The Boominator - another stab at the ultimate party machine

[Saturnus]

Where to get the parts I used if you live in Denmark?

HP10W - www.ljudia.se or www.intertechnik, the german site will send them to you while the swedish require you to drive to one of their stores but you can get all you need there, remember to order well in advance and have them call you when all parts are ready for pick up.

Piezos, grills, wires and accessories - www.ljudia.se or www.dlt.dk

Amp - www.41hz.com

Amp enclosure - www.brinck.dk or www.velleman.be

Batteries - www.brinck.dk or www.batteribyen.dk

Solar cells - www.siliconsolar.com

Battery charger - www.batteryspace.com or www.brinck.dk

[tfan]

Thanks.. I've just ordered two HP10W from Germany.

Would be a good time to read about building a case now. I know the principles of bass reflex case, but don't know how to measure the size of it. I guess it's something learning about how to read and understand the parameters for the driver. I'll have to Google for that one.

Yeah, tell me about it! One major mistake from last years version, was me. I got drunk and forgot all about turning of the amplifier, even though it had a beautiful "main switch" for everything inside, I didn't even tell the others to remember it. It all resulted in that we drained an entire battery in around one and a half day
I'm not going to be around the stereo all the time, so I'm currently thinking about a good way to save power, which won't be to complicated and time consuming to make. One thing is sure, I'm not going to waste power on charging the laptop battery (might be taking it out to be sure)

Actually I wasn't aware that I car batteries would be so bad. I could probably go with marine batteries, but as I already have three car batteries, I think I'm going to stick with them (got two of them for free). I'm going to buy some used ones and connect them all in a parallel connection in the bottom, so I don't have to think about them at all (hopefully).

As for design, I think the only thing I'm going to copy is the design of your speaker cases. Making a copy of your Boominator would be a boring project for me, especially when this is the third version of the stereo. I'm also getting help from people from my camp, so I think we'll figure something out that matches our theme. I don't think my mobile coffee machine would not fit in very well in yours

I've been on Roskilde for five years, but never seen your stereo. Hope I'll trip over it this year (not literally :P)

[tfan]

Oh, btw, I found a freeware program (WinISD) which measured the whole thing for me. Very recommendable.

I used the numbers from the data sheet, so I hope it's correct.

Does this sound reasonable (bass reflex design):

Box size : 53,8 l
Tuning frequency : 48,42 Hz
Vent : 1 vent(s)
0,116 m length for each
0,102 m round

Dimensions of the box (cube):

(Board thickness: 2,1cm)

Width: 42,5cm
Height: 65,4cm
Depth: 27,2cm

[123gute-laune]

Hi, first of all a big "thank you" to Saturnus for starting this thread, it was really inspiring in many ways; very impressive craftsmanship by him and all the others. Thanks to all in this thread who did a great job in opening my eyes for a lot of things I forgot to consider when I started to build my boombox some time ago.

Currently my setup consist of a pair of JBL Control Ones loudspeakers, mounted in a wooden frame, driven by an Tripath TA1101B-Amp (2x10W@8 Ohm); I never thought about things like speaker sensitivity when I built this thing. Not necessary to mention that I am not satisfied with the volume this system outputs (I would not have searched for a thread like this one, would I? ;-) ).

So with the countless great ideas this thread has given me I am going to take the next step and try a complete redesign. A couple of questions remains though, that is why I joined the forum.

First, here are some assumptions I am making, I would be happy if you tell me wether I am right or wrong:

A#1: Paralleling 2 speakers halves the overall impedance thus doubling overall current/output at a fixed voltage, so in a simplified view connecting 2x2 paralleled speakers to a stereo amp doubles its output power compared to 2x1 speaker (I looked here and here).

A#2: Clamping together 2 correctly poled paralleled drivers back-to-back/coil-to-coil gives an extra gain of about 1 dB because the magnetic efficiency is tweaked.

A#3: To fully utilize the effect of A#2 it is necessery to place the speaker system in the middle of the audience. If the audience is placed in front of the speaker system, half of the output is lost "behind" the speaker system, so in this second scenario one would achieve a bigger gain by placing all of the drivers on one side of the speaker.

So at the moment I see 2 upgrade paths emerging, more or less defined by the choice of the amp, my premise having a little more emphasis on carriability than Saturnus' solution (after all my soundsystem is supposed to fit in a large backpack together with the usual barbecue utensils):

1) a mono-design with 41hz.com's AMP11-LV (1x100W, 24V)
1.1) reuse of the existing JBL Control Ones, paralleled, fully aware now of their inferior sensitivity of ca. 87 dB.
1.2) with 1 of the P.Audio HP10W and 1 piezo tweeter recommended by the OP
1.3) with 2 6" *paralleled* woofers and 1 piezo tweeter, all front mounted.
1.4) with 2 6" *paralleled* woofers and 1 piezo tweeter, woofers back-to-back.

2) a stereo-design with 41hz.com's AMP6-BASIC (2x25W, 12V)
2.1) with 2 6" woofers and 2 piezo tweeters, all front mounted.
2.2) with 2x2 6" woofers, each 2 of them *paralleled* and 2 piezo tweeters, all front mounted.
2.3) with 2x2 6" woofers, each 2 of them *paralleled* and 2 piezo tweeters, woofers back-to-back.

I am considering (for the sake of simplicity) a closed enclosure.

Ordering the different paths above regarding price is easy (from "cheap" to "expensive"):

[1.1] < [1.2] < [1.3,1.4] < [2.1] < [2.2,2.3]

But how would you order it regarding sound volume (from "silent" to "loud"), especially considering assumption A#3 (i.e. would [1.3] be *a lot* louder than [1.4])?

[tsnell]

Hi Everybody,

I hope the new year finds you all well. Sorry for the delay in getting the pics up too! These are only the ones I have on my computer at the moment but there’ll be more to come! And once again thanks to everybody for the help getting this beast going before Christmas, I cannot express my gratitude enough!

The amp9 chip was dead but the Boominator was up and running on the amp6B. We got rain and miserable weather almost the whole time but the batteries lasted without faltering. I ended up using 2 x 7Ah gel cells in parallel (it is a heavy beast). When cranked up to full volume on the iPod it was pretty freakin’ loud but there was nasty sounding distortion with the iPod volume up this high (classic 6g 120gb). I ordered a new amp9b kit and had it running on the amp9 (12V) for Australia day (and the triple j hottest 100) last weekend! First impressions… LOUD! I also used my Headamp Pico to drive the amp9 and it made it louder again (over the iPod), plus got rid of much of the distortion at high volume. Very, very impressed and absolutely stoked with my new toy. Nice work on this one Saturnus! But you should have warned me, I think I have caught the bug, next upgrade…. 24V.

[tsnell]

I forgot that I hadn’t given any real updates on the finished box (and I stuffed up the battery I stated above, typo, still thinking of the original (true?) Boominator) so some of the build details are:
• 2x18Ah SLA batteries connected in parallel
• 20W solar panel
• Chargers for iPod and iRiver built in plus accessories outlet
• Both Amp6 and Amp9 are mounted in Soanar aluminium enclosures as small as I was able to fit them in (actually had to grind out corners of amp9 box to get it to fit) and use case as a heat sink. I expect that if I go to 24V I may need to rethink the amp9 arrangement to add better heatsinking but at the moment it seems to get warm but not hot to touch
• Battery life seems practically infinite with amp6, have not had a chance to really give it a run with amp9 but got a whole day with no problems (charged batteries)
• Crossover/speaker wiring – I tried fiddling around with the few different options talked about. With amp6 it was 2 woofers in series with each other, in parallel with 2 sets of 2 tweeters (make sense? Maybe I should draw it). With the amp9 I tried setting it up with woofers on one output and tweeters off another, using jaycar fader. Sounded good but the tweeters were a bit “hissy”. Currently it is set up as per the saturnus style sketch I did with a 68 ohm resistor. This sounds good but the tweeters sound a bit dead, they are still there but only noticeable with cymbal shimmer type sounds when you stick your head down to listen. I will need to work on a happy compromise here.

Sound and general comments:
• Volume is seriously impressive
• Sound quality is very good for the volume (But the pre-amp device is important!)
• Bass is good, very passable, much better to the ear than the curves had led me to believe it would be. Daft Punk Alive was one test album I was using when trialling different setups. On several occasions my girlfriend came out to the shed to tell me to knock it off because “It’s 11 at night and all I can hear is thud thud thud in the house, shut it off before the neighbours get angry!”. I guess that is as a good a bass-stamp’o’approval as any! The woofers move some serious air out the ports too.
• It is heavy and I’m sure that one day when I’m an old man with back problems I’m going to look back and curse this thing
• Is exactly one corolla boot width wide (maybe a few mm to spare), very lucky, you’d think I would have checked that before I built it though! haha

Um, not sure what else to mention… Will definitely keep the thread posted with any new developments though!

[Saturnus]

Thank you very much for the appreciation. And I'm thrilled that you got it up and running without too many hick ups.

Really great looking build as well but I take you have painted it later? As far as I can tell you didn't schampfer the woofer cut-outs, if it's possible I'd recoomend doing it. Your cabinet is longer than mine, I guess to make room for those massive batteries you use. Those extra 6-7 kilos would off course bring it up over 30 kilos in total weight. Something to build upper body strength with.

You can try with a little lower resistor value on the piezos and see if you like it but it will not give you more volume, it will only shift the x-over frequency downwards. As I already stated, a resistor in series with a piezo works as a highpass filter, so the capacitance of the piezo and the resistor value works precisely like an ordinary highpass filter would, where it's just the resistance (impedance) of the tweeter and capacitor value that governs the filter frequency. I like that the piezos aren't terribly audible as I really don't like the aggresive sound they can make but tamed they can sound pretty ok.

It is very important to change the feedback resistor in the amp6b to at least 82K or 100K when running off an iPod because depending on version they have very low to ultra low head phone output, and will distort badly, and you also find out, if pressed too hard. With an amp9b, a preamp is basically mandatory.

Yeah, sorry about not mentioning that they are a totally and utterly addictive toy. 24V ... Go for it

[tsnell]

Hey Saturnus,

Thanks! Will definitely try a lower resistor value when I get a bit of time. The box in the photos is finished with 3 coats of poly urethane so no paint after that. The woofer cut outs are chamfered with a 10mm round over router bit. Note to all, the plunge depth with this bit and 12mm ply pushes the roller bearing just past the bottom of the timber. Result = one ruined front baffle. Lesson learned = use a backing sheet of ply with a matching circle cut out. This was one of the few (few too many!) hiccups along the way. The ports and breather holes are all chamfered with a 5mm round over bit too.

[v-bro]

Great looking Boominator Tsnell!

Congratulations!!

So any riots started with the neighbours or are they cool with it?

[aphelion]

Hey guys,

I'm brand-new to this forum. Everyone here seems really helpful and cool, so I figured I'd try to get a little help from you all.

Thanks a ton to Saturnus for sharing his ideas and knowledge in this thread (I just finished reading all 11 pages). I have been looking to make something like this for a long time. My buddy built the "Podzuma" about a year ago, and was reasonably happy with it, but it ended up being too heavy (weighed around 50 lbs/22kg) to be truly portable. The Boominator is a superior design, but at 60 lbs/26kg, is not light enough to carry around for more than a few minutes.

My goals for the Boominator Mini are:
[list=1][*]Is light enough and comfortable enough to carry around on a shoulder strap, slung-over neck like a messenger bag - like this, but less queer looking. [*]Puts out respectable amount of midbass[*]Costs less than $500/4100kr.[/list=1]

I plan on making these changes to save weight over the original Boominator design:
[list=1][*]No solar panel - this is excess weight that I cannot afford to have. (-3 lbs/1.3kg)[*]8" woofers instead of 10" woofers - 12in x 12in x 36in (30cm x 30cm x 90cm) is too bulky to carry on shoulder, and requires too much weight in speaker and enclosure. I am trying to find speakers that are 5lb/2.2kg or less in weight (-10lbs/4.4kg). [*]Smaller enclosure - Mini Boominator will be approximately 9in x 9in x 27in (23cm x 23cm x 70cm), which will also save weight (-4.6lb/2.2kg assuming original Boominator plywood weighs 11lb/5kg)[*]Li-Ion battery instead of SLA battery (-10lb/4.5kg)[/list=1]

Original weight:

• 31lb/14kg woofers
• 11lb/5kg batteries
• 15lb/7kg everything else
• ------------------
• 57lbs/26kg total

Mini weight:

• 20lb/9kg woofers
• 1.3lb/.6kg batteries
• 7.4lb/3.4kg everything else
• ------------------
• 28.7lb/13kg total

Ideally, I would like for the Mini Boominator to be closer to 25lb/9kg. If I can save a little more weight on speakers and enclosure material, then I could possibly hit this goal.

Questions/Problems I have:
[list=1][*]Trying to find an 8" woofer as good as the HP-10W is proving difficult. Anyone have any recommendations? Here are a few I have found, but each has its problems: Dayton Series II, Vifa P21WO-20, Aurum Cantus[*]Saturnus:
The CAD files you posted are not available. Can you post them somewhere else please?[/list=1]