One of the terms for this is articulation, extension or response.

Mechanically speaking that means it can change velocity more quickly within that range of efficient resonance because the only part that's really moving is that cone and coil and it's efficiently resonating in an enclosure.
posted by loquacious at 4:11 PM on August 29, 2022

> I hope this was clear?

yep i understand now, thank you! i had failed to grasp the fact that the blades were able to change between "pushing" and "pulling". i was thinking "it's a fan, it blows one way? i don't get it?" now i get it.
posted by glonous keming at 4:16 PM on August 29, 2022 [1 favorite]

This kind of system replaces the normal electromagnetic voice coil and magnet system pushing/pulling on a speaker cone or plate with a purely electromechanical drive system that moves a cone or plate mechanically.

I get that there's some discussion about whether they're "really" servo, but that's not how Rythmik subs are described as working. The owner/designer describes it as using a second voice coil to generate a feedback signal that goes back to the amp for comparison and correction.
posted by GCU Sweet and Full of Grace at 4:48 PM on August 29, 2022

I get that there's some discussion about whether they're "really" servo, but that's not how Rythmik subs are described as working.

Yep, those aren't the kind of servo drives I'm talking about. I'm aware of Rythmik's take and technology and as I understand it they're using feedback sensors with traditional voice coils to improve accuracy and frequency change response times, but not necessarily efficiency per dB or SPL in the bass and sub-bass range.

Technically speaking they are a kind of linear servo drive due to the position sensing and feedback.

Which is cool technology but is kind of overkill if you're still working with the traditional design for a tuned, ported enclosure with a voice coil woofer. If you design your enclosures well and use good drivers with good crossover settings the frequency change response time issue is a fairly well solved problem for this general kind of speaker design - and I have doubts about how useful this is for sub-bass extension and articulation considering any feedback/sensor induced changes are going to be fighting against the natural resonance of a given enclosure anyway.

I'm talking about big iron PA subwoofer speakers like Danley's ServoDrive systems, like this:



That first Reverb link has pics of the mechanical linkage for the dual drivers and you can see how complicated it is compared to a voice coil. It uses a servo motor with it's own internal limit/position sensors like most proper "servo" motors do to keep from over-running the drive belt limits.

While this system can produce amazing bass to infra-bass ranges it has some known problems with the noise of mechanical system, servo drive and belts as it moves. This is one of the benefits of a voice coil system is that there's not really any moving, wearing parts as the coil floats in the magnetic surround and is never, ever supposed to make physical contact with it.

Interestingly Danley has introduced new bass/sub-bass drivers using a new-ish kind of "tapped" loaded horn bass driver and/or fully integrated full spectrum speaker systems that are an interesting, modern retake on the "coaxial" or "concentric" speaker designs that solved the issue of delay timing and comb filtering issues of combining multiple drivers in a single enclosure by stacking or otherwise aligning them into a linear stack or combining multiple drivers and cones in the same structure so that from the listening perspective and axis (call it X, or depth) they were lined up in the Z and Y axis, or up/down, left/right.

The PAS coaxial speaker is an example of this with a loaded horn tweeter mounted inside of a 15" subwoofer, and a long time ago, for many years these designs were some of the best in the industry for PA speakers, but fell out of favor when affordable DSP PA drive systems became more widely available to deal with the issues of speaker delay timing and crossover settings all in one easy to use rackmount box.


These coaxial/concentric designs also had major issues and limitations, like manufacturing costs due to overly complicated driver arrays, having the mid/high range drivers acoustically obscuring the larger drivers behind it, and issues with acoustic/mechanical coupling between driver elements destructively interfering with each other and introducing unwanted distortion.

As I understand it Danley has been using advanced computer-aided acoustic design to combine the outputs of multiple drivers into a single horn or range of horns. Basically the sound starts with the bass driver at one end of a loaded and (I believe) a non-symmetrical horn-slash-waveguide kind of rigid physical shape and then midrange and higher range drivers "inject" their frequencies into the same horns at appropriate points or resonance modes along the horn-slash-waveguide.

With a lot of pro audio PA speakers like this the key is efficiency and how to maximize available watts/energy from the amplifier into real world SPLs, and loaded horn speakers are some of the most efficient speaker designs in existence, the same way that a trumpet or other brass/horn instrument is very efficient at producing very high SPLs in a given frequency range and sets up standing acoustic waves within the horn.

Sorry if I'm nerding out too much in a fun, silly thread about Bass Cookie Monster but I love this stuff and I love bass.
posted by loquacious at 3:26 PM on August 30, 2022 [2 favorites]

I'm talking about big iron PA subwoofer speakers like Danley's ServoDrive systems, like this:

So it's like an old-timey GAWOOOOGAH horn that's hit the gym and lives in a very special condo?
posted by GCU Sweet and Full of Grace at 6:39 PM on August 30, 2022

So it's like an old-timey GAWOOOOGAH horn that's hit the gym and lives in a very special condo?

Actually, nope, because those use reed diaphragms, lots of air pressure and a loaded horn, like a military grade bugle on juice and gear.

The ServoDrive bass is more like you replaced the wimpy brushed motor in a old NiCad cordless drill with a massive brushless motor and a major portion of a Lithium Ion Tesla battery pack.

If these metaphors aren't getting confusing enough I could go get really stoned and get back to you.
posted by loquacious at 8:42 PM on August 30, 2022 [2 favorites]

If these metaphors aren't getting confusing enough I could go get really stoned and get back to you.

I remember the Jerry Garcia's Birthday weekend party where we rented a pair of ServoDrive subwoofers back in the late nineties or early oughts -- before we got a couple of pairs of EV-S181s and didn't need to rent. They were wonderful. Good thing Jeff had used a four-track (Tascam 246) to record a bunch of shows with a pair of SM-81s and a pair of PZMs to get the low-end in stereo...

"And then Mickey Hart started hitting The Beam, and we all lost our shit..."
posted by mikelieman at 7:12 AM on August 31, 2022 [1 favorite]

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