How to pressurise a room

[Mike13]

Can anyone help with this?

 

It’s done by subs from what I’ve been told. I have two Rel T9i’s but I don’t feel like it is pressurised. Do I need bigger/more subs?

 

My room is 10L x 4.3W x 3H with a L-shaped kitchen section that’s 3 x 3.8 x 2.

 

149.2 cubic metres (5269 cubic feet).

 

Is there a rough formula for sub size and output to cubic metres?

 

Thanks!

Edited July 3, 2018 by Mike13
clarification

[bjc]

You need to seal a room to pressurise it. Your room is massive with a kitchen also so I doubt it's possible unless you buy bulk 18 inch subs.

[blybo]

1 hour ago, Mike13 said:

Can anyone help with this?

 

It’s done by subs from what I’ve been told. I have two Rel T9i’s but I don’t feel like it is pressurised. Do I need bigger/more subs?

 

My room is 10L x 4.3W x 3H with a L-shaped kitchen section that’s 3 x 3.8 x 2.

 

149.2 cubic metres (5269 cubic feet).

 

Thanks!

It's not a pi55ing contest but I have a similar but slightly bigger room also with a hall running off it. I can hear my single Rel S3 which is in a corner to get some boundary gain, but I certainly don't feel the sub, but I do feel bass in my adjoining 6x4m HT with twin subs, but I don't listen to music in there except for bluray concerts.

Edited July 3, 2018 by blybo

[Mike13]

Thanks @blybo. Your post in Darren’s thread was what prompted me. Can you hear a big difference when pressurised in your HT?

[Mike13]

31 minutes ago, bjc said:

You need to seal a room to pressurise it. Your room is massive with a kitchen also so I doubt it's possible unless you buy bulk 18 inch subs.

Thanks bjc. 18” is pretty big.

[Red Spade Audio]

If you want to FEEL the bass, there are two things you might be talking about. One is tactile bass in the midbass - this occurs around 40 - 60 Hz and you tend to experience it more in movies where the bass tends to have much less compression, so it is more dynamic. The other is very low bass, which gives a sense of pressure but not so much impact and punch. Many people think they need 20 Hz extension or lower when it's actually the midbass punch they want. It's actually good news where that is the case, because that is much easier to achieve.

 

This was illustrated in a calibration session recently, where the client was surprised to find that this tactile experience came not from adding extension but rather removing a big midbass dip. In this case, it was caused by the room and the solution was multiple subs in the right locations.

 

There is no useful formula here because the situation is too complex. It's a trial and error process. Keep in mind that it's not just about how much fire power you need. It's also about where you put your subs and how they interact with your room.

 

 

[blybo]

2 hours ago, Mike13 said:

Thanks @blybo. Your post in Darren’s thread was what prompted me. Can you hear a big difference when pressurised in your HT?

 

Hard comparison because it's set up for movies, not music. I find there is too much bass for music in my HT room but I can feel really low bass which is not so much heard as felt. I assume it is pressure waves I'm feeling. Our little friend @Red Spade Audio above positioned my subs for me a few years ago.

 

When the SVS PB2000 is really pumping I can also feel the puffs of air on my legs from 3m away

[bjc]

If you can I'd move your existing subs to nearfield first. Preferably directly behind (within 1mt) you but if not then either side of your seating position. I'm not sure if your subs are ported or sealed but nearfield imo is where it's at as they don't need to work half as hard for impact and the room is almost taken out of the equation. Corner loading is nice but I feel it bloats the sound (I've never measured it though) which is why I used 4 subs with 2 front and 2 rear. These were all sealed 12's with passive radiators. I've got my 4 18's now (2 more arriving soon) but they are still in the box until I build my HT again!
Suppose I should pull my finger out...

[hopefullguy]

sorry i am far from an expert but from my readings no 2x 10" subs will pressurise that size/shaped room. if you want to feel it in your chest then the rels go for some subs from peter at deep hz audio..and deep pockets.

 

or if you just want to get a bit more "feel" into your movies at a much reduced expense you could get some bass shakers.. sorry i am ducking the rocks that are being thrown.

 

dont knock em till you try em. they will make you think the subs are bigger than they are.. wont pound your chest but actually do what they say they do and are very cost effective (subject to aust dollar and any old avr with A+B switching will power them)

Edited July 3, 2018 by hopefullguy

[AudioGeek]

When done right you can feel your shirt flapping from the bass without hurting your ears or feeling uncomfortable.

Multiple subs really helps. I see in some of the newer HT setups they are even placing subs at different heights - often with at least one at almost ceiling height!

Much easier to pressurise the car!

[Mike13]

34 minutes ago, bjc said:

If you can I'd move your existing subs to nearfield first. Preferably directly behind (within 1mt) you but if not then either side of your seating position.

This I can do. Can also add a smaller 8”, not sure it would do much.

 

Build that theatre!

[Mike13]

@hopefullguy I’m more looking for music thanks.

 

@AudioGeek that’s what I’d like.

 

My corner positioning is a bit boomy. I’ve been meaning to move them out a bit. 

 

 

[mcb]

I have a pair of SVS PC13 Ultras and could not pressurise my room, as it is open on one side and leads into other areas.  As I was never going to be able to seal the area (short of pulling the house down and starting again),

i overcame the issue by putting together a pair of couch kickers  4x12" drivers powered by an INuke3000.

 

Our couch sits immediately in front of these.  The 2 PC13's and these two are then combined using a MiniDSP 2x4HD and MultiSubOptimiser (MSO).

 

Nothing like a good kidney massage

 

[Mike13]

@mcb nice. They look like a sub/speaker hybrid. 

[mcb]

They are actually car subs, which some bright spark figured out made a good cost effective sub for HT.  They are now discontinued.  https://www.sonicelectronix.com/item_18918_Infinity-Reference-1262W.html  There was a long thread on AVS regarding them, which is where I got the idea from.  Not sure what the equivalent they are using now is.

[davewantsmoore]

7 hours ago, Mike13 said:

but I don’t feel like it is pressurised

Even in a sealed room, you will not feel it unless it is quite low and loud.   Below the rooms lowest mode, a monopole subwoofer will 'pressurise' the room.

 

Paul's post above is on the money.

[almikel]

In an old previous thread I tried various sized rooms both closed and open (but never "sealed") to investigate the differences in low bass that could be achieved. 

As Dave says

On 03/07/2018 at 7:19 PM, davewantsmoore said:

Below the rooms lowest mode, a monopole subwoofer will 'pressurise' the room.

Below the lowest modal frequency in the room, you enter the "pressure" zone for the room.

The theory applies very well for sealed speaker boxes (a very small room), because the "room" is sealed, and you have large cone area compared to "room" size.

 

Increase scale to a real room, IME you won't be able to get sufficient room sealing and cone radiating area to leverage the "pressure" zone to achieve lower bass by pressurising the room.

 

In my experiments with "normal" rooms that weren't airtight, I could never achieve the deeper bass that was theoretically achievable in a "sealed" room by pressurisation,  but I also learned that much deeper bass could be achieved in the room than "popular" theories saying the lowest bass is determined by the longest room dimension/lowest mode.

 

Forget room pressurisation as a criteria for achieving good "in room" bass. Just keep adding treatment and subs until it measures right.

 

cheers,

Mike

 

[davewantsmoore]

20 hours ago, almikel said:

Below the lowest modal frequency in the room, you enter the "pressure" zone for the room.

The theory applies very well for sealed speaker boxes (a very small room), because the "room" is sealed, and you have large cone area compared to "room" size.

Increase scale to a real room, IME you won't be able to get sufficient room sealing and cone radiating area to leverage the "pressure" zone to achieve lower bass by pressurising the room.

I feel you are confused about this....

 

All sound below the lowest room mode "pressurises the room"....  by this, it means that the wave is so large, that at all points in the room the pressure is rising/falling in unison.... ie. "the room is being pressurised".

 

The requirement for the 'room to be sealed' is not about 'building up pressure' as you might think about it.    It is that if the room is not sealed ... then there will exist a lower mode, and thus the whole 
"pressure rises and falls in unison all over the room" scenario won't be reached.

 

... but this is all semantics, and especially for this thread not useful.

 

20 hours ago, almikel said:

Forget room pressurisation

This is much better!     

 

On 03/07/2018 at 12:02 PM, Mike13 said:

Is there a rough formula for sub size and output to cubic metres?

Yes, but a critical parameter is "how loud".

 

Rather than thinking in terms of rules, or pressurisation, or anything.... ask:

 

Is my bass loud enough?

Is it low Hz enough?

(....and once you've turned it up)  Is it low distortion enough?  (as in "THD" type distortion)

(... and the most important one, IMHO)  Is it smooth enough?  (as in are you getting peaks a dips in the response, patches of no bass, or boomy frequencies, etc.)

 

 

[Mike13]

Thanks Dave and Mike. How sealed would the room need to be? For example is the gap under a sliding door going to ruin the seal?

 

I’ll add my 8” sub, reposition one of the other two next to the couch and see what that does.

 

Do bass traps have the opposite effect of removing bass?

[davewantsmoore]

1 hour ago, Mike13 said:

How sealed would the room need to be?

Complex question.   The answer won't help you lots though.... just go with Mike's advice  

 

1 hour ago, Mike13 said:

Do bass traps have the opposite effect of removing bass?

When sound bounces back and forth between the surfaces of your room .... it creates an interference pattern where in some locations certain frequencies will be reinforced (twice as loud), and some places canceled (zero), and everything in between.

 

Bass traps reduce this by absorbing the sound waves (and reducing the amount which bounces back).

[almikel]

On 05/07/2018 at 6:28 PM, Mike13 said:

Do bass traps have the opposite effect of removing bass?

Different words but same thing as @davewantsmooresaid - Bass traps reduce the "ring" time (reverb time) of bass frequencies bouncing around the room...

...so yes bass traps "remove" bass in a good way - by absorbing the bass you don't want - bouncing around the room many cycles after the speakers produced it.

Managing the room's bass response (the target being a smooth FR with even decay) is IMO much more important than any criteria on room pressurisation.

 

cheers

Mike