I see no mention of a Turtlebox. I have one (Gen 3) for my boat. It is comparable, sound wise, to the big JBL boom box 4. It is water proof and practically indestructible. And you can sync with another for stereo or just expanding soundstage.

Scratch my previous post. Received the Flex in excellent condition, but from the packaging it may have been used. 

This is an audiophile bluT enabled speakers, not toy.  No boombox either.

Phantom Ultimate 98 dB $2400

If you want the very best — something that sounds truly great, not just good — look no further than this work of art.

Pair them together for a complete stereo system; $3800 if you choose this color

18 Hz - 25 kHz (-6dB). Wow...

I have a stereo pair of Sonos Move 2s that I use. I love them. They connect wirelessly in about any way possible and pretty much disappear outside. 
 

if price was no object, Devialet Phantoms are pretty amazing for what they are.

Looks like OP asked about Bluetooth speakers to use outdoors on his property. Would $2000 Devialets that look like teapots from Goodwill fit his use case? That's for him to decide, but in case he were in the market for something sensible, the Ion Tailgater Tough that could once be had for $59.99 at Costco sounds quite good. It's a 2-way with a 6.5" woofer that actually claims 55 Hz – 15 kHz @ -3 dB; it's loud, it's not too big and not too garish-looking compared with its tailgate-party ilk, and it can be paired for stereo.

That's if you can get past its name.

Happy outdoor listening!

https://www.ionaudio.com/tailgater-tough.html