Bass anechoic vs in-room

[Yorkshire Mouth]

Another school day for me.

I've just been watching one of Erin's typically great videos, this one being on the JBL 4329P.

In the video he says the speaker measures on the spinorama as going down to 30hz, but when you put in your room it'll go down to 20hz, dependent on the room.

Now I've heard this sort of thing before. Obviously, before anyone points it out, I know all rooms will be different, but I have a few questions.

1 - Whilst the amount may differ, will pretty much all rooms make a speaker go lower?
2 - Is room size the the dominant factor? As a general rule of thumb, will a larger room take it down lower and a smaller room less so, or the other way around?
3 - If you have your room treated (bass traps in corners, etc.), will this negate the effect, or does this deal with a completely different issue?
4 - Is the effect dependent in any way on the speaker, or is this purely how the room operates? In other words, if you put two different speakers, both going down to 30hz in the same room (at different times), and the room takes one of them down to 20hz, will the other speaker also go down to 20hz, or will the room always affect LF in the same way; is it completely room dependent?

Many thanks.

 

[alex-z]

The amount of room gain depends on the dimensions of the room. Bass has long wavelengths, which don't physically fit in a room, pressure builds up.

A larger room will have less room gain overall, requiring more capable subwoofers.

Most bass traps have no impact below 50Hz, and therefore have minimal impact on room gain.

The effect is purely room dependent, unless you have speakers or subwoofers capable of cardioid radiation pattern. This is exceptionally rare outside of live audience setups using pro audio gear.

 

[DJBonoBobo]

You can use the room sim in REW (Tools -> room sim). You can see a prediction how a speaker may behave in your room (edit: or any other virtual room). In this example if have entered a ported speaker with 50Hz (-3dB), close to the front wall. The graph shows, that you could probably expect some output up to 35Hz. In reality your room will behave different, but this is some way to play around a bit.

And here a real life example from my own room (Room sim vs actual measurment) - clearly different, but some correlation:

(From: https://www.audiosciencereview.com/...trol-dlbc-dual-kh750-subs.43054/#post-1524735)

 

[abdo123]

You can use the room sim in REW (Tools -> room sim). You can see a prediction how a speaker may behave in your room. In this example if have entered a ported speaker with 50Hz (-3dB), close to the front wall. The graph shows, that you could probably expect some output up to 35Hz. In reality your room will behave different, but this is some way to play around a bit.

View attachment 299156

And here a real life example from my own room (Room sim vs actual measurment) - clearly different, but some correlation:

(From: https://www.audiosciencereview.com/...trol-dlbc-dual-kh750-subs.43054/#post-1524735)

Did you not click on 'room is sealed'?

 

[DJBonoBobo]

Did you not click on 'room is sealed'?

I have indeed overlooked that option.

 

[Soniclife]

Room construction also matters, solid walls will reflect lots of bass, wooden construction will allow more bass to pass through.

 

[Curvature]

Analytical Analysis - Room Gain

-Introduction- The term 'room gain' is often seen used when the topic of subwoofers and the low frequency sound reproduction comes up. As I see many explanations that are lacking or incorrect, I thought I might try and clear up the topic once and for all. In all rooms there are so-called...

www.audiosciencereview.com

 

[Purité Audio]

Yes room construction a ‘limp’ room and there won’t be a great deal of bass returned, re size the larger the room the lower in frequency are any standing waves.
Keith

 

[Yorkshire Mouth]

This is all great, and thanks to everyone for their contributions.

But could you use the above to answer my 4 questions (see the first post).

Many thanks.

 

[DJBonoBobo]

This is all great, and thanks to everyone for their contributions.

But could you use the above to answer my 4 questions (see the first post).

Many thanks.

I suggest using the room sim and simply playing around a bit - different room sizes, different speaker height, closer or more far from the walls and so on. I think this will tell you more than a thousand words here.

 

[Yorkshire Mouth]

I suggest using the room sim and simply playing around a bit - different room sizes, different speaker height, closer or more far from the walls and so on. I think this will tell you more than a thousand words here.

I’m not asking about my room.

Please read the questions again.

Many thanks.

 

[Yorkshire Mouth]

To be clear.

As an example, the answer to question 1 must be either:

A - The room always makes speakers go lower
B - The room usually makes the speaker go lower, but sometimes not, or not be very much
C - It’s 50:50 whether the room will make your speaker go lower or not
D - Sometimes LF will go up, sometimes it’ll stay the same, sometimes LF will actually be reduced

For question two the answer is either:

A - The bigger the room, all else being equal, you get lower frequency response
B - The smaller the room, all else being equal, you get lower frequency response
C - Room size is not a factor

For question 3 it’s either:
A - Bass traps will also stop, or lessen the room making the speaker sound liwer
B - Bass traps remove unwanted effects, but your room will still make your speaker go lower

And for 4 it’s either:
A - If the room makes one speaker go lower, it’ll make all speakers go lower
B - Some speaker designs will mean a room won’t make them go lower

Or some variation not too dissimilar to one of those.

 

[DJBonoBobo]

I’m not asking about my room.

Please read the questions again.

Many thanks.

Please read my answer again, just play around with different parameters, then you can find answers to at least 3.5 of your 4 questions.

 

[DJBonoBobo]

To be clear.

As an example, the answer to question 1 must be either:

A - The room always makes speakers go lower
B - The room usually makes the speaker go lower, but sometimes not, or not be very much
C - It’s 50:50 whether the room will make your speaker go lower or not
D - Sometimes LF will go up, sometimes it’ll stay the same, sometimes LF will actually be reduced

Or some variation not too dissimilar to one of those.

Yes, obviously I know all rooms are different, I think that’s pretty clear from my first post.

No, the room effects the FR depending on it's geometry of the room and the placement of speakers and LP. Some frequencies are going up, some go down. Your options A-D are too simple. If you used the room sim, you would see for yourself.

 

[Yorkshire Mouth]

Please read my answer again, just play around with different parameters, then you can find answers to at least 3.5 of your 4 questions.

Your answers tell me to measure my room.

My questions are not about my room.

Therefore your answers don’t answer my questions.

I’m not being rude, it’s just how the English language works.

 

[sarumbear]

Another school day for me.

I've just been watching one of Erin's typically great videos, this one being on the JBL 4329P.

In the video he says the speaker measures on the spinorama as going down to 30hz, but when you put in your room it'll go down to 20hz, dependent on the room.

Now I've heard this sort of thing before. Obviously, before anyone points it out, I know all rooms will be different, but I have a few questions.

1 - Whilst the amount may differ, will pretty much all rooms make a speaker go lower?

Yes

2 - Is room size the the dominant factor? As a general rule of thumb, will a larger room take it down lower and a smaller room less so, or the other way around?

Yes. It depends on the room geometry and construction.

3 - If you have your room treated (bass traps in corners, etc.), will this negate the effect, or does this deal with a completely different issue?

It may, it may not.

4 - Is the effect dependent in any way on the speaker, or is this purely how the room operates? In other words, if you put two different speakers, both going down to 30hz in the same room (at different times), and the room takes one of them down to 20hz, will the other speaker also go down to 20hz, or will the room always affect LF in the same way; is it completely room dependent?

Every room has a gain but some speakers use different propagation and the gain maybe different between different speakers.

Many thanks.

Happy, now that I answered your quiz instead of reading others who were telling you the same information in an informative way?

 

[Yorkshire Mouth]

No, the room effects the FR depending on it's geometry of the room and the placement of speakers and LP. Some frequencies are going up, some go down. Your options A-D are too simple. If you used the room sim, you would see for yourself.

Your answer implies you agree with option D.

I’ve added options for the other 3 questions.

 

[Yorkshire Mouth]

Yes

Yes. It depends on the room geometry and construction.

It may, it may not.

Every room has a gain but some speakers use different propagation and the gain maybe different between different speakers.

Happy, now that I answered your quiz instead of reading others who were telling you the same information in an informative way?

I’m very happy that you’ve answered my questions, rather than posting reams of writing from which I find it difficult to extrapolated answers which may be implicit, but which require drawing out.

One of the things I love about these forums, Amir’s reviews often take complex issues, but deal with them in a manner which is easily understandable.

I’m very grateful of anyone trying to answer my questions, but it has to be said that some posts appear almost wilfully obtuse.

I deliberately split my post into four clear, deprecate questions. By answering them in this form you’ve helped keep it simple, but without dumbing down.

It really is the easiest thing in the works to start with “On question 3, I’d say…”

Thanks again.

 

[Bjorn]

The room gain is very much dependend on placement of the speakers in the room. It's related to boundary effect. A placement in the corner wil give the highest gain.

Here's an example of a subwoofer measured at free field (no boundary effect), at the floor away from walls, up against a wall and in the corner (black graph).

Porour material wil generally remove room gain, but needs to be very thick to work in the lowest frequencies. Pressure based traps don't effect the gain that much.

 

[abdo123]

This is an intensive analysis on room gain, it's worth a read. It will answer all of your questions.

Analytical Analysis - Room Gain

-Introduction- The term 'room gain' is often seen used when the topic of subwoofers and the low frequency sound reproduction comes up. As I see many explanations that are lacking or incorrect, I thought I might try and clear up the topic once and for all. In all rooms there are so-called...

www.audiosciencereview.com

Generally the size of the room should not matter, it might push the dominant mode down the spectrum giving an illusion of lower extension but you might very well get a null somewhere else in the room on the same frequency so it's not really guaranteed extension.