Why I'm not adding a sub to my 2-way monitors for music

Using Rel s5 Sho subs with my Thiel 3.7s.  I would never go back to no subs.  There is a presence and expansion of the sound stage that I would very much miss.  That said, if you listen to chamber music or music without much lower frequency information, I would image you wouldn't miss having subs in your system.  

No reason not to have a quality sub.  An SVS Pro is an affordable quality option that has a dedicated iphone app that lets you adjust the EQ, crossover, volume, etc to your liking.  I use different saved settings for music and video.  I also adjust it based on the particular album I listen to.  

It's simple, if you are serious about achieving great sound there are two requirements: room treatment and a DBA system. Read articles from Welti, Floyd and Geddes

This will lift your system above the pedestrian, that is any system not employing subs.

There is a scientific goal with treatment where the quest is to get the sound to decay a certain amount in a certain time and only broad-band absorption including bass traps will provide this. Those mentioning books as diffusers and drapes and other silly things have little effect.

EQ of course can not know how long the sound takes to decay and even if it did what can it possibly do? All it can do is boost or attenuate and there is a limit how much it can boost before your amp runs out of steam. EQ is not necessary in a good room.

I helped a friend where we installed 3 small 8" subs, the lowest we got from some scavenged drivers is about down to 45Hz. which does not really count as a sub but overpowering bass was not the reason for doing this. These 3 small sealed boxes provided a large number of peaks and partial nulls that were very much less than before. So what we ended up with, beyond the 32Hz of his main speakers was a smooth response from about 50HZ upwards. Some full nulls had been filled in that had previously cancelled any music info. In other words music previously completely absent was now heard and the overall effect was truly amazing with a sweet spot the width of the speakers. Everything improved. Consider also that no component upgrade can do what I have just outlined.

As I said, if you're serious!

No subs are the domain of the bootless and unhorsed 😁 

I love adding a sub to music - i spent 25 years without one for music - since i added one 3 years ago - im loving the sound with them. its all individual - always has -always will

With minimonitors im using the sub they way it was intended to be used. With floor standers - i still have a sub turned on -albeit barely.

I've been following this thread and have decided to weigh in and I acknowledge that all of my comments are simply my observations and opinions. I am not as interested or competent in the technical aspects of audio as @erik_squires, @millercarbon and others who frequently post. I am, however, an avid music listener and my wife and I both play musical instruments and frequently attend classical and jazz concerts. Our audio system is the vehicle for our music listening.

1. I agree with @rauliruegas that for some listeners adding one or more subs that generate significant distortion may be worse than not having a sub. I say "for some listeners" because if someone is adding one or more subs in an attempt to create the sound of a live rock concert, adding subs that generate distortion is overwhelmed by the distortion already in the music, created by the electronics of the performing artists - think Led Zeppelin, Deep Purple, The Who, etc. Having subs that produce generous amounts of bass will help get one closer to the high volumes and bass of such groups.

2. I also agree with another contributor who noted that adding one or more subs may be less important for those who listen to acoustic music - classical and jazz, folk, etc. While much classical and most jazz do have significant amounts of bass, the acoustic bass is typically part of a large orchestra in classical and is typically part of a rhythm section in jazz. For such music, and particularly for chamber music, folk and some bluegrass, the bass frequencies are a less significant part of the overall performance than in rock music, although much symphonic music has a significant amount of percussion and there are organ pieces that will challenge the best audio systems.

3. I will not disagree with the benefits of a well integrated subs or subs. They can improve not only the bass response of an audio system, but also improve the soundstage and the response of the drivers in the main speakers. This leads to another point.

4. What has not been mentioned in the prior posts is the importance of having sufficient and high quality amplification for the main speakers of a system. To provide low distortion and lifelike transient response in something like a large symphonic work, the amplifier(s) need to match the requirements of the speakers. As an example, our primary speakers are a pair of Aerial Acoustics Model 8b's. These are modestly sized, three-way floor standing speakers that are relatively inefficient (86 dB sensitivity), with published frequency response of 28 - 22k Hz +/- 2 dB. They are 4 ohm speakers that drop to almost 2 ohms impedance at certain frequencies, a challenge for most amps. Fortunately, our then dealer paired them with a Proceed (Levinson design) HPA-2 amp with specs of 250 w/ch at 8 ohms, 500 w/ch at 4 ohms. The amps have never clipped that I could hear in the years we've owned them and provide high current that drives the 10.7" woofers in the speakers with aplomb. I mention all this because a few years ago I auditioned in home a high-end Luxman piece as a possible replacement for our amp. The Luxman was rated at 150 watts/ch at 8 ohms so I figured we were fine. Wrong - the clipping was very audible and obvious at high volume transients while listening to a symphony. If I had our M&K sub integrated into our two-channel system the Luxman amp would have been splendid for at lower volumes it produced lovely, neutral and highly detailed sound.

5. I have benefited from tips provided by @millercarbon in several of his posts and in direct communications with him. His recommendations for acoustic treatments noticeably improved the music's clarity and soundstage in our listening room. I, however, share the view that while subs can be very helpful, they are not necessarily the end all. And the DBA, multi-sub approach advocated by @millercarbon is not feasible in many multi-purpose listening rooms even if one uses wireless subs. I cannot dispute the DBA may sound "better" whatever that means, but for us integrating even one M&K sub into our system was a challenge and I don't want to have to adjust the bass volume as different albums are played. I want to spend my time listening to the music. So our sub is used for home theater but not for music and we are content with the reproduction provided by our speakers and amp with both analog and digital sources.