Active Room Treatment (ART) by Dirac

[abdo123]

Your quote has something I did not write.

Sorry, fixed that.

 

[neRok]

Can you explain to me how mixed phase filters can help when the sound source is not producing any sound at all at the SBIR frequency?

The speaker is producing sound, the problem is that the sound it is currently producing is perfectly cancelled by a first reflection of sound it has previously played. See "Monopole located at the first null from the left wall". If you phase shift during the tone, the current sound will be out of phase with the reflection, so you can get some sound back.

Edit: Say the speaker is 700mm from the front wall, which equates to an SBIR cancellation at 122Hz. Using a cosine wave as an example (ie, starting at + peak), after playing 1/4 of a tone the wave moves 1/4 length=700mm from the speaker. This means the forward wave is 700mm in to the room, and the rearward wave is at the back wall, and that the speaker is currently playing the 0 part of the tone. Then after another 1/4 of a tone, the forward wave is now 1.4m in to the room (a full 1/2 cycle) whilst the rearward wave has reflected and means the + peak is now at the speaker, whilst at the same time the speaker is now playing the - peak. So from that point on, the original rearward + peak wave travels on top of the new forward - peak wave, and so they cancel each other. But if you use an IIR filter with -gain and high Q value then you can cause a phase shift, so that the speaker now plays a second -peak, along with some post-ringing, like I showed here.

Edit2: Here's some pictures I just made that might help explain. I used a "ghost" speaker as the reflection, to make it easier to visualise.


You can see the first 2 examples are a normal SBIR issue. Blue_1 moves forward on its own, but Blue_2 are cancelling each other. Eventually Blue_3 comes through with power.

The last 3 examples are what would happen with IIR filter (or FIR that replicates the post-ringing). Green_1 starts unencumbered, but is slightly weaker than Blue_1 due to the EQ filter. Green_2 has a little power towards the purple peak. Green_3 is now 2 phases in same direction, so they sum together to make a bit of power. Green_4 is out of phase but sums slightly towards purple.

So at all moments of the IIR shifted wave there is some power at the peaks.

 

[seedragon]

Yes, Storm and Trinnov (and JBL), seem to own the premium end of this market...

Many of us are hoping to see ART on AVR's like the X3800 and RZ70, bringing the tech to a much larger (more budget oriented!) market ...

There has been no hint from the house of Harman with regards to ART so far.... (unless I missed something) - I would be surprised for ART not to be available on ARCAM/JBL kit...

Yeah. I don't see a way for Dirac to make a reasonable return on their R&D unless ART gets licensed by more manufacturers.

I saw this thread saying ART is running on beta FW for a Denon X6800. Hoping that's not leftover code that'll be disabled or removed at a later date. Dirac ART is now running on beta FW for Denon Xx800H AVRs!

 

[dlaloum]

Yeah. I don't see a way for Dirac to make a reasonable return on their R&D unless ART gets licensed by more manufacturers.

I saw this thread saying ART is running on beta FW for a Denon X6800. Hoping that's not leftover code that'll be disabled or removed at a later date. Dirac ART is now running on beta FW for Denon Xx800H AVRs!

Right now, I expect most ART deployments will be as optional licences purchased direct from Dirac...

It would be nice to see ART as an inclusion, but I doubt that will happen any time soon (at least at the mid to lower end of the market)

 

[abdo123]

The speaker is producing sound, the problem is that the sound it is currently producing is perfectly cancelled by a first reflection of sound it has previously played. See "Monopole located at the first null from the left wall". If you phase shift during the tone, the current sound will be out of phase with the reflection, so you can get some sound back.

Edit: Say the speaker is 700mm from the front wall, which equates to an SBIR cancellation at 122Hz. Using a cosine wave as an example (ie, starting at + peak), after playing 1/4 of a tone the wave moves 1/4 length=700mm from the speaker. This means the forward wave is 700mm in to the room, and the rearward wave is at the back wall, and that the speaker is currently playing the 0 part of the tone. Then after another 1/4 of a tone, the forward wave is now 1.4m in to the room (a full 1/2 cycle) whilst the rearward wave has reflected and means the + peak is now at the speaker, whilst at the same time the speaker is now playing the - peak. So from that point on, the original rearward + peak wave travels on top of the new forward - peak wave, and so they cancel each other. But if you use an IIR filter with -gain and high Q value then you can cause a phase shift, so that the speaker now plays a second -peak, along with some post-ringing, like I showed here.

Edit2: Here's some pictures I just made that might help explain. I used a "ghost" speaker as the reflection, to make it easier to visualise.
View attachment 314514 View attachment 314513

You can see the first 2 examples are a normal SBIR issue. Blue_1 moves forward on its own, but Blue_2 are cancelling each other. Eventually Blue_3 comes through with power.

The last 3 examples are what would happen with IIR filter (or FIR that replicates the post-ringing). Green_1 starts unencumbered, but is slightly weaker than Blue_1 due to the EQ filter. Green_2 has a little power towards the purple peak. Green_3 is now 2 phases in same direction, so they sum together to make a bit of power. Green_4 is out of phase but sums slightly towards purple.

So at all moments of the IIR shifted wave there is some power at the peaks.

This is … kind of brilliant.

Not something i expect any Dirac module other than ART to do but it’s still very innovative.

You’re losing a lot of output btw, and SBIR nulls are rarely really “in ideal conditions” but it’s nice to know this is in your arsenal.

 

[pogo]

To all those who have already performed ART measurements with REW, ... in their own listening room:
Have you ever explored your system limits, i.e. not only at one volume, but also sometimes 10dB above or below, etc.?
I expect worse results in the future, for example when ART is to be used on 'smaller' AVRs.

 

[Curvature]

I expect worse results in the future, for example when ART is to be used on 'smaller' AVRs.

Why?

 

[seedragon]

Is there any data on the amount of additional amplifier power an ART-enabled system might need over a "passive" approach?

 

[pogo]

Why?

An active room treatment cannot be compared with a passive one. Further sources of error can arise here.
ART assumes that there is no compression of the loudspeakers even at louder levels, (weak) power supplies do not go to their knees, DSP-controlled subs do not cut back the lower frequencies at high levels, ...
It could even be that a support speaker outputs a correct correction signal, but the speaker to be supported incl. power amplifier stumbles, ...
I would be interested in a measurement at 100/110dB (unweighted). These are the short-term peaks that are present in my surround setup at my listening position. However, I would try to approach these levels slowly

 

[Curvature]

An active room treatment cannot be compared with a passive one. Further sources of error can arise here.
ART assumes that there is no compression of the loudspeakers even at louder levels, (weak) power supplies do not go to their knees, DSP-controlled subs do not cut back the lower frequencies at high levels, ...
It could even be that a support speaker outputs a correct correction signal, but the speaker to be supported incl. power amplifier stumbles, ...
I would be interested in a measurement at 100/110dB (unweighted). These are the short-term peaks that are present in my surround setup at my listening position. However, I would try to approach these levels slowly

I agree with all of that, since correction measurements are usually taken at lower levels, but why are lower level AVRs not likely to perform as well?

Are you pointing to less processing power or pointing to the problems around limited output power/voltage and how ART would react to a clipped signal?

 

[abdo123]

An active room treatment cannot be compared with a passive one. Further sources of error can arise here.
ART assumes that there is no compression of the loudspeakers even at louder levels, (weak) power supplies do not go to their knees, DSP-controlled subs do not cut back the lower frequencies at high levels, ...
It could even be that a support speaker outputs a correct correction signal, but the speaker to be supported incl. power amplifier stumbles, ...
I would be interested in a measurement at 100/110dB (unweighted). These are the short-term peaks that are present in my surround setup at my listening position. However, I would try to approach these levels slowly

I rather have a better experience at 85dB over a better experience at 100dB any time of the day personally.

 

[pogo]

This is quite simple. Listen to a full range speaker on an ordinary AVR and compare the reproduction with a good external power amplifier. In the second case you can hear your speakers breathe properly

 

[Curvature]

This is quite simple. Listen to a full range speaker on an ordinary AVR and compare the reproduction with a good external power amplifier. In the second case you can hear your speakers breathe properly

...

If you aren't exceeding the linear operating range of your gear there will be no problems.

 

[Magnus]

This is quite simple. Listen to a full range speaker on an ordinary AVR and compare the reproduction with a good external power amplifier. In the second case you can hear your speakers breathe properly

If I wanted to read Stereo Review or Stereophile like claims of magical sound just because they're separates, I'd dig out some old magazines....

In the real world, the load matters, for instance as does the amplifiers in question.

The Yamaha RXV-659 AVR got stellar amp section reviews back in 2006. You can pick these up for around $150 each used. That's 120W into 8 ohms each x2 real world measurements (https://www.audioholics.com/av-receiver-reviews/yamaha-rx-v659)

Even if you bought 8 of these, you could get 120Wx16 for about $1200. Compare that to what Marantz wants for a 16ch Amp 10 ($7000). Three could get you around 50W per channel continuous for 5 channels driven at max for a 9.1.6 setup for a mere $450 used total. For most speakers with Atmos programming across 15 speakers, that's plenty.

Oh, but I guess they won't "breathe properly".

 

[tehas]

Its October ! Any non-Storm announcements?
@Flak when can we get ART on PC?

 

[seedragon]

Its October ! Any non-Storm announcements?
@Flak when can we get ART on PC?

I'm anxious for news, as well. Crossing fingers for ART on JBL Synthesis!

 

[Inertia]

I'm anxious for news, as well. Crossing fingers for ART on JBL Synthesis!

I heard whispers months ago that they would bring it to the Marantz AV10 - has anyone heard anything about this yet? I also heard that ART was going to be on Storm until November but was hoping we'd get at least an announcement about the other platforms they plan on supporting by now.

 

[tehas]

FWIW, part of my eagerness is because I'm stingy. I don't have any kind of Dirac Live, but I want to purchase Live, DLBC and ART as a bundle, with the hope of non-trivial savings when purchased as such.

 

[seedragon]

I heard whispers months ago that they would bring it to the Marantz AV10 - has anyone heard anything about this yet? I also heard that ART was going to be on Storm until November but was hoping we'd get at least an announcement about the other platforms they plan on supporting by now.

Dirac's own website still says October, so I hope we'll see something within a few days. One would think we would have heard from several manufacturers already since they're always trying to gain a competitive edge but maybe ART was harder to integrate than they thought. Or ART required more power than their AVRs could produce.

 

[ban25]

Dirac's own website still says October, so I hope we'll see something within a few days. One would think we would have heard from several manufacturers already since they're always trying to gain a competitive edge but maybe ART was harder to integrate than they thought. Or ART required more power than their AVRs could produce.

More likely, the terms of the licensing agreement for integrators includes an NDA that doesn't lift until after the exclusivity period with StormAudio has run its course.