The Profile 636 is a genuine 3-way design with a driven bass unit in a sealed enclosure. Above it is Tannoy's 'Dual-concentric' 2-way combined tweeter/mid-range unit. The tweeter sits behind the mid-range driver (inside the cabinet) and voices out through a 'tulip wave-guide' in the centre of it. This arrangement is not as good as KEF's uni-Q, as the tweeter is actually further away from the listener than the main driver. But nonetheless, it does give more of a point source that can only help with imaging. The drawbacks are timing errors between the tweeter and mid-range and a slightly 'shut in' sound to the treble. As far as I can remember, these were the only sealed box designs in that Tannoy model range. This did them no harm at all. The bass was described as having a few Htz more extension (44Htz vs. 47Htz?) than the ported and cheaper Profile 633 model, which had the same cabinet dimensions. All the floorstanders had prodigious bass output, for their size, and the 636 was no exception. It was a real rival for the TDL RTL3 that was its similarly priced and the more popular competition, at the time. As it was only a 'budget' floorstanding speaker, there are always going to be some noticable compromises to its design and sound. The treble I've mentioned, but the fairly lightweight vinyl wrapped MDF construction made itself known by a certain boxiness to the mid-bass, despite the triangular cabinet cross section. There was provision to mass load a compartment within the base, but this made little difference. They were a relatively easy 6 ohm load, making them a good match for my Cyrus 3 amp. With high listening levels, they would make its casework get hot to the touch, but never 'suck the life out of it', like my later 4 ohm KEFs did. To sum up, although these speakers have their inadequacies, they do something that, to me, is a basic requirement missed by the vast majority of loudspeakers available: they have a genuine go at reproducing the deep bass. Leftfield's 'Leftism' sounded awesome and I've never enjoyed listening to Metallica's 'Enter the Sandman' so much, as when I had a pair Profile 636s!