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Class D Switching Power Amplifiers and Power D/A conversion

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Old 13th November 2004, 12:19 AM   #21
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Default Schematics

See the automotive section of www.schematicsforfree.mattsoft.net. You will find a schamatic for a Kicker brand amp that delivers 1000W to the LF. Build that for practice first. Then, from what you learned from that, tackle the 5000W amp.
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Old 13th November 2004, 12:23 AM   #22
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Default Generator

Yes, connect the sub directly to the 50 or 60 Hz output of a generator, through a triac. Then extract the bass line from the music with a bass beat extractor like on www.schematicsforfree.mattsoft.net in the lighting section send the output to the triac set to switch on at zero crossing, pulse the AC at the beat rate of the music.
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Old 13th November 2004, 11:14 PM   #23
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hi all there,

I sugest the other solution. build your own drivers with x max 1 to 2 mm102-108db/w/m or 109-112db/w/0.5m , make sure that magnet is from bla bla bla another planet with really strong magnetic field (like lowthers do)

conect in paralel 10 of them ant do some nice input by vdo dayton cdp. I quest 10 to 15 wats will be enought to reach 150db spl

luck in your mad projects
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Old 14th November 2004, 01:46 AM   #24
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thanks for the suggestions, im trying to keep all the install in the boot, but those schematics look very interesting, thanks
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148.6dB In Car System, needs to get louder i want 150dB+
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Old 15th November 2004, 06:21 PM   #25
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Default another suggestion

The way with less amp power needed could be a resonating impedance transformer (p converted to v) -> (folded) horn, transmissionline e.t.c.
Check, if you can do this first. The settling time is long enough to allow a high Q for a high sensivity/efficiency. But you would need specialised drivers of course. And: the bigger the radiating area, the better is the directivity (-> beaming, have a look into PA-forums).

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Old 15th November 2004, 07:41 PM   #26
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Mr Kelley, 5000 watts in your car, is it for music or some test signals? 150 dB, are you in the car when you have 150 dB's?
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Old 15th November 2004, 08:56 PM   #27
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150dB is with sine waves, realistically music it will play around 145dB. any yes i do sometimes listen to it pritty loud from in the car but not when playing a test tone as i would still like to have some of my hearing later on in life
Transmission line would be good however space is a issue, i need to keep the system in the boot and so only have about 6^ft to play with. the trunk is aproximatly 42"long by 16" high x 21"deep. - displacement of wood/sub atc i cant see this being a viable option. i do not wish to change the 15" sub either.
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Old 23rd November 2004, 03:27 AM   #28
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You can add the output of a string of amp in series if you connect them with output transformers. Take a reasonable size amp that you can buy (1 KW for instance) and the total you are after- 5 KW. You will need 5 amps. Each will be driving 1/5 of the total load. Added in series then each amp will be driving 2/5 or .4 Ohm. Use matching transformers, AC power transformers in this case, scaling them for the V in to V out ratio appropriate to this task and connect the secondaries in series. Doing this in parallel increases the chance of amp destruction. Not done normally because good transformers are heavy and expensive.

You still won't get there because the voice coil of the driver will heat up enough to reduce your output appreciably during your test. And this is assuming that the magnet won't get demagnitized during the test. Both are real phenomena and will make the problem much harder to overcome than just adding more watts. The technical term is power compression. You could use Helium cooling, it may work. Its used in cutterheads for phonograph records.
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Old 24th November 2004, 02:00 AM   #29
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I have a close friend here that just break 172dB with 2x12" subs. He uses 1 power amp.
I often visit his place and follow his rising records. When he hits 145dB, it is on ordinary car. When he breaks 150dB, he uses 8x15" subs with 16 classD power amp.There are stiffing wood bars everywhere in the car. When he hits 170db, he uses 2x12"sub with 4 power amp. The car maybe add another 700kg weight from treatment. Now he does 172dB with 2x12" sub and 1 power amp--> now you couldnt drive the car. You have to pull out 50% of the setting to be able to drive the car. When he arrived the SPL arena, he puts back the 50% back.

Power rating and subwoofer number has minimal effect in building competition SPL car. The most important is treating the car as a bandpass box. Measuring the volume for front box and rear box, while you are sitting on one of the box. The mike position is also very important to know. In his car, you shift the mike 50cm, the SPL is only 150dB, but in the exact position (passanger's seat with 50cm mike holder you get 172dB).

So, you will have to put 1/2" thick resin everywhere in the car room, stiffen the roof and lower deck with 1" MDF, make another front glass with 1/2" glass, stiffen the doors with resin and put tons of asphalt sound damper inside the car.

Any system more than 145dB is dangerous for yourself, especially for hearing. That SPL friend of mine just dare to stay for 3seconds inside 155dB car. I try 155dB with him for 3 seconds. It's feels like your hart and brain is just empty room. Couldn't think of anything and walk straight after hearing 155dB SPLcar. Takes 3 minute to recover after 3 second shake.

More than 155dB, hmm..... I think no one will try it inside the car, even the world SPL champion.
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Old 24th November 2004, 06:58 PM   #30
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your friend obviously has a walled SPL car,i compete in the street classes so everything must fit in the trunk. The pressure sensors we use are the termlab, your friend uses the audio control mic from your description. term lab is much more linier than the ac mic as it is based on a pressure transducer rather than a microphone, this makes it much more accurate at higher levels. the 148.6 i currently hiting my car is 152.x on the ac mic as far as i can remember. i have sat in a car of 155+dB at 40Hz on the termlab sensor so i would guess 158-160dB on the audio control mic and yes i can confirm this is scarily loud. This was in a car tuned to 18Hz for street bass, i would hate to think how loud it would have been if it was tuned to 70-80Hz like mose walled spl cars.
As said i cannot wall my car because of the class i compete in, infact i couldnt use the planned amp in competition either, but i just wanted to see if i could do it for my own benefit.
I have modified my box now and think i have managed to gain a dB or so(it sounds louder to me, but havent had time to put it in on the sensor) So i may well be able to make the 150+dB without a new amp
If i can the next target will be 155dB this is going to need a lot more effort as the world record in my class is 155.2dB although i believe they were running 6KW or so.
The current UK reccord is at 149dB i plan to beat this at my next event
My car has no sound deadening at all so if i deaden the car i hope this will gain me a dB or so.
I have been told i can borrow a matched pair of amps off a friend next season which will give me 6-8KW depending on the sub i use.
If anyone has any more suggestions on how i could improve my output, please feel free to reply
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