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RoHo

How much bass extension is really necessary?

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We all know the audio spectrum is from 20Hz-20kHz.  I think it is a common understanding that for true, high fidelity reproduction the speakers/room should be capable of reproducing down to around 20-30Hz, though few can.  Most people would accept the compromise of less bass extension against the gains in speaker size and cost.    But we accept this is a compromise as we are trading off that "full-range" ideal.   

So I was thinking about the music I listen to - rock, folk, blues, country.  The lowest fundamental tone is the 42Hz from the bass guitar.  Maybe a kick-drum thud will be around that also.  But what else?  Dunno.  So would a speaker that is, say, 3 dB down at 40Hz be indistinguishable with my music to a "full range" speaker?

Sure, if you listen to large-scale classical, pipe organ or electronic music there is significant content in the lowest octave.  But for the large number of us who don't, is there anything to be gained by having a speaker that is flat to 25Hz?

Rod

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Posted (edited)

Some, certainly desperately want  you to believe, and trust them, that the audio spectrum is limited. However we absolutely need audio equipment to have audio spectrum capable of reproducing the actual ability of musical instruments as shown here to 102.4khz :    http://www.cco.caltech.edu/~boyk/spectra/spectra.htm

http://recordinghacks.com/articles/the-world-beyond-20khz/

 

As for the other end, its exciting  to have ability at the very lowest octaves, as there are many pieces of music containing these frequencies. 

Edited by stereo coffee

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Posted (edited)
1 hour ago, RoHo said:

We all know the audio spectrum is from 20Hz-20kHz.  I think it is a common understanding that for true, high fidelity reproduction the speakers/room should be capable of reproducing down to around 20-30Hz, though few can.  Most people would accept the compromise of less bass extension against the gains in speaker size and cost.    But we accept this is a compromise as we are trading off that "full-range" ideal.   

So I was thinking about the music I listen to - rock, folk, blues, country.  The lowest fundamental tone is the 42Hz from the bass guitar.  Maybe a kick-drum thud will be around that also.  But what else?  Dunno.  So would a speaker that is, say, 3 dB down at 40Hz be indistinguishable with my music to a "full range" speaker?

Sure, if you listen to large-scale classical, pipe organ or electronic music there is significant content in the lowest octave.  But for the large number of us who don't, is there anything to be gained by having a speaker that is flat to 25Hz?

Most of the problem is nothing to do with the lower extension limits per se. It is to do with how much maximal sustained energy can be produced at those frequencies. For example, if you have a small bookshelf speaker with a lower limit extension of 42Hz, there's a good chance that it can't generate more than a few watts at most before the cone excursion becomes non-linear and the output compressed, thus making it impossible for the fundamental to actually be loud enough at anything above quiet background music, and when played at quiet background music levels we can't hear those low frequencies at all.

 

Take for instance this graph below, this is a 16" closed subwoofer with a 1500W built in amplifier. Note that its maximum sound pressure level is about 113dB, and it only just is able to maintain that at 42Hz, but any lower frequencies and the maximum amplitude drops off dramatically no matter how much power you pour into it. Notice how the top 3 lines all come together below this frequency. Now extrapolate this concept to a 5" woofer in a bookshelf speaker and you'll see that it's probably only able to maintain its maximum sound pressure levels no lower than 80-100Hz. Furthermore, when you are pushing the limits of excursion in the low frequencies, it will be adversely affecting all the other frequencies that woofer is reproducing.

 

image

Edited by Ittaku

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I have always found in my room that increasing low frequency extension also has an inverse impact with a great sense of 'air' that one would normally associate with high frequency extension?

 

For example my current speaker system is Voxativ field coil 9.87 with a full range field coil driver running fairly flat in room from 40Hz – 18kHz with an active Ripol bass system that is fairly flat down to 20Hz in room.  My previous system was an active 3-way with RAAL ribbon flat out to 35kHz but Accuton bass units not extending much below 40Hz.

 

The added bass in my Voxativ speakers seem to actually compensate in room performance for what objectively is less high frequency extension?!

 

I would suggest that bass extension is VERY important as its impact is very broad across the rest of the spectrum.

 

A good friend uses active version of the gigantic Rockport Technologies Arrakis2 which has phenomenal bass on its own but to increase extension and control below 20Hz, he added 3 x active REL Gibraltar subs per channel to augment the Arrakis's already formidable bass.  The in room experience of this combination is truly staggering for how it seemed to make everything sound so effortless and also open up the high frequencies as well as extending the bass response considerably.

 

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33 minutes ago, Ittaku said:

Take for instance this graph below, this is a 16" closed subwoofer with a 1500W built in amplifier.

 

image

Being a 16 incher I presume this is the largest SVS sealed subwoofer.
I'm thinking that would go quite well with typical room gain.

https://www.svsound.com/blogs/glossary/room-gain

 

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Just now, Satanica said:

Being a 16 incher I presume this is the largest SVS sealed subwoofer.
I'm thinking that would go quite well with typical room gain.

https://www.svsound.com/blogs/glossary/room-gain

Yep exactly that one. Since it's my sub, I know its details very well.

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35 minutes ago, Ittaku said:

Most of the problem is nothing to do with the lower extension limits per se. It is to do with how much maximal energy can be produced at those frequencies.

I love it when someone intelligent can put into words what I have been hearing for years now. What measurement is indicative of a speaker that will have bass impact and weight? Is that even measurable?

 

Bass extension doesn't tell you the full story. Bass impact and extension at volume is more important to me then a speaker that has 25-30hz of extension. For me when I listen at a reasonable level, say peaks of 110db+ from my listening position, how convincing and realistic is well recorded percussion. Does a kick drum or a tom have considerable weight and move a significant amount of air. You can keep your 25hz slim line speakers and I'll take less extension for more realism in that frequency range.

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3 minutes ago, kelossus said:

What measurement is indicative of a speaker that will have bass impact and weight? Is that even measurable?

Sure. Instead of doing sweeps at just 1W, you need sweeps at ever increasing power levels such as in that subwoofer sweep above. Alas that seems to ONLY be done on subwoofers even though it is equally important with any regular woofers. Generally speaking, low limit extension should be proportional to woofer size. If you see a small woofer with 20Hz listed as its lower frequency extension, you're being sold a pup. I mean you could get a dome tweeter to reproduce 20Hz, but probably only .01W of it before bottoming out with a maximum volume of about 10dB or something stupid. You could make an argument for putting a high pass electrical filter to your main woofer to minimise its excursion with frequencies it can't reproduce, but in the analog crossover domain, this would amount to an insanely large capacitance so high that it would have very deleterious effects on the quality of the sound. In the digital domain however, anything's possible, and I cross over my main woofers at 35Hz even though they're 13" to derive the benefit of this.

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Posted (edited)
29 minutes ago, Ittaku said:

Sure. Instead of doing sweeps at just 1W, you need sweeps at ever increasing power levels such as in that subwoofer sweep above. Alas that seems to ONLY be done on subwoofers even though it is equally important with any regular woofers. Generally speaking, low limit extension should be proportional to woofer size. If you see a small woofer with 20Hz listed as its lower frequency extension, you're being sold a pup. I mean you could get a dome tweeter to reproduce 20Hz, but probably only .01W of it before bottoming out with a maximum volume of about 10dB or something stupid. You could make an argument for putting a high pass electrical filter to your main woofer to minimise its excursion with frequencies it can't reproduce, but in the analog crossover domain, this would amount to an insanely large capacitance so high that it would have very deleterious effects on the quality of the sound. In the digital domain however, anything's possible, and I cross over my main woofers at 35Hz even though they're 13" to derive the benefit of this.

No not necessarily proportional to speaker size, when Edgar Villchurs acoustic suspension principle is used, outstanding results can be obtained from modest cabinet size. As shown here 35 Hz +-5db   http://0339436.netsolhost.com/WordPress/gs401-speaker/

using 2x 8 inch drivers. 

 

As for tweeters 2khz is about the lowest frequency in a two way, and in a 3 way system, 450- 500 hz for midrange and 5 Khz is the recommended crossover point for its tweeter.  

Edited by stereo coffee

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3 minutes ago, stereo coffee said:

No not necessarily proportional to speaker size, when Edgar Villchurs acoustic suspension principle is used, outstanding results can be obtained from modest cabinet size. As shown here 35 Hz +-5db   http://0339436.netsolhost.com/WordPress/gs401-speaker/

using 2x 8 inch drivers.

2x8 inch is a lot of surface area. There's nothing small about that.

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2 hours ago, RoHo said:

We all know the audio spectrum is from 20Hz-20kHz.  I think it is a common understanding that for true, high fidelity reproduction the speakers/room should be capable of reproducing down to around 20-30Hz, though few can.  Most people would accept the compromise of less bass extension against the gains in speaker size and cost.    But we accept this is a compromise as we are trading off that "full-range" ideal.   

So I was thinking about the music I listen to - rock, folk, blues, country.  The lowest fundamental tone is the 42Hz from the bass guitar.  Maybe a kick-drum thud will be around that also.  But what else?  Dunno.  So would a speaker that is, say, 3 dB down at 40Hz be indistinguishable with my music to a "full range" speaker?

Sure, if you listen to large-scale classical, pipe organ or electronic music there is significant content in the lowest octave.  But for the large number of us who don't, is there anything to be gained by having a speaker that is flat to 25Hz?

Rod

 

Thinking about the bits I highlighted above, I would agree that you don't need it to enjoy that type of music.  In fact in many situations that's all you get - say in most cars for example, but you still enjoy the music. I would not say it is indistinguishable, but you can get a reasonable hifi experience that's enjoyable from smaller speakers. 

 

What that added extension gives you is a bit more realism and excitement - like when a double bass is really thumping. Another example - the other night when I was listening to Bernstein's version of West Side story studio recording (with Jose and Kiri), there was a gunshot near the end, that made me jump in surprise.  It would not have sounded so surprising without that lower frequency pulse I suspect.

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Agreed, but working in tandem too, as one driver moves in the other moves out - they can fit in modest sized cabinets like gales 401, which is heavy at some 56kg each, but domestically fits in well, dare I say reasonably high WAF and very satisfying with audio, as many have found.    

 

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@RoHo

 

Not  exactly sure how low you may want to go. But after having the ability to have a system that’s not only flat to less than 18hz but plays about 3-4db louder down there.

All I can say that it’s wonderful.

You’d be amazed at what content there is down low. Though I have not measured how low I’m getting music/bass , I’m certainly left wanting when I it’s missing on other setups.

But 8x12” long travel linear subs are wonderful with the headroom available.

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Here are my fronts vs my subwoofer. They both go down to 25 - 28hz at audible level. Anything lower, just makes it boomy and rattles things unnecessary.

I would take quality somewhat low bass extension vs meh lower bass extension. 25 -28hz is good enough for almost everything in home theatre.

 

 

Red is uncorrected, Black is target, green is corrected.

1207599839_ScreenShot2020-05-22at1_45_56pm.thumb.png.92b62c94b5c9658a5b3c58d98ad41d56.png344682178_ScreenShot2020-05-22at1_45_47pm.thumb.png.02a4740529dd84d943da706358c12bd7.png923741958_ScreenShot2020-05-22at1_46_05pm.thumb.png.7fb7299a830ed9a224bbf13ad8639323.png

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Posted (edited)

I thought I would open up a rock song with Audacity and am surprised to find as much frequency roll off from about 50Hz down.

 

1.jpg

2.jpg

 

Also on a separate note, much has been mentioned about the "house curve".
For a while I've held the opinion that much of the "house curve" already ends up in the typical mix\master as I think this shows.

Edited by Satanica

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Here's a bit of a guide to which instruments might utilise the extra footroom.

Bass drum doesn't 'kick' in until about 50Hz!

Action movie LF effects would be down there with the Pipe organ I expect.

main_chart.jpg

Legend.jpg

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Low frequencies brings out any weaknesses of a system as it is especially dependant on the room and the acoustic treatment. A 20hz wave is 17m~ making rooms very problematic to treat without giving up functionality/space/aesthetics. Even just the dimensions of a room would make it very poor for bass, like when room modes are stacked together making it impossible to treat. Untreated/ringing bass just sounds horrible.

 

We are much more sensitive to intensity differences among the bass, due to how equal-loudness curve works. A 5dB change is perceived as twice as loud compared to 10dB required in the higher frequencies. Bass and sub bass provides spacial cues on the location of the recording and gives a particular toe-tapping quality to the music. 

 

The placement of the subwoofer drastically affects the resulting performance. They are big, heavy units and quite cumbersome to integrate properly. If you have floor standers, it'll mean you'll be very limited in their placement. At the end its all worth it as it allows you to enjoy Tchaikovsky - 1812 Overture in all its glory. Subs are worth the effort. 

 

BqE9Wvrl.png

 

9tdBouKl.png

 

2 slides are from: Floyd Toole - Sound reproduction – art and science/opinions and facts

 

QjZPJLd.png

 

Pre-EQ.

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There's hearing the bass, and there's feeling the bass.

If you can't move a lot of air you miss the visceral aspects of the bass sounds.

Like feeling the thump in your chest, and having your pants rattled.

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Awesome information, people.

To sum up, with my music a 40 Hz low limit may be sufficient but only if my system can maintain that 40Hz at high volumes.

I have a dsp controlled sub so I might try increasing the low frequency cut off to 35-40 Hz and see if I hear a difference.

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13 hours ago, RoHo said:

Awesome information, people.

To sum up, with my music a 40 Hz low limit may be sufficient but only if my system can maintain that 40Hz at high volumes.

I have a dsp controlled sub so I might try increasing the low frequency cut off to 35-40 Hz and see if I hear a difference.

Try 80Hz if you are actively cutting off your main speakers. If there's no cut off to your main speakers it'll have to be a compromise point. If you have a single sub only, and are actively measuring the output, try to make it about 5dB louder than the main speakers during a frequency response sweep.

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On 22/05/2020 at 12:04 PM, RoHo said:

The lowest fundamental tone is the 42Hz from the bass guitar.  Maybe a kick-drum thud will be around that also.  But what else?

There are many things which have a lot lower frequncy content than the "fundamental" tone.

 

Short bursts of sound contain both very low and very high frequency content .... think of the "percussive" type sounds you can make hitting a string on a bass guitar.   Lots lower than 42Hz.

 

That being said, very low frequency tones themselves are not very audible.

 

On 22/05/2020 at 12:04 PM, RoHo said:

So would a speaker that is, say, 3 dB down at 40Hz be indistinguishable with my music to a "full range" speaker?

Here is a simulated response of a speaker which is -3dB at 40Hz  .... If it weren't for the low frequency rolloff the phase would be zero at all frequencies.    👀

 

 

 

freq.jpg

phase.jpg

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For example....  50Hz, is ~60 degrees out of phase with 100Hz.

 

Many people have argued that this phase distortion is not audible.... however the way I understand it, is that those arguments are flawed.

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38 minutes ago, davewantsmoore said:

For example....  50Hz, is ~60 degrees out of phase with 100Hz.

 

Many people have argued that this phase distortion is not audible.... however the way I understand it, is that those arguments are flawed.

If the harmonics of an instrument are out of phase with each other, they will not be able to generate the "missing fundamental" that normally occurs with such instruments as the piano. If this is an obvious example which is also easily modelled, then it is probably happening throughout the whole frequency spectrum creating and missing many other frequencies that should or should not be there in the original. Note the lowest fundamental on a piano is 27.5Hz which is extremely low, but there is actually very little natural energy at that frequency from the longest string's vibration, it is usually being created by the phenomenon of the missing fundamental itself. If the harmonics are out of phase with each other, they will not be creating this fundamental.

https://en.wikipedia.org/wiki/Missing_fundamental

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For music, if you have pretty clean extension without a big rolloff down to 30hz, very few would be dissatisfied.

Better than that is for those who want to physically feel the bass, and not just hear it well. Subwoofer territory. Also helps with movies - explosions, etc. 

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It's going to depend on if you are playing vinyl or digital files.

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