Honest Experience on Effects of Subwoofer Please

@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.  

@ryder, Subwoofers will always make an improvement more or less depending on what type of speakers you are using but there are rules that have to be followed to match the subwoofer correctly with the rest of the system. Trying to do it on the cheap can certainly be worse than doing it at all. My own experience with subwoofers goes back to 1978 when I bought my first pair. It was a love hate relationship. 

To make it brief, never start with just one subwoofer. Two is the minimum, the larger the better. You need a full two way digital crossover with delay capability. There are inexpensive ones out there now. The low pass filters that come with most subwoofers are a cheap and dirty way of messing up your system. You want to cross over as high as you can, 80 to 100 Hz anyway. I have heard systems operating at 125 Hz sound wonderful. Doing this lowers the distortion of everything else produce by your main system's woofers. Subs should always be placed right against a wall (1/4" off) or in a corner. They are more efficient this way and you cancel out a few early reflections. This is why delay capability is so important. You have to be able to match the subwoofer's phase and time with the main speakers or you just get mud in the crossover region. 

Done correctly subwoofers not only add low bass but a sense of power and effortlessness. The midrange becomes cleaner, more detailed and a system's headroom can improve up to 10 dB. That is twice as loud. There are very few systems that could not benefit from subwoofers. You can not get the feeling of a live performance without them.

@wolf_garcia, I hate to be a PITA (not really) but, if you think subs are easy to set up then you have not heard them done correctly. 

@phusis , When enough audiophiles hear subwoofers set up correctly, digital cross overs and all, the acceptance will grow like a snowball rolling down hill. All my audiophile buddies on hearing my system got subwoofers and digital crossovers with room correction. None of them are dyed in the wool analog guys but still.

It turns out that with the proper equipment subs are easy to set up. The computer does it for you. It measures your system one speaker at a time and adjusts delays and volumes appropriately. The only thing you have to do is select a crossover point and slope. The system I use now lets me change crossovers and slopes on the fly while I am listening which is very helpful. 

@b_limo , that is an interesting way to do it. What are you doing to delay the sub so the arrival time and phase are the same as the main speaker's Your version is surely visceral when you are seated but everywhere else not so hot. The realistic way to do it is multiple subs out front and a lot of power. 

@scm , I also cross over at 100 Hz. You need subs that sound good that high and they have to be in a stereo array. The rational for it is to take the load off the main amp and speakers to lower distortion and increase head room. In my case IMHO it is critical. I use full range ESLs. One diaphragm handles everything. Taking out the bass literally cleans up everything and they play louder than anyone could stand for 30 seconds. 

@phusis 1+. Live concerts are in much larger venues than a residential room. Bass is much less of a problem in larger venues. Then you have to deal with echoes which can be profound. We really do not have echoes in our homes or rather very little. The distances are too short which makes the delay shorter. We have difficulty with reflections which can be perceived as part of the music then as a distortion of the original signal. 

There are very few systems that could not benefit from subwoofers. My goal is to save people, who want to get into them, time and maybe some aggravation. I have always used a two way crossover, always, right from the beginning. I had a single sub for 6 months when I discovered that one was not going to do it. This lasted for 22 years and as I said before it was a love/hate relationship and at times very frustrating. 22 years later TacT entered the market and I jumped right one, their 1st preamp and I upgraded to another one down the line. The results floored me. Then I realized that I needed 4 subwoofers, next is 8. The TacTs time has come to an end as there is now better tech out there. I thought I was going to get a Trinnov unit but I am waiting to see what the next high end DEQX unit is going to like. It is supposed to be released next quarter. The company has not yet released an owners manual so I can get a handle on it's capability. But, from the outside it looks great.

The point of all this is that if you start out with two subs and a digital crossover like the MiniDSP you will saving yourself a lot of time, frustration and expense. Don't do it cheap. Do it right. On the other hand if you have to learn the hard way like I did fire away. You will learn a lot in the end.

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.