Subwoofer Question

I currently have a Martin Logan Balanced Force 210 sub paired with Dynaudio Contour 3.4 LE speakers and a Prima Luna HP Dialogue integrated amp.  My listening space is fairly small (listening position is about 11 feet from the speakers.  The nature of the room only allows me to place a sub in the front corners of the room near the speakers so I can really only have two subs.  I have been toying with the idea of selling the ML and replacing it with dual subs, one in each front corner.  One particular sub I have been thinking and reading about is the REL t9i.  Why am I thinking about this? No other reason than the itch to tweak but certainly also to improve.

I would greatly appreciate this board’s thoughts and insights.


Ag insider logo xs@2xpuppyt
If you are using 4 corners, then a specific version of a bass array, also called DBA, but in this case double bass array, may be something to look at based on your physical implementation.
Kingharold asked, "would four horns in the four corners achieve enough improvement to be worthwhile?"

Todd Welti of Harmon International investigated symmetrical subwoofer placements using simulations, and four subs with one in each corner was one configuration he examined in this paper:

Corner placement optimizes for low-end extension, but not for smoothness.

From the paper: "One subwoofer in each corner has good low frequency support, but does not perform quite as well as one subwoofer at each wall midpoint..."

So imo four subs, one in each corner, is likely to be an improvement over two subs in two corners. Whether or not the improvement will be "worthwhile" is a judgment call, but I’ll go out on a limb and say "probably". The reason I think so is, the ear has a heightened sensitivity to frequency response issues in the bass region. This is implied by equal-loudness curves, which bunch up south of 100 Hz, such that a 5 dB difference at 40 Hz is subjectively comparable to a 10 dB difference at 1 kHz. In English, a little bit of improvement goes a long ways in the bass region, in my opinion.

Also, the Fitzmaurice Tubas are big enough that you could probably orient the mouth of each one differently with respect to its corner and get a little bit of asymmetry that way. And if such orientation is not an improvement, easy to undo.

Heaudio wrote: " a specific version of a bass array, also called DBA, but in this case double bass array, may be something to look at..."

My understanding is that a double bass array normally consists of four subwoofers on the front wall, each 1/4 of the way in from its nearest corner (this configuration theoretically producing a planar wave). Then a second identical array is placed on the rear wall. The polarity of the signal going to the rear array is inverted and it is delayed by the amount of time it takes for the sound from the front array to reach the rear wall, the intention being to cancel the front wave when it reaches the rear wall.

(Personally I try to use the term "distributed multi-sub system" rather than "distributed bass array" because the latter invites the abbreviation "DBA", which as you pointed out also stands for "double bass array". Not that I object to anyone else using "distributed bass array" abbreviated as "DBA", as the meaning is usually clear from the context.)

I will express a somewhat different experience based on my experience.  I had Martin-Logan CLSs paired with a pair of Entec LF-20 subs.  These subs each had two 10 inch woofers that were servo controlled and I had new surrounds put on by the original manufacturer. Each was probably about 75 lbs and the pair would have been about $6,000 in the late 80's to early 90's.  A very high-quality pair of subwoofers.

When I moved up to a pair of Martin-Logan CLXs, I wanted to take advantage of the custom crossovers provided by Martin-Logan for these speakers as mains, so I sold the Entecs and bought one Martin-Logan Balanced Force 210 sub.  It sounded great with the custom crossover filter.  It also had more than enough output for my 25x20x11 listening room. It is currently placed in between the mains.

What is the game changer for this subwoofer though it the ability to use the Perfect Bass Kit (PBK) to create an inverse correction filter for room nodes.  To be honest, I was skeptical at first, and put off doing the set-up for weeks, to my deficit.  The difference in bass quality and musical enjoyment between corrected and uncorrected is stunning.  You know how in some songs some of the bass notes are more prominent than others?  That ends.  Runs up and down the neck of an electric bass are now essentially equal in volume.  Same with double bass and lower cello, etc.  I agree with many above that multiple subs provide a smoother response across the whole room, which is a great reason for multiple, but in my single listening position, I can get a much flatter bass response curve than most uncorrected multiple sub systems.

@puppyt, if you have not done the PBK, it is essential before trying other things.  If you are still dissatisfied, I am a potential buyer of your 210.  I want another one, not for output, but I do think there is stereo bass information to be recovered in some recordings, principally in live concert recordings.
docknow: " I want another one, not for output, but I do think there is stereo bass information to be recovered in some recordings, principally in live concert recordings."

Hello docknow.

     I don’t know why you believe this. There are 2 factual problems with your statement:

1. Humans are unable to localize (determine where a sound is coming from) on all bass tones below 80 Hz. Therefore, we perceive all bass below 80 Hz as mono bass and there is no stereo imaging created, occurring or perceived with bass sound frequencies this deep, whether heard played live or recorded

2. There are virtually zero commercially available music recordings containing stereo bass (separate and unique left and right channel bass content) below 100 Hz. Recording engineers have known that humans cannot localize bass frequencies below 80 Hz for more than 70 years and, as a result, have been summing all recorded bass content below 100 Hz to mono on their recording mixes on all formats (LPs, CDs and even high resolution direct to digital music files) ever since.
     If you doubt this, just try to identify a single commercially available music recording from the past 70 years, on any format, that contains stereo bass below 100 Hz. If you find a single example, it will be the very first that I, and millions of other music lovers worldwide, are aware of.
     So, even if you are superhuman and can localize bass sound tones below 80 Hz and setup your system to reproduce bass frequencies below 80 Hz in stereo, there’s virtually zero music content available worldwide to play on it. I’d suggest this makes the debate, over whether or not true stereo deep bass below 80 Hz is feasible, moot.  Wouldn’t you?
     Current direct to digital high resolution recording technology actually is capable of recording music with separate and unique left and right channel bass content below 100 Hz. The reality that recording engineers still sum the bass below 100 Hz on these recordings to mono is due to the very important truth that fact #1 from above still applies, humans are unable to localize bass sound tones under 80 Hz.
     I hope these facts have convinced you that the pursuit of a system capable of reproducing true stereo bass below 80 Hz is futile.  Instead, I suggest you use a minimum of 2 and up to 4 subs to create a high quality mono bass system with bass extension down to a least 20 Hz. I can describe in detail how and why to do this in a future post if you’d like.