21-Dec-2023, 21:48
I'm not certain that the problem is a SAM problem and, re-reading the earlier posts in this thread including mine, I'm wondering whether it is actually a room problem or a problem related to the interaction of SAM and the room.
Let's look at the issue:
- it's a bass frequency problem;
- SAM affects bass frequencies below 150 Hz;
- rooms produce bass frequency response issues due to the effect of modal frequencies.
SAM does 3 things. First, at a setting of 0% it corrects the speaker's phase response at frequencies below 150 Hz and that will produce stronger bass at some frequencies. Second, it allows you to extend the speaker's bass response by raising the SAM setting above 0% and doing that will progressively boost low bass response. Third, it has a protection feature "built in" which cuts the boost if you raise the volume to high levels in order to protect the woofers.
What do room modes do to bass frequencies? Depending on your location in the room (where you put your listening chair), the level of bass frequencies related to the room dimensions will be boosted or reduced to some degree.
Let's say your problem occurs at x Hx. SAM may be correcting the phase of that frequency to a degree that it makes that frequency louder at the listening position and you may be increasing the boost at that frequency by using a SAM setting higher than 0%. How do you work out whether SAM is contributing to the problem? Turn SAM off. If the problem is less noticeable then SAM is contributing to the problem.
How do we work out whether the room's modal frequencies are a factor? Move backwards and forwards from the listening position along a line equidistant from the 2 speakers. Is the problem better or worse in some locations than it is at the listening position (ear height can make a difference so try to keep your ears at the same height as they are at the listening position). If the problem reduces or disappears at a location which is different to your listening position then the room is having an effect.
What to do?
If it's only a SAM problem then turn the SAM setting down or turn SAM off. If it's only a room problem then either move the listening position to a location where the problem is minimised while still keeping a sound balance you like and/or move the speakers a little closer or further away from the wall behind them. If both SAM and the room are contributing, then try a combination of those suggestions.
If the subsonic filter is helping then that suggests that the problem is occurring at a frequency below 20 Hz because subsonic filters apply a steep roll off below 20 Hz. If you need to run additional highness filters in order to prevent it then that suggests the problem is above 20 Hz. You didn't say what the highness filter frequencies were but if they're above 20 Hz then the problem is above 20 Hz and you probably don't need to engage the amp's subsonic filter because the highness filter should be sufficient.
If the problem frequency is above 20 Hz then there is another possible cause which is speaker related. If the speaker is ported then what you may be hearing is a "chuffing" sound as air is expelled from the speaker's port at or around the frequency the port is tuned to. If that's the case then you could try sealing the speaker ports if the speaker comes with foam plugs designed for that purpose and see if that solves the problem. You'll probably want to adjust your SAM setting if that suggestion works.
Regardless of whether you can avoid the problem by using the amp's subsonic filter or a high pass filter on your computer, I would try to avoid using that solution because filters are going to affect all frequencies below the set frequency and that means they're going to affect other bass frequencies which aren't causing the problem so I'd first try to solve the problem without using a high pass filter of any kind.
I hope there's something in the above suggestions which helps.
Let's look at the issue:
- it's a bass frequency problem;
- SAM affects bass frequencies below 150 Hz;
- rooms produce bass frequency response issues due to the effect of modal frequencies.
SAM does 3 things. First, at a setting of 0% it corrects the speaker's phase response at frequencies below 150 Hz and that will produce stronger bass at some frequencies. Second, it allows you to extend the speaker's bass response by raising the SAM setting above 0% and doing that will progressively boost low bass response. Third, it has a protection feature "built in" which cuts the boost if you raise the volume to high levels in order to protect the woofers.
What do room modes do to bass frequencies? Depending on your location in the room (where you put your listening chair), the level of bass frequencies related to the room dimensions will be boosted or reduced to some degree.
Let's say your problem occurs at x Hx. SAM may be correcting the phase of that frequency to a degree that it makes that frequency louder at the listening position and you may be increasing the boost at that frequency by using a SAM setting higher than 0%. How do you work out whether SAM is contributing to the problem? Turn SAM off. If the problem is less noticeable then SAM is contributing to the problem.
How do we work out whether the room's modal frequencies are a factor? Move backwards and forwards from the listening position along a line equidistant from the 2 speakers. Is the problem better or worse in some locations than it is at the listening position (ear height can make a difference so try to keep your ears at the same height as they are at the listening position). If the problem reduces or disappears at a location which is different to your listening position then the room is having an effect.
What to do?
If it's only a SAM problem then turn the SAM setting down or turn SAM off. If it's only a room problem then either move the listening position to a location where the problem is minimised while still keeping a sound balance you like and/or move the speakers a little closer or further away from the wall behind them. If both SAM and the room are contributing, then try a combination of those suggestions.
If the subsonic filter is helping then that suggests that the problem is occurring at a frequency below 20 Hz because subsonic filters apply a steep roll off below 20 Hz. If you need to run additional highness filters in order to prevent it then that suggests the problem is above 20 Hz. You didn't say what the highness filter frequencies were but if they're above 20 Hz then the problem is above 20 Hz and you probably don't need to engage the amp's subsonic filter because the highness filter should be sufficient.
If the problem frequency is above 20 Hz then there is another possible cause which is speaker related. If the speaker is ported then what you may be hearing is a "chuffing" sound as air is expelled from the speaker's port at or around the frequency the port is tuned to. If that's the case then you could try sealing the speaker ports if the speaker comes with foam plugs designed for that purpose and see if that solves the problem. You'll probably want to adjust your SAM setting if that suggestion works.
Regardless of whether you can avoid the problem by using the amp's subsonic filter or a high pass filter on your computer, I would try to avoid using that solution because filters are going to affect all frequencies below the set frequency and that means they're going to affect other bass frequencies which aren't causing the problem so I'd first try to solve the problem without using a high pass filter of any kind.
I hope there's something in the above suggestions which helps.
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
