Using REW to investigate xovers in old receiver

[maxcooper]

I have an old Sony STR-DA333ES receiver. I have always wondered where it crossed over the mains to the sub. The manual doesn't give this specification anywhere, and it is not adjustable.

So, today I used REW to investigate. I connected the SPDIF output of my soundcard to my receiver, and connected a pre-out (sub or right channel) to the Line In on the soundcard to do my tests. I put the receiver in "Auto Format Decode" mode, which gives 2.1 when feeding it PCM from the soundcard. I also tried "Cinema: Normal Surround" (ye olde DPL) mode and found the sub crossover to be the same as AFD mode (I gave up trying to measure the highpass portion, since the signal was routed mostly to the center).

With the front speakers set to SMALL, this is what I got:
crossover.jpg

Hmm... seems to be crossed over at about 120 Hz with a 6 dB/octave high pass and a 12 dB/octave lowpass. Or at least that's what I think I see. I'm a novice, and I welcome any corrections if I am not perceiving that correctly.

As expected, with the front speakers set to LARGE, there is no highpass, and the sub lowpass stays the same (I think?):
crossover_large.jpg

Well, I am glad I finally know the secret, even if it is somewhat bad news. I was hoping that it would be 80 Hz.

-Max

[DrWho]

I wonder how hard it would be to swap some parts and move the crossover lower. I would imagine they are just using basic analog filters and using a relay to select the filter type.

But with that shallow of a slope for the mains, it wouldn't be that bad to set the crossover on your subwoofer to 80Hz. You'll have to boost the output a bit to flatten out the summed region between 80 and 120, but it's not going to take much.

[brucek]

I would imagine they are just using basic analog filters

I believe todays receivers/processors use digital filters since they all use DSP's in the decoders. Analog filters are normally only used in speaker crossover design......

brucek