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From Tony D at Rockford.....
This is a picture of the ORIGINAL prototype. At this point it had not been dubbed the "D'Fibrillator" yet. In fact at this point I had no idea if it was going to work or how much power it was going to make. If you look closely you'll see that there are 2 circuit boards back to back with about 2 inches between them. Those are output sections from T15002s. The MOSFETs used in the T15002s were not going to be able to handle the amount of power I wanted to put through them without overheating and blowing up so they are mounted to 2 inch aluminum square tube which had the coolant being pumped thru them. In the pic you can see the coolant reservoir and below it and to the left is the pump. We filled the reservoir with coolant that was in the freezer at 0 deg F and ice. The box underneath the output sections contained 12 motorcycle batteries all wired in series for 151.2 volts. Not pictured is the power supply that would convert 12V to 150V and charge them. (The T15kW runs at 136V in production trim). The MDF box in the picture is about 30 cubic feet ported with (4) T215D4s wired down to net (2) 1 ohm loads. Like I was saying I didn't know how much power it would make exactly so during the sound-off we had an Audio Precision system one connected to the output of the amplifier to measure its power. We made several trips through the lanes, each time I would push it a bit harder. First run was like 3000W 153db. Next run was around 7kw 156ish. Final round 10kw for a 158db at which point we had won. So because of this we decided to let it all hang out and see what she had. The result.... 15,030 Watts and a 160.3db. Thats how 15kW became the target. I just had to find a way to make it play music and not use motorcycle batteries.
here is more to the story from a post ive had on my site for a minute or two
im tryin to get more pics out of him now
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Yes it is true the idea came from a defibrillator. It seemed silly to me that all these guys in the db drag lanes need to have 1/2 of their vehicle full of batteries and alternators to maintain a decent B+ voltage for a few seconds. That and the fact that the amount of total energy all those batteries contain is huge and they are only using a fraction of it during their burp. It is like taking a NASCAR car to a drag race. A vehicle that is designed to go 200mph for hours on end probably isn't the best design for a 1/4 mile burst.
So when you look at the way a defibrillator is used its like burping an amp. Defibrillators don't have massive power cords that need mega amps at 220V, in fact some of them are portable and run off a very small battery. Why, because they don't need to shock someone for hours at a time, just a quick burst. They just draw a small amount of power continuously during 'charge up' and once all the energy they need is accumulated they release it all at once.
With the operation of the defibrillator in mind, I tried to apply it to car audio. I set off to build a prototype which was based on (2) T1500.2 output sections, I had to liquid cool the MOSFETs because even the FETs in the T1500.2's were not big enough to handle the kind of power I wanted. By keeping them very cold they could be pushed beyond their limits. (This may be the radiator ect... part of the story that someone posted). Then I needed a way to store a bunch of energy, electrolytic caps and some of the carbon based caps that are commonly used in car audio were not even close to being capable of storing the amount of energy I needed, so I used 12 small motorcycle batteries in series to get 140+ Volts. Then I built a power supply that would convert 12VDC to 140VDC to 'charge' these batteries.
I got this contraption all put together the night before the Annual Rockford Fosgate Employee Sound-Off. I didn't really how much power it would make exactly, but to try to shorten this long story it ended up putting out 15,030 Watts RMS! This is how 15k Watts became the goal for a 'real' amp.
The first step towards making it a 'real' amplifier was I had to eliminate the array of batteries. I began searching high and low for something that would do it. I found a company that makes capacitors for hybrid cars and large wind turbines. These worked perfectly. The caps I ended up using are 400 Farads, and there are 180 of these in the T15kW. Then I needed an intelligent power supply that could monitor these caps and add energy to them as needed, and it had to be fast, really fast if this amp was going to play music and not just a burst. So during music these caps are charging, discharging, charging, discharging. The power supply in the T15kW can charge the caps 35,000 times per second.
Of course many other things had to happen like finding MOSFETs that could handle it, a way to keep it cool without antifreeze and car radiators ect. The final product met all the goals and then some.
The main idea is that with this technology the amplifier can put out more power during transients or bursts than the car it's connected to could supply.
Again thanks for the props, look for hybrid technology to hit our smaller amplifiers in the near future.
PS if you guys would like to see pictures of the original liquid cooled proto I'll post them. This proto was eventually dubbed the D'Fibrillator. haha
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Tony D'Amore
Design Engineer
Rockford Corporation
MultiQuote
That's just freakin' nuts. I was wondering how the whole 15kw came to be. I love to hear a good R&D effort turn up some useful results/technology. 
