The time-domain equalizer (TEQ) is a commonly used device to shorten the channel impulse response in a discrete multitone (DMT) receiver. With a capacity maximization criterion, a TEQ design method called minimum intersymbol interference (minISI) has shown to have nearly optimum performance. However, the minISI design method require high computational complexity, adversely affecting its real-world implementation. In this paper, we propose a low-complexity method to overcome this problem. The main idea is to use a subset of the subchannels, instead of all, for capacity maximization. With a simple equally-spaced sampling method, the number of subchannels required for calculation can be effectively reduced. Simulations show that the performance of the proposed algorithm is almost the same as the original minISI while its computation is dramatically reduced.