If you're using hacking your Ikeas Symfonisk Sonos speaker to bi-amp a pair of passive speakers, you need to know what the electronic crossover frequency is of the amplifiers to make sure it's compatible with your speakers. I used close mic'd measurements of the frequency response of the woofer and tweeter to try and reverse engineer the crossover frequency between the amps (sound 1,600hz). While I was testing, opened the speakers and tested the impedance of the woofer (4ohms) and tweeter (8ohms) - you can basically use any speaker components are that are 4-8ohms, run Trueplay and it will sound great,