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[nakamoto]

I have a usbstreamer B which shows up as an ASIO sound device, this is hooked up to an ADA8000 which goes to 2 studio monitors and 1 amplifier for the subwoofer. The usbstreamer B supports ADAT out with 8 channels. I am having a lot of trouble with EQing the subwoofer and some of it is related to issues with JRiver. I have my left speaker hooked up to channel 1, my right to channel 2 and the subwoofer on channel 4. Whenever I try to change the relative dB in room correction the clip protection will quickly go higher and the overall sound level goes down. The signal LED on the amplifier for the subwoofer is usually dim and only turns on when there is a lot of low frequency noise, no matter what I try to change in JRiver I cannot get a strong signal to the subwoofer without the main speakers being deafening. This may have something to do with how JRiver mixes audio to create the subwoofer channel, but I have tried it using parametric EQ and room correction and I am not getting a good response.

I have tested each channel individually with an ASIO tester and everything seems relatively normal when I do that. The signal to the amplifier is more or less correct as it should be, only a 10 db boost is required for the subwoofer channel. This makes me think it is some kind of issue with JRiver.

What exactly is this clip protection? I could not find documentation on it.

Here is my ADAT interface

http://www.minidsp.com/products/usb-audio-interface/usbstreamer-box

[mwillems]

The clip protection function works like a limiter.  If the audio content would clip, it just turns things down so that they don't clip (which is preferable to clipping in most case as loud clipping sounds terrible and can wreck equipment in the right circumstances).  If you see it engaging, it most likely means you're adding boost and not offsetting it.

The vast majority of digital audio is mastered so that it has a peak at or near 0dBFS.  No digital sound can go over 0dBFS without clipping.  That means that if you try to add gain to any channel without offsetting it somehow it will push that channel into clipping (sooner or later). 

So the way to create effective "boost" on certain channels without clipping is to attenuate the other channels appropriately.  So if you want a 10dB "boost" to your sub, reduce the left and right channels by 10dB (i.e. apply a -10dB filter to them). 

If you have any net boost without an offset, you will get clipping sooner or later unless you offset it somehow.

[nakamoto]

The clip protection function works like a limiter.  If the audio content would clip, it just turns things down so that they don't clip (which is preferable to clipping in most case as loud clipping sounds terrible and can wreck equipment in the right circumstances).  If you see it engaging, it most likely means you're adding boost and not offsetting it.

The vast majority of digital audio is mastered so that it has a peak at or near 0dBFS.  No digital sound can go over 0dBFS without clipping.  That means that if you try to add gain to any channel without offsetting it somehow it will push that channel into clipping (sooner or later). 

So the way to create effective "boost" on certain channels without clipping is to attenuate the other channels appropriately.  So if you want a 10dB "boost" to your sub, reduce the left and right channels by 10dB (i.e. apply a -10dB filter to them). 

If you have any net boost without an offset, you will get clipping sooner or later unless you offset it somehow.

I'm not convinced this is the only issue.

I tried leaving the sub at 0 db and putting everything else at -10 or -20 even and I still have the problem that the signal to the subwoofer amplifier is weak, it only flashes when there is a loud low frequency noise in a file.

Is there anything else you think I could change to help remedy this?

[mwillems]

What does the "signal light" on your model of sub actually signify in the user manual? Sometimes they represent an arbitrary signal threshold which may or may not be a good target, but I've also seen several amps and subs where a light labelled "signal" was effectively a "pre-clip" light meaning it lit green when the signal was within 3dB or 6dB of clipping.  If it's that kind of light, you don't want it lighting except when there's loud information in the file. 

It's hard to assess what the issue might be without knowing what the "signal light" on your device is supposed to indicate.  How does your sub output actually sound?  Have you tried measuring the sound output?  That's the way to tell if there's really an issue.

FWIW, my current sub's signal light only lights during very loud portions of films, but I've measured the output and it's volume calibration is correct.

[nakamoto]

What does the "signal light" on your model of sub actually signify in the user manual? Sometimes they represent an arbitrary signal threshold which may or may not be a good target, but I've also seen several amps and subs where a light labelled "signal" was effectively a "pre-clip" light meaning it lit green when the signal was within 3dB or 6dB of clipping.  If it's that kind of light, you don't want it lighting except when there's loud information in the file. 

It's hard to assess what the issue might be without knowing what the "signal light" on your device is supposed to indicate.  How does your sub output actually sound?  Have you tried measuring the sound output?  That's the way to tell if there's really an issue.

FWIW, my current sub's signal light only lights during very loud portions of films, but I've measured the output and it's volume calibration is correct.

I have a signal, a -20, a -10, and a clip light.

http://www.zzounds.com/item--CWNXLS2000


I will have a calibrated microphone in a couple of days to get a full frequency response.

But if I use a ASIO test program to just output tones, I can get a good signal, everything seems normal.

Is there some kind of ASIO debugging application I could use to see what is actually going to channel 4?

[mwillems]

Ok that signal light should be lighting up at less than a milliwatt of input so something is probably going wrong somewhere in the signal chain.

How are you creating the subwoofer channel?  Specifically what are your output format settings?  Could you post screen caps of your output format, room correction, etc.?

Also do you experience the same issue with multichannel content with a dedicated sub channel?  Or only with 2 channel sources?

[nakamoto]

I am testing with some video clips now. I would say, it is roughly the same, maybe better. It is hard to find multichannel music.

Here are my current settings.



http://i.imgur.com/Dtx73EN.png

I have tried many variations of the above.

All of the other channels are set the same as left except the subwoofer channel.

[nakamoto]

Ok, I just ran through a few clips from edge of tomorrow and the bass is much better. This is how I would expect it to sound.

A good example is if I play a song that doesn't have over the top bass, but still has some decent LF sound like, Tocatta and Fugue in D minor, I won't get much out of the subwoofer, even though that piece has 32 foot pipes in there. But if I play some overly bass heavy song I will get a lot of output, almost too much. It sounds almost like there is a noise floor limiter or something not giving me that subtle output.

I also couldn't find what exactly "JRSS Mixing" entails.

Some of this is related to room EQ as well, no doubt, but not all of it.

[mwillems]

Ok, I just ran through a few clips from edge of tomorrow and the bass is much better. This is how I would expect it to sound.

A good example is if I play a song that doesn't have over the top bass, but still has some decent LF sound like, Tocatta and Fugue in D minor, I won't get much out of the subwoofer, even though that piece has 32 foot pipes in there.

That may not be the best example as much of the bass in that piece is below 20Hz, and redbook audio (CD standard) isn't obliged to reproduce any sound below 20Hz.  So depending on the source of your recording you may not have the actual fundamentals on the lowest notes (only overtones).  Additionally, I don't know what your sub's FR is like, but you should take into account that many subs don't reproduce very low tones at the same volume they might reproduce higher frequency tones (like you might get from a bass guitar).  

If you want to get to the bottom of this, I would recommend testing with low frequency test tones or a software sine wave generator and try stepping through 1) different frequencies and 2) different volume levels.  That would expose the issue pretty quick if it was a noise floor limiter or a frequency response issue.

This does remind me of something I ran up against a few years back.  Some subs have a pernicious "auto-off" feature that turns them off to save power when the input is below a certain threshold; my experience is that the threshold is sometimes set a little on the high side, which would have the kind of "gating" effect your seeing (soft bass is inaudible because the sub is actually off, loud bass is plenty audible).  Some subs have a three position switch ON/Auto/OFF so you might want to check that (unfortunately some subs only effectively have two settings "auto" and "off"; hopefully that's not your situation).

But if I play some overly bass heavy song I will get a lot of output, almost too much. It sounds almost like there is a noise floor limiter or something not giving me that subtle output.

With your settings, JRSS Mixing will not touch the sub channel at all (it just handles up and down mixing).  7.1 audio will be played back natively, 5.1 will be upmixed to 7.1 (which should leave the sub alone) and stereo music will be left alone by JRSS mixing (due to the combination of only mix to 2.1 and the "silent" setting).  The room correction bass re-direction should be the only content in the sub with stereo content.

[nakamoto]

Yes, I will wait for the calibration mic to come and test the frequency response with REW and see what I can do.

It could also be a line level problem, but I think it's not.


The subwoofer is this driver in a 4 cu ft box.

http://www.parts-express.com/dayton-audio-rss460ho-4-18-reference-ho-subwoofer-4-ohm--295-472

part of the problem is likely that the subwoofer is a little overpowered compared to the studio monitors.

But, I will wait for the mic to come for now.