Please note. This is a development thread that is expected to be complete in Autumn 2018.

Please read all responses to make sure you have noted all changes to the design before beginning construction.

Please note: the Aura NS6 this build was originally based on have sold out and will not be produced anymore. A new design based on Dayton Audio drivers and advanced DSP amplifiers is in the process of being completed during Autumn 2018.

As some of you might have noticed I've finally decided to expand on my original Boominator design with a few extra models. This is based on the many requests to make something lighter, smaller, larger and/or more versatile. So I'll make them all.

Firstly, I'd strongly emphasize that the original Boominator design should still be your preferred first choice for a DIY build. These extra versions just expands on the concept. 

There'll be a true mark II version which has a new flexible bracing structures which allows to incorporate almost any driver with suitable parameters into the Boominator design. The main result of this will be a LITE version with neodynium based drivers (Eminence Basslite S1020) making it possible to build a Boominator that weighs half the original at 10kg excluding batteries (the original weighs 19kg excluding batteries).

There'll also be a MEGA version with 4x 15" pro woofers (the PD.153ER to be exact) and a powerful Selenium DT220TI compression drivers combined with a compact bi-radial CD horn (the Eminence APT200S horn guide). It'll be massive mainly in terms of weight (estimated 70kg) as it will still be impressively compact and will sports 2x 300W amp for the woofers.

Back on topic though. The MINI. One of the most asked for designs was a cheaper and smaller version. In effect I tried to advice people to just build half a Boominator. But although good, it's not really what I wanted to offer as it's not a true bipolar speaker which is an absolute necessity for an outdoors speaker of this kind to sound good. I also wanted something that could be used indoors which ruled out the overtuned boombox BR tuning that I worked and experimented so long to perfect. One thing remains though: the higher than standard Q tuning at Q=1.207. With the ultra cheap Aura NS6 drivers this gives the same warm sound with exceptional vocal clarity as the original Boominator.

Aura NS6 is available from PE and Madisound. Both unfortunately US dealers but with a price that low and freight forwarder service used instead of direct delivery. It's still a very good deal.

To complement the Aura NS6, I've chosen a old favorite of ultra compact designs with drivers that go up to about 4.5-5Khz, the Dayton ND16FA-6. Available from PE and Europe-Audio. It's small, it's cheap, and crossed in above 4Khz it does it's job very well. It also have the desired very high dispersion.

Filter is a hybrid 2.-order with L-R LP and B-W HP at 4.6Khz. No extra attenuation or compensation circuits necessary. This is due to an L-R filter being 6dB down at x-o and a B-W being 3dB down at x-o. But a pure b-W also has a 1dB lift at x-o, the hybrid takes care of that while at the same time compensation for the 3dB spike in the woofers FR between 4Khz and 5Khz. Remember to invert phase on the tweeters. Use cheap as dirt components except the cap in series with the tweeters negative pole (it's inverted, remember) which should be at least an MKP type.

Amp is ideally the amp32 from 41hz but it might be a bit difficult to solder as it's really tiny and uses SMD components through out. Other than that only a "9800mah" li-ion battery, a recessed dish, grills, some cables bits, and some connectors are needed. The recessed dish functions as cooling plate for the amp as well the point where the connectors are mounted..

Not sure what other choices there are for amps but the TA2024 is generally ruled out as that doesn't work too well with 4 ohms loads that dips to 3.2 ohm. Also, it's a waste to put a TK2050 based amp in it as the drivers aren't really capable of handling that running 24V on full tilt for very long, as well as you'd need 10(!) times the battery capacity to get the same playing time. And a TK2050 uses too much power running 12V compared to a TA2020/TA2021 based amp.

If anyone got suggestions for an amp. I'd like to hear it. Though any ready built amp in a cabinet you can rule out right away as that will take up too much internal volume. It must be a bare bones circuit board.

Cabinet design will be up over the holidays but dimensions are 180x180x720mm built from 9mm plywood. A router and knowledge of how to use it is an absolute necessary tool in order to build this speaker.

Zuk4wd wrote: why is the back to back design ? 360 degree sound seems not something that i would want.

I don't want to start with Adam and Eve of simple acoustics again. It's primarily an efficiency issue. In a bipolar design the bass output from the speaker on the "back" augments the output from the "front" with 6dB under the summing frequency. In the Boominator it's at 384Hz.

In principle you could just let the drivers on the "back" play bass, and nothing else. But so much would be lost. You cannot really comprehend why a bipolar design with 360 sound is so vastly preferable  for this type of speaker until you hear it. No one who has ever heard it has said: "Great, but could I just get the sound only from the front instead". No, they all say: "Great, can I get the same sound at home if I use bipolar speakers there as well?"

roubi wrote: Maybe I'm gonna say something stupid but why not keeping the Amp6 in replacement of the Amp32. It is easier to solder !

Certainly also an option. And it would fit, so no problems there.

I apologize for the delay. The first two tries had to be scrapped. The originally planned one simulated fine but wasn't DIY friendly enough in that it relied on some very fancy routing. The second try where the center brace was scrapped didn't simulate to well as there'd be too much vibration in the cabinet (power lost and different effective tuning due to lower Ql value).

I think I have solved most problems now, and will simulate it. It'll be slightly larger at 200x200x700mm (length is reduced though) but will be much easier to build and have a central compartment for electronics just as the original Boominator. And that'll be the same 66mm width as well so a 12v 7ah standard SLA can be used instead of it having to be a li-ion battery. This also means you can use any amp you like as getting sufficient cooling is no longer an issue either.

I should have it ready shortly (though not today). 

I'll finish this one first before starting on the MEGA but there's at least 2 versions possible as I see it right now. The ultimate in sound quality one with pd.153.er (4 ohms) drivers as originally intended but Eminence Kappalite 3015 will also work at a lower price and lower total weight. Perfect for a "light mega". It'll not go as deep (it will be 95% equal to the Boominator in output just with +6dB in sensitivity) or have the same sound quality as with the pd.153.er drivers though but you also don't have to have minimum 6 amp channels (8 preferred) and a digital dsp like mini-dsp to run it effectively with the Kappalites. You could in principle get by with a stereo amp and passive crossover, although I'd highly recommend a 4 channel amp and active cross-over.

And, yes, I'll make a separate thread for that one.

Drawing completed. Please read the comment field.

It's basically a back to basics Boominator design just scaled down.

http://sketchup.google.com/3dwarehouse/details?mid=965927e4830845c72ef85ac2733ed8e5" rel="nofollow - http://sketchup.google.com/3dwarehouse/details?mid=965927e4830845c72ef85ac2733ed8e5

Phaedras wrote: I'm likely to do one, do you have more info on the filter Saturnus? The impedance of the woofers seem to be around 15 ohm at the crossover frequency.. What impedance did you use to calculate the filter?

8 ohm (2 in parallel) and 4 ohm for the tweeter which is half the impedance at x-o for one tweeter.

Yes. I'll post a schematics. However, it is likely that components needs slight tweaking in values after building and testing, so any schematics posted now will have to be taken with a grain of salt as it might not be perfectly adjusted from the start. I doubt many will notice the difference though.

Edd Jordan wrote: http://www.ebay.co.uk/itm/LithiumFerrumPhosphate-LiFePo4-cell-aluminiumCasing-8Ah-/290582322953#vi-content" rel="nofollow - http://www.ebay.co.uk/itm/LithiumFerrumPhosphate-LiFePo4-cell-aluminiumCasing-8Ah-/290582322953#vi-content These look cheap (ish)

I think I saw a LiFePO4  in a standard 12V 7Ah package with built-in BMS for as low as $60 excluding freight recently.

Pepto wrote: Is this a terrible idea?

Yes. I think it is but I can't stop you. Just note that you have to dampen the piezoes by several dB. (A series resistor does not dampen a piezo).

Btw, I just noticed that Intertechnik also has the Dayton tweeters in stock at a good price (€10 each) which is a good deal cheaper than buying them in the States when custom fees and VAT is considered.

http://https://www.intertechnik.de/Shop/Lautsprecher/Dayton/Dayton-Hochtoener/_70303_H28-ND16FA-6_1768,de,7054,53103" rel="nofollow - http://https://www.intertechnik.de/Shop/Lautsprecher/Dayton/Dayton-Hochtoener/_70303_H28-ND16FA-6_1768,de,7054,53103

Appearantly Loudspeakershop has them even cheaper at €8½ each. That's cheaper than PE even in retail.

http://lautsprechershop.de/index_hifi_en.htm?lautsprechershop.de/hifi/dayton_en.htm" rel="nofollow - http://lautsprechershop.de/index_hifi_en.htm?lautsprechershop.de/hifi/dayton_en.htm

0.56mH inductor should be below 0.4 Ohm series resistance.
5.60uF capacitor should be MKP or MKT type

Edd Jordan wrote: How do you sum your signal to get mono? or is the mini run in stereo and this is just one channel?

The latter.

markg wrote: Has anyone built a boominator mini yet?   I just ordered the components today. I will use it outdoors but also in the hockey arena locker room. Any changes to the design advised for use indoors?

Not to my knowledge but 4-5 people are in the process of doing so. No change for indoors use. It's designed to be usable both indoors and outdoors. 

You can get tweeters, coils, capacitors etc from  http://www.intertechnik.com/" rel="nofollow - http://www.intertechnik.com/

Just use a MKT cap. They're fairly cheap.

According to CATIA simulations there's not much reason for using 12mm over 9mm with the suggested bracing structure. However, I suppose it wouldn't hurt to make the baffles 12mm.

Just make sure that everything is working before closing the box the last time. Triple check everything. There should be not reliability issues at all if everything is connected and soldered together correctly. It'll easily last years and years.

The weak point is the electronics compartment in the middle. Make sure you can access that and change the battery or amp if you're unlucky. I would not worry at all about the speakers.

One of the first prototypes of the Boominator still works perfectly, and is touring festivals, brought to beach parties, bbqs, company events etc every year, and have been so since 2005. Sure it's looks battered but it still works fine.

You can spray the cone very lightly with impregnating silicone for added resistance to the elements. However, it is far better just to avoid water/sand coming into contact with the driver in the first place. You can do that by using a grill, either a fine mesh grill which can be difficult to find in the right size, but I also very much favour using a standard punched grill where you first take the rubber ring off, spray the top side with contact glue, glue on a speaker cloth of your liking, cut away excess, and lastly put the rubber ring back on. Remember, the grill goes on the inside, between the woofer and the baffle.

While we're on the subject of the baffle. If you have the wood lying around, you can make the baffles of 12mm instead of 9mm without changing the outside dimensions. The result is a slightly improved stiffness, slightly higher weight, but most importantly it will make the drivers fit without any gaps between the magnet and the center brace. The grill with rubber ring will probably be slightly more than 1mm, usually about 1.2mm, but it easily compresses. It will not have any significant effect on tuning due to smaller cabinet volume (it's less than 1/3 of a liter smaller).

Baffles = 2x 12mm, brace = 9mm, grills with rubber ring = 2x 1mm, woofers 2x 82.5mm. Total = 200mm.

Please note. I think I forgot to mention this before but I advise the cabinet to stuffed medium hard with acoustic wool.

I didn't use the amp6 because the original idea called for an fully closed enclosure where all drivers shared the same volume. With the change to a design with a central electronic enclosure that is no longer applicable. Adjust the size of the electronic compartment as you see fit to suit whatever battery and amplifier you choose. Remember to keep the speaker cabinet volume roughly the same size so adjust overall length accordingly.

The 9800mah li-ion is one similar to this  http://www.aliexpress.com/store/product/New-DC-12V-Portable-9800mAh-Li-ion-Super-Rechargeable-li-on-Battery-Pack-for-wireless-transmitter/803611_564472693.html" rel="nofollow - http://www.aliexpress.com/store/product/New-DC-12V-Portable-9800mAh-Li-ion-Super-Rechargeable-li-on-Battery-Pack-for-wireless-transmitter/803611_564472693.html . It's 3 cell, so nominal voltage is between 10.8V and 11.4V. That works fine with any TA2020, TA2021, and (to some degree) TA2024 amp. The lower voltage of a 3-cell battery pack is actually a blessing in disguise as it makes a TA2024 amp capable of running a 4 ohms load which it would not do optimally on 12V or higher voltage. But you can use whatever battery you like. The electronic compartment is now sized so that it can host a standard 12V 7Ah SLA.

The amp I currently favour using for my own build is this  http://www.ebay.com/itm/TA2024-MKV-Bluetooth-Tripath-amplifier-2X-15-Watts-12V-fully-finished-/251221801085?pt=UK_AudioTVElectronics_HomeAudioHiFi_Amplifiers&hash=item3a7dfc787d" rel="nofollow - http://www.ebay.com/itm/TA2024-MKV-Bluetooth-Tripath-amplifier-2X-15-Watts-12V-fully-finished-/251221801085?pt=UK_AudioTVElectronics_HomeAudioHiFi_Amplifiers&hash=item3a7dfc787d . Combined with the battery above and laid on it's side I can cut 34mm of the width of the electronics compartment making the overall length 666mm. Please note that for that to fit, you need to replace the large input caps on that amp to something more suited for a class D amplifiers, like standard small WIMA or EPCOS MKP types (the large caps are passive loudspeaker filter caps, they're not suited for places where they can and will receive large amount of RF noise). I favour this amp primarily because of the built-in bluetooth audio module which naturally isn't terribly good for critical listening like all bluetooth audio recievers but for use as a portable audio player, it's an absolute gem as you can just stream the music directly from you phone instead of having to worry about cables.

It's not that relevant as you can't actually order them anymore.

The new international regulations prohibits the transport of lipo batteries of this size unless they are UN38.3 approved. Such an approval costs money, and none of those low-cost models we have usually bought will pass anyways so it's a dead-end I'm afraid.

Good thing I designed it to be able to hold a standard SLA size so I can get a proper lifepo4 battery instead.

Depends on whether you plan to do some tweaking of the filter as the design matures. Or if you trust my calculations and experience to have nailed the optimum filter.

I did earlier in this this thread warn that the filter may be tweaked slightly but in any case I expect it to be very minor tweaks, and that the filter, as is, will do it's job well enough for most people not to notice any difference at all.

The Boominator MINI is relatively tiny compared to the Boominator. 5 times smaller to be exact.

The recommended amps runs 12V only. Naturally one could use an amp with which takes higher voltages but I'd recommend against it. If you do, you must insert a higher order high pass sub cut filter to ensure the driver excursion limits are not exceeded.

As for choosing battery, I strongly recommend using a lifepo4 battery if you can under any circumstance afford it.

Larzman wrote: I'm tempted to order this and tear it apart to see what the batteries are, hoping it has 12V, but I doubt it. probably a pair of 3.7V LiPo's.

No point. Weight is 450g. That means you already know the maximum capacity it could have is far far less than what is advertised.

Let's assume the battery cells is 2/3rds of that weight. Li-Po energy density is on average 165Wh/kg for the actual battery without any electronics and packaging. That's means the maximum capacity it could have is 50Wh. Divide that with 3.7V for nominal cell voltage, and you end up with 13380mAh capacity. It's probably not even close to that in reality though.

well my amp arrived today so managed a trial fit, mostly to make sure that all the bits fit.

So far so good , I still have a fair bit of thought to go into how to package the electronics.

 I am not really going for a festival sound-system but something that will see slightly lighter duties, therefore I don’t intend to fit grills to the drivers. I am really happy with the quality of finish I have got so far, the baffles paint job is gorgeous in direct sunshine (ford electric orange)

Anyway onto the pics

Looks great. Gorgeous even.

Although I still think the 12mm plywood you have use may be a bit too think for this build but I don't see it have a negative effect, so why not?

Are the drivers excellent quality? Especially considering their price?

Those blue caps are huge  

Larzman wrote: maybe this battery pack will work, 12V 8000mAH looks pretty good, with 1 year warranty & free shipping, $28.

You can try and order it. I think it's pretty certain that you after a week or two will get a notice saying they cannot ship it to you, and you get your money back.

slaz wrote: 100Wh is mentioned as a maximum capacity - so 6800mAh/12V scrapes insides that anyway. Just looked at my laptop's batteries (one original Asus branded, one 3rd party cheapie), and neither have any UN-xxxx certifications printed on em ...... so will THOSE be banned ?

Yup. 100Wh max for a separate battery.

Don't need to. The restrictions regards separate batteries. Not ones that are in an electronic device (as long as it's not over 100Wh max).

Above 100Wh max. You need the UN certification.

enal wrote: Point taken!  I think I will maybe save the two ClassDAudio Mini Amps that I have for full size Boominators instead since they have qualities that will benefit something large.   Any recommended Mini Boominator amps that are also available in the USA or is everyone just getting them from China?  I see a lot of people in forums talking about the little Dayton Audio DTA-2 Amp that's built on the TA2024 and just wondered what the past experiences were from anyone here?

Actually the ClassDaudio Mini would be excellent here. On a battery it'd have the same output as any other class D amp on the same battery (unless it's single ended and not BLT but I doubt that). Not sure if it can handle stereo 4 ohm load at 12V though. You need to ask classDaudio about that.