This paper presents a method to attain very low bit-rate compression of speech spectral envelope. It is based on fixed-length segment coding. The method utilizes Temporal Decomposition (TD) technique for the compact representation of segments of Line Spectrum Frequencies (LSF) vector followed by split matrix quantization. The TD technique is modified to fit fixed-length segment coding. Computation is reduced by using fixed event functions and because event positions determination requires only a simple search within the short fixed-length segment. Weighted Euclidian distance is used as cost function to better approximate the spectral distance measure. The method achieves low bit rates without significant increase in computation cost. The method has been implemented on coding the spectral envelope for the MELP coder and showed its viability.