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JL Audio Fathom F113 (v2)

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1 hour ago, SME said:

 

Long term max is a good candidate for a plot,  I'll generate that when I have some time.

1 hour ago, SME said:

Might as well quantify what can be quantified,  otherwise no plot.  I would say that sub performance is easier to distill into a set of numbers than loudspeakers  where dispersion is key and equalization is more difficult due to direct vs reflected sound. neither of those is an issue for subs playing below 80 Hz.  

1 hour ago, SME said:

I picked 20 Hz as I was looking at small subs,  many of the small ones cant reach 10 Hz but I will plot at 10Hz , 16Hz, and 30 Hz when I have time.

1 hour ago, SME said:

Hoffman's Iron Law can be overcome with brute (motor) force.  The limitation then is how much magnetic flux you can ultimately focus on a coil, and whether the end result is remotely affordable.

FWIW, I spent an excruciatingly long time deciding on which subs to buy for myself.  I had a very specific location and space budget, and wanted the best I could possibly get with that space.  I had to make a custom design.  There was no chart that told me which driver would work best.  I had to consider all the possibilities individually.

 

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1 hour ago, SME said:

Well, for subs measured by Data-Bass, there are the max long-term output, power compression, and harmonic distortion plots.  For DIY systems there're also impedance and raw driver response plots which offer at least some hints as to how inductance effects may impact sound quality.

Of course none of these things can be conveniently distiled down into one SPL "output" number, but so what?  If you want the best, you're not going to find it by looking at a single chart or a single metric.  That kind of "make everything quantifiable" BS is a major error, perhaps even at the root of some of the major problems facing our society right now.  (Serious!)  BTW I say this as an engineer who specialized in study of computational science.

Also, why CEA at 20 Hz?  Many small rooms have a lot of room gain by then.  My room in particular dramatically boosts sub efficiency there.  The air starts noticeably rippling before the "signal present" lights even come on on the amp.  Tell me what the sub can do at 10 Hz, and then I'm interested.  But of course for someone who need something small to fill a large room, maybe 30 Hz is the money spot.

Hoffman's Iron Law can be overcome with brute (motor) force.  The limitation then is how much magnetic flux you can ultimately focus on a coil, and whether the end result is remotely affordable.

FWIW, I spent an excruciatingly long time deciding on which subs to buy for myself.  I had a very specific location and space budget, and wanted the best I could possibly get with that space.  I had to make a custom design.  There was no chart that told me which driver would work best.  I had to consider all the possibilities individually.

I have to agree with you there, firstly its impractical to test even all the known aspects, things like intermodulation distortion, and subharmonic distortion, are factors I consider in designs that also affect the sound but to test these adds a whole other level of complexity. Besides the fact that who besides the engineers designing drivers/systems know how to interpret them. As it stands a lot of people already don't know how or even misinterpret the measurements Databass does do. I know there are some out there who believe we know all there is to know about drivers and how they work, and how to test every aspect of them and that how they sound can be completely derived from these tests, but I have been listening to designing and building drivers for some time now and even with all the possible aspects we know about and test for I still believe its fully possible that there are things about drivers we haven't even put a name to yet let alone devised a way to test.  

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I've been mulling over a HIL type of metric for a very long time. Years...There was some discussion here at some point a while back. I had all of the data already I just needed to decide what are the appropriate measurements to use and what is the appropriate way to parse and present the data. After that it's a matter of extracting it and adding it to the DB site. 

I always thought it would be interesting to have a metric representing which units have the most output from the minimum size. 

I decided to use the maximum burst output rather than distortion limited burst for a couple of reasons. Distortion levels are dramatically affected in rooms and vehicles. Also when listening to a system we don't have an exact cut off for distortion or noise the way CEA-2010 does. It's subjective and varies by person. Some apps may not care about a distortion limit at all (Car audio SPL comps). I thought about using the maximum long term sweeps as this would produce a more level playing field between turn-key systems and the passive cabs. Problem with that is those sweeps often involve a significant amount of compression so are not a good indicator of the true short term output. 

The data is presented in a way that indicates the measured, maximum, short term output, at each 1/3rd octave band, normalized per cubic liter of volume. The data is converted to Pa and then divided by the volume that the DUT takes up in L. This is then presented in Pascals per liter. 1 Pa is = 94dB SPL. A rating of "1" in even the 125Hz bandwidth from something the size of 1 cubic liter would be a tremendously powerful and output dense system. HIL is still baked into the results. Ratings down below 20Hz are way lower than at 125Hz. I may need to compensate each frequency band so that a "0.3" at each bandwidth has the same relative weighting. I haven't thought too much on that yet.

I'm tentatively calling it A.P.P.L. or acoustic power per liter. The point of the rating is that the most output "dense" systems at each bandwidth could be determined. Also the ratings would be directly comparable. You may wonder whether a vented 18 gets outperformed by a stack of 6, 8" sealed subs, or some other outlandish scenario. It's easy to determine. If the APPL rating is higher on the 8" sealed than the vented 18 a pile of the 8's in the same volume as the vented 18 would have more output at that bandwidth. Obviously this type of information would be of limited use to most consumers but it should be a fun comparison tool for the data nerds and system designers out there. Making comparisons this way does have some very large caveats though. It does nothing to consider the cost, weight, power requirements, or number of outlets required. A pile of smaller cheaper subs may potentially out perform a larger single unit from the same amount of space, but it might require 6 power outlets, a couple of extra breakers, they could cost 3X as much, or they might weigh 3X as much. 

Anyway I've been adding this graph to some of the systems and I'm about 2/3rd's there. The ones that I have done should be visible now, but I'd consider these preliminary pending some further thought on some type of compensation at each frequency band and possibly a sortable chart of all systems similar to what we have for max burst and CEA-2010. 

 

image.thumb.png.52370213ba54f1fe5d3a402bd859be40.png

 

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4 hours ago, Wayne said:

Here is all active commercial subs on data-bass (plus the F113) . Looks to me that linear volume vs log SPL is a decent fit.  The r squared is 0.6684 or a correlation of 82%.  The JTRs also outperform the trend on output at 20 Hz vs size.

 

image.thumb.png.68dbc302cc2509a53b54d246e02a6176.png

Have to say I am kicking myself now for not sending in the square versions of the 18.0 and 21.0, those curved sides 🤔

The 18.0 we make in a 20"x20"x20" cube and the 21.0 in a 22.25"x22.25"x16", both have identical internal volume to the ones tested.

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3 minutes ago, Funk Audio said:

Have to say I am kicking myself now for not sending in the square versions of the 18.0 and 21.0, those curved sides 🤔

The 18.0 we make in a 20"x20"x20" cube and the 21.0 in a 22.25"x22.25"x16", both have identical internal volume to the ones tested.

That's another caveat with the APPL rating I meant to mention. How to deal with odd shapes and curved sides? They will get shafted a bit. It's not feasible to physically measure and calculate that stuff on my end. Perhaps the MFG could. Anyway this type of output density rating is really just for "learning" rather than salesmanship to consumers. They have a ton of other usually more pressing considerations like, cost, looks, warranty service, availability, etc. 

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2 minutes ago, Ricci said:

 this type of output density rating is really just for "learning" rather than salesmanship to consumers. They have a ton of other usually more pressing considerations like, cost, looks, warranty service, availability, etc. 

I do believe your right on that.

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Would like to ask the board a more specific question.  Looking at sealed subs in the same size as the JL113,   the SVS SB13-ultra makes an interesting comparison.  It's slightly bigger at 3.7 cubic feet vs 3.5 but it's 20 Hz output is about 5 dB lower.  Why is this?

1)  the box volume is similar and the driver is the same size

2) according to data-bass tests the SVS is not amp limited at 20Hz

3) looking at the photos the SVS driver is massive.

 

What would need to be done to have an ID sub with the same volume and 5dB more output?  Does it come down to just the driver? Why is no one making one?

Thanks

Wayne

 

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9 hours ago, Funk Audio said:

I have to agree with you there, firstly its impractical to test even all the known aspects, things like intermodulation distortion, and subharmonic distortion, are factors I consider in designs that also affect the sound but to test these adds a whole other level of complexity. Besides the fact that who besides the engineers designing drivers/systems know how to interpret them. As it stands a lot of people already don't know how or even misinterpret the measurements Databass does do. I know there are some out there who believe we know all there is to know about drivers and how they work, and how to test every aspect of them and that how they sound can be completely derived from these tests, but I have been listening to designing and building drivers for some time now and even with all the possible aspects we know about and test for I still believe its fully possible that there are things about drivers we haven't even put a name to yet let alone devised a way to test.  

Definitely agree about not really knowing what to test in drivers.  I think it's fascinating that some of the most audible "distortion" is often the hardest to directly measure.  An example of a weird thing I worry a bit about these days is how humidity changes to driver suspension might affect stability of sound quality in a very tight in-room bass calibration.  It may not really matter, or it could have rather profound effects.  I don't really know.  Perception is extremely sensitive to certain aspects of sound and seemingly completely ignorant of others.  Which stuff matters?

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7 hours ago, SME said:

Definitely agree about not really knowing what to test in drivers.  I think it's fascinating that some of the most audible "distortion" is often the hardest to directly measure.  An example of a weird thing I worry a bit about these days is how humidity changes to driver suspension might affect stability of sound quality in a very tight in-room bass calibration.  It may not really matter, or it could have rather profound effects.  I don't really know.  Perception is extremely sensitive to certain aspects of sound and seemingly completely ignorant of others.  Which stuff matters?

That's what keeps things interesting for me, always trying to learn more, the hows whys and what matters, then how to correlate the science to the perception, by no means does anyone have it "all figured out". Some of science's biggest discoveries have been accidents. I have to humbly admit I have discovered some things by accident myself.

Humidity can very well affect some materials, thick untreated paper cones would change in mass/damping properties, I have never investigated this so I cant say how significant the differences would be. Most suspensions shouldn't be affected much with the synthetic materials and resins used, temperature certainly can change them though, that is something I consider in designs. For things like that you factor for a range, min max, and make sure everything still falls within desired spec at each end of the range. Luckily we don't need worry about the speakers/subs any of us use(make) working right at -40 or anything like that, I believe that would cause some issues.

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20 minutes ago, Funk Audio said:

That's what keeps things interesting for me, always trying to learn more, the hows whys and what matters, then how to correlate the science to the perception, by no means does anyone have it "all figured out". 

 Luckily we don't need worry about the speakers/subs any of us use(make) working right at -40 or anything like that, I believe that would cause some issues.

+1

Home audio has it easy with a relatively stable environment. Outdoor pro audio work at festivals and the like is a whole other deal. The worst is car audio. 100+ deg temperature variations, random humidity and barometric pressure, road noise, etc...Forget that tightly dialed in DSP. 

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2 minutes ago, Ricci said:

+1

Home audio has it easy with a relatively stable environment. Outdoor pro audio work at festivals and the like is a whole other deal. The worst is car audio. 100+ deg temperature variations, random humidity and barometric pressure, road noise, etc...Forget that tightly dialed in DSP. 

🤔"reactive dsp" I wonder if that could be a thing, albeit prohibitively complex and expensive I am sure. Have sensors that detect temp humidity pressure and even outside noise, that feedback into a system that compensates in the dsp signal processing with some noise canceling action too.

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Since we are discussing some type of HIL related rating here...I'd like your opinions. 

Should I use max burst for it, which will tend to favor passive systems at the higher frequencies due to the absurd amount of amplifier on tap, or use the max long term sweeps which will be more granular and more fair between turn-key systems and the passive stuff, but may under represent the actual dynamic potential by a large amount?

Alternatively should it be discarded altogether? Too much work, not enough pay off, too confusing for casual enthusiasts?

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5 hours ago, Funk Audio said:

That's what keeps things interesting for me, always trying to learn more, the hows whys and what matters, then how to correlate the science to the perception, by no means does anyone have it "all figured out". Some of science's biggest discoveries have been accidents. I have to humbly admit I have discovered some things by accident myself.

Humidity can very well affect some materials, thick untreated paper cones would change in mass/damping properties, I have never investigated this so I cant say how significant the differences would be. Most suspensions shouldn't be affected much with the synthetic materials and resins used, temperature certainly can change them though, that is something I consider in designs. For things like that you factor for a range, min max, and make sure everything still falls within desired spec at each end of the range. Luckily we don't need worry about the speakers/subs any of us use(make) working right at -40 or anything like that, I believe that would cause some issues.

Thanks for your input re humidity vs speaker parts.  I don't see a rubber surround being too happy at -40 deg.

5 hours ago, Funk Audio said:

🤔"reactive dsp" I wonder if that could be a thing, albeit prohibitively complex and expensive I am sure. Have sensors that detect temp humidity pressure and even outside noise, that feedback into a system that compensates in the dsp signal processing with some noise canceling action too.

Expensive how?  A servo controlled woofer is likely to rely on (re)active DSP.  The Apple HomePod uses a servo woofer in addition to adjusting its room EQ in realtime using data from built-in mics.  I believe many cars already use active noise cancellation.  Some cars also play fake engine noise through their speakers.  I think Harley may do something like this on the outside for its European bikes, in order to provide a "Harley-like sound" while staying within EU noise restrictions.

I could definitely implement reactive capabilities with my current PC-based DSP system, if there was a good justification for it.  I live in a climate that has fairly large humidity fluctuations.  It's reasonable to assume that indoor relative humidity will correlate with outside dew point temperature, given enough time for the air in the house to equalize.  A/C usage is likely to affect things a bit too.  I now casually monitor dew points published by NWS here.  In the last week, I've seen multiple jumps from 58 deg F (14.5 deg C) to 28 deg F (-2 deg C) and back, each in less than 24 hours.

Humidity changes have a very measurable effect on absorption in the air of ultra high frequencies.  It's probably reasonable to assume that human listener adapt to these changes when listening to "normal sounds" but audio reproduction systems typically have flaws, and the humidity changes could affect the relative audibility of said flaws, leading to intermittent changes in apparent sound quality.

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26 minutes ago, SME said:

Thanks for your input re humidity vs speaker parts.  I don't see a rubber surround being too happy at -40 deg.

Expensive how?  A servo controlled woofer is likely to rely on (re)active DSP.  The Apple HomePod uses a servo woofer in addition to adjusting its room EQ in realtime using data from built-in mics.  I believe many cars already use active noise cancellation.  Some cars also play fake engine noise through their speakers.  I think Harley may do something like this on the outside for its European bikes, in order to provide a "Harley-like sound" while staying within EU noise restrictions.

I could definitely implement reactive capabilities with my current PC-based DSP system, if there was a good justification for it.  I live in a climate that has fairly large humidity fluctuations.  It's reasonable to assume that indoor relative humidity will correlate with outside dew point temperature, given enough time for the air in the house to equalize.  A/C usage is likely to affect things a bit too.  I now casually monitor dew points published by NWS here.  In the last week, I've seen multiple jumps from 58 deg F (14.5 deg C) to 28 deg F (-2 deg C) and back, each in less than 24 hours.

Humidity changes have a very measurable effect on absorption in the air of ultra high frequencies.  It's probably reasonable to assume that human listener adapt to these changes when listening to "normal sounds" but audio reproduction systems typically have flaws, and the humidity changes could affect the relative audibility of said flaws, leading to intermittent changes in apparent sound quality.

I am aware of the things you mention, what I am talking about is going the next level and implementing it in a high end system made up of all kinds of different components, and compensating for driver specific changes, meaning you would need to know what to have the system change to compensate, and where for each part of the system, a little harder to do when its not a complete integrated system. Also I am talking about not just frequency response correction. Again though there is the question of what do you bother compensating for, to what degree and would it be of much detectable value.

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5 hours ago, Ricci said:

Since we are discussing some type of HIL related rating here...I'd like your opinions. 

Should I use max burst for it, which will tend to favor passive systems at the higher frequencies due to the absurd amount of amplifier on tap, or use the max long term sweeps which will be more granular and more fair between turn-key systems and the passive stuff, but may under represent the actual dynamic potential by a large amount?

Alternatively should it be discarded altogether? Too much work, not enough pay off, too confusing for casual enthusiasts?

I think long term would be best, as most of the time the power level used on a passive system to get the highest sweep is about the amount of power that would be spec'ed for it in use, so even if a system can do more with more power in the upper frequencies most applications wont bother taking advantage of it.

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47 minutes ago, Funk Audio said:

I am aware of the things you mention, what I am talking about is going the next level and implementing it in a high end system made up of all kinds of different components, and compensating for driver specific changes, meaning you would need to know what to have the system change to compensate, and where for each part of the system, a little harder to do when its not a complete integrated system. Also I am talking about not just frequency response correction. Again though there is the question of what do you bother compensating for, to what degree and would it be of much detectable value.

That is most definitely key.

If not just compensating for frequency response, I think you'd probably want a closed-loop system (i.e. servo), which depending on design can practically compensate for "everything at the same time".  Well, that's still oversimplifying a bit.  If you want to try to reduce high order distortion, you need a very tight loop, i.e. DSP that can respond with extremely low latency.

OTOH, frequency response issues alone can be enormously important to sound quality.  It's also hard to distinguish FR from (non-linear) distortion issues with listening tests because human perception is very non-linear.  FR issues often do not become audible or annoying until one pushes the volume up high enough and may therefore be mistaken for  non-linear distortion.

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On 8/21/2019 at 5:19 PM, Wayne said:

Would like to ask the board a more specific question.  Looking at sealed subs in the same size as the JL113,   the SVS SB13-ultra makes an interesting comparison.  It's slightly bigger at 3.7 cubic feet vs 3.5 but it's 20 Hz output is about 5 dB lower.  Why is this?

1)  the box volume is similar and the driver is the same size

2) according to data-bass tests the SVS is not amp limited at 20Hz

3) looking at the photos the SVS driver is massive.

 

What would need to be done to have an ID sub with the same volume and 5dB more output?  Does it come down to just the driver? Why is no one making one?

Thanks

Wayne

 

They are both sealed subs so all output comes from the driver displacement. The enclosure volumes are close enough to disregard those differences. The SB13 fails for distortion a full 3 or 4dB before it's actual maximum output is reached. The amp should not be a contributor to distortion at all below 25Hz for the SB13. It really just comes down to the driver design and the behavior of it at high excursion. The F113 driver is clearly more linear and lower distortion at much higher displacements. If both subs are driven to the absolute limits and distortion is ignored the SB13 is within roughly 1dB of the old F113 (current v2 version may be improved), but clearly the F113 driver is behaving better.  

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