Michael Gerstgrasser is simply calling thermal power compression distortion.
"Obvious the resulting current flow through the voice coil for the same speakers terminal input voltage is dropping at around 35% also – hence - SPL will drop by 35% consequently. This is a 35% (!!) DISTORTION"
Mark Gander's white paper "Dynamic Linearity and Power Compression in Moving-Coil Loudspeakers" presented at the 1984 AES convention is far more detailed and informative.
"Obvious the resulting current flow through the voice coil for the same speakers terminal input voltage is dropping at around 35% also – hence - SPL will drop by 35% consequently. This is a 35% (!!) DISTORTION"
Mark Gander's white paper "Dynamic Linearity and Power Compression in Moving-Coil Loudspeakers" presented at the 1984 AES convention is far more detailed and informative.
Here is a sim of the new 21 inch PD driver, one at rated power and one with just 100 watts (one fifteenth or its rated power!) just for Arez benefit!
There are many ways to the goal, and in terms of power compression, JBL "low TCR" voice coils are the best approach to that so far, even with 3" voice coils, no need to mention the double voice coils has as much surface area as a traditional 6"
Used in the 2216ND, 2216ND-1, 2213ND-2 for example, along with a large chassis for heatsinking / thermal transfer to the frame. And dual VC "Differential Drive".
Again Klippel will measure power compression, and give you Small and large signal parameters, as can be found in JBL EDS Transducers spec sheets of newer dates for example.
Cheap/small voice coils, in the proposed driver? Yes it is a 3", but the voice coil is far larger and more expensive to make than what's in the PD, which is a large reason for the high MMS
There is no doubt though that the PD (2155) should have more airflow and venting, as would be expected from a 5,5" coil with a lot of surface area compared to winding depth, and a motor structure that shallow, with a "traditional" design. None of that really smells expensive. It is a fairly basic transducer design optimized for PA use, simple construction, no attention to Inductance control (2,4mh on a 26mm long coil), or lowering distortion with shorting rings etc.
Silicone spiders are used for reasonable price, longevity and being good at handling abuse.
I have no doubt that they are very robust drivers though, that can take some serious abuse all day long.
Also there is no damping to see on the surround or cone, which explains the simulated impedance curve, along with a frequency response that is clearly plagued by nonlinearities from cone/surround/spider. Fluctuating +/-5 dB over it's entire range above 100hz.
the response in itself might not be a large issue though used as a sub, the effects causing it is another thing.
5-10 dB of continuous peaks and dips in the stated intended range of use, does not appear without underlying issues or shortcuts in design.
Without seeing measurements i am not very convinced of it's superiority, but each to his own
Do you really think it behaves better, when it is driven in a range where distortion is dominated by nonlinearities vs power compression?
The high BL in large part comes from the short 13mm deep gap, and 26mm winding depth (huge voice coil where?), which by today's standards is not a lot for a 21". And it will get nonlinear rather fast due to that. Reference the Klippel papers below if you do not wish to believe me.
Now that 6" coil is large sure, but resting on a thermal insulator, it keeps all the heat in the coil itself. The long 3" coil will have way more effective cooling area using a alu former which is thermally conductive, maybe you should not miss out on that point either, it also has a lot more venting.
The designs are very different, using different approaches to reach that goal.
And i did not see anyone propose a heavy rubber surround driver yet.
The best transducers generally have most of the restoring force in the spider.
Please remember that MMS is not cone weight by itself, all in all there might not be a huge difference in cone weight, which would be MMD
Except for the massive coil despite 3", heavier spider, the HST also have a heavier dust cap/assembly as that's often the weak point when using thermally conductive formers.
Yet cone mass is not really a huge issue except for it's inherent influence on efficiency.
So what makes it not capable of reproducing audio signals?
Again Klippel tests of different transducers will show you that sometimes a driver with heavier cone and lower BL, has a higher VC velocity than one with a lighter cone and higher BL
Thanks then, but i am not sure what new it should show me, as for your ELF article i read it many years ago too, and yes that web page is a good resource for several things.just for Arez benefit!
Maybe take a look at some of the linked material, that will explain where distortion comes from, and what dominates in the intended range of a sub.
And it is not from a heavy cone, a foam surround or high excursion capability with outstanding linearity.
We can easily agree on the simple fact that cone area is almost always a better way to increase spl, then by excursion though.
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Arez,
In case you didnt notice the PD is a 21 inch driver, not a 15 inch bass mid driver.
As I previously stated, the PD is designed to reproduce sub 100Hz music signals.
It does this with lower distortion and higher SPL than any of the drivers you mention.
Nothing you posted has any relevance to the PD driver performance as used in an ELF design.
The fact that ELF designs have been around for a while does not reduce their performance.
In case you didnt notice the PD is a 21 inch driver, not a 15 inch bass mid driver.
As I previously stated, the PD is designed to reproduce sub 100Hz music signals.
It does this with lower distortion and higher SPL than any of the drivers you mention.
Nothing you posted has any relevance to the PD driver performance as used in an ELF design.
The fact that ELF designs have been around for a while does not reduce their performance.
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Arez,
https://www.audioheritage.org/vbulletin/showthread.php?42399-2216Nd-1-Measurements If you think that this JBL driver is comparable to the PD 21 inch sub woofer then I beg to differ!
https://www.audioheritage.org/vbulletin/showthread.php?42399-2216Nd-1-Measurements If you think that this JBL driver is comparable to the PD 21 inch sub woofer then I beg to differ!
Sorry, I don't consider a box with a -3dB point of 72 ish hz a 'subwoofer'.
PD = pretty dismal.
PD = pretty dismal.
Anyone who doesn't understand the ELF principal will make that mistake... ELF subwoofers are designed to give outstanding results below box resonance which means the higher F3 and Fb are the better they sound over a broader range.
If the ELF design is difficult for you to understand then maybe just compare the results to your classic ported or whatever delayed resonance design you are used to... Can you post a sim for another driver capable of matching the PD 2155 in 100 liters ? To make it easy for you lets just use 100 watts
" 1 driver = 105 dB continuous (111 dB peaks) at 30 Hz. A pair in room corners will deliver 110dB continuous with 116dB peaks"
The cone never exceeds 3.5mm travel - Less than 30% of its Xmax!
Linear and non linear distortion are greatly reduced compared to any heavy coned / fat rubber surround sub oscillating / overshooting some ridiculous plus/minus 20 mm!"
Over to you...
If the ELF design is difficult for you to understand then maybe just compare the results to your classic ported or whatever delayed resonance design you are used to... Can you post a sim for another driver capable of matching the PD 2155 in 100 liters ? To make it easy for you lets just use 100 watts
" 1 driver = 105 dB continuous (111 dB peaks) at 30 Hz. A pair in room corners will deliver 110dB continuous with 116dB peaks"
The cone never exceeds 3.5mm travel - Less than 30% of its Xmax!
Linear and non linear distortion are greatly reduced compared to any heavy coned / fat rubber surround sub oscillating / overshooting some ridiculous plus/minus 20 mm!"
Over to you...
Outstanding results in what way? It's a sealed box, and below resonance the suspension and box dominate the response.Anyone who doesn't understand the ELF principal will make that mistake... ELF subwoofers are designed to give outstanding results below box resonance which means the higher F3 and Fb are the better they sound over a broader range.
If the ELF design is difficult for you to understand then maybe just compare the results to your classic ported or whatever delayed resonance design you are used to... Can you post a sim for another driver capable of matching the PD 2155 in 100 liters ? To make it easy for you lets just use 100 watts
" 1 driver = 105 dB continuous (111 dB peaks) at 30 Hz. A pair in room corners will deliver 110dB continuous with 116dB peaks"
The cone never exceeds 3.5mm travel - Less than 30% of its Xmax!
Linear and non linear distortion are greatly reduced compared to any heavy coned / fat rubber surround sub oscillating / overshooting some ridiculous plus/minus 20 mm!"
Over to you...
Some people are not tied to a 100 liter enclosure.
What is your definition of continuous? Forever and ever? If that is your definition, then I have an EBS ported enclosure that will do 30 hz at over 120 dB 1m ground plane outdoors for as long as you desire to put voltage into it. ( pro tip, the impedance maxima is at 30 hz, so power across the coil is next to negligable )
Are there any other commercial / retail examples of your ELF other than the old Bag End? There must be a reason why?
Your "points" In order:
"Outstanding results in what way?"
Read the graph, thats what Sims tell you... If you know how to read the graph. Over and above the numbers there is the small matter of the sound... It is sealed so it is time domain accurate with zero delayed resonance/port/transmission line distortion, tonally accurate and as deep and flat as you want with DSP/Eq.
"It's a sealed box, and below resonance the suspension and box dominate the response."
Again you clearly dont understand how the ELF design works... Above resonance one gains the classic " Critically Damped" mids and bass which active sealed box designs are known for, below resonance the driver suspension / sealed air volume combine and interact and are manipulated using the DSP/Eq to achieve "Flat to 30Hz" or whatever frequency the designer is aiming for. High F3/Fb is only a problem in last centuries passive crossover / ported designs.
"Some people are not tied to a 100 liter enclosure."
Excellent, if you have room for a bigger box then use a lower Q and increase sensitivity... I use a 0.5 Q with great results with 50 watts to 150 watts.
"What is your definition of continuous? Forever and ever?"
No, I dont have a definition, fortunately The Audio Engineering Society (AES) do, so I like to use that... You might want to look it up rather than read my explanation... All respected Pro driver manufactures use it, just check out Precision Devices, Beyma, 18 Sound, Faital Pro etc... Get the picture buddy?
"pro tip...."
"Are there any other commercial / retail examples of your ELF other than the old Bag End? "
You are clearly a well informed "Pro" and I am sure you do know better than all the award winning studio monitor designers using sealed box/DSP/Eq ... https://www.sweetwater.com/c405--Sealed_Active_Monitors
BareFoot Sound
Dynaudio
ATC
Neumann
Kii / Hypex/
QS Accoustics
Yamaha... Etc.,
But just in case you are wrong, maybe the most respected Pro Audio magazine can help guide you re ported bass...
https://www.soundonsound.com/sound-advice/how-choose-studio-monitors: " Putting a hole in your speaker cabinet essentially lets some of the rear‑firing energy from the woofer out into the wider world, thus improving its efficiency and letting it play more bass louder. There’s a catch, though: the port doesn’t increase efficiency across the woofer’s entire frequency range, but at a fairly specific frequency, and with some resonance. The frequency and amount of resonance are determined by the diameter of the hole, and the length of any tubing fitted to it (most reflex ports aren’t straightforward holes; tubes are used to more precisely tune their resonant frequency). The upshot is that, around the port’s resonant frequency (typically somewhere between 40 and 60 Hz, or higher in smaller monitors), the woofer will continue to vibrate for some time after the signal that caused it to do so has stopped. This resonance (properly called ‘group delay’ but sometimes simply ‘bass overhang’) can seriously impact a monitor’s accuracy. It can make bass drums sound bigger than they are (by artificially increasing their sustain), or it can make bass notes uneven in volume (the so‑called ‘one‑note bass’ syndrome). Terms like ‘plummy’ and ‘overblown’ are almost exclusively reserved for ported monitors!"
"Outstanding results in what way?"
Read the graph, thats what Sims tell you... If you know how to read the graph. Over and above the numbers there is the small matter of the sound... It is sealed so it is time domain accurate with zero delayed resonance/port/transmission line distortion, tonally accurate and as deep and flat as you want with DSP/Eq.
"It's a sealed box, and below resonance the suspension and box dominate the response."
Again you clearly dont understand how the ELF design works... Above resonance one gains the classic " Critically Damped" mids and bass which active sealed box designs are known for, below resonance the driver suspension / sealed air volume combine and interact and are manipulated using the DSP/Eq to achieve "Flat to 30Hz" or whatever frequency the designer is aiming for. High F3/Fb is only a problem in last centuries passive crossover / ported designs.
"Some people are not tied to a 100 liter enclosure."
Excellent, if you have room for a bigger box then use a lower Q and increase sensitivity... I use a 0.5 Q with great results with 50 watts to 150 watts.
"What is your definition of continuous? Forever and ever?"
No, I dont have a definition, fortunately The Audio Engineering Society (AES) do, so I like to use that... You might want to look it up rather than read my explanation... All respected Pro driver manufactures use it, just check out Precision Devices, Beyma, 18 Sound, Faital Pro etc... Get the picture buddy?
"pro tip...."
"Are there any other commercial / retail examples of your ELF other than the old Bag End? "
You are clearly a well informed "Pro" and I am sure you do know better than all the award winning studio monitor designers using sealed box/DSP/Eq ... https://www.sweetwater.com/c405--Sealed_Active_Monitors
BareFoot Sound
Dynaudio
ATC
Neumann
Kii / Hypex/
QS Accoustics
Yamaha... Etc.,
But just in case you are wrong, maybe the most respected Pro Audio magazine can help guide you re ported bass...
https://www.soundonsound.com/sound-advice/how-choose-studio-monitors: " Putting a hole in your speaker cabinet essentially lets some of the rear‑firing energy from the woofer out into the wider world, thus improving its efficiency and letting it play more bass louder. There’s a catch, though: the port doesn’t increase efficiency across the woofer’s entire frequency range, but at a fairly specific frequency, and with some resonance. The frequency and amount of resonance are determined by the diameter of the hole, and the length of any tubing fitted to it (most reflex ports aren’t straightforward holes; tubes are used to more precisely tune their resonant frequency). The upshot is that, around the port’s resonant frequency (typically somewhere between 40 and 60 Hz, or higher in smaller monitors), the woofer will continue to vibrate for some time after the signal that caused it to do so has stopped. This resonance (properly called ‘group delay’ but sometimes simply ‘bass overhang’) can seriously impact a monitor’s accuracy. It can make bass drums sound bigger than they are (by artificially increasing their sustain), or it can make bass notes uneven in volume (the so‑called ‘one‑note bass’ syndrome). Terms like ‘plummy’ and ‘overblown’ are almost exclusively reserved for ported monitors!"
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@Hydrogen Alex: you can quote (parts of) a last post by selecting the text, and clicking "quote" which pops up.
Just testing the quote option
with the latest (Dec 2023) legendary ATC sub woofer using the sealed ELF principal... https://atc.audio/hi-fi/loudspeakers/subwoofers/c4-sub-mk2/I have the spec sheets, and the T&S models in software so i am well aware, i guess i was not clear enough about what i meant, sorry.
And i would totally agree with you on that ofc.
I did not say the 2216 is comparable, it is a midbass, just pointed out that there is many ways to combat power compression, and voice coil diameter is not the only way to do so, so you can't judge a transducer by it's voice coil diameter in terms of power compression. If it's based on a similar motor structure and design, then it might give you a hint.
The manufacturer spec sheets pretty much state what range and use they are intended and designed for.
What we choose to use them for is another thing.
Based on a sim of T&S parameters?
The smaller the closed box the higher the distortion in the low end btw, especially in a room.
A small box is good if you have a driver that is plagued by suspension nonlinearities, as they used to be, else it adds nonlinearity to a noticeable extent.
Where is the distortion measurements, with a reliable third party or from the manufacturer?
As the Klippel chart i linked above shows, what actually has the largest effects on distortion below resonance, namely suspension linearity and the box, as was pointed out above.
Which part of PD's datasheet or the sim shows that?
Also i did not see i suggested more then one driver anywhere.
I did not see anyone state that either?
Yes it is clearly not affected by the laws of physics, unlike all other tansducers, it does not have any sorts of nonlinearity, because it was made by PD, and you say so, understood
Also ELF stands for? Extended low frequency.
What about 30hz, is extended low frequency?
I asked you what YOUR definition of continuous was, not someone else's. Keep in mind the limits of your AC breaker sizes, and thermal rejection of your driver in a sealed 100L box. Drag your 100L sealed PD box out in 80 degree freedom unit full sun on the pavement, and apply as much power as you like to generate as much SPL at 30 hz at 1m as you can continuously. Ramp up the power 1dB at a time until the driver fails, like the JBL 100 hour tests.Your "points" In order:
"Outstanding results in what way?"
Read the graph, thats what Sims tell you... If you know how to read the graph. Over and above the numbers there is the small matter of the sound... It is sealed so it is time domain accurate with zero delayed resonance/port/transmission line distortion, tonally accurate and as deep and flat as you want with DSP/Eq.
"It's a sealed box, and below resonance the suspension and box dominate the response."
Again you clearly dont understand how the ELF design works... Above resonance one gains the classic " Critically Damped" mids and bass which active sealed box designs are known for, below resonance the driver suspension / sealed air volume combine and interact and are manipulated using the DSP/Eq to achieve "Flat to 30Hz" or whatever frequency the designer is aiming for. High F3/Fb is only a problem in last centuries passive crossover / ported designs.
"Some people are not tied to a 100 liter enclosure."
Excellent, if you have room for a bigger box then use a lower Q and increase sensitivity... I use a 0.5 Q with great results with 50 watts to 150 watts.
"What is your definition of continuous? Forever and ever?"
No, I dont have a definition, fortunately The Audio Engineering Society (AES) do, so I like to use that... You might want to look it up rather than read my explanation... All respected Pro driver manufactures use it, just check out Precision Devices, Beyma, 18 Sound, Faital Pro etc... Get the picture buddy?
"pro tip...."
"Are there any other commercial / retail examples of your ELF other than the old Bag End? "
You are clearly a well informed "Pro" and I am sure you do know better than all the award winning studio monitor designers using sealed box/DSP/Eq ... https://www.sweetwater.com/c405--Sealed_Active_Monitors
BareFoot Sound
Dynaudio
ATC
Neumann
Kii / Hypex/
QS Accoustics
Yamaha... Etc.,
But just in case you are wrong, maybe the most respected Pro Audio magazine can help guide you re ported bass...
https://www.soundonsound.com/sound-advice/how-choose-studio-monitors:
Have you any of your own data to show, other than conjecture and simulations?
By the way, I checked out Sweetwater, and jeez, they sell ported monitors too !!!
Neumann ported monitors: KH80, KH 120II, KH150, KH420, Focal makes ported monitors, so does Kali, so does ADAM. Wow, even Yamaha has ported monitors !!!!!!! 
Anyone who doesn't understand the ELF principal will make that mistake... ELF subwoofers are designed to give outstanding results below box resonance which means the higher F3 and Fb are the better they sound over a broader range.
If the ELF design is difficult for you to understand then maybe just compare the results to your classic ported or whatever delayed resonance design you are used to... Can you post a sim for another driver capable of matching the PD 2155 in 100 liters ? To make it easy for you lets just use 100 watts
" 1 driver = 105 dB continuous (111 dB peaks) at 30 Hz. A pair in room corners will deliver 110dB continuous with 116dB peaks"
The cone never exceeds 3.5mm travel - Less than 30% of its Xmax!
Linear and non linear distortion are greatly reduced compared to any heavy coned / fat rubber surround sub oscillating / overshooting some ridiculous plus/minus 20 mm!"
Over to you...
The Faital Pro 18XL1800 has comfortably more excursion-limited output than the PD driver, if that's your thing.
FWIW, when you bandwidth-limit to below the system resonance, there will be no overshoot. I can see that might be unintuitive, but essentially the driver is moving very very slowly compared to what it's capable of, and is therefore capable of following the waveform within the linear limits of the driver.
Chris
Yes, but do notice the Faital xmax calculations, is more optimistic then what most manufacturers use
They give it that way for good reason? Look at the Audioxpress review of the cheapest Faital 18" with neo magnet, the 18FH500 that not even having shorting ring(s):Yes, but do notice the Faital xmax calculations, is more optimistic then what most manufacturers use
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