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miniDSP with an AVR?

I'm new to this and I'm confused.  I'd like to learn how to do basic digital room correction and thought miniDSP was the way to go.

Using a miniDSP seems straightforward with a 2.1 setup:

https://www.minidsp.com/applications/digital-crossovers/subwoofer-integration-with-minidsp
I.e, the input is a source-level line-out, and the output goes to your power amps/active speakers. As long as you have some sort of source-selector and volume-control, this makes a lot of sense.

But with an AVR over HDMI, how does a nanoAVR HD connect and work?

https://www.minidsp.com/ht-series/nanoavr-hd

It has 2 HDMI inputs and one HDMI output.  I assume a cablebox and blu-ray player are fed directly into the miniDSP box ... but if you then send the output to your AVR for amplification, won't the AVR then reprocess the signals and completely mess up the work that the nanoAVR did?  How do you go from its HDMI output into multi-channel amplification?

If there is a link to a post somewhere that explains this in detail, please point me to it. I have searched to no avail.

How do the experts here add DSP based room correction to their multi-channel setups? Or even if they only want room correction for their 2-channel music, how do they connect/integrate it if they are using a blu-ray player as a CD player and an AVR as an amp?

Thanks for any help!

Re: miniDSP with an AVR?

Reply #1
It depends on the AVR I guess, they are pretty good these days, plus most will allow settings to be tweaked after you've run an AVRs auto-setup. My old Denon AVR-2805 placed the setup mic in the listening position and that was it. My X2100W advises 8 positions. They are a lot better at room correction than they used to be.

So I guess it depends what your actual goal is?

Re: miniDSP with an AVR?

Reply #2
I assume a cablebox and blu-ray player are fed directly into the miniDSP box ... but if you then send the output to your AVR for amplification, won't the AVR then reprocess the signals and completely mess up the work that the nanoAVR did?  How do you go from its HDMI output into multi-channel amplification?

The above post seems to presume that audio gear is chaotic and random, when it fact it is generally stable and deterministic.

Most audio processing is in some sense additive. So for example if you apply equalization in one step, and amplify it in the next, then the results are easy to predict - the signal is equalized and then amplified with minimal interaction between the two operations. You end up with a signal that is both equalized and amplified independently, which is what you presumably hoped for. 

The ability of audio gear to process signals without introducing interactions between different sounds in the signal is called linearity, and modern audio gear is generally nothing if not highly linear. For example, unless you go out of your way, signals in the digital domain are handled in a perfectly linear fashion. No phase errors, no frequency response errors, no noise and no distortion is added in the digital domain. If such things exist, they are added in the analog domain, or during the transitions in and out of the analog domain.

However, ADCs and DACs are among the most perfected of all audio components. They are getting within one or a few orders of magnitude of high quality resistors and capacitors.

It seems like every once in a while the performance of ADCs and DACs improves so much that a new generation of Op Amps needs to be created to not detract from their performance.

Note that at these performance levels, ADCs DACs and Op Amps are orders of magnitude better than loudspeakers, rooms, microphones, and the ultimate stumbling block - the human ear.

 If you connect up a chain of DACs and DACs in series, and flip the signal back and forth between analog and digital, even with modest grade parts, it takes something like 5 or more stages to create a reliably audible difference.  If you use really good professional grade converters, it takes 10 or more stages to create a reliably audible difference.

There are test files related to the ADC DAC generations question here - http://ethanwiner.com/aes/  . Fire up FOOBAR2000 with the ABX plug in and hear for yourself using the files labelled "SoundBlaster Generations". Note that the converters involved are inexpensive mid-grade parts, at best.



Re: miniDSP with an AVR?

Reply #3
Thanks for the reply Arnold.  I was not clear about my concern in my first post. I am not concerned about ADC, DAC and amplification having any effect on the processed signal.  I expect all well-designed modern audio electronics to sound the same, and I can see how putting a miniDSP 2x4 in the front of any 2-channel gear would work seamlessly.

I was concerned about the 'processing' that takes place in an AVR.  As I said - I don't really know much about the AVR world, but looking at the buzzwords on a modern AVR (Dolby TrueHD, DTS-HD Master Audio, DTS Neo X etc...) I assumed it is doing something other than DAC and amplification into separate channels. They also include room correction (YPAO, Audyssey, ARC etc..) and selecting a variety of cinema audio modes.  Perhaps I'm obtuse, but it's not clear how parametric EQ can happen before all of this processing, and still remain accurate and useful. Are you saying that none of this extra processing has any effect on the frequency response of the final signal?


Re: miniDSP with an AVR?

Reply #4
Dolby TrueHD and DTS Master Audio are codecs.  A way of simply storing and transmitting information.  A lot like FLAC or MP3.

Stuff such as Dolby Pro Logic IIz and DTS NEO: X are signal processors.  Surround Sound from specially encoded Stereo or additional channels from an existing discrete surround sound format.

And stuff like Dolby Atmos and DTS:X are both codecs and signal processors in one.  Home versions are a bit different from Theater versions in terms of how they work.  I don't have the best understanding in how these work.

Re: miniDSP with an AVR?

Reply #5
I found this on the MiniDSP Website:
Quote
Will the nanoAVR work with Dolby TrueHD and DTS HD-MA?
 
No. While these are true high-definition formats, they are also compressed, used to reduce space on Blu-ray discs, and require proprietary decoders. Adding support for these formats to the nanoAVR would have meant extra product complexity and licensing costs, resulting in a higher price. We decided to keep it simple and put the available resources into high-resolution (96 kHz) audio processing, allowing the Blu-ray player to decode the compressed bitstream.

But, I don't know if these compressed formats will simply pass-through or if they will be corrupted or blocked.

Re: miniDSP with an AVR?

Reply #6
Thanks. I see now that should have been my other question: If the miniDSP unit sits at the front of the AVR, how does it pull out the data for each channel and EQ it without knowing how to do all of the processing/codec handling that the AVR supports? And is it able to EQ the stream without affecting any of those codecs?

From your answer, it sounds like the codecs need to be processed ahead of the miniDSP unit, in the Blu-ray player or settop box - negating the usefulness of the AVR to some extent. Correct?

Re: miniDSP with an AVR?

Reply #7
Thanks. I see now that should have been my other question: If the miniDSP unit sits at the front of the AVR, how does it pull out the data for each channel and EQ it without knowing how to do all of the processing/codec handling that the AVR supports? And is it able to EQ the stream without affecting any of those codecs?

From your answer, it sounds like the codecs need to be processed ahead of the miniDSP unit, in the Blu-ray player or settop box - negating the usefulness of the AVR to some extent. Correct?

It processes the PCM stream and sends it out to the AVR from the way things look.  It can't handle the compressed streams at all according to their site.  So no Dolby or DTS, only PCM.  HDMI is good at informing the player what the device on the other end of the cable can decode and support most of the time as well but sometimes may require additional settings to adjust on a player to work.

To some extent you might lose "some" features that are part of the Dolby and DTS offerings, but you should retain upto 7.1 Surround Sound via PCM and setups greater than 8 channels will not work any higher than 7.1 Surround Sound or not at all in some extreme corner case.

Just make sure your player or streamer supports multichannel linear PCM according to their site.
Quote
Will my player/streamer generate multichannel linear PCM?
You will need to check the specifications of your player or streamer. Players that support Dolby TrueHD and DTS HD MA should be able to decompress the audio bitstream into multichannel linear PCM. Devices that only support Dolby Digital and DTS may only support linear PCM with a stereo downmix, or not at all.

 

Re: miniDSP with an AVR?

Reply #8
You could always just get a receiver with Audyssey MultEQ XT32 for less than $1000 and pay $20 for the Audyssey editor app.

 
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