Linn Owners

The 4 Hour Transformation Of A Linn System

Elad Repooc

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Go into SOV1 and create a room with speakers. Calculate room modes. Then change the speaker positions. The mode will not change at all.
This is where as I recall (I haven't messed with Sov1 for years) my experience is much different, it may be the case in certain systems perhaps but that's not how I remember things.

 

sunbeamgls

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An attempt to clarify a few things:

 - SOv1 did not calculate the cubic air volume (affected by temperature and humidity I might add) of the room and how sound at all frequencies is energizing the space in the room. It only calculated length, width, and height modes and offered suggested cuts for frequencies below 200Hz based on the position of the given speaker in the given room dimensions - which were explicitly something that still needed to be further adjusted and verified by ear. Not every SOv1 calculation could or would be very accurate, as admitted by Linn back then.

- In addition to calculating the cubic air volume of the space based on the provided input, and in general performing a much more advanced calculation of the given room dimensions, materials coefficients, etc. (which is why it moved to the cloud - SOV1 could be done on standard computing hardware we all use whereas the maths happening with SOV2 are being done using GPU-based processing in the cloud on much more powerful machines so that you don't have to sit there and wait for hours - just that should tell you something about the sophistication of V2 vs V1) SOV2 uses a more advanced modeling system with respect to the speaker being used in order to determine the shape/dimension of the speaker, how it is interacting with the room surroundings, and what affect that has on both the speakers low frequency output and it's time-of-flight (AKA group delay) for all frequencies. This is audible with most speakers (even passive) once a proper TuneDem has been completed, by just ensuring the proper speaker has been selected in Konfig, without applying SO. The profile(s) that Linn have for the speakers in their database specifically take into account where the center point of the midrange driver is on the loudspeaker, the cabinet dimensions, and the resonant frequency of the port/radiator system used (if any). So @akamatsu is correct about the fact that SOv2, is indeed based on the characteristics of the speaker being used and it's assumed/presumed response and interaction within the given environment.

- Linn are (or at least have been in the past) very adamant that NONE of the above is a "magic bullet" and that SOV2, just like V1, would only give proper results when the speakers are TuneDem'd properly into the room. The idea is, you need to get the speaker as free of the room influences as possible before you do anything further in software. Otherwise you're just chasing your tail, and likely making things sound worse than they should. It has been my experience that this is the "Achille's heel" for getting results with SO, and as I've mentioned elsewhere, I've not personally met very many folks who are competent with this process. Again, speaking from a NA/US perspective (I think things are a bit different in the UK/EU, etc.) there are plenty of audio "gurus" and speaker setup "masters" who would not have the first clue as to how to properly TuneDem a pair of speakers, let alone know what to do with something like SOv2. I know because many of them have flat out told me to my face that the speaker setup process that Linn uses is wrong, and is an incorrect way to go about tuning a speaker into a room. So my assumption is, whenever I read or hear something to the effect of "we tried it and the customer didn't like it" or "I like the sound with it off better than with it on", that the individuals involved in the setup don't really know what they're doing.
I think your last sentence is a little simplistic. For nearly all sysyems SO v1 at default calculations was not good.

Unfortunately some people stopped at that point and did not put more effort in or have erroneously decided that their one bad experience was definitive and they'll not accept that things have changed and may now be worth a re-visit.

Like the occasional Wam show visitor who will not go into a Linn room because they heard a Linn system 25 years ago and didn't like it.

They're potentially missing out.

 

akamatsu

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This is where as I recall (I haven't messed with Sov1 for years) my experience is much different, it may be the case in certain systems perhaps but that's not how I remember things.
You may be (most likely are) right. I was looking at ideal vs. practical and the modes didn't change. My mistake. I should know better than to rely on my memory. But I keep forgetting that. My apologies.

 
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Elad Repooc

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It all stands to reason as the formula for room modes is agnostic to listening position.
The listening position is required in order to ensure proper group delay for the drivers. A given speaker may excite a different room mode at a different position in the room depending on it's response characteristics. Which is why Tune Dem of the speakers and knowing where they are placed in relation to the listener is important. It is not just about correcting for the mode(s) the room supports and how the speaker works within that context, it is also about ensuring proper time-of-flight for the frequencies in relation to each other (harmonics). You can't really do this without having a primary listening position by which to determine when and at what frequency a given driver is going to fire, and how it's pressurization of the air volume is going to affect other frequencies as well. 

 
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Elad Repooc

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I think your last sentence is a little simplistic. For nearly all sysyems SO v1 at default calculations was not good.
No one bothered to read the manual and follow the instructions.

But I get it, it was very complicated in the beginning, and few people spent the time using it for the tool that it was. Anyway that doesn't matter anymore because SoV2 is beyond all of that anyway, as I've explained. It was the logical progression of the path they had started down, and it led them to something far better, which unfortunately is still largely being ignored.

I mean, at one point someone told me they had been told by Linn that only something like 25% of DS/DSM owners even bothered engaging SO, and that was after SOV2 came out. Seems like the only people who know anything about it are running around on this forum :)

 
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Craigas

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...at one point someone told me they had been told by Linn that only something like 25% of DS/DSM owners even bothered engaging SO, and that was after SOV2 came out. Seems like the only people who know anything about it are running around on this forum :)
So we are the experts, god help us and those who rely on us lol

 
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Pennypacker

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@akamatsu I’m not sure if SO corrects for time of flight, I think this is an Exakt-feature.

I want to add a couple of things to the discussion, these maybe some brain farts on my behalf though:

  • SO works only under 200Hz, my question is if this is “just” a limitation of the system or an deliberate limitation? IMHO by only tackling that frequency range the rest of the voicing of any speaker remains intact. 
  • Either way SO unmasks any “mistakes” made above 200Hz.
  • A lot of older discussion on the former Linn forum or other forums one can find online regarding choosing a certain speaker were/are about if this or that speaker could be handled in a room of such and such dimensions. Typical reactions are;  “speakers -X- bass is this or that” and gets dismissed on that manor. The other way around people may have been gravitated to bookshelfs for simulate reasoning. IMHO this should be a thing if the past with SO or other comparable solutions. Take my situation for instance, 10 years ago full range speakers would be a big no no given my room dimensions. 8x4 meters with my current behemoths (Keltiks) on the long wall firing down over the 4 meter length. If there is one speaker with a bad rap of to much bass and problematic to set up  it must be the Keltik, and yet here the are and everything sounds A-oké, made possible to a free software solution.
 
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Craigas

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Think that's why I like sticky threads, to accumulate a community agreed knowledge base.

 

akamatsu

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@akamatsu I’m not sure if SO corrects for time of flight, I think this is an Exakt-feature.
This is a common confusion on my part as well. You may be thinking of "phase alignment" which is done in Exakt and involves the different drivers within a speaker and the superior accuracy of digital crossovers. Something like that. I'm not sure to what degree "time of flight" involves individual drivers. I've always had the impression it just looked at the overall speaker location. If there is more to it than that, I'm simply unaware.

 
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Elad Repooc

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Per Linn's explanation of what is different about the new version of SO vs the older:



The spatial discretisation employed by this method of acoustic modelling allows the new version of Space Optimisation to correctly consider the effects of: non-rectangular rooms; the placement of features like doors and windows; and the location and rotation of your speakers. Furthermore, the time-domain formulation of this method of acoustic modelling means that the new version of Space Optimisation is now able to reduce both the energy and decay time of any artificial distortions caused by the interactions between your speakers and room, resulting in both a flat frequency response and a uniform decay time. Finally, the new version of Space Optimisation has been designed to give a better balance of low- and mid-frequency energy.


 


As far as I am aware the new version of SO compensates for group delay/time-of-flight on both Exakt and non-Exakt speakers, given the above explanation.


 


What Exakt does in addition to correcting time alignment (relative phase) is also correct for magnitude distortion, which you cannot with a non-Exakt speaker (since the differences in magnitude between drive units cannot be measured/fed back from a passive and/or analog system to the processor for correction). 


 


 

Elad Repooc

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Also on this note concerning group delay, it's interesting that in the past analog filters were considered "fast" if they didn't introduce more than 8ms of delay (relative to the rest of the drive units). Even the best analog filters introduce something like 4ms of delay. so if this can be properly corrected upstream for a passive system, it can obviously make things sound a lot more cohesive (which is what I find happens when passive speakers are selected in Konfig, after a Tune Dem to find the right spot in the room). 

 

Elad Repooc

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SO works only under 200Hz, my question is if this is “just” a limitation of the system or an deliberate limitation? IMHO by only tackling that frequency range the rest of the voicing of any speaker remains intact. 
I think given the above quote from Linn docs, that it's clear SO works above 200Hz (in terms of correcting for time-of-flight); what I think gets confused is that in terms of compensation (i.e. "EQ" - cutting the modes out) for the room itself, it only works on low frequencies. I was actually under the impression that SOv2 only really makes cuts in the low frequencies below 80Hz, can't quite remember where I saw/heard that but I believe it has changed a bit from version 1.

 

akamatsu

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I went into SOV1 and changed the speaker position around. I'm getting some confusing results. If I make reasonable changes that might represent real world adjustments, the frequency of the first, about three modes, doesn't change nor does the bandwidth. The gain does change.

If I make more extreme changes, such as having the speakers rather close to the front wall, an entire mode may drop off, and the second mode becomes the first mode. Also, there might be slight changes to the higher numbered modes, like 4 and 5. The changes are something like 77 Hz vs 75 Hz. These are just examples.

I'm not finding a reliable pattern in all this.

 

fredbatch

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Bit of a repeat of some of my previous posts, but here’s an summary/overview and explanation of SO, room modes, etc,  - certainly no claim to be definitive:

Room modal patterns of reinforcement and cancellation are created for all reflected soundwaves in an enclosed volume, across the entire frequency spectrum. It is akin to a unique fingerprint, peculiar to the precise geometry of the enclosed space. Modal frequencies transition in behaviour around the so-called Schroeder frequency, typically somewhere between 120 Hz and 200 Hz. Above the transition the behaviour of the modes is largely non-resonant, and their distribution is numerous and uniform. These modes do not generally adversely affect perceived sound quality. Conversely, below this transition region, the modes are less evenly spaced and readily discerned as resonant peaks and troughs. They are easily measured and heard. As an approximation they are often defined and calculated in terms of the order of reflections that can be defined in a cuboid space. The frequency position of the modes is an entirely dependent property of the geometry of the room and is unrelated to the speakers or speaker positions.

However, the excitation of this underlying pattern of LF modes will be perceived differently from different positions and every individual “point” in space will have its own unique perspective with regard to which modes are excited and to what degree. The listening position is one such “point”. The extent of the excitation of this underlying “modal pattern” is dependent on a) the position of the LF source (primarily the bass drivers) and b) the amount of LF energy available to energise the modes. The directivity pattern of the LF source – whether it be controlled cardioid, omnidirectional full sphere, half sphere, or whatever, will influence the results (cardioid response helps remove room effects).  Overall considerations are dependent not only on the position and output of the LF source, but also on the LF transmission/absorption properties of the structural boundaries of the enclosed space, which determines the amount of net LF energy available to rattle the cage.

 For lower frequencies, SO models this interactive behaviour and applies notch filters of suitable bandwidths and amplitudes to reduce the effect of constructive modal peaks (antinodes) below 80 Hz or so, as determined at the listening position. Destructive interference regions, as mentioned by others, cannot be addressed by applying this method in reverse. If more energy is pumped in to try and counteract a modal trough (node) it is simply cancelled by the same amount of energy reflecting back and nulling the input. It would be very wasteful of an amplifier’s power and provide no benefit to try and counteract it.

 SO2 uses a more advanced calculation method than SO1, encompassing a sophisticated boundary/mesh analysis technique rather than using standard equations for a regular rectangular cuboid, which just about every other calculation algorithm uses too. SO2 also applies some adjustment based on psychoacoustic preferences.

 Measurements and other DSP tools can be used to corroborate, validate and compare with SO. Lot’s of opinions and lot’s of choices.

 After the SO filters have been applied they can be tweaked. With SO1 this can be fairly gratuitous, enabling it to be used almost as a parametric equaliser if desired. I find the results of SO2 a marked improvement over SO1.  Either way, the clever bit has all been done. All we have to do is make a few measurements, fanny about and then debate the consequences.

 Using DSP to convert minimum phase response loudspeakers to linear phase, thereby preventing phase from varying with frequency, is a separate topic. Overall Group delay is part of this phenomenon due to a combination of mechanical and electrical factors, including driver voice coil inductive reactance, the displacement of driver center positions relative to each other and the listening position (Time of Flight considerations). Conventional passive crossovers also contribute significantly to phase anomalies. TOF corrections for “measured” loudspeakers appears to be done in SO2 and/or Exakt.  The latter adds further refinements to help accomplish linear phase and magnitude consistency.

 

akamatsu

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Apply SO, modes go away. Problem solved. I agree, and I have experienced this as I could move about the room and hear bass reinforced and attenuated at different positions. However, since I finally figured out how to do SO correctly, this isn't happening in my room anymore.
@sunbeamgls,

I had a listen last night. I put on some bassy music and moved about, first sitting back, then sitting forward. I didn't experience a real noticeable change in the bass. I then stood up and move to behind the sofa. Again, no real change. I finally walked around the room. Still no change, other than rather slight and not noticeable if I'm just listening to music.

Previously, I could go to the back of the room into the kitchen area and hear very noticeable bass reinforcement, not anymore.

 

akamatsu

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Yes, but if SO addressed a room mode NOT at the listening position, it will make the sound at the listening position sound "wrong".

If SO addressed a mode at the back of the room which was not present at the listening position, to make the response flat at the back of the room, it would create a dip in the frequency response at the listening position.

Take a look here: https://amcoustics.com/tools/amroc?l=500&w=600&h=250&r60=0.6

Click on some of the frequencies in the upper diagram and you get a map of where / how they affect different parts of the room.  Fixing a mode issue away from the listening position will create a problem in the FR at the listening position.
I don't know how I missed this yesterday. Having had a look, I'm sorry that I did miss it. Very interesting. It would be nice to see the formulas behind this, but I really don't want to delve that deeply. But I'm thinking that this is done with established "off the shelf" formulas and SOV1 would use the same. It's the information I was looking for.

I'll pay closer attention from now on. Thanks for posting this. What an awesome (educational in my case) tool. :)

 

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