fly under the radar because advertisement just too expensive or not viable.
I don't think I have ever seen ATC advertise although they are longtime supporters of the Audio Engineering Society and have published peer-reviewed engineering papers on speaker technology, which is a form of advertising if you think about it. ATC management and design staff are bona-fide degreed audio engineers rather than DIYers with a passion for audio that became gifted at cabinet making and went into business from that route. One of the few small companies that make their own transducers instead of sticking to wood work and third party parts assembly.
ATC is a UK company based in rural Gloucestershire (presumably for access to lower cost labour and skilled crafts people). They tend to sell speakers by word of mouth and have have barely began to penetrate US markets in the last ten years; they remain a name that the majority of North American Hi-Fi dealers and audiophiles have never even heard of. They fulfill a small niche for Studio precision/reference sound at realistic SPL levels/dynamics of live music but with audiophile precision rather than PA sound (PA or live event sound reinforcement is a much bigger market as JBL and Bose can attest to). Recently, ATC have began installs in exclusive night clubs/Jazz clubs and high end concert halls such as the Disney Concert Hall in LA....again a niche market. They also have made home studio installations for some well known musicans/artists.