@YSDR
As mentioned, at no point you have stronger magnetic field and more coil inside it, while you get less output from it. It would basically mean that with less coil and less wire, you get more output, and there is no coeficient in existance that would stop you from arguing that no field and no wire makes the most output. Be critical about it.
This is no joke about the state of the whole audio community. I am very stupid monkey, please tell me it is not worse when I look around.
Please show where. It is very unlikely.
As mentioned, at no point you have stronger magnetic field and more coil inside it, while you get less output from it. It would basically mean that with less coil and less wire, you get more output, and there is no coeficient in existance that would stop you from arguing that no field and no wire makes the most output. Be critical about it.
This is no joke about the state of the whole audio community. I am very stupid monkey, please tell me it is not worse when I look around.
Here is:
As we can see, around Fs, the efficiency (real W/dB) of the high Bl version is lower than that of the lower Bl version of the same driver. And interestingly, B&C ended up setting a Bl of 21.5 for the final version of this driver.
https://www.youtube.com/live/bIU3a872UkQ?si=X9xFDmgi4EOW29N8&t=2289
https://www.bcspeakers.com/en/products/lf-driver/10/8/10NSM76
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@YSDR
Yes, that is very interesting and noncomforming case. But if you listened, Bennett mentioned, that there is more going on at that point, it is not that straight forward. Also he said it is not easy to change Bl without changing anything else on the driver, and thus the data presented is not perfect. Also he said to basically ignore that datapoint, and go for higher Bl driver anyways. All this was ignored in order so you could keep your point. I.E.: Your reading between the lines does not end up in the right conclusion. And sorry for a blunt or less than polite expressions, I am not a native speaker, I have very few words in my vocabulary after "No, this is not working, it is wrong" isn´t working, and hitting you (parentally) isn´t an option. 🙂
Transcribed:
"Going from 20 to 27 Bl, There is a 3dB gain in efficiency which equates to a 3dB gain in sensitivity once you adjust for changes in impedance across the entire bandwith of the transducer more or less. You don´t really see it down to Fs, because Fs is a little complex and so you´ll have to trust me".
He mentioned it multiple times, that higher Bl driver is more efficient. On top of that, you are focusing on a usable band of 200Hz to 260Hz and ususable band of 100-200Hz, while ignoring usable band of 260-1300Hz.
If we start with easy, we go like that:
Sound is made by movement of the air. Air is moved by speaker cone. In order to move the air, you need to apply force at the cone. The more force, the more cone movement and more sound we get. High Bl driver applies more force on the cone at same power input, thus creating more output in SPL. If we cannot take this premise as a starting point, we cannot continue. We´re stuck on fighting very basic physics and logic.
F (force) = B (magnetic flux density) x I(Current) x l(wire length).
If Bl raises, the force F raises.
There is no way around it, and no formula that could disprove it. No math that you could hit me with to prove me wrong. I highly encourage you to find that math. What you see in the simulations are outcomes of unsuitably interpreted data, I.E.: Sound pressure level with nonequal power input to differend drivers. Hornresp can output true 1W SPL graph, I encourage you to find drivers with similar Vas and Cms, but different Bl (Re dependable) and see for yourself. It will show you the right thing. I will try for a bit to search for suiting drivers for this comparison too.
Yes, that is very interesting and noncomforming case. But if you listened, Bennett mentioned, that there is more going on at that point, it is not that straight forward. Also he said it is not easy to change Bl without changing anything else on the driver, and thus the data presented is not perfect. Also he said to basically ignore that datapoint, and go for higher Bl driver anyways. All this was ignored in order so you could keep your point. I.E.: Your reading between the lines does not end up in the right conclusion. And sorry for a blunt or less than polite expressions, I am not a native speaker, I have very few words in my vocabulary after "No, this is not working, it is wrong" isn´t working, and hitting you (parentally) isn´t an option. 🙂
Transcribed:
"Going from 20 to 27 Bl, There is a 3dB gain in efficiency which equates to a 3dB gain in sensitivity once you adjust for changes in impedance across the entire bandwith of the transducer more or less. You don´t really see it down to Fs, because Fs is a little complex and so you´ll have to trust me".
He mentioned it multiple times, that higher Bl driver is more efficient. On top of that, you are focusing on a usable band of 200Hz to 260Hz and ususable band of 100-200Hz, while ignoring usable band of 260-1300Hz.
If we start with easy, we go like that:
Sound is made by movement of the air. Air is moved by speaker cone. In order to move the air, you need to apply force at the cone. The more force, the more cone movement and more sound we get. High Bl driver applies more force on the cone at same power input, thus creating more output in SPL. If we cannot take this premise as a starting point, we cannot continue. We´re stuck on fighting very basic physics and logic.
F (force) = B (magnetic flux density) x I(Current) x l(wire length).
If Bl raises, the force F raises.
There is no way around it, and no formula that could disprove it. No math that you could hit me with to prove me wrong. I highly encourage you to find that math. What you see in the simulations are outcomes of unsuitably interpreted data, I.E.: Sound pressure level with nonequal power input to differend drivers. Hornresp can output true 1W SPL graph, I encourage you to find drivers with similar Vas and Cms, but different Bl (Re dependable) and see for yourself. It will show you the right thing. I will try for a bit to search for suiting drivers for this comparison too.
Problem is that the enclosure volume will never behave in a linear fashion as the driver does…..so how does one eliminte the chaos?…….no enclosure at all of course which allows for nearly unfettered linear motion of the cone. For A sealed system, the larger the enclosure the better and EQ to compensate. Heavy stuffing helps and an aperoidic vent even better.
……but this is of course splitting hairs………multiple subs solve the in room issues which are far more detrimental than the source. We worry about group delay at the driver while completely ignoring the meters of floor and wall bounce. Downfiring solves a lot of problems and is often overlooked……..if the driver doesn’t suffer from sag, it’s the most linear position you can place the motor…..or upfiring of course.
……but this is of course splitting hairs………multiple subs solve the in room issues which are far more detrimental than the source. We worry about group delay at the driver while completely ignoring the meters of floor and wall bounce. Downfiring solves a lot of problems and is often overlooked……..if the driver doesn’t suffer from sag, it’s the most linear position you can place the motor…..or upfiring of course.
@Crashpc
Still, the higher Bl driver produced less SPL/W around Fs, complex or not. Of course we can trust what B.P. said but why he didn't showed such a graph where the higher Bl have higher SPL/W in the whole bandwith, incuding the range around Fs? A little lame presentation, if you ask me.
Still, the higher Bl driver produced less SPL/W around Fs, complex or not. Of course we can trust what B.P. said but why he didn't showed such a graph where the higher Bl have higher SPL/W in the whole bandwith, incuding the range around Fs? A little lame presentation, if you ask me.
I watched Bennet's vid, and have the same interpretation as CrashPc.
Higher BL gives increased efficiency, but decreased sensitivity (because it raises impedance which is a good thing).
The large signal response in the meat of the passband is what counts.
Whatever is going on at fs needs to be heavily discounted .....due to what Bennet termed "confounding resonance suck down"
Far from lame, very instructive and insightful, imho.
But is still there and interestingly B&C still didn't choosed the highest BL for the presented driver for production and B.P. still didn't not proved with measurements that a higher BL driver have higher dB/W around Fs.
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We have no idea why B&C chose what they did for that driver. Perhaps cost? Perhaps how it fit within their existing line?
Big leap of faith to say that vid had anything to do with what B&C chose to make, imo.
Besides, how many times did Bennet say BL is all win, other than cost and maybe weight.
Personally, and to OP's question....I say get the highest BL driver you can for the box you have in mind.
And don't sweat fine tuning of the box size much at all.
edit: and most importantly ....do exactly as was suggested...plan on EQ from the start, using an amp that has sufficient voltage
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@YSDR
As of why, it wasn´t in the scope of the presentation and he didn´t have a product that was compliant and comparable enough in his hands.
You can pick the wrong reasons all day long, and it is somewhat good you question everything, but you can´t afford to put them as some kinds of setting facts of physics and math. You are coming from bad place, heading to bad place.
Noone was able to do better to date.
Now, here I picked two drivers and put them into 120l closed box in Hornresp.
B&C 18PS100_8 and B&C 18TBX100_4.
The vital mechanical parameters, PS100 vs TBX100:
Fs: 30/30 Hz
Vas: 245/256 l
Mms 202/230g.
Fs deviation: 0%, Vas deviation 4.5%, Mms deviation 14%.
As you can see with the outcome of the same Fs, the mechanical differences equalled each other out and the resting deviance doesn´t matter as they still outcome at the same Fs. Certainly not a noted difference for static force comparison, and close to it, I.E.: deep bass up to Fs. Don´t ask me why, it is what it is. The same way as you pointing at the graph presented by Benett.
Continued:
Motor force of these drivers: 18PS100: 9,81N/Watt, 18TBX100 11,48N/Watt. Deviation 17%. As Power scales rather with distance of the cone travelled or in accoustical environment in pressure in Pascals, it means double the effect on accoustics. We are talking about 34% "difference" in SPL/decibels. We should be at something like 1,27dB difference between those two drivers, as that is the ballpark that math dictates us.
See the Hornresp simulation:
The plot of 18PS100 driver is put in the plot of the 18TBX driver for comparison, where the stronger TBX driver is the upper curve.
At 100Hz, the SPL SPL values are 101,29/102,52 dB, resulting in 1,23dB difference. That´s very good match with 1,27dB expectation.
That´s 3% ignoring the fact that the louder driver cone will move further, facing more resistance of the suspension. Accounting for that, I guess we match in 2% even.
Now, down to the bass, the values should be somewhat converging, because at 0Hz you have 0dB. The cone at 1Hz doesn´t have enough area to move the air in order to make any SPL, the air is running off of the cone to the sides before any pressure builds. So towards the bass, we should have less SPL difference, as that power and movement doesn´t translate into SPL.
At 30Hz though, given the convergence, the values in deciBels are: 94,6/93,71, resulting in the difference of 0,89dB for the stronger motor.
In other words, the math is mathing, and your conclusions are subjective and untrue.
Did my homework. From this point on, it doesn´t even matter to me what could be the counterarguments, as long as you don´t bring more math to this. Bringing feelings and disagreement to math fight is not a good idea. Mind you, this is monkey math. It would be funny if someone was coming to destroy both of our arguments with the advanced approach.
//Edit: grammar and few minor touches.
That is again wrong coclusion, to a point of imaginary conclusion. I might be deaf as well, but at no point in the presentation, there was a choice presented between these, as if B&C company was deciding between these values, That is far fetched extrapolation that might or might not be true. You are reading between wrong lines here. These are just some lab results, and such choice might not even be on the table at B&C.
Bennett suggested, that the parameters of the drivers were not same. And so different outcomes could be happening.
As of why, it wasn´t in the scope of the presentation and he didn´t have a product that was compliant and comparable enough in his hands.
You can pick the wrong reasons all day long, and it is somewhat good you question everything, but you can´t afford to put them as some kinds of setting facts of physics and math. You are coming from bad place, heading to bad place.
Noone was able to do better to date.
Now, here I picked two drivers and put them into 120l closed box in Hornresp.
B&C 18PS100_8 and B&C 18TBX100_4.
The vital mechanical parameters, PS100 vs TBX100:
Fs: 30/30 Hz
Vas: 245/256 l
Mms 202/230g.
Fs deviation: 0%, Vas deviation 4.5%, Mms deviation 14%.
As you can see with the outcome of the same Fs, the mechanical differences equalled each other out and the resting deviance doesn´t matter as they still outcome at the same Fs. Certainly not a noted difference for static force comparison, and close to it, I.E.: deep bass up to Fs. Don´t ask me why, it is what it is. The same way as you pointing at the graph presented by Benett.
Continued:
Motor force of these drivers: 18PS100: 9,81N/Watt, 18TBX100 11,48N/Watt. Deviation 17%. As Power scales rather with distance of the cone travelled or in accoustical environment in pressure in Pascals, it means double the effect on accoustics. We are talking about 34% "difference" in SPL/decibels. We should be at something like 1,27dB difference between those two drivers, as that is the ballpark that math dictates us.
See the Hornresp simulation:
The plot of 18PS100 driver is put in the plot of the 18TBX driver for comparison, where the stronger TBX driver is the upper curve.
At 100Hz, the SPL SPL values are 101,29/102,52 dB, resulting in 1,23dB difference. That´s very good match with 1,27dB expectation.
That´s 3% ignoring the fact that the louder driver cone will move further, facing more resistance of the suspension. Accounting for that, I guess we match in 2% even.
Now, down to the bass, the values should be somewhat converging, because at 0Hz you have 0dB. The cone at 1Hz doesn´t have enough area to move the air in order to make any SPL, the air is running off of the cone to the sides before any pressure builds. So towards the bass, we should have less SPL difference, as that power and movement doesn´t translate into SPL.
At 30Hz though, given the convergence, the values in deciBels are: 94,6/93,71, resulting in the difference of 0,89dB for the stronger motor.
In other words, the math is mathing, and your conclusions are subjective and untrue.
Did my homework. From this point on, it doesn´t even matter to me what could be the counterarguments, as long as you don´t bring more math to this. Bringing feelings and disagreement to math fight is not a good idea. Mind you, this is monkey math. It would be funny if someone was coming to destroy both of our arguments with the advanced approach.
//Edit: grammar and few minor touches.
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Of course he said (but not proved fully), because the higher the BL the higher the price of a driver the higher the profit.
Perhaps there are benefits of very high BL but not around Fs, it seems.
I bet that if higher BL wouldn't decrease Qes/Qts, then the efficiency around Fs wouldnt decrease.
Same idea with the B&C decisions...
Oh, there is more to it. I am somewhat planning to test being a cheapscate - Once these drivers are driven outside the impedance minima, it is very alluring to use cheaper amplifier being "stable" at the used impedance, but not being classified as optimally performing (i.e.: 8Ohm suited amp for two 8Ohm speakers in parallel), because the amplifier will not see the load and currents in such settings. It will see somewhat 10-14Ohm load in the low impedance spots from each drivers, compared to 5-6Ohm misery that would await for it at tuning frequency. So basically, my eyes go "dollar eyes" seeing 1800W/8Ohm bridge amplifier as 2x 1800W amplifier, because the impedance will be high. There are quite some benefits with this approach. It seems to at least equal itself out with the conventional design, if not bettering it. I hope I will have time, space, money and tools to do more measurements in the future, to fully confirm that.
Yeah Bl is not static, but varies with excursion. Regarding why Bl isn't necessary as high as it could be, I think in some of Bennets videos he explains that some of the peak Bl is sacrificed to make Bl(x) curve flatter. Bl(x) is typically upsidedown u shaped, so peak Bl is when cone is centered at rest but it starts to reduce the farther the voice coil is from rest. I understood that to maintain same Bl for some excursion, the maximum Bl needs to be reduced.
Illustration, a good flat Bl(x) I found from internet and my handrawn illustration on top to show what it could be but the manufacturer chose otherwise.
It is then about marketing/customer base whether to advert max Bl value with cost of not so good Bl(x), or vice versa.
Illustration, a good flat Bl(x) I found from internet and my handrawn illustration on top to show what it could be but the manufacturer chose otherwise.
It is then about marketing/customer base whether to advert max Bl value with cost of not so good Bl(x), or vice versa.
Can you simulate and compare please with the same driver but with different BL?
I'm wondering why is the lower efficiency around Fs with higher BL in the B.P. video.
BTW, in the video the real measurements are presented, nut just a simulation.
Anyway, I would be curious.
More to it for sure.
I was trying to simply join the vote for a subwoofer system design, that includes amplification and DSP response curve flattening right from the design get-go..
Re amp matching to load....
Some QSC amps have 4-channels where channels can be combined in various configs....parallel, series, or series-parallel.
FAST stands for Flexible Amplifier Summing Technology.
Wattage on Y-axis. Impedance on X.
The Red lines bounding regions upward sloping from the Y-axis, reflect current limitations..
Blue curves sloping down reflect voltage limits.
These amps have been very helpful to me for dialing in the best amp match for whatever chosen drivers and their setup.
It helps to visualize the tug of war between satisfying low impedance dips thirst for current, and high impedance peaks thirst for voltage.
He mentioned that the drivers might not be "same enough", as it is hard to do without changing other parameters. I know it is not simulation, but as we don´t have TS parameters of these presented, we might be led on with something.
What a great idea! And while I have already seen the plot, it might give us some additional insights on what is truly happening!
Here:
18PS100, with just stronger motor.
The stronger one still leads in all points, including the Fs, but well, we see obviously there is something happening at that point, so they´re about the same.
Looking for math to explain such phenomenon. In other side simulations I see how same power and same SPL goes in and out of the driver, but I have an issue seeing why. Good part is that it is the same in just "only one point" of the response, while we need whole part of it. So the main claim stands.
But we have some lack of knowledge on our hands indeed. On it!
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I bet that an even stronger motor would show more of that 'something' and at some high level of BL, the efficiency would decrease around that point as we can see in the B.P. video.
Thanks the simulation anyway!
No need for betting, I tried to sim even more Bl(70) to be sure, and the situation stands. Outside Fs the effficiency grows, and at Fs the efficiency stands. Even with multiples of Bl. The natural feel for the issue is not that good for us, mortals. For me anyways, and for you even little less. 🙂
Sorry for the mess, the scale changed:
I have hard time putting it into the equation, but basically, it seems that the mechanical resonator has the upper hand in this. That is the damping part. Still on it. The question is, why the same power AND force goes to the speaker cone.
Sorry for the mess, the scale changed:
I have hard time putting it into the equation, but basically, it seems that the mechanical resonator has the upper hand in this. That is the damping part. Still on it. The question is, why the same power AND force goes to the speaker cone.
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Okay, it seems higher BL leads to higher efficiency in general. Similar to a lower moving mass. Of course with lower moving mass, we need a larger enclosure for the same low frequency extension.
I played with that as well, to create multi-dimensional speaker behavior idea with changing parameters. I set the cone weight to 550g-ish.
It is too much to understand at once, but basically, lower mass also doesn´t require larger enclosure in the efficiency realm, and higher mass doesn´t add to the efficiency in the low end, as the efficiency of the resonator in lower frequency is robbed by the mass instantly. We have really little idea what speaker is and what it does here. Mms game is a hoax too.
It is mathematically obvious. In order to move a mass certain distance, you need to put force onto it. Adding mass to the object obviously decreases distance travelled or increases need for more power in case of keeping the distance travelled. This is very basic stuff, that we have hard time grasping in such complex device.
It is too much to understand at once, but basically, lower mass also doesn´t require larger enclosure in the efficiency realm, and higher mass doesn´t add to the efficiency in the low end, as the efficiency of the resonator in lower frequency is robbed by the mass instantly. We have really little idea what speaker is and what it does here. Mms game is a hoax too.
It is mathematically obvious. In order to move a mass certain distance, you need to put force onto it. Adding mass to the object obviously decreases distance travelled or increases need for more power in case of keeping the distance travelled. This is very basic stuff, that we have hard time grasping in such complex device.
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