Boominator MINI (development thread)

Sure electronics makes a 3s 11.1v battery holder with over charge, under & balance protection built in for $10. Been using one for a year with no issues

My son with my guidance completed a mini boominator w the accusafe speakerkit for a school project and generally we are happy with the performance. However one of the criteria was to compete with production boomboxes like jbl etc. It seems to me that the comparable size production boomboxes have more bass and go louder. Models like the jbl boombox, aiwa , teufel, and more recent diamondboxxx M are a case in point. The site oluvsgadgets has a very nice switcher where you can compare many models using level matched binaural recordings at 1m and max volume at 5m.
I often see db measurements of these speakers peaking at over 110db. Javis boomtech on youtube has a recent loudness face off on these where he measures them. I imagine his db meter is calibrated. 
The issue with our mini is that I measured about 100db peak at 1m at max volume  with a dedicated db meter and NOT with an uncalibrated android phone which can have huge discrepancies (are iphones more precise?).
The amp is a sanwu bluetooth 7294 amp powered by 3s2p samsung batteries. I see from the specs that this amp as well as most class d amps cannot manage more than about 15W with a 12v supply. So I guess 100db is in the ballpark although I would have expected something like 104-105db reading through the mini/monacor specs. i.e. 93db from each channel at 1watt. 99 db from two channels. 109db at 10watts calculating roughly.
So how do the production boomboxes manage much higher levels? Has anyone measured their mini loudness level?


Edited by protos - 23 November 2017 at 12:28pm

Well 100 db is very loud for some people. It is loud enough for a small party in a normal room. But after that there is distortion so it is not a matter of gain. Also for me the bass is very rolled off. I spent the afternoon taking measurements freq response with audio toolz app and it seems the bass starts to roll off from about 200 hz and is already
more than 10db down at 125 hz and more than 20db at 60hz despite room boost effects. I know it is a small speaker but I was expecting a slow roll off from 90 hz or so according to specs. As it is there no lower bass and no upper bass either. I am sure production boomboxes are much better. I have the harman kardon go play in my summer house and I can say the bass performance is very good. It is the same size and costs the same as a mini build.

The SP60 has some inherent design problems including incorrect specs.   Having built all of the Boominator designs, this is clearly the poorest performing of the bunch and it had far less development than the other boominators.   It has a very thin sound that I could not eliminate even with a DSP and it all comes back to inaccurate specs from Monacor.   The NS6 design is worlds better and, for outdoor use, the full size boominator is stunning.   

How do the commercial units achieve more?   Well, they have certainly benefited from more R&D and, in some cases active filters / DSP that can extend the actual bass or implement psychoacoustic tricks that make you think there is more bass than there really is.     

Passive radiator is just a tuned port. ;). I have a Sony X33 that is also very impressive .   The progress in the last 30years is really amazing.

I measured a dozen SP60 drivers and there was significant variation (poor quality control) and the T&S parameters were quite off the spec sheet.   I don’t have the raw data at my fingertips. At the time I posted the data on the diy audio site with the same user name.

Edited by Aterren - 25 November 2017 at 8:18pm