How to Not Buy a Subwoofer

(Subtitle: Everything you really should have asked first but didn't because you thought this was going to be simple)

Update January 2021: 

This article is very theoretical.  If you want a practical, step by step take on how and why I avoided using a subwoofer for music please read here.

Introduction

Getting great bass in a room is one of the greatest challenges audiophiles will face. While interacting with a lot of audiophiles it is clear to me that getting great bass is important and, of course, the discussion of a subwoofer often comes up, but lets be honest, no audiophile wants to buy a subwoofer. We don't want to go, pay thousands of dollars and bring home more large boxes to take up more room in our home. The end goal is actually to have great bass and the expense, shipping and placement of a subwoofer is a means to that end.

The point of this article is to introduce several topics related to listening to a system great bass which you should consider, especially if your first and only thought to getting great bass in your room has been to buy a subwoofer. This post will hopefully be a survey of solutions before we get to subwoofers, and we do in fact discuss buying at the end.

HSU Research VTF-15H MK II

At some point we will often consider getting a sub-woofer for one of these reasons:

1. Small speaker with limited bass output 
2. They need more bass despite having a floor standing speaker
3. They've heard that a sub-woofer can really enhance the rest of the audio range

It is true that all of these items will be improved with a well integrated and well performing sub woofer but getting to "well integrated" is be fraught with complications, not to mention the cost and size of a sub.  Truthfully, very few audiophiles with a sub woofer know how to properly set up a sub, and most tire of trying before they are done, with mediocre results.

Don't get me wrong, I love subwoofers but a subwoofer is a glorious addition to a system only when it is properly set up because otherwise it is a nightmare.  In summary:

Without automatic room correction like Dirac or ARC the proper installation of a subwoofer is much more difficult and time consuming than buying it and putting in a corner. It is very easy for the average consumer to get this wrong.

Because subs are complicated it is worthwhile to explore alternatives which I list below and along the way we'll talk about room acoustics which greatly enhance a sub's performance.

Speaker Placement

The closer a speaker is to walls the more bass you'll hear out of them. Usually manufacturers recommend a specific distance away from the rear wall, but remember that side walls count as well. The legendary Allison speakers were designed to be up against the rear wall, and some Snells also rely on very close placement.  Of course, with closer wall placement you also have more early reflections, so your ideal combination might be closer to the wall, and more mid/treble absorption on the floor and walls. 

Tone Controls

There's no such thing as a neutral system when it comes to music playback. Unfortunately the best we can do is try to bowl down the middle of the lane and hope we get a strike more often than not.  Every recording and every mastering engineer was listening to a system very different than yours, and these systems, even if we could buy one exactly to match have changed over time. It is no lie that during the 70's and 80's single driver boom boxes were the standard often recorded to. 

Lets be clear:  A subwoofer IS a tone control.  If you are trying to use a sub to maintain some sort of religious purity, you've already lost, so just accept we are all sinners in the eyes of whatever audiophile purist church is out there and go all in, you will feel better, get to your happy place and spend less money.  There are generally two types of tone controls.

Dial Tone Controls

Schiit Loki

The point is that tone controls that sound good exist and are built into preamps integrateds and receivers or you can add a Schiit Loki which gets great buzz. Not all gear has great sounding tone controls, but even if they add some haze, the benefit of hearing a cymbal sing correctly or adjusting for aging hearing easily outweighs any haze.

Digital Tone Controls

These are now quite common either with room correction, outboard units like miniDSP as well as built into streaming software like Roon. They can be quite effective but require different levels of measurement and configuration. The big benefit here is precision. You can treat a narrow bass mode with a DSP in a way you can't get any other way. Even if you do buy a subwoofer, you should seriously consider an EQ somewhere in your chain, as the lower you go, the more room modes you will activate and having an EQ to clips them greatly enhances the performance.

To give you an idea of how these manual type of DSP equalization processes can work please see my previous post. It uses Roon as an example, but the principles of measurement and parametric filters are the same.

Automatic Room Correction

Automatic room correction can also be called "automatic sub integraters."  In addition to the automatic setup of parametric equalizers they will automatically configure the most important and difficult settings a subwoofer needs to sound good if not excellent.  Brands like the Anthem STR line, Lyngdorf, Dirac, Audyssey etc. are all making room correction mainstream, not to mention home theater processors. The ease of use of room correction systems is not to be underestimated.

One bit of advice: room correction systems have different goals which have been chosen by humans so they results won't sound the same.  You may really not like the choices one system makes vs. another so it is worth listening to them ahead of time.

Personally I like Dirac and JL Audio (subwoofer only) and Anthem, but I have not heard every system. Please audition and compare for yourself.

Amplifier

B&W 802 D3 Impedance Curve

I don't want to spend too much time on this, since it is a very expensive proposition, and the amount a  new amp can benefit the bass output of a system is just more than trivial.  Noticeable but not a major difference. In my humble experience, amplifiers are more susceptible to low speaker impedance ( < 4 Ohms) than the math leads us to believe. A dip in impedance in the 80-300 Hz range often occurs with speakers and some amps are going to be more susceptible to this than others. This B&W 802 chart from Stereophile is a great example of a tough speaker between around 100Hz to 1 kHz.

When auditioning amps, you want to look at a chart like this and see if you hear significant differences in the low impedance range, as well as whether or not you like the change. You might actually like a less beefy amp as it may give you a built-in loudness curve with this speaker.  That is, there's no right answer. A megawatt amp may not sound right or be appropriate for you, but if you feel you need more bass, in the region the speaker dips this could be a reason why.

Remember when listening for this to listen at your normal listening levels. If you normally are working in the office listening from a distance, listen at that level. Don't try to judge this feature based on maximum output. 

Room Treatment

The right room treatment can make 2-way speakers sound huge and eliminate the desire for a sub altogether. Even if you treat the room and still want a sub-woofer, you'll find the improvements in clarity, smoothness transparency and imaging completely worthwhile.  To many audiophiles, the amount of improvement in bass performance room treatment brings to the table be shocking when first heard.

Treatments come in two flavors, so lets talk about them separately. I want to emphasize, as a committed apartment dweller, you can get treatment that work great in an apartment. Mine have outlived every other piece of gear I own. 

GIK Acoustics

Panels

Panels on the walls and ceiling are a combination of diffusion and absorption that are mainly effective in the mid to treble range.  But wait, you are trying to fix a bass problem right? Well, what if the problem is not too little bass, but too much midrange or treble?  A live room will sound much brighter.  Reduce that and, like magic, the bass appears like a Spanish galleon emerging from the ocean at low tide.

If you are willing to spend thousands of dollars and countless hours buying a new sub or new speakers and setting them up, I highly encourage you to treat the room as best you can first. The best most cost effective way I know of right now is to ask GIK Acoustics for advice. Their panels are very effective and far below the cost of millionaire installer equipment from other brands. 

Bass Traps

Also available from sources like GIK, bass absorb bass but more importantly de-energize room modes, which not only makes speakers sound better but if you use an EQ either via Roon, miniDSP or via room correction systems the bass traps will greatly enhance their efficacy and even allow you to treat nulls which an EQ alone could not.

I don't know why but GIK doesn't promote their soffit traps very much, I find them ideal for an apartment as I can stack 2 of them in a corner and they work really well. 

But I Still Want a Subwoofer!

That's fine, get one. I own a Hsu VTF-15 which I use with six panels, two bass traps and a miniDSP unit and it's amazing, but if you get a sub treat the room first anyway. It will help the sub perform better and you'll have lots of other audiophile benefits.  Next, consider the setup effort. A subwoofer has to integrate with your main speakers as well as the room.  This means the following settings must be configured:

• The crossover points 
• Delay / phase 
• Exaggerated room modes must be clipped via EQ
•  If you have room treatment, or other null eliminating items like open layouts you may be able to fill in nulls as well.

So, before you buy, ask yourself how you will do this. Dirac and other room-correction systems will do this all automatically as will some new subwoofers. If you have time and desire to learn to do this manually, I suggest you search the Room EQ Wizard forums since it is a popular tool used to configure DSP equalizers. I don't use it so please don't ask me for help, I use OmniMic and am very happy with it.  Neither of these is a push button subwoofer configuration tool though.

For another take on this subject you might want to look at this article: 

https://www.trinnov.com/en/blog/posts/myth-busters-subwoofers-in-stereo-systems/

What About Two Subwoofers?

This is a great idea, especially in larger listening rooms if you can place them optimally they can cancel out room modes.  Note that optimal placement takes time and effort and it usually means asymmetrical locations.

What About small Subwoofers?

The myth is that subwoofers with small diameter's are "faster." This is a myth.  Large diameters, powerful motor structures and big amps are what you want for bass, but!! Small subwoofers may excite the lowest room modes less due to their limited bass output. In this sense, for many listeners small subwoofers may sound better and be easier to integrate into a room.

So, yes, the idea of using a small subwoofer in a room is something to consider if you don't have enough room treatment, EQ, placement options, but it is still technically a myth that the drivers are faster or lower distortion. 

What about the Distributed Bass Array

To oversimplify, the DBA or  Audio Kinesis Swarm uses four subwoofers to cancel room modes. Please read details directly from the vendor as I am not a fan and therefore won't do it justice.

While I was a fan of this idea due to the innovation and possibilities it offered I never really warmed to it due to the physical complexity.  For me, I want my system simpler, smaller, and tripling the number of speakers in my home has no appeal at all. I am no longer a fan of this idea due to the fan boys and how cultish they have become. 

While the vendor's promotion online has been fair and honest the fan boys of this system are out of control.  From reading their posts and their attacks of the ideas posted above it is clear to me the fan boys have never heard a well integrated single sub so their opinion of any other ideas is at least misinformed if not down right deceptive.  At least one account seems to have been created specifically to show up and misquote Floyd Toole's writing to me.  You will notice the DBA cult because of the insistence that the DBA and only the DBA can solve all things bass in a room. This is how cults work.  They say "you have a problem (maybe you did not know you had this problem) and only our idea/savior/politician can save you."

Summary

• Treat the room if you can and only when done there look around and see if you want a sub
• Consider tone controls and equalizers as cost effective alternatives, even if you can't treat the room.
• Consider the amp/speaker combination, but beware the cost and limited improvements possible.
• If you still want to get a subwoofer, look at the alternatives and consider the integration effort as more important than the "quality" of a subwoofer.  How exactly are you going to be done setting it up? What good is a megabuck sub if you are only going to set it up half-way?
• If the DBA seems like the easiest and most convenient way for you go and you have the space for it go ahead. 

Financial Disclaimer

Before anyone asks I have no financial interests in anything related to audio equipment or acoustics.  Whether you buy the brands I suggest above or find better one's I have no financial personal interest, direct or indirect.

IM Distortion, Speakers and the Death of Science

One topic that often comes up is perception vs. measurements.

"If you can't measure it with common, existing measurements it isn't real."

This idea is and always will be flawed. Mind you, maybe what you perceive is not worth $1, but this is not how science works. I'm reminded of how many doctors and scientists fought against modernizing polio interventions, and how only recently did the treatment for stomach ulcers change radically due to the curiosity of a pair of forensic scientists.

Perception precedes measurement.  In between perception and measurement is (always) transference to visual data.  Lets take an example.

You are working on phone technology shortly after Bell invents the telephone. You hear one type of transducer sounds better than another.  Why is that?  Well, you have to figure out some way to see it (literally), via a scope, a charting pen, something that tells you in an objective way why they are different, that allows you to set a standard or goal and move towards it.

This person probably did not set out to measure all possible things. Maybe the first thing they decide to measure is distortion, or perhaps frequency response. After visualizing the raw data the scientist then has to decide what the units are, and how to express differences. Lets say it is distortion. In theory, there could have been a lot of different ways to measure distortion.  Such as Vrms - Vrms (expected) /Hz. Depending on the engineer's need at the time, that might have been a perfectly valid way to measure the output.

But here's the issue. This may work for this engineer solving this time, and we may even add it to the cannon of common measurements, but we are by no means done.

So, when exactly are we done?? At 1? 2? 5?  30?  The answer is we are not.  There are several common measurements for speakers for instance which I believe should be done more by reviewers:

- Compression
- Intermodulation ( IM ) Distortion
- Distortion

and yet, we do not. IM distortion is kind of interesting because I had heard about it before from M&K's literature, but it reappeared for me in the blog of Roger Russel ( http://www.roger-russell.com ) formerly from McIntosh. I can't find the blog post, but apparently they used IM distortion measurements to compare the audibility of woofer changes quite successfully.

Here's a great example of a new measurement being used and attributed to a sonic characteristic. Imagine the before and after.  Before using IM, maybe only distortion would have been used. They were of course measuring impedance and frequency response, and simple harmonic distortion, but Roger and his partner could hear something different not expressed in these measurements, so, they invent the use of it here. That invention is, in my mind, actual audio science.

The opposite of science would have been to say "frequency, impedance, and distortion" are the 3 characteristics which are audible, forever. Nelson pass working with the distortion profile, comparing the audible results and saying "this is an important feature" is also science. He's throwing out the normal distortion ratings and creating a whole new set of target behavior based on his experiments.  Given the market acceptance of his very expensive products I'd say he's been damn good at this.

What is my point to all of this?  Measurements in the consumer literature have become complacent. We've become far too willing to accept the limits of measurements from the 1980's and fail to develop new standard ways of testing. As a result of this we have devolved into camps who say that 1980's measures are all we need, those who eschew measurements and very little being done to show us new ways of looking at complex behaviors. Some areas where I believe measurements should be improved:

• The effects of vibration on ss equipment
• Capacitor technology
• Interaction of linear amps with cables and speaker impedance.

We have become far too happy with this stale condition, and, for the consumers, science is dead.

The SNR-1, Room Response and Roon

It's been a long time since I had the tools out, and I've been playing with a lot of ideas so this post will be a bit of a ramble. Remember the SNR-1? A 2-way with a 6.5" Scanspeak Revelator mid-woofer?


They are still my personal reference speakers. Several things have come together in my listening area. I am switching over from Logitech Media Server to Roon. Honestly being on a subscription software service bugs me, but Roon's music service and DSP capabilities have won me over. I'm also setting my HT again, and as before, am doing my own room correction.

Anyway dear readers, to take advantage of Roon's DSP capabilities I pulled out OmniMic again (thanks Bill Waslow) and measured the speakers in place. First thing to talk about is just how much bass a good 6.5" driver can produce.The red chart below shows you the original speaker response, while the black is the response after correction:

 

The Start Line

Some of you may see this 1/6 octave plot and wonder why the bass is already so smooth. The answer is in part the room and in part the room treatment. The wall behind the speakers has a large opening to the rest of the apartment, making certain modes very difficult to start. I also use a pair of stacked Soffit Traps and 5 other acoustic panels around the area. All from GIK Acoustics. 

I should be clear here: I cannot achieve results this good with so little compensation without the room acoustics. They enable the EQ.  

The Goals

Having a lot of experience in motion picture measurement and calibration as well as doing the same in my multiple apartments I had clear and simple goals in mind. Absoltuely flat response was NOT one of them. Also, I know the microphone was set low to the tweeter, so I wasn't worried about the last octave drop-off.  I also know how easy it is to get carried away with EQ, so here were my goals:

• Ensure a smooth bass response
• Match the two speakers to one another

The truth is I really like the sound of the speakers from the start, I did not want to create lab instruments, I just wanted to see how much of the limitations of my apartment I could correct for.

The Process

I played ripped tracks from the OmniMic CD , observed the frequency response in real time while I adjusted the EQ in Roon. Honestly the hardest part of this was figuring out the Roon nomenclature. They use "Parametric EQ" for things that affect all channels, and "Procedural EQ" for exactly the same, but they adjust 1 or more channels. 

The Result

Using Roon and OmniMic I was able to very quickly flatten the response with the judicious use of two parametric filters, shown below.

The left speaker is placed much farther away from the side wall, so I really did not have the same issues at all, and it's correction curve is boring. However, I did use the Right channel as a template and forced the Left to match throughout the mid-treble area with a delicate, single filter. The phantom center is much more filled in and voices distinct and close to palpable.

One other thing, take a look at the original chart. This response was WITHOUT a subwoofer! If you make the SNR-1 or buy a model from Fritz Speakers with similar drivers and configuration you are going to get awesome bass out of a small monitor. If you don't, it's your room.

Oh, of course, you could just buy a Wilson or Gamut if you prefer.

Here's more information from one of the most famous kit designers on earth, Troels Gravesen. Most of Troels' kit designs include charts showing how much a speaker changes in a room, vs. the ideal/anechoic expectations. He calls it "room gain" and here is an example from his Fusion kit:

Every room is different, so you can't use these charts to predict the response of any given speaker, but it illustrates the point: The actual bass output of speakers in a room is more than their spec.

Adendum 

In the end I added about 3 dB to the bass by using a Low Shelf filter at 82 Hz. It's still not chest thumping, but adds some body to the music. Here's an image of the filters. The Parametric EQ works on both channels at once, so it acts like a tone control. I then used 1 Procedural EQ per channel for the room correction needs which I documented above.