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Class D Switching Power Amplifiers and Power D/A conversion

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Old 17th January 2011, 09:32 AM   #11
gooki is offline gooki  New Zealand
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As mentioned winisd will help sort out the enclosure size, and recommended port size should you choose to port the box.

Yes it's not a cheap solution, but as your quickly realizing one good driver is often the same price as multiple average drivers. However there are sure to be lower cost units that also perform well, just keep an eye on the weight.

Minidsp is an audio dsp that can perform many functions. It costs around $100, but can replace the passive crossover components and help correct speaker short comings to some degree, allowing you to get more out of lower price drivers.

Might be best if you post up a budget for electronics + speakers so we recommend more appropriate products.

Another option for your enclosure is to modify a hard shell backpack. We have some awesome ones at work, but I suspect they cost a bomb as they protect $50,000 of equipment. However ebay/google may point you to some affordable solutions. Glassing the inside of an existing backpack is also an option.

This looks good (but not cheap):
http://www.plaber.com/3500.htm

Last edited by gooki; 17th January 2011 at 09:49 AM.
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Old 17th January 2011, 09:59 AM   #12
gooki is offline gooki  New Zealand
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Another option for your drivers is multiple fullrange units. The Mark Audio CHR-70 is fairly cheap and has the benefit of being semi water proof, however you would want grills on them.
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Old 17th January 2011, 10:02 AM   #13
v-bro is offline v-bro  Netherlands
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Why make it ported, sealed is half the size!!
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Max. cone displacement can be several foot on any speaker!Too bad it can be done only once......
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Old 17th January 2011, 10:26 AM   #14
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I would use LI-LION cells as a power source for your project, the power vs weight ratio is way better then any other battery.

Just my 2 cents.
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Old 17th January 2011, 10:27 AM   #15
v-bro is offline v-bro  Netherlands
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Or lifepo, it'll have several times higher durability and far lower danger of explosion....
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Max. cone displacement can be several foot on any speaker!Too bad it can be done only once......
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Old 17th January 2011, 10:51 AM   #16
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whats your budget mate?
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Old 17th January 2011, 10:55 AM   #17
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You should use li-lion battery's only with protection circuitry and a special charger.
But a nice explosion would be drawing some serious attention from the audience!

What about using 2 hypex UcD180ST they are cheap, have good specs, ready to run auto of the box. they need +-50V.
one li-lion cell will give you 3.7v so you will need about 26 cells to build the battery. You will skip the part of making higher voltage from 12V.
This setup will be very efficient about 92% (datasheet hypex)!

Last edited by egberttheone; 17th January 2011 at 11:11 AM.
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Old 17th January 2011, 03:12 PM   #18
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no explosions please!!!

well, I hate to put down definite numbers, but for electronics and speakers, how about a maximum of $250. And less would make my wallet smile

those Mark Audio CHR-70 's look pretty shnazzy... but their SPL is listed at 84.5... which seems very inefficient for my set up, right?

okay, so I think I now know what minidsp is... basically a crossover?

those backpacks look pretty sweet! but I agree that they are very probably out of my price-range.

again, thanks for all the help so far!
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Old 17th January 2011, 09:28 PM   #19
gooki is offline gooki  New Zealand
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Quote:
Originally Posted by 1307invert View Post
those Mark Audio CHR-70 's look pretty shnazzy... but their SPL is listed at 84.5... which seems very inefficient for my set up, right?!
Which is why you use multiples of them. 4 of them will get you 90db at 2.83v at 4ohm. 8 of them will get you 96db at 2.83v at 2x 4ohm - which is pretty much ideal for a tripath amp.
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Old 17th January 2011, 11:27 PM   #20
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Quote:
Originally Posted by gooki View Post
Which is why you use multiples of them. 4 of them will get you 90db at 2.83v at 4ohm. 8 of them will get you 96db at 2.83v at 2x 4ohm - which is pretty much ideal for a tripath amp.
Or start off with a high sensitivity driver, then multiply them?

while 8 of the drivers would get you around 94db-95 efficiency, with careful driver choice you can use two high sensitivity drivers to achieve the same level.

Bear in mind that the lower the impedence, the less efficient the amplifier is. Not really going to make much of a difference for small systems, but in larger systems the inefficiency really scales up and can create problems with both heat and current draw.
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