11-Feb-2019, 01:54
Sound can get to another apartment in 3 ways: physical transmission of vibration, sound travelling through walls/floors/ceilings, and sound travelling through air channels such as linked ductwork connecting the apartments. Depending on construction either one, two, or all 3 of those methods may be involved. Isolating the speakers from the floor reduces transmission to the floor. If the floor is physically connected to supports that are also physically connected to surfaces in another apartment, even in an apartment above you, then physical vibration can travel from your floor to the other apartment and isolating your speakers from the floor could reduce the transmission of bass to the other apartment. If there's no continuous physical path for the vibration to use to reach the other apartment then isolating speakers from the floor is unlikely to be beneficial and the sound will almost certainly be getting to the other apartment by some other route.
Isolation is tricky. A lot of isolation devices are essentially springs which are used to decouple one thing from another thing. Springs can't provide complete decoupling. Springs have a resonant frequency. Let's say your speakers have rolled off to inaudibility or near inaudibility in the bass by 30 Hz (I'm picking that figure for ease of calculation). It's unlikely that bass below 30 Hz is going to be a problem for the neighbours because the speakers simply aren't producing significant bass below 30 Hz so you want to stop bass above 30 Hz getting to the neighbouring apartment. If the isolation device you choose is essentially a spring it will have a resonant frequency so say it has a resonant frequency of 30 Hz. It will actually transmit and magnify the bass at that frequency, after all it's resonating at that frequency, so the bass reaching the neighbour's apartment through a physical vibration path could become greater than what you hear in your apartment. Springs don't start to isolate until the frequency is around 1.4 times the resonant frequency so the isolator won't start to provide isolation below 42 Hz. At 43 Hz it will essentially pass the same level of vibration reaching it from the speaker. As the frequency rises above 42 Hz you start to get a reduction in transmission and the amount of reduction increases as frequency increases. If you want to reduce transmission at 30 Hz you need a spring with a resonant frequency of 20 Hz or less. With a resonant frequency of 20 Hz you won't start to get a reduction in transmission of vibration below 28 Hz and transmission will be magnified down to 20 Hz when it peaks and then starts to decline. What this means is that if your isolation device is a spring mechanism of some kind, and that includes things like springy rubber pucks and the like, you need to ensure that the device has a resonant frequency that is as low as possible, and much lower than the bass that's causing the problem. If you can't do that then you may actually make the problem worse.
That's why I suggested you look at devices that are intended to isolate subs. In order for those devices to work they have to be designed to actually reduce vibration transfer at frequencies subs are capable of producing and that means at frequencies which will be lower than your speakers can produce. There are some foot type isolation products intended for use to isolate subs and they will definitely be capable of isolating your speakers. Isolation devices often don't supply information about the frequencies at which they provide isolation or about how what frequencies they provide isolation at. Even when they do provide information, at times that information can be less than accurate. It's much harder to provide isolation at low frequencies and smaller devices tend to be less capable of isolation at lower frequencies than larger devices.
Heavy mass doesn't necessarily provide isolation at low frequencies. This planet is very heavy in mass yet low frequency vibration from earthquakes can travel around the world and be picked up by seismic sensors several continents away so mass alone won't do necessarily do the trick. Things like cement garden slabs and marble blocks on their owncan actually be reasonable carriers of bass vibration.
If your transmission path is actually sound passing through your ceiling to the apartment above or through common ductwork linking the apartments then your job is going to be a lot more difficult.
Isolation is tricky. A lot of isolation devices are essentially springs which are used to decouple one thing from another thing. Springs can't provide complete decoupling. Springs have a resonant frequency. Let's say your speakers have rolled off to inaudibility or near inaudibility in the bass by 30 Hz (I'm picking that figure for ease of calculation). It's unlikely that bass below 30 Hz is going to be a problem for the neighbours because the speakers simply aren't producing significant bass below 30 Hz so you want to stop bass above 30 Hz getting to the neighbouring apartment. If the isolation device you choose is essentially a spring it will have a resonant frequency so say it has a resonant frequency of 30 Hz. It will actually transmit and magnify the bass at that frequency, after all it's resonating at that frequency, so the bass reaching the neighbour's apartment through a physical vibration path could become greater than what you hear in your apartment. Springs don't start to isolate until the frequency is around 1.4 times the resonant frequency so the isolator won't start to provide isolation below 42 Hz. At 43 Hz it will essentially pass the same level of vibration reaching it from the speaker. As the frequency rises above 42 Hz you start to get a reduction in transmission and the amount of reduction increases as frequency increases. If you want to reduce transmission at 30 Hz you need a spring with a resonant frequency of 20 Hz or less. With a resonant frequency of 20 Hz you won't start to get a reduction in transmission of vibration below 28 Hz and transmission will be magnified down to 20 Hz when it peaks and then starts to decline. What this means is that if your isolation device is a spring mechanism of some kind, and that includes things like springy rubber pucks and the like, you need to ensure that the device has a resonant frequency that is as low as possible, and much lower than the bass that's causing the problem. If you can't do that then you may actually make the problem worse.
That's why I suggested you look at devices that are intended to isolate subs. In order for those devices to work they have to be designed to actually reduce vibration transfer at frequencies subs are capable of producing and that means at frequencies which will be lower than your speakers can produce. There are some foot type isolation products intended for use to isolate subs and they will definitely be capable of isolating your speakers. Isolation devices often don't supply information about the frequencies at which they provide isolation or about how what frequencies they provide isolation at. Even when they do provide information, at times that information can be less than accurate. It's much harder to provide isolation at low frequencies and smaller devices tend to be less capable of isolation at lower frequencies than larger devices.
Heavy mass doesn't necessarily provide isolation at low frequencies. This planet is very heavy in mass yet low frequency vibration from earthquakes can travel around the world and be picked up by seismic sensors several continents away so mass alone won't do necessarily do the trick. Things like cement garden slabs and marble blocks on their owncan actually be reasonable carriers of bass vibration.
If your transmission path is actually sound passing through your ceiling to the apartment above or through common ductwork linking the apartments then your job is going to be a lot more difficult.
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
