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Subwoofer low frequency extension.

A800

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Subwoofer low frequency extension:
What's a useful spec for the usable frequency range?

-3dB?
-6dB?
-10db?
 

Siwel

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-10dB has been something of a standard boundary for measurement purposes. I say "something" because I don't know if an actual standard has been specifically agreed upon as the exact point at which LF is no longer considered to be "spec-able" output. I can tell you that an LF signal that measures at -6 from nominal level is still plenty audible. Lesser output (-10 dB) is still audibly valuable but at the point that a speaker is 10dB down from nominal output it is well along the way to adios amigos.
 
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A800

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According to the equal loudness contours, a ~10dB difference <40Hz sounds like a 20dB difference, so I would say that’s too much. I usually see -6dB, which seems good as speakers use a 6dB deviation window (+/-3dB) as well.

Good point.
Thanks.
 

North_Sky

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Quality subwoofers: minus 2/3 dB.
 

Kvalsvoll

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Subwoofer low frequency extension:
What's a useful spec for the usable frequency range?

-3dB?
-6dB?
-10db?

None of those numbers are useful. The only meaningful specification for a subwoofer/bass-system is spl output capacity in the frequency range it is meant to reproduce. Frequency response in itself does not matter.

I have repeatedly explained why and how and what, even wrote an article on this specific subject, I do believe I have posted links to that article also on this forum. For someone with a technical background, this is not very difficult to understand.
 

North_Sky

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+/-3dB rating on this baby ...
https://www.paradigm.com/en/sealed/seismic-110

SPL output capability, not many manufacturers mention that spec.
...And for each frequency covering the low three octaves.
Best is to measure them in our own rooms.

* Kvalsvoll, you have a link please to your article on this specific subject?
There are ... total number of posts, and ... total number of threads here @ ASR.
If we were to read them all it would take ... number of months (perhaps years).
 
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A800

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None of those numbers are useful. The only meaningful specification for a subwoofer/bass-system is spl output capacity in the frequency range it is meant to reproduce. Frequency response in itself does not matter.

I have repeatedly explained why and how and what, even wrote an article on this specific subject, I do believe I have posted links to that article also on this forum. For someone with a technical background, this is not very difficult to understand.

Can you link me?
 

Kvalsvoll

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Can you link me?

I sincerely hope my previous reply was not taken as criticism for asking the question, nor discussing the matter. Any question must be welcomed and replied to in due respect, it is just that sometimes, well, you get the idea..

I found the article: https://www.kvalsvoll.com/blog/2018/02/25/specification-for-subwoofers/ (It is on my web-site, but it does not promote any of my products or tech solutions, as far as I can remember.)

And now I am going to read it myself. Because this was written 2 years ago.
 

Kvalsvoll

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+/-3dB rating on this baby ...
https://www.paradigm.com/en/sealed/seismic-110

SPL output capability, not many manufacturers mention that spec.
...And for each frequency covering the low three octaves.
Best is to measure them in our own rooms.

* Kvalsvoll, you have a link please to your article on this specific subject?
There are ... total number of posts, and ... total number of threads here @ ASR.
If we were to read them all it would take ... number of months (perhaps years).

I would have a hard time finding those posts myself.
 
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A800

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I sincerely hope my previous reply was not taken as criticism for asking the question, nor discussing the matter. Any question must be welcomed and replied to in due respect, it is just that sometimes, well, you get the idea..

I found the article: https://www.kvalsvoll.com/blog/2018/02/25/specification-for-subwoofers/ (It is on my web-site, but it does not promote any of my products or tech solutions, as far as I can remember.)

And now I am going to read it myself. Because this was written 2 years ago.

Thank you!
 

Siwel

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None of those numbers are useful. The only meaningful specification for a subwoofer/bass-system is spl output capacity in the frequency range it is meant to reproduce. Frequency response in itself does not matter.

I have repeatedly explained why and how and what, even wrote an article on this specific subject, I do believe I have posted links to that article also on this forum. For someone with a technical background, this is not very difficult to understand.

I think the original question is 'at what frequency does the output of a subwoofer no longer contribute meaningful information?' At least that's how I read it. As I said, there is no standard for this that I am aware of. I don't interpret the question as asking what makes a good subwoofer, just a query regarding the point at which any output is no longer meaningful.
 
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North_Sky

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I would have a hard time finding those posts myself.

No problemo, and I totally understand what you mentioned; it is often misunderstanding the order of the words we put together that leads to wrongful criticism.
We all have a voice and the utmost respect for life. It's all together who we put this world upright. ... the farmer, the medical nurse, the doctor, the pope, the stockbroker, the prime minister, the presidential team, the scientist, the Hollywood star (actor), the football player, the golfer, the film director, the photographer, the subwoofer's designer, the movie watcher, the music listener.
 

MZKM

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None of those numbers are useful. The only meaningful specification for a subwoofer/bass-system is spl output capacity in the frequency range it is meant to reproduce. Frequency response in itself does not matter.

I have repeatedly explained why and how and what, even wrote an article on this specific subject, I do believe I have posted links to that article also on this forum. For someone with a technical background, this is not very difficult to understand.
+/-dB window doesn’t matter much, but how deep the response digs does matter, and at what SPL.

Amir has asked how he should measure subs, as a 2.83V Spinorama is not very useful. My vote was for CEA-2010 at minimum, with the addition of group delay (which should give the same info as a waterfall and spectrogram) being highly requested. Data-bass remains the best website for subwoofer measurements, and I know Amir is not willing to put in the work to be as extensive. Another issue is Amir being able to do a CEA-2010 test without disturbing his family, but more importantly, not pissing off neighbors.
 
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A800

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I think the original question is 'at what frequency does the output of a subwoofer no longer contribute meaningful information?' At least that's how I read it. As I said, there is no standard for this that I am aware of. I don't interpret the question as asking what makes a good subwoofer, just a query regarding the point at which any output is no longer meaningful.

This.
 

Kvalsvoll

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I think the original question is 'at what frequency does the output of a subwoofer no longer contribute meaningful information?' At least that's how I read it. As I said, there is no standard for this that I am aware of. I don't interpret the question as asking what makes a good subwoofer, just a query regarding the point at which any output is no longer meaningful.

And this relates to capacity. How much capacity is needed, then depends on what we see as meaningful spl, at least it should be audible.

At the listening position, audible means approximately:
90dB at 10Hz
80dB at 20Hz
70dB at 30Hz

Tactile feel - to feel the sound physically on your body - starts at around 80-90dB, but is very dependent on mechanical properties of the floor at very low frequencies. This also depends on the properites of the sound field - the intensity and particle velocity.

Those detection levels will be higher if sound at higher frequencies are present, the higher frequencies will mask the ultra-low frequencies.

For realistic spl levels, it makes sense to dimension for around 110-120dB. Then you will be able to play quite loud, and have a nice physical impact.

A subwoofer is measured at a given distance, in specified surroundings, often 2pi/ground-plane. How loud it is in-room at the listening position depends on placement of subwoofer and listener, room size, and room loss. A small sealed room with rigid walls will be louder that a large, open space. Fortunately, room gain increases with lower frequency, in a sealed room. The bad side is that intensity and particle velocity decreases.

So we see that a subwoofer needs more output at lower frequencies to be usable. Since output from all subwoofers decreases as frequency goes down, we see that is will be the capacity at the lowest frequencies that sets the capacity limit for the system. So to get usable extension well below 20hz in a large room, the subwoofers will need to be quite large.

But for most music, those capacity requirements can be relaxed quite a bit, because music rarely has very loud levels of ultra-low bass, typically max spl will be limited by capacity in the 30hz-and-above range.
 

Kvalsvoll

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+/-dB window doesn’t matter much, but how deep the response digs does matter, and at what SPL.

Amir has asked how he should measure subs, as a 2.83V Spinorama is not very useful. My vote was for CEA-2010 at minimum, with the addition of group delay (which should give the same info as a waterfall and spectrogram) being highly requested. Data-bass remains the best website for subwoofer measurements, and I know Amir is not willing to put in the work to be as extensive. Another issue is Amir being able to do a CEA-2010 test without disturbing his family, but more importantly, not pissing off neighbors.

A simpler test may still be useful, as long as it shows capacity, perhaps distortion. A simple compression sweep set could do the job.

It also makes sense to test smaller subwoofers. Because that is what many actually buys, and not everyone needs demolition-spl.
 

MZKM

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A simpler test may still be useful, as long as it shows capacity, perhaps distortion. A simple compression sweep set could do the job.

It also makes sense to test smaller subwoofers. Because that is what many actually buys, and not everyone needs demolition-spl.
The Dayton sub-1200 and BIC F12 are the most popular decent subs. Polk makes the most popular budget subs.

Klippel has a CEA-2010 test I believe (they have documentation for the test).

Group delay will show us which subwoofers are “loose” and “fast”.
 
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