When Bose had their speakers properly working, configured and setup by Bose on the parks themselves. They sounded incredible, truly great audio.
I suspect the Bose left on park now, like everything else, have been tinkered and messed with over the years, adjusted / swapped the amplifiers and messed with the processing. Which leads to a very different sound than originally intended and what they are capable of. Plus, no doubt some of them are very worn by now. Enduring the British weather, probably driven too hard at times and just general wear and tear over what would be hundreds of thousands of hours of use at this point. The fact some are still going, outdoors and after two or more decades, is testament to their quality.
Ohm, the speaker of choice nowadays, work pretty well I think. Their audio engineers are not quite upto scratch with Bose's decades and decades of experience though.
I do not think their processing in the audio chain as as good as Bose either. That is a somewhat subjective opinion though. But take Hex for example, while sounding impressive somewhat still, I am sure it used to sound far better back in its opening years. With a fresh Bose setup.
I noticed those old rock speakers from Ug Land back in October. When walking up past the lake towards Hex from Mutiny Bay you can see some of the left. They were custom made by Tussauds for Ug Land and housed the commonly used Bose 151 / 325se lould speaker inside (the old design).
Not sure which one as both speakers are in the same enclosure. I would take a guess and say Bose are still inside them today, as they were designed specifically to hold the chassis of that speaker enclosure, so not much else would fit in them.
Any fan of Alton Towers will have seen these everywhere in Alton Towers back in the day, they were in the monorail stations, towers street, stacked on the top of Obivion and queue, on the Spinball break run and Ug Land speakers to name just a few places. These 151 speakers and their identical looking 325se models were by far the most common speaker seen on park, in black and white. Almost every attraction on the park had these for something, be it station announcements or queue line videos, or part of the ride itself. They were everywhere. They used quite a few other different models too, but these were the most common.
I think Spinball and Galactica still have these as did Duel in the station as of last year. They were mounted above the trains in the station when it was Air and used to play the "prepare for air" and "now fly" announcements. I am sure they got a custom air blue paint job too.