How much bass do I need for my HiFi / Home Cinema System to be perfect? Much more than you think
Ask me the question how much bass do I need for my HiFi or Home Cinema system to sound its best and I would answer you need the same amount for both, the right amount. What determines the right amount is the question I am sure I would hear in reply and ask a group of audiophiles this very question and there would be little agreement. The purpose of this article is to discuss why you need much more bass than you think and what are the implications and problems in achieving this and then the best method to achieving perfect bass.
What is Perfect Bass and why is it critical to the sound of EVERY audio system?
There is a very funny phenomena in audio reproduction because as humans we are naturally poor at hearing bass notes because our ears are small and bass waves are vast in their size, a 30hz wave form is over 37 feet long. Hold that thought until a little later.
Despite an Audiophiles natural inhibition to hear bass notes when you listen to a HiFi or Home cinema system the bass is often the first thing noticed as being good or bad. Too much bass and it dominates, booms and smears and masks the mid range and treble clarity. Not enough bass and the mid range and high frequencies sound more pronounced and the system can sound, forward, analytical, dry and shout at you. You often see audiophiles blaming the speakers for being too “bright” rather than realising there is simply not enough bass to balance, this is a mistake I see being made all the time, hence the reason for writing this article with a video to come soon.
A perfect audible frequency range for humans is often referred to as 20-20, 20hz to 20,000hz, its uncanny that its also the same numbered term for perfect vision. In reality 20hz is harder to hear and is often felt more than heard and you are a lucky audiophile if you can hear up to 20,000hz. Take the entirety of the bass in audio from 0hz to where bass becomes mid range at say 300hz then the range of bass we hear makes up only 300 from 20,000 so only 1.5% of the total audible spectrum. Yet its the most important 1.5% for the reasons just discussed get it wrong and it dominates, smears and distorts the other 98.5%. Get it right and it improves and enhances the other 98.5% of what we hear. Getting bass right is worthy of your time and takes a lot of work because it is not easy.
Ask yourself this question do you know what bass you are getting from your system in your room and how did you measure it?
A “flat” sound does not look flat
For as long as I can remember there has been talk about a “flat sound” as being the ideal and often this is referred to or associated with an audio system having a flat frequency response which appears as logical thinking. Feed a fixed volume signal into an audio system and as you change the frequency of this signal what you hear at the listening position is the exact same volume at each frequency. This means no frequency is being enhanced or reduced by the system, room and the speakers. This is a very simple concept that I think everyone can understand except that is not how it works, in fact it couldn’t be any further from the reality.
I spent years working with acoustic measuring equipment and different equalisers to try and achieve the perfect sound, a measured exactly flat frequency response at my main listening position and I was able to achieve close to it within reason and you might think audio was nirvana was then achieved, nope it sounded terrible. Now you could associate the terrible sound with many different things, dsp and equalisation being bad things, or maybe the speakers or the system were both bad, I don’t think so. I now know the perceived ideal of a flat frequency response just doesn’t sound flat despite how it looks on a graph.
This is not a new concept
in 1933 a study was undertaken by Fletcher and Munson into human hearing and from that the Fletcher and Munson equal loudness curve table was created which plots the perceived human hearing of sound frequencies at specific amplitude or phon (below in red) . This was then re studied later and some adjustments made in what is known as the Equal Loudness Contour (below in blue). As you can very clearly see neither the Fletcher and Munson curves or Equal Loudness Countours look anything like a flat frequency response and yet these crazy looking graphs have been proven to sound “flat” to the human ear, again to clarify each frequency being heard at the same perceived spl for a fixed input volume or phon.
Why is this important?
There is a lot to take from these graphs and studies, leaving the mid range and treble for now which share consensus across both studies and I will return to this in a future article; focusing on the bass and the general shape of the curves you will notice an obvious trend – the lower the frequency the more bass pressure level is required to be perceived as the same spl volume. The difference is even more dramatic at lower volumes; why do audio systems sound lacking at lower volumes, looking at these curves and you can likely see why. The lower the volume exponentially more bass is required to sound equal in volume and how often is this the case in an audiophiles system setup, I would say never.
A more recent study produced a similar result ISO 226:2003
In 2003 the International Organisation for Standardisation (ISO) produced a standardised set of equal loudness curves using research from various countries such as Japan, Germany, Denmark, USA and the UK. These new curves were developed to address some of the potential issues from the work previously undertaken by Fletcher and Munson but it produced a very similar result as you can see.
Its fair to say from studies conducted across different countries in different decades with differing levels of equipment quality and testing methods the results are both credible and something audiophiles should be mindful of and take very seriously because these graphs represent the theoretical ideal frequency curve to mimic in their setups
Why don’t speaker manufacturers design speakers this way?
It would be logical to assume that all speaker manufacturers would use this data and produce a speaker that delivers exactly this frequency curve in a room and I have no doubt it would be a very interesting and balanced speaker to listen to.
In my Dirac Live Calibration work I am measuring speakers all the time and analysing their in room frequency responses. Its very interesting to see how different speaker manufacturers more closely adhere to the equal loudness curves in the mid range and treble regions than others and this inevitably dictates the perceived “house sound” that is attributed to these manufacturers.
Designing a speaker to produce the exact equal loudness bass curve response is fraught with challenges for both the speaker designer and then the in room challenges that are unavoidable. However when you look at these graphs is it any wonder why audiophiles like subwoofers in their systems and how line arrays of subwoofers can really add to the performance of even a very good speaker systems. Is it any wonder that bigger speakers that feature more bass drivers and output more bass often sound more pleasing to listen to compared to bookshelf speakers that can sound strained by comparison due to their limited bass output.
It gets the brain really thinking about how an audio system needs to be designed or setup to sound perfect
Your room is the main problem to achieving perfect bass?
The room you listen in has a huge effect on the sound of the audio system within it, the room acts as an amplifier, but not one you would buy because its far from linear in its amplification. The room will either constructively or destructively make certain frequencies louder or more quiet. This is an unavoidable side effect of listening to an audio system in a room and its happening in every room.
Bass is pressure and bass pressure is measurable, repeatable and predictable, hence the reason I am able to say with conviction your room is a problem to you achieving perfect bass in two main ways frequency and decay. The room dimensions and where you place the speakers in the room and where you listen in the room will totally dictate the bass frequency response of the speaker, it doesn’t matter what speaker it is either the room dictates the bass more than the speaker.
If you compare the frequency response the speaker manufacturer references against for each of their designs with the in room frequency response in the bass region especially they will look like completely different speaker systems. In fact if the manufacturer published a frequency response from the average audiophiles listening room no one would ever buy that speaker. This will seem like harsh words and I don’t intend them to be such, instead I am trying to stress a very important point.
The room that a speaker system will be listened in cannot be predicted by speaker manufacturers because your room is different to mine which is different to the next audiophile and so on, manufacturers of speakers cannot overcome this inherent bass problem dictated by the room. We cannot expect or rely on speaker manufacturers to deliver us the perfect bass that is all on us as the enthusiast to achieve it for ourselves.
I am always mindful of selecting a speaker system with a bass output that will be able to deliver on what I need. Secondly I place the speakers in the room and have the listening position in the spot that will give me the best bass starting point. I wonder how many audiophiles do this as the starting point of their speakers setup?
You cannot measure bass by ear no matter what you think
One of the biggest challenges or obstacles the majority of audiophiles reading this article will face is the acceptance that their ears are no good for measuring bass, no one can train their ears to be able to identify the exact bass frequency and how much in db its either above or below where we needs it to be. The second obstacle is learning a new skill in being able to measure the frequency response of their speakers in their rooms.
This is a basic and fundamental skill that every audiophile should understand and know how to do, I have had countless forum arguments with audiophiles who live by the code “if a difference cannot be measured it cannot be heard” and yet they have never once even measured a speaker in their rooms to know what sound they are actually getting, their ears and what they hear is good enough for them which is a hypocritical mindset, don’t be this audiophile. Despite this quite closed mindset in one regard they are right you need to measure bass using a microphone and computer software if you really want to know whats going on. Luckily the software is free (REW) and the perfect microphone only costs about £100 a miniDSP UMIK 1.
You don’t need to be an acoustics expert to use REW but there is a learning curve that accompanies this path of enlightenment and it is enlightenment to visually see the sound you are getting in your room from your audio system Its also horrifying to see how bad it inevitably is, especially for bass. If you are lucky you will see peaks and nulls in your bass response of under 20db in variance and shortly followed is the realisation a second ago I was just listening to this system thinking it sounded great.
Seeing the sound of your system in your room represented graphically is the first step to understanding how to make it better – until then you are just guessing with no assurance of success.
A second acoustical bass problem to think about
There are two main bass problems caused by rooms and they are intrinsically linked together, the first problem is frequency and how this wildly varies due to the second problem decay. At the start of the article I mentioned a 30hz wavelength as being 37 feet long so what happens in a room that is not 37 feet long. I will leave the technical explanation to acousticians but as audiophiles this is something to be very aware of.
I am sure the majority of the readers of this article will be aware of bass room modes which are caused by the build up of pressure within the room. As bass pressure builds in the room it will change the spl of bass frequencies heard by the listener as the bass notes “ring” for a significant period of time, much longer than at mid range and high frequencies generally. Think of bass boom or one note bass which is fundamentally changing the tone of bass instruments, the bottom of vocals and worse it sounds awful.
Ringing is another word for lingering and if you measure the time a bass notes takes to decay (reduce in spl) to below audible it may take as long as a second. Its only a second how can that be damaging to an audio systems clarity, well think of how complex music can be and then think of how much sound there is every second in music. If the bass is running on a 1 second delay to the rest you will notice it instantly so 1 second is a very significant period of time for an audio systems presentation. Also think of a time when you have heard boomy bass from a system and how invasive that is to you enjoying the music.
To simplify this and generalise the deeper in frequency of the bass notes that are created by the speaker system the larger they are in wavelength (physical size)and the more likely they are to “ring” in the room due on the dimensions of the room.
This is extremely important to consider because going back to the ISO Equal loudness curves we know the deeper the bass the significant amount more of it we need to sound equal in loudness BUT the more bass we feed into our rooms the bass decay and frequency problems are worsened which makes the audible result worse rather than better.
In the words of Dick Dastardly “Drat and Double Drat” perfect bass cannot be achieved in 99% of small rooms (under 37*37*37 feet in size) and this is why speaker manufacturers don’t design speakers to have the perfect equal loudness curve bass response because the room will completely change it anyway
BUT I want perfect bass I dont want to settle for less than perfect bass
Bass needs to be delivered in a linear fashion – the Third Challenge
As I have discussed achieving perfect bass is a real challenge not only do you need a lot of it, much more than you thought, your room needs to be able to dissipate the sheer amount of large wavelength bass to stop it building up and causing problems.
In my experience bass also needs to be delivered in a linear fashion to the listener if you look at the shape of the curves for all the equal loudness studies the overall shape of each curve on the graphs are pretty much identical and therefore to get perfect bass our audio systems needs to deliver the bass to the listening position in the same controlled linear way.
Really this is the third challenge to achieving perfect bass, we need the right amount at the right frequency being delivered in a linear fashion without the room causing the problem of allowing bass to build up and ring with all three challenges being intrinsically linked.
What can I do about it?
The first step to achieving perfect bass is accepting two things, I need much more bass than I thought I did and I will take the necessary steps in order to get it. The first step might seem a little counter intuitive but the speaker placement needs to reflect how much bass is needed in order for it to be perfect, the majority of speakers will need to use the room as an amplifier to boost the lower frequencies they produce to the levels required. An alternative approach is to install subwoofers which is an obvious option but comes with its own setup challenges and caveats that I will look to cover in the future.
We know that if we put the speakers in the best spot in the room to give us the right amount of bass needed as per the equal loudness curve (aka a lot) the other 2 problems of decay and frequency variance will likely be worsened and yes this is inevitable and is why it seems a counter intuitive to place speakers to do this, but its an essential first to start with as we need the bass present to manage it down in spl, you cannot easily manage bass spl up to where you need it to be.
Bass Management is essential there is no getting around it for the majority of audiophiles
There will be a lucky few audiophiles that have a room that doesn’t require bass management although I would guess that you have a better chance of winning the National Lottery than this being the case for you. Every room has bass problems, different rooms have different problems but they are still problems and we want perfection.
There are two ways to manage bass in a room one is physical and one is electronic and from my experience to achieve a perfect sound you likely will need the best of both.
Speak to any Acoustician about room acoustic treatment and their first advice is concentrate on treating bass, which is very different advice given by certain professionals in the HiFi Industry; PS Audio Paul McGowan springs to mind. He often recommends diffusion based treatment as the best to install and I will cover why I feel its not a simple as that due to the very limited range diffusion works in. Acousticians advice to instal treatment to fix bass problems first is based on they know its the most problematic area of room acoustics and the most difficult to fix. Bass waves are huge and speakers produce huge amounts of bass with hundreds of watts of amplification power being available in devices the size of smart phones. Feeding large amounts of bass into rooms is not difficult in 2020 but managing that bass is the real problem.
GIK Acoustics make a fantastic range of acoustic products that are all Lab tested to deliver the results they promise, they will also give you free acoustics advice on treatment strategies. They also offer a 3D visualising system on their website so you can better select the right visual finishes to complement your room.
From my experience room acoustic treatment is very effective at reducing bass decay problems in rooms, and yes it helps with the frequency response variance problem some too but often the speaker room interaction is too dominating and further action is required to achieve the tight linear bass response we need for perfect bass.
Despite what the graphs might show you for frequency adding good acoustic treatment to your room your ears will hear a much tighter more focused bass which allows for a much tighter and more focused mid range and treble to be presented. If you improve the frequency response variation then important things like tone are improved. If you lower the reverb time of the room it has less of its own sonic signature which means you are hearing more of the original recording and less of your room being added to it. Room reverb is a very interesting area of psychoacoustics I will revisit in the future.
Good DSP is the second answer
The analogue only HiFi enthusiast who thinks “the signal must stay pure it must stay analogue” makes perfect sense to me, deliver this signal into a speaker that is setup with a perfect frequency response in a perfect room and that will be audio nirvana I have no doubt. But as this article has discussed this lofty goal is totally unreasonable to achieve for 99% of audiophiles.
In fact this whole logic becomes counter intuitive and in my experience audiophiles that adopt this end up listening to the same music that sounds “good” on their systems and they then blame the music that doesn’t sound good on the recording quality. This statement is a little sweeping but after reading countless “the recording quality is poor” comments on forums it can make one a little jaded.
I think a much more proactive approach is to face the problem head on, accept that bass problems exist and that they are problems that NEED to be addressed to achieve perfect bass and therefore perfect sound and if that means digital and dsp then that has to be the way to go.
A solution like Dirac Live is exactly what we need as audiophiles to take control of the bass in our systems to manage it to be delivered in the linear fashion we know its needs to be. Clever DSP like Dirac Live while it is outstanding it does not replace the importance of room acoustic treatment for reasons of decay and reverb (RT60 Times) although it does help.
With the bass management implementation of both good acoustic room treatments and good DSP we can achieve as close to perfect bass one could ever hope to achieve and it wont be guess work, it will all be measured confirming the bass is at last “PERFECT”
The final straw – has the master of this track been made with the same attention to detail as I have with setting up my system
This is a very interesting and apt question to raise because even after all the efforts have been made some songs and or movies still don’t have perfect bass.
In my experience the better the audio system is setup to deliver “perfect bass” the easier it is to appreciate the work done to create music or movies sound tracks with more of them being very good rather than bad which is a positive going forward, but inevitably some still will have less than perfect bass.
For the ultimate in reassurance if you know you have things setup correct, you have followed the right path and you know you have “perfect bass” from your system in your room any bass you hear that is not perfect you can then blame the recording or the sound work of the engineer, you have earned the right to make that accusation. However if you are an audiophile who still hasn’t done what’s necessary to earn this right, I say look in the mirror and point the finger at that that person before any accusations are made towards the recording or mastering engineer.
I hope this article has come across in the right way and I hope it helps sparks a little fire in some of the audiophiles that will read it. I appreciate what I am discussing in this article is not a quick fix situation, it requires a lot of work and some of it will be difficult to achieve in normal domestic situations, and its difficult to achieve anyway but I do honestly believe the path to achieving a perfect system starts by achieving perfect bass.