Boominator MINI (development thread)

Message Rating: Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

   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.

Edited by Saturnus - 07 August 2018 at 1:51pm