22-Dec-2023, 21:59
@daniel.avasilichioaei
Your post is the first time I've heard mention of SAM introducing a progressive reduction of frequencies below 30 Hz. I haven't conducted any testing of my own but I don't think that can be quite accurate.
I have no doubt that SAM does roll off at the lower end of its range for a given speaker in order to protect the speaker driver but if one looks at Devialet's quoted claims for the bass extension SAM can deliver for different speakers one finds that for many "small" speakers it does not extend bass to 30 Hz while for many "larger" speakers the response is extended to below 20 Hz. Looking at the claims for a variety of speakers some years ago I came to the conclusion that it extended bass response by something between half an octave and an octave and that the amount of extension claimed increased as the speaker manufacturer's claimed bass response got lower. That's kind of in line with a comment I remember reading in Floyd Toole's book "Sound Reproduction" which said something like phase correction in the bass resulted in an extension of around half an octave.
Speakers roll off naturally in the bass and SAM can't avoid that, in fact trying to extend the bass response of every speaker to, say, 20 Hz would result in damage to a lot of woofers. There's a limit to how far you can push a driver without causing damage and some speaker drivers are more "robust" than others.
So I think that you're right is stating that SAM progressively reduces frequencies at the low end but I think that reduction actually occurs at the low end of the profile for each speaker rather than from a set frequency such as 30 Hz given that Devialet's claims for the extension provided for some "smaller" speakers does not extend as low as 30 Hz and logic suggests that SAM has to be rolling off its action progressively at the low end of it's claimed extension capability for those speakers.
I would love a fuller explanation from Devialet about just what SAM is doing. I suspect at 0% it is simply correcting phase with a "roll off" of that correction at the upper end of its range so that there's a smooth transition back to the woofer's natural behaviour and a "roll off" at the lower end also in order to deliver a natural roll off at the bottom end. I would love to know what's going on in between as one increases the SAM setting. Is the change between 0% and 100% achieved with simply a graduated increase in the amount of phase correction applied, is the phase correction profile fully implemented at 0% with an increasing amount of bass boost applied as you increase the setting, do they use a combination of those 2 strategies, or is there some other "secret sauce" involved in what SAM does?
I hadn't thought of the possibility that SAM responds differently with pure sine waves than it does with music but having read your comment I do think that is plausible but I think that Devialet is probably being honest when they told you that this was because SAM was designed for music rather than for pure sine waves though I suspect that it also is a factor in how the driver protection function is implemented.
I've used SAM with 2 different speakers since getting my Devialet, originally with Dynaudio Contour 1.3 SEs and then with my current Focal Sopra 2s. I ended up settling on a setting of around 50% with the Contours but I've ended up running SAM at 0% with the Sopra 2s. Dynaudio claims bass extension to 35 Hz for the Contours and Focal claim extension to 33 Hz for the Sopra 2s, a relatively small difference in extension but my experience is that increasing the SAM setting above 0% delivers very different results in my room with those 2 speakers and I put that down to differences in speaker placement plus the fact that the woofers of the Sopra 2s, a floor stander, are much closer to the floor than the woofers of the stand mounted Contours which means they load the room differently to the Contours and get more room reinforcement. I think SAM is beneficial but I also think that there can be a lot of difference in the SAM profiles for different speakers, thaty different speakers can load the room at bass frequencies in very different ways, and that speaker placement also has a significant effect on bass response in the room. Taken together, those factors mean that one needs to spend a fair amount of time playing with speaker placement and the SAM setting if one is to get the best out of SAM because whatever SAM is doing, it is operating in a frequency range where the room is also a big player in the bass response we hear and interactions between what SAM is doing and what the room is doing are probably a factor in any situation where someone is reporting problems with SAM. Those interactions are also probably a major factor in why different people report using very different SAM settings with the same speakers much less with different speakers. They're probably also the reason why Devialet use a laser device to measure the woofer's response when creating profiles rather than microphone measurements because the physical behaviour of the woofer, which is what the laser device is measuring, is probably going to be far more consistent from room to room than microphone measurements will be.
Your post is the first time I've heard mention of SAM introducing a progressive reduction of frequencies below 30 Hz. I haven't conducted any testing of my own but I don't think that can be quite accurate.
I have no doubt that SAM does roll off at the lower end of its range for a given speaker in order to protect the speaker driver but if one looks at Devialet's quoted claims for the bass extension SAM can deliver for different speakers one finds that for many "small" speakers it does not extend bass to 30 Hz while for many "larger" speakers the response is extended to below 20 Hz. Looking at the claims for a variety of speakers some years ago I came to the conclusion that it extended bass response by something between half an octave and an octave and that the amount of extension claimed increased as the speaker manufacturer's claimed bass response got lower. That's kind of in line with a comment I remember reading in Floyd Toole's book "Sound Reproduction" which said something like phase correction in the bass resulted in an extension of around half an octave.
Speakers roll off naturally in the bass and SAM can't avoid that, in fact trying to extend the bass response of every speaker to, say, 20 Hz would result in damage to a lot of woofers. There's a limit to how far you can push a driver without causing damage and some speaker drivers are more "robust" than others.
So I think that you're right is stating that SAM progressively reduces frequencies at the low end but I think that reduction actually occurs at the low end of the profile for each speaker rather than from a set frequency such as 30 Hz given that Devialet's claims for the extension provided for some "smaller" speakers does not extend as low as 30 Hz and logic suggests that SAM has to be rolling off its action progressively at the low end of it's claimed extension capability for those speakers.
I would love a fuller explanation from Devialet about just what SAM is doing. I suspect at 0% it is simply correcting phase with a "roll off" of that correction at the upper end of its range so that there's a smooth transition back to the woofer's natural behaviour and a "roll off" at the lower end also in order to deliver a natural roll off at the bottom end. I would love to know what's going on in between as one increases the SAM setting. Is the change between 0% and 100% achieved with simply a graduated increase in the amount of phase correction applied, is the phase correction profile fully implemented at 0% with an increasing amount of bass boost applied as you increase the setting, do they use a combination of those 2 strategies, or is there some other "secret sauce" involved in what SAM does?
I hadn't thought of the possibility that SAM responds differently with pure sine waves than it does with music but having read your comment I do think that is plausible but I think that Devialet is probably being honest when they told you that this was because SAM was designed for music rather than for pure sine waves though I suspect that it also is a factor in how the driver protection function is implemented.
I've used SAM with 2 different speakers since getting my Devialet, originally with Dynaudio Contour 1.3 SEs and then with my current Focal Sopra 2s. I ended up settling on a setting of around 50% with the Contours but I've ended up running SAM at 0% with the Sopra 2s. Dynaudio claims bass extension to 35 Hz for the Contours and Focal claim extension to 33 Hz for the Sopra 2s, a relatively small difference in extension but my experience is that increasing the SAM setting above 0% delivers very different results in my room with those 2 speakers and I put that down to differences in speaker placement plus the fact that the woofers of the Sopra 2s, a floor stander, are much closer to the floor than the woofers of the stand mounted Contours which means they load the room differently to the Contours and get more room reinforcement. I think SAM is beneficial but I also think that there can be a lot of difference in the SAM profiles for different speakers, thaty different speakers can load the room at bass frequencies in very different ways, and that speaker placement also has a significant effect on bass response in the room. Taken together, those factors mean that one needs to spend a fair amount of time playing with speaker placement and the SAM setting if one is to get the best out of SAM because whatever SAM is doing, it is operating in a frequency range where the room is also a big player in the bass response we hear and interactions between what SAM is doing and what the room is doing are probably a factor in any situation where someone is reporting problems with SAM. Those interactions are also probably a major factor in why different people report using very different SAM settings with the same speakers much less with different speakers. They're probably also the reason why Devialet use a laser device to measure the woofer's response when creating profiles rather than microphone measurements because the physical behaviour of the woofer, which is what the laser device is measuring, is probably going to be far more consistent from room to room than microphone measurements will be.
Roon Nucleus+, Devilalet Expert 140 Pro CI, Focal Sopra 2, PS Audio P12, Keces P8 LPS, Uptone Audio EtherREGEN with optical fibre link to my router, Shunyata Alpha NR and Sigma NR power cables, Shunyata Sigma ethernet cables, Shunyata Alpha V2 speaker cables, Grand Prix Audio Monaco rack, RealTRAPS acoustic treatment.
Brisbane, Qld, Australia
