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Original poster
Oct 16, 2011
I’m looking to add a powered sub which I already have and an AirPod Express Gen2 to a pair of HomePods and an Apple TV 4K. sub Has LFE, or RCA so I’m using 3.5mm male to L&R RCA male cable to connect. So far so good.

Issues are even though sub has High and Low pass cutoffs I’m still getting full frequencies. Worse in some apps than others. Is there no way to designate a speaker as LFE only? Is there anyway to get LFE only out of Airport Express to feed the subwoofer?


macrumors regular
Mar 16, 2010
Bloomington, IN
No way in software that I know of, if your crossover internal to sub doesn’t work I would add an external low pass filter between airport and sub.
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macrumors 601
May 27, 2008
The airport express can output 5.1 audio, you need an mini-toslink adapter though. it's the same size as a regular headphone plug, but is optical. (if you look in the jack on the airport express when it's outputting audio you'll see a red glow)
you'll then need some sort of device to split that signal, so you can send the LFE channel to the sub. You'll have to do some research to find if there's a device that will do what you want.

All that said, I don't know if it will work like you want it to
I'm not sure if airplay to the airport express will send proper 5.1 audio.
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macrumors 601
Jan 13, 2011
I'm not sure if airplay to the airport express will send proper 5.1 audio.
I'm pretty sure it does, but only when you stream movies. There is no multichannel of any sort in audio AirPlay.
If you mux your 5.1 audio into a MP4/M4V file and AirPlay it to APE, you will get all 6 channels transmitted.
If we are talking about TOSLINK, then it can only be AC3 5.1 or DTS 5.1 (not sure if APE can handle E-AC3 7.1) - meaning you'd need an outboard decoder and amps. There is no way to send PCM 5.1 over TOSLINK.
So for pure audio enjoyment I would use Sub's internal LPF or get a miniDSP DSP where you can program your own filters. The HD version has TOSLINK input :
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