Request info on Subwoofer output on Node 2

Answered
Simon Blandford

I am using my Node 2 with studio monitor main speakers and an active Sub. It sounds fantastic!

I would just like to understand a bit better how the "With Subwoofer" function works so that I can fine-tune my active sub.

1) Selecting the "With Subwoofer" option, from what I can tell from other posts, activates an 80Hz high-pass filter on the main analogue outputs. Does it also activate an 80Hz low-pass filter on the sub out? If it does then I guess I can open up the upper frequency limit on the active sub and let the Node 2 take care of the crossover. Otherwise I would set it to 80Hz.

2) What is the number of poles, or dB/octave, of the 80Hz filter?

2) Is the filter implemented in DSP or after the DAC using some analogue filter (just curious)?

Thanks

1

Comments

8 comments

Date Votes
  • Official comment
    Tony W.
    Product Support Manager
    • Edited

    Hi Simon

    1) The sub out put is always active up to 80Hz regardless of in use or not

    2) We have never measured this but in speaking with our engineers, it rolls out at about 2db/octave starting at 80 Hz

    3) The external DAC bypasses our DAC completely so no processing is done and will receive full range

    We always recommend try a couple of options and go with what your ears tell you...

    Tony

  • Simon Blandford

    Hi Tony,

    Thanks for the response. A couple of points:

    A single pole filter would have a roll off of 6dB/Octave, two poles would be 12dB/Octave so a figure of only 2dB/Octave is somewhat surprising.

    I was referring to the internal DAC, not an external DAC. However if there is no roll-off when using an external DAC then that indicates that the sub filter is analogue and between the internal DAC and the audio outputs.

    Regards,

    Simon

    1
  • Simon Blandford

    OK. I've done some measurements myself. As far as I can tell the low-pass filter on the Sub out is -6dB at 80Hz then a 24dB/Octave roll-off after that.

    When the "Select Attached Speakers" option is switched to "With Subwoofer" then a complementary high pass filter which also appears to be -6dB at 80Hz then, I assume, 24dB/Octave roll-off after that although I wasn't really able to measure that so well with the white-noise/FFT technique I was using.

    2
  • yodogyodog

    Is there any fix in the works to resolve the max volume on the sub out issue when using fixed output level + digital coax out to external DAC (like a topping E30)?

    Also, why is there nothing in the works as far as the software implementation on being able to adjust the roll off slopes for the always on LPF on the sub out rca and also the HPF on the digital coax out when “With Subwoofer” option is selected in the BluOS Controller (iOS)?

    0
  • Tony W.
    Product Support Manager

    Hi Yodog

    If you are using FIXED output, you should have your SUB connected not to the player but to the amplifier that is controlling the volume. Please redirect your SUB to resolve the issue.

    0
  • yodogyodog

    Roger that. I was wondering, do you know if the output voltage/volume level for the coaxial digital rca out is the same when it’s on fixed output mode versus just having the volume set to maximum via airplay 2 but allowing the node 2i control the volume as well?

    0
  • Tony W.
    Product Support Manager

    FIXED is FIXED regardless of output.

    A word on AirPlay and Bluetooth - yes you will still have 2 independent volume controls that need adjusting;

    • The source
    • The Amp

    Both will need to turn up to hear.

    On Variable you would have 3...

    0
  • yodogyodog

    So on variable, if adjusted to the maximum volume, would it be identical in output as the “fixed volume output” option selected as active?

    1

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