An inequality about average

Question

If $f$ on $\mathbf{R}^n$is integrable,we define two operators as following. $$Mf(x)=\underset{r>0}{\sup}\dfrac{1}{\lvert B_r\rvert}\int_{B_r}\lvert f(x-y)\rvert\, dy,\enspace B_r:=\{x|\,\lvert x\rvert\le r\}$$ $$M'f(x)=\underset{r>0}{\sup}\dfrac{1}{(2r)^n}\int_{Q_r}\lvert f(x-y)\rvert\, dy,\enspace Q_r:=[-r,r]^n$$ When $n=1$,$M$ and $M'$ coincide.However,if $n>1$,my question is why there exist constant $c_n$ and $C_n$,depending only on $n$,such that $$c_nM'f(x)\le Mf(x)\le C_n M'f(x)$$ It seems obviously,but I don't know how to deal with it.