Why aren't cinemas targeting sub 20hz response?

[sigbergaudio]

I'm curious to hear opinions on how deep home theater / consumer subwoofers should dig? I'm looking at equipment from JBL Pro for small cinemas, and their 2x18" subwoofer naturally goes to 22hz at -10dB, and can achieve down to 22hz -3dB with external EQ.

I'm pretty sure a properly setup cinema with (enough of) these subwoofers give a pretty good experience. So why do we need subwoofers that go deeper at home? Is it because at the cinemas they typically have a number of subwoofers, so in reality they have a lot of content below that as well, while at home we perhaps only have one or two, and thus need even the single subwoofer to have a more extended response?

The JBL Subwoofer for reference https://jblpro.com/en/products/4642a

 

[Blumlein 88]

Our hearing stops at 20 hz. Seems enough if subs do the same. I seem to remember one reason is with hearing below 20 hz we'd hear our joints creaking.

Plus there is the chance to make people sick, queasy or see illusions at high levels below 20 hz.

 

[Vini darko]

https://deafbonce.com/uk/subwoofers/deafbonce-db-832neo
Grab a couple of these and never worry about bass again

 

[Frank Dernie]

https://deafbonce.com/uk/subwoofers/deafbonce-db-832neo
Grab a couple of these and never worry about bass again

120kg and intended for a car!
I wouldn't add anything weighing 120kg to a car, but then, I spent my whole carreer trying to make cars as light as possible.

 

[MZKM]

Let’s say a theater is 40ft•80ft•30ft, that is almost 100,000 cubic feet.
A nice home theater may be upwards of 3000 cubic feet, that means a regular theater (forget IMAX & Dolby) is >30x the cubic volume.

That is simply too much volume to get appreciable response down to even 20Hz. The loudest sub at 20Hz that Data-Bass has measured is the ZOD MAUL, which is a quadruple 19” sub where each driver is $2000, and that achieved almost 130dB @ 20Hz.

 

[Jimbob54]

120kg and intended for a car!
I wouldn't add anything weighing 120kg to a car, but then, I spent my whole carreer trying to make cars as light as possible.

Ever think about taking 2 of the wheels off?

 

[sigbergaudio]

Let’s say a theater is 40ft•80ft•30ft, that is almost 100,000 cubic feet.
A nice home theater may be upwards of 3000 cubic feet, that means a regular theater (forget IMAX & Dolby) is >30x the cubic volume.

That is simply too much volume to get appreciable response down to even 20Hz. The loudest sub at 20Hz that Data-Bass has measured is the ZOD MAUL, which is a quadruple 19” sub where each driver is $2000, and that achieved almost 130dB @ 20Hz.

So the reason we go deeper is essentially "because we can" ? - Or on the flip side, the cinemas would go deeper if it was feasible?

 

[Frank Dernie]

Ever think about taking 2 of the wheels off?

That would be less than 120kg in the cars i was designing.
In fact for a reasonable period the engine weighed less than 120kg.

 

[sergeauckland]

One issue that may need addressing is that of disturbance to neighbours. The lower the frequency the harder it is to keep it where it belongs. Any cinema in an urban area or indeed, multi-screen cinema in one location, will have serious problems with sound spillage. I would expect local authorities to take a dim view of any cinema that created serious disturbance to local inhabitants, and indeed customers who couldn't hear dialogue in one screen for the LF noise coming from the next screen in the same complex.

S.

 

[FrantzM]

To fill up the volume, those large venues use several subwoofers.. then the overall response would likely be lower than that of one sub,

 

[Fluffy]

20 hz is not a magical barrier where we suddenly stop hearing sounds. There is a gradual shift from hearing with the ears to feeling with the rest of the body, and it starts at a higher frequency, and extends lower than 20 hz. It doesn't really matter if a speaker is exactly -3 db at 20 hz – it's not like you can tell between 19 and 20 hz. These subwoofers specs should be taken more generally to reflect how relatively low it can get and with how much approximate power, and not to scrutinize every individual hz of response.

 

[astr0b0y]

Most cinemas I’ve been too lately have pretty lacklustre sub output (Imax excluded) but I did notice that a few have a buttkicker under every second seat.

 

[sigbergaudio]

20 hz is not a magical barrier where we suddenly stop hearing sounds. There is a gradual shift from hearing with the ears to feeling with the rest of the body, and it starts at a higher frequency, and extends lower than 20 hz. It doesn't really matter if a speaker is exactly -3 db at 20 hz – it's not like you can tell between 19 and 20 hz. These subwoofers specs should be taken more generally to reflect how relatively low it can get and with how much approximate power, and not to scrutinize every individual hz of response.

I'm aware of that, I was mainly commenting on the fact that a professional cinema subwoofer is apparently happy to stop above 20hz, while many work hard to get sub-20hz response in their rooms. So would it for instance be better to work on achieving higher SPL between ~20-30hz and worry less below 20hz?

 

[Vini darko]

120kg and intended for a car!
I wouldn't add anything weighing 120kg to a car, but then, I spent my whole carreer trying to make cars as light as possible.

Yeah basshead culture is...unconventional.

 

[Fluffy]

I'm aware of that, I was mainly commenting on the fact that a professional cinema subwoofer is apparently happy to stop above 20hz, while many work hard to get sub-20hz response in their rooms. So would it for instance be better to work on achieving higher SPL between ~20-30hz and worry less below 20hz?

but it doesn’t just "stop" at 20 hz, it's not a vertical filter that cuts off everything below that. if you put 15 hz through that speaker, you'll still get something.

 

[sigbergaudio]

but it doesn’t just "stop" at 20 hz, it's not a vertical filter that cuts off everything below that. if you put 15 hz through that speaker, you'll still get something.

Yes, I am aware of that too. But to use the JBL sub I referenced as an example, they recommend a 24db/octave high pass filter from 20hz, which comes on top of the 24db/octave natural rolloff below the port frequency, which means 48dB/octave roll-off. So it is actually cutting pretty steep.

 

[Fluffy]

Personally I think the pursuit of ever-lower hz in subwoofers is silly. If the music/movie isn't good without sub 30 hz content, more BASS won't fix anything.

 

[MZKM]

One issue that may need addressing is that of disturbance to neighbours. The lower the frequency the harder it is to keep it where it belongs. Any cinema in an urban area or indeed, multi-screen cinema in one location, will have serious problems with sound spillage. I would expect local authorities to take a dim view of any cinema that created serious disturbance to local inhabitants, and indeed customers who couldn't hear dialogue in one screen for the LF noise coming from the next screen in the same complex.

S.

I don’t know what theaters you go to, but all of mine have pretty decent isolation, all the walls are concrete. The exception is when I’m in the auditorium next to the Dolby Cinema and there is an action movie, then you can sometimes hear the bass coming thru.

 

[SIY]

I wouldn't add anything weighing 120kg to a car....

So I shouldn't count on you for a ride?

 

[Blumlein 88]

but it doesn’t just "stop" at 20 hz, it's not a vertical filter that cuts off everything below that. if you put 15 hz through that speaker, you'll still get something.

True of course. Some early texts on hearing listed human hearing as 40-16,000 hz. The hearing organ seemed designed for that. The response past each end was sort of like leaky filters.