Not a shock that companies want to make as much profit as the market will bear.
The "power handling" rating being the heat the voice coil can withstand, easily over 200°C with modern designs.
The website claims "the working temperature is up to 80 degree Celsius" for the magnet your 4" coil motor design.
Better neodymium formulations using dysprosium and terbium allow heat ratings (curie temperatures) of 310-400C, working temperatures around 240C, around 3 times the working temperature of those budget motors.
Designing a driver that can deliver on paper, and one that can deliver in the real world are quite different.
A near field in room test says nothing about free field output, longevity, or distortion.
Third party outdoor tests like the CEA-2010-A above do.
No handy example, but Siegfried Linkwitz ( the Linkwitz of Linkwitz–Riley filters) made a handy calculator:
https://www.linkwitzlab.com/Amplifiers-etc/SPLmax.htm
The distortion estimation accounts only for 2nd order distortion.
The formula is taken from his spreadsheet "closed-box1.xls".
distortion in % = 0.014*Sd*Xmax/Vbox
Sd is the cone area in cm^2
Xmax is the peak excursion in mm
Vbox is the internal box volume in liters
Vbox is in the denominator, so a larger box would reduce this distortion source.
Halving the box size doubles the box air spring distortion H2 distortion:
Anyway, Siegfried Linkwitz (RIP) knew what he was doing when he made the spreadsheet.
Art
No, a "mud pump" is a driver with very low BL, little magnetic force, "muddy" sound because of little control of the cone movement/damping.
The JL GothamV2 "tick" by using two very highly damped, high powered (4500watts peak), high BL (heavy, the little box weighs in at 360lbs./163 kg) high displacement (~76mm peak to peak) well-cooled drivers.
DSP that includes eighteen bands of digital equalization for "Digital Automatic Room Optimization".
Their patents describe some of the details that differentiate them from the usual subwoofers.
https://www.commandav.com/wp-content/uploads/2016/10/JL-Audio-Gotham-Users-Manual.pdf
Anyway, nothing too groundbreaking, but a good integration of a lot of details that are often skipped in less expensive designs.
Art
The steel and hard magnetic parts of a motor do not get that hot unless it is a very high power subwoofer, thousands of watts. Motor design, cooling, and heatsinking also keep things cool.
I'm not sure what you are basing "paper vs. real world" notion on, have you done R&D developing subwoofer motors or are you just assuming things based off numbers on a spec sheet? Funny how we have made it to the point in this thread now of trying to invalidate me by claiming that I don't have any real world examples.
Gotchya, so no measured numbers. Paper vs. real world?
I've felt the LAB12 drivers magnet structure heat up quite hot in under a minute of testing using 400 watts.
They can, but difficult to keep things cool when 98+% of the power is converted to heat enclosed in a well-insulated sealed 1 cubic foot box. Heat exchangers can help.
No, I have only used existing motors for a half century building enclosures.
Looked at quite a few Klipple charts, distortion and driver spec sheets, driver failure modes, and claims over those years.
You have not provided any spec sheets, so I have not assumed anything.
They have good specs for the application.
The slab motor weight helps keep them "parked" (cabinet not walking away) at high power 😉
Art
Big difference between an Eminence sub feeling warm vs. a sub motor at 176 degrees F. Will literally burn you if you touch it. 36 degrees away from boiling water. And even if the steel does get that hot, all it takes is an upgrade to some UH or higher grade neo. Not a difficult design decision.
I am not obliged to disclose any specs or information of development of my products, especially since it is proprietary, but I find it funny how this topic has now exclusively shifted into some consumers and forum hobbyists trying to invalidate what I am making based off of minimal information that I have provided, none of the disputes being any kind of real world or quantifiable data. Apparently people here think that small sealed subwoofers are physically impossible to make, yet we have plenty of examples of them out on the market already, just with smaller drivers. I use a klippel, among other real world tools and measurements, to design my drivers.. and nothing anybody in this thread has said so far holds any relevance to this process. It's essentially just "here is how I think that doesn't work".
I am not obliged to disclose any specs or information of development of my products, especially since it is proprietary, but I find it funny how this topic has now exclusively shifted into some consumers and forum hobbyists trying to invalidate what I am making based off of minimal information that I have provided, none of the disputes being any kind of real world or quantifiable data. Apparently people here think that small sealed subwoofers are physically impossible to make, yet we have plenty of examples of them out on the market already, just with smaller drivers. I use a klippel, among other real world tools and measurements, to design my drivers.. and nothing anybody in this thread has said so far holds any relevance to this process. It's essentially just "here is how I think that doesn't work".
He clearly demonstrated the causation of low power distortion and low power THD by hundreds of measurements, which is way above just correllation. You don't have to quantify or define something by an equation for that. If you insist on that, well, why don't you just disprove that?
You obviously have never ever even remotely touched any PA equipment. @weltersys already reported 150°C, I measured 185°C on a magnet after a 4-day rave festival. Surprisingly, none of the subs were killed, though I'm sure it definitely shortened their lifespan significantly. It was not my responsibility or fault, I just helped out when a friend asked me to help out. The reason we found out was someone managed to stuff an umbrella into one of the ports and the seemingly easiest way to get it out was to remove the driver. After one stage hand burnt his fingers severely, I measured it with a laser thermometer.
No, I don't. Neither have I seen an impedance curve for their driver, nor its raw sound pressure response before it's placed in the enclosure, both of which would have been interesting. I assume that the manufacturer judiciously made use of EQ as power is cheap, albeit the driver must withstand its application.
Got a link to that?
Mechanical losses resulting in distortion would render every driver with an aluminum voice coil former or ferrofluid useless, as those two lower Qms drastically.
Did you not read my comment:
I am well aware of high power PA subwoofers, and I even mentioned that if your steel temps are that high you just need to use a higher grade neo like a UH. Not rocket science. Weltersys's observation was after over 2 thousand watts of power to the subs.. just like I said.
But we are not talking about high power PA subwoofers, we are in a thread about small box subwoofers. Different drivers for a different use case. The attempted invalidation by weltersys is that my small box hifi subwoofer motor design that is based around a retail magnet (and that I already have over a year of testing with🙄) will somehow get over the 80c steel temps that the magnet grade is rated at. It does not. Case closed.
Maybe think about crawling back into the bucket with the other crabs?
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I feel like you are smart enough with vituix cad to model a filter to match its response like you did with mine, and simulate it on that subwoofer.
Sure, that wouldn't be too difficult, but I don't see it as being particularly useful; the response is what it is. The whole point of my earlier simulations was to take a look at what an Fb = 39Hz and Qtc = 0.62 response would look like, considering that it was being achieved in a compact closed-box enclosure. It was simply exploratory in purpose, to try and gain a better understanding of a particular physical realization, and the −3dB cut-off frequency of 17Hz seemed difficult to achieve in my simple simulations.
I wrote "quite hot", estimated around 150 degrees after a short duration of pink noise equivalent to around 300watts (one eighth power of 2400 watts peak). 30 years ago Bob Carver was using more power than that in his 11" cube "True Subwoofer".
The LAB12 is an example of a driver that does not exchange it's heat well, though the heat won't affect it's ferrite slab magnet's magnetism- the voice coil burns first.
The 10" Eminence driver that I burned the coil on while testing with sine waves was hotter, as in water (saliva) instantly evaporating on it's surface, above 212F, an easy determination that did not require any instrumentation other than a finger 👎
No one has posted that they think that small sealed subwoofers are physically impossible to make in this thread, there have been examples of small sealed subwoofers measurements posted.
Fb is the box tuning frequency of a bass reflex enclosure, which does not change with the mass of the driver.
Fcb, the resonant frequency of the driver in a closed box, always increases from Fs (Free air resonance).
More Mms does (generally) lower Fs, and a lower Fs will have a flatter response in a sealed box, but that does not mean a high Fcb precludes it "to have any low end".
I simply stated the fact that the working temperature of up to 80 degree Celsius of the neodymium magnet you chose was about one third that of the 240C working temperature of the magnets used for high power applications.
If the power used in your small box hifi application does not generate enough heat to demagnetize your magnet, no problem.
Cheers,
Art
I think this is just semantics, I've seen Fb, Fcb, and Fsc used interchangeably. I think it's well understood in this context that we are not talking about a ported enclosure.
Interesting. The specifications of the 12W7 in a compact sealed enclosure are: Fc = 44.7Hz, Qtc = 0.791, F3 = 40.4Hz, Vcb = 1.375 cuft (38.94 litres). The simulated frequency response of the equivalent second-order high-pass filter is shown below. It matches up quite well with JL Audio's specifications. Unfortunately, they don't show any measured results, but I expect that they believe that Small's analysis of closed-box loudspeaker systems stands them in relatively good stead.
I already wrote the link - it's not a hyperlink though. It's the magazine.
There is a reason why I said mechanical losses in the first place. The Qms is indeed a combination of electrical and the mechanical properties. And I did mean the actual mechanical properties and not Qms.
Yes, I've read it. And he did not say 2kW average, he said equivalent to 300W pink noise. So, die you read it?
But depending on the driver (VC, ventilation etc), that can also happen to a driver with much less power. And I'll tell you why the case isn't closed. Such Xmax monsters often burn up way below their max power, sometimes even with just a fraction of it because if they can't do enough excursion, the ends of the VC can't dissipate the heat. Even if they don't burn up, the heat causes power compression, DC offset and additional distortion.
And if these mud pumps are in a sealed enclosure, they can only dissipate their heat to the air in the enclosure - which heats up without any air exchange. That means, the drivers can heat up way hotter and die with just mediocre power, nowhere near their rated power.
The analogy of bucket and crabs shows what you're used to yourself. I can tell you, there's more beyond the horizont of your own bucket.
😂 I'm the one who is breaking new ground in the subwoofer world with a new motor technology, I'm miles away from the bucket. The crabs are the ones who somehow always end up making everything about PA drivers regardless of the context or niche, and call any big subwoofer that isn't a PA woofer a "mud pump". The crabs who still try and tell you why they think what you're doing won't work even after you tell them that it's worked for a long time now. 🙄
Let's stick to the technical issues or we'll have to start excluding members from the thread.This simulation shows that in fact the very low end response is really pretty much I think actually dominated by the ratio of cone size to box volume. The notion that the bass is getting more extended may sound so perceptually but is actually kind of fake; it's really the top end getting choked off which then makes F3, F6 lower. But the actual power to put out the very low notes is hardly affected by the moving mass.
--> I think at this point, you just have to simulate each driver you are thinking of.
Hmmm, something like the red curve I'm feeling will complement a -12 dB lowpass filter which is "undertuned"
The "less low end" is because as you say the sensitivity increases but that was specified by Small as a mid-band quantity. So Hoffman applies more to full-range woofers...the "less low end" is not because the actual sensitivity at very low frequencies has changed.
Right...can someone post simulations for all to see? I'm not set up for it right now. My recollection is more and more BL, the very low frequencies stayed the same but the rise from very low frequencies would continue higher up. So you'd have a speaker with more midrange output, higher F3 F6 F10 compared to the previous, but actually the same output per watt in the low bass.