20 KW amplifiers

How its done...

Generally, you use multiple amps in some interesting ways. Big jobs like this typically use one amp as a voltage source. This in turn drives lots of other amps simply as current sources. Music is not the test, spl is. That leads to other problems. The drivers must be time aligned to the measurement point, so the mulitple drivers are delayed so that thier wave hits at the same time. Visualize the method that the Germans proposed for thier superguns, where additional detonations are added as the projectile passes. Obvioulsy, the pressure wave must be added at exactly the same time. The absurd high end of these "vehicles" are often measured over 170dB. No human could likely survive in these.

Multiple amps is the only way to do this. Building a 20kw amp is not hard, we do it all the time in broadcast using multiple solid state modules. It is stupidly expensive.

But to answer the question, you will need multiple amps. Build one simple as a voltage amp. One gain stage. Then build as many current supplies as needed to meet your goal. Bunches of MOSFET's are needed, both for the switching powersupplies (they can be slow and nasty as nothing over 100hz is needed), and then the current stages. Your drivers will likely max out at 1kw each, and only a few can be on the same time alignment depending on your driver layout. Rinse and repeat. Be prepared that the top of the line sometimes run over 40kw. BTW, you are not going to buy this - someone is going to build it.

Think piece - just how many MOSFETs will he need for 40kw into this 1 ohm load? Remembr sound quality is not important, neither is high freq.

[Edited by Sawzall on 10-08-2001 at 04:33 PM]
 
The point of it?

This is an engineering exercise for some, a compitition for others. It is not musical for this extream care. However, it does have benefit for us in that anytime someone explores the envelope, discoverys are made that we can use. They call it dB drags, and like racing, some of the technology will creap down to us daily drivers. For example, the 1 Farad caps are now reasonable in price (and coming up in voltage too - think of these rated at 100volt at $100 bucks each and how much simpler will your power supply problem become?), and have added some real help to my mear mortal of a car system to resist the voltage drop that even a car battery will see when suddenly faced with an instant 50 amp current draw at 13.8 volts- not that uncommon when driving two 12" subs with even modest levels. (My car has a total of about 1kw of total amps for 10 drivers - high, mid, low and sub) In the past, the rails just drooped and clipping was not far behind.

Some of the switching power supplies that are common in lots of gear nowdays is rooted in car technology (Soundcraftsman was making these 20 years ago). Its made it a great deal cheaper for all of us since these devices are made in the thousands instead of the hundreds that "audiophiles" would have bought. Driver makers are learning a great deal since they have a steady market for big drivers that must deal with huge loads - how long ago was it that a woofer driver would have bailed out at a few hundred watts. Now days, they often can see 1000watts RMS. Sure, most of that is "unmusical" but the technology is used by drivers that we want to hear.

People are exploring 5.1 technology in cars, which is great since soundstage is difficult in cars. This will benefit all of us - think of it as the space race. Sure it was expensive for the pioneers, but we as a whole sure gained a lot from it. For example, they are figuring out ways to deliver that wattage without the need for the cooling towers. How to time align drivers in an exact way. Signal processing. I can go on, but you can see some of the challenges they face and figure out how to overcome. It will trickle down to us. Take in a show and you will be amazed at the quality of the sound they are getting out of thier cars - sure lots of system are built just for thump, but many more are built and judged for true sound quality (winning cars eq to less than .2 db flat) and the car is a much tougher case than your living room.

So like ProSound gear, this segment offers cubic bucks thrown at the designers - we get the benefits in our segment as they learn more.

(Sorry for the length)..
 
Hey to each their own. I believe however that you are misinformed on a couple of points. Firstly, Switch mode power supplies most certainly did NOT originate in this application. Secondly, power of this magnitude is not uncommon in pro-audio applications, which makes me wonder just how likely it is that real developments in this area will influence main stream or even audiophile circles. Contrary to what you may believe it is not difficult to make a high power driver when efficiency and quality are not factors, the reason none were available before is because demand for this type of device was too low to concern manufacturers.

Having said the above, I agree there is a technological challenge involved, indeed quite considerable from a DIY perspective. I’m not sure if I would agree with your analogy of drag racing, maybe “monster trucks”, or those cars that jump around by remote control (what are they called anyway?). Certainly past-times that push the envelope. Expand it? Maybe not.

Good luck with the project anyway.

Cheers,

Pete Fleming

PS One question. Why maintain the 12 (13.8) V system in the car? If the main power consuming devices in the car are the amplifiers then why not chose the appropriate voltage for that application and reduce this rail to 12V for the normal car systems. I’m sure it would be possible to have an alternator custom wound, and it sure is a hell of a lot easier to reduce DC voltage than increase it.
 
Not misinformed, but realistic. Sure switched mode were not first used in cars - but I would bet the first time commerically widespread. Carver was using these type amps in pro audio in the early 80's - I know, I probably flew a thousand of them over the years. They were not cheap, just more efficent and light weight (and when you needed 40 or 50 of them, it counted). You still stacked Crowns or Crests on the floor for the subs since they really sucked for low freq. Nowdays, you can buy a 2kw/2ohm amp for less than $800 all day long. But I am willing to bet that more switching poweramps are sold for cars than all other applications.

Your statement about drivers is incorrect in that power is important, but so is efficiency as well as extension. We both know that only a few dB of driver efficiency drop would waste an absurd amount of power when at this extreme level. Secondly, drag racing enticed kids to "soup up" their cars, so parts makers made those parts. No, they were not pure race parts, but they were performance. Car makers noticed it too - therefor the muscle car era.

As for the voltage, its the rules. Sure it would be easy to just bank up some batteries for the voltage of your choice - infact, most of these do have battery banks - but the rules stick you to the 13.8v.

And I agree with you, good luck to your project, yeehaw. Enjoy it - and thats what this forum is for... and all little bickering aside, everyone here will be glad to help anyway they can.
 
most of the heavy hitters use 1-2 1kw-2kw commercially available amplifiers per voice coil on their speakers. with even 2 DVC speakers, you can begin to see how expensive this "sport" is. The most famous car uses 48 10" square kicker solobarics with 48 kicker zr1000 amps. I'd venture to guess thats more powerful than half of the radio stations in america.

I think the rules for dbDrag anyways is that all equipment must be unmodified and available to the public. So DIY amps are out :/ The maximum voltage limit is 18V. The cars that win require so much more effort and money than the cost of equipment used, but they are indeed engineering marvels.

A lot of the rules are pretty stupid. but all forms of competition have them. like restrictor plates(nascar) or treaded tires(F1). When will we have a no rules "bring what you got" racing series? I'd like to see somebody turn a 30 second lap at laguna seca. dbDrag has the 40hz-80hz window.

jt
 
Ah, there are “rules”. Well ok.

Sazwall perhaps we are talking about different things, however I am referring to Switch Mode Power supplies, which was the term you used (or implied by “switching power supply”). Next time you turn on your computer or your television ponder for just a few seconds as to what powers them. Switch mode power supplies have long been used in domestic situations as the offer very high efficiency, and have a high tolerance to input voltage variation. Indeed it’s not difficult to make them “universal voltage” capable. Unlike linear power supplies a large transformer is not required, hence for high power applications is cheaper to manufacture.

I suspect what you are referring to is actually an inverter, and would not doubt it gained popularity in this application.

Cheers,

Pete Fleming
 

blmn

Member
2001-02-01 2:43 am
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yeehaw,

Try http://www.corzus.com.br, they have an competition amp called matrix wich delivers (they claim) 3500W continuos (bridged mode) for a few seconds.

I reached 800W continuous in class B using mosfets at output and now I´m trying to reach 1500W using Tripath or HIP4080 circuits.

As some fellows said in this thread, the SMPS project is not an easy task, but it´s possible to do. In your case, however, SPL competitions not allow DIY prototypes in most cases.
 
hi.

we design and build high power pwm amplifiers/modules and were interested in testing them in db drag competitions.

when we read the rules we werent that interested any more, the rules dont say anything about music , they "measure" the loudest one note tone in a given car for 10 secs. (correct me if im wrong)

i suggested using a fog horn (hehe)....

some of the competitons i saw were powered by chargers as the batteries and wiring in the cars were totally useless for high power applications.

12v and 5000watts should give like 400a of current :)

i still think that a 1000w car amplifiers mates (only) with a 1000w car speaker as none of them are really more than say 50 w :)

using them with pro audio equipment can cause destruction (let alone some homour...)

bye k madsen - http://www.cadaudio.dk

ps. as some of you may have guessed we come from the pa business ....
 
5kW for car audio????!!!!

Yeehaw, don't know if you're already into the car audio stuff seriously. IMHO you DON'T need 5kW to power a sub in a vehicle for anything short of being the next world SPL champion.

My own installation consists of 2 nos of 4-channel high quality power amps rated at 4 x 50W each. One of them, when running in the bridged mode churns out 2 x 100W each (4 ohms) and 2 x 200W (2 ohms).

Using an active crossover, one amp runs in a 4 channel configuration driving front and rear speakers while the other amp runs in the 2 channel mode driving 2 nos of 12 inch subwoofers, mounted in a sealed box of suitable size, Q total of 0.7.

And the point is, it gets bloody loud, enough to shake nearly everything in the vehicle (a 4 wheel drive SUV!) including stares from passerby!