Filter Visualization Tool help

Hi, I have tried to execute the following code :

clc;

clear all;

n = 6; f = 0.8; a =fir1(n,f,'high'); %fir high pass filter b = fir1(n,f, 'low'); %fir low pass filter [y,fs] = audioread('pong.wav'); %load audio file

o = filter(a,1,y); %passing audio to designed high pass filter p = filter(b,1,o); %passing o to designed low pass filter

fvtool(p,1); %use to display designed filter

subplot(2,1,1); plot(y); %original signal y

subplot(2,1,2); plot(p); %filtered signal

But it shows following error:

Error using Filteraudiosignal (line 14) When first input is a matrix, it must have exactly 6 columns to be a valid SOS matrix.

Can anybody help me in this regard??