Hi @Paolo P.
Welcome to the Sonos Community!
I’m sorry to hear you are not happy with your new Arc - is it, by any chance, enclosed by your TV furniture? I’ll assume not.
TruePlay is worth trying if you have the option, but your satisfaction with the sound of your Sonos product is paramount for us. Please test playback of online music via the Sonos app (remember to turn down the volume a bit first in case it is too loud) - if this sounds louder, then it’s possible the low volume is due to the audio format being provided by the TV. Adjusting the TV’s digital audio output format to Dolby Digital would be a good test to verify this - lossless formats like Multichannel LPCM often sound much quieter than Dolby Digital. If, however, the Arc sounds quiet when playing music too, then there might have been a manufacturing issue - we’ll be happy to organise a replacement or a refund, whichever you prefer. In this instance, please get in touch with our technical support team directly.
I hope this helps.
"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein