servo subwoofers
Hi Paradise Ice,
Interestingly, many years ago I had a discussion with a friend of mine, an electronic engineer who used to run his own audio design and manufacturing business, about using an aditional coil to control the movement of the sub's cone. He said that ideally, it should be a small coil with a few turns (the number experimentally determined) made of a thin wire and possibly somehow screened to minimise the influence of the main coil. I tried to persuade him that we might explore this direction (I am an economist by profession with interest in audio electronics althugh I also studied engineering including two semesters of electronics) but by then a frien of mine was already loosing his interest in audio electronics so I did not rise the issue again.
It seems that the guy from the rythmik audio did exactly that and patented the whole thing. Looks that people in different parts of the world may come to the same conclusions.
Anyway, I think these subs are made in China (or elswere in Asia) so the price can be low. Besides it is a new concept (and possibly a young business) so it needs to attract customers by offering low prices. Over time these will go up. Still, the overall efficiency of their systems is moderate and obviously one needs bigger (15")and more efficient drivers but the concept is extremely promissing.
Cheers,
Hi Paradise Ice,
Interestingly, many years ago I had a discussion with a friend of mine, an electronic engineer who used to run his own audio design and manufacturing business, about using an aditional coil to control the movement of the sub's cone. He said that ideally, it should be a small coil with a few turns (the number experimentally determined) made of a thin wire and possibly somehow screened to minimise the influence of the main coil. I tried to persuade him that we might explore this direction (I am an economist by profession with interest in audio electronics althugh I also studied engineering including two semesters of electronics) but by then a frien of mine was already loosing his interest in audio electronics so I did not rise the issue again.
It seems that the guy from the rythmik audio did exactly that and patented the whole thing. Looks that people in different parts of the world may come to the same conclusions.
Anyway, I think these subs are made in China (or elswere in Asia) so the price can be low. Besides it is a new concept (and possibly a young business) so it needs to attract customers by offering low prices. Over time these will go up. Still, the overall efficiency of their systems is moderate and obviously one needs bigger (15")and more efficient drivers but the concept is extremely promissing.
Cheers,
Janusz
Curious? – on what evidence do you think that Rythmik Audio did:
Small coil with a few turns (experimentally determined) made of a thin wire and possibly somehow screened to minimise the influence of the main coil.
And what would the benefit(s) be?
Cheers
Curious? – on what evidence do you think that Rythmik Audio did:
Small coil with a few turns (experimentally determined) made of a thin wire and possibly somehow screened to minimise the influence of the main coil.
And what would the benefit(s) be?
Cheers
Oh, I agree with you! Fast bass - at least as many audiohphile classify it - is actually a lack of bass. We've done work for many high end companies... It's nearly a 100% predictable occurance that they will ask for "flat to 20, -3 dB at 16 Hz) for their high end product. So they get that kind of response. And it's immediately classified as slow and boomy. Rolling off the bottom end around 35 Hz or so "tightens" and "speeds" up the perceived bass. Of course, it's really just cutting the deep stuff out...
Objectively, physics says deep extension is fast. Of course perception is really what we need to concern ourselves with, and that is often to roll off the deep bass. Provide some of it there, but if the 20 Hz level is a good 10 dB down from the 35-40 Hz range, there's enough deep stuff to hint at its existence, without making the perception "slow".
I just love throwing in the actual physics of what fast bass physically IS - it's the lowest, loudest, flattest extension bass. In other words, in terms of the actual physics of the situation, a 6.5" woofer cutting off at 40 Hz is nowhere near as fast as a 12" woofer extending down to 16 Hz...🙂
Dan Wiggins
Adire Audio
Objectively, physics says deep extension is fast. Of course perception is really what we need to concern ourselves with, and that is often to roll off the deep bass. Provide some of it there, but if the 20 Hz level is a good 10 dB down from the 35-40 Hz range, there's enough deep stuff to hint at its existence, without making the perception "slow".
I just love throwing in the actual physics of what fast bass physically IS - it's the lowest, loudest, flattest extension bass. In other words, in terms of the actual physics of the situation, a 6.5" woofer cutting off at 40 Hz is nowhere near as fast as a 12" woofer extending down to 16 Hz...🙂
Dan Wiggins
Adire Audio
DanWiggins said:
Lack of bass Dan? I have never heard an audiophile system to be lacking in bass extension or volume or even said to be slow when these qualities are present?
Almost all high end systems, be they home or studio factor in an accurate extended low end frequency response, below 35Hz don’t they?
I believe to have an accurate low end extension below 50Hz to 10Hz that is not classed as slow, specific drivers have to be used.
In a typical three way systems you have your bass, 35Hz to 500Hz flat, 500Hz to 3.5Khz flat and then 3.5Khz to infinity and beyond 🙂 all flat, yes there is a roll of at 35Hz, as the excursion is so large a typical driver with 20mm running from 35 Hz to 200Hz has nothing left below 35Hz It would be very difficult to muster the required excursion with standard suspension and motors.
The sub infra range will not be perceived as slow, when it's separated,
It adds scale, space and air to music IMHO.
Its cheaper to use 3 driver units and be aesthetically pleasing and present a simple load to an amplifier than to increase the cost and complexity of a speaker system with another pair of drive units with a very limited range, and seemingly limited purpose, but I don’t believe this 2D thinking.
The servo-feedback systems of the passed that I am aware of used capacitive sensing. They had a small piece of foil on the inside of the dust cap, and the other plate located around the top of the pole piece, and measured the cone motion from that, and from that signal, derived the needed corrective voltage to apply to the voice coil.
Re: servo subwoofers
There are many variations of servo subwoofers based on sensing coils. Some are proposed before we filed the patent (in 1995) and some are after. I have a survey of that on my web page. Second, there is no so-called optimal number of turns in the sensing coil. If there is, then it is not the same as ours, and I cannot do anything legally🙂. I have developed an entire set of servo theory (to explain how all servo subs are equivalent or not equivalent to each other), even before 1995 (BTW, I do have a Ph.D degree in Engineering). My next project: dual sensing feedbacks in passive radiator servo.
Maybe I didn't make this clear on my web page. The subwoofers are made in US . Sorry I have to stop that misquote.
Brian Ding
Rythmik Audio
janusz said:
There are many variations of servo subwoofers based on sensing coils. Some are proposed before we filed the patent (in 1995) and some are after. I have a survey of that on my web page. Second, there is no so-called optimal number of turns in the sensing coil. If there is, then it is not the same as ours, and I cannot do anything legally🙂. I have developed an entire set of servo theory (to explain how all servo subs are equivalent or not equivalent to each other), even before 1995 (BTW, I do have a Ph.D degree in Engineering). My next project: dual sensing feedbacks in passive radiator servo.
Maybe I didn't make this clear on my web page. The subwoofers are made in US . Sorry I have to stop that misquote.
Brian Ding
Rythmik Audio
directservo:
Since your website is for the buying pubic, don't you think you should get in there and polish up the misspellings and grammar?
Since your website is for the buying pubic, don't you think you should get in there and polish up the misspellings and grammar?
Fast subwoofer (how fast???)
How fast can a subwoofer sound? No matter how fast they sound, they cannot be faster than the speed of sound regardless it is at 20hz, or 100hz, or 200hz🙂
There are subwoofers that can only sound "fast" when the bass frequency is aggressively attenuated. This is not because 100hz will sound faster than 20hz, it is because the deficiency of those particular subwoofers at low frequency. There are also subwoofers no matter which frequency it plays, they consistently sound slower than other subwoofers. All of these are because the memory effect in materials used in the subs, plus other factors such as distortion, and enclosure, etc. Some are better than the others. That is why some subs sound like they are always "slightly" behind in term of rhythm.
Brian Ding
Rythmik Audio
How fast can a subwoofer sound? No matter how fast they sound, they cannot be faster than the speed of sound regardless it is at 20hz, or 100hz, or 200hz🙂
There are subwoofers that can only sound "fast" when the bass frequency is aggressively attenuated. This is not because 100hz will sound faster than 20hz, it is because the deficiency of those particular subwoofers at low frequency. There are also subwoofers no matter which frequency it plays, they consistently sound slower than other subwoofers. All of these are because the memory effect in materials used in the subs, plus other factors such as distortion, and enclosure, etc. Some are better than the others. That is why some subs sound like they are always "slightly" behind in term of rhythm.
Brian Ding
Rythmik Audio
Bill Fitzpatrick said:
Can I contract you to do that? I am serious. I need someone to read proof the web pages.
Brian Ding
Rythmik Audio
Bill Fitzpatrick said:
Can I contract you to do that? I am serious. I need someone to read proof the web pages.
Brian Ding
Rythmik Audio
Re: Fast subwoofer (how fast???)
I think not enough is done to determine the ability of a big driver to follow the waveform as presented. Tracking a sine wave is easy enough but the transients that create tonal quality require slew rates that only big amps can deliver. Inertia must be overcome and even if a driver can follow, there is always going to be a lag between the signal and the driver motion. This delay is the difference between when the low tones and their harmonics reach my ears. Even more than delay, it is an out of phase response that gets clipped when the signal reverses direction.
Ergo, the LF driver is "slow" if it cannot keep up with the mid or HF transducer.
🙂ensen.
PS: Interesting that the definition of fast has so far not included "motionless," as in "hold fast."
I think not enough is done to determine the ability of a big driver to follow the waveform as presented. Tracking a sine wave is easy enough but the transients that create tonal quality require slew rates that only big amps can deliver. Inertia must be overcome and even if a driver can follow, there is always going to be a lag between the signal and the driver motion. This delay is the difference between when the low tones and their harmonics reach my ears. Even more than delay, it is an out of phase response that gets clipped when the signal reverses direction.
Ergo, the LF driver is "slow" if it cannot keep up with the mid or HF transducer.
🙂ensen.
PS: Interesting that the definition of fast has so far not included "motionless," as in "hold fast."
DanWiggins said:
Sounds like they want to compensate for room gain, which tends to be a 6dB/octave phenomenon, no? Wilsons use a low-Q alignment and get kudos for their tight bass, probably for the same reason.
Francois.
Re: Re: Fast subwoofer (how fast???)
Not enough is done because we still don't know if the relation between larger cone and higher cone mass and slower bass is a causation or correlation. I think it is a little bit of everything that can be traced back to higher cone mass. And higher cone mass by itself does not make the bass sound slow. I have heard 15" drivers that sound more defined than smaller drivers (I don't want to use the term fast because it is really about definition).
Earlier European driver makers offered two drivers based on similar motors (that is the magnetic size is same and top plate and back plate thickness is the same..) and same cone material, one for midbass and one for bass. The cone mass on the midbass driver is always lighter. So when people compare the sound, the conclusion is lighter mass in the midbass caused it to sound "faster". However, other factors that were not discussed at that time was the distortion number and how well the cone can be controlled. Both of these are partially related to the force factor and inductance. The force factor in the midbass driver is higher (because the gap is tighter and voice coil is shorter) and the inductance is lower (for the same reason). These factors affect distortion because a higher force factor draws less current and induces less magnetic distortion. In terms of cone control, if there were no voice coil resistance and inductance, the cone motion can be completely controlled (except the natural resonance of the cone). In practice, the term (BL)^2/Re is often used as the indicator of how well the cone can be controlled. I think this metric should be corrected as (BL)^2/(Re*Ms). Then one can see higher mass just needs higher BL value to support it. And for the case of previous midbass driver vs bass driver example, the midbass driver has both higher BL value and lower mass. No wonder they sound better.
In our servo subwoofers, the system acts as if the voice coil has a resistance of only 1 ohm. That is a factor of 3x improvement compared to the same driver used in a non-servo configuration.
BTW, there is no significant signal information from musical instruments below 30hz (actually, a lot of people say it's 40hz). So the bass definition will remain the same whether the sub has a 20hz extension or 30hz extension. Changing the extension from 30hz to 20hz increases the perception of hall effect (which is primarily very low frequency contents). The bass definition remains the same. So if someone gets faster bass by moving the bass extension from 20hz to 30hz, he is doing something else that indirectly improves the sound characteristic about 40hz. So it is a correlation, but not causation.
Conclusion, there wouldn't be a single reason to explain what makes fast bass. There are always counter-examples. The problem is so complex that I thought we aleady gave up trying 🙂
Brian Ding
Rythmik Audio
purplepeople said:
Not enough is done because we still don't know if the relation between larger cone and higher cone mass and slower bass is a causation or correlation. I think it is a little bit of everything that can be traced back to higher cone mass. And higher cone mass by itself does not make the bass sound slow. I have heard 15" drivers that sound more defined than smaller drivers (I don't want to use the term fast because it is really about definition).
Earlier European driver makers offered two drivers based on similar motors (that is the magnetic size is same and top plate and back plate thickness is the same..) and same cone material, one for midbass and one for bass. The cone mass on the midbass driver is always lighter. So when people compare the sound, the conclusion is lighter mass in the midbass caused it to sound "faster". However, other factors that were not discussed at that time was the distortion number and how well the cone can be controlled. Both of these are partially related to the force factor and inductance. The force factor in the midbass driver is higher (because the gap is tighter and voice coil is shorter) and the inductance is lower (for the same reason). These factors affect distortion because a higher force factor draws less current and induces less magnetic distortion. In terms of cone control, if there were no voice coil resistance and inductance, the cone motion can be completely controlled (except the natural resonance of the cone). In practice, the term (BL)^2/Re is often used as the indicator of how well the cone can be controlled. I think this metric should be corrected as (BL)^2/(Re*Ms). Then one can see higher mass just needs higher BL value to support it. And for the case of previous midbass driver vs bass driver example, the midbass driver has both higher BL value and lower mass. No wonder they sound better.
In our servo subwoofers, the system acts as if the voice coil has a resistance of only 1 ohm. That is a factor of 3x improvement compared to the same driver used in a non-servo configuration.
BTW, there is no significant signal information from musical instruments below 30hz (actually, a lot of people say it's 40hz). So the bass definition will remain the same whether the sub has a 20hz extension or 30hz extension. Changing the extension from 30hz to 20hz increases the perception of hall effect (which is primarily very low frequency contents). The bass definition remains the same. So if someone gets faster bass by moving the bass extension from 20hz to 30hz, he is doing something else that indirectly improves the sound characteristic about 40hz. So it is a correlation, but not causation.
Conclusion, there wouldn't be a single reason to explain what makes fast bass. There are always counter-examples. The problem is so complex that I thought we aleady gave up trying 🙂
Brian Ding
Rythmik Audio
Re: Re: Re: Fast subwoofer (how fast???)
Brian when you say, there is no significant musical information below 30Hz, you must be talking about a natural string instruments or the musical recording?
Modern music and formats are filled with a vast amount of programming below 30Hz
With the advent of SACD DVD and there new respected formats, signals below 30Hz are typical and omni present in real musical events and life.
A vital quality in my ears for Vinyl is the low frequency output and feedback, below 30Hz.
This is strange we are talking about fast bass and yet, we have not discussed what sounds fast in the first place?
In order to have a fast sound, a fast sound must be defined, what’s fast then?
What does sounds fast? I will not concern myself with musical tempo, lets simple concern ourselves with the perception and quality of a sound that is fast, we all have set ideas on what’s fast but,
When it comes to music, unless we are part of the band or the recording engineering staff we will never know what was played before it was digitised and mixed to become our favourite music, so what is fast must be from our imagination or what we want to hear, so can we make a sound that equals the leading edge of our imagination?
The sound we hear is a perception, Our ears are chemical mechanical microphones and from morning to night there perception shifts with our biological rhythms, so in a sense, we are not accurate or linear machines for testing what is fast and what is not.
The drug culture in the UK past and present proves that strong chemicals make people feel that time slows down and sounds are more meaningful and have much more sensation and wonder than without these chemical enhancements.
Could a healthy person hear a fast bass when an unhealthy one hears a slow bass? Is this a simplistic notion that our healthy and emotional state of being has a greater affect on the sound we hear?
This would go some way to explain the lack of emotional human agreement with technical and mathematical data that has been amassed over many years from many people, yet we still do not have a formula for (dare I say it) fast bass.
Is fast bass metaphysical or real? Is it something that can be made with the correct collection of electronics and transducers?
Yes and No, Maybe and Maybe, No and Yes,
Who knows and who cares😎
Take your pick, the questions is far more complex than the answer, to which each person has there own notion.
directservo said:
Brian when you say, there is no significant musical information below 30Hz, you must be talking about a natural string instruments or the musical recording?
Modern music and formats are filled with a vast amount of programming below 30Hz
With the advent of SACD DVD and there new respected formats, signals below 30Hz are typical and omni present in real musical events and life.
A vital quality in my ears for Vinyl is the low frequency output and feedback, below 30Hz.
This is strange we are talking about fast bass and yet, we have not discussed what sounds fast in the first place?
In order to have a fast sound, a fast sound must be defined, what’s fast then?
What does sounds fast? I will not concern myself with musical tempo, lets simple concern ourselves with the perception and quality of a sound that is fast, we all have set ideas on what’s fast but,
When it comes to music, unless we are part of the band or the recording engineering staff we will never know what was played before it was digitised and mixed to become our favourite music, so what is fast must be from our imagination or what we want to hear, so can we make a sound that equals the leading edge of our imagination?
The sound we hear is a perception, Our ears are chemical mechanical microphones and from morning to night there perception shifts with our biological rhythms, so in a sense, we are not accurate or linear machines for testing what is fast and what is not.
The drug culture in the UK past and present proves that strong chemicals make people feel that time slows down and sounds are more meaningful and have much more sensation and wonder than without these chemical enhancements.
Could a healthy person hear a fast bass when an unhealthy one hears a slow bass? Is this a simplistic notion that our healthy and emotional state of being has a greater affect on the sound we hear?
This would go some way to explain the lack of emotional human agreement with technical and mathematical data that has been amassed over many years from many people, yet we still do not have a formula for (dare I say it) fast bass.
Is fast bass metaphysical or real? Is it something that can be made with the correct collection of electronics and transducers?
Yes and No, Maybe and Maybe, No and Yes,
Who knows and who cares😎
Take your pick, the questions is far more complex than the answer, to which each person has there own notion.
Great post there Troy. Too often people talk about 'no information below 30 Hz' but they neglect modern synthetic music. I have been in clubs where several times I thought my phone was vibrating in my pocket, but it was just the bass 🙂 Bass so deep that when you speak your voice is modulated 🙂
I also back you up on the emotional state thing. Depending on how you feel (which probably is influenced a little by your health as well) can change the way your system sounds. Me and friends have had experience of this.
PS Hope to report on the subs sometime late Jan when I get my new amps and digital camera 🙂 Good to see you again.
I also back you up on the emotional state thing. Depending on how you feel (which probably is influenced a little by your health as well) can change the way your system sounds. Me and friends have had experience of this.
PS Hope to report on the subs sometime late Jan when I get my new amps and digital camera 🙂 Good to see you again.
Sorry to disillusion you richie, but that bass you love in clubs is probably all around 40-60 Hz, pro systems are way too expensive to run flat below that...😉
I know pro/club systems have a relatively high F3, but because the levels are so loud, even at 20Hz there is still significant output.
pinkmouse said:
Yes your right they don’t run flat below 40Hz but I don’t think they could, if flat was 120+db @ 20Hz in a hall of some 130 feet by 80 feet, for this you would need a hurricane maybe 😉
Hi Richie I have been working away, hope your well.
Pinkmouse, I understand what Richie is saying, the output is still very high below 40Hz and this is true deep bass, maybe not flat but it could still be 103 to 115db at these true low frequencies, plus the music makes a vast difference in what is felt.
The output of every club system is very different, some have bass bins, some just have lots of small excursion high SPL PA drivers, but others have well designed walls for low frequency extension, club owners want an edge to get customers, they are investing in well though out high output bass walls and under floor systems, the 80 pop club wont cut the mustard with modern electronica
,
AudioFreak said:
You are probably standing in line with a beaming array of drive units and yes I agree it is far too loud but it’s the only way to get the music into every nook and cranny in the club, my advice get off axis and turn your back to drivers 🙂
You know most UK DJ's have some hearing loss😱
I didn’t know this until recently poor sods, dont want that job.
Paradise_Ice said:
Sure, but most Club systems have all the low bass rolled off to prevent the drivers from being constantly burned out. It may not be obvious, but all big systems will have a control rack hidden away where the DJ's can't get their paws on it. 🙂
As for the wall and floor bass systems, they are purely shakers, similar to those used in theme park rides. Actual output at audio frequencies is minimal. It's all psychological 😉
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