Honest Experience on Effects of Subwoofer Please

As a last comment, I previously mentioned 8 subs. What I plan on doing is 8 drivers in 4 enclosures.  I'm doing this because in comparison to live performance I feel my bass which is wonderful for a home system, needs just a little more authority. Doubling the drivers only gives you another 3 dB but I think the array will pressurize the room better for lack of better terminology. It may not work. The problem might be with the dynamic range of the source material. It will definitely lower distortion in the bass so it should be worthwhile in the end.   

I think the issue with subs is its far more complex than it appears:

1) SOURCE MATERIAL has varying bass levels. The deep bass in source material is all over the place, and its not your fault.  It's not consistent at all and we find a large variance in quality.  Many records, especially old english records have no bass (Genesis, Selling England by the Pound, Kate Bush, etc).  Many streaming services strip bass out to prevent clipping within their processors.  If you adjusted your sub to sound good on one thing, the next thing will likely be very different.  This makes one think its the sub not working correctly when its no such thing.   

Conversely, if you set up your sub to sound good on Eminem, very little has that much bass in it.  Technically, this is where recording quality has improved dramatically over the years but old recordings or some broadcast mediums roll the bass off tremendously.  

So the music you play may determine if you say "my subs don't do anything".. 

2) SUB LOCATION in the room is also greatly varied compared to someone else.  Since most of us are horrible about setting up subs in room, or we love to use just one-in the dead center between two speakers (the single WORST place) - we get vastly varying results of a given model of sub in the room.  Quite often this center position is the null point in the room and the owner never tries a different place because he or she has been told or mistakenly believes "they belong there".    

3) Use of HIGH PASS FILTERS in line with mains is very audible, introduces a major phase shift due to the larger physical distance between mains and sub, and almost never sounds good.   Using mains full range and subs low passed and then blending to taste is my preferred way, getting the subs as close as possible to the mains, maybe even on the same stand (if you are using sound anchors).  I've heard and set up many systems where this technique makes the subs almost 100% undetectable.  Not always, but certainly better than HP inline with an expensive speaker I bought for "resolution". 

4)   The idea of one big sub is not the best way.  The best plan is the opposite, multiple small subs set up on multiple different walls at different distances from corners.  This is far more likely to yield a smooth response in the room.  That's why I like Duke Swarm idea, it works. We use multiple subs in pro studios all the time, it always works better to excite more room modes rather than fewer room modes.  Then, one mode doesn't dominate.

5) Use subs somewhere from 125 Hz to 95hz on down works better than trying to get subs to work up higher.  It might work in Live sound, but not for home.   

6) Make sure you have inverted phase on the sub to see if its better.

7) do not depend on measurement with a low cost or built in system.  Those little mics that comes with receivers or lower end preamps are absolutely terrible- they have no bass, they are not accurate below 200Hz 99% of the time. 

8) People expect there to be bass in small room.  Bass wavelengths are long, and if the frequency's wave is longer than your room dimension guess what, you won't be able to hear it.  (32Hz = 38 feet long wave.  Anything room dimension shorter than this means you cannot propagate (reproduce) 32Hz in there.  20Hz wave = 54 feet.  10 feet means 60Hz is about the best you can do.

Brad

@mijostyn --

Well put. 

@lonemountain --

Ad 1). Don't see how that applies here. If subs are successfully implemented I'd only want them to reflect the variation in source material. It's about what becomes your "axis mundi" for setting the reference gain, and the rest really falls into place from here in my experience. 

Ad 2). Sure, below the Schroeder frequency the resonating nature of sound waves becomes an important factor with regard to placement and how to avoid the most severe nulls and peaks. It can be a balancing act using both digital bass management and a more pure acoustical approach of placement and sub numbers. In my dual sub setup with a higher cross-over between the subs and mains, symmetry of placement is paramount, and corner loading, while not always ideal acoustically, lends itself naturally both with regard to proximity and symmetry to the mains, while also taking advantage of boundary gain. I could successfully add two more subs for an even smoother acoustical response, but that's for future plans to come.

Ad 3).

I'm guessing this is the potential rub many are confronted with here; leaving the mains running full-range and then trying to blend in subs (slightly overlapping or not) is really dealing with two separate systems - with all that entails. 

I can understand some of the reasoning behind why many wouldn't want to employ a high-pass filter digitally over their passively configured main speakers, hereby adding another filter layer - albeit a sonically more transparent one compared to passive filters, to my ears - to an existing passive one, which is where I would suggest a more radical approach; without a HP running the mains full-range can integrate quite well with subs (I've used such a configuration years back), but my current approach high-passing the mains is done fully actively with a digital XO sans any passive cross-over, and as such is really dealt with as a 3-way system with the subs in close proximity to the mains. Every cross-over section, especially where horns are used, involves dealing with delay elaborately and eventually fine-tuned by ear, so the high-passing part of the mid-woofers is no different an aspect than high-passing the compression driver above them - or the subs for that matter just below the knee (i.e.: tune) to protect the drivers due to unloading. This is the radical nature I'm referring to above, because it's done considering the system incl. the (sub-)bass section as a whole.   

Implemented as such remember the mid-woofers will be relieved of LF which, certainly when HP'ed above 70-80Hz, equates into a cleaner presentation and bigger headroom - up to 10dB's, even. That's significant and audible for the better when carefully implemented. 

Ad 4). Why not take the next step and make it multiple larger subs?

Ad 5). I rarely encounter high-pass filters between subs and mains higher than ~125Hz. In my own setup the high-pass is set just below 85Hz, which is dictated by the upper end response of my tapped horns. I try to avoid extensive EQ'ing, but I guess I could stretch that HP a bit more towards 100Hz with some minor corrections.  

Ad 6). It's delay settings galore on my Xilica DSP. 

Ad 7). Using the ears is always the last measure here. 

Ad 8). You still hear the half and quarter waves of a 20Hz tone in moderately sized listening room, albeit with lesser clarity vs. the full wavelength due to room interaction. 20-25Hz in not in vain by any measure in my moderately sized listening space.  

AKG_C wrote, "You see, it’s very difficult and expensive to build a good subwoofer. One reason is that a sub has to move a tremendous amount of air, which places big demands on the driver (or drivers). Moving lots of air requires a lot of power and that means an amp with a huge power supply, which can cost huge money."

I have not found that to be the case with my Bill Fitzmaurice designed HT Tuba folded corner horn subs.  With a sensitivity of 104 or 105 db/w/m depending on the 15 inch driver used a modest amplifier can produce all the clean, tight  bass the music requires.  The only downside is the size of eighteen cubic ft. each. 

@kingharold , now imagine 8 of those in one room.

Since I build my own subwoofers in a rather extravagant shop I have the capability to do things others can not. Still, there are some excellent subwoofer kits available and many SOTA drivers available. These are not that difficult to build and can save you piles of money.

This really is not that complicated. A sub enclosure has to be extremely stiff, heavy and non resonant. With DSP and room control porting has become a thing of the past. You limit your low end extension that way. The only other spec that matters is the volume of the enclosure but even if you are off a little, a powerful amp and DSP have you covered. With an outboard crossover you can use passive subs and separate amps. I personally do not like amps in speakers. You can easily do a 4 woofer system for the price of two commercial powered subs if not less. Making a subwoofer look good is the hard part. I tell people to cover them with equipment carpet if they do not have finish facilities. 

With a symmetrical sub array and accurate phase and time alignment you shoot yourself in the foot not taking the crossover up to at least 100 Hz. I ran 125 Hz with my old speakers. With the subs digitally matched you would never know they were there until you turned the volume up too high. A good test is, you should be able to switch the woofers in an out and not hear any difference on a Peter, Paul and Mary album played at moderate volume 80-85 dB.  Anything with a bass drum will immediately announce the subwoofers.  Paradoxically if you use just a low pass  filter at 40 Hz there won't be any difference either but the end results are night and day. 

I'm listening to Shostakovich's 10th at this moment at only 73 dB and the bass drum is rolling off me like an ocean wave even at this low volume.