Next up: What is room pressurization?

[FrantzM]

When things start moving around your room and falling off of shelves, your room is pressurized. When you can feel pressure on your chest and your pant legs moving, your room is pressurized. Different bass wavelengths (different frequencies) cause different effects to be felt and heard. The tighter the room and the lower the bass that you can reproduce will cause different pressurization effects.

There is another effect that I will call *excitation* for lack of a better word, and that is when you feel like the air molecules in your room are energized. This is more of a high frequency phenomena and maybe the opposite of pressurization. I can give you one good example of a recording that is capable of letting you hear this. There is a country tribute album to the Beatles called “Come Together, America Salutes the Beatles.” It’s mainly a bunch of country and western yahoo artists, but there are a few good cuts. The cut that can excite the air molecules in your room with high frequencies is “We Can Work it Out” by Phil Keaggy & PFR. Nice cover by the way.

mep

There are conditions under which the room is really pressurized. I did try to outline these in my previous post. I stated that it is not a function of bass response only. You can have great bass response , yet no room pressurization... For Room pressurization to occur, the room must be relatively well sealed. Sealing a room is not just closing the doors.. Sound will escape even through the walls ... depending on the room construction ... So the sealing of the room has to extend to the lower frequencies, n always difficult proposition but do-able, nonetheless.

The phenomenon of Room Pressurization is known and not as prevalent as many would think.. Good room sealing at the frequencies where the pressurization occurs is the requisite there ... and the woofer loading ... The vast majority of subwoofers are either sealed, bass reflex or bandpass , few are trly dipoles so they can under the right conditions (sealed rooms, substantial woofer displacement and of course right material) pressurize the room.
I am somewhat beating my head on the subject and will have to drop it but I know that Room Pressurization is less common than people think and it shouldn't be confused with room gain , a completely different phenomenon, or good bass response which is what you are describing here ...
Wish I had the command of someone like Tom Danley or Mark Seaton on the subject.. Guys where are you !!

 

[fas42]

There is another effect that I will call *excitation* for lack of a better word, and that is when you feel like the air molecules in your room are energized. This is more of a high frequency phenomena and maybe the opposite of pressurization. I can give you one good example of a recording that is capable of letting you hear this. There is a country tribute album to the Beatles called “Come Together, America Salutes the Beatles.” It’s mainly a bunch of country and western yahoo artists, but there are a few good cuts. The cut that can excite the air molecules in your room with high frequencies is “We Can Work it Out” by Phil Keaggy & PFR. Nice cover by the way.

I think Mark's on the right track here. I only discovered this concept of "pressurisation" since coming on board this forum, had never heard it mentioned elsewhere before. When I queried the post when it was mentioned it was quite clear that the person meant it to refer to intensity of sound, combined with quality of sound. Those two go hand in hand: virtually any half reasonable system can produce intensity by upping the volume control, but any emotional or positive impact is ruined by the level of distortion that is obvious. But when a system is capable of generating clean SPLs at a certain minimum level then Mark's excitation, or pressurisation not solely dependant on bass, occurs. Roger has mentioned many times that the apparent volume of his system varies depending on the quality: I'm very familiar with this phenomenon, and it's part of the process of excitation, which I feel is a more appropriate descriptive term.

As a simple example, when my system is working well, then "excitation" occurs very easily. But if the audio loses its "touch" then that excitation factor completely disappears, it just becomes tedious to listen to: there's too much apparent distortion and the ear/brain fails to couple agreeably with the sound.

Which is why I would suggest a lot of people have trouble with getting digital to do it: it is very difficult to eliminate that last edge of a certain type of distortion in the playback of digital, and so the illusion fails; the excitation, or pressurisation does not take place.

Frank

 

[fas42]

I know that Room Pressurization is less common than people think and it shouldn't be confused with room gain , a completely different phenomenon, or good bass response which is what you are describing here ...
Wish I had the command of someone like Tom Danley or Mark Seaton on the subject.. Guys where are you !!

Hello, we have another one!!!

"What is room gain?"

Frank

 

[NorthStar]

Room Gain is when you add a new addition to your room; by making it larger?

 

[Soundproof]

Room gain is not a mystery - the acoustics of a concert hall are designed to direct and redirect the acoustic energy of the orchestra, amplifying the energy that reaches the listeners. In open air, the enery dissipates in many directions, and there is no room gain - in a structured space, you achieve a room gain effect.
Here's an interesting link that discusses the acoustics of two concert halls in Stockholm, Sweden, where the author stresses this "room gain" factor, calling it amplification:
http://www.torgny.biz/Room acoustics_1.htm

However, to prove the importance of subjective impressions, here's another paper that in detail describes the impressions of the musicians working in those two concert halls, as they were asked to evaluate the acoustics of their halls - from their working vantage point, and from selected evaluation points in the hall, as changes were made. Very interesting reading:
PDF - http://www.google.no/url?sa=t&rct=j...sg=AFQjCNGmORNnpsQnwr9JgK9c9A_efO_ZAQ&cad=rja

 

[NorthStar]

Oops! :b

* Anyone seen that girl I was with just few minutes ago?
...She seems to have disappear suddenly.
Pressure is mounting ... :b

 

[microstrip]

IN order to center the discussion we may have to abide to ONE definition of Room Pressurization .. . .

Frantz

OK, I understand what you mean - we will need an alternative thread for other "audiophile" definitions. Let us assume that this is what Tim wants. Please help defining it. Or is just 3 large long throw subs, solid walls and a lot of sealing tape?

BTW, a quick calculus suggests dV max = 20 liter, V room = 100.000l , the maximal variation in pressure will be about 0.2 mBar (20 pascal for SI people - I hope I did not made any mistake in the calculus ) . Is this the recipe?

 

[mep]

Frantz-I hear what you are saying. My room is 9’ below ground and the walls are poured concrete and are insulated on the outside and inside of the foundation. Then the walls are studded and sheet-rocked. I have a pair of French doors that open into my utility room off to the left of my sitting position where the “L” in my “L” shaped room is. I can’t close those doors all of the way against their stops because on certain songs, the pressure in the room from low bass makes those doors rattle against their stops. To me, if you can feel pressure, your room has to be pressurized. I think due to the construction, my room is very tight and is better able to sustain the pressure of the bass waves.

 

[NorthStar]

That's strange; I experienced intense pressurization before in a room with a large door opening to the rest of the house.

Mind you though; you could feel that pressurization at certain spots more than others, but still some pressurization in those null spots.

Makes any sense?

 

[Phelonious Ponk]

Hello, we have another one!!!

"What is room gain?"

Frank

What is room gain? Are you serious?

Tim

 

[Phelonious Ponk]

Frantz

OK, I understand what you mean - we will need an alternative thread for other "audiophile" definitions. Let us assume that this is what Tim wants. Please help defining it. Or is just 3 large long throw subs, solid walls and a lot of sealing tape?

BTW, a quick calculus suggests dV max = 20 liter, V room = 100.000l , the maximal variation in pressure will be about 0.2 mBar (20 pascal for SI people - I hope I did not made any mistake in the calculus ) . Is this the recipe?

Tim doesn't know what he wants and is a long-time admirer of thread drift. Take it away!

Tim

 

[fas42]

What is room gain? Are you serious?

Tim

It's obviously about reflections, early, late, or whatever, altering the quality of sound in the room, both in an objective, measured sense, and also a subjective, experience enhancing sense. So what may be debatable when people use that term is whether they mean "gain" in the sense of upping the dBs, objectively or subjectively, or in the sense of "improving", achieving a "gain" in quality ...

Frank

 

[RogerD]

Ok, I'll ask a question. How can you tell if a room is over pressured at moderate volume? and if it is so,is that because of the speaker size?

Put it another way, if you have experienced an over pressurised room.what kind of distortions were present and I'm not talking about stuff falling of shelves.

 

[Phelonious Ponk]

It's obviously about reflections, early, late, or whatever, altering the quality of sound in the room, both in an objective, measured sense, and also a subjective, experience enhancing sense. So what may be debatable when people use that term is whether they mean "gain" in the sense of upping the dBs, objectively or subjectively, or in the sense of "improving", achieving a "gain" in quality ...

Frank

Not really, no.

Tim

 

[microstrip]

I picked this text from IAR80 available online:

In the concert hall, you hear both pressure and velocity components of the sounds produced by the live musical instruments, but microphones capture and record only the pressure component, and most loudspeakers can only play the pressure component. It has been hypothesized that one of the barriers, preventing reproduced sound from truly seeming like the real thing, has been the fact that reproduced sound lacks this velocity component that you hear from live music. Bass is particularly bad in this regard, since our bass systems only pressurize a room (single mono subwoofers are especially bad in this regard, which is why we so strongly recommend you use at least two widely spaced subwoofers).
The W1, if oriented precisely as we recommend, can provide a perceived sense of this sorely missing velocity component for bass, thereby making bass sound more naturally real and lifelike. It's not the full fledged real thing, since the velocity component was not recorded in any one channel, and so does not exist in any one channel for a single W1 to reproduce. But it still helps the natural veracity of the experience to be hearing a velocity component in your room's air from each subwoofer, as opposed to a conventional subwoofer that just pumps pressure at you.
And this sense of experiencing velocity is dramatically further enhanced when you employ two or more widely spaced subwoofers, reproducing stereo or surround bass from distinctly recorded channels. That's because the velocity component of bass can be recorded by two or more widely spaced microphones, which can pick up the propagation velocity of the bass wave as it wafts across a large hall, and you can reproduce this wafting velocity effect by employing two or more widely spaced subwoofers to play back the two or more recorded channels, jointly containing between them this recorded velocity propagation.

I have never heard about this effect. Just a way of selling more subs? Any comments?

 

[FrantzM]

Soundproof

We may , again talking about a different concept this is related to small room acoustics not for venues as large as a concert hall. I am not entirely in my element. Let's suppose a radiator outside ina yard far from any boundaries.. This kind of space is caled 4 -pi the transducer/speaker wave radiates freely with nothing in their path to fold them and redirect them ... If you put the same radiator in a room, say in a corner then you have the waves reflecting on the boundaries and reinforcing each other , especially at low frequencies where our ear-brain apparatus takes a little while to process the whole thing, up to 50 ms... This phenomenon is called room gain and can be substantial. Upward of 6 dB in most cases to convince yourself take your trusty SPL meter and move any subwoofer in a corner you wil likely see an increase in apparent output at (certain) low frequencies ...
There is another closely related phenomenon called vessel-gain .. This is a phenomenon by which at a certain frequency the room is too small to support standing waves, IOW the wavelength of the signal/wave/sound s greater than the room larger dimension .. resulting in that direction in uniform pressurization ...(there comes that word again) ... This usually happen in the low frequency an if the transducer is is adequate, read monopole at that frequency, you get uniform pressurization, assuming the room is reasonably well sealed at that particular frequency and the musical content, contain this range of frequency etc...
From all of that you can see there can ver various frequencies all of them low at which such could occur and for the effect to be felt the SPL has to be there as well. in a car yuo get both, very easily , in a room you can get them but the sealing is not always that good ...
Room pressurization is not an audiophile concept it has a clear, physical reality and meaning. The reason why with the Rotary woofer you will feel it very easily is that the resonant frequency of this superb subwoofer is very low I think it is 0.1 Hz or something. This sub is a monopole in all its range and its output is extraordinary .. You can get that with an IB ... or truly any subwoofer as long as the frequcny i well reproduced and higher than the resonant frequency of the sub driver ..Of course output has to be adequate and room has to be sealed... ooof

I still would like experts such a Mark Seaton, Nyal Melior, Tom Danley, etc to chime in they may explain it much better than I did but I hope you get the gist..

 

[NorthStar]

Here's my WAG....

1. Because of the way LP's are cut, bass becomes mono and the cross-talk/interaction between the 2 signals, maybe contain signals out of phase?

2. LP has rumble below 10Hz

3. R2R has wow/flutter?

4. Feedback?

Ok, I'll ask a question. How can you tell if a room is over pressured at moderate volume? and if it is so,is that because of the speaker size?

Put it another way, if you have exoerienced a over pressurised room.what kind of distortions were present and I'm not talking about stuff falling of shelves.

The first quote above?

P.S. Roger, you gotta watch for those typos man! :b

 

[fas42]

Not really, no.

Tim

Okay, so what is it?

Is this irrelevant:

The first reflections will give the sound its details and live feeling. In addition, in a big concert hall, it is important that the first reflexes come from the sidewalls. This behaviour is called lateral reflections. This will give the listeners the impression of being surrounded by sound and immersed in the music. In the Berwald hall, you can see that the actual sound from the hall is of a mono-type quality, which is also clear if you sit in front of the orchestra. It is not a “stereo-sound” that you will hear. If you visit the hall, I recommend that you sit on the side of the hall in the first row, so as to enhance your experience.

Frank

 

[fas42]

But it still helps the natural veracity of the experience to be hearing a velocity component in your room's air from each subwoofer, as opposed to a conventional subwoofer that just pumps pressure at you.

It sounds mumbo jumbo to me. What makes bass work for me is the treble working correctly; without that the bass notes are just a plodding rumble. Jazz acoustic bass only develops the correct bite and edge if that top end is filling in correctly.

Frank

 

[FrantzM]

I picked this text from IAR80 available online:

In the concert hall, you hear both pressure and velocity components of the sounds produced by the live musical instruments, but microphones capture and record only the pressure component, and most loudspeakers can only play the pressure component. It has been hypothesized that one of the barriers, preventing reproduced sound from truly seeming like the real thing, has been the fact that reproduced sound lacks this velocity component that you hear from live music. Bass is particularly bad in this regard, since our bass systems only pressurize a room (single mono subwoofers are especially bad in this regard, which is why we so strongly recommend you use at least two widely spaced subwoofers).
The W1, if oriented precisely as we recommend, can provide a perceived sense of this sorely missing velocity component for bass, thereby making bass sound more naturally real and lifelike. It's not the full fledged real thing, since the velocity component was not recorded in any one channel, and so does not exist in any one channel for a single W1 to reproduce. But it still helps the natural veracity of the experience to be hearing a velocity component in your room's air from each subwoofer, as opposed to a conventional subwoofer that just pumps pressure at you.
And this sense of experiencing velocity is dramatically further enhanced when you employ two or more widely spaced subwoofers, reproducing stereo or surround bass from distinctly recorded channels. That's because the velocity component of bass can be recorded by two or more widely spaced microphones, which can pick up the propagation velocity of the bass wave as it wafts across a large hall, and you can reproduce this wafting velocity effect by employing two or more widely spaced subwoofers to play back the two or more recorded channels, jointly containing between them this recorded velocity propagation.

I have never heard about this effect. Just a way of selling more subs? Any comments?

There is a relationship between the velocity and pressure in a fluid ... If you know the pressure then you can derive the velocity of the fluid flow ...

This paragraph sounds scientific but it is not .. What "velocity" are they talking about? Velocity of what? How do two subs make up for the velocity component which can be derived from the pressure anyway or its variations at a given point? Not sure but looks like a mumbo-jumbo to sell subwoofers ...
Then again i am for more than 2 subs so ...