I received the OM-18/21 about a week ago and have packed as much time in playing it as I possibly could with busy work and family life. The sound matches up more or less with what I predicted a Circa OM-18 would sound like. Though I've played a number of Circas, I don't think I've ever played one with mahogany back and sides.
It's evenly balanced in response across all 6 strings, though I suspect it has the potential to develop a bit more bass over time. It already shows signs of having a little more bass than your average 18. It's loud and aggressive with plenty of headroom - no big surprise there given the style John is using for his builds and the very stiff spruce used. Although it tends to the drier side of the spectrum, as is typical for mahogany, it does have a fair amount of overtones - probably somewhere in between what I would usually expect from mahogany and rosewood. Significantly, though, the overtones don't interfere with note separation. Great note separation is one of the reasons I have so much love for mahogany.
It has the great mid-range response and plenty of sweetness in the trebles. The sound and response is really classic mahogany, to my ears. The setup is flawless, with the Plek zeroing in on exactly the relief that works for my playing. It's quite light at 3 lbs 12 oz and the graphite truss rod makes for a great physical balance (not neck heavy) when the guitar is sitting in your lap.
Build quality and workmanship is flawless - truly.
To me, this guitar is yet another demonstration of why John's work is in such high demand, and it's why I keep going back to the Circa well.
