Castle is a traditional hi-fi company that builds traditional products, and the Classic Sub reflects this. It's one of the few subwoofers around that looks like furniture, with its rich veneer and bolt-on plinth. It's hard not to overstate the finish; were it not for the big grille at the front of the speaker, it could easily be mistaken for a side table.
The Classic Sub boasts a thoroughly conventional 300mm front-firing bass speaker, partnered with a 200W amp. The nearest it gets to revolutionary is the carbon fibre used to load the paper cone of the bass driver. Conventional doesn't necessarily mean boring, however, as the speaker has been co-designed with British monitor loudspeaker company ATC.
The cabinet is extremely well-made, inside and out, with heavy MDF and the sort of solidity needed to deliver sound from 200Hz down to a claimed 20Hz. It's difficult to get such deep bass from a solid cabinet, and many subwoofers rely on ports to simulate this, but the Castle is a totally sealed box. This reflects the musical background of both ATC and Castle.
Both companies are music-oriented, and demand a faster, tighter and more even bass than can be provided by a ported subwoofer. The downside to this is that the subwoofer doesn't seem to move as much air as a ported sub, and as such it could be less impressive for out-and-out energetic home cinema.
This theory is borne out in practice. The Castle delivers a brilliantly musical sound that is seemingly as genteel as its looks, but also offers a mighty punch when required. This is one of those subwoofers that treads lightly when correctly set up, making no unwarranted noises.
But when bass is needed, it provides solid, powerful support, underpinning the sound of the main speakers perfectly and making it almost impossible to determine where the main speakers stop and the subwoofer starts. This comes from the Classic Sub's extraordinary neutrality.
Clean and clear?
Of course, there are times when this sort of clean, accurate and musical bass just isn't enough, and it's here that the Castle sub begins to fall short. In a strictly cinema setting, where what is required is edge-of-the-seat excitement, you'll end up either setting the Classic Sub too high and too loud (meaning it'll deliver the occasional earth-shattering thump), or else setting it correctly and never stirring the blood.
So, when the Death Star blows up at the end of Star Wars, the sound is precise, but not the sort of impressive 'Kaboom' you'd really want from the end of the most despotic weapon of mass destruction in the galaxy.
Castle's Classic Subwoofer is too refined for out-and-out movie use, and is more suitable for those who plan on playing a lot of music. If you have a Castle hi-fi system, for example, this subwoofer is the perfect partner. If, however - as is likely - it's all about movies, you'll need to look elsewhere.