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Bass response - how deep should my speakers go for a lifelike sound at home?

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  • Bass response - how deep should my speakers go for a lifelike sound at home?

    This is a fork of the discussion of stereo subwoofers, here.
    --------------------------------------------------------

    Ah! That old chestnut again. OK, you probably won't believe me if I say 'not as deep as you've been led to believe' so let's actually make some audio clips and you can hear and judge for yourself.

    First: I'd like you to forget all about the numbers you see in speaker marketing literature. They are all as good as useless. Speaker designers are coerced by marketeers to provide these numbers, and cautioned by the same marketeers that if the competitor's speaker spec says 'bass down to 38Hz' then unless he gives way and writes the spec for his creation as 'bass down to 37Hz' he won't sell any. And believe it or not, the consumer will assume, based on just numbers, that 37Hz must be better than 38Hz. It's all smoke and mirrors.

    The problem is that it is very, very difficult for a designer to say, with certainty, how the bass end of his speaker measures. That's because the bass wavelengths are so long (10mtrs. at 33Hz) when playing bass notes, in effect the speaker is reaching out and touching every object in the room. That means, the poor designer cannot say with certainty where the speaker's contribution stops and the room contribution starts: they are fused together. So he has to use an educated guess but even that guess cannot be how the speaker behaves in your room: at best it is how the speaker will behave in a reflection-free, anechoic chamber. A chamber of free field room is a good way of trying to minimise the room's contribution (but not eliminate it, hence there will still be some uncertainty in the measurements at low frequencies*) and you could ask, what's the relevance of an anechoic bass specification to my listening room. That's a damned good question. I don't have an answer for that.

    My long held belief is that a speaker like the LS3/5a or P3ESR produces a satisfying listening experience for most listeners at a reasonable loudness on wide range material not, logically, because of amazing physics-busting bass extension but because the ear is very good at generating and filling-in missing fundamental notes by interpreting the second and third harmonics of the missing fundamentals. Were this not the case, music reproduced over very modest equipment such as a kitchen radio would be wholly unsatisfying through absence of any sort of bass at all.

    So let's take some examples of a nice, warm orchestral sound that we associate with a fulfilling 'lifelike' listening experience and see how much deep, deep bass there really is. Then we can remove the really deep bass, and see if we miss anything.

    Loading the player ...
    Clip 1: full orchestra, Enigma main theme

    Suppose we apply a brickwall filter set to 120Hz, cutting away everything below that. How does this sound? Noticeably lacking in warmth?

    Loading the player ...
    Clip 2: full orchestra,all bass below 120Hz erased

    OK: lets allow a little more bass through. This time the brickwall filter removes all bass below 90Hz:

    Loading the player ...
    Clip 3: full orchestra, all bass below 90Hz erased

    How about letting everything through above 60Hz?

    Loading the player ...
    Clip 4: full orchestra, all bass below 60Hz erased

    I think that you'll agree that on this particular orchestral track, even though we have completely removed all bass below 60Hz with our 20th order Butterworth filter, it is not easy to tell Clip 1 from Clip 4. The point is that the weight and warmth of those stringed instruments (presumably cellos and double basses) has been substantially retained even with the filter applied which must, logically, mean that their primary contribution to the musical spectrum is above 60Hz - and even above 90Hz. This 60-90Hz region is reproducible on even the tiny P3ESR (at a sensible volume) for a fully lifelike experience.

    Let's reverse the filter and prove the point. This time, rather than erasing all the bass below 60Hz, I'm going to erase all the audio above 60Hz. I won't change the levels, what remains is in the correct proportion to Clip 1. If you play Clip 1 again at a goodly loud volume and then fix that volume, Clip 5 will let you hear how much deep bass there is in Clip 1 here:

    Loading the player ...
    Clip 5: full orchestra, all sound above 60Hz erased

    Can't hear anything? Listen very closely or cheat and turn up the volume! There is a very low level sound there. That tells you how extremely small the sonic contribution below 60Hz is. There is even less contribution below 50Hz, 40Hz or 30Hz. And remember: I have applied a brickwall filter to completely remove unwanted sounds. In the real world, filters - an a loudspeaker is like a filter - have a much more gentle action and would let more deep bass through.

    *The BBC anechoic chamber (just demolished) was far from ideal. The published specification in 1965 after construction indicated that below about 70Hz (from memory) the foam wedges were not perfect absorbers and the frequency response evidenced significant ripples making reliable, accurate measurement impossible. In fact, I hit this problem in 2007 when using the chamber; I concluded that the foam wedges had dried out over their 40+ year life there, and that had made them harder and less porous. I had to find another way to get credible bass measurements.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  • #2
    Rock music and deep bass

    What about rock music - hasn't that got a strong deep bass line?

    Loading the player ...
    Clip 6: Wake up, Rage against the Machine - source file

    Now if we take Clip 6 and apply the same brickwall filter to remove all sound above 60Hz, just as we did in Clip 5 what we're left with is the deep bass. Play Clip 6 and set the volume; then play Clip 6 without altering the volume and what you hear will be in correct proportion to Clip 6.

    Loading the player ...
    Clip 7: all audio above 60Hz erased

    You can probably just about hear a repetitive bass pulse; if you turn up the volume it may be clearer.

    Conclusion so far based on just these two randomly selected audio clips, one full orchestra, one rock music: the deep bass in the rock music track is more audible and it has an obvious beat to it. The deep bass in the orchestral track is quieter and has no obvious beat to it. An early conclusion would be that if you listen mainly to natural music you would not obviously benefit from having speakers with super-extended bottom octave, especially if that had been achieved by a sacrifice in overall neutrality. If you are a rock music fan, there is some information below 60Hz which you may appreciate but it is at a very low level and being of low frequencies with long wavelengths which penetrate walls with ease, would be irritating to neighbours in a way that orchestral music wouldn't.

    It could be argued that as a socially responsible neighbour, your choice of speaker should be governed by the irritation that it causes to others versus the sonic benefit it may bring you. They may hear that boom-boom-boom from <60Hz throbbing through their walls: you probably won't notice its presence or absence.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

    Comment


    • #3
      Subwoofer contributions

      Referring to the above well written article by Mr. Alan Shaw, the designer of the Harbeth Speakers......

      EVERYTHING HE WROTE ABOVE IS OF COURSE TRUE ---BUT ONLY FOR THE SPECIFIC MUSIAL PIECES HE USES FOR HIS "EXAMPLES", like "The Enigma Variations". (The "funny" thing is that you NEED A SUBWOOFER ON YOUR COMPUTER SPEAKERS TO HEAR HIS LAST EXAMPLE! It just so happens that my computer speakrs currently are using a Yamaha YST-MS201 which is comprised of two small regular computer speakers plus one 8 inch (20cm) square built in subwoofer)

      If he chose some other pieces, like my now "beloved" Johann Strauss "Concert Waltzes" Box CD set that I keep mentioning being a 52 CD box set for $2 a CD of HUNDREDS OF MELODIES NOT HEARD FOR OVER 150 YEARS, if he chose one of those pieces he WOULD hear MORE TUNEFUL BASS in those "Johan Strauss II Concert Waltzes" than any of his examples he uses above---he would hear bass that makes the music more beautiful because there is an underlying bass melody that you'd miss otherwise. IT ALL DEPENDS on the piece of music chosen as an example.

      My only objection with what Mr. Shaw so well wrote above is this: it seems to me that he is saying, "Oh heck, you don't REALLY need one of them subwoofers. Forget about 'em and just listen to the speaker without any additional bass because there is so little bass that actually is produced by the CD."....or words to that effect. It seems to me that his comments, though sometimes and partially true, might have the effect to DISCOURAGE the reader from getting a subwoofer.

      I have the capability with my Best Buy $100 Integrated Amp to PLAY JUST THE BASS GOING TO THE SUBWOOFER while TURNING OFF THE OTHER SPEAKERS. And YES...there is sometimes very little bass going to the subwoofer. But at many other times with many other musical pieces, THERE IS SUBSTANTIAL WARM, TUNEFUL BASS being heard from the subwoofer. Can I live without those last few lower notes. Yes! But, if I don't HAVE to live without those few bass notes WHY SHOULD i DENY MYSELF THE PLEASURE OF HEARING THAT WARM BASS SOUND UNDERLYING THE REST OF THE MUSIC???

      Weekend before last I went to a concert of a new piece of music called something like "Benedicte"...forget the name of the composer. It is a choral piece done in a church with one of those gigantic pipe organs on the wall. Several of the sections started with what seemed to me to be the LOWEST NOTES on the pipe organ....LOUD AND DEEP vibrating all through the church venue and all through your body! Or, how about the opening note or notes from "Thus Spake Zarathustra" by Richard Strauss with it's 32Hz beginning notes? You going to give those up if you don't have to?

      So, maybe we have a difference of opinion. Everyone is free, of course, to make their own decision. I've already made my decision to use a subwoofer. My suggestion to like minded blokes and lasses is to get an inexpensive one: Definitive Technology Pro Sub 800 price about $300 on ebay. Works brilliantly!

      John Boland, USA

      Comment


      • #4
        The church organ and its bass

        Let's have a look at the church organ. Here is a recording made by my friend David Lane, the ultimately attentive recording engineer. This was recorded with a pair of B&K 4006 omnidirectional microphones (the same type as I used for my Fairfield Hall piano recording), raised 20 foot with the shortest possible A-D signal path through a Meridian 607 A/D converter. Paisley Abbey info here and here.

        Again, after about 15 seconds and until nearly the end I have applied a brickwall 60Hz filter, so what you hear, in the correct proportion to the overall, is how much deep bass there is in this huge organ.

        Loading the player ...
        Clip 8: Paisley Abbey organ, full frequency bandwidth, then portion where all audio above 60Hz erased.

        If you have a subwoofer and it has a volume control, should you get hooked on deep bass, you may find yourself tempted to turn up the subwoofer. For a bit of a thrill, there is nothing wrong with that but you do need to be aware that the contribution of the sub should be very subtle, barely audible and that by raising the subwoofer output, you have distorted the artists intentions: you have repainted the overall recorded balance to suit yourself. And you may have annoyed the neighbours with the deep throbbing headache-inducing bass notes which will easily penetrate their walls - and bodies.
        Alan A. Shaw
        Designer, owner
        Harbeth Audio UK

        Comment


        • #5
          Star Wars and deep bass

          And here from Star Wars, Episode 1 The Phantom Menace (John Williams) is a track with even more deep bass than the title track (deceptively surprising actually)

          Loading the player ...
          Clip 9: Augie's Great Municipal Band, full frequency bandwidth, then portion where all audio above 60Hz erased.

          Of all the examples here, this one evidences the deepest bass in hertz (approx. -6dB at 20Hz). As my headphones here don't go down so far, it sounds barely audible, but measurably there is significant deep bass. Is there a point in trying to reproduce it? What does it really add to the musical experience? Could reproducing this deep bass in our normal listening room cause the overall sound to swim and become muddy with bass overhang?
          Alan A. Shaw
          Designer, owner
          Harbeth Audio UK

          Comment


          • #6
            Thoughts about deep bass

            What of the subtle ambient clues in the music ABOVE 60Hz, if the frequencies below are removed. Furthermore, the phase issues caused by the filtering (oh alright, the phase issues caused if the filtering is in the analogue domain) MUST be audible (I believe I can identify it, but obviously I haven't subjected myself to controlled conditions for definitive proof). Mind you, the music I listen to, albeit at fairly low levels these days, has plenty of "something" in the 40 to 60Hz region and I have one or two 1970's recorded organ LP's where, if not removed completely in the cutting stage, there's certainly a "presence" in the very low bass that is missing if a high-pass filter is used.

            I haven't put a tone generator into SHL5's, let alone the M40.1's I love so much (heaven forbid!), but these two models do seem to "breathe" more on well produced contemporary bassy works than the M30.1's, let alone the P3ESR's which do their best in the mid bass, and shine everywhere else.........

            I feel that low bass reproduction (to 20 - 30Hz) is necessary, as long as the speaker cones aren't "flapping around" all over the place (amplifier and drive unit damping again) in an uncontrolled manner, the sound becoming sort-of "mechanical" if it's not there. I don't think it's psycho-acoustics either, but I'm obviously not qualified to explore further.

            Comment


            • #7
              Rework examples to see what's below 30Hz?

              Originally posted by DSRANCE View Post
              ...I feel that low bass reproduction (to 20 - 30Hz) is necessary, as long as the speaker cones aren't "flapping around" all over the place (amplifier and drive unit damping again) in an uncontrolled manner, the sound becoming sort-of "mechanical" if it's not there. I don't think it's psycho-acoustics either, but I'm obviously not qualified to explore further.
              Ok, perfectly reasonable question. We can cast some light on that by taking one of the existing examples (or you are welcome to send me you own as a high-bit MP3) and changing the filter parameters. If we cut off everything not above my arbitrary 60Hz but, say, your 30Hz, we can hear just how much energy remains. Or shall I pick, say, the organ work and reprocess it for 30Hz?

              Now clearly David, with all your experience in audio, you have in mind some concept when you talk about 'phase audibility' in the low frequencies. Unfortunately, I just can't figure out what you mean, but I'd like to listen for it. What should I be listening for? How does this mysterious phase issue sound? What are the tell tale sonic clues?

              One thing to keep at the forefront: the ear/brain is extremely adept at filling-in missing fundamentals from harmonics. So, if we have a sharp filter at, say, 70Hz, a note at 55Hz is completely removed. However, if the music contains harmonics of that instrumental note generated by the instrument at 110Hz, 165Hz and 220Hz, amazingly, the ear will 'hear' the fundamental note at 55Hz even though it is entirely absent, and, as the fundamental, has far more power than any of the harmonics added together. This is how we can tolerate music on a plastic transistor radio. There is no bass, but we rapidly adapt to that and hear a foot tapping solid bass that actually isn't there at all. Much depends on the sort of musical diet we have: if it contains much church organ music we can expect somewhat different listener expectations compared with 'normal' western orchestral music.

              I've rooted around and found a good an organ example I think you'll enjoy. From Reference Recordings 30th Anniversary Sampler (RR-908). This is an analogue recording from 1976 (on CD) and we know that analogue bass is unreliable due to recording tape/EQ/head issues. Even so, there is loud, deep bass here:

              Loading the player ...
              Clip 10: Bach Prelude and Fugue in D, BWV532, full frequency bandwidth

              Then we remove everything above 60Hz in the 14-41 secs. portion:

              Loading the player ...
              Clip 11: all sounds above 60Hz erased

              Or, we remove all sounds above 40Hz, leaving only the 20Hz -40Hz band in the 14-41 secs. portion:

              Loading the player ...
              Clip 12: all sounds above 40Hz erased

              Or we remove all sounds above 30Hz, leaving only the 20-30Hz band in the 14-41 secs. portion:

              Loading the player ...
              Clip 13: all sounds above 30Hz erased, leaving only 20-30Hz

              Listening here on normal Sennheiser HD414 headphones, I cannot hear any bass below about 40Hz even on this mighty organ recording. There may be a degree of bass extension beyond which it is not worth paying for and my working hypothesis at this time is that speaker extension to no deeper than about 40Hz is all that is needed to capture even the deepest bass notes. That implies to me that any other listener preference about weight, warmth or ambience as these relate to the lower frequencies of home audio reproduction point to a satisfying sonic experience at a higher bass frequency. For example, not the 20-40Hz region, but by careful optimisation, the 80-120Hz band where by the strangest coincidence (?) the LS3/5a and P3ESR type bass magic works. The attached plot tells you all you need to know.

              >
              Attached Files
              Alan A. Shaw
              Designer, owner
              Harbeth Audio UK

              Comment


              • #8
                Clips

                This is a fascinating exposition, unfortunately the audio clips don't appear to be available in the messages. The clips were playable in the earlier section, before the thread split.

                Comment


                • #9
                  Clips ok?

                  Originally posted by gakyle View Post
                  This is a fascinating exposition, unfortunately the audio clips don't appear to be available in the messages. The clips were playable in the earlier section, before the thread split.
                  Anyone else having problems? They are ok here on Win7 PC and Fujitsu M532 Android tablet. Will check MAC.

                  Comment


                  • #10
                    Ok

                    Originally posted by HUG-1 View Post
                    Anyone else having problems?
                    Fine here on Windows 7 / Firefox

                    Comment


                    • #11
                      Osx ok

                      Work on OSX Mountain Lion too.

                      Comment


                      • #12
                        OK and thanks

                        Fine on Mac with Safari. Great thread. Thanks very much Alan.

                        Comment


                        • #13
                          Ubuntu OK

                          No problems on Ubuntu 12.10 and Firefox.

                          {Moderator's comment: really useful to have Ubuntu/Linux feedback.}

                          Comment


                          • #14
                            Preamps?

                            Originally posted by A.S. View Post
                            Listening here on normal Sennheiser HD414 headphones, I cannot hear any bass below about 40Hz even on this mighty organ recording. There may be a degree of bass extension beyond which it is not worth paying for and my working hypothesis at this time is that speaker extension to no deeper than about 40Hz is all that is needed to capture even the deepest bass notes. That implies to me that any other listener preference about weight, warmth or ambience as these relate to the lower frequencies of home audio reproduction point to a satisfying sonic experience at a higher bass frequency. For example, not the 20-40Hz region, but by careful optimisation, the 80-120Hz band where by the strangest coincidence (?) the LS3/5a and P3ESR type bass magic works. The attached plot tells you all you need to know.

                            >
                            Umm - HD414's don't have any bass to speak of, the balance dominated by a rough and ragged upper midband - see the old HiFi Choice for confirmation, or borrow my old grey coloured set for confirmation..

                            The only objective reason I can give is to get you to listen through a Quad 33 preamp on modern wide range recordings, and then change to a good modern preamp (I'm sure a 77 or 99 would be fine, as well as the later 44 with phonos and proper IEC mains sockets). To me, my 33 in stock form, had a "mechanical" and sort-of "limited" quality to percussive bass notes, which was lacking and to me, more realistically reproduced, on the Croft, AVI and old Crown preamps I have still. If you can tolerate the sparkle at 5kHz or so, do try some Sennheiser HD25's (I have the SP's) to hear a bottom octave or two that seems missing on the 414's...

                            Excuse me please, I'm not that objective in these things and, knowing that the main thrust of this forum is to discuss matters with as much objectivity and proof as possible, I feel slightly backed into a corner I may not be able to escape from I'll listen again with the 25 headphones (once I have an adaptor that works), but gut instinct and experience still tells me that I need to use the most extended and biggest speakers that my room (and wife.....) will allow :lol: The "classic" two cubic foot box with approx 200mm bass unit is just about as big as I can get away with, and I believe these generically go to the mid 40Hz level fairly comfortably if volume levels aren't too high (distortion sets in on older models, especially older BC1's for example, although I'm certain that this is far better on current examples).

                            Comment


                            • #15
                              Originally posted by DSRANCE View Post
                              Umm - HD414's don't have any bass to speak of, the balance dominated by a rough and ragged upper midband - see the old HiFi Choice for confirmation, or borrow my old grey coloured set for confirmation..

                              The only objective reason I can give is to get you to listen through a Quad 33 preamp on modern wide range recordings, and then change to a good modern preamp (I'm sure a 77 or 99 would be fine, as well as the later 44 with phonos and proper IEC mains sockets). To me, my 33 in stock form, had a "mechanical" and sort-of "limited" quality to percussive bass notes, which was lacking and to me, more realistically reproduced, on the Croft, AVI and old Crown preamps I have still. If you can tolerate the sparkle at 5kHz or so, do try some Sennheiser HD25's (I have the SP's) to hear a bottom octave or two that seems missing on the 414's...

                              Excuse me please, I'm not that objective in these things and, knowing that the main thrust of this forum is to discuss matters with as much objectivity and proof as possible, I feel slightly backed into a corner I may not be able to escape from I'll listen again with the 25 headphones (once I have an adaptor that works), but gut instinct and experience still tells me that I need to use the most extended and biggest speakers that my room (and wife.....) will allow :lol: The "classic" two cubic foot box with approx 200mm bass unit is just about as big as I can get away with, and I believe these generically go to the mid 40Hz level fairly comfortably if volume levels aren't too high (distortion sets in on older models, especially older BC1's for example, although I'm certain that this is far better on current examples).
                              David, that is all very entertaining anecdotal stuff but I'm keen for you to tell me about the audibility of 'bass phase', as you have heard something of that ilk (even on non-ideal speakers you say) but I'm none the wiser as to what it is or how to hear it for myself!

                              Suggestion (if you agree). Let's delete the word 'phase' from the audiophile lexicon other than when talking of loudspeakers being out of phase (one pushes, the other pulls air) and we all know what that sounds like and how it came about (incorrect wiring). The problem with the word 'phase' or 'phase shift' or 'phase audibility' (frequently bandied about by audiophiles) is that one seemingly innocuous word expresses one of, perhaps the most, complex subjects in audio physics. Phase is very hard indeed to get ones head around, and I speak as someone who works at the sharp end every day. It really has no place in ordinary audio conversation. It is, quite frankly, meaningless chatter and if you hear someone utter it you should stop them in their tracks and ask them to explain exactly what they do mean.

                              I couldn't care a monkeys about the midrange quality of the 'phones: we're talking bass, octaves away. I've filtered off the midrange so we don't need to worry about reproduction quality. Furthermore, because the comparisons are structured with abutted A-Bs, any old speaker or 'phones will do: something picked up at a car boot sale will be just fine. We're not looking for absolutes, we're exploring comparatives, and your 2 cubic footers will be just perfect for the task. Doubly so if there really is no bass below about 40Hz.

                              I am quite sure that significant, even chronic phase distortion, especially at LF, is most unlikely to be audible. So what have you heard? It couldn't be the far less glamorous amplitude (a.k.a. magnitude, level) differences could it - the most basic of technical parameters of audio equipment?

                              You made a statement David relating somehow to phase in the bass. Your views are taken seriously; we need to get to the core of your concerns here as together we have a duty of care to our readers to factually inform and guide them away from inappropriate or unfulfilling purchase decisions based on unsupported opinions.
                              Alan A. Shaw
                              Designer, owner
                              Harbeth Audio UK

                              Comment

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