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Class D Switching Power Amplifiers and Power D/A conversion

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Old 19th June 2008, 09:41 PM   #131
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woop woop, received the speakers.

I've decided to go for just the two for now, but I need some help designing a case. I hear that its dimensions are pretty important. So what data do we need? I'll try to provide as much as I know for now.

The case is going to be made with 20mm plywood, the arrangements inside it will be left - battery - right speaker. That is, the good ol' design for a boombox.

I sincerely hope the bass will be more clear when it's all installed in a case
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Old 22nd June 2008, 04:22 PM   #132
MortenJ is offline MortenJ  Denmark
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>>Jchilerup: If the woofers are not placed in a cabinet the soundwaves from the front of the speaker are cancelled out by the waves from the back, especially in the lowest frequencies. So it will sound a lot better in a cabinet.

My boombox is almost ready now, the paint is drying up now so it should be finished in a few days. I went for two 6.5" woofers and two piezo tweeters powered by an Amp6 Basic from a 12V, 12 Ah sla battery. Can't wait for it to be finished.

>>Saturnus: I'm up for a small competition.

Morten
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Old 24th June 2008, 01:57 PM   #133
m4gnus is offline m4gnus  Denmark
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So cool project - but could we please get some dimentions?? What size is the box, how tall, deep and long is it? And don't you have som photos from inside it? It could be nice to see how close the magnets are..
Thanks
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Old 24th June 2008, 02:13 PM   #134
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The magnets are pressed together. And the dimensions you can find in this thread.
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Old 24th June 2008, 04:02 PM   #135
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Quote:
Originally posted by Saturnus
@Janoch

The magnet to magnet construction focuses the magnet fields in the driver and gives a slight increase in sensitivity of roughly ½dB per driver, resulting in a 1dB sensitivity increase per speaker pair ... that may not sound like a lot but 1dB is 25% more output for the same power input.
Hi Saturnus.
You gain only 0,5db combined if each speaker is 0,5db more efficient I think.

ex: If you have two 90db speakers you get 93db combined, if you have two 90,5db speakers you`ll get 93,5db.

Regards,
Peter
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Old 24th June 2008, 06:45 PM   #136
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That's very possible, and in that case I get a 1dB boost just by putting the magnets together. Measurements don't lie.
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Old 24th June 2008, 09:56 PM   #137
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Quote:
Originally posted by Saturnus
That's very possible, and in that case I get a 1dB boost just by putting the magnets together. Measurements don't lie.

1db boost for free is good


Great idea to use the speaker basket as a part of the structural design. Saving weight and adding strength at the same time, and it also cancels out vibrations.
Very cool
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Old 24th June 2008, 10:55 PM   #138
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Click the image to open in full size.
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Old 26th June 2008, 03:28 AM   #139
m4gnus is offline m4gnus  Denmark
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Where can I find that Qbox system thing?? And is it important?
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Old 26th June 2008, 09:44 AM   #140
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Quote:
Originally posted by m4gnus
Where can I find that Qbox system thing?? And is it important?
Qbox is the resulting Q a system has when a driver is placed in an enclosure volume (a box) whether it's an open baffle, closed, or reflex system. You need the formulae or a speaker software to calculate it. Most free speaker design software doesn't let you adjust Q though, so professional software is needed.

Read this to understand the basics:

http://www.geocities.com/kreskovs/Box-Q.html
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