Is a flat extension to 20hz or less impossible to achieve in average sized rooms?

[Verdinut]

I have a pair of iems that have a flat response down to 5hz as measured by headroom, 15hz is as audible as 20hz, 10 hz is pretty faint but I can still hear it. 15hz sounds like the low frequency sound of helicopter blades spinning. There's also been some studies showing humans actually can hear and respond to infrasound at higher spl (90-100dB). This particular study found that humans can hear down to about 8hz, a whole octave lower than previously thought. As the study states, the sound was picked up by the ear, not just felt, since the auditory cortex was active during the test.

https://www.sciencedaily.com/releases/2015/07/150710123506.htm

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Eight Hertz is the fundamental frequency of a 64 foot pipe on an organ. Actually, there are several such stops installed on various organs worldwide. As a matter of fact, one of the first operating ones in North America is located in Salt Lake City, most likely at the Mormon Tabernacle Choir Temple.
If someone can ear an 8 Hz tone, it would be interesting to hear from a person from that city or some visitor who had the opportunity to hear and mostly feel those low frequency vibrations. Did you know that the blower that feeds the air into that organ develops something like 375 horsepowers?

 

[yepimonfire]

Eight Hertz is the fundamental frequency of a 64 foot pipe on an organ. Actually, there are several such stops installed on various organs worldwide. As a matter of fact, one of the first operating ones in North America is located in Salt Lake City, most likely at the Mormon Tabernacle Choir Temple.
If someone can ear an 8 Hz tone, it would be interesting to hear from a person from that city or some visitor who had the opportunity to hear and mostly feel those low frequency vibrations. Did you know that the blower that feeds the air into that organ develops something like 375 horse powers?

There's a couple organ recordings with low fundamentals well captured. With the in ear monitors mentioned I most definitely can hear it.

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[yepimonfire]

What are the subs in use?


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Dayton sub 1500.

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[Verdinut]

There's a couple organ recordings with low fundamentals well captured. With the in ear monitors mentioned I most definitely can hear it.

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Greetings!
Would it be possible for you to give me a little list of the most interesting recordings for the low fundamentals and excellent recording engineering as well? It would be appreciated.

However, I doubt that there is one available digital disc that will contain fundamentals below 16.35 Hz, the vibration of a 32 foot pipe.

 

[fuzz092888]

Dayton sub 1500.

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Yea, you're gonna need a bit more than that to get down to single digits.

 

[TLS Guy]

He is hearing woofer flutter and the harmonics of severe distortion.

What drivers are these people using that claim to get to 5 and 8 Hz? To do that you would need a driver with an Fs in that range. You can only drive a driver a few Hz below Fs, and most a little above.

I'm very suspicious these people are NOT generating the fundamentals they think they are.

If you had a driver with an Fs of 16 Hz. If you drove it at 8 Hz, I bet the second harmonic at 16 Hz would dominate the fundamental, so you would hear it, but not 8Hz.

In the OPs case, the driver has an Fs of 17.5 Hz, but in a ported enclosure the lowest F3 is 23 Hz. So if you drive it below about 20 Hz it will decouple from the box, and you hear the helicopter blades described by the OP. You can NOT Eq a ported box.

There is no way the OP can generate the frequencies he thinks. Below 23 Hz his distortion will rise off the clock and it will all be harmonics, and that is what he hears, NOT the fundamental.

Case closed!

 

[Verdinut]

He is hearing woofer flutter and the harmonics of severe distortion.

What drivers are these people using that claim to get to 5 and 8 Hz? To do that you would need a driver with an Fs in that range. You can only drive a driver a few Hz below Fs, and most a little above.

I'm very suspicious these people are NOT generating the fundamentals they think they are.

If you had a driver with an Fs of 16 Hz. If you drove it at 8 Hz, I bet the second harmonic at 16 Hz would dominate the fundamental, so you would hear it, but not 8Hz.

In the OPs case, the driver has an Fs of 17.5 Hz, but in a ported enclosure the lowest F3 is 23 Hz. So if you drive it below about 20 Hz it will decouple from the box, and you hear the helicopter blades described by the OP. You can NOT Eq a ported box.

There is no way the OP can generate the frequencies he thinks. Below 23 Hz his distortion will rise off the clock and it will all be harmonics, and that is what he hears, NOT the fundamental.

Case closed!

I guess that you meant "You cannot EQ a ported box below its tuned frequency" because we can EQ above it, right?

 

[Bucknekked]

I think there is a lot of bunk about room responses and its consequences. As usual the problem is speakers and not most rooms. As usual this problem is mainly speakers and NOT the majority of rooms.

TLS Guy
Your detailed posts continue to inform my smallish, churlish brain. While I like a quick 4 line post as much as the next guy, when you decide to bring out the explanation with the data, I am always going to learn something useful. The "how low can you go discussion" is no different. I've seen your setup and the care and patience it must have taken to get there. If there's low frequency music to be heard, you are capturing it. I'm pretty sure your systems aren't leaving anything worth hearing behind.

I take claims of ability to hear things from folks who have audio has their hobby with more than a grain of salt. I don't dispute the claims because I don't need to. It doesn't affect me, or my audio system, one iota for someone to post they can hear things that aren't there. I would much rather read and see posts however that have substantial backing and data, like yours. If you advance an opinion, odds are pretty good it is substantiated.

There will always be folks who will throw stones at your opinions because you put stuff out there in a very direct fashion. Keep it up. I enjoy reading them.

 

[Verdinut]

TLS Guy
Your detailed posts continue to inform my smallish, churlish brain. While I like a quick 4 line post as much as the next guy, when you decide to bring out the explanation with the data, I am always going to learn something useful. The "how low can you go discussion" is no different. I've seen your setup and the care and patience it must have taken to get there. If there's low frequency music to be heard, you are capturing it. I'm pretty sure your systems aren't leaving anything worth hearing behind.

I take claims of ability to hear things from folks who have audio has their hobby with more than a grain of salt. I don't dispute the claims because I don't need to. It doesn't affect me, or my audio system, one iota for someone to post they can hear things that aren't there. I would much rather read and see posts however that have substantial backing and data, like yours. If you advance an opinion, odds are pretty good it is substantiated.

There will always be folks who will throw stones at your opinions because you put stuff out there in a very direct fashion. Keep it up. I enjoy reading them.

Bucknekked,
I don't agree with the fact that you have a small and churlish brain, but I agree with you as to what you say about TLS Guy who knows quite a bit about loudspeakers.
I know quite a bit too but not as much as him. I have always had that kind of passion to know more about the weakest link in a sound system. I have applied what I have learned throughout the years when I build speaker enclosures.

 

[TLS Guy]

I guess that you meant "You cannot EQ a ported box below its tuned frequency" because we can EQ above it, right?

You are correct.

However the ability to correct all speakers with equalization is very limited. Frequency response errors in drivers, are just symptoms of bigger problems such as retained energy, which do not disappear making the frequency response pretty. The foundation of good speakers is to start with drivers with excellent response within their intended bandwidth of operation, and the wider the better.

 

[KEW]

What drivers are these people using that claim to get to 5 and 8 Hz? To do that you would need a driver with an Fs in that range. You can only drive a driver a few Hz below Fs, and most a little above.

I'm very suspicious these people are NOT generating the fundamentals they think they are.

If you had a driver with an Fs of 16 Hz. If you drove it at 8 Hz, I bet the second harmonic at 16 Hz would dominate the fundamental, so you would hear it, but not 8Hz.

Would this also register falsely using REW?
IOW, does the software generate a 8hz tone (at the start of the sweep) and assuming a 16Hz sound resulted, would REW show it as 8 Hz since the sound was produced when the 8 Hz was being fed into the system?
IOW, does REW only measure SPL regardless of pitch or does it verify the pitch somehow?

 

[yepimonfire]

He is hearing woofer flutter and the harmonics of severe distortion.

What drivers are these people using that claim to get to 5 and 8 Hz? To do that you would need a driver with an Fs in that range. You can only drive a driver a few Hz below Fs, and most a little above.

I'm very suspicious these people are NOT generating the fundamentals they think they are.

If you had a driver with an Fs of 16 Hz. If you drove it at 8 Hz, I bet the second harmonic at 16 Hz would dominate the fundamental, so you would hear it, but not 8Hz.

In the OPs case, the driver has an Fs of 17.5 Hz, but in a ported enclosure the lowest F3 is 23 Hz. So if you drive it below about 20 Hz it will decouple from the box, and you hear the helicopter blades described by the OP. You can NOT Eq a ported box.

There is no way the OP can generate the frequencies he thinks. Below 23 Hz his distortion will rise off the clock and it will all be harmonics, and that is what he hears, NOT the fundamental.

Case closed!

I'm not attempting to get into the teens and I am well aware of how a port works, and I know that it behaves like an out of phase hole in the box instead of a resonator below the tuning frequency that cannot be equalized lower. I was just noticing when I was plugging in room dimensions out of curiosity into rew's room simulator with a theoretical response of 10 hz that unless the room was either sealed or was as long or longer than 1/4 wavelength that the response drops off considerably below 1/4 wavelength of the room regardless of placement. This was confirmed by taking my own measurements. Even with aggressive eq it's difficult to get a decent response below 30hz, if I put the sub outside and take a measurement it's pretty much flat down to 23hz. The two dominate room modes in my listening room are 58hz and 40hz. At best at a 38% distance from both walls 23hz is still buried about 12dB below 50hz without eq.

I seriously doubt any conventional dynamic cone driver could get into single digits or even the low teens without either being extremely large (perhaps 21" or above) or being by being very heavy with a loose suspension and massive amounts of xmax and an enormous cabinet, which would make it extremely inefficient.

The guy at Lenard audio makes a good point when he claims it is impossible for small drivers to properly reproduce large wavelengths and large drivers to reproduce smaller wavelengths and ideally no driver should be used beyond 3 octaves. Of course with a bit of tuning or porting we can make a driver extend below what it would normally in a sealed box. A sub that could make it down to 8hz flat would likely reproduce everything above 60hz poorly.

I think you misunderstood my point. Obviously I am not trying to get a ported sub to play an entire octave below its fs, I was simply stating that 15hz was audible.

The original intent of my post was whether or not it was futile to place a subwoofer with a 20hz or lower f3 into a room that was significantly shorter than 1/4 wavelength of 20hz and expect a -3dB response down to 20hz without substantial eq, as my theoretical room simulations along with my own measurements showed it was not.

 

[shadyJ]

Would this also register falsely using REW?
IOW, does the software generate a 8hz tone (at the start of the sweep) and assuming a 16Hz sound resulted, would REW show it as 8 Hz since the sound was produced when the 8 Hz was being fed into the system?
IOW, does REW only measure SPL regardless of pitch or does it verify the pitch somehow?

That would only be true if you were using the SPL meter function, not the real time analyzer. The RTA tells you what frequencies are being recorded. You can see what your speakers are doing as opposed to what they are supposed to be doing.

 

[yepimonfire]

Would this also register falsely using REW?
IOW, does the software generate a 8hz tone (at the start of the sweep) and assuming a 16Hz sound resulted, would REW show it as 8 Hz since the sound was produced when the 8 Hz was being fed into the system?
IOW, does REW only measure SPL regardless of pitch or does it verify the pitch somehow?

It shows the frequency and spl. It also shows distortion and harmonic distortion. Most of the time at or below a speakers designed f3 harmonic distortion gets worse and worse the lower you go and louder you go, which is one reason people recommend you don't run your speakers full range if you have a sub.

For example, my Klipsch R-15m speakers are rated for 63hz, if I do a full range sweep from 0-20khz at 85dB I end up with a THD of 4.6%. If I do a sweep from 60hz to 20khz at 85dB I get a THD of 1.04%, and it's about 70 dB down. The majority of that harmonic distortion occurs below 50 hz. Of course with more volume both numbers go up. At 105 dB which is peak at reference volume I'd imagine that number for full range would be >20%, since they're ported there would also likely be a massive amount of port noise.

Even speakers that can match the -3dB response of a subwoofer show greater distortion than a sub at low frequencies well within their operating range.

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[its phillip]

People who want single digit response typically buy/build multiple sealed subwoofer systems with large, high-displacement drivers and a lot of amp power. Signal shaping/dsp is used to boost the low end/cut the middle frequencies. This is of course a really basic explanation since I do not have a lot of knowledge regarding the subject.

 

[ATLAudio]

The whole issue of chasing infrasonic frequencies in home audio is a dead end. Practically you only need to go to 25 Hz, and 20 Hz at the very outside. Chasing lower stuff is a pointless endeavor and an unnecessary expense.

I can't possibly disagree more. Mark Seaton has done many listening tests comparing 20hz roll off vs 5-10hz roll off and all of his audiances either prefered or vastly prefered the lower extension.

I can only assume that you've just never experienced ultra low frequency properly set up.

 

[Bucknekked]

I can't possibly disagree more. Mark Seaton has done many listening tests comparing 20hz roll off vs 5-10hz roll off and all of his audiances either prefered or vastly prefered the lower extension.
I can only assume that you've just never experienced ultra low frequency properly set up.

Take great care with suggesting someone with decades of recording and playback experience, not to mention a fabulous system setup beyond the reach of most mortals, doesn't have the experience of low frequency setups.

My question to you would be, in this under 20hz range, what music plays in that range? What musical content is achievable in the under 20hz range? For home theater folks that want to make things go "thud and bang" I will concede there may be content under 20hz in some situations. But for music, what's there?
If I look at what the lowest frequency that can be produced by musical instruments (look here) its inaudible in the range you are discussing.

I have no way to prove or disprove anything in this area of audio. I can use REW and I have measurement tools. But, I don't have sound equipment that even suggests it will play that far down. For me, this is an interesting, but not a practical discussion.

 

[TLS Guy]

I'm not attempting to get into the teens and I am well aware of how a port works, and I know that it behaves like an out of phase hole in the box instead of a resonator below the tuning frequency that cannot be equalized lower. I was just noticing when I was plugging in room dimensions out of curiosity into rew's room simulator with a theoretical response of 10 hz that unless the room was either sealed or was as long or longer than 1/4 wavelength that the response drops off considerably below 1/4 wavelength of the room regardless of placement. This was confirmed by taking my own measurements. Even with aggressive eq it's difficult to get a decent response below 30hz, if I put the sub outside and take a measurement it's pretty much flat down to 23hz. The two dominate room modes in my listening room are 58hz and 40hz. At best at a 38% distance from both walls 23hz is still buried about 12dB below 50hz without eq.

I seriously doubt any conventional dynamic cone driver could get into single digits or even the low teens without either being extremely large (perhaps 21" or above) or being by being very heavy with a loose suspension and massive amounts of xmax and an enormous cabinet, which would make it extremely inefficient.

The guy at Lenard audio makes a good point when he claims it is impossible for small drivers to properly reproduce large wavelengths and large drivers to reproduce smaller wavelengths and ideally no driver should be used beyond 3 octaves. Of course with a bit of tuning or porting we can make a driver extend below what it would normally in a sealed box. A sub that could make it down to 8hz flat would likely reproduce everything above 60hz poorly.

I think you misunderstood my point. Obviously I am not trying to get a ported sub to play an entire octave below its fs, I was simply stating that 15hz was audible.

The original intent of my post was whether or not it was futile to place a subwoofer with a 20hz or lower f3 into a room that was significantly shorter than 1/4 wavelength of 20hz and expect a -3dB response down to 20hz without substantial eq, as my theoretical room simulations along with my own measurements showed it was not.

Actually it used to be thought what you say is true. However it turns out that room size and wavelength is not a limitation. Inability to produce a low note in a small room is without exception due to cancellation by reflections and amenable to suppressing reflections.

 

[shadyJ]

I can't possibly disagree more. Mark Seaton has done many listening tests comparing 20hz roll off vs 5-10hz roll off and all of his audiances either prefered or vastly prefered the lower extension.

I can only assume that you've just never experienced ultra low frequency properly set up.

You are understating the difference between 20 Hz and 10 Hz, which, physically speaking, is quite large; an entire octave, 56 ft vs 112 ft wavelength. The difference between, say 17 Hz and 10 Hz will be a lot more subtle. I have experienced properly set up systems that dig down to the single digits, and the difference between those and the systems I am more familiar with, which extend to the mid teens, is subtle. While there certainly isn't any harm in having a system that can dig to the single digits, it is difficult to justify for any practical reason. It simply is not a big difference. I don't know about Mark's tests, but unless I read about his methodology, I wouldn't take them too seriously. If you want to gauge how much of a difference is commonly experienced between different low frequencies, the thing to do is a blind test, and have the participants fill out a chart that asks something like, "on a scale of 1 to 10, how much more different is this sound experience compared to the last sound?"

 

[ATLAudio]

Take great care with suggesting someone with decades of recording and playback experience, not to mention a fabulous system setup beyond the reach of most mortals, doesn't have the experience of low frequency setups.

My question to you would be, in this under 20hz range, what music plays in that range? What musical content is achievable in the under 20hz range? For home theater folks that want to make things go "thud and bang" I will concede there may be content under 20hz in some situations. But for music, what's there?
If I look at what the lowest frequency that can be produced by musical instruments (look here) its inaudible in the range you are discussing.

I have no way to prove or disprove anything in this area of audio. I can use REW and I have measurement tools. But, I don't have sound equipment that even suggests it will play that far down. For me, this is an interesting, but not a practical discussion.

"My question to you would be, in this under 20hz range, what music plays in that range?"
Very little, if any.

"What musical content is achievable in the under 20hz range?"
Again, very little if any.

"For home theater folks that want to make things go "thud and bang" I will concede there may be content under 20hz in some situations."
There's plenty of content in movies which aren't just thuds and bangs below 20hz. As Seaton and others can attest, there's a very appealing fullness to bass response which you will sense in a proper ultra low frequency set up.

"But for music, what's there?"
Once again, basically ziltch

"I have no way to prove or disprove anything in this area of audio. I can use REW and I have measurement tools. But, I don't have sound equipment that even suggests it will play that far down. For me, this is an interesting, but not a practical discussion."
Only if your position comes from exclusive music listening, however, I can't possibly disagree more on any notion which suggests ultra low bass isn't practical for home theater.