Returning spectrumdata to an array of 64 floats in good framerate

I am making a parametric equalizer, and the script underneath works fine with returning 8 floats, based on the incoming audio. What I can't seem to fix, is returning a higher number of floats than 8 without unity framerate going superlow, or it just doesnt work. I need abit help to get it to work returning to 64values with good speed. Maybe there's a better solution than mine?!

using UnityEngine; using System.Collections;

     public class AudioToFloats : MonoBehaviour {
 
     private float[] samples = new float[512]; 
     public static float[] curValues = new float[8]; 
     string ss = "";




         void Start () {
         
         }
         
         // Update is called once per frame
         void FixedUpdate () {
         int count = 0;
         float diff = 0;
         AudioListener.GetSpectrumData(samples, 0, FFTWindow.BlackmanHarris); 
         ss = "";

         for (int i = 0; i < 8; ++i) 
         {    
             float average = 0;    
             int sampleCount = (int)Mathf.Pow(2, i) * 2;
             for (int j = 0; j < sampleCount; ++j)
             {
                 average += samples[count] * (count + 1);
                 ++count;
             }
             average /= count;
             diff = Mathf.Clamp(average * 10 - curValues[i], 0, 4);
             curValues[i] = average * 10;
             ss += curValues[i].ToString("0.000")+",";
         }
             }

 void OnGUI()
 {
     
     GUI.Label(new Rect(150, 0, 600, 500), ss);
     int ImageHeight = 300;
     for (int i = 0; i < 8; i++ )
     {
         float Height = ImageHeight * (1 - curValues[i]);
         
     }    
 }
         }