To Sub Or Not To Sub, That Is The Question

[DonH50]

Subwoofers are resonant devices that depend entirely on high moving mass and creating efficiency via of resonance! Common sense dictates that any form of resonance is not controlled by the input signal! Please read about the solution to resonance, physical size, integration and room issues.

www.tbisubwoofers.com

I have never thought about subwoofers as resonant devices aside from port and box tuning. A resonant circuit is a significantly different thing to me. High moving mass does not necessarily lead to high efficiency; it is more dependent upon the volume of the box and any porting (there is resonance at the port, and a sealed box has a resonance point in conjunction with the driver parameters, but the vast majority of operation is not at the resonance frequency).

Bass extension and overall efficiency is a combination of driver and box parameters. And generally the problem with distortion occurs at higher levels, not the lowest signal, which requires less movement and thus reduces distortion. Drivers do not have crossover distortion so touted in amplifiers as causing problems at low audio levels (though that is largely a myth, not a subwoofer topic).

There are physical rules like Hoffman's Law limiting the efficiency one can obtain from a small driver such as you propose. And Helmholtz, T/S, and other formulas for designing speakers. Do you have any white papers or technical articles describing your approach?

 

[Robh3606]

Subwoofers are resonant devices that depend entirely on high moving mass and creating efficiency via of resonance! Common sense dictates that any form of resonance is not controlled by the input signal! Please read about the solution to resonance, physical size, integration and room issues.

www.tbisubwoofers.com

Huh? So are musical instruments. How do you think you tune them?

Rob

 

[Macattack]

Okay, so bass resonants in a room. Not sure how you overcome the physics to say your 20HZ or whatever frequency Sub output resonates less In a room than another sub.

The room is the room.

If you are saying your subs enclosure resonates less than others, okay, prove it. Show us the data.

 

[Holmz]

I have never thought about subwoofers as resonant devices aside from port and box tuning. A resonant circuit is a significantly different thing to me. High moving mass does not necessarily lead to high efficiency; it is more dependent upon the volume of the box and any porting (there is resonance at the port, and a sealed box has a resonance point in conjunction with the driver parameters, but the vast majority of operation is not at the resonance frequency).

Bass extension and overall efficiency is a combination of driver and box parameters. And generally the problem with distortion occurs at higher levels, not the lowest signal, which requires less movement and thus reduces distortion. Drivers do not have crossover distortion so touted in amplifiers as causing problems at low audio levels (though that is largely a myth, not a subwoofer topic).

There are physical rules like Hoffman's Law limiting the efficiency one can obtain from a small driver such as you propose. And Helmholtz, T/S, and other formulas for designing speakers. Do you have any white papers or technical articles describing your approach?

it is possible that the higher moving mass that the fellow was talking about was either air in a port, or it was a passive radiator with mass on the diaphragm… (that is my guess).

 

[DonH50]

it is possible that the higher moving mass that the fellow was talking about was either air in a port, or it was a passive radiator with mass on the diaphragm… (that is my guess).

Did not read like it to me, and the design is using 6.5" drivers so apparently lower mass, but all I've seen so far is marketing without any real description of the innovation (technical details) so can't say. Some of the claims appear to defy physics but again without detail it is impossible to review the claims and design. They may not want to release details pending a patent, or ever if they do not plan to patent it.

A passive radiator would still appear to be a "resonator" in their eyes based upon the original post. Maybe a worse resonator since it is not driven.

 

[Musical Bass]

I tried to read and understand what's on this website, but I am afraid I don't understand what this subwoofer is doing differently. Are you an owner of the sub or a representative of the company?

Well first it’s small using a driver with a tenth the mass of a typical subwoofer! The range is 20-200 analog. It is acoustically grounded! The difference is for music where fundamentals need speed, mass and the associated resonance is not musical! The issues that I witness on the site are fairly consistent meaning a common problem! Room reflections in small rooms affect subwoofers only because they are operating in a state of resonance! That is what brings the efficiency same thing that brought the Tacoma Narrows bridge down. The MS-6P avoids the principle of resonance and produces broadband critically damped output that loves the room! The room is actually a pressure vessel with room gain at low frequencies if resonances don’t get in the way!
Owner and representative!

 

[Musical Bass]

I have never thought about subwoofers as resonant devices aside from port and box tuning. A resonant circuit is a significantly different thing to me. High moving mass does not necessarily lead to high efficiency; it is more dependent upon the volume of the box and any porting (there is resonance at the port, and a sealed box has a resonance point in conjunction with the driver parameters, but the vast majority of operation is not at the resonance frequency).

Bass extension and overall efficiency is a combination of driver and box parameters. And generally the problem with distortion occurs at higher levels, not the lowest signal, which requires less movement and thus reduces distortion. Drivers do not have crossover distortion so touted in amplifiers as causing problems at low audio levels (though that is largely a myth, not a subwoofer topic).

There are physical rules like Hoffman's Law limiting the efficiency one can obtain from a small driver such as you propose. And Helmholtz, T/S, and other formulas for designing speakers. Do you have any white papers or technical articles describing your approach?

Did you see the graphs? These are low level inputs right from the lowest frequency to the highest. There is no eq or crossover associated with the graph for the passive unit! The driver has a moving mass of 32 grams with a Fa of 40Hz. If you look at the 20Hz sine wave at low level it is a clean sine wave! It is a quick 20Hz not created by moving mass! Of course distortion increases with level but we are not compressing air in this patented alignment so Hoffmans iron law is not in play here! The exterior dimensions of the enclosure 3D printed unit is 10” x 10” x 7 “. The driver diameter is 6.5”. The reason that it am posting this info is for everyone’s information.

We will scale the design for most subwoofer diameters in the future using 75% less cabinet volume with efficient non resonant high level output favorable for room operation. For reference just how many independent sound sources ( no speakers) have a problem with small room acoustics?

 

[DonH50]

Room modes are dictated by room dimensions, does not matter the speaker (or subwoofer). The idea of equating room and speaker resonances to the Tacoma Narrows bridge failure, a result of underdamped resonance excited by wind, is not particularly relevant. Speakers are driven by amplifiers that control their motion, speakers (drivers) have suspensions (spider and surround) that reduce resonances, and room modes ("resonances") are independent of the speaker.

"Speed" just means enough bandwidth to reproduce the frequency range of interest, which is pretty low for a subwoofer. System damping via driver, box, and amplifier designs help control transient response, another interpretation of "speed", but again for a subwoofer not a lot of bandwidth is needed for that. Any driver has mass, and high or low it is up to the amplifier driving it to control the mass and "resonance". I think there must be a bit of a language barrier here, or a technical disconnect.

 

[Musical Bass]

Room modes are dictated by room dimensions, does not matter the speaker (or subwoofer). The idea of equating room and speaker resonances to the Tacoma Narrows bridge failure, a result of underdamped resonance excited by wind, is not particularly relevant. Speakers are driven by amplifiers that control their motion, speakers (drivers) have suspensions (spider and surround) that reduce resonances, and room modes ("resonances") are independent of the speaker.

"Speed" just means enough bandwidth to reproduce the frequency range of interest, which is pretty low for a subwoofer. System damping via driver, box, and amplifier designs help control transient response, another interpretation of "speed", but again for a subwoofer not a lot of bandwidth is needed for that. Any driver has mass, and high or low it is up to the amplifier driving it control the mass and "resonance". I think there must be a bit of a language barrier here, or a technical disconnect.

I appreciate your explanations but the fact is that there are common issues (problems)associated with the existing theory!

You are 100% correct if innovation isn’t introduced! Please don’t believe that all of the physics has been employed in this subject! Entropy, isothermal dissipation, 2-Dimensional turbulence and 3-Dimensional turbulence are a few new terms to be introduced !

 

[sigbergaudio]

Well first it’s small using a driver with a tenth the mass of a typical subwoofer! The range is 20-200 analog. It is acoustically grounded! The difference is for music where fundamentals need speed, mass and the associated resonance is not musical! The issues that I witness on the site are fairly consistent meaning a common problem! Room reflections in small rooms affect subwoofers only because they are operating in a state of resonance! That is what brings the efficiency same thing that brought the Tacoma Narrows bridge down. The MS-6P avoids the principle of resonance and produces broadband critically damped output that loves the room! The room is actually a pressure vessel with room gain at low frequencies if resonances don’t get in the way!
Owner and representative!

A small driver with a light cone and Fs of 40hz will not create a whole lot of sub bass. Based on your graph the sub seem to be about -12dB or something at 20hz, which in itself isn't bad given the size, but at what SPL I wonder. Your graph is also very low resolution. You have 10dB per line on the y-axis that is severely truncated by the scale - and also smoothed.

Instead of -150 to 150dB, try 45-105dB (so a 50dB range rather than 300dB range), and no smoothing. Something along the lines of this (1dB per line rather than 10dB):







This state of resonance you are talking about makes little sense to me. I see nothing about your design that would make the sub ignore the room. Do you perhaps have a measure of your subwoofer from the listening position (3-4 meters from the subwoofer) in a room, without equalization to prove this idea?

 

[Musical Bass]

Did you see the graphs? These are low level inputs right from the lowest frequency to the highest. There is no eq or crossover associated with the graph for the passive unit! The driver has a moving mass of 32 grams with a Fa of 40Hz. If you look at the 20Hz sine wave at low level it is a clean sine wave! It is a quick 20Hz not created by moving mass! Of course distortion increases with level but we are not compressing air in this patented alignment so Hoffmans iron law is not in play here! The exterior dimensions of the enclosure 3D printed unit is 10” x 10” x 7 “. The driver diameter is 6.5”. The reason that it am posting this info is for everyone’s information.

We will scale the design for most subwoofer diameters in the future using 75% less cabinet volume with efficient non resonant high level output favorable for room operation. For reference just how many independent sound sources ( no speakers) have a problem with small room acoustics?

High moving mass represents inefficiency and slow response in any form cars, speakers etc. resonating the mass increases the efficiency!

 

[Musical Bass]

A small driver with a light cone and Fs of 40hz will not create a whole lot of sub bass. Based on your graph the sub seem to be about -12dB or something at 20hz, which in itself isn't bad given the size, but at what SPL I wonder. Your graph is also very low resolution. You have 10dB per line on the y-axis that is severely truncated by the scale - and also smoothed.

Instead of -150 to 150dB, try 45-105dB (so a 50dB range rather than 300dB range), and no smoothing. Something along the lines of this (1dB per line rather than 10dB):

View attachment 134967





This state of resonance you are talking about makes little sense to me. I see nothing about your design that would make the sub ignore the room. Do you perhaps have a measure of your subwoofer from the listening position (3-4 meters from the subwoofer) in a room, without equalization to prove this idea?

In replying to the 20Hz level don’t forget about room gain at that frequency! Any sub flat to 20Hz would overload a typical room. The rolloff below 20Hz is not typical of a ported enclosure more like a sealed box! Again pay attention to mass! I would rather produce that 20Hz with low mass so it won’t hear a sub as is the current problem. Your mains will always have lower mass so response will be quicker than the sub! What you don’t see is what is going on inside that small amount of real estate! There is virtually no free air space inside! The drivers energy is acoustically grounded behind the diaphragm for all motions. It ignores room reflections as a result. We will expand the design for all driver diameters eliminating the large size currently required while improving quality!

I’ll get you out a pink noise of the room but hearing is the only quality measure. The room has modes but the solution is to keep the driver from being sensitive to them. When this is achieved there will be benign modes in different parts of the room but the subwoofer not enhancing those modes. More like an independent source of sound in the room like your voice. It can sound different listening in different locations but your voice close up is the same!

 

[Musical Bass]

In replying to the 20Hz level don’t forget about room gain at that frequency! Any sub flat to 20Hz would overload a typical room. The rolloff below 20Hz is not typical of a ported enclosure more like a sealed box! Again pay attention to mass! I would rather produce that 20Hz with low mass so it won’t hear a sub as is the current problem. Your mains will always have lower mass so response will be quicker than the sub! What you don’t see is what is going on inside that small amount of real estate! There is virtually no free air space inside! The drivers energy is acoustically grounded behind the diaphragm for all motions. It ignores room reflections as a result. We will expand the design for all driver diameters eliminating the large size currently required while improving quality!

I’ll get you out a pink noise of the room but hearing is the only quality measure. The room has modes but the solution is to keep the driver from being sensitive to them. When this is achieved there will be benign modes in different parts of the room but the subwoofer not enhancing those modes. More like an independent source of sound in the room like your voice. It can sound different listening in different locations but your voice close up is the same!

The late Siegfried Linkwitz of filter design has a page on his current website titled issues with speakers! He is well respected for his views and he states plainly that there needs to be a way to acoustically terminate the energy behind the driver to prevent it from interfering with the drivers motion. He resorted to the flat baffle (no enclosure) approach because no solution had been attained!

 

[sigbergaudio]

It ignores room reflections as a result.

I am afraid this reads as pure fantasy until you are able to back up those claims with some measurements and proof of some sort.

 

[Musical Bass]

A small driver with a light cone and Fs of 40hz will not create a whole lot of sub bass. Based on your graph the sub seem to be about -12dB or something at 20hz, which in itself isn't bad given the size, but at what SPL I wonder. Your graph is also very low resolution. You have 10dB per line on the y-axis that is severely truncated by the scale - and also smoothed.

Instead of -150 to 150dB, try 45-105dB (so a 50dB range rather than 300dB range), and no smoothing. Something along the lines of this (1dB per line rather than 10dB):

View attachment 134967





This state of resonance you are talking about makes little sense to me. I see nothing about your design that would make the sub ignore the room. Do you perhaps have a measure of your subwoofer from the listening position (3-4 meters from the subwoofer) in a room, without equalization to prove this idea?

The graph is not smoothed! You can see the breakup in the higher bass regions

 

[DonH50]

I appreciate your explanations but the fact is that there are common issues (problems)associated with the existing theory!

You are 100% correct if innovation isn’t introduced! Please don’t believe that all of the physics has been employed in this subject! Entropy, isothermal dissipation, 2-Dimensional turbulence and 3-Dimensional turbulence are a few new terms to be introduced !

I am familiar with all of those terms and eagerly await more detailed technical explanations. The only systems I am aware of to date that counter them are active, using servo (feedback) control for the driver, and essentially acoustic waveform processing (akin to array radar or sonar processing) to handle room effects. I am familiar with those from my (former) day job.

 

[Musical Bass]

I am afraid this reads as pure fantasy until you are able to back up those claims with some measurements and proof of some sort.

The fantasy is for sale! This isn’t our first effort as our Magellan subwoofers (Google TBI Magellans) for reviews on that model. The MS-6P is two patents beyond that!

 

[Musical Bass]

I am familiar with all of those terms and eagerly await more detailed technical explanations. The only systems I am aware of to date that counter them are active, using servo (feedback) control for the driver, and essentially acoustic waveform processing (akin to array radar or sonar processing) to handle room effects. I am familiar with those from my (former) day job.

Servo means creating more pressure! You must remember the actions of compressed air molecules is to fight back! When you compress them they help the driver in the reverse direction! Compressing then expanding while the signal inputs what is correct! Common sense but ignored because no solution! Those technologies that you mentioned have not solved the issues as they still exist! Power (force) does not overcome these issues! The MS-6P is operating with a maximum of 100w and typical power required at 30 Hz@ 95db+ in moderate size room with low distortion is about 20W. If you can modulate the pressure you reduce distortion and increase the efficiency!

 

[sigbergaudio]

The graph is not smoothed! You can see the breakup in the higher bass regions

It says right there on the graph that it's 1/6th. Or are you referring to a different graph?

 

[Musical Bass]

Servo means creating more pressure! You must remember the actions of compressed air molecules is to fight back! When you compress them they help the driver in the reverse direction! Compressing then expanding while the signal inputs what is correct! Common sense but ignored because no solution! Those technologies that you mentioned have not solved the issues as they still exist! Power (force) does not overcome these issues! The MS-6P is operating with a maximum of 100w and typical power required at 30 Hz@ 95db+ in moderate size room with low distortion is about 20W. If you can modulate the pressure you reduce distortion and increase the efficiency!

It says right there on the graph that it's 1/6th. Or are you referring to a different graph?

View attachment 134970

Yes look for the graph for passive MS-6P. The above graph is with high pass at 25 Hz and crossover at 200Hz.