A system detects symbols communicated from multiple transmitting antennas to multiple receiving antennas. A first detector determines the symbols from respective partial distances of potential choices for symbols from a constellation. A second detector determines the symbols from respective partial distances of more potential choices. The first and second detectors determine their partial distances from signals received at the receiving antennas. The second detector has a lower bit error rate than the first detector. The potential choices for the second antenna are smaller than the potential choices for the first antenna in response to a signal-to-noise ratio (SNR) being higher than a threshold. An evaluator estimates the SNR of the signals received at the receiving antennas. The evaluator enables the first detector in response to the SNR being lower than the threshold, and the evaluator enables the second detector in response to the SNR being higher than the threshold.