TOPIC:

The NanoAVR-DL requires that bass management be handled by the downstream AVR. There is some criticism that bass management after REQ (such as Dirac) means that REQ has been improperly applied.

When Kal Rubison reviewed the NanoAVR-HD for Stereophile, the same issue came up with bass management being passed down to the AVR. This is after applying the REQ and Kal had pointed this out to MiniDSP. Subsequent discussions and to MiniDSP credit, this was fixed via the firmware such that bass management is done before REQ.

Would like to know if a fix for bass management before Dirac REQ in the NanoAVR-DL is also in the works?

stephenting99 wrote:

The NanoAVR-DL requires that bass management be handled by the downstream AVR. There is some criticism that bass management after REQ (such as Dirac) means that REQ has been improperly applied.

Hi Stephen, where is that? I believe that's incorrect - Dirac Live should see the BM in the "feedback loop" otherwise it can't compensate for it. With BM after Dirac, the Dirac Live optimization will "see" the speaker channels as full range channels which it will EQ, IRC, etc. If you put the bass management first, then the bass management will "mess up" the results that Dirac accomplishes.

When Kal Rubison reviewed the NanoAVR-HD for Stereophile, the same issue came up with bass management being passed down to the AVR. This is after applying the REQ and Kal had pointed this out to MiniDSP. Subsequent discussions and to MiniDSP credit, this was fixed via the firmware such that bass management is done before REQ.

That was a different issue, where the initial version of the nanoAVR plugin required that the sub feeds from all channels be subjected to the same lowpass filter. In addition, the LFE channel had that same filter. In Kal's words; "The summed, rerouted bass and the LFE are subjected to the same low-pass filter." The updated BM plugin has the speaker channels and the LFE channel with independent low pass filters, so there's no chance of accidentally filtering out LFE content (plus you get the ability to do the speaker-sub crossover at different frequencies on different channels.)

john.reekie wrote:

Hi Stephen, where is that? I believe that's incorrect - Dirac Live should see the BM in the "feedback loop" otherwise it can't compensate for it. With BM after Dirac, the Dirac Live optimization will "see" the speaker channels as full range channels which it will EQ, IRC, etc. If you put the bass management first, then the bass management will "mess up" the results that Dirac accomplishes.

Hi John,

The comment came from Kal Rubinson about the NanoAVR-DL in AVS Forums thread.

Regarding how Dirac works for REQ. In the measurement stage, does Dirac sends out the full range signal to each of the main channels (20-20kHz)? Or does it expect that each main channel to be capable of reproducing the full range signals? If in the AVR, the speakers are set to SMALL, with crossover to the sub, say the F3 is lower than 20Hz (as some sub are), what happens? Is there a brick wall and Dirac stops correction at 20Hz or continue to correct until the F3 is reached? What if the speakers set to LARGE in the AVR and the F3 is higher than 20Hz, will Dirac take this into consideration and cut off correction up to the F3, then route the lower frequencies to the sub?

Apologies for these questions as this is all new to me.

That was a different issue, where the initial version of the nanoAVR plugin required that the sub feeds from all channels be subjected to the same lowpass filter. In addition, the LFE channel had that same filter. In Kal's words; "The summed, rerouted bass and the LFE are subjected to the same low-pass filter." The updated BM plugin has the speaker channels and the LFE channel with independent low pass filters, so there's no chance of accidentally filtering out LFE content (plus you get the ability to do the speaker-sub crossover at different frequencies on different channels.)

Not sure if I quite follow what Kal complained about. Initially, it appears that the crossover from the mains to the sub was a single frequency and summed with the 0.1 LFE channel? This was subsequently fixed with the new plugin allowing individual crossover for each main channel which is then summed with the separate 0.1 LFE channel? Maybe a sketch is in order to clarify this.

Kal Rubinson's review of the NanoAVR-HD is here: Kal's Rubison's review of NanoAVR-HD . Refer to Note 3 which is was the complaint.

Hi Stephen, I will have reply in more detail later, but for now the diagram in the bass management app note may be helpful (re: sketch) - www.minidsp.com/applications/home-theate...ning/bass-management

(Previously there was a single LPF after the "+")

stephenting99 wrote:

john.reekie wrote:

Hi Stephen, where is that? I believe that's incorrect - Dirac Live should see the BM in the "feedback loop" otherwise it can't compensate for it. With BM after Dirac, the Dirac Live optimization will "see" the speaker channels as full range channels which it will EQ, IRC, etc. If you put the bass management first, then the bass management will "mess up" the results that Dirac accomplishes.

Hi John,

The comment came from Kal Rubinson about the NanoAVR-DL in AVS Forums thread.

Here ?

I think, as they say, the devil is in the details. First, let's confine the discussion only to parametric EQ (i.e. not Dirac type EQ). If one were to EQ the speaker channels without bass management turned on anywhere, and THEN turn on bass management "after" the EQ, then the total EQ would indeed be incorrect, because the low-frequency signals on each speaker channel either have no EQ applied at those frequencies, or the EQ has been done for the individual speaker, not for the sub.

If, however, one were to have bass management "after" the EQ already turned on, then do the EQ, the result would be correct. Your measurements and EQ would simply be based on "seeing" the speaker channel as a full range channel. If you're doing this manually, though, that would be a lot of extra work, as you would be doing the same (more or less) EQ (below say 80 Hz) on every single channel. For say a nanoAVR HD, that wouldn't be a very good way to do it.

So for a nanoAVR HD, you do the EQ for each channel, then you implement the bass management "before" the EQ and tweak the bass management settings - freq, slope, delay - to get a flat response through the crossover region.

Now if we look at Dirac, firstly it's automated, so there's no extra work in EQing with the bass management turned on downstream. Furthermore, Dirac is not only correcting for amplitude but also the impulse response. I don't know how much the sub crossover and attendant phase shift will affect the impulse response or how much Dirac can "undo" any such effect (something to try measuring when the opportunity arises) but if Dirac does have a useful effect in this regard then we want that crossover after the Dirac processor so that Dirac can compensate for it. Even if not, there are other likely issues it will correct as well, such as if the integration between the sub and the speaker isn't perfect on any channel.

As above, if you were to run the Dirac Live algorithm with BM in the AVR turned off, and then turn BM on, you would get an incorrect result. The downstream BM would need to be turned on when doing the measurements for Dirac Live.

If, on the other hand, the BM is before Dirac, then Dirac won't correct for any errors or anomalies the BM introduces. So you would have to make sure that the bass management produces a flat response. But that's still only amplitude and there's nothing you will be able to do about impulse/phase. By putting BM before the Dirac processor, my understanding is that you would both be limiting what Dirac can do and setting yourself up for extra work in the BM.

So, based on my understanding of how this all works, I do believe that "after" will work better for the nanoAVR DL

Regarding how Dirac works for REQ. In the measurement stage, does Dirac sends out the full range signal to each of the main channels (20-20kHz)? Or does it expect that each main channel to be capable of reproducing the full range signals? If in the AVR, the speakers are set to SMALL, with crossover to the sub, say the F3 is lower than 20Hz (as some sub are), what happens? Is there a brick wall and Dirac stops correction at 20Hz or continue to correct until the F3 is reached? What if the speakers set to LARGE in the AVR and the F3 is higher than 20Hz, will Dirac take this into consideration and cut off correction up to the F3, then route the lower frequencies to the sub?

Dirac Live will make a guess at a suitable target curve based on what it measures, and then you can adjust it yourself (per the manual). I'm not sure about the < 20 Hz question, from memory the low freq limit in the 2ch version is something about 15 Hz... I'd have to look. Or:

You might like to trial one of the computer-based solutions to learn more about how it works, download from dirac.se.

John,

Thanks for the reply. Yes the AVS forum link you provided is one of the discussions being carried out on the NanoAVR-DL.

Need to have a think about what you've written. There some very smart guys in AVS who disagree with what you've said. I intend to get some feedback on what they think is the proper way to REQ and implement bass management.

From what you're saying, the initial setup of the AVR seems to be important. That is having the AVR correctly gone through in setting up the levels, distances and crossover for each channel. Then setting each channel as SMALL in the AVR so that bass management is active. This I've done already and engaged the built in REQ - Audyssey MultiEQ.

I can do some frequency sweeps with and without bass management using REW. It would involve setting the speakers to SMALL, then LARGE.

I can also do some frequency sweeps with and without the Audyssey MultiEQ engaged with REW.

So from what you're saying, the downstream AVR needs have all the speakers SMALL. The built in REQ of Audyssey MultiEQ to OFF, as well as all other features on the AVR. Just the bass management feature is ON so that each channel can reproduce the full 20 to 20kHz signal range. Dirac will then send the full range signals to a channel and report back it's response. Once the correction filters are applied and played from the source, it will be as per the target curve.

The next question comes at the AVR. Most modern AVRs have sound matrix features such as Dolby PLx, DTS Neo, etc. There are other things such as dialogue lift (which seems to lift certain frequencies), center channel width, panaroma, etc. When these features are enabled, what happens to Dirac correction filters?

Hi Stephen, I don't see a disagreement. I outlined six different scenarios and explained the consequences of each.

I'm afraid I don't understand the sidetrack into Audyssey - I have no idea what it does.

Your second last paragraph sounds right to me. The question about matrix features is a good one, and I don't know anything about that. Wrt dialogue lift, I'd try doing that with the target curve. I guess this is all stuff that early adopters will be finding out - bear in mind nobody actually has one yet.

Thanks

Hi guys,

I've got a question regarding the DL trial version.

I would like to buy the new NanoAVR DL, but I can't understand how the DL trial version policy works.

If I buy the NanoAVR DL with the DL trial version I assume I can calculate the convolution filters and I can consequently feed them to the NanoAVR DL.

But after the trial period exprires, what is going to happen?

Will my NanoAVR DL still work?

What if I have to make a new measurement, let's say, one month after?

In a nutshell: in which case I can be happy with the trial versione and which case I have to buy the 250 USD license for DL?

Thanks in advance

Luigi

gigone wrote:

Hi guys,

I've got a question regarding the DL trial version.

I would like to buy the new NanoAVR DL, but I can't understand how the DL trial version policy works.

If I buy the NanoAVR DL with the DL trial version I assume I can calculate the convolution filters and I can consequently feed them to the NanoAVR DL.

But after the trial period exprires, what is going to happen?

Will my NanoAVR DL still work?

What if I have to make a new measurement, let's say, one month after?

In a nutshell: in which case I can be happy with the trial versione and which case I have to buy the 250 USD license for DL?

Thanks in advance

Luigi

Lungi,

The NanoAVR-DL hardware would still be working, just that Dirac REQ won't be. You can purchase the standard plugin that will give the same features as the NanoAVR-HD. You would the work done in Dirac and It would mean using REW and carrying out new set of measurements and applying PEQ filters.

Thank you for your prompt answer.

I'm not very confident with NanoAVR-HD standard pluging.

Can you kindly help me to understand more in details pro e cons (even under an economic perspective) wheter go on standard NanoAVR-HD plugin or stick on 250 DL.

I can't clearly spot the differences.

Luigi

gigone wrote:

I can't clearly spot the differences.

Hello Luigi, the two units are quite different in how they work. The nanoAVR HD uses parametric EQ, which is individual bands of EQ that you can set up manually, or do with the help of REW (room EQ wizard). You need to use REW or similar software to do acoustic measurements. It also has bass management. There are some app notes that describe how to use it here:

www.minidsp.com/applications/home-theate...ization-with-nanoavr
www.minidsp.com/applications/home-theate...ning/bass-management

The nanoAVR DL has the Dirac Live algorithm included and is more automated. The software that comes with it does the measurements for you (you have to place the microphone - UMIK-1 needed - in nine different locations). It's a more sophisticated type of correction than what you can do with parametric EQ. Also there is no bass management built in, you use the bass management in your receiver. There's no app note for the nanoAVR DL but here's one for the stereo version DDRC, the procedure will be similar but for 7.1 channels:

www.minidsp.com/applications/digital-roo...ries-getting-started

Hope that helps - ?

john.reekie wrote:

Hi Stephen, I don't see a disagreement. I outlined six different scenarios and explained the consequences of each.

I'm afraid I don't understand the sidetrack into Audyssey - I have no idea what it does.

Audyssey is another room equalization similar to Dirac. It's built in the AVR. I assume this has to be disabled for Dirac to work properly.

During initial setup, the Audyssey mic is placed at the listening position and the AVR will ping each channel. Based on the results, the individual speaker level and trims are set as well as the bass management for the crossover (pair for the front left, individual for the center and pair for the surrounds).

There are several nice features in Audyssey, including reference level offset to take into account the difference between TV shows, music and movies. Dynamic Volume which allows for day, evening and midnight listening by essentially compressing the dynamic range. Don't know if Dirac would implement these features?

Your second last paragraph sounds right to me. The question about matrix features is a good one, and I don't know anything about that. Wrt dialogue lift, I'd try doing that with the target curve. I guess this is all stuff that early adopters will be finding out - bear in mind nobody actually has one yet.

Thanks

Obtained feedback from an AVS member on what he thinks is the correct signal flow.

(1) Input signal ---> (2) bitstream decoding ---> (3) mix bus depending on the number of speakers/surround modes ---> (4) bass management ---> (5) EQ/delay/gain ---> (6) master volume/loudness compensation ---> (7) D/A ---> (8) output

The NanoAVR-DL will be in step (5). Obviously ahead of the bass management which is in step (4).

The matrix / up-mixing is done in step (3) and my understanding is that this where the DTS Neo X, Dolby ProLogic IIx would take a 2.0 signal and bring it up to 5.1/7.1

If the source has a 2-channel stereo soundtrack and sent as PCM to the NanoAVR-DL, the out is only sending 2.0 signals to the AVR. On the AVR if ?I engage DTS/Dolby Prologic IIx, would that mean only the front left and right channels have the Dirac correction while the remaining channels are not corrected since the bus mix is downstream of the NanoAVR-DL?

stephenting99 wrote:

Obtained feedback from AVS on what they think is the correct signal flow.

Ah. Did anyone explain why they think that?

Hi John,

I haven't received feedback on why. But I the signal flow seems logical.

If one chooses basic surround modes, i.e. 5.1/7.1 that would affect the bus mix. Some of the modern receivers have additional surround modes such as heights and wides in 9.1/11.1 configuration which requires up-mixing. This would have to be done before bass management and REQ is applied.

There could be another issue with down mixing of the source, say from 7.1 to 5.1 via lossless BR movies. My understanding is that the bus mix will make sure the information is not lost from back surround channels when it goes from 7.1 to 5.1. It's a bit unfortunate that I have only a 5.1 receiver so I rely upon this feature.

I initially thought it wasn't a problem, but thinking it through it could be an issue for me as I do like to up-mix the stereo source (2-channel) to 5.1 in either DTS or Dolby Prologic II. Most TV shows are 2-channel here in Hong Kong, there is no reference level and the commercials are annoying loud - very sad state for viewers.

The NanoAVR-DL would work for those have fixed input to fixed output arrangement with not much change in between. This way, Dirac will work well. The downstream AVR does the bass management, D/A conversion with volume control. The problem will come when the in between starts to change - like say different surround modes or features that's built into the AVR that was disabled during the Dirac setup, but then enabled during use. This could possibly make the Dirac EQ a bit pear shaped.

For straight movie watching via a BR player I don't think it's a problem, provided the downstream AVR is 7.1. For other sources, I'm not so sure.

Whilst the NanoAVR-DL is a great concept and Dirac is is certainly attractive, I'm not sure it's the right device for me.

Now if MiniDSP can make a pre/pro with Dirac - that would be a different story.

Hm. I would think downmix to 5.1 will be fine, if you run the calibration as 7.1 then the RL and RR will just be EQed the same as SL and SR. That's assuming a straight mix, which is what my AVR does anyway.

Upmix from stereo.... I dunno. I guess you'd have some sort of partial result, with the two fronts good and rest maybe not. Would it be worse than no DL at all? No idea. I guess it depends on a number of things, like how much gets sent to the other channels and how close the speakers are in design (i.e. if the same crossover in all then the phase/impulse response correction will be at least partially correct).

Interesting thoughts, thanks