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).

[IMGDEAD]http://img340.imageshack.us/img340/8915/dsc00019iv2.jpg[/IMGDEAD]

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

[IMGDEAD]http://img522.imageshack.us/img522/6240/dsc00016od6.jpg[/IMGDEAD]

[IMGDEAD]http://img522.imageshack.us/img522/3201/dsc00017cq8.jpg[/IMGDEAD]

[IMGDEAD]http://img412.imageshack.us/img412/350/dsc00018wy5.jpg[/IMGDEAD]

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.)

[IMGDEAD]http://img528.imageshack.us/img528/5544/dsc00012bw4.jpg[/IMGDEAD]

[IMGDEAD]http://img528.imageshack.us/img528/8369/dsc00013nu9.jpg[/IMGDEAD]

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.

[IMGDEAD]http://img442.imageshack.us/img442/8814/dsc00010jj7.jpg[/IMGDEAD]

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.

[IMGDEAD]http://img517.imageshack.us/img517/8674/dsc00014qk5.jpg[/IMGDEAD]

[IMGDEAD]http://img442.imageshack.us/img442/6480/dsc00015ga8.jpg[/IMGDEAD]

Cheers! :D
 

sts9fan

Member
2006-04-26 5:50 pm
MA
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!
 
Back from field-testing at Roskilde Festival which was the rainiest Roskilde ever! We got 100mm of rain in 4 days which made the mud ankle deep most places and knee deep some places.

It also meant that I didn't get much power from the solar cells but the batteries did last from Saturday evening until Friday morning playing 12-18 hours a day before needing recharging, so I think it proves that even if we had very little sun the solar cells did work.

The best of it was the literally hundreds of people commenting that it was the best sounding boombox ever. Rock solid bass. People where amazed to hear that it didn't any play subbass at all, it really sounds like it does. Neutral and natural midrange with good focus on both foreground and background details, and not least very natural voices. Suprisingly well rounded top end with only a miniscule of "piezo"-sound.

Also the front and back firing configuration surprised many people, they where walking past nodding their heads, and then when where past you could see them suddenly stopping up as if in confusion why the sound hadn't changed. Most turned around for a second look, and many just had to ask where the hell I bought it. :D

It still works, btw. I'll probably try to sell this one after a full check up and some minor tweaks, and make an even more crazy version next year with direct methanol fuel cells from ird.dk

Nisbeth said:
Going to Roskilde? :D :smash:

YEAH. :D

I'm a surviver of Roskilde '07 but by God didn't I have times when I thought enough was enough.


sts9fan said:
Could you explain how the solar panels are connected? Are the always charging? Nice Job!

Since the total output of the solar is 8 Watts at best compared to the 168 Watts in the battery pack, the solar cells can easily be connected all the time, without damaging the batteries. Then it can also pump in every bit of solar power they recieve into the system.

The connection is pretty simple. The two solar panels on each side is connected in series with a diode so the batteries doesn't into the solar cells. Each solar panel has clearly marked solder points on the back. A schottky diode could be used but it's not critical. Then each pair is connected into a central plus and ground point that connects all the power.

The reason for seperating the two solar panel sets on each end is because people tend to sit on the boombox while it's playing and when placed like this there's a bigger chance that at least one of the sets will work.

And thanks. :)


v-bro said:
Wow, I bet it's louder than the one Pekar built! :bigeyes:

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

It actually play so loud that you can't really sit next to it when it's playing at maximum volume, you have to move away a couple of meters. Then again, the sound quality is also best if you do exactly that since that gives you the most well distributed sound from the tweeters.

The other drivers I've been raving about is for next years version. ;)

TroelsM said:
Hej

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

Hej. It's tricky here in Denmark since the Danish distributer of P.Audio dltaps.dk doesn't have them in stock, and is unwilling to order any unless you buy at least 10 pieces! The good side is that can order them in Sweden at ljudia.se or in Germany at intertechnik.de at almost half the Danish retail price. Then you only have to either drive to get them or know somebody that is willing to send them to you.
 
panomaniac said:
FYI, here is the spec sheet for the 10" P.Audio driver.
http://www.paacoustic.com/pdf/IMF-SERIES/HP-10W-10T.pdf

Oh, I forgot to mention that though the current specs of the P.Audio driver is the same the picture is an older version. The current version doesn't have a logo, and it has a smaller fine mesh dust cap that allows air to flow through it.
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
Hey Saturnus

I saw your Boominator today in commerical form. :)

[IMGDEAD]http://www.harmankardon.com/images/product_large/HKGOPLAYBLK.jpg[/IMGDEAD]

It's an iPod boom box by Harmon Kardon. Looks as cool in person as in the photo. Very sturdy with clean lines. It is symetrical, looks the same front and back. Two speakers on each side. iPod dock on the top. Aux connections along the bottom. Claims to have "Digital Amplification."

Did not get to hear it play, no batteries, no iPod. But the basic idea is there. It's a way cool looking unit. So it seems you are in good company. But yours is BIGGER!
 
Actually it looks like a cross between pekar's solar powered boombox and mine. I'm thinking about the centerhandle here.

But yeah, they forget the solar cells. And also with the slanted fronts I doubt they used one of main aspects of my boombox which is the magnet-to-magnet mounted bipolar speakers. Though just going bipolar in a boombox has some significant advantages of it's own, mainly that when used outdoors the "back"-mounted speakers will augment the bass response of the "front"-mounted speaker, and when used indoors they will augment the mid-high response as well, resulting in somewhat flat frequency response regardless of being used indoors or outdoors.