Two quite different sizes of subwoofer. Room volume decides this more than anything else on the page: a big driver in a small room is wasted, and a small one in a large room is worked to death.
| Area | Better | Why |
|---|
| Bass depth | B | MartinLogan 400 goes deeper - 30Hz against 35Hz. A real difference, though most music has little content below 35Hz. |
| Driver area | A | MartinLogan Dynamo IW S moves more air: 2 x 8" against 8" is 2x the cone area, not the 1.41x the diameters suggest. More area means the same output with less excursion, and less distortion with it. |
| Cabinet size | depends | MartinLogan Dynamo IW S is about 69% smaller by volume. In a subwoofer that is a real trade rather than a preference: box volume is how you get output low down without a bigger amplifier. |
| Warranty | A | MartinLogan Dynamo IW S carries 5 years on parts against 3 years. A subwoofer amplifier works harder than anything else in the system, so this is not a throwaway line. |
| Price | B | MartinLogan 400 costs less - $500 against $1,600, about 69% less. |
A MartinLogan Dynamo IW S B MartinLogan 400
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both subwoofers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
MartinLogan Dynamo IW S is ahead, but on only 1 of the measured areas, and it costs about 3.2x the price. MartinLogan 400 is the sensible buy unless your room is large enough to need the extra. Two small subwoofers beat one big one in most rooms - a pair evens out the room modes in a way no single box can, whatever its specs. At $500 each, two MartinLogan 400 cost about $1,000 against $1,600 for one of the other, which is worth a thought. If placement is the constraint - a corner, behind a sofa, under a desk - MartinLogan Dynamo IW S is the one that will actually go there, and a well-placed small subwoofer beats a badly-placed big one every time.
One thing outweighs everything above: where the subwoofer stands. Room modes can add or remove 10dB or more at a given seat, which is far larger than any difference on this page. Before spending more, try the sub in two or three positions - the crawl test, where you put it in the listening seat and crawl the room to find where the bass sounds best, costs nothing and usually beats an upgrade.