Vanguard Caldera 12" Active Subwoofer

This is fun. I like to try and it has been in my head for some years to try, add 2 subwoofers to my system which has 2 RELs Ti9. VeraFi audio made this possible for me with his offer of Vanguard Caldera 12" Active Subwoofer. Since they sell for 399$ each it was easy to grab 2 and try on an old dream.
I did discover in 2019 what 2 subwoofers do for the sound of a stereo system and during that play I remember reading that adding 2 more enhances the effect. A seed of curiosity was planted and last week I had 2 more in my possession. 
I went with my gut and placed them on the side wall, 4 feet from my speakers, facing my listening seat. Cheap 12 feet RCA was bought and a signal taken from Pre out of my ModWright LS100. Advice was given to play one of the subs out of phase to avoid standing waves. This I proved to be correct. My idea was to have the new subs only play the lovest registry of the bass. My RELs go pretty low but the Caldera has a bigger woofer and the box is bigger so I gave them the benefit of playing even lower than the RELs. The rolloff for them is around 50hz and volume was set to be almost audible at normal listening level. 
The impact was immediate. Playing Felix Hell, Organ Sensations, track 4, Abendfriede, where the volume is low but I could feel the vibration in my feet playing below normal volume.  This is stunning. This is fun. The soundstage becomes much bigger. To the point of the room being filled with sound. At higher volume I could hear a halo around the bass note that I do not like (or is "good or correct") but I have come across this before. Good feet under the woofers will help with that. 
I did have the idea of moving them to the side of the speaker as well as in the corner behind but I really like how this worked out so I keep them where they are. 
If one has 2 subs and likes to try to add another 2, this is a no brainer. 

I just received my two Caldera 12” subs. The entire order process was effortless and the shipment to Canada went very smoothly.
The fit and finish are excellent ( I love rosewood ) and the performance in my very large 16' x 28' x 9' listening room is excellent.
I'm using them to extend the low frequency performance of a pair of large stand mounts and have them crossed over at about 50 hZ. They have integrated beautifully and now make the main speakers sound totally full range. I'm now getting extension down to the low 30 hZ region and enjoying a full bandwidth presentation! The bass is tight, fast and very articulate.
I don't think they're even broken in yet with only about 10 hours on them, so I'll keep you posted with a future update.
I don’t know how the guys at Veri-Fi do this, but these would be an absolute bargain at twice the price!