# miniDSP nanoAVR (HD vs. DL)



## Lumen (May 17, 2014)

Moderators please redirect this post if misplaced :cop: . I found miniDSP discussions elsewhere on the site, but this forum looked the most relevant to me. Thanks!

From what I can tell, Wayne reviewed the *miniDSP DDRC-22D Dirac Live* here, and the *miniDSP nanoAVR HD* here. Thanks, Wayne, for your insights and significant time you invested in those reviews. It would seem that all miniDSP analog/digital, stereo/multichanneL, and Dirac-Live bases have been covered; but I just became aware of the *miniDSP nanoAVR DL* (see link below). Is anyone aware of an upcoming review for that model? Did I miss some member feedback somewhere?

I've studied :reading: miniDSP's home theater models here using the comparison table and technical literature., and have a few questions for the collective: 

:scratch: 
Would you consider the HD model more flexible and feature-rich, while the DL model more plug-n-play?
Can you provide details explaining the pros/cons of the DL model's lack of bass management?
Would you consider the HD model's 96kHZ over the DL model's 48kHz internal sampling rate superior for music listening?
If your answer to the question immediately above was "no," then why would miniDSP bother to engineer it that way?
There's a small footnote under the UMIK-1 picture that reads "* UMIK-1 required for nanoAVR DL, optional for nanoAVR HD." In the case of the HD version, do other options include non-USB mics?
 :scratch:

TIA, BRL


----------



## Kal Rubinson (Aug 3, 2006)

BlueRockinLou said:


> :scratch:
> Would you consider the HD model more flexible and feature-rich, while the DL model more plug-n-play?
> Can you provide details explaining the pros/cons of the DL model's lack of bass management?
> Would you consider the HD model's 96kHZ over the DL model's 48kHz internal sampling rate superior for music listening?
> ...


1. That is a reasonable description.
2. Some don't need BM. Some have BM elsewhere.
3. Superior in theory but not necessarily in practice which depends on the relative success of the HD's EQ vs. the DL's EQ. In turn, that is a reflection both of the system's EQ needs and the user's skill. Not trying to be evasive but there are simply too many variables to permit a one word answer.
4. The limitation is imposed either by Dirac (wanting to keep the price low and not cannibalize the DL market) or by the lack of sufficient DSP power in the box. I do know that adding BM to the DL model would require additional DSP.
5. The HD requires an external program, like REW, for measurement and filter generation. What mic is used is determined by that program.


----------



## Flak (Nov 15, 2013)

BlueRockinLou said:


> [*]Would you consider the HD model more flexible and feature-rich, while the DL model more plug-n-play?


Being more plug-n-play certainly is not the only difference between the HD model and the DL version.
The HD model allows for bass management and an excellent parametric EQ with REW... and has a lower cost.
So why would you want to invest significantly more money in the DL version?

REW will indicate the minimum-phase filters to be used by the miniDSP processor while the DL version will use mixed-phase filters... so let's try to explain what has often been asked, what are these mixed-phase filters used by Dirac Live?

Let's consider three signals, an ideal impulse, an ideal white noise, and an ideal sine sweep.
All of them have a perfectly flat spectrum, that is, they contain an equal amount of all frequencies from DC to infinity.
The difference between them is the phase... for the impulse the phase is constant (zero unless it is shifted), for the sweep it is linear and for the white noise the phase is random.

The phase information is all the difference between these signals, and it tells us about when does each frequency arrive.
For a given frequency response the minimum phase signal/filter is the one that has the most energy arrive as early as possible (hence the name minimum phase).

Now, a speaker in a room can be measured, and showed to have some frequency response.
What we try to do with Dirac live is to improve this response in frequency (to have the desired target as in RCS) and in time (we want the impulse response to be as close to a perfect impulse as possible).

When considering only the frequency response we can (in theory) apply any filter that have the inverse frequency response and the resulting response will be flat.
This filter is often a minimum phase filter, and if the system (the speaker together with the room) was already minimum phase, the result will be a flat frequency response and the impulse response will be perfect.

If the system is not minimum phase (and this will happen at some frequencies in our normal listening rooms) the frequency response will still be flat, but the impulse response will not be ideal, (exactly how it looks will depend on the phase).
In order to get the impulse response correct for a non minimum phase system you need to use a filter that is not minimum phase.

What this filter will do is shift certain frequencies in time in such a way that they all arrive at the same time, thereby achieving the desired result... what we want to do with mixed phase filters is to move all the frequencies so that they come at the same time.

Obviously we cannot move them all to time zero, as this requires us to know about the future.... we have an advanced technology but not that advanced  
Instead we shift all of them to the latest frequency, that is we delay frequencies to match the latest one (within reasonable limits of course) 

An excellent document about minimum-phase is available in the REW documentation:
http://www.roomeqwizard.com/wizardhelpv5/help_en-GB/html/minimumphase.html

Ciao, Flavio


----------



## Lumen (May 17, 2014)

Sincere thanks to you both, Kal and Flavio, for your answers. I think I understand the pros/cons between the two models much better now. 

I know I should use the pounds of equipment and miles of cable I bought, change my couch-potato ways, and start learning REW in earnest to make best use of the HD model. Truth of the matter is, I spread myself too thin over some other hobbies. Along with my honey-do list, I'm in trouble when it comes to climbing the REW learning curve.

Even though I'll have to throw more money at the Dirac Live model, it'll be worth it to me because (a) I really need an easy HT solution right away, and (b) phase-correction benefits come along for the ride.


----------



## Arcanum777 (Sep 25, 2014)

Hi:

I joined this forum with this exact question in mind and must thank the posters for making what I thought might be a long process of reading and learning about the differences into an easy for a noob to understand post about the basic differences between the two.

Time versus money also suggests to me that I will be going the DL unit route. I am sure both would suit my needs.


----------



## Frank D (Sep 1, 2008)

Excellent write up Flavio!

Ciao!


----------

