The standing proposal is that 11 and 13 take the first two notes an octave up. The problem is that an octave is perceptually the same note: 11 will sound like 2, and 13 like 3. That might read as a second family of primes, which would be lovely — or it might just be confusing.
Three alternatives are here too. Switch schemes while listening; the comparison pairs are the fastest way to hear it.
2 · 3 · 5 · 7 are fixed — they are what the lab already sounds. Only 11 and 13 change.
The question to answer: with 11 and 13 in the set, can a child tell six primes apart — or does she hear four, twice?