Anyone ever run a Loudbox Mini thru an inverter/battery combo? - Page 2

dannyg1 · #16 07-30-2015, 09:29 AM

Just bought an Ashdown AA40 (an 8 lb, Class D 50w, 6.5" with a dome tweeter) and I got 3 hours and 27 minutes with the 5ah battery. The amp is only a single channel though so, if I keep it, it'll be used as an extension box.

A quick review of it: It's just acceptable for vocals (Using an impedance booster plug on an xlr and an EV ND257). At higher volumes the tweeter tends to start shrieking and the woofer/mid driver starts to break up pretty easily. Sounds very well with the guitar though. Plugging a computer in the aux and listening to music sounds pretty bad, so not a mini PA.

As directly compared to the Loudbox Mini, it has a more 'brittle' presentation and it's not as 'smooth' sounding. It has a pronounced high mid bite and breaks up in the lower mids. Less bass comes through, though it does well with what does come through. It sounds in overall fidelity, closer to the Vox Mini5 than the Loudbox Mini.

dannyg1 · #17 08-02-2015, 05:26 PM

Latest test results with the Loudbox Mini.

JonFields45(?) let me know the inverter that I had bought was less than well reviewed on Amazon and I decided to test the theory. I got a Powerbright ACS300 to see if it would perform much better and it does seem to. I hooked it up to a new SLA 12v 18AH battery, freshly charged for 48 hours (as well as upgrading the cabling of the whole system) and I got my 4 hours (and did not hit the 'low battery' alarms).

The murky part starts here. Being stuck without AC power after the first test and fearing that I'd run the battery down pretty far and having read somewhere that I could charge to 85% by plugging the battery directly into the cigarette lighter socket in my car (with the alternator running) for a 1/2 hour, I did this and got almost 5 hours the next day, but I did hit the alarms at the very end of the set.

I re-did the plug in to the lighter socket trick on the way home and when I got here, I plugged it in to the Shumacher 1.5amp charger. It's been charging now for 12 hours and it's still not green lit. I'm thinking that the cigarette lighter charging thing may not have been charging the battery after all.

If that's the case, then I got plenty of hours out of the 18ah battery. Here's to hoping I didn't hurt it.

jonfields45 · #18 08-03-2015, 06:15 AM

One last comment for anyone who has not bought an inverter. Relatively few pro sound products require a true sine wave power source. I am a retired EE and it would be expensive to produce a better sine wave without lowering efficiency. Efficiency is paramount when using the smallest possible battery (since they are heavy!). Call your equipment's support line first, before you buy anything more than a modified sine wave inverter. In general it is bottom of the line consumer stuff that MSW inverters can screw up with harmonics of the 60Hz MSW causing mischief (a classic example would be lines on the display of a low end transformerless TV or cheap digital stuff resetting itself).

dannyg1 · #19 08-03-2015, 12:00 PM

Hey Jon
My reading about inverter efficiency gave me the idea that pure sine inverters featuring a more perfect reproduction of a true sinusoidal wave were more efficient on both sides of the power equation. That is, the inverter delivers around 85~90 % of the power from the battery, if it's pure sine wave, as compared to 50~65% if it's modified sine wave, and that the powered device will convert sround 20% of its delivered power as heat from a modified sine wave inverter.

Also, from what I've read, audio equiptment is very sensitive to how it's power is delivered, making him on the low end, and breaking up in the bass if it doesn't like what it's getting. All of that led me to believe that pure sine wave inverters are the only good choice for audio applications. Is all of this not true?

Tomm Williams · #20 08-03-2015, 02:02 PM

Quote:

Originally Posted by jonfields45

One last comment for anyone who has not bought an inverter. Relatively few pro sound products require a true sine wave power source. I am a retired EE and it would be expensive to produce a better sine wave without lowering efficiency. Efficiency is paramount when using the smallest possible battery (since they are heavy!). Call your equipment's support line first, before you buy anything more than a modified sine wave inverter. In general it is bottom of the line consumer stuff that MSW inverters can screw up with harmonics of the 60Hz MSW causing mischief (a classic example would be lines on the display of a low end transformerless TV or cheap digital stuff resetting itself).

Jon that's good info but....................wouldn't it be much easier, safer (and cheaper) in the long run to just go with a PSW inverter and not need to revisit this issue everytime a new piece of equipment is acquired?

jonfields45 · #21 08-03-2015, 04:19 PM

I've never had anything I've tried not work fine with a MSW inverter. But some people report problems and I don't have the info to dispute or verify their issues. A MSW inverter is a very simple waveform that can be reproduced with relatively few on/off transistor events. A PSW requires a relatively high frequency switch running off a boost converter. More stuff running quickly means more loss, given you don't spend big money on very fast transistors with very low gate capacitance.