To SAM or not to SAM and DRC

[Soniclife]

The most difficult thing in this test is the transparency of your system chain...I know, I know, everybody in this forum would claim his system for being very transparent   .
But may be there is a here and then of someones system resolution being a little bit better than the average   ...you know what I mean   .
For those having a 'highly' transparent system the effect the test discovers will be of a large amount, I promise. Saying that we did this test with 'highly' tuned rooms and systems here.

"I've made up my mind, don't confuse me with the facts."

There is no point proposing a subjective test if your going to reject the samples that don't agree with your theory.

There are so many reasons for why different people and systems could produce very different results here.  Of the top of my head hear are a few.

1) The different transform functions of the different SAM profiles may act, or not on the relevant frequencies.
2) In general the smaller the speaker the larger the group delay that would need fixing, so it might be critical to have SAM on for small speakers, but off for large speakers.  Same goes for the response equalisation.
3) 2 way vs 3 way, depending on the crossover frequency some SAM profiles might need to, but won't from my understanding of how the measurements are done, take account of the output from the midrange unit if shallow slopes are used in the crossover.
4) Doppler effect of moving small drive units a large amount more than originally designed might impact midrange performance.
5) How SAM'able a speaker is.  I've been curious why some speakers cannot be SAM'ed, but other similar designs can, e.g. Fact 8 (can) vs Fact 12 (cannot, they have tried and failed more than once apparently), makes me wonder if there is a sliding scale of how well SAM works, with some just qualifying and others ideal.
6) Multiple bass units vs one, I'm  guessing multiples are harder to correct than single ones, they must be harder to measure.

I expect anyone who has studied sound, or loudspeaker design will have many more, and this is before we get to such standard hifi reasons as peoples rooms, the recordings used and personal preference.  I'm amazed it works at all.

[ogs]

Hi gui
there are weaknesses in your reasoning here; you assume that the loudspeakers in use are transparent and 'correct' sounding. Very few speakers have linear phase response. Example: the Kef LS50 has the tweeter inverted, many (most?) Wilson models invert the midrange driver, many High End speakers do not even try to have a decent time response. If a dome tweeter is mounted on the same baffle as the bass/mid, the treble arrives too early. You'll have to account for this when you develop your theory. Your ML speakers is very good in this respect, I am sure.
You may be correct when you say that digital room correction reduces information density, but this is not my experience. I use Audiolense with long filters (132K) and can not say I miss something. If I use short filters (8K, 16K) I can hear the 'coarseness', but not with the long ones. Your test with SAM on/off and a female voice is interesting. I will try this as soon as I get my amp back from upgrade. Your binding post mod will be hard for me to resist, however! And what about this 'secret mod' you have mentioned?

No, you got me wrong. I know loudspeakers are not correct sounding when it comes to phases. And the ML are by far no reference for me.

But why does it matter anyway. For me this is a good distinction for good and bad loudspeakers. The one which is more neutral on the phase is mostly the better sounding for me.
The music signal is not meant to compensate on this. It's a 3D-Matrix. You can not cut in and take one 'thing' (freq/vol) out of it. If you do you cut this 'freq/vol thing' out of every (sound) object in the 3D-Matrix. You can only do harm to the signal when you try to solve problems here though their cause is further down the system chain.

It might not be easy to imagine what I mean about this 3D-Matrix (freq/vol/phase) of the music signal. 'freq/vol/phase' of a sound in a room is unique at every point inside this room and these points are dependent on each other. Think of reconstructing a single moment with all sounds in this room. The values of 'freq/vol/phase' have to be variable to describe every point in the room. You can not use a set value for a unique freq to be assigned to every point of its occurrence because this unique freq might belong to a saxophone AND also to a voice AND a guitar AND...it has to be different in 'vol/phase' at every of this points.
Man, it's hard to get it down to words  
Think of it again and it might do a 'klick' in your head    .

I think I know what you mean. I'll test as soon as my amp is back from Paris. Like Hifi_swlon I have compromises in speaker placement and depend on RC.

[Soniclife]

SAM does very little here. Yes it makes the facts go deeper, but i always feel it comes with a narrowing of soundstage, and in my average shared use lounge this extra bass doesn't really sound right anyway. I also sense a slight 'softening' of the sound with SAM.

FWIW, and in your case this really isn't worth anything, when I had Fact 8s on home dem one of the things I struggled with is that there was no way I would want them without SAM, and I wasn't sure about buying a speaker that only worked with SAM, but with SAM I was very close to wanting them.  SAM added deep extension, really filling in the bottom end, and that brought a much larger acoustic with it, but it didn't do anything for the higher up edginess I ultimately decided I didn't like. Rooms are a pain, if only I liked headphones.

[yabaVR]

The most difficult thing in this test is the transparency of your system chain...I know, I know, everybody in this forum would claim his system for being very transparent   .
But may be there is a here and then of someones system resolution being a little bit better than the average   ...you know what I mean   .
For those having a 'highly' transparent system the effect the test discovers will be of a large amount, I promise. Saying that we did this test with 'highly' tuned rooms and systems here.

"I've made up my mind, don't confuse me with the facts."

There is no point proposing a subjective test if your going to reject the samples that don't agree with your theory.

My comment wasn't meant to offend and I'm not rejecting any samples but wanted to give an explanation for those not hearing large differences or no differences at all, hence the smilies   .
For the rest of your post you're absolutely right. One can not estimate on all influences that belong to the sensed effects.


gui

[baconbrain]

I had also propagated the merits of SAM after purchasing my 250. To me, it just sounded better.

After investing in additional DRC equipment and listening to the significant change in results, I also began to question the value of SAM again. If SAM is truely doing everything that it is marketed to do, why the significant difference in SQ after additional DRC?

For me, it ultimately links back to the acoustics of the listening room. I am quite sure that the room Devialet used when setting up SAM for my speakers was no where close to my living room ...

[yabaVR]

...
An other consideration is that a phase shift is a phase shift and an attenuation is an attenuation and it does not matter if it is done in the digital, the analog or the acoustic domain. Similarly, if I can insert somewhere in the chain the exact inverse function the end result will be much more accurate, and it does not matter in which domain the correction is done. 
It happens that digital signal processing is the most cost effective way to achieve it. So yes the digital chain is no longer bit perfect but the overall chain becomes much closer to the identity function. 
...

Jean-Marie

Good point Jean-Marie and somehow it made 'klick' in my head this morning. I may got it wrong inasmuch as looking ONLY on single sound objects.
Thinking more over it you are right that a phase shift is a phase shift for ALL sound objects in the end.

But there is this last point standing. That's the SAM test from above. The difference/effect in SAM On/Off can clearly be recognized. There has to be a conclusion to this effect for me.

If I think of SAM doing it right in theory but to accomplish its task it has to use digital filters.
SAM compensates for phase and volume flaws of the speakers BUT has to use filters that itself have phase shifts involved on the freq they are used on (6dB/90°, 12dB/180°, 18dB/270°, 24dB/0°).
Even 24dB (no phase shift?) needs processing time, so there is a time dependency here? As I'm no engineer on this task now it would be nice to have Devialet engineer on hand and have some enlightment. It's all patented anyway. He could make detailed comments. Ok, dream on...

But may this be the point?
SAM compensates for the big flaws of a speaker but can not prevent smaller flaws (phase shifts) to appear in the music signal hence its function parameters?

gui

[yabaVR]

I had also propagated the merits of SAM after purchasing my 250. To me, it just sounded better.

After investing in additional DRC equipment and listening to the significant change in results, I also began to question the value of SAM again. If SAM is truely doing everything that it is marketed to do, why the significant difference in SQ after additional DRC?

For me, it ultimately links back to the acoustics of the listening room. I am quite sure that the room Devialet used when setting up SAM for my speakers was no where close to my living room ...

I don't have the link on hand but Devialet showed in a vid how they meassure a speaker with SAM. The mic is very close to the speaker and it only meassures the direct sound coming from the speaker. Reflections of the room won't get meassured as they say.

Conclusion for me is that SAM does only compensate for the speaker parameters not the room parameters. That's why you achieve further improvements with DRC.

gui

[Hifi_swlon]

I didn't think they measured with a mic at all? I thought it was impedance etc and driver excursions measured by laser?

They also measure a single speaker driver per model, and rely on all speakers ever made performing 100% identically. How realistic that is I'm not sure. For those who place a lot of weight on speaker cables, jumpers and connectors making significant differences, I'm not sure how these things are taken into account either.

[yabaVR]

I didn't think they measured with a mic at all? I thought it was impedance etc and driver excursions measured by laser?

They also measure a single speaker driver per model, rely on all speakers ever made performing 100% identically. How realistic that is I'm not sure.  For those who place a lot of weight on speaker cables, jumpers and connectors making significant differences, I'm not sure how these things are taken into account either.

Yeah, sorry...you're absolutely right. No mic was involved in SAM meassurement.

gui

[Hifi_swlon]

I didn't think they measured with a mic at all? I thought it was impedance etc and driver excursions measured by laser?

They also measure a single speaker driver per model, rely on all speakers ever made performing 100% identically. How realistic that is I'm not sure.  For those who place a lot of weight on speaker cables, jumpers and connectors making significant differences, I'm not sure how these things are taken into account either.

Yeah, sorry...you're absolutely right. No mic was involved in SAM meassurement.

gui

No apology needed! But definitely none of the room creeping into measurements (for whoever was worried about that), well, unless the whole room was vibrating, or containing an as yet undiscovered black hole perhaps.