The Boominator - another stab at the ultimate party machine - diyAudio
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Class D Switching Power Amplifiers and Power D/A conversion

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Old 29th June 2007, 10:58 PM   #1
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Default The Boominator - another stab at the ultimate party machine

First a picture of the finished beast on the scales (it weighs 26 kilos with batteries).

Click the image to open in full size.

Then a couple from the testing where you see both sides:

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The design parameters for this was to make the optimum comprimize between several things. These being:

- best possible sound quality
- loudest possible output
- longest possible battery life
- lowest weight possible
- smallest volume possible
- lowest cost possible
- simplest possible construction

Since I wanted low weight and high output I very early settled on a design with 4 10" pro woofers mounted magnet to magnet inside the cabinet to give added sensitivity and free structural strength which meant I could use thinner plywood than would normally be used for baffles. I also quickly settled on 7 layer 12 mm filmed birch plywood, both because we have a lot of it at work and because it very very rigid.

I used 4 P.Audio HP10W woofers becuase they're cheap, sounds great, and not least because they had the perfect depth for magnet to magnet mounting. For top end I used 4 MGR CH-100 piezo tweeter. Again low cost and good sound quality was the primary factors. It's not really filtered, it's got a 0.22 mH coil to flatten the peak of the woofers and filter above that point. The piezos only has 3 Watts 150 Ohm carbon resistors in series. With a 150 Ohms resistor, they sound great as long as the voltage across them is not too high.

The cabinet is built as two separate bass reflex cabinet with a battery and electronics compartment in the middle. The holes on the front are cooling and cable access, while the handles on the sides double as reflex ports.

It's designed to be used outdoors, so I chose a Qbox of 1.1 tuned at 82 Hz (my little nod towards 41Hz.com ). Trying to go belong 100 Hz in free-field is nonsense if you keep the other design parameters in mind. It's better to have a good middle bass performance to compensate for the lack of real sub-bass.

It's loud! The sensivity is about 98 db/watt because of the double woofers and the magnet to magnet construction. With the amp giving about 50 Watts total peak power output, it should be around 113db total in peaks.

The choice of amplifier was pretty obvious. I had to be a Tripath based amp because of the low cost, good sound, and long battery life. The choice fell on the excellent amp6basic kit from www.41hz.com. Here shown with and without cooling plates. (I made two beasts at the same time, one for me, and one for a friend of mine.)

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The optimize battery life I installed 4 8 Volts 250 mA solar cells from siliconsolar.com, 2 in series on either side. The battery life solely on battery is around 50 hours at maximum music power. And with reasonably sunny weather, they can probably last several months at fairly normal power levels. That remains to be tested.

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I also added a switch mode recharger from batteryspace.com, and a standard car USB power supply. The batteries are 2 standard 12 Volts 7 Ah SLA paralleled and stacked on top eachother.

Here's a few more pictures from when I put them together.

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Cheers!
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Old 30th June 2007, 11:57 AM   #2
Pano is offline Pano  United States
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Very nice! Very Pro.

So are there 2 drivers facing out the back as well as the front? You mention 4 drivers.
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Old 30th June 2007, 12:04 PM   #3
Hartono is offline Hartono  Indonesia
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Awesome party machine !!!
I like the name

Hartono
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Old 30th June 2007, 01:43 PM   #4
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Quote:
Originally posted by panomaniac
So are there 2 drivers facing out the back as well as the front? You mention 4 drivers.

That's right, the two sides are identical with two drivers facing each way. That gives an almost 360 sound.
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Old 1st July 2007, 09:32 AM   #5
Nisbeth is offline Nisbeth  Denmark
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Going to Roskilde?


/U.
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Old 1st July 2007, 10:20 AM   #6
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I like it. Wouldn't it have been better with just one pair of drivers on one side though? As you have it the drivers are just cancelling each other out in the midbass.

I'm amazed it can go for 50 hours on a charge, and months(!) with sun. That's brilliant.
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Old 1st July 2007, 12:13 PM   #7
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Ignore my bit about there being cancellation, I had not fully woken up.
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Old 2nd July 2007, 05:13 PM   #8
sts9fan is offline sts9fan  United States
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Could you explain how the solar panels are connected? Are the always charging? This is something I have been wanting to build for a long time and this thread was the nudge I needed. Could you post a simple wiring diagram to help out a terrible DIYer? Nice Job!
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Old 2nd July 2007, 07:27 PM   #9
v-bro is offline v-bro  Netherlands
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Wow, I bet it's louder than the one Pekar built!

I thoiught you were going to use other drivers, but the efficiency of this setup is probably nothing to joke about either

Keep it rocking!
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Old 4th July 2007, 06:30 AM   #10
TroelsM is offline TroelsM  Denmark
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Hej

May I ask where you bought the P.Audio HP10W's from?

Mvh TroelsM
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