B18C only has one VTEC solenoid. you're not hearing 2 VTEC engagements... you're hearing the VTEC crossover at 4400rpm, then the secondary intake runners at 5500rpm.

on the Prelude H22A, VTEC and the secondary runners engage at 5200rpm, hence you only hear one change in pitch. Honda had to raise the VTEC crossover on the H22A due to emissions requirements.

if you were to put a P72 GSR ecu into your car, you'd hear the two distinct changes in pitch... but you'll run lean due to the GSR's leaner fuel maps. you can just have the P72 ecu chipped for H22A duty, or get a VTEC controller.