5 hz bass @ 125 db in room

[Kindhornman]

BHTX.
I have experienced that sensation many times with a sun roof open to a certain amount and it drives me crazy while others seem to be oblivious to the very low frequency buffeting. I just can't imagine trying to make such low frequency output myself, I find it terrible to have that affect. Not unlike needing to pop your ears when changing elevation. I have made some extreme double 18" bass horns that put out plenty of low bass but not that low as we used them for PA use outdoors and below a certain frequency you are going to have low frequency feedback for sure, so the very low frequencies are actually cut with a filter. Except for the body sensation which you can get at much higher frequency than 5hz I just don't see the point and I imagine that there are others like me that can't stand that. I would walk out of the room, this would not be an enjoyable experience for me at all. I guess I have better sensitivity to this than some, I pick up on it instantly.

[vacuphile]

Kindhornman, I know exactly what you mean with the open roof. The point you make about extreme bass is absolutely correct. The speakers I listen to now go into the high thirties - 3dB, and even then it may sometimes get uncomfortable for the random low rumble you have in much audio material. I am in the proces of designing an analog xover for this speaker, and it will have shelving high pass filter at the extreme low end to tune it to the room and the program material.

[JapanDave]

Kindhornman, I know what you are saying, a 5hz sine wave in my room can give you an unpleasant sensation if played for too long (Not that I regularly play 5hz sine waves). But , in the real world when experiencing 5hz in a movie it is a whole different feeling, not to mention it is usually only for a few seconds at most in any given movie that 'actually' has 5hz content.

[weltersys]

Originally Posted by JapanDave

Kindhornman, I know what you are saying, a 5hz sine wave in my room can give you an unpleasant sensation if played for too long (Not that I regularly play 5hz sine waves). But , in the real world when experiencing 5hz in a movie it is a whole different feeling, not to mention it is usually only for a few seconds at most in any given movie that 'actually' has 5hz content.

In the movies I have heard, the ultra LF signals used are always used to convey an "unpleasant sensation", whether it is supposed to be real (earthquakes, explosions, car crashes etc.) or psychological (ghosts, alien influence, mind games).
Either way, I find it does not take a whole lot of level to get the message across.

[Rullknufs]

A recording of the Tchaikovsky 1812 Overture I have on my computer has lots of information down to 6-7Hz when the cannons are firing.

[Kindhornman]

I truly believe that you are exaggerating the frequency response in a movie theater. First the majority of theaters are using JBL sound systems behind the screen, leaving out any side wall or rear wall speakers as they could not produce these low frequency waves, and I don't remember them ever specifying such low frequency output of 5hz. Second fact would be that in a multiplex, the majority of theaters these days, you could never contain those low frequencies, everyone in the next theater over would hear all that sound bleeding into the other theaters and this would include just about every other screen in the theater, not just the adjacent screen. I have built bass horns that were used in a club and people down the block were complaining about the sub harmonics that were rearing their ugly head in a different building through conduction in the ground. It is next to impossible to isolate these sounds, this is a problem even in anechoic chambers and recording studios even with floating foundations. You do not have to hit 5hz to feel the impact of an earthquake and other low frequency illusions. Not necessary.

[weltersys]

Originally Posted by Kindhornman

I truly believe that you are exaggerating the frequency response in a movie theater.
You do not have to hit 5hz to feel the impact of an earthquake and other low frequency illusions.

Kindhornman,
So far, you are the only person that has mentioned commercial theater systems which certainly don't go as low as the home theater systems Josh or Dave have.

Even my moderate 2x12" home theater sub goes well below the THX standard, though not as loud.

You are correct that a speaker system does not have to hit 5hz to feel the impact of an earthquake and other low frequency illusions, but one that can is more accurate reproducing a recording containing those frequencies than one that can't, whether "needed" or not.

Art

[Kindhornman]

Art,
What I see now happening in the commercial theaters is they are now adding shakers to the seating to give the illusion of those very low frequencies, not through the air but through actual vibration transfer into your butt. In a home I would worry about things vibrating off of shelves and you would sure find out quickly if your wife or girlfriend was dusting well as it starts to fall from places you never thought of before! I had that experience in a famous club here in Los Angeles when we brought in some low frequency horns and proceeded to cover everyone with the dust accumulated on the exposed ducting above the audience. Those got shut down rather quickly!

[Severianb]

Originally Posted by Kindhornman

Art,
What I see now happening in the commercial theaters is they are now adding shakers to the seating to give the illusion of those very low frequencies, not through the air but through actual vibration transfer into your butt. In a home I would worry about things vibrating off of shelves and you would sure find out quickly if your wife or girlfriend was dusting well as it starts to fall from places you never thought of before! I had that experience in a famous club here in Los Angeles when we brought in some low frequency horns and proceeded to cover everyone with the dust accumulated on the exposed ducting above the audience. Those got shut down rather quickly!

I have sat in quite a few of those theaters with the tactile transducers in the seats.

I can also tell you my infinite baffle subwoofer creates the same effect, but BETTER. It's better because it's reproducing the whole range of sound, smoothly and without distortion.

And please people, unless you have experienced a movie with ULF material played on a system capable of decent volumes down near 5hz... stop saying how useless or uncomfortable or worthless it is.

My IB system absolutely floors everyone who hears/feels it. That, of course, is the ULF part, the part that pressurizes the room and shakes the floor. It adds a LOT to movies and music that have it. After all, it's the artist's intent.
The more subtle part of an IB is the clairity of the sound. Subwoofer have got a bad rap from audiphiles because of the distortion. IB subs have very little.

And another bone of contention with many of the comments in this thread, describing the huge amounts of money and drivers needed to experience ULF. In a normal sized home theater, room gain makes those needs much smaller.
My sealed 1700 cubic foot room is easily filled by four 18" FiCar IB3 drivers in dual manifolds with 500 watts going to each driver. About $1500 (U.S.) total.