Here’s a simple test

December 3, 2022
 by Paul McGowan

Whenever the subject of filling in missing low frequencies comes up I am often asked how do you know what’s missing?

Certainly one can perform a series of measurements at the listening seat. But how relevant are those measurements given they will never be flat?

Part of the problem with frequency response graphs is reading and interpreting them. Have a look.


The frequency response appears to be all over the map (it is). With a bit of experience, you learn to see the general averaging trend and ignore the dips and bumps (most programs offer various levels of smoothing or averaging). Still, how do you accurately relate what you see to what you will eventually hear in your room and on the musical choices you play?

Perhaps even more important is the question, is flat what you want for an in-room response?

In my experience, you want the lowest frequencies, say from 35Hz and down to be up a few dB relative to the average.

In fact, the easiest way to figure all this out is not with charts and graphs but by simply listening.

One of my favorite tracks is Boz Scaggs Thanks to you. As the keyboardist hits the lowest note is it the same level as the others? Or, is it missing altogether? Or, another oldie but goody is from the album Hourglass by James Taylor. The track is Gaia. About 2/3 the way into the track there’s a musical bridge where the bass and drums should rattle the room at the same level as the song itself. On most systems, this is less than exhilarating. Wimpy, in fact.

At the end of the proverbial day what you’re looking for is an even in room low-frequency response that is nearly always available only to those with an added subwoofer.

Have a listen and see where you stand.

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25 comments on “Here’s a simple test”

  1. Very helpful to have some music recommendations with which to try.

    Just reading this morning an article on BBC news about the composer Sir James MacMillan who, over ten years ago and in complete secrecy, was asked to compose some music for the Queen’s funeral. To quote from the article:

    When news of the Queen’s death broke, he realised his music, written more than a decade earlier, could now be used.

    “I got the score out and looked at it again to remind myself of what the music would sound like,” Sir James said. “It’s always different when you play it on the piano – but that’s what composing is, you’ve got to imagine sounds that are not in the room with you.”

    Interesting, we could do that as a possible cheaper way to upgrade your hi-fi. 😉

  2. I’ll give them a listen – thanks for the hints.

    Oldies but goodies for reference. There’s a phrase you don’t hear a lot in the new recording world, but is well accepted in the playback world.

    No surprise that the room measurement should be used as a guide not an absolute. 🙂

  3. I doubt these simple measurements can show only the direct sound from the loudspeakers and ignore the reflected sound! Thus what is it use for? And what about the differences between near-field and far-field listening? As yesterday’s post concerning room modes and subwoofers clearly showed things are a bit more complicated!

  4. I have found exactly what Paul described to be true. I prefer the “35hz & lower” part of the signal adjusted up a few DB. I notice it doesn’t just help with low content, but also seems to round out the whole sonic picture.

  5. Yes, listening also here is always needed to verify measurement results.

    And filling in missing frequencies is always the easiest task and most think, that’s what’s the simple task with a sub. Just to find the position for the sub in the room where it fills that missing dip and this seems easy for the above graph. But even there, if one fills in everything below the 37Hz point, it will get obvious that the 24Hz peak will get annoying or there will still be a dip between 24Hz and 37Hz, not yet considered that the sub, wherever placed will have own dips and bumps up to 37Hz.

    That’s why one in my experience will never have a quite flat response under a frequency like those 37Hz, if it’s not a parametric EQ’able sub. Without having that, one will have filled mainly a certain frequency peak below that, which will ad something that was missed…but there will still be missing frequencies around that upcoming peak.

    Regarding demo tracks for leveling in the amount of sub bass that’s optimal, this is certainly depending on the own still present bumps in FR in the room. Paul’s description is only valid for his current environment and will fill in a different part of low frequencies depending on his individual new situation, but he’ll think he always filled in what’s acoustically needed. But at the end it’s all we can do. We don’t know how that music sounded live, nor how the engineer mixed it on whatever monitoring equipment. So what sounds most satisfying to us in our room might be completely wrong compared to what was live…just because the engineer didn’t take care for those low frequencies.

    At the end we choose some tracks that we identified as helpful to tune in the bass of our average music in whatever room. A mainly classical listener will choose very different tracks with very different results than a mainly electronic music listener.

    However I also experienced Paul’s Bozz Scaggs example is helpful and good to verify bass response, but a bit too limited…it needs more, different tracks of which everyone of us will have several, not just one…and the Scaggs album just offers this one track.

    Two albums which by each one’s various tracks alone (suited to level in a setup), cover a lot of frequencies at the low end, for me are Bob Belden’s Tapestry and Mono Cinelu’s self titled album containing the tracks Namonale and Soon I will be home (just to make it identifiable more easily). Two great albums musically, too, by the way.

    If you have a full range setup and get all tracks of both albums sound perfectly bass filled and not annoyingly resonating somewhere, you’re set. The measurements will then show a flat enough graph, too, I’d say. But anyway, I do it the other way around…positioning and EQ’ing the sub so I get the flattest FR, then use those albums to set the final EQ and level adjustments of the sub (and in my case main speaker bass)

    1. For bass testing, I have a couple favorites. The first is the drum in Gaia mentioned by Paul above. The second is several tracks from Harry Manx’s live album “Road Ragas”. The low level is nicely mixed in a musical way. Sounds flat on systems that are off in the lower end.

      1. Your last sentence is exactly why single tracks or albums are often not helpful (if they’re off). Then you get a flat response but with the wrong tracks.

        My personal current choice ended up in this measurement (slightly smoothed as discussed in this forum topic). I can’t do anything about the dip around 43 Hz, as everything else including the main speaker position would get worse. It’s the best compromise for me and I consider especially the quite flat range below that as more important.

        I agree with Paul, that it often sounds right when the very low end is slightly leveled up, but for my current musical profile, this works really well.

  6. Hi Paul
    We are on the same page.

    I have used the 2 tracks mentioned for assessment of my systems for years.

    If these sound good I am happy. After the “drop of a hat”, Gaia 4 minutes 11 seconds in, hits this perfect spot.

    For a more general assessment Gretchen Peters Trio is my go to album with Barry Walsh on Piano and Dave Francis on Bass just sounds wonderful.

    1. “Dropped my pack”… and it is awesome.

      The first CD I popped into the deck when I had an all ADS tri-amped system installed in a Mazda RX7.
      All EQ,d with spectrum analyzer and a little Nakamichi 8” driver in a home-made box For a subwoofer.
      It’s all in boxes in the garage now.

  7. It just dawned on me that’s there is always this talk of complete sonic accuracy and that talk continuously changes depending on the recording, the equipment and its placement, or revolves around “the room”. The room measurement and room correction software are the latest panacea. This is all in the quest of flat response in the frequency / sound level realm.

    It seems what many audiophiles want is a standardized room and sound. (How boring?) They can go to Paul’s place and things don’t sound any different there then at Jazznut’s place or any other place.

    I don’t think I subscribe to that concept. Every concert hall is different, every jazz club is different, every performance is different. Hell, every studio and its personnel are different. About the only thing that doesn’t change every time we listen is the actual recording we happen to choose. (Even that can change depending on format)

    Why not embrace the room sound? Change it as you hear fit for you and for your choice of recording at that moment. How you implement the change is a matter of personal choice and personal subjective taste.

    Often these discussions sound like a game of “one up man ship” …. With what is perceived as total accuracy as the crutch to hold things up.

    I prefer total musical enjoyment over total accuracy. Others can’t.

    1. Gene at Audioholics would definitely take exception to your last sentence (more likely your entire comment.) and anyone else who just want to “listen” for the pleasure that music brings. Don’t think it’s in his lexicon. Another fool that happens to have a huge following of The Living Dead.

      1. 😀

        Maybe a better concept is defining the most accurate “audiophile” 1st. 😉
        They should all have exactly the same personality and all be in lock step agreement.

        I don’t begrudge anyone who is in pursuit of better sound for them. I like the audio discussions the banter, the different ideas and the concepts.

  8. This is an area where I think electronic music might have an advantage over acoustical instruments (as far as testing goes).

    You can listen to a bass player run down the neck to see if the notes are of even volume…. but are they, or did he just play that note softer or louder than the rest? Hard to say.

    Or, we could just listen to test tones. Not as much fun, but probably more accurate.

  9. Good day to you Paul, hope you are doing well. Thank you for the base references .Two questions , does the upcoming Octave Records effort celebrating ‘the bass’ contain either of those and when will we be able to acquire a copy? Inquiring minds wish to know.

  10. A comment and a question

    Comment: I prefer my bass tight and have in punch you in the chest as apposed to bass that rolls across the floor and rattles things. Thus I am not sure if I have the records you mentioned, but I will try to check them out.

    What is the Art of Hi-Fi series going to be about and how does it compare the the Audiophile’s Guide series?

    1. The Art of HiFi series is just musical examples of a specific HiFi quality and there is no associated book. If you’re interested in bass we’ve hand selected some great recordings that have deep bass. Something you can just pull off the shelf and be certain the music has deep bass.

  11. Carly Simon’s “Letters Never Sent” , ‘Halfway Round The World’…
    A timpani on the rhythm section is captured well, yet does not muddy anything.

    Causes my carpet to wriggle.

    It sure rattled my wife’s diaphragm.

    It’s a great Carly album overall.

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