SIR spectrum analyzer

SpectrumAnalyzer is a state-of-the-art spectrum analyzer plugin, which offers a lot of opportunities to display the spectral content of your audio material and helps you create a better mix this way. SpectrumAnalyzer comes in two editions, a free and a full version.
SpectrumAnalyzer uses modern and reliable technics to analyze your audio material. It has a FFT (Fast-Fourier-Transform) and an analog-style (parallel band-pass IIR filter) engine, both of which can run simultaneously. So you can benefit from the more accurate time resolution of the band-pass filters and the better frequency resolution of the FFT at the same time. Check out the cool intelligent peak-detection, which automatically detects resonant frequency peaks in the signal. Use the snapshot function to easily save the current state of your analyzer, so you can compare the spectral profile of your current project with other songs. SpectrumAnalyzer also includes a VU-Meter (with peak and RMS measurement) and a Stereo Correlation Meter.

http://www.siraudiotools.com/Spectrum-Analyzer.php