In this letter, the authors present two improved split vector quantization (SVQ) methods for line spectral frequency (LSF) parameters. By using these methods jointly, the codewords and quantization results conserve a given minimum difference LSF (dLSF), although they are trained and quantized with a weighted distance measure. Experimental results show that the proposed methods are more effective than conventional SVQ methods, because the total training error and number of outliers due to quantization are all reduced.