To SAM or not to SAM and DRC

[baconbrain]

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.  

I was worried about the room. Sounds like I need to do some more homework.

[Confused]

Here are some nice videos to watch:

https://www.youtube.com/watch?v=AcLYb4sBhwQ

https://www.youtube.com/watch?v=DWFDPCKS3XM

Anyway, stop overthinking this the lot of you! Go and try the 'gui' test instead and see what you hear.

[Jean-Marie]

...
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

I was only trying to answer to the part whether bit perfect is important or not.

This being said, I don't know enough details about how Devialet is doing its SAM processing to comment on whether or not they are introducing extra phase changes beyond the compensation it intends to do or not.

An other interesting point is not not every phase shift is audible. I find it fascinating that one cannot distinguish by ear whether the bow of a violin is being pushed or pulled, but if you look at the spectrum, the harmonics are seriously phase shifted between the two.

One thing that would be interesting would be to do the test with the SAM percentage to zero, which if I have understood correctly would turn down the bass extension aspect and only leave the phase correction of the phase.

Jean-Marie

[yabaVR]

An other interesting point is not not every phase shift is audible. I find it fascinating that one cannot distinguish by ear whether the bow of a violin is being pushed or pulled, but if you look at the spectrum, the harmonics are seriously phase shifted between the two.

One thing that would be interesting would be to do the test with the SAM percentage to zero, which if I have understood correctly would turn down the bass extension aspect and only leave the phase correction of the phase.

Jean-Marie

Very interesting. I didn't knew that there is a phase shift in push/pull a bow on a violin. So the sound on one tone could go on for ever if there was a perfect musician playing one tone on a violin in perfection with zero pause between push/pull and you won't recognize a difference? Would be interesting to audition even if not perfect. I like those trials. Keeps my brain trained to be attentive.

We did the test also with SAM@0%. The result was the same. Loosing (all  ) micro details around the instruments/singer connecting them to the recording room as micro reverberation details.

gui

[Jean-Marie]

An other interesting point is not not every phase shift is audible. I find it fascinating that one cannot distinguish by ear whether the bow of a violin is being pushed or pulled, but if you look at the spectrum, the harmonics are seriously phase shifted between the two.

One thing that would be interesting would be to do the test with the SAM percentage to zero, which if I have understood correctly would turn down the bass extension aspect and only leave the phase correction of the phase.

Jean-Marie

Very interesting. I didn't knew that there is a phase shift in push/pull a bow on a violin. So the sound on one tone could go on for ever if there was a perfect musician playing one tone on a violin in perfection with zero pause between push/pull and you won't recognize a difference? Would be interesting to audition even if not perfect. I like those trials. Keeps my brain trained to be attentive.

We did the test also with SAM@0%. The result was the same. Loosing (all  ) micro details around the instruments/singer connecting them to the recording room as micro reverberation details.

gui

So in theory that should put out of the equation the possible effect and phase shift of the bass extension.

Only remained the processing done for correcting the phase of the speaker.

I was reading the theory being the Manger transducer and it is quite different from traditional speakers, especially in the phase sector.... 

I'm reaching here my threshold of incompetency and will not be able to go deeper.

Jean-Marie

[4tLotM]

I tried a lot of music with or without sam and for 70 percent i decided for sam off. I heard over 100 songs in different genres and made a list and deciced for the better SQ.
But i had one big problem: the temperature. So i made another test: I stopped the music, turned off the 250 pro and wait one hour.
I started the 250 without playing music. Sam on, Dpm off, Vol. 0 db. I turned to the Temperature list. I was shocked. In only 2 minutes the temp of the a-amp climbs from 29 to 75 degrees, without any input. D-amp and supply stays about 38 degrees (With dpm on and sam off the a-amp climbs to 43 degrees). I think my upgraded 250 pro has a real problem. Or has any other user a similar observation?

[Jean-Marie]

I tried a lot of music with or without sam and for 70 percent i decided for sam off. I heard over 100 songs in different genres and made a list and deciced for the better SQ.
But i had one big problem: the temperature. So i made another test: I stopped the music, turned off the 250 pro and wait one hour.
I started the 250 without playing music. Sam on, Dpm off, Vol. 0 db. I turned to the Temperature list. I was shocked. In only 2 minutes the temp of the a-amp climbs from 29 to 75 degrees, without any input. D-amp and supply stays about 38 degrees (With dpm on and sam off the a-amp climbs to 43 degrees). I think my upgraded 250 pro has a real problem. Or has any other user a similar observation?

I'm sorry to say this, but yes this looks very suspicious to me. Especially the test you did with no input. The class A shall reply be barely working and therefore there is no good reason for it to get that hot. 

My recommendation would really be to contact Devialet 's support and ask for their opinion. 

Jean-Marie

[Antoine]

@4tLotM, since you did the exact same thing here: http://devialetchat.com/showthread.php?t...6#pid53166 please read this: http://www.urbandictionary.com/define.ph...0Hijacking

[4tLotM]

@4tLotM, since you did the exact same thing here: http://devialetchat.com/showthread.php?t...6#pid53166 please read this: http://www.urbandictionary.com/define.ph...0Hijacking

No, first i thought it depends on the musical input. Now i tried it without any input.

[baconbrain]

I don't think that bit perfect is what really matters. The ideal would be a system that reproduces at the listening location as the output of the speakers the exact sound Field that the microphone was attempting to capture. 

Back to topic ....

+1 Jean Marie. After chewing on it awhile, I believe your conclusion is the one which really makes the most sense.

The listening postion has to be the reference point, and since that varies for each of us (for better or for worse), it would seem logical that the individual listening position would explain why some hear more benefits with SAM and others less.