Active Room Treatment (ART) by Dirac

[Oddball]

Many thanks to Kal and Timo for sharing their experience. I was hoping that Dirac, not Storm (and others), solved the one LFE sub issue. Hopefully D&M will follow Storm path in their implementation.

@Fidji - my experience with ART on Storm 12-18 mos ago is consistent with yours. It was sounding super tight but thin even there were 2 15" Perlisten subs and demo room was not that large. While I got to demo the unit in my space for a day, that was not really enough to get any real insight. Took a while to set it up and then it was just a struggle to figure out what is going on.

The idea that a bunch of 6.5" drivers or 8" drivers could contribute to LFE output is not a bad one, provided these drivers are top notch and adequately powered. It is true that they will not create a miracle, but could fill in some gaps in the sub response and potentially add to SPL in the room where positioning will not create cancelations that are greater than additions. As noted in my previous post, my LFE distribution across 8 bed channels is working nicely, given that resources are there and positioning turned out to be net positive. I rarely listen to more than -10dB to reference so peaks are 95dB for bed channels, which my speakers can take for their in-room extension without unusual distortion or clipping. While I don't run really big amps for surrounds (130Wpc into 8ohm), each pair of speakers has their own stereo amp, and combination of capacitors, power supply and raw power are sufficient to deliver these peaks without any issues.

 

[Fidji]

That is currently what I do.

Kal, question - probably not for your use for MCH music - but more for Movie enthusiasts - what is Seat to Seat consistency of ART setup? Is there any deliberate trade-off between MLP quality vs wider area coverage?

No one is saying all speakers combined will result in more dBs in room - I think what we're trying to say is a single sub supported with other speakers will result with no nulls and flat response.

Mind that cancelation waves are done at lower SPL - so your towers don't need same woofer area as your sub - math says to achieve 20dB cancelation wave (max ART can do if not mistaken) for a signal of 100dB you would need signal at 94dB (6dB lower for 20dB of cancelation) - most towers can do that albeit at higher distortion.

Logarithmic math is clear [I hope] to everybody on this forum. I pointed to "mains acting as LFE" part.
1) So your tower in example needs to handle - a) cancellation signal b) LFE signal to support sub c) its own bass signal.
2) If you use EQ you will loose headroom on top - anywhere up to 10dB - this is important to take into account.
3) your tower will not help you where you need it - in sub 50Hz frequencies

This is example of quite potent sub, you still need 2 of them to get to reference levels at 20Hz [but probably 4 if you need to EQ them]

or my sub [dark blue line] - have 8 of them, will add another 2 + have approx 10dB room gain below 25Hz

As you can see there is no problem with available output above 40Hz, so theoretically in the area are where big towers can really help you, so there your sub(s) are on their own to support themselves. And below 40Hz is the area that really matters to get "big sound". So no way around having 2-3-4-X subs in order to get top performance.

The idea that a bunch of 6.5" drivers or 8" drivers could contribute to LFE output is not a bad one, provided these drivers are top notch and adequately powered. It is true that they will not create a miracle, but could fill in some gaps in the sub response and potentially add to SPL in the room where positioning will not create cancelations that are greater than additions

This I can agree - but you need to have very specific drivers - that can handle high SPL without distortion - I can think of Purifi Ushindi as good example, but there you pay premium money. There is a good reason, why top HT speakers use 8-10-12in drivers and still cross them over at 80Hz. If you want undistorted dynamics there is no other way.

 

[OCA]

In most of the commercial subs you will hit limiter settings much sooner than Dirac 20Hz brickwall if you want to get anywhere near reference levels.

There used to be a 16Hz hpf in A1 Evo and I remember all the reactions I got from the infra-bass crowd. Some people (definitely not me, I am quite content with above 20Hz) pay a lot of money for their 12Hz capable subs and they claim to "feel" the difference. I have read about users not activating ART so as to avoid that 20Hz brickwall.

 

[Daka]

Kal, question - probably not for your use for MCH music - but more for Movie enthusiasts - what is Seat to Seat consistency of ART setup? Is there any deliberate trade-off between MLP quality vs wider area coverage?


Logarithmic math is clear [I hope] to everybody on this forum. I pointed to "mains acting as LFE" part.
1) So your tower in example needs to handle - a) cancellation signal b) LFE signal to support sub c) its own bass signal.
2) If you use EQ you will loose headroom on top - anywhere up to 10dB - this is important to take into account.
3) your tower will not help you where you need it - in sub 50Hz frequencies

This is example of quite potent sub, you still need 2 of them to get to reference levels at 20Hz [but probably 4 if you need to EQ them]
View attachment 457182
or my sub [dark blue line] - have 8 of them, will add another 2 + have approx 10dB room gain below 25Hz
View attachment 457189

As you can see there is no problem with available output above 40Hz, so theoretically in the area are where big towers can really help you, so there your sub(s) are on their own to support themselves. And below 40Hz is the area that really matters to get "big sound". So no way around having 2-3-4-X subs in order to get top performance.



This I can agree - but you need to have very specific drivers - that can handle high SPL without distortion - I can think of Purifi Ushindi as good example, but there you pay premium money. There is a good reason, why top HT speakers use 8-10-12in drivers and still cross them over at 80Hz. If you want undistorted dynamics there is no other way.

Shouldn't preventing cancelations/room modes be treated as supporting LFE? I would think so. So imagine a subwoofer in anechoic chamber - perfect response throughout - you wouldn't need multi sub setup would you other than potentially increasing SPL.
So mains supporting subwoofer to remove room effects rather than the way you are thinking - giving similar output to subwoofer - no need for that at all.
All in all what I hope for is less subs required for smoother tighter bass - perhaps even with one, but will have to wait and see its limitations.

 

[Fidji]

There used to be a 16Hz hpf in A1 Evo and I remember all the reactions I got from the infra-bass crowd. Some people (definitely not me, I am quite content with above 20Hz) pay a lot of money for their 12Hz capable subs and they claim to "feel" the difference. I have read about users not activating ART so as to avoid that 20Hz brickwall.

Proud member of "single digit Hz crowd here"

But honestly - for me all this is about headroom and distortion. If your setup is able to handle 12Hz at reference levels, there is high probability that system will have ample headroom everywhere and you will never enter any compression/distortion territory. E.g. - like probably most of us here - I never watch movies at "reference levels" because is too loud. This is why I have speakers able to play f-6 at reference at 30Hz and still cross them over at 80. My HT is build around "Excess and Overkill" design approach.

What I am trying to somehow say - I can see here some people thinking of ART as some magic wand, that will make ****** setup sound great. It won't, it will still sound ******, but without so many room resonances. You still need to have high quality speakers, placed half correctly to get good results.

As you are from Germany - did you had a chance to ever visit Ascendo [AIA] showroom? This usually settles the discussion about what is possible to feel or not.

Shouldn't preventing cancelations/room modes be treated as supporting LFE? I would think so. So imagine a subwoofer in anechoic chamber - perfect response throughout - you wouldn't need multi sub setup would you other than potentially increasing SPL.
So mains supporting subwoofer to remove room effects rather than the way you are thinking - giving similar output to subwoofer - no need for that at all.
All in all what I hope for is less subs required for smoother tighter bass - perhaps even with one, but will have to wait and see its limitations.

Physics does not work that way, no idea, whether you had a chance to visit anechoic chamber. If you have a chance, you can do an experiment - get your speakers outside and play some bass heavy music. And compare it with what you hear in your room.

ART is not something new in the principle. There are several other ways of achieving the same goal - SBA, DBA, Waveforming - where the end result is the same as you can see on available ART measurements - controlled, even decay and flat frequency response [if you choose flat].

They all have one thing in common - they require LOT of subs to work properly [in terms of required subwoofer output]. And I have heard 2 ART installations - and they exhibited the same behavior.

 

[Oddball]

Proud member of "single digit Hz crowd here"

But honestly - for me all this is about headroom and distortion. If your setup is able to handle 12Hz at reference levels, there is high probability that system will have ample headroom everywhere and you will never enter any compression/distortion territory. E.g. - like probably most of us here - I never watch movies at "reference levels" because is too loud. This is why I have speakers able to play f-6 at reference at 30Hz and still cross them over at 80. My HT is build around "Excess and Overkill" design approach.

What I am trying to somehow say - I can see here some people thinking of ART as some magic wand, that will make ****** setup sound great. It won't, it will still sound ******, but without so many room resonances. You still need to have high quality speakers, placed half correctly to get good results.

ART is not something new in the principle. There are several other ways of achieving the same goal - SBA, DBA, Waveforming - where the end result is the same as you can see on available ART measurements - controlled, even decay and flat frequency response [if you choose flat].

They all have one thing in common - they require LOT of subs to work properly [in terms of required subwoofer output]. And I have heard 2 ART installations - and they exhibited the same behavior.

Looks like you do have great gear. I would assume that you use Waweforming given Trinnov and 8 subs and likely happy with it? Are you planning to try/switch to Storm?

I never had particular interest in going subsonic, so built my system around 20hz response which I also have to start rolling off at 30hz as (for now) using system in a multi purpose room where sub 30hz frequencies start wrecking havoc at high SPL (say 100 dB plus).

As you note, ART is approaching an old problem from a different angle, but my hope was always that it will help reduce hardware requirements compared to e.g. DBA and especially Waweforming. I don't think that many people here are chasing 115dB response at 20hz, but really expect to get clear response throughout the range and controlled decay from a 2 subs, 2 towers and remaining bookshelves up to the loud levels such as -10dB or -15dB to reference. This would in turn reduce peaks to more manageable 105 or 100dB for the subs and 85 or 80dB for the mains. If ART beats DLBC in these circumstances by a significant margin - then it will be a good solution for many.

My expectations are little different, but enough gear to play with ART if I feel like it. Probably won't be an early adopter though - to make sure I know exactly what I am getting into. Don't feel like spending months and months tweaking (yet again).

 

[Fidji]

Looks like you do have great gear. I would assume that you use Waweforming given Trinnov and 8 subs and likely happy with it? Are you planning to try/switch to Storm?

I never had particular interest in going subsonic, so built my system around 20hz response which I also have to start rolling off at 30hz as (for now) using system in a multi purpose room where sub 30hz frequencies start wrecking havoc at high SPL (say 100 dB plus).

Just as small interestign topic - one thing that DBA and later Waveformning helped me to achieve, is that I can go around 10dB louder before I start to bother my neighbours - I live on top floor in the penthouse, and there is very friendly and nice family below me with small children, so I do not want to be asshole and I checked with them. I can go -5dB reference in the evening and they hear nothing as WF is really cancelling all the standing waves. I expect to see similar effect via ART, once you kill resonances, your neighbors will thank you ;-).

Re Storn - no, not interested - what I am looking for is to build another AV setup in the room, where I do not have chance to do proper Waveforming, so this is why ART is of interest to me. It would save me a lot of trouble, if I could just place 4-5-6 subs randomly in-wall and forget them and not bother about specific placement for "cylindrical WF". So kind of "good enough" with some design in wall speakers [Perlisten? Focal?] and probably 115 TCL screen. I had a chance to witness similar setup with ART and it was very nice. But subs wer 4 21 in drivers from YG acoustics ;-), so not my desired price bracket ....

I would go either for a) AV10 and ART or b) Trinnov Altitude 16 and cylindrical WF. Storm - don't see the value proposition, still Dirac thing with couple of bells and whistles for the price of Trinnov. Except of Dante/AES67. but I want to keep the setup simple - in rack PrePro, multichannel amps, sub amps, Kaleidascape player and go with wires.

ART vs WF - I think re placement - absolutely ART is much more flexible and less demanding, also re subwoofer power needed I would expect ART to need less subs to get to similar SPL above 30Hz. Below 30Hz [depending on the size of the room] WF switches to Pressurization Mode, generally pumping the air. Need to say it is quite addictive sensation. Once you get used to it, you start to realize something is missing elsewhere.

 

[Kal Rubinson]

Kal, question - probably not for your use for MCH music - but more for Movie enthusiasts - what is Seat to Seat consistency of ART setup? Is there any deliberate trade-off between MLP quality vs wider area coverage?

I cannot offer much because my setup is just for me: one seat. I can conjecture that it is good in the vicinity as I often draw another chair alongside for me when I seat a guest in the MLP. OTOH, the bass does sound lumpy when I listen from my desk in an adjacent room.

 

[Oddball]

Just as small interestign topic - one thing that DBA and later Waveformning helped me to achieve, is that I can go around 10dB louder before I start to bother my neighbours - I live on top floor in the penthouse, and there is very friendly and nice family below me with small children, so I do not want to be asshole and I checked with them. I can go -5dB reference in the evening and they hear nothing as WF is really cancelling all the standing waves. I expect to see similar effect via ART, once you kill resonances, your neighbors will thank you ;-).

Re Storn - no, not interested - what I am looking for is to build another AV setup in the room, where I do not have chance to do proper Waveforming, so this is why ART is of interest to me. It would save me a lot of trouble, if I could just place 4-5-6 subs randomly in-wall and forget them and not bother about specific placement for "cylindrical WF". So kind of "good enough" with some design in wall speakers [Perlisten? Focal?] and probably 115 TCL screen. I had a chance to witness similar setup with ART and it was very nice. But subs wer 4 21 in drivers from YG acoustics ;-), so not my desired price bracket ....

I would go either for a) AV10 and ART or b) Trinnov Altitude 16 and cylindrical WF. Storm - don't see the value proposition, still Dirac thing with couple of bells and whistles for the price of Trinnov. Except of Dante/AES67. but I want to keep the setup simple - in rack PrePro, multichannel amps, sub amps, Kaleidascape player and go with wires.

ART vs WF - I think re placement - absolutely ART is much more flexible and less demanding, also re subwoofer power needed I would expect ART to need less subs to get to similar SPL above 30Hz. Below 30Hz [depending on the size of the room] WF switches to Pressurization Mode, generally pumping the air. Need to say it is quite addictive sensation. Once you get used to it, you start to realize something is missing elsewhere.

And I thought that I was the worst neighbour on ASR . Definitively true that even with primitive (aka not fully canceling) DBA I did spare the neighbours a whole lot of grief and able to do higher SPL than before. Unfortunately not in penthouse, and the only neighbours occasionally complaining are the ones floor up. Floor down is my tenant and he never complains. Seems like the mass of the building below me is sufficient to push the problems to higher flors (18-25).

I did not have Trinnov, although on my bucket list, but can definitively understand the pressurisation effect. My smaller HT is in a smaller room and the bass pressure in there is bordering insane despite limited resources (see signature). What you noted about the towers not being able to contribute is generally true, but some towers in small-er rooms will actually move air upon a gunshot that you will feel (air movement) at MLP. I ended up with Klipsch towers in that setup for a variety of reasons so while not ideal, the bass from those is really like pop candy on steroids for HT. The rest is not so great, but hey, they are still fun in their own cheap way. Surf&Turf is obviously great, but burgers also sometimes taste pretty good.

 

[ban25]

One of my concerns with ART is that it seems like limiting LFE to a single sub would result in uneven frequency response across multiple seating positions even if it is excellent at the MLP. With DLBC and multiple subs, I have excellent, even bass across the room regardless of seating position. I'd also be concerned about potentially being able to localize some of the bass in an ART setup as my subwoofers are placed quite far apart.

 

[Oddball]

I don't think we know enough about what ART actually does, unfortunately. Even the "single LFE sub" is still, at least to me, a mystery.

If one sub plays full LFE according to its capabilities and is EQd to take out the peaks, and e.g. second sub plays only the parts that are going to fill in the nulls or lower response in specific FQ range compared to the first sub, that might not be so far off from the other solution where all subs play LFE and then are EQd as a group. In fact it might conceptually be better and easier to implement. Would be even (way) better if the algo could account for more than just filling nulls, so that the net difference between the two outputs could both even out the response and increase the SPL of the LFE - with the second sub just playing the signals that are canceling and additive to the first sub, so not really full range.

If the case is that one sub plays LFE and the others are just canceling - yeah that is a significant concern and hopefully D&M can follow Storm implementation to enable different solutions.

Broad statements made by Dirac are not really sufficient to understand what is going on, and while user reviews are helpful, have not seen anything that would go to this level of detail. But as always, ready to learn more about this new and exciting product that has been on the shelves for a mighty long time .

 

[Kal Rubinson]

One of my concerns with ART is that it seems like limiting LFE to a single sub would result in uneven frequency response across multiple seating positions even if it is excellent at the MLP.

Well, if you "support" the LFE-designated sub with other subs (or, even, some potent main speakers), that may not be an issue.

If one sub plays full LFE according to its capabilities and is EQd to take out the peaks, and e.g. second sub plays only the parts that are going to fill in the nulls or lower response in specific FQ range compared to the first sub, that might not be so far off from the other solution where all subs play LFE and then are EQd as a group. In fact it might conceptually be better and easier to implement.

I've done it both ways and prefer the single LFE-designated sub with support from others. OTOH, rather than recommend this outright, I will recommend experimentation. Also, my application is music, not HT, so LFE itself is not typical for me.

 

[Oddball]

Thanks Kal - much appreciated. How do you actually do it both ways though? By designating subs as separate groups and assigning LFE function to both if you want both to play LFE (and then including the other sub in the respective support groups for the subs)? As opposed to just designating one as LFE and the other one just as a support?

As others noted, for HT SPL is also important and in larger rooms it might require multiple subs so that overall SPL is increased, not just that FQ response is flattened and decay times reduced.

 

[Kal Rubinson]

How do you actually do it both ways though? By designating subs as separate groups and assigning LFE function to both if you want both to play LFE (and then including the other sub in the respective support groups for the subs)?

I do it outside of DL. My setup is on a WinPC with Jriver whose output goes (via Ravenna) to a Hapi II DAC. Jriver provides full mixing/routing among all channels and permits me to route LFE (or anything else) to any or all outputs. I bellieve that Storm Audio has similar routing options.

Downstream, DL-ART offers additional options for support. Overall, I can then generate DL-ART filters to suit and compare and created configurations with a click.

 

[peng]

I don't think we know enough about what ART actually does, unfortunately. Even the "single LFE sub" is still, at least to me, a mystery.

If one sub plays full LFE according to its capabilities and is EQd to take out the peaks, and e.g. second sub plays only the parts that are going to fill in the nulls or lower response in specific FQ range compared to the first sub, that might not be so far off from the other solution where all subs play LFE and then are EQd as a group. In fact it might conceptually be better and easier to implement. Would be even (way) better if the algo could account for more than just filling nulls, so that the net difference between the two outputs could both even out the response and increase the SPL of the LFE - with the second sub just playing the signals that are canceling and additive to the first sub, so not really full range.

If the case is that one sub plays LFE and the others are just canceling - yeah that is a significant concern and hopefully D&M can follow Storm implementation to enable different solutions.

Broad statements made by Dirac are not really sufficient to understand what is going on, and while user reviews are helpful, have not seen anything that would go to this level of detail. But as always, ready to learn more about this new and exciting product that has been on the shelves for a mighty long time .

I am not sure if I follow, from what I understood DL's ART, it probably does both boost, cuts, and phase shifts to all the speakers, sub (s) included whether there are 1,2,...4 or more subs. If that's the case, then it is like infinitely variable depending on the moment by moment contents driven, and DL just try and analyze what action to take based on the info collected during the measuring process. In theory, it should work well, likely equal/better to/than Trinnov's, as long as all the speakers have adequate response to the bass range, and have more than enough current capabilities.

 

[Oddball]

I think you are not alone in not following exactly what would be going on. If based on the input from the people using Dirac, only one sub plays LFE original signal, the question is what are other subs (let's put other speakers on the side for now) really doing. It seems that Kal is getting around "that" through software he uses in his setup and Storm has their own solution to engage more subs as LFE subs.

I tried to break down "that" in my previous post with the point of will e.g. 4 subs generate higher SPL as in traditional setup or will it all be levelled to the output of the main LFE sub. Despite the improvement in FQ response and decay, which is evident from many charts shared, SPL is another really important point for HT and not sure I have seen anything for that particular shade of grey. The only usable answer is that multiple subs need to be SPL additive for HT use for any larger room.

 

[peng]

I think you are not alone in not following exactly what would be going on. If based on the input from the people using Dirac, only one sub plays LFE original signal, the question is what are other subs (let's put other speakers on the side for now) really doing. It seems that Kal is getting around "that" through software he uses in his setup and Storm has their own solution to engage more subs as LFE subs.s

Thank you for further clarification on your point, though I probably still don't understand fully about the potential SPL effects of the scenarios. Regardless, I would think this is a case by base thing, for example, your AV10 has 4 independent subwoofer outputs so all of them will play the LFE channel but each will be "corrected" as DL sees fit. Who are those people using Dirac that have only one sub plays LFE original signal? As to what are the other subs really doing, then it would be a good question, but I just can't understand why they wouldn't also play the LFE channel.

I tried to break down "that" in my previous post with the point of will e.g. 4 subs generate higher SPL as in traditional setup or will it all be levelled to the output of the main LFE sub.

Can't really know but the first question above needs to be answered first, otherwise it would be unknowable, logically speaking.

Despite the improvement in FQ response and decay, which is evident from many charts shared, SPL is another really important point for HT and not sure I have seen anything for that particular shade of grey. The only usable answer is that multiple subs need to be SPL additive for HT use for any larger room.

Agreed, but surely that should be the case that multiple subs will product more SPL overall, but the combined SPL will not be higher than, as the RC (DL ART in this case) would have trimmed the levels up such that they overall effect will not become bass heavy, iow, if a flat target curve is used, the multiple subs will produce the same SPL as if only one sub (a capable one) is used, that is, whether it is a 7.1.6 or 7.4.6, the SPL of the bass range will be the same, all else being equal, obviously.

 

[Oddball]

Thank you for further clarification on your point, though I probably still don't understand fully about the potential SPL effects of the scenarios. Regardless, I would think this is a case by base thing, for example, your AV10 has 4 independent subwoofer outputs so all of them will play the LFE channel but each will be "corrected" as DL sees fit. Who are those people using Dirac that have only one sub plays LFE original signal? As to what are the other subs really doing, then it would be a good question, but I just can't understand why they wouldn't also play the LFE channel.

Can't really know but the first question above needs to be answered first, otherwise it would be unknowable, logically speaking.

Agreed, but surely that should be the case that multiple subs will product more SPL overall, but the combined SPL will not be higher than, as the RC (DL ART in this case) would have trimmed the levels up such that they overall effect will not become bass heavy, iow, if a flat target curve is used, the multiple subs will produce the same SPL as if only one sub (a capable one) is used, that is, whether it is a 7.1.6 or 7.4.6, the SPL of the bass range will be the same, all else being equal, obviously.

As I understand, the issue with single LFE sub is present even with multiple independent sub outputs. That is apparently (based on other member's input) why some software solutions or Storm implementation are "getting around it".

What is "it" - not sure. Dirac says it is "support" but would be good to understand what kind of support that is. I can say from experience that "support" is the most common misunderstanding in many relationships so best defined in detail.

As far as conventional setups, calibration is one thing and maximum output and compression test and a separate issue. Calibrating at 85dB will work quite well in most cases, but it will depend of gear and room if you can reach reference 115dB for HT at MLP for a given frequency. My subs are close to that individually at 3m distance at 50hz, a bit lower at e.g. 20hz, in open outside space scenario (aka Audioholics measurements). Peaks are easy to equalize, but nulls are coming at higher price, as EQ will pull down the output for the most part rather than trying to fill deep nulls. Also, having overall headroom is what most advanced setups are aiming for so you don't have to push relatively high distortion at maximum output. Furthermore, common EQ curve is to boost the low end, at which point 115dB might become 120dB or more, depending on the curve used.

This is a really confusing topic - but I am sure I understand most of it in the conventional setup as have been doing this for really long time and have tried all there is - except ART and Trinnov. My ART adventure was for a day and really can't say I got anything useful out of it.

 

[ban25]

Thank you for further clarification on your point, though I probably still don't understand fully about the potential SPL effects of the scenarios. Regardless, I would think this is a case by base thing, for example, your AV10 has 4 independent subwoofer outputs so all of them will play the LFE channel but each will be "corrected" as DL sees fit. Who are those people using Dirac that have only one sub plays LFE original signal? As to what are the other subs really doing, then it would be a good question, but I just can't understand why they wouldn't also play the LFE channel.

Can't really know but the first question above needs to be answered first, otherwise it would be unknowable, logically speaking.

Agreed, but surely that should be the case that multiple subs will product more SPL overall, but the combined SPL will not be higher than, as the RC (DL ART in this case) would have trimmed the levels up such that they overall effect will not become bass heavy, iow, if a flat target curve is used, the multiple subs will produce the same SPL as if only one sub (a capable one) is used, that is, whether it is a 7.1.6 or 7.4.6, the SPL of the bass range will be the same, all else being equal, obviously.

If you enable ART in a system with 4 independent subwoofers, you give up LFE output on 3 of those. Only a single sub will play LFE, the rest, I assume, will merely play low level support frequencies. That's a pretty significant limitation for HT in a large space with multiple seating positions.

 

[alvigg]

If you enable ART in a system with 4 independent subwoofers, you give up LFE output on 3 of those. Only a single sub will play LFE, the rest, I assume, will merely play low level support frequencies. That's a pretty significant limitation for HT in a large space with multiple seating positions.

The measurements can be taken over a wide range to even out the room. The rest, including speakers that play between 20-150 Hz will generate whatever is needed to downplay resonances (cancellation waves like in noise cancelling headphones) or additions where there are nulls.