Weird behavior with bass management and REW

[bkeeler10]

So last night I was using REW to do some measuring of my system. I ran across a curious behavior, and I'm not sure where the problem lies. For reference, I use my HDMI-equipped laptop running Windows 10 and the latest (or nearly latest) version of REW, and UMIK-1 microphone with calibration file

I have bass management running on my receiver (a NAD T758 v3). However, when I run a sweep with HDMI channel 1, 2, or 3, I sometimes don't get output from the subs. Rather, everything is going to the main speaker - it's as if bass management has been turned off in the receiver. Perhaps the strangest part is, it seems to be intermittent. On some sweeps I'll get the response I expect and the subs are clearly participating, and on other sweeps the subs just go away. This is happening in back-to-back measurements, without restarting any equipment or software, or changing any connections.

As far as I've heard while playing actual content from other sources, this has never happened in actual use. So it's hard to blame the receiver. And yet, I can't think of anything going on with the computer itself or the REW software that would cause this. After all, REW can't know whether there's bass management running downstream of it.

Hmm, well now that I'm thinking about it, I suppose it's possible the receiver is to blame. I do get pretty good response from the speakers themselves, and most of the content I listen to that doesn't have an LFE channel is not demanding in the bass department, so perhaps it just hasn't been noticeable. I'm going to look into that idea further. So I may be barking up the wrong tree here, but if I'm missing anything regarding how REW or the computer might be causing this, please let me know.

 

[JStewart]

I sometimes don't get output from the subs. Rather, everything is going to the main speaker - it's as if bass management has been turned off in the receiver.

So you're getting a full range sweep of the speaker then or is the response of the speaker with the high pass bass management filter on and just no subwoofer output?
Either way, very strange behavior. I'm inclined to agree with you that the problem would lie with the NAD. I can't see either how the input would cause bass management in the NAD to be bypassed.
Here's the link to a NAD support request if you need it. https://support.nadelectronics.com/hc/en-us/articles/360000158868-Welcome-to-the-NAD-Help-Centre Its toward the bottom of the page. IIRC they'll have you create an account that works for both NAD and BlueOS and I found it a bit confusing myself.

 

[bkeeler10]

I will have to play around some more to determine if the response from the main speaker is the same with bass management switched off as I'm getting with bass managment on. It is rather strange indeed. More troubleshooting is in order.

 

[John Mulcahy]

Some subs turn themselves off if there is no signal, they can vary in what they look for to turn back on.

 

[JStewart]

I will have to play around some more to determine if the response from the main speaker is the same with bass management switched off as I'm getting with bass managment on. It is rather strange indeed. More troubleshooting is in order.

Set xo to 200hz so easier to see?

Anything else in the signal chain like minidsp?

I hate anything intermittent. Always a pain.

 

[bkeeler10]

Some subs turn themselves off if there is no signal, they can vary in what they look for to turn back on.

I was making back-to-back measurements, within less than a minute of each other. So this shouldn't have been a problem.

 

[bkeeler10]

Set xo to 200hz so easier to see?

Anything else in the signal chain like minidsp?

I hate anything intermittent. Always a pain.

Setting a different crossover is a good idea, for troubleshooting purposes.

I do have a minidsp 2x4 between the AVR and the subs. I have two subs that are done at 30 Hz, so I have them high passed in the minidsp. The other two are unthrottled on the bottom end. All subs are low passed at around 200 Hz. There's some delay set. And there's a bit of EQ on the output.

 

[JStewart]

I asked about MiniDSP because I had a problem once where filters weren’t applied to one channel. That was weird too and a power cycle fixed it. Unlikely this will help, but then everything seems unlikely.
Good luck.