Analytical Analysis - Room Gain

[René - Acculution.com]

This is my setup, with all three subs in one corner of the room aimed roughly at the corner diagonally across.
View attachment 299022
View attachment 299023

I haven't measured the nearfield response yet, so I can't simulate the overall frequency response in the room, but the cardioid part works splendid.
It's a 3 woofer setup because initially multi-sub optimizer was intended to be used. It'd be easier to simulate with only 2 woofers of course.

Nice. Do you have a picture of the setup? Looks cool.

 

[KLang1]

Oh it's just three closed boxes stacked on each other with the lowest one turned to the back. All Dayton RSS315HF-4 in 34L.

 

[spalmgre]

Erin is discussing this topic as well or is it another variant of the same idea being "Room gain"?

He is calculating the f0 for where the room gain starts from the dimensions of the room. Here in this thread here, it has been presented that the room gain is a product of pressurizing the room. I hope I have understood this right.

I have tried to measure the room gain and compare this to Erin's method with WinISD. I seem to find the gain in the measurements of my 15" 2235 speaker but it correlates with the WinISD filtered curve only if I use 50Hz as f0 (where the gain starts).

I have read the first post in this thread many times but I can not find an answer (maybe I just don't understand the text) to where from does the gain start.


Erin's video -->Free Bass! Subwoofer Room/Cabin Gain: What it is and how to model it with WinISD

 

[bert stoltenborg]

Erin is discussing this topic as well or is it another variant of the same idea being "Room gain"?

He is calculating the f0 for where the room gain starts from the dimensions of the room. Here in this thread here, it has been presented that the room gain is a product of pressurizing the room. I hope I have understood this right.

I have tried to measure the room gain and compare this to Erin's method with WinISD. I seem to find the gain in the measurements of my 15" 2235 speaker but it correlates with the WinISD filtered curve only if I use 50Hz as f0 (where the gain starts).

I have read the first post in this thread many times but I can not find an answer (maybe I just don't understand the text) to where from does the gain start.


Erin's video -->Free Bass! Subwoofer Room/Cabin Gain: What it is and how to model it with WinISD

What are the room dimensions?

 

[René - Acculution.com]

Erin is discussing this topic as well or is it another variant of the same idea being "Room gain"?

He is calculating the f0 for where the room gain starts from the dimensions of the room. Here in this thread here, it has been presented that the room gain is a product of pressurizing the room. I hope I have understood this right.

I have tried to measure the room gain and compare this to Erin's method with WinISD. I seem to find the gain in the measurements of my 15" 2235 speaker but it correlates with the WinISD filtered curve only if I use 50Hz as f0 (where the gain starts).

I have read the first post in this thread many times but I can not find an answer (maybe I just don't understand the text) to where from does the gain start.


Erin's video -->Free Bass! Subwoofer Room/Cabin Gain: What it is and how to model it with WinISD

You’ve got it. What I am discussing is the behaviour down towards the zeroth mode but the longest length in the room will determine the first mode as Erin says. So calculate that and know that well below it, the behaviour is very much governed by your type of speak and how leaky your room is.

 

[bert stoltenborg]

You’ve got it. What I am discussing is the behaviour down towards the zeroth mode but the longest length in the room will determine the first mode as Erin says. So calculate that and know that well below it, the behaviour is very much governed by your type of speak and how leaky your room is.

There is afaik a thread here where people show their measured room response. If they add the speakers and room dimensions and eventually the room boundary construction you could check if Earl Geddes is right in what he said about room gain.

 

[René - Acculution.com]

There is afaik a thread here where people show their measured room response. If they add the speakers and room dimensions and eventually the room boundary construction you could check if Earl Geddes is right in what he said about room gain.

What did he say?

 

[bert stoltenborg]

What did he say?

He said he never met a situation where room gain mattered as all environments are way to lossy to make it substantial. There was a discussion on the Studiotitsforum where Brian Ravnaas (of green glue fame) postulated a theory on car acoustics. and Philip de Haan (of AlconsAudio fame) did some measurements on speakers in a car showing, as far as I remember, there was room gain. I see if I can retrieve this discussion and the measurements. I have used them not extremely long ago but memory serves me bad .

 

[René - Acculution.com]

He said he never met a situation where room gain mattered as all environments are way to lossy to make it substantial. There was a discussion on the Studiotitsforum where Brian Ravnaas (of green glue fame) postulated a theory on car acoustics. and Philip de Haan (of AlconsAudio fame) did some measurements on speakers in a car showing, as far as I remember, there was room gain. I see if I can retrieve this discussion and the measurements. I have used them not extremely long ago but memory serves me bad .

I showed in a recent audioXpress article how the theoretical room gain matched well with measurements done by Erik Wiederholtz of Perlisten in his own room. But sure, a lot of factors come in to play in general.

 

[bert stoltenborg]

He said he never met a situation where room gain mattered as all environments are way to lossy to make it substantial. There was a discussion on the Studiotitsforum where Brian Ravnaas (of green glue fame) postulated a theory on car acoustics. and Philip de Haan (of AlconsAudio fame) did some measurements on speakers in a car showing, as far as I remember, there was room gain. I see if I can retrieve this discussion and the measurements. I have used them not extremely long ago but memory serves me bad .

The discussion was on how you can get low frequencies in a car that is mainly made of 0.7 mm metal. All the sound will flow through the hull as there is only a few dB attenuation in the low freqs.
Philip measured a 4 x 10" ampeg speakerbox in a ground plane situation in a factory hall, then put it in a Mercedes Station car and measured again, showed in pic 1.
He also measured with vents closed and open, and with car windows closed and open, pic 2.
It is a kind of vented bandpass system, of course.

 

[bert stoltenborg]

I showed in a recent audioXpress article how the theoretical room gain matched well with measurements done by Erik Wiederholtz of Perlisten in his own room. But sure, a lot of factors come in to play in general.

Cool where do I find it?

 

[René - Acculution.com]

Cool where do I find it?

I might be able to post the picture showing this once I am back from vacation. Need to ask audioXpress.

 

[NTK]

Cool where do I find it?

I think it is available only to subscribers or you'll have to purchase the issue.

Audio Amplifiers and Exciting Innovations in audioXpress July 2023

audioXpress July 2023 provides an updated market and technology overview of Audio Amplifiers, includes the review of the Hypex Nilai500DIY 500W Power Amplifier Kits, a visit to Dutch company Grimm Audio, and an interview with Rémi Guastavino to discuss the new GRAS EQset measurement microphone...

audioxpress.com

 

[René - Acculution.com]

I think it is available only to subscribers or you'll have to purchase the issue.

Audio Amplifiers and Exciting Innovations in audioXpress July 2023

audioXpress July 2023 provides an updated market and technology overview of Audio Amplifiers, includes the review of the Hypex Nilai500DIY 500W Power Amplifier Kits, a visit to Dutch company Grimm Audio, and an interview with Rémi Guastavino to discuss the new GRAS EQset measurement microphone...

audioxpress.com

There isn’t much more there than I already put in this post, except for the measurements.

 

[bert stoltenborg]

There isn’t much more there than I already put in this post, except for the measurements.

Measurements is, what I understood from this forum, what it is all about.

 

[spalmgre]

You’ve got it. What I am discussing is the behaviour down towards the zeroth mode but the longest length in the room will determine the first mode as Erin says. So calculate that and know that well below it, the behaviour is very much governed by your type of speak and how leaky your room is.

My rooms longest dimension is 5 m. So that is way down from the 50Hz that seams ( see my measurement post #83) to be the gain start frequency. So then we do have a third gain variable after the Hz0 (Rene) and the Hz1 (Erin) described modes. This would then be the boundary gain witch in my case prowobly is the floor interaction with the 15in base driver.
Any thoughts about if this is right?

 

[René - Acculution.com]

My rooms longest dimension is 5 m. So that is way down from the 50Hz that seams ( see my measurement post #83) to be the gain start frequency. So then we do have a third gain variable after the Hz0 (Rene) and the Hz1 (Erin) described modes. This would then be the boundary gain witch in my case prowobly is the floor interaction with the 15in base driver.
Any thoughts about if this is

Way below f1, the effect of the f0 mode will be very determining for the resulting sound field, so if your measurements deviate a lot from the anechoic response of the loudspeaker then you have very little leakage in your room. That is probably the most I can say without having to look at the measurements on my phone screen

 

[audiofooled]

My rooms longest dimension is 5 m. So that is way down from the 50Hz that seams ( see my measurement post #83) to be the gain start frequency. So then we do have a third gain variable after the Hz0 (Rene) and the Hz1 (Erin) described modes. This would then be the boundary gain witch in my case prowobly is the floor interaction with the 15in base driver.
Any thoughts about if this is right?

Too see correlation with your measurements, first go to https://amcoustics.com/tools/amroc , enter your room dimensions and find the frequencies of the first two modes (1-0-0) and (0-1-0), also third (2-0-0), and fourth one (0-0-1).

These are the axial modes determined by your room dimensions, are two dimensional and particles in the close vicinity of these boundaries cannot move, resulting in lowest particle velocity but highest pressure. These modes are hard to miss, but it's excitation can be manipulated by position of your source(s) and your listening position, resulting in different peaks and nulls.

If your room is not leaky, then yes, f0 mode would give you flat response down to DC, but for a prediction of a normal, leaky room, try the WinISD Linkwitz filter where you enter your second (0-1-0) mode as f0, and your first (1-0-0) mode as fp, where the room gain should start to roll off. You may see that WinISD will still predict a lot of room gain governed by the peak at the second mode, with a slope shaped around the first mode. For my room, this prediction works even with all windows and doors open.

 

[tomtoo]

Could someone gift me some brain?

 

[clemenules]

I might be able to post the picture showing this once I am back from vacation. Need to ask audioXpress.

I think it is available only to subscribers or you'll have to purchase the issue.

Audio Amplifiers and Exciting Innovations in audioXpress July 2023

audioXpress July 2023 provides an updated market and technology overview of Audio Amplifiers, includes the review of the Hypex Nilai500DIY 500W Power Amplifier Kits, a visit to Dutch company Grimm Audio, and an interview with Rémi Guastavino to discuss the new GRAS EQset measurement microphone...

audioxpress.com

I've bought the issue and read the article.

Not sure what to make of the measurements in the article. The measured room gain is just so-so. Then it goes on to say that the measurement room has a large opening to an adjacent room. So..... what to make of this? Room gain is supposed to describe spl gain below a certain frequency in a sealed room. We are presented with measurements in a non-sealed room, that only shows a couple of db gain below 33 Hz. What does this tell us about room gain? I am confused.

How much room gain for a less leaky room? Is it 12 db per octave below the first mode? 9? 7? Does it level out from a certain frequency? (assuming a closed sub with 12db rollof). Is the room gain in db related to the rollof of a sealed sub or is it strictly room dependent? How leaky is a room with minor (like few mm) opening to an attic and 2 cm opening under a door? The only thing I am learning from the articles' experiment is that indeed a ported sub has 0 db room gain.

Questions questions. I am debating with myself buying a sealed or ported subwoofer for my small listening / home cinema room of 3x3x2.4 m (approx), closed, apart from said door with 2cm space under it.

Is it worth it to get a sealed sub for this room? How much room gain could I expect? Or should I get a ported sub with many db's more 'native' output but almost zero output below the port's tuning freq?