SAM effects

[Jwg1749]

Cheers, guys! Some interesting thoughts there. 

Obviously bass response will depend on the woofer's excursion (among other things), so what SAM's doing is increasing bass response by extending woofer excursion by as much as is safe for any given speaker. So other things being equal, the most noticeable SAM improvement will come with relatively small long-throw woofers: step forward PHANTOM!

What you describe above is what I was getting at when I said SAM worked "predictively", i.e. based on the speaker modelling in the labs, SAM predicts the cone excursion. To me that's not what "in real time" means, but perhaps I'm just being a bit pedantic about the phrase "in real time".

I guess SAM is working predictively in real time?  Plus in my book, there is absolutely nothing wrong with being pedantic! 

Yes, "predictively in real time" satisfies my pedantry!

[thumb5]

The following was posted on the Linn Forums site by a Linn engineer, by way of an explanation as to how SAM works and contrasting it to the Linn Exakt system:


"The Devialet SAM system functions as a bass extension filter. They match a shelving filter that is equal and opposite to the natural roll-on of the speaker(*), effectively pushing the low frequency response of the speaker down in frequency. The shelving filter will produce an equal and opposite phase response to the natural roll-on of the speaker(*) thereby linearising the low frequency phase response (to some degree).


(*) based on measurement of a single loudspeaker, so not truly accurate when you consider production variance.

At very low playback levels this extension can be pushed to (conceivably) quite low frequencies without end stopping the drive unit. However, as playback level is increased, the influence of the shelving filter applied by Devialet is reduced giving progressively less bass extension as the volume is increased. To claim that the low frequency of the Ninka is extended to 15 Hz is therefore rather disingenuous.
..."

Guillaume

That's very interesting.  It makes it sound as if SAM is going to compress dynamic range in the bass region, which surely can't be right, can it?  If it works like that, is the extent of the SAM effect actually controlled by the volume setting (static) or the average "loudness" of the signal (dynamic)?

[Confused]

In the spirit of keeping things on topic but also continuing interesting discussions,  very interesting proposal has emerged in another thread, let's call it the 'Gui test'.

As follows:

To experience for yourself what I'm hearing listen to a recording with no bass but high frequencies (single instrument, woman's voice) and many of room information (best is live recordings). Listen - switch off SAM on RC - listen again. Then you know what SAM also does to your music.

To me this looks like a fun thing to try, and it might indeed prove very informative.  I plan to give this a go over the weekend.

[GuillaumeB]

In the spirit of keeping things on topic but also continuing interesting discussions,  very interesting proposal has emerged in another thread, let's call it the 'Gui test'.

As follows:

To experience for yourself what I'm hearing listen to a recording with no bass but high frequencies (single instrument, woman's voice) and many of room information (best is live recordings). Listen - switch off SAM on RC - listen again. Then you know what SAM also does to your music.

To me this looks like a fun thing to try, and it might indeed prove very informative.  I plan to give this a go over the weekend.

Cheers Confused! Yes I think this will be very interesting.

Guillaume

[Confused]

OK - I have just been trying the 'Gui' test. (Per #53 above)

Very interesting!  I used the Devialet remote pseudo blind test, that is you repeatedly press the SAM on / off button to the point that you do not know if it is on or off, sat in the listening position I cannot see the display on the Devialet.  I did manage to find a number of recordings with more or less zero bass as suggested, all 24 bit and decent recordings.  Toggling SAM on and off I, I could tell a difference between each one.  In terms of details, I could notice a very slight improvement / reduction in the fine details.  The first couple of time I checked, the slightly better details were obtained with SAM off.  I was able to repeat this a number of times, there was one occasion where I preferred the SAM on version, but other than that, each time SAM off prevailed.  I recall YabaVR (Gui) posting that SAM 'looses all the fine details'.  I would not put it as starkly as this, for me it was a very small reduction in fine details, very small but clearly discernible.  As for soundstage, this was a bit hit and miss for me, so I reckon this aspect may be more system / listener specific.  Sometime I preferred the soundstage with SAM on, but I think a fairly consistent result was a narrowing of the soundstage, which in same cases I think I may have preferred as it came across as a more accurate sound stage, possible because it was actually less accurate!  So yes, definitely a ***** (replace ***** with insignificant, small, major / unacceptable, depending on your perspective) loss of details. I think the sound stage effect could be system dependant, but in my case it was a narrower sound stage that perhaps seamed more precise and more detached from the speakers, which could mean more mono!

Well done to Gui for spotting this and posting such a clear method of trying it for yourself.

Being slightly less serious (although there may be a serious point lurking here), I can now propose the Confused SAM test.  This is for the very brave only.  Play the first 30 seconds of Dizzee Rascal's 'Dirtee Disco' on a reasonable volume. Please note that it is neither safe nor sensible to play more than 30 seconds of this track.  I suspect that Confused SAM test may also be very system dependant.

[thumb5]

Given the health warning, I wonder what are the possible outcomes of the Confused SAM test? Or is that self-explanatory on carrying it out...

[Confused]

Given the health warning, I wonder what are the possible outcomes of the Confused SAM test?  Or is that self-explanatory on carrying it out...

Nothing serious, it's just the rest of the song will send you quite mad.

[4tLotM]

When i use sam in 100% the temperature of the Analog Amp of my 250 pro goes up to 65 degrees. The volume was -25. When i turn sam off it's about 45 degrees. It's that a normal thing?

[Antoine]

If the exact temperature increase is normal or not depends on whether you provide sufficient ventilation (65 degrees is quite high) but that the temperatures increase with higher SAM usage is to be expected.

The SAM percentage controls the amount of bass extension and the amp has to provide much more power for that extra extension.

I would think though that your D amp would rise about as much in temperature as it provides most of the current.

[4tLotM]

If the exact temperature increase is normal or not depends on whether you provide sufficient ventilation (65 degrees is quite high) but that the temperatures increase with higher SAM usage is to be expected.

The SAM percentage controls the amount of bass extension and the amp has to provide much more power for that extra extension.

I would think though that your D amp would rise about as much in temperature as it provides most of the current.

My actual temps. at -25 db. I didn't thaught that the A-Amp makes the work.