Shortcut or badcut?

Thanks for letting us know. You would like a little more extension, shimmer and sparkle.

Easy! When was the last time you cleaned? If its been more than a year you may be surprised how much extension and detail has been slowly gradually obscured by dirty connections. Yes its a regular maintenance thing..... that hardly anyone does.

Anything more than a year and you should be able to hear a nice improvement even from something as simple and free as wiping everything off real good with alcohol and a clean cotton cloth. Disconnect everything and clean every RCA, spade lug, power cord prong, absolutely every metal contact you can get at.

This is what you can do for free. There’s a million cleaners and contact enhancers out there, all the dozen or so I’ve tried are frankly not a whole lot better than alcohol. (Keith Herron recommended plain old alcohol to me.) But if you can afford it, Total Contact from Perfect Path Solutions is in a whole other league and will transform your system every bit as much as a major cartridge or amp upgrade. Maybe more. If you do your panel then for sure a lot more.

So, how long has it been?

{Edit- post removed. Sorry to say but the overtly political nature of post removal has been a topic of late. I removed the following post myself. It was a dupe. First I got an "Application Error" and my post wasn’t posted. So I posted it. Only to find it posted twice. So I removed the dupe. Me. Not admin. Admin specializes in removing posts that should be left up.}

Sincere thanks for the info and suggestions.
I just wanted more high-end extension. Sometimes I miss the shimmer and sparkle of the higher end.  I'm also one of those weirdos who think the inaudible higher frequencies have an effect on our bodies, and therefore, our listening experience, just like the very lows do. (I was once exposed to 22kHz, through an apparently loud driver, and although I didn't hear a thing, I felt like being exposed to positive ions, like at the seashore. ) 

OP... What is your definition of "air?" Is it to increase the high frequencies, meaning more high-end extension? Or are you looking for the phenomenon of air around the instruments? This would increase the space surrounding each instrument and improve focus.

If all you want is more high-end detail and extension, then super tweeters are worth trying. For true "air" in the audiophile sense, then it's more complicated.

You will lose your sense of sound stage.

I am quite happy with the sound I have, so I will take the given advice and not mess it up with a dumb idea.  The SuperTweeter seems like the way to go, so I will $tart $aving.

Thanks for the info.  Much ....appreciated.

It can be done, But..

Generally to accomplish doing so and getting it to perform and sound worthwhile will require 'pro sound' equipment of the sort you see at concerts. They have a whole range of devices and means to make those arrays 'do what they do'...*S*

@mijostyn has your best option, but level and balance control over the back pair (at minimum...eq added to that is a plus) would perhaps fill the bill for just sheer volume.

No guarantee as to what you may hear, however...*shrug* 

I highly doubt this will accomplish your goals and will likely create more problems than it solves.  It would help greatly if you would share what equipment you’re currently using along with a bit about your room and speaker positioning. 

@sound22card - If you think about what is at play IF you were to do this...- 

e.g. Each set of speakers has it's own cross over, so unless you implement the same model/year of speaker there will likely be differences in the signal path, which can lead to degraded sound

Different speakers will have different tones, so now the entire tone has changed and maybe not for the better

The two sets of speakers could result in out of phase signals - which will impact sound/image - sort of like a bad echo effect

These are just a few of the issues.

It really depends on how picky your are about your sound.

The "air" I currently enjoy is due to the speaker cables and the speakers I currently have.

The speakers/crossovers are tested and tuned in an independent lab to extreme levels in order to deliver the best quality sound their drivers can accommodate and the cables allow them to function to their highest level.

I would start with cables

What cables do you currently have???  

Regards - Steve

I would suggest using a pair of Townshend Super Tweeters. If they don't accomplish "air" they will still enhance your current speakers or for that matter most likely any speaker.
I have used my Townshend Super Tweeters with 6 different pairs of speakers with very good results.

I assume you have not got separate volume controls for speakers A+B.
If you put the speakers in the back of the room at greatly reduced volume it will make the room sound larger. If you put them up front with the others it will screw up the imaging like a blurred picture. Roberjerman is right. If you run tweeter up above 10 kHz this will give you a sense of air and detail but it is artificial and most of us do not do this. The "air" in the recording is the right air. 

Buy a pair of JanZen D-130 electrostatic tweeters! These were used in days of yore to improve the treble of Acoustic Research and KLH box speakers. Unfortunately long out of production. I have a restored pair, along with vintage AR's and KLH's!

Is there some point to try to add a bit more air to my speakers, using the 'second set of speakers'  switch on my receiver?

The usual meaning of "air" is used as a metaphor for a presentation in which individual instruments and voices are heard so clearly individual and distinctly separate as to have a space or air around them. The sound of each individual musical source reverberates within the acoustic recording space and this too when believably reproduced is referred to as air.

Is that what you're going for?

I don’t think you’ll get air, but hey, so long as both speaker pairs are 8 Ohms, try it. :)

Speaker placement and room acoustics are a better way to go. Experiment for free with some blankets and pillows on the walls and on the floor.