prako2 wrote:Does amperage matters? I found this one https://m.skelbiu.lt/skelbimai/nauji-ir ... 80519.html and in the picture it says that it's 750 A. What does it mean? And maybe I'm enough to have 600W countinuous inverter if I'm not going to play a music with distortion and damage my speaker. But I still don't understand one thing, in Thomann description it's written that HF is 300W and LF is 1000W and the rating is 1300W and it's written on the speaker. As I understand, 300W is equivalent to 300W RMS and what is higher than that, damages the speaker (when I turn up the too much volume on the speaker and hear a distortion).
The 750A marked on that battery is the absolute maximum current that you can take from it. That sort of current demand usually only happens when you are starting your car from cold and you can ignore it for what you want to do. The more important thing to look at is the capacity which is marked as 74Ah. In perfect conditions this means that you could draw 1 amp for 74 hours or 74 amps for one hour (but in practice things will be slightly different).
Active PA speaker specifications can be rather hard to interpret as manufacturers are often rather optimistic with their power ratings. The best guide is to look at the markings next to the power connector. For the Mackie Thump 15a this shows that the power consumption is only 75W so the 1300W specification is definitely "marketing" power rather than real watts. A 150W continuous power invertor would probably work but it might be safer to go for something like 300W to give you some headroom. At 300W you would be drawing 25A out of the battery (assuming 100% efficience) so the battery that you linked to would last just under 3 hours (if it was in top condition). At 75W you would have 12 hours life.