[medium jim]

Many say that they can live without subs, but most full range speakers typically go down to 40hz.  That begs the question, when do you need to go below 40 hz?

Thanks,
Jim

[Devil Doc]

Lovers of organ music might appreciate bass response below 40Hz.

Doc

[mjosef]

Depends on the type of music you listen to...piano, tuba, organ,bass etc. has notes or harmonics below 40Hz... personally I can live with 3dB down @ 30Hz.


http://www.independentrecording.net/irn/resources/freqchart/main_display.htm

[Russell Dawkins]

According to old (but probably still valid) Bell Labs research, any time you go above 10kHz.


Their golden rule covering this was that for playback to sound natural the upper and lower -3dB (or minus anything dB) frequencies, when multiplied together should equal 400,000.


By that reasoning, if you are 6 dB down at 40Hz, you should be 6dB down at 10kHz

This is how telephones can sound reasonably natural with a bandwidth from 200 Hz to 2,000 Hz - the product is 400,000!

[JohnR]

Russell, I would be wary of extrapolating a rule of thumb for telephone bandwidth to hifi. With regard to the question "when do you need to go below 40 hz?" it needs to be remembered that no speaker stops producing output abruptly at 40 Hz (or any other frequency). And the curves vary by speaker - a sealed speaker with a -3dB point of 40 Hz will produce more output at 20 Hz than a ported speaker with a -3dB point of 40 Hz, as an obvious example. There's also potential drawback of pushing your in-room response as low as you can, while often 20 Hz is stated to be necessary for true hi-fi, you run the risk of getting very poor decay times at such low frequencies. I found an in-room -3dB of 30 Hz (in my room, my system, etc) preferable to 15 Hz.

[Edit: added a very important "at 20 Hz" qualifier...]

[JohnR]

With regard to the fundamental frequency of instruments, that frequency does not by itself determine the lowest spectral content in music. Many instruments have a strong transient nature. When (for example) you modulate a sinewave by a transient, the spectrum is the sinewave frequency convolved with the spectrum of the transient envelope. In non-technical terms, I suppose you could say that the transient "spreads out" or "smears" the spectrum from the nice single frequency that the sinewave has. The result is spectral content that extends considerably lower in frequency than the fundamental of a note.

You can do spectral analysis on segments of your music files with Audacity, it's an interesting thing to try. bear in mind that you may get some "artifacts" so don't be too literal with interpreting the results, but it's worth doing nonetheless.

[roscoeiii]

And then there is electronic music, which can plumb the depths of bass.

[Russell Dawkins]

Russell, I would be wary of extrapolating a rule of thumb for telephone bandwidth to hifi. With regard to the question "when do you need to go below 40 hz?" it needs to be remembered that no speaker stops producing output abruptly at 40 Hz (or any other frequency). And the curves vary by speaker - a sealed speaker with a -3dB point of 40 Hz will produce more output at 20 Hz than a ported speaker with a -3dB point of 40 Hz, as an obvious example. There's also potential drawback of pushing your in-room response as low as you can, while often 20 Hz is stated to be necessary for true hi-fi, you run the risk of getting very poor decay times at such low frequencies. I found an in-room -3dB of 30 Hz (in my room, my system, etc) preferable to 15 Hz.

[Edit: added a very important "at 20 Hz" qualifier...]

I wasn't extrapolating this from a rule of thumb for telephone engineering - Bell was applying what they had identified as  a fundamental principle of natural reproduction (and has since been forgotten by the masses, apparently) to the challenge of making the very narrow bandwidth available in telephony sound reasonably natural.

Serious audiophiles of the time up until around 1985, in England particularly, were employing devices in their replay chain by which they could widen or narrow "the window" to suit the quality of the recording. These were one-knob EQs which, when adjusted, allowed the adjustment in a manner such that the two frequencies (hi pass and low pass) always produced 400,000 as a product.

I have experimentally made a filter with my Metric Halo processor which does this and it works surprisingly well. I choose the frequency of 632 Hz and vary the bandwidth from .01 octaves to 2.5 octaves. Sure enough, the fundamental tonality is preserved to a surprising extent until an amazingly narrow passband.

I think it is assumed the steepness of the slopes, high and low, match, as well as the general shape - which would suggest this is probably most easily accomplished with sealed LF boxes.

Of course, ideally, the decay times are similar at all frequencies - that's why bass absorption is so important for creating a good listening environment in the home, although in my experience it is almost always inadequately done.

Anyway, I bring this whole thing up to stimulate thought, not as a definitive decree.

I have experimentally made a filter with my Metric Halo processor which does this and it works surprisingly well. I choose the frequency of 632 Hz and vary the bandwidth from .01 octaves to 2.5 octaves.

[JLM]

My single driver friends usually camp in the high efficiency/low amp output corner and so struggle with power hungry bass output to the point that most are deluded into forgetting, even denying what exists "down there".  Interestingly I attended an audiofest years ago in that camp where a huge pair a powered subs (about 48 cu. ft with 2-15 inch woofers each) were available.  Yet they kept getting turned down, further and further.

I agree with Russell on the need to balance highs with lows.

And thanks mjosef for that chart (best I've seen).   

[Photon46]

Whether one "needs" bass below 40hz. depends on how resolving one's system is and what type of music you listen too as well. If you listen to orchestral music and have heard much of it live, you know that all sorts of subtle low frequency ambient sounds contribute to the sense of music being created in a large space. Tympanis and bass viols couple with the orchestra flooring and create massive amounts of low frequency sound energy that is so cool to hear on a good system. I notice on well recorded cds that you hear the recording studio or hall "breath" for lack of a better word before the music starts and that sort of aural information is below 40 hz. as well. Plus, large dynamic drivers (or big horns) that reach real LOW just move air in a wave launch that better captures the sense of ensemble dynamics.

[rollo]

For my personal system subs are required. Meaning after adding a pair and then a third behind me there is no turning back. A fuller more complete presentation. The feeling of being there. The added weight and impact to the sound creates for me a closer look into the live performance.
    It took some time to dial in the balance below 40 HZ is a requirement now for us. As an aside we have been auditioning some new speaker lines which at best go to 30HZ in room. They sound VG to us as is. However every time we engaged the subs our enjoyment increased. A fuller more complete sound. Every demo so far for some club members the same outcome was reached.
   I would recco dual subs and if ya can try a third one behind you.



charles
   

[dB Cooper]

Lowest fundamental on a bass guitar tuned to A440 is about 43Hz IIRC. Obviously organ music goes much lower. Characteristics of the room and speaker placement come into play as well. No shortage of variables.

[srb]

Lowest fundamental on a bass guitar tuned to A440 is about 43Hz IIRC.

While not as popular as 4-string basses, there are a number of 5-string basses, both upright and electric, being used in many genres of music that have the extra lower bottom string tuned to B0/~31Hz.

But the question is how often are the lowest note or two on this or other low-reaching instruments actually played?  Probably not enough to make it any kind of system need or requirement.

Steve

[Russell Dawkins]

I look at the region of 50-15Hz as one of of the "wild frontiers" in audio, and not just because it is often messed up or missing in home replay, but because it is not well handled at the mixing and mastering stages of a recording, either.

Only one type of microphone covers this range well - the omni, which senses air pressure, not particle velocity as do the others. Omnis are not always used.

The audiophile favorite "Jazz at the Pawnshop" was recorded with a pair of omnis, I believe, and that is a large part of the reason the club ambiance is so well portrayed - and the image is so non-specific. There is still no free lunch, and spaced omnis do not do imaging well.

[cheap-Jack]

Hi.

.Obviously organ music goes much lower.
Characteristics of the room and speaker placement come into play as well. No shortage of variables.

But the question is how often are the lowest note or two on this or other low-reaching instruments actually played?  Probably not enough to make it any kind of system need or requirement.

Record shows pipe organs can actuallly deliver 8Hz subsonic bass notes with 64-ft ranks & 16.4Hz with a 16-ft pipe.

Here is what I experience in my audio den down my house basement whenever I want to shake the place all over - playing the last soundtrack of the flip side of the LP: "Andrew Davis plays the organ at Roy Thomson Hall" (BTW, RTH is in Toronto, Canada).

With my 100W 10" sub on, fed direct from my DIYed super-upgraded Dynaco PAS-2 tube phono-preamp driving my super-upgraded ST-70 (triode-strapped to deliver only about 15Wx2) & KEF 2-way bookshelvers, I can hear clean & very substantial bass note (sounded to my ears like 20Hz or so) across the room.

I swear I was virtually STUNNED by the clean subsonic pipe-organ notes from  the LP I played the very first time after I picked it up from my favourite thrift store (for 75cents only!!)

Who said LP can't deliver sub subsonic notes??

c-J

[konut]

Who said LP can't deliver sub subsonic notes??

c-J

Nobody. Just watch the woofer move when a warped record is on the platter.

[James Romeyn]

I'd prefer 45 Hz cutoff with great power and bass modes fully controlled vs. 20 Hz cutoff with great power and no modal control.

Any day.

I'd even probably settle for 55 Hz.  Bass with modal problems is awful.   

[cheap-Jack]

Nobody. Just watch the woofer move when a warped record is on the platter.

Don't worry. When you can SEE the tonearm riding the warps, it'd be probably only a few Hz sub subsonic. Not many amp or loudspeaker can reproduce them. Our ears surely can't detect it.

c-J

[cheap-Jack]

Hi.

I would recco dual subs and if ya can try a third one behind you.
 

Just out of curiosity.

You want 3 subs to bring an outdoor rock concert back home or what?
You want the massy LF volume to drive away yr neighbours or you want to enjoy some clean unboomy sub subsonics?

c-J

[*Scotty*]

cheap-jack, read this thread and the included links for the reasons behind the three subs in rollo's system. This thread and the links introduce the Controlled Acoustic Bass System (CABS). http://www.audiocircle.com/index.php?topic=106838.msg1099888#new
Scotty