Low Volume Listening?

[awkaplan]

 …Also partly wonder if a larger speaker may be less likely to disturb upper and lower neighbors at lower volumes.

Speaker size is irrelevant. The thing which causes disturbance is volume, the sound pressure level that you listen at and not the numerical value shown on the volume display of an amp.

When sound travels a greater distance, the sound pressure level reduces because it's spread over a larger area. When sound travels through something like a wall or floor or ceiling,  the energy in the sound is reduced because it takes energy to pass through a physical medium so the sound pressure level of the sound emerging on the other side is lower. Both sorts of loss occur as sound moves from your room to the neighbour's apartment and the loss is greater at  high frequencies than at low frequencies,

t's possible to calculate the amount the sound pressure level is going to drop between the level it is at your listening position and the neighbour's apartment in dB which is a measure of sound pressure level. Let's call the amount of loss x dB, noting that the value of x going to be different at different frequencies. If the level at your listening position is 80 dB at a given frequency, it will be 80-x dB in your neighbour's apartment. If the level is 100 dB in your room the level is going to be 11 - x dB in your neighbour's room. The loss in getting from your room to the neighbour's room is basically a constant that doesn't depend on your actual listening level.

Say you have 2 speakers, a small 2 way and a larger 3 or 4 way speaker. Either speaker can deliver the same levels in your room. It doesn't matter which speaker you use, if the level in your room at a given frequency is 80 dB then the level in the neighbour's room is going to be 80-x dB and if the level in your room is 100 dB the level will be 100-x db in the neighbour's room. The size of the speaker isn't going to affect that at all.

What will make a difference is the amount of bass extension the speaker has. Bass frequencies hold up more over distance and in getting through walls/floors/ceilings so the value of the loss involved, the value of x, reduces as frequency drops. The lower the extension of the speaker, the deeper the bass it can produce, the higher the level in your room at that frequency is going to be for the same volume setting on your amp. Let's say you have a level of 80 dB in your room at a 1000 Hz. If you have a speaker that's 6 dB down at 40 Hz in your room then the level at 40 Hz in your room is going to be 74 dB and the level in your neighbour's room is going to be 74 - x dB. If you have a speaker with more extension things change. Let's say that added extension means it's response in your room is flat to 40 Hz. That means the level in your room is going to be 80 dB at 40 Hz when it's 80 dB at 1000 Hz and the level at 40 Hz in your neighbour's room is going to be 80 - x dB. That means the level in your neighbour's room at 40 Hz is going to be 6 dB higher if you play a speaker that's flat to 40 Hz at a level than it will be with the other speaker if the level you listen to both at is the same at 1000 Hz. An increase of somewhere between 6 and 10 dB is regarded as being around twice as loud to our ears at 1000 hz and a bit less than twice as loud at 40 Hz because of the drop off in our ear's sensitivity at low frequencies.

Bigger speakers often, not always but often, have greater bass extension so the odds are that a bigger speaker will actually make things worse for the neighbour but the issue isn't the size of the speaker, it's just how much bass extension it has.

And as has been said previously, the big problem with low level listening is that you need a bass boost in order to compensate for the drop in the ear's sensitivity at low frequencies in order to keep the tonal balance between bass and midrange sounding natural. Whatever speaker you have, the more you turn the level down, the more bass boost you need to get a satisfying result. That increases the level of bass in your room and that increases the problem in your neighbour's room. 

We've also mentioned speakers can need to be driven to different levels before they "wake up". Let's say you like a level of 70 dB when listening at low level. For reference 65 dB is around the level of a speaking voice at normal conversation distances. If your speaker "wakes up" at 65 dB, then things are great, it's working comfortably at that level, but if it doesn't "wake up" until the level is 75 dB then you're probably going to find yourself listening at 75 dB instead of 70 which makes things worse for the neighbour. A speaker that "wakes up" at a lower level than your preferred low listening level is going to be beneficial and a speaker that "wakes up" at a higher level than your preferred low listening level is going to be be a problem when it comes to keeping the neighbour happy because you're going to want to play it at a level where it has "woken up".

Now to speaker isolation. Speaker isolation reduces the transmission of sound to the neighbour's apartment by reducing the amount of energy transmitted directly from the speaker to your floor and then by a continuous physical transmission path to the neighbour's apartment. Speaker isolation can increase the value of x in my examples above but it will only do so if there's that unbroken physical transmission path to the neighbour's apartment. If you don't have the transmission path then speaker isolation isn't going have an effect on the value of x and there will be little or no change in the sound reaching the neighbour's apartment. As I've said earlier there are several paths by which sound can reach the neighbour's apartment and in order to reduce the level of sound reaching the neighbour when you're listening at whatever level you want to listen at, you have to increase the value of x in the examples above. You can only do that by changing something in the path or paths that the sound reaching the neighbour's apartment travels by. Changing a path that the sound isn't taking won't help, you have to change the paths that the sound actually takes and increase the energy losses along those paths so that the value of x becomes greater.

So we essentially need to try some isolation, and potentially as part of the speaker search, look for those that wake up at a lower level.  Size isn't the issue.  I have a dB meter on my phone, and it does seem that mid-70s dB is where my current set wake up.  Not more than 80.  

There's no connected ductwork, but I'm having maintenance come in and add extra insulation to the inside of the outlets, as some are producing a draft.  I'm not sticking anything on the ceiling.  As I look now, though, I can see that there are two outlets flanking each side of my speakers.  Perhaps we've found a culprit.  Actually, there are 6 entry points for sound (outlets, ethernet, TV mount points) on one side and one entry point on the other.  I may see if they can fill these with foam.  The speakers also aim at a handful of outlets as well.  Or just bite the bullet and cover the outlets on both sides with a wall treatment.

I'm wondering, since I've been more enthralled with Roon since the 1.6 update, if I could have a nighttime DSP that would be tolerable and would eliminate complaints, similar to what the Phantom Premier offers.