hispls:
Heh, that looks sick :-D
As I think about it, Impedance dip value propably IS an indicator for port efficiency. Just not the system efficiency.
In my systems I build in some years, I mostly end up in 1,45x - 1,6x value of the dip in the impedance compared to Re of the speaker. I believe possible ideal is 1,3x. If you spot you go higher, the port is just smaller and less efficient. I´d say multiples of the Re is falling in the "bad outcome" region then. In some applications you even want this, in some other you don´t. Obviously not for SPL competitions.
But when you fight for decibels per enclosure volume, there might be a breaking point, that you would rather profit from more motor force and cone area than from larger port. Depending on the measurement frequency and so on. It´s really some science in car... :-D
//Wow, you work fast!
Heh, that looks sick :-D
As I think about it, Impedance dip value propably IS an indicator for port efficiency. Just not the system efficiency.
In my systems I build in some years, I mostly end up in 1,45x - 1,6x value of the dip in the impedance compared to Re of the speaker. I believe possible ideal is 1,3x. If you spot you go higher, the port is just smaller and less efficient. I´d say multiples of the Re is falling in the "bad outcome" region then. In some applications you even want this, in some other you don´t. Obviously not for SPL competitions.
But when you fight for decibels per enclosure volume, there might be a breaking point, that you would rather profit from more motor force and cone area than from larger port. Depending on the measurement frequency and so on. It´s really some science in car... :-D
//Wow, you work fast!
Do you suppose the impedance at box tuning is purely a function of box and port geometry or is this going to be dependent on woofers? The way I see it if these subs have free air impedance of 26 ohms at 44hz getting down to 1.8 at 45 isn't too shabby.... then again I'm many years out from the few electronics classes I took and the loudspeaker as an electrical circuit is beyond my current skills to decipher.
As has been mentioned, the cabin is not too many multiples larger than the box anymore so that may well change performance with the cabin acting as a ported box into the enclosure coming the other way at it?
As to the pics, I forgot I had already downloaded them off photobucket in a zip file and uploading to imgur was very quick and easy. I got that all done while waiting on my lunch to cook.
I've got a spare sub here and more coming (deal I couldn't pass up) but I doubt more smaller subs will really help. I get a gut feeling that cone area being equal the box and port and everything else will make more of an impact.
For point of reference the neo version of the TC 3hp motor (Audiopulse Axis, Eclipse Ti, Lightning Audio Storm, Soundsplinter RL-P, etc.) uses only one of these neodymium slugs. These use a very tight gap and are extremely strong motors and very friendly on the back compared to trying to mount 80 pound + ceramic ferrite motors that I'd be using otherwise.
Of course it depends on both woofers and the box.
But as it´s two action elements here, the box matters.
The high peak has not much to do with the dip. My current 8Ohm sub with Re of 5.1 goes way over 100 Ohms at peak, but it bottoms out at 7,9Ohm with quite medium portage of 33% of cone area. The peak height is rather set by Bl, Qes and Qms parameters, while the dip is rather set by Re and enclosure parameters.
Yes, things in the car change rapidly with this kind of construction, and I must say I´m not a pro in car audio at all. So while the box might get serious upgrade, the whole system with the car might not perform as expected. I have no idea what will it do in a car.
I cannot find the exact model you posted. Looks serious. How much of Neodymium is that? Must be quite unsafe to assemble. 🙂
If I count well, the motor is really exceptionally strong. I wonder if the back plate and top plate can even handle those magnetic fields....
But as it´s two action elements here, the box matters.
The high peak has not much to do with the dip. My current 8Ohm sub with Re of 5.1 goes way over 100 Ohms at peak, but it bottoms out at 7,9Ohm with quite medium portage of 33% of cone area. The peak height is rather set by Bl, Qes and Qms parameters, while the dip is rather set by Re and enclosure parameters.
Yes, things in the car change rapidly with this kind of construction, and I must say I´m not a pro in car audio at all. So while the box might get serious upgrade, the whole system with the car might not perform as expected. I have no idea what will it do in a car.
I cannot find the exact model you posted. Looks serious. How much of Neodymium is that? Must be quite unsafe to assemble. 🙂
If I count well, the motor is really exceptionally strong. I wonder if the back plate and top plate can even handle those magnetic fields....
Last edited:
Putting together more pieces of the puzzle here. Conventional wisdom among the SPL crowd is to not get hung up on impedance curve apart from knowing how low to safely wire down to get max power out of your amp(s).
That's 6 of those slugs and I've been told that it is over-saturated, but that at extreme power levels this actually does benefit. I'd like to think they're assembled and then magnetized but yeah, they're scary strong and I could see losing fingers easily if you were trying to assemble them charged and something went wrong.
They're the "Shocker Neo-Sig" which "replace" the '05 "small gap" sig (a 70 pound ceramic motor which is similar to TC 4hp but with 3" coil, extremely tight gap, and solid top plate as opposed to tapered/threaded. There were only 50 made and built to order for "team" member competitors. They were not cheap 10 years ago and that's before the windmill craze sent the price of neodymium through the stratosphere. In any event they were built by TC Sounds and while he can't seem to run a business, I trust Thilo knows what he is doing when designing woofers.
You won't find much about them. I've got 5 and another 4 coming this fall, there's one more in Maine in a guys garage. At least one is cracked/broken (saw it on eBay about 4 years back) and from what I've been told most are owned by former world finals tier competitors who just have them stashed away as memorabilia of their competing days and will likely never see the light of day. I'm pretty active on car audio boards and the only ones I've seen come up are the ones I own.
As you say, a lot of things go out the window in such a small "room" and many things which would be undesirable and avoided for the purpose of flat 20-120hz may be exactly what I want, but I'm sure fundamentals are the same. I'm very encouraged by the idea that I could potentially triple my cone area in port and not run into trouble.
I do hope we can come up with some useful information that helps someone else along the way.
I'm guessing these folks are at the 'outer limits' with four 15" PRs [~ 25.5" dia. piston area] for a single 15", which tuned this low is going to be a very long equivalent pipe to get to 14.8 Hz at high gain: Allen Organ Products - Speakers
GM
hispls: I see. It´s just that the impedance might as well indicate efficiency, so for the same power, you might get more SPL. That was the point I´m slowly developing.
It seems to me that it has to be oversaturated, maybe creating some kinds of unwanted distortions. But as long as it serves the need, and doesn´t sound bad, it doesn´t matter at all then. I´m sure that it benefits in about any power level. It´s just that it benefits at high power levels most. Or rather it´s the ultimate benefit, deciding if the speaker will give the output you need, or don´t. And if you push it, it might as well burn from overloading much sooner.
It´s not only about losing fingers. When these beasts hit each other, they have tendency to make kind of explosive destruction. So baaad are these. 🙂
I bet these are assembled magnetized.
Anyway the motor assy looks business (serious)... Obviously the guy knows what he´s doing, otherwise he wouldn´t survive witout many kinds of possible injuries and senses damages (eyes and ears not excluding).
I can see how these will be stashed. Even I do sometimes think about buying some awesome speakers, and just stashing these. It´s funny that SPL oriented speakers didn´t really develop that much in 20-30 years, if you´re willing to pay. It´s just that it costs you less and less for the size and for decibel in time.
You also reignited that idea in me, that I should look into smaller diameters with more motor force and larger excursions. These are quite rare indeed.
Anyway, Wish you best luck with your current built. Hope we rather helped than harmed.
It seems to me that it has to be oversaturated, maybe creating some kinds of unwanted distortions. But as long as it serves the need, and doesn´t sound bad, it doesn´t matter at all then. I´m sure that it benefits in about any power level. It´s just that it benefits at high power levels most. Or rather it´s the ultimate benefit, deciding if the speaker will give the output you need, or don´t. And if you push it, it might as well burn from overloading much sooner.
It´s not only about losing fingers. When these beasts hit each other, they have tendency to make kind of explosive destruction. So baaad are these. 🙂
I bet these are assembled magnetized.
Anyway the motor assy looks business (serious)... Obviously the guy knows what he´s doing, otherwise he wouldn´t survive witout many kinds of possible injuries and senses damages (eyes and ears not excluding).
I can see how these will be stashed. Even I do sometimes think about buying some awesome speakers, and just stashing these. It´s funny that SPL oriented speakers didn´t really develop that much in 20-30 years, if you´re willing to pay. It´s just that it costs you less and less for the size and for decibel in time.
You also reignited that idea in me, that I should look into smaller diameters with more motor force and larger excursions. These are quite rare indeed.
Anyway, Wish you best luck with your current built. Hope we rather helped than harmed.
Like I said, I've built a lot of subs on that motor and mostly they're enormously peaky, moreso as you get into smaller cone sizes, but those can be made to perform well in too-small box but at that point you are killing efficiency for the sake of flat output. These days EQ is so cheap if I cared about flat I'd still build around efficiency and tame down the peak.
As you say, they do gain at lower power levels as well but the really impressive gains were guys who were already in the 170s who swapped into these and made gains. These don't even use a terribly beefy coil (compared to many car audio woofers these days) but guys throw 20,000W+ into them for 3 seconds, so in the 3 second realm I'll never buy enough power to hit the limit in 3 second power handling and it's not like I listen to music full tilt.
The best changes in SPL sub technology in the last 10 years have been just better spider and cone materials that can withstand the extreme pressures without tearing apart. Apart from that and slight tweaks to the coils, 10-15 year old motors still dominate.
Bob Carver is a big proponent of high excursion small diameter and he makes a good case for it. Considering how cheap power is these days especially under 100hz, IMO space becomes easiest thing to sacrifice when hitting Hoffman's Law. The lion's share of the car audio market has been moving in this direction since space is such a limiting factor.
Thanks for the input. I'll update in a couple few weeks after I can get this done.
I spent a lot of time working at one of the most successful automotive electronics companies, and a lot of time in one period with the amplifier engineers. Their head guy-quite a genius, really-spent an evening in a bar with me explaining that amplifiers don't really deliver power, they deliver current. And the lower the impedance they must deliver it into, the more the cost goes up sharply. In part this is because losses increase a lot (which is why efficiency goes down). This is vaguely similar to why power transmission lines operate at very high voltage, to make the current low.
I also tested amps for a long time. Now, amp tests are generally pretty crude, although the Power Cube can help. Nevertheless, I pretty firmly believe that driving lower and lower impedances is a fool's game, and that if you could really rig up the right test, you would find no increase in actual dynamic power at clipping. Not just from the amp, but because the vehicle will have difficult driving the sharp increase in current.
Really we would be better off with high impedance woofers and high voltage amplifiers, but a cascade of historical reasons have conspired against it.
Hispls:
Oh yes. I fully agree on the EQ thingie. I propably shouldn´t even mention “the flat word” in any instance, as you car guys get caught up with it every time .
I couldn´t be happier if more people understood this speaker behavior and then management, as very normal and even natural.
Stronger motor most often than not, is the solution for great amount of things. Haven´t seen many designs where it would harm things.
3seconds is not a lot of time. Could some capacitors do the job instead?
I cannot see how anybody listen to this at full tilt. It would obviously hurt ones hearing. Yesterday I played with my 21” in a room, coming close to it, and my ears hurt a little bit. Cannot grasp on how anybody can stay sitting in the car, while 3500 sq cm cone area moving over two inches peak-peak is raging right behind him. That´s nuts, and ill. :-D
I´ve been reading some speaker history, and it amazed me, that they had perfectly working speaker, and even better, “up to date” (I mean for today) plans of speakers, and knew details of its behavior, significantly before they could even use it, because there was no adequate amplifier to feed it and get sound (90-100db) from it. Those “ancients” were not as stoopid as many think…
I don´t know about Bob Carver, but I might dig into it, as there is not much stuff around at small diameter high excursion. And if it is, it´s bloody expensive for the size. Like DD, Sundown and some others.
Anyway, looking forward to see your results.
Oh yes. I fully agree on the EQ thingie. I propably shouldn´t even mention “the flat word” in any instance, as you car guys get caught up with it every time .
I couldn´t be happier if more people understood this speaker behavior and then management, as very normal and even natural.
Stronger motor most often than not, is the solution for great amount of things. Haven´t seen many designs where it would harm things.
3seconds is not a lot of time. Could some capacitors do the job instead?
I cannot see how anybody listen to this at full tilt. It would obviously hurt ones hearing. Yesterday I played with my 21” in a room, coming close to it, and my ears hurt a little bit. Cannot grasp on how anybody can stay sitting in the car, while 3500 sq cm cone area moving over two inches peak-peak is raging right behind him. That´s nuts, and ill. :-D
I´ve been reading some speaker history, and it amazed me, that they had perfectly working speaker, and even better, “up to date” (I mean for today) plans of speakers, and knew details of its behavior, significantly before they could even use it, because there was no adequate amplifier to feed it and get sound (90-100db) from it. Those “ancients” were not as stoopid as many think…
I don´t know about Bob Carver, but I might dig into it, as there is not much stuff around at small diameter high excursion. And if it is, it´s bloody expensive for the size. Like DD, Sundown and some others.
Anyway, looking forward to see your results.
Head_unit:
Hey. I have no means of disregarding your experience or denying your points. They´re fair. But In current state of technology and device parameters, it´s not really possible to do what you say so easily, and on the other hand, with superior semiconductors and switched mode supplies, it´s easy to deliver “short circuit currents” in normal working order. Switching transistors go in milliohms resistance now, and if you throw bunch of these to the “action element”, there is not much heat and losses to speak of.
The other problem is car electrification. On that one you´re absolutely right. Although the battery doesn´t have problems delivering current fast, the whole car rather does. And the battery is not happy either.
BUT, there is a reason for all this.
Power amps are still voltage sources, even though you most often want current from them. The problem is, that very strong speakers with higher impedance also have very high impedance peaks. You can touch 300 Ohm in extremes. The amp has to have enough voltage swing for these, and also current capabilities to deliver into lets say 8Ohms. These guys ordinarily want thousands of watts. 5000W is pretty normal. If you count it trough, you need over 200 volts for the impedance minimum, and you´d need 800V to drive the peak with 2000W. Basically, you´d need 1000V+ 30A+ (SOA) semiconductor. That´s not cheap, that´s not small, that´s not easy. That way they HAVE TO go for lower impedance, so the impedance peak is then let´s say 30Ohm, so the component only needs to be rated for 250V to drive the same power into it.
Hey. I have no means of disregarding your experience or denying your points. They´re fair. But In current state of technology and device parameters, it´s not really possible to do what you say so easily, and on the other hand, with superior semiconductors and switched mode supplies, it´s easy to deliver “short circuit currents” in normal working order. Switching transistors go in milliohms resistance now, and if you throw bunch of these to the “action element”, there is not much heat and losses to speak of.
The other problem is car electrification. On that one you´re absolutely right. Although the battery doesn´t have problems delivering current fast, the whole car rather does. And the battery is not happy either.
BUT, there is a reason for all this.
Power amps are still voltage sources, even though you most often want current from them. The problem is, that very strong speakers with higher impedance also have very high impedance peaks. You can touch 300 Ohm in extremes. The amp has to have enough voltage swing for these, and also current capabilities to deliver into lets say 8Ohms. These guys ordinarily want thousands of watts. 5000W is pretty normal. If you count it trough, you need over 200 volts for the impedance minimum, and you´d need 800V to drive the peak with 2000W. Basically, you´d need 1000V+ 30A+ (SOA) semiconductor. That´s not cheap, that´s not small, that´s not easy. That way they HAVE TO go for lower impedance, so the impedance peak is then let´s say 30Ohm, so the component only needs to be rated for 250V to drive the same power into it.
There's plenty of good cases to be made for high impedance speakers and high voltage amps, but power supply becomes a huge challenge since we're generally starting at 12.8V DC.
I ran this amp for a few years and absolutely loved it (sold it to my brother when I outgrew it). This makes 6000W into 4 ohms but is simply too big to be practical and they are incredibly costly and complex. Repair on this unit is about 1000$ plus shipping to and from Tacoma (the only guy in the country that will work on them).
Some folks are using Maxwell Ultra-capacitors with fair results but "bank" of 6 is still 250$ plus bus bars/jumpers and would feed an amp the size of the one I have for under 2 seconds AND they still start to become bulky. The guys who are really putting them to good use are dropping 6000-8000$ into cap banks. I think LiFePO4 batteries are going to be the way forward for the high power car guys. Far better tradeoff between energy density, fast burst discharge, and actual storage capacity. If I stumbled across the right deal on a couple cap banks I'd give it a whirl and I'm sure I'd gain, but at this stage 500$ could better be invested elsewhere.
Bob Carver interview here:
Home Theater Geeks 29: Audio Legend Bob Carver - YouTube
If you're an audio enthusiast you'll enjoy listening to him.
High sound pressure <60hz is a whole different thing than higher frequencies. It's not so much in your ears but all over. The feeling is hard to describe and addictive. I don't go full out much (apart from playing for others at shows), but it's exhilarating. I try to avoid sitting in guys cars who are louder because I'll literally toss and turn at night thinking about how I can do that myself until I get there.
Everything about audio is expensive, moreso if you're paying import prices in Europe. Deals on used equipment come up constantly in the states and if something is local, close to Christmas, etc. you can scoop up some real bargains.
Interestingly enough, the Brazilians are building some 20 and even 30KW amps which rely on 200-300V battery source and they are tiny and relatively inexpensive.
The catch being they're not allowed in most competition organizations and require 20-30 70-100 pound AGM batteries, special charging equipment, AND of course working with elephant killing DC voltages.
Again I'm not a huge fan of low impedance (head_unit and I may have even talked to the same engineer in SoCal about this issue), but with the limitations of the 12V world it's a necessary evil and the technology has come a long way to make them as good as can be.
As an aside, there's a fascinating test/writeup of a guy testing "7K" amps among which was the big Crown amp (pic related). An interesting phenomenon was that the same power at 4 ohms was louder than that power at 1 ohm.
Oh and lastly we typically gain by pushing into soft-clip when we do SPL metering.
Is your SPL currently limited by chuffing? If not, then enlarging the port without adding length is just raising the tuning frequency, which is probably responsible for the increase you've already experienced. All of this can be modeled in WinISD or other programs - at least to see the relative effect of possible changes. It will even show you port speed if chuffing is an issue.
Dan
Dan
hispls: Thanks for the reference.
You got very good point about transformating the voltage from 12V. One needs to do as low ratio as possible. Also when you´re talking about 30kW (And I don´t say you need this at the speaker impedance peak), you´d then talk about 3000V semiconductors for that hypothetical 8Ohm strong speaker. That´s really not small and cheap.
Now I´m looking around for herd of 12"s, but that´s for another topic. Yours is way more interesting...
You got very good point about transformating the voltage from 12V. One needs to do as low ratio as possible. Also when you´re talking about 30kW (And I don´t say you need this at the speaker impedance peak), you´d then talk about 3000V semiconductors for that hypothetical 8Ohm strong speaker. That´s really not small and cheap.
Now I´m looking around for herd of 12"s, but that´s for another topic. Yours is way more interesting...
Definitely beyond the point of chuffing even at 300" ^2. As you say the gain my have been from raising my peak by 2hz, either way it was a significant gain and tuning lower will be very simple to test after the port has been enlarged.
Actually it looks like they're marketing one that can produce 150,000W into 1/4 ohm
https://produto.mercadolivre.com.br...kw-150000-rms-t150-t-150-hv-alta-voltagem-_JM
Again relying on 300V DC from batteries. Still leaves you gobs of power at 4 ohm and these are short money. I wouldn't mess with that high DC voltage on a dare though! Hard to find much about the biggest ones in English, but there's a couple guys in the USA running some of their "smaller" high voltage offerings and raving about how great they perform.
No idea how they do it, and these Brazilian amps have a reputation for being somewhat unreliable, still sort of interesting how they're pushing the boundaries.
Plus 6,000$ worth of batteries and another 1000 worth of hardware to buss them together. I'm quite skeptical of the 150KW model until proven otherwise, but as I said the 30K is legit and I saw one for sale on a car audio forum <600$ last year. Typical Korean 10K is about 1500$ at cost from the build-house.
I wonder if it would be better and more interesting to make powerfull oscilators instead of full amps. You´d only need very basic output unit with filters (SMPS) and a timer.
Well, with 95% efficiency, you´d burnt 1kW with 20kW amp. That´s a lot of heat to go, but the outer case would manage. Now 6,5x that, I´m not sure. And even short term bursts would be crazy demanding on stuff inside.
Well, with 95% efficiency, you´d burnt 1kW with 20kW amp. That´s a lot of heat to go, but the outer case would manage. Now 6,5x that, I´m not sure. And even short term bursts would be crazy demanding on stuff inside.
Hmmmm. Somehow I am harking back to the Carver amps, I forget what he called the technology. Your idea seems like you could bypass the amp entirely and have an oscillating power supply. And ideally an enclosure/driver/cabin system also resonant at the same frequency. Sounds like a job for Tom Danley!
I wonder if instead of all these ports, maybe a massive sealed array could be advantageous. Huge impedance peak = low current, and some kind of high voltage resonator.
Reminds me of a lab in college wherein I decided to build a power amp but ooops didn't realize that the transformer was rated RMS, and my output voltage was too high when rectified. Well heck I thought, I'll just put in an SCR to cut the voltage. Sharply. Into essentially a 5 pound inductor. I will never forget the huge sound made by the breakers in the room all slamming off!
...I wonder if one couldn't do something similar, resonant electric circuit to feed a battery of woofers for a short period (how long for an SPL contest?)
Last edited:
Good points. I think my comments apply well still to less extreme conditions; these competitions are a different animal altogether!
Different engineer, this was in Japan. But yes it was some time ago, so technology has evolved to fit the situation.
- Status
- Not open for further replies.