FAST BASS?! | Direct Servo Open Baffle Subwoofers!

What the heck is the big deal about fast bass? In this episode, Danny Richie walks us through all the goodies involving Direct Servo Open Baffle Subwoofers!

[@msmeyersmd8]

I’m a retired engineer/physicist and physician, a musician and an audiophile. These are “hands down” the best information I have ever heard or read about speakers. Straight forward, unbiased and useful, factual, easily understood, but still with great technical information. Thanks so much.

[@jaapdekker5983]

I totally agree

[@diggerson88]

100% agreed. enjoy listening to this guy. Can hear the experience.

[@H2oRiz]

Why does you being a retired engineer/physicist and a physician even matter. Does that make your opinion more valid? This is basic information anyone can understand. Stop thinking you are special.

[@bradenroy2617]

sorry to be so off topic but does anyone know of a tool to get back into an instagram account? I somehow forgot my login password. I would appreciate any assistance you can give me.

[@averytobias4554]

@Braden Roy Instablaster ;)

[@thefrankenator]

I am a full time Sound engineer from Ireland, Just earlier today I was telling a colleague how I felt that the Subwoofer I was testing sounded slow and muddy when playing high BPM double kick drums from a track. This explains perfectly what I was trying to describe. Thank you for such a great explanation. I learned a lot and I hope you have more content like this.

[@megamond]

The worst "one note" droning subs I've heard (even with only a modest 8" driver) had amplifier boost @ c. 60Hz for "Cinema mode" effects (LFE) - the early ones often had a switch to put the boost in and out, as AV Surround Receivers were the key sellers of subs back in the day - audiophiles tended to ignore them.

[@DJdavefromlondon]

Danny. I am a budding audiophile , physics major at school in 80s . I literally can’t stop listening to you and this was the best video of all in terms of explaining. The decay of the drum is different to the decay of the woofer … how amazing is the physics of sound

[@chrisgoodwin4786]

These are the best "audiophile" videos on KZbin! I am not an engineer, but I am a musician and audiophile, so I am familiar with what I have experienced, but I had no knowledge to understand the physics of what I hear and how to make it better, or why some things--with my limited knowledge--seem like they should work and don't. His explanations are always clear and just down right fascinating. Thank you for posting these!

[@moricemeandros3049]

Fully agree! That's because Danny comes with engineering explanations and not with snakeoil or subjective tastes

[@jamesroebuck5911]

Well done Danny, you are the only fella I know that talks about attack, decay and amplitude of bass playback and diameter of driver.

[@NickP333]

Thanks for another vid featuring Danny. His explanations of speaker design and building are easy to understand and very concise. Thanks for the intro to GR Research too. I love how your NX Otica’s came out! You did a wonderfully detailed and professional job of building them, and you should be commended for your efforts. I’ve got a 5 ft. tall pair of full range speakers in my main listening room, but I need a smaller pair of spkrs for the living room. I’m a DIY guy anyway, so I’m gonna go with the building of a pair of N3S’s with of course with Sonicaps, Mills resistors, No Rez damping material, and of course those beautifully made Electra Tube Connectors. Thanks again for your introduction to GR Research.

[@Newrecordday2013]

Thank you!

[@karlcotleanu4144]

Great!! Clear, concise explanations and excellent descriptions. I am learning a lot from your videos. Keep em comin'!

[@123antas]

Would be great to if you can show some speakers playing with recordings of ‘normal’ subs compared to quick base. Explanation is excellent..!

[@jamegumb7298]

Fast and tight, no smear. Always sealed for me, and my latest is a dual opposed driver one. It is absolutely fantastic. No rumbling or shaking floor, but low, fast, really get sound not a trembling floor. Thinking of stepping it up to dual opposed isobaric cone to magnet.

[@siletteman]

After 27 years listening to hi fi, finally I've understood why my subwoofer increases bass, but smears the overall sound ! Thank you so much. Keep making the videos.

[@TimpBizkit]

Because lower frequencies are naturally longer period and less "fast" we are talking about the effect over several cycles. Whilst ported and bandpass enclosures amplify a driver by resonance and making compromises in the time domain and stored energy in the vibrating ports. Any design that amplifies using resonance introduces inaccuracies in the time component of bass reproduction. It takes a few cycles for the air to get moving at maximum amplitude in the ports and a few cycles for it to stop moving again - particularly true around the box's tuning frequency. A horn enclosure will radiate away the driver's stored energy quite well because the large expanding funnel of air acts as a brake or parachute for the driver. You basically have a sealed box with an extremely light parachute on the driver. Add to the fact more SPL for your cone motion and there is less stored energy in the cone to begin with for a given listening level. A horn that is acoustically small will resonate a bit at its quarter wavelength. The mouth isn't big enough to quickly provide damping and the air column behaves like a ball on a bungee cord. An infinite baffle with an aperiodic membrane (forcing the output through a resistive sponge to damp resonances and cone energy) will do a similar job as a brake but with less efficiency because it "wastes" the cone's energy instead of converting it into sound. To be honest, by far the biggest culprit is THE ROOM YOU USE THE SYSTEM IN! Bass that sounds good in your car can sound terrible in a reverberant room, especially exciting room modes that take several cycles of the woofer to come to full amplitude and will keep resonating for several cycles after the woofer is no longer reproducing the bass note. You are either better off outdoors or in tiny acoustically dead rooms if you want "fast bass" - the "infinite room" and the airing cupboard! Or use a pair of headphones!

[@littlegandhi1199]

In regards to the room > I believe this is where using an open baffle sub box will lower the excitation of the modes

[@garysmith8455]

This is why I got hooked on VELODYNE subwoofers back in the mid 90ies. I STILL enjoy my Velodyne F-1500-R Servo controlled 15" driver. Also had the lowest distortion ratings of any subwoofers at the time. Thanks for your informative video!

[@rtimmins7212]

Thanks Danny, great video and explanation. I have been wanting to build an H Frame Servo sub for a while just haven't bit the bullet yet. See you on the Circle.

[@Qui-9]

I used to have this subject in my mind and even built servo amps to achieve "fast bass" (or transient response in my day), which is basically emulating a larger magnet, but in the end, all it really came down to was frequency response. If there were any *changes* of slope in frequency response, like a rolloff knee, especially more than first order, or furthermore an actual resonance, at a rolloff knee or anywhere else in the spectrum, that's where the output signal would "ring" and wouldn't track the input signal accurately. In a speaker driver, it's not the cone mass itself which reduces fast bass, it's a rolloff induced by a high inductance coil, a pliable cone with damping properties to reduce internal material resonances, a similarly viscoelastic suspension or other parts of the driver, the off-axis response of a larger diameter driver, the fundamental moving resonance of the driver/enclosure combination remaining after motor damping, the presence of a bass-reflex, transmission-line or other reactive function with a resonance or comb-filter group delay response, and internal enclosure resonances, either in air or from the panels. Down to the driver, you can use as heavy as a moving mass as you want, that alone isn't the cause of any upper rolloff... A steel cone could easily create fast bass, as long as the resonance of such a heavy system remains controlled by the motor. Therefore, even a big heavy woofer would easily play a note instantly and stop instantly. There's no stored energy at most frequencies because they aren't part of a resonance, and the resonance of sub/woofer systems with a flat response and gentle rolloff knee is so well damped to be of little significance. The mass simply limits the acceleration of the cone, and the motor boosts that but limits the top speed. Drivers don't have any difference of envelope response (speed of bass) if they have a relatively wide, flat frequency response, are used properly in their range, and combined likewise into a proper multi-way full-range system. Also, using multiple drivers driven to less excursions has nothing to do with the response, or "settling(resonance)", because it's not an amplitude-dependent phenomenon.

[@dannyrichie9743]

I'm sorry but the exact opposite is true regarding some of those things you went on about.

[@rotaks1]

Thanks for the great education! Please keep these coming. In my case, I don’t know what I don’t know and so these episodes are really enlightening.

[@russelhaxby6194]

These Tech Talk videos are great. I gotta go back and make sure I've seen them all. If you ever feel like talking about horn tweeters or passive radiators, I'll be all over that one.

[@johnnestor7386]

The best explanation of fast bass I've ever heard. And frankly, that applies to every informational video I've heard you do on topics related to audio. I subscribed after the first video I saw, and have been basking in your video catalog ever since. Thank you for all of your hard work, all while entertaining and enlightening myself and others. Cheers, John

[@johnhodgson5313]

I just found this, thank you for your explanation. I am going to add something. 2 cabinets, different designs, but they used the same drivers. They were commercially available and the popular opinion was that the one cabinet made "faster" bass than the other, yet all the drivers were identical. I happened to have both and started experimenting. I discovered that there was one panel in the "slow" cabinet that did a lot of ringing. I did overkill bracing of this panel and after that the "speed" of the 2 woofers sounded the same 2 me. So cabinet resonance can add to the signal decay and make it sound "slow".

[@mkshffr4936]

I think this may be the biggest part of it because fast=high frequency. But what people are hearing is really a "smearing" due to some kind of resonance whether it be the driver, the cabinet, a helmholtz resonator or whatever.

[@larydixon4824]

Hi Danny, Excellent video! You're helping people to see a simplified perspective on topics that can be very difficult to understand. You are doing a great job of keeping the industry alive and interesting! Thank you my friend! Lary

[@moricemeandros3049]

extremly educational! many thanks for your time explaining these speaker topics!

[@Spawndukes]

I like the monsoon computer speakers in the shelf there. I had a set way back. Wish I still had them

[@markroze3641]

I have a low tuned, vented PSA subwoofer with an 18” B&C pro grade dvc driver (with a neodymium magnet) and it stops on a dime. The bass is super clean. No muddiness or overhang. Just Extremely precise bass. I get deep extension and great mid bass output too.

[@loulopez7808]

Awesome video. I learned a lot. PS Audio’s new speakers will use a servo controlled sub and I wonder why more speaker & subwoofer designers don’t incorporate them.

[@ronbradshaw7404]

Yes sad, as this is NOT a new invention!. Thanks to Infinity, 3A and Phillips, they had this technology in the 70's

[@nh18343]

Because if done cheaply is sounds terrible. And most people have no idea how good things can truly sound.

[@mkshffr4936]

Diminishing returns. It is costly and complex.

[@kennethcohagen3539]

Danny, during the intro I see a lot of my friends from that same era. Cool stuff! Thanks for all you do.

[@markyoung7470]

Great job Danny keep the video's coming I really enjoy your perspective on Home Audio.

[@christopherward5065]

Superb explanation. I have not enjoyed subwoofer bass before it always sounds false but, the notion of servo controlled open baffle bass really appeals. It should allow the envelopes of bass notes to be heard more accurately. Thanks for explaining

[@1mctous]

The concept resembles negative feedback in amplifiers. The sensing coil provides the feedback which in turn corrects the audio driver stage and thus the output.

[@Blacklighting]

Love this guy. I always wanted a Rythmik F12g sub... or two.

[@kimbothwell917]

Thank you again Danny! I enthusiastically agree with the learned gentleman below; clear, to the point, understandable, and useful!

[@AntsAasma]

One thing to note is that a speaker is only a part of the whole audio system. A speaker driver that can stop on a dime is of very little use when the room keeps ringing like a bell.

[@VioletGiraffe]

But we don't perceive sound literally, our brain detects reflections as reflections as long as they're delayed enough. A ringing room will spoil the sound for sure, but it won't necessarily make fast base kicks sound slow.

[@TheJohnsofDoes]

Actually, it makes a huge difference. I was forced to use my Rhythmik Sub in a project studio a few months ago that was mostly for song writing so little to no treatment or management of RT60 times in the low end..with the rubbish Yamaha HS8's with matching sub they had set up, like you say everything rang like a bell..i simply could not work with that set up so went out my way to bring my own studio monitors and sub down, and even in that very reflection driven room, it was pretty obvious that the Rhythmik sub performed by quite a margin better and articulated better than their setup which everybody confirmed and had assumed that a sub was supposed to just sound like the audio equivalent of a tub of lard. Within the nearfield that sub sounded just as snappy as it did in my treated/designed room, as it did in that shitty room to especially my surprise. Their surprise was mostly that a sub could sound that "fast". A better room simply just amplifies those benefits by a much greater magnitude, but the differences can be of benefit to people who do not have acoustically treated spaces as well. Placement obviously makes a huge difference and finding the best place in this room wasn't too difficult considering it was a pretty large room

[@Artcore103]

this is why headphones or especially iems, have the fastest bass. physics. and it IS about tracking the input signal. not about the speed the driver moves, you were right about that, but it IS about tracking the input signal. any additional cone movement that is from stored energy / momentum is by definition NOT following the input signal, hence the servo systems! they attempt to force the driver to follow the input signal exactly.

[@cyesso2141]

I think I just graduated to a new level of understanding, and I am off to throw all of my speakers away!! Fast bass awaits!! Seriously though, a truly fantastic explanation that connects the dots and demystifies a lot while at the same time giving a new direction.

[@benjaminmontgomery4697]

Excellent Short description of cerrvo driven cones. Thank you for the vid.

[@svtcontour]

I think the idea of a heavy cone being slow is wrong. A speaker with a heavy cone (moving mass), could have a big motor with high magnetic field that can still control the movement of that heavy cone so mass alone is not an indicator. Likewise a light cone with a very weak motor can still be uncontrolled. I think the overall QTS of the driver can be a good indicator of what will be happening with regards to control. Just my thought.

[@PaulHobbs23]

True, but all things being equal, making the cone heavier increases the transient uncontrolled response.

[@svtcontour]

@@PaulHobbs23 Its true, but one must always take the complete specs in consideration, not only the moving mass :) So the most correct statement would be that cone weight alone is not a determining factor to transient response. Just my two cents :)

[@randomtube8226]

Fast bass should refer to the woofers aerodynamics. If someone wants fast bass all they have to do is use a small woofer. Small woofers are lighter in weight and can cut through the air faster than larger woofers. Now fast and low bass is a challenge. Large woofers are slow but can go low. Small woofers are fast but struggle to get low. Servo control is a way for large woofers to be fast and line array of smaller woofers is a way for them to go low. Aerodynamics and air displacement is what we're dealing with here.

[@pssound9749]

Hi, Thank you for this great video! Finally i don't have to cover this topic and i can just share it straight to my customers! Beautifully described! ;)

[@truthhouse8]

Have a friend who just got a pair 521.4 Libwitz with dual opposite firing woofers in each cabinet are those servo woofers.

[@dannyrichie9743]

No, those woofers do not have servo control.

[@Gersberms]

You haven't mentioned room acoustics at all, I've heard plenty of rooms storing a lot of bass energy. Especially where ports are near the wall! It can really ruin the experience. One question though: how different is amplifier servo control from amplifier feedback? Amplifier feedback is used to keep speaker cone movement in check too, isn't it?

[@dee1458]

I've been enjoying dual Paradigm Servo-15s for ~15 years now and they're just delicious for both music and home theatre. I will highly consider Danny's Servo or OB offerings as replacements one day.

[@EVILUTION9]

I have learnt so much from watching this video. This explains now why my Bose 802's sound so good with small drivers!

[@aitchr8770]

Now this is a good one. The effect of the electronics on the harmonics at those frequencies are not detectable to the human ear so the effect is minimal, so it is a good thing to have in the signal path, an improvement. Where as higher in the frequency range the less you have the better (Dannys description of design the driver right and then use less cross over)

[@zulumax1]

Attack and decay of the midbass is more gratifying than sloppy deep bass. JBL D130 driver can do it too, you need a short throw low compliance driver to do it on a larger woofer, just don't expect much output below 50 Hz. long throw woofers have much of the coil not in the magnetic circuits control which looses damping and wastes power to heat. ZU audio, Klipsh, Altec to name some others. Has anyone done a line array of the smaller 3 inch drivers to bring up the SPL potential? In 1968 Bose 901 used multiple 5 inch drivers to create quick midbass never possible before at the time and had high SPL as well.

[@jespencer7805]

Phillips did ‘motional feedback’ in the 70’s. I am surprised it isn’t used more widely given the possibilities with DSP nowadays?

[@ScottGunMag69]

Thanks for this explanation. It really makes sense.

[@martinlarbi5896]

I have used a servo velodyne sub woofer for over 20 years and l now understand the science behind it. Thanks.

[@HoomanR17]

Thank you for the super helpful information.. Do open baffle servo subwoofers blend well with "closed/box" bookshelf speakers or just with open baffle speakers?

[@dannyrichie9743]

Open baffle servo subs can be used with any design.

[@jarvislarson6864]

"Fast bass".....in car audio i tend to look to amplifier specs and the higher damping factor the better. Is that right? Ive always considered myself an audiophile but closest i ever got to audiophile quality gear during the 90s height was alpine head units linear power amplifiers and image dynamics highs with black gold mtx subs...only dreamed of McIntosh

[@justingillette8287]

I gave thumbs up, and subscribed based on this video, this is good content. I look forward to more.

[@billmilosz]

What I've found is that having a heavy stiff cabinet enclosing a woofer - which is good for damping vibration in the upper bass / lower midrange to keep the cabinet from radiating at those frequencies- this cabinet will store low frequency energy from the woofer cone motion and then release it over time. Cabinets smear bass. Even the frame of an open-baffle woofer will do this, but because an open baffle frame isn't being driven by air trapped in an enclosure, it happens much less than with a cabinet enclosing the woofer along with a bunch of air. DISCLAIMER - I am a panel speaker guy, I own Magneplanar and Quad Electrostatic speakers. I have open baffle servo subs for the Magneplanars, no subs for the Quads they are in a small room and mostly used for more "polite" listening.

[@CthulhuOO7]

Best money I ever spent in audio is my Rythmik F12. It's SOOOO clean and deep. I'm in happy tears every time we watch a film.

[@scottyo64]

Wow really interesting subject! I have always heard you needed a fast sub for magnapan speakers. Small and sealed.

[@The-Spotlight-Kid]

i'm convinced. & have already heard folk extoll the virtues of modern Servo-controlled woofers, like "you can't go back.." I've owned all designs (minus maggies) & have long intended to own O.B. for my next & lasr speaker. Mainly from taking note of 'GR -research' & 'New record day' vids & guests they had. A servo controlled open-baffle woofer (or 2?) on each side has to be the icing on the cake. & flat to 20'Hz & -3'db in the teens, if my room can do those wavelengths(?) would be like nothing ive heard at home! 132'ft Gottenberg(?) Cathedral organ pipe, easy(?)

[@hjnorlander7124]

How far up will an OB sub go? Can it be paired directly to the mids? Would be nice building an open baffle for the mid and tweeters and an OB sub in the bottom of it. Thanks.

[@Newrecordday2013]

Acoustic output can reach up to around 2-300

[@diegogonzalezplascencia6590]

Nice video. Really just commenting for KZbin logarithm. Your channel deserve to grow. Cheers.

[@Chemist1076]

Lag and resonance of the cone is what he is talking about... The speaker is like a spring and keeps bouncing after the signal is finished. A low qts will help control the cone better than a high qts. Bigger magnet more control.

[@cartofgiant]

Wow good info ,, makes perfect sense.. can tell you know your stuff.. good info , and no hype.. hard to find in hi rich now a days.. thank you

[@anandshah71]

Nice video great explanation not many people have talked so well explaining on YT. My 15” dual woofers per side in OB feel so great can’t go to stereo sub in a box

[@dmark2639]

Would you say your OB subs are up to handling home theater use? Can they achieve 115db peaks in-room (THX requirements)? I know OB subs load the room differently than a box sub. I'm concerned how that "feels" when an explosion or a dinosaur is on screen...do you still get the tactile "feel" of the bass with your OB?

[@AaronAlso]

Reminds of a story from my car audio days. I used to work for a business many years ago that had a customer who want the loudest cleanest bass and price wasn't much of an object. I was asked to design a system for his long bed pick-up that would become a show car. I came up with a design that called for 96 eight inch high power subs. The whole thing would have drawn upwards of 3000watts and had a sensitivity around 98db. Despite me trying to explain the science to the customer he just wouldn't have it and complained to the owner, basically getting me fired. They then installed six 18" subs in his truck and barely hit 92db of sensitivity. Sure it was loud, but it sounded like garbage and as I was told he never did win any competitions.

[@SheikhN-bible-syndrome]

Sensitivity is measured at 1 watt 1 mm away what exactly are you referring to buy sensitivity?

[@AaronAlso]

@@SheikhN-bible-syndrome It is 1 watt @ 1 meter @ 1KHz if we want to be technical. Sensitivity is really a measure of how efficient the driver is at converting electrical energy into sound energy. Doubling the number of drivers effectively increases Sensitivity by 3db; 2 drivers gives 3db over a single driver, then 4 gives 3db more, then 8 and so on. There is probably a point of diminishing returns but I have never tested that. Also, the enclosure design has some effect on overall Sensitivity. So packing a bunch of small drivers into the right enclosure will produce more output at lower power than a single driver at max power and have better transient response.

[@SheikhN-bible-syndrome]

@@AaronAlso not necessarily. Its driver dependent however generally speaking several smaller size drivers CAN be louder than 1 big driver because of more motor force and piston surface so the box with several smaller drivers hypothetically can handle more power and produce more "torque " therefore making more SPL. But the sensitivity has little to do with total SPL because a sub with a 98db sensitivity that can only handle 100rms will get destroyed by a sub with an 88db sensitivity that can take 5000rms because yes more power is needed but it will still far exceed the SPL of the 98db sub when both are running at there maximum output ability. And this is just the subwoofer by themselves now the boxes are a whole other can of worms

[@Ryu288288]

Awesome and helpful, my question is how do you make speakers sound fast? Can you apply the same servo technology to speakers?

[@sudd3660]

Morel and Seas produce some 10 and 12 inch woofers that have a moving mass of only 100g or thereabouts, now that is some woofers i want to build a subwoofer with. to put things in perspective the general 12" woofer moving mass is 500 grams.

[@dannyrichie9743]

Our 12" servo subs have less than 105 grams of moving mass, 18mm of X-max, and a servo control system that will stop it approximately seven times faster than an uncontrolled driver. Now that's a whole different ball game.

[@sudd3660]

impressive :) i only knew of 2 woofers that was that light. nice to hear that there is more. found spec sheet on that SW-12-08FR Servo Sub Woofer on the website now, 113grams :)

[@Boogerweldz]

500 grams? Maybe 280g for Mmd?

[@watahyahknow]

makes sense , think you need to listen in a pretty death room or a room full of people or the reflections messes up that tightness and details in a hurry

[@kenthomas1613]

Quick question for Danny... What happens if you move the drivers forward of the baffle? That is to say, what happens to the sound of the drivers if you move the drivers forward of the baffle by 10mm to 15mm? What would happen then? Conversely, what happens if you move the drivers back into the baffle 10mm to 15mm?

[@elviscaragea4433]

High Bl, low mms, not using the speaker at full power, using half the xmax, in a low qtc box, with lots of sd and low group delay. A dream

[@dell177]

Decades ago I owned a ppair of AR3a's, for the late 60's they were pretty good. They had their problems but would go lower than most speakers. Years later I had a pait of Dynaudio kit speakers that had a 6-1/2" woofer, that didn't go nearly as low but it was a lot faster than the 12" AR woofer so it seemed to have more punch. That 6-1/2" woofer was a lot beter made than the AR 12" unit and I'm sure is had better step response as well as less mass to control.

[@UnburdenedByWhatHasBeen]

Interesting. So in theory i would be better building a box with 4 6½" subs instead of 1 12" sub. My 12 now seems to have muddy bass, im wondering if this would solve that issue.

[@kaedeschulz5422]

Really depends on the driver. i have heard 5inch driver's that sounded like mush and i have heard EIGHTEEN's make me think the snare drum is in my room. That 18inch was one from the PA sector witha 4inch coil and 10kg of ferrite magnet with an insanely stiff suspension. The moving mass was around 170gramms. some 10inch driver's have more moving mass than that and a lot weaker motor. I had it playing open baffle. Never heard a snare hit that similar to the real thing.

[@xblinkusedfinchx]

great vid easy to follow. would love to see more about open baffles

[@Hudsonlee1954]

Thanks for the share. Fast and clean bass.

[@ericsmith6692]

Very Informative, thanks 👍

[@shaftoflight3497]

for the end user, the main thing is the result ... no matter what technology ... What is your personal impression of REL - T -X or Rhythmic Servo ??? which is better to listen to?

[@ThPappas]

Thank you for your video.I ask if you can add some sound examples of your speakers,so as to understand better..Theodore.

[@johnjohnson7128]

linear power had 10s and 12s with amp for car audio years back

[@ericperry72]

Kenwood did also.

[@scottroberts4551]

Great explanation - thank you.

[@yadah678]

Excellent insightful videos! Make more thank you.

[@Newrecordday2013]

Danny has his own channel now, you can follow him here: KZbin.com/grresearch

[@chuckwilliams999]

Thanks Danny for the good video.

[@IliyaOsnovikov]

Do we have to use bass drivers with a direct servo? How about low Qts (below 0.25) pro bass drivers with powerfull motors used with necessary frequency response corrections?

[@Qui-9]

I think this is what servo control emulates, is a stronger motor. Honestly a high quality cone, regardless of mass, can be as fast/accurate as you need. This guy is talking like the envelope response is dependent on mass, and that's not directly true. Resonance and rolloffs etc in the frequency response will "smear" the envelope response. A woofer which rolls off high frequencies, but is combined with other drivers filling in the missing frequency response, will sound quick and accurate.

[@IliyaOsnovikov]

@@Qui-9 If we are talking about lower bass, I think, any pro bass driver with a really strong motor would be more accurate in an open baffle application particularly in a driver resonance range. Maybe not as accurate as a direct servo driver but pretty close to that.

[@SheikhN-bible-syndrome]

I've got a sub with a BL of 36 and its magnet is 5" tall by 10" wide it is very powerful and it will shock you at how it can play kick drum I love the feeling of 140+db helicopter bass beating on your chest. I've always noticed that the more BL a sub has the more "fast bass" it will have.

[@markfischer3626]

Thank you for clarifying this issue. Nobody ever explained it to me and I assumed that it meant the group delay between the application of voltage to the voice coil and the corresponding motion of the cone. This notion came from the 1970s silver bullet of "time alignment" where the drivers were supposed to respond together at the same time in the crossover range. This was supposed to make them "phase coherent." It doesn't unless the geometric center of propagation is the same such as in a coaxial or triaxial driver. It's like having two rocks land in a still pond at the same time but in different locations, they'll still create interference patterns. It took me 25 years between the time I had the analytical tools and the time I applied them to understand how woofer/enclosure systems actually work. The primary tool is Newton's second law of motion applied to forced oscillation. This is the same equation you'd use for many things such as how a car with springs and shock absorbers will respond to hitting a bump or pot hole. It's called the mass spring dashpot problem. The issue here is damping factor. What I realized was that in an acoustic suspension design the damping factor is controlled by the stuffing in the enclosure. The woofer is forced to push and pull air between the fibers. With the box containing a lot of stuffing the aggregate surface area of the fibers is enormous and the air space between them is tiny. It's the same principle as how the space shuttle heats up due to friction with air when it reenters the atmosphere at high velocity. The springiness of the air is linearly proportional to the amount of air compression and rarefaction in the enclosure. From the ideal gas laws PV=nRT --> P1xV1=P2xV2 where P=pressure and V=volume. Since Force = pressure x area the force is linear with both frequency and amplitude and it is applied uniformly over the surface of the cone with no differences either radially or circumferentially. A paper cone reduces internal energy dissipating it quickly between cellulose fibers. By adjusting mass, springiness, and damping you can have an acoustic suspension speaker have any resonant frequency and any Q you want it to. The price is efficiency. No other design IMO comes close to meeting this criteria. You might just as well speak about the speed of tweeters by their ability to dissipate energy, paper being the best, silk being very good, and metal being the worst.

[@maker-matt]

So, for an amplifier we call it damping factor. For a speaker it's a matter of physics - IE inertia. As was stated, the stored energy or "momentum" of the moving mass of the speaker cone and voice coil which causes the oscillation once the driven signal is removed. (which BTW does induce a voltage to the voice coil that the amplifier can damp out without the aid of additional feedback). The speakers (better defined as an "Audio Transducer") described as "Servo" are in reality a type of "Linear actuator" and very similar to a stepper motor in function. What is not (thoroughly) discussed is the special amplifier required to accept and process the feedback from the speaker, specifically the cost. That said, I think i will stick with my open baffle - hybrid bi-amped towers and tube amps!

[@bc527c]

The cost is readily known on his website. The open baffle subwoofer kits are not giant money. I have heard them in action, in an epic system at an audio show. Because you, like me, already have an open baffle woofer/subwoofer I can say this. Best bass I've ever heard. Ever, any system, any price. And they are not expensive.

[@yxcvmk]

Servo control means, a special amplifier (with fed-back input from the speaker) is needed?

[@billmilosz]

Yes, special amplifier and a special driver that has a sensor on it to "read" cone motion. So the subwoofer driver will have four terminals on it: audio drive power + and - , and sensing coil + and - terminals (or accelerometer sensor + and - for Velodyne etc)

[@ericfshook]

Good to know, this is what I hoped I meant when I say fast bass.

[@soundssimple1]

Just found this, great explanation of the theory and results found. It does seem to make sense. Does this then mean that Bose had it right all along with the Bose 901 cabinets ? ie lots of smaller drivers reacting quicker to push the air ? Please give me your comments ts on this ???

[@brians.4488]

The car boxes that Dino at stero plus in Las Vegas designed were fast as the woofers barley moved and sounded amd blended well with the mb quart mids.

[@netmoe]

In a non-servo controlled woofer application, isn't a high damping factor rating in the amplifier going to help solve this issue and have much better control of the woofer?

[@ryeshyes2552]

This is excellent and no-nonsense. Motional Feedback loudspeakers by Philips all the way back in the 70's....

[@Nomad-Rogers]

I call it thump vs. BOOM bass. Thump bass dose not step on the next bass note/ bass beat! BOOM BASS is how you get pulled over. And you are completely right it nothing but stopping the mass of the woofer /sub-woofer to the correct location in the basket. Very important for a fretless bass guitar performance in fact servo controlled speakers would be great for bass guitar Amplifier cabinets.

[@gges1605]

When two bass notes are played in quick succession a slower bass you will only hear one note however a fast bass you will hear both notes

[@dmc2554]

Keep goin' like yer goin'.....Did I learn something? Yes. Then I subscribed ...........

[@markfreedman2470]

Are you talking about the term “Transient Response” or perhaps “impulse Response”?

[@AntsAasma]

For linear systems impulse response encodes everything the system can do, including the storage, decay and release of energy. So technically, this is talking about one aspect of impulse response.

[@Davethreshold]

Partly right. It is not only moving mass but all drivers hit the dreaded BREAKUP mode, where they cease to become a piston. When that happens the response has a peak, followed by a very quick decline in the response. The larger the driver, the sooner the breakup mode. - Also, another way to look at it is, "fast bass" is really a matter of overhang. It is a law of physics that sealed enclosures will have less boom then vented enclosures. IOW they STOP quicker. That shows up in what is called the Group Delay which is expressed in milliseconds.

[@Davethreshold]

@Carl Klinkenborg That is so much BLAM that you don't need transient response! :-)

[@rimcountryoutfitters]

As a former God who has literally walked on the Moon, I must say this is some decent information.

[@sydneydalpe7818]

How would an infinite baffle twin voice coil compare to a T-line sub box design? How different would they sound?

[@michellonergan8517]

You are good and UNBIASED , thank you.

[@damianjacobs2193]

why has servo technology been so unpopular? Does it complicate the dsp schemes of today? I was stunned to find the JL fathom subs were not servo...before we used the room eq/mic setup to tune the JL's the fathom had the "one note" bass effect going on at about 50hz ( a subtle but constant resonance )...I could'nt help but think that a servo mechanism would have eliminated this entirely....perhaps at the cost of clean volume? The DSP corrected the frequency response but the resonance was still there....this was in a treated room with serious bass traps...they were loud AF though and I guess fast enough paired with Focal Alto Utopias

[@mattlehnardt8035]

The multiple low mass drivers is the idea behind TEKTON audio designs for upper midrange. Apparently it works pretty well but they claim a patent on line arrays, when it’s been around for 70 years as common knowledge.

[@caseyodonnell6621]

If you can pretty much make the frequency response look any way you want it to then why not put servo control on mids and tweets as well? I understand that there’s less mass moving so you’re not as concerned with the cone smearing the sound but wouldn’t servo controls all around just make a hyper accurate and super tunable speaker system? Love these vids. Thanks!

[@dannyrichie9743]

We tried it on 5" drivers playing up to 2kHz. From 200Hz and down the servo amp was clearly better in every way than our non-servo controlled amps. But above 200Hz the advantage went away and the quality of the amp (sound quality) made a much greater difference in how it sounded.

[@shomesaha]

Hello Sir, between the two designs , small multidriver vs large servo controlled sub , which one would be a preferred interms of acoustic properties ( texture, slam, depth etc) ..If any, in which applications one design may be preferred over the other?

[@dannyrichie9743]

For high SPL levels the LS-9's with big powerful tube amps on them were a personal favorite: gr-research.com/mis/ls9-1.jpg

[@dannyrichie9743]

Realistically though what is ideal for one room might not be so for another. It all depends on the limitations of the room.

[@shomesaha]

Thanks for the response.In a room say 24 ft by 14ft which one would work ...Also considering servo controlled Bigger drivers can be tuned to calibrate with the room , why isnt the preferred solution....

[@dannyrichie9743]

@@shomesaha Here is a personal favorite that is a combination of multiple drivers in the bass, open baffle top to bottom, and servo controlled woofers handling the very bottom: gr-research.com/nx-treme.aspx

[@stogie525]

We need a video showing how good these sound please.

[@pssound9749]

How on earth would you show it?? :D

[@59seank]

Danny, thanks for a great explanation of "fast" bass. We need a better name for it. I've heard the term "tight bass" before, and that might refer to the lack of smearing you can get with larger woofers. Do you sell open baffle subwoofers as a completed product or are they only sold as kits?

[@dannyrichie9743]

I try not to spend my time doing assembly work. But I do have customers that regularly build out these things for other customers, and at a real reasonable price.

[@59seank]

@@dannyrichie9743 Thanks for the quick reply. I'll look around for someone in the Chicago area that might be able to build one for me.

[@dannyrichie9743]

@@59seank Post something about it in our forum at the Audio Circle and you will likely get some responses and some help from customers in that area.

[@59seank]

@@dannyrichie9743 Thanks, Danny.

[@djohnnineonesix820]

My YST-C10 Yamaha component sounds amazing.

[@TheSimonarne]

i would ratehr use the therm signal responsiveness. adding decay would reduce responisveness

[@cihant5438]

This guys knows what he is talking about

[@Jasonv8z]

It's not so much the mass of the woofer but the Q of the system which is a measure of how damped the speaker is around its resonance. Tune your sub with a Q of 0.5 and it will be critically damped (fast decay). The majority of subs are underdamped to get more low frequency bass at the expense of quality.