Sat front row at the symphony...

At Symphony Center in Chicago there is a semicircular "terrace" above and behind the orchestra, where the chorus sits when it is required.  Listening from that vantage point is a unique experience.  I describe it as like having an aural X-ray of the score.  Every detail of orchestration is distinct, powerful, and vivid.  Of course, it's not ideal when there's a soloist, whose back will be facing you.  But for an orchestral piece it's a worthwhile experience, much like a very well-mixed recording.

Every detail then how do you here the flutes and oboes along with the horn section that is 15feet in front of the back wall and projecting outward toward the conductor ?

The orchestra is in a huge shell-shaped proscenium.  Some years ago, an array of glass reflectors were suspended at the very top of this shell to improve  the balance of sound for the audience and to help the musicians hear each other.  I can attest to its success.  I can't fully account for the acoustic science of it, but it does work.  Flutes, horns, triangle, whatever...you can hear it in the terrace.  And out in the front of the house on the main floor, where I normally sit, I can hear the woodwinds better than I could in the olden days (for me, that would be the 1970s and '80s.)

@bigtwin Wait til you get your Sound Labs!  You’ll be amazed at how real it sounds. 
 

All the great halls sound good. But they also have front-of-house sound guys who are reinforcing the orchestra. All those small condenser mics hanging over the orchestra? Those are getting used. It’s subtle. These guys are good, and their equipment is top notch.  Their job is for you not to notice. 
 

I’m fortunate to sub with a top 10 orchestra from time to time. Last time I did, I brought up Sonic Tools on my iPad. Sitting just under the conductor by the first violins and <ten feet from the percussion section, the highest SPL on stage was 80dB. It was an orchestral fanfare, not Mahler. But classical music SLOs is much lower than jazz/pop/rock. I try to take that into account when listening at home. 

what mics? You mean there are speakers? It's not pure acoustic?