Super sound from a portable speaker! Of course, I bought a second one and the performance went to the top. It's powerful, but not for outdoor parties. It's perfect for indoors. Nice design and materials. Quite heavy. The price is very good compared to the quality and in relation to the competition.

In the +

Design
Sound quality/clarity
Bass
Can be connected to a second one for even better results
Build quality
Good and immediate Bluetooth
Even better performance when plugged in

In the -

The battery is not suitable for all-day trips, you will need a power bank (at least 55000 milliampere) with a 19V adapter (waiting for it to arrive and will update).
Today it lasted only 1.5 hours at medium to high volume with the Bass booster app enabled.
I'm sorry to disappoint you, but it is more suitable for indoor use. The bass is significantly lost in outdoor spaces, unless you find a corner and place it there to create good resonance. Together with the "Bass booster" app, it works wonders.
If you want to have an outdoor party, you will need a power outlet because if it is not connected and playing on battery, the sound appears a bit low. You would definitely want something more (although it is still satisfactory, depending on your preferences and of course the noise level where you will be).
Its size is suitable for transportation by car if you want to be comfortable.
I'm not saying it can't fit in a backpack, but it will take up almost all the space and it is heavy. I was torn between the JBL Xtreme and the Go + Play and I sat and thought about what to sacrifice...
The JBL Xtreme has slightly worse sound quality but is a much more portable device with a better battery.
The Go + Play has crystal clear sound but is larger and has a slightly worse battery.
And since I have a car (although I use my bike a lot), I chose this one...
Indoors, the sound and bass really make everything inside and outside the cabinets vibrate.
Together with the Bass booster app (which surprisingly does not negatively affect the sound quality at all, only at maximum volume where the bass is slightly lost, but I don't think there is a speaker for €300 that does not distort the bass at high volume), I believe this little thing will satisfy even the most demanding.

Update 14/02/2019
With the power bank (it says 80000 milliampere but probably around 45000 in reality), it lasts another two hours.
So far, very satisfied.
It has a very nice crystal clear sound and bass.

Update 01/01/2022
The batteries need to be replaced as it only lasts about half an hour if it is not plugged in.
I consider it reasonable since it has been used for several years and I constantly use it at home and sometimes outside.
Everything else is fine.
No membranes have torn or anything broken... Its quality remains excellent! Everything is good!

Guys, I would give up to the last minute for this speaker, it is the best in terms of sound, bass, and weight (okay, it's not light but okay, we can't have it all). Crystal clear and clean sound, perfect for your summer vacation with your friends, with 2 of these, the deal is done. I highly recommend it, it surpasses any JBL, of course, it's a bit expensive but it's worth it, no one who buys it will be disappointed.

The speaker is the best. Bass intensity and crystal clear sound. It truly covers the whole house in terms of sound.

Very good sound, especially with two, you don't need an extra sound system at home or in an outdoor space.
Especially for vacations, it is perfect.
The best sound!!!!