Do you use a subwoofer?

[Chris]

Do you use a subwoofer in your two channel HiFi? Comment with your experiences and other thoughts.

[speakertom]

In the past I have used subwoofers to great benefit. Unless you have several large drivers with high xMax in your main speakers you probably want to get subs. Not only will they extend the low frequency response of the system they will unload the woofers and minimize IM distortion as the woofers try to reach down to low frequencies. Generally crossing over around 80Hz will prevent localization of the subs. If the crossover is at least 12dB/octave, below the crossover point the woofers will not experience any further excursion as the frequencies go down, given the same drive level. With my 4 large xMax 12" drivers in the bases for the eggs I have not run into any problems. If I do need subs in the new room, I will probably mount them in the floor of the room with the basement underneath as the "sealed box" enclosure.

[Dave R]

I use subwoofers.  In fact, I recently went from two to four with a huge increase in quality.  I've been interested in trying DEBRA, which is a distributed bass reflex array (or something similar).  I finally got the shelves along the back wall out of the room an figured I'd give it a try.  I went to the web site that describes how to set up DEBRA and the description on how to locate the four subs was, at least for me, too subjective.  I did some further research and as you might expect there are other thoughts on how to get the best bass.  I knew I had found the right one when it said that it doesn't matter where in the room they are as long as they are not all clumped together.  I can get behind this sort of set up.  As it happens, it does matter somewhat where some of the subs are located.  Here's sweep of the two main subs that are stands for the left and right speakers:

Yikes!  The problem is trying to set the level where you get good bass without the peaks overwhelming the rest of the bass spectrum.  This is with two subs on the back wall where the shelves used to be, randomly placed:

Big improvement!  After some moving subs around and trying putting one of the subs out of phase here's where I ended up:

No change in EQ.  I am using a low shelving filter that the speakers are designed to have in the controller, but it hasn't changed.  I ended up with one sub on the back wall out of phase and one on the wall in the foot of the L near the treadmill, for those of you that have been here.  Here's the whole system response:

So much easier to get the bass balanced with everything else without those peaks and suck outs.  The bass is remarkably consistent as you move around the room as well.  The biggest surprise was how much better the lower midrange is with things as they are now, I was surprised that the improvement extended up that far.

[sailor]

I have used the same stereo pair of sub-woofers since 1985 when I bought them new. I have a pair of Janis W1's driven by a 150w/ch chip amp off of ebay and a Marchand Bassis Parametric Equalizer with added built in Marchand XM9 electronic crossover boards set at 45Hz. The Marchand has been modified extensively with usual DIY tweaks plus including adding a 2nd power supply so each channel has its own PS.
I first bought into the BS of only needing one sub because of the supposedly unidirectionality of audio below 80hz. I found when I was listening to bass heavy material with one sub my attention always focused on the one sub. I immediately got the second sub and never looked back. System measures flat to below 20Hz and 6db down at 10Hz. With the Razz I do not use them except to show off. I do use them with the Quad ESL (57's) as they are needed.


You can see the Janis behind the Volti Razz's

[sailor]

So I did a quick sweep of RAZZ plus The Janis

The sharp cut off at 20kHz must be the TrueRTA software





The peak at 100Hz is the Razz "Fun" xover  plus room node otherwise pretty good

[speakertom]

Don't look at frequency response alone. You also need to look at the level at the measurement frequencies. You can get 20 Hz bass out of an 8" woofer with EQ and with low distortion if you want to listen at 50 dB. To keep the frequency response flat to low frequencies, have low distortion, and high SPLs, you need a lot of linear volume displacement which is where subs shine. If you crossover at a low enough frequency that you cannot localize and use time alignment with the main speakers, you can also place the subs in locations that provide a more even response at the listening position. Another thing that will help frequency response across all bands and also help imaging is room treatments. Subs certainly provide the foundation (pun intended) for wide bandwidth with lower distortion and placement of the mains for the best imaging.

[larrys]

I do use subs in both my Magnepan setups. With the 1.7i's, I am using a pair of Sumiko S9's. These are very similar to the REL T-9. With the 3.7i's, I'm using a pair of MartinLogan Dynamo 1100X's. These have Anthem Room Correction built in. Since both of these setups are in multipurpose rooms (1.7i's in the den and 3.7i's in the living room, I am somewhat constrained as to the speaker and sub placement. Also, since all of my serious listening is done from one or, at most, 2 different seating positions in each room, I have optimized my systems for those positions (if I listen to either system as background, I'm in a different room). I've made many spectral measurements using my iPad running the AudioTools RTA program and a Dayton Audio iMM-6 calibrated microphone and, for both systems, can position the speakers for a relatively flat in-room response without any equalization save the built-in ASC of the MartinLogans.

Here, though, is where I apparently differ from Dave and Sailor. Neither system has a response that is flat to 20KHz at the listening position as they are set up.  Instead there is a gradual roll-off beginning at about 10KHz.  Every time I've tried to achieve a flat in-room response it sounds unbearably bright to me. So, where lies the difference? Is It because of the speakers? In the case of the 3.7i's I would presume not given their ribbon tweeters. Also I've gotten similar results when measuring my Totem Acoustic Sky's and KEF Reference 101's in the same systems. Is it where I am making my measurements (either about 8' (den) or 11' (living room) from the speakers)? In other words, it is simply room attentuation? Is it the dipole nature of the Magnepans? The results form the Sky's and 101's would seem to argue against that. Is it the level (I usually use pink noise at about 80dB average)?

A final comment. As often as I have measured spectra, tied strings to my listening chair and measured distance to the speakers, mounted a head vise to the wall behind my listening chair (kidding on this one - maybe), I always end up making adjustments by ear. Do I just need to sell all of my gear and buy two hand-cranked Victrolas with tin horns (to match my ears)?

[speakertom]

What you are doing with the rolloff is commonly referred to as a "house curve". This adjustment has been around for a long time and generally starts around 200 Hz and ends up at 20KHz.  Common values of the attenuation of SPL up to the 20KHZ point range from around 1.5 dB to 6 dB.  The 6 dB was a figure promoted by Bruel & Kjaer but is a bit extreme for my taste.

[sailor]

I adjusted the Razz tweeter about 1 and 1/2 db over stock to make up for my hearing loss. I can barely hear anything over 10kHz.
It is not harsh or edgy. Very different from the Spatial’s which did roll off above 10kHz. It was very edgy and glassy. It’s why I sold them so quickly..
I need to put the Quads back in for a reality check.

[mark]

I've also been experimenting with integrating subwoofers.

I've been working with a program called "Multi-Sub Optimizer" I heard about first on the miniDSP website, as an approach to subwoofer integration.

Its very complicated and difficult to use, and therefore loads of fun! Its also free, and the minimum users support only adds to its charm.

After lots of room measurements from a range of positions, it calculates parametric eq, gains, delays, phase, crossover frequencies and other parameters for use with each subwoofer (in my case, three subwoofers).

You can select the goal as either maximum overall flat response, or minimum variation from position to position.

The only problem I've had with it (other than its marvelous complexity) is it assumes you can independently set delays for main speakers, which is not always feasible.

I've found it particularly useful for filling in the inevitable big holes in low frequency responses resulting from standing wave cancellations.