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.

Thanks,

puppyt
Ag insider logo xs@2xpuppyt
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.

Tim
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.
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:

https://www.harman.com/documents/multsubs_0.pdf

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.)

Duke
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.


https://en.wikipedia.org/wiki/Double_bass_array
This question is probably just hypothetical since I doubt my wife would approve. even though she is very understanding about big speakers. I use Bill Fitzmaurice designed HT Tuba folded corner horn subs (18 cubic feet each) and love them.  If I added two more of these subs to my system all four subs would obviously have to be in the room's four corners.  I understand that asymmetrical placement is a part of the swarm sub idea, but would four horns in the four corners achieve enough improvement to be worthwhile?
While I am a huge advocate of acoustics treatment, the op mentions they have a small listening space  (Hey op, what are the measurements). Good, emphasis on good, bass control with acoustic treatments means large acoustic objects. That may not be feasible in the space. With the exception of resonators, which can still be large to be effective, or too narrow band, any absorber is going to be big.  With two subs, the nodes will be much less pronounced and easier to control with acoustics.

erik_squires8,841 posts04-17-2020 1:59pmSpend all the money you were going to spend on a 2nd sub and treat your room first. Talk to GIK. Then see if you still feel a 2nd sub is needed.

noble100: "Virtually anyone with fairly extensive experience utilizing more than 1 sub in their room and system, will agree that 2 subs perform twice as well as a single sub and 4 subs perform about twice as well as a pair of subs." 
clio09: "LOL. This one's a classic. Most of the time I avoid your drivel so you probably said this before multiple times and I missed it. Just had to call you out on it this time. LOL."

Hello clio09,

     Please excuse my drivel that tends to get your panties in a bunch.  I have chosen to ignore the sticks and stones you have thrown, btw like a sissy, in my general direction. 
      I'm not exactly sure what your major malfunction is, but I believe it may have something to do with me completely and factually shutting the door on your notions about the existence of true stereo deep bass below about 80 Hz.  Facts can be such stubborn, enlightening and inconvenient counterpoints to notions of nonsense sometimes.  
     Fortunately, your avoidance. obfuscations and denials of the scientifically and anecdotally proven truths contained in my quote above, have no effect on their veracity.  

Tim 
Daveyf1 wrote: " The more subs in the room, IME the easier it is to overload the room....and this really needs to be taken into consideration. "

If we’re talking about a setup where the user is careless with the level control for the sub(s), then I suppose that’s true.

However in a setup where the user takes care in setting the level of the sub(s), the improved in-room smoothness of a good multisub setup makes is less likely that a peak will "bloom" and overload the room.

That being said, there is a situation in which multiple subs might result in a rising bass response as we go down in frequency: Near the top of the bass region the outputs of the distributed subs will be combining in semi-random phase, while down at the bottom end of the bass region (where the subs are a relatively small fraction of a wavelength apart) their outputs are combining much closer to in-phase. Approximately in-phase sources combine more efficiently than do semi-random-phase sources. So if the individual subs are more or less "flat" across the bass region (not counting room effects), the net result can be too much output down at the bottom of the bass region. Fortunately the solution is fairly simple: Reverse the polarity of one of the subs, which not only corrects this in-room bass rise, but also improves the in-room smoothness. I suggest reversing the polarity of the sub which is farthest from the main speakers.

Duke
commercially affiliated with a multisub system
I think a lot of folks make the mistake and assume that all rooms sound the same when it comes to subs. The more subs in the room, IME the easier it is to overload the room....and this really needs to be taken into consideration. Having said that, it is also true that two subs can flatten out the bass response in a room...assuming that the subs are a suitable size for the room.
Since the OP has limited options of placement in his room, I would think that if he is willing to add room acoustic treatments and is considering the high level connection on the REL T9i that he will be on the right track, imho.
What drivel? He’s right. Call him out on what? You haven’t said anything! Talk about drivel!

Everyone here should be praising Tim. The DBA concept he’s explaining is not an easy one to understand. It flies in the face of all our accepted wisdom about timing and matching and symmetry. There’s no marketing angle because the advantages of using lots of subs overwhelms any one sub however good it may be. Its a hard sell not because it doesn’t work, but because it works so well its hard to believe how well it works!

The only thing DBA has going for it is that it does in fact actually work. Nothing else really does. Not really. For sure not anywhere near as good. Its physics: you put one sub in a room, you get one set of lumpy bass modes. The more subs you put in the room the more and the smaller and therefore the smoother the modes. Its not drivel. Its science. You should try it some time.
Virtually anyone with fairly extensive experience utilizing more than 1 sub in their room and system, will agree that 2 subs perform twice as well as a single sub and 4 subs perform about twice as well as a pair of subs.  
LOL. This one's a classic. Most of the time I avoid your drivel so you probably said this before multiple times and I missed it. Just had to call you out on it this time. LOL.

     Virtually anyone with fairly extensive experience utilizing more than 1 sub in their room and system, will agree that 2 subs perform twice as well as a single sub and 4 subs perform about twice as well as a pair of subs.       Yes, this is my opinion based on my experience of using initially a single sub, then a pair and currently 4 subs in my system and room.  But the theory that in-room bass performance improves as more subs are added to the room has been scientifically and independently proven, and with results documented and summarized in White Papers that are accessible online, by several acoustic experts including Dr. Earl Geddes, Dr. Floyd Toole and Todd Welti of Harman International.  You can google these names, read all about their findings and decide for yourself if you'd like.
     Of course, none of this negates the fact that the benefits of multiple subs begins to be clearly perceived with the utilization of 2 subs in any given room, especially if very good bass performance is only required at a single designated listening position in the room.  A minimum of 3 subs are required for very good bass performance to be perceived throughout an entire room.
     It's technically possible to attain somewhat decent bass at a single designated listening position with one sub. But this designated seated position needs to avoid being placed in a specific room position that avoids all bass modes in the room, which cause bass peaks, dips and even nulls. 
     Utilizing the 'sub crawl method' (google it) is a very useful tool to avoid this for both single and dual sub systems but, since it's fairly well known that dual subs in a room sounds so obviously and vastly superior to a single sub, very few individuals still use only a single sub in their systems anymore.  I believe 4425 just may be the very last human on earth with 1 sub.  Where's he been for the last 25 years? 

Tim
puppyt, don't make life more complicated than it has to be. Just buy another 210 and a good crossover like the JL Audio Or dbx Drive Rack units. Put the subs in the corners like you planned and I think once you get things set up you will be very happy with the results. You can always add more subs in the future but would wager that you will not feel the need. 
I personally use 4 subwoofers but I'm forced to to get an equivalent radiation pattern to my satellites which are 8 foot tall ESLs (line source).
People with point source speakers which is the vast majority, can do just fine with two subwoofers in the typical residential setting. One subwoofer is never satisfactory. Those who think it is will change their mind when they hear and feel what two does. 
I have 5 subs actually - two Rythmik F25s, two SVS SB 13 Ultras, and one HSU Mid Bass Module (MBM-12).  The MBM-12 is only engaged for home theater.  I use the subs for both 2 channel and home theater, but primarily for two channel listening.  The Rythmiks can play low and also play higher into the bass region so they are good for both.  I originally bought them primarily for home theater, but as I started learning more about the distributed bass / swarm systems, I thought why not try them?  It made a huge difference in my two channel listening experience.  Enrico and Brian at Rythmik are pretty easy to reach and very helpful.  Give them a shout.  My personal belief is that you're going to get more bang for your buck buying internet direct.  There's a lot of dealer mark up on those Rel subs.
In all seriousness, I appreciate the suggestion big Greg.  Can you tell me about the Rythmik’s performance? Do you use them for two channel listening, home theater or both? I am strictly a two channel listener. Would love to hear more about how you use them and how they perform. Many thanks
The Rel subs are WAY cuter than Rythmik subs!  I'd guess that most of the design intent and manufacturing cost goes towards performance, not looks, with Rythmik.
How cute are the Rythmik subs? Cuteness is a big factor.
With your room constraints and for about the same price as those cute little Rel subs, I'd take a look at a pair of Rythmik F15HPs.
I have a REL S5 SHO, and it blended perfectly. I almost went for the ML balanced force, but after reading rave reviews about similar REL performance AND its ability to blend I went with the REL. Its amazing how much it added to my system. You can't hear a thing directly from it but the size and power of the music, increased dramatically. 
I should have done it years ago, but way back, subs sounded fat, slow and sloppy to my ears. Not anymore. 

" Doesn't the Swarm include a fundamental parametric equalization adjustment?"


Hello m-db,

     The AK Swarm and Debra DBA systems both use the same Dayton SA-1000 sub amp/control unit.  It has very limited equalization functionality, I believe mainly to mitigate the effects of floor to ceiling slap echo.  
     I've never felt a need for any PEQ adjustments in my room but I've read about other 4-sub DBA users utilizing separate PEQ and DSP components with claimed positive results.

 Tim

If you were to do an in home comparison with your ML you'd most likely find the Force 210 out performs the T9 in many ways.

The connectivity alone allows for XLR and RCA inputs as well as a Multi-Output that facilitates daisy chaining most any other subwoofer with a compatible input. 
Of greater importance would be the ability to use ML's PBK equalization kit.

In my experience using four powered subwoofers in three different homes, simply using four subwoofers is NOT a panacea for low frequency equalization. You may even find, as I have, that two crawl test positioned subs satisfactory. 

With the limitless system, room, and personal taste variables each of us will have differing goals and results. Take it slow.

Doesn't the Swarm include a fundamental parametric equalization adjustment?

Good luck and have fun.    
Hello puppet,

     As millercarbon stated, I also agree that you will attain the best bass quality utilizing 4 subs, even in a small room.  In fact, 4 subs will actually make your room seem larger and you’ll also notice improvements in the sound stage imaging and size.
     I know of another Audiogon member, hleeid, who had a small office with very limited floor space for 4 subs.  He purchased the Audio Kinesis Swarm 4-sub bass system and the AK owner, Duke Lejeune, detailed how to locate one of the four subs on the floor and the other three subs off the floor supported on shelves.  Each sub is relatively small and light, at 12”x14.5”x28” and 40 lbs,with a 10” aluminum long-throw woofer in each sub.  They have a rated bass extension down to 20 Hz +/- 3 dB.       The price is about $3K, including the 1,000 w class AB amp/control unit to power all 4 subs.  I’d suggest you call or email Duke to discuss.  Or, you could pm hleeid and ask him about it first.

Tim
I can assure you that one sub will work seamlessly in some setups. I may just be lucky.
Spend all the money you were going to spend on a 2nd sub and treat your room first. Talk to GIK.  Then see if you still feel a 2nd sub is needed.
millercarbon:

Many thanks for your detailed advice. Much appreciated.
Whatever you like. In all honesty what seems to matter most is numbers not quality, not power, not any of the usual stuff everyone says. It is of course better to have four really good subs than four puny weak ones. But four puny weak ones beats one of just about anything. Something like that. Hard to explain until you do it. The minute you experience four or five decent subs in the room, well you won't believe it. The bass is of a quality so much better than you can get with any one or two subs its really hard to explain. Because whatever I say it will be interpreted in the framework you're familiar with, two speakers and one sub, maybe two, and its just not the same.

Now given your particular situation that might not be practical. Even though the additional subs could be fairly small and yet still work quite well, maybe some small Hsu sub that fits behind a sofa, you might really be stuck with just the front corners.

If that's the case then simple, get two of the Tekton subs. These monsters use four drivers and stand tall. Because of the way they are made each one is kind of like having two subs spaced 4 feet apart. Or whatever. You get the idea. DBA works best when the subs are spaced far apart and asymmetrically around the room. The idea being to create more small modes in spread out locations. Well the Tekton sort of does this by the way its made. Plus it is a powerful, efficient, killer sub. Resist the urge to place them symmetrically or in relationship to the mains. Low bass doesn't work that way. Look at my system. They are asymmetrical, no two the same distance from a corner, and yet the bass is wonderfully seamlessly integrated.

Then I would get the Dayton SA1000 to drive them. Perfect amp for this, and you can add more if you want without needing another amp. Yeah I have two but check Tim noble100 he has almost identical setup with one Dayton and loves it to death. 
millercarbon:

Would you add two more ML's or something else?
Keep the ML sub, and add two more.

The physics of low bass is each sub creates its own lumpy bass peaks and dips. Using lots of subs each one creates peaks and dips in different places, and they're smaller because with more they each put out less. The total result is much smoother, deeper and more accurate bass. 

This cannot be done with any one sub. Physically impossible. 
Check it out. https://systems.audiogon.com/systems/8367 Search Swarm, DBA. Only way to go.
and one sub is all it takes
because of a mandated poor bass listening position I finally discovered a fantastic sub(B&W DB1) that truly added the weight I was missing with every high end speaker that I’d tried. I run the main speakers full range and position the sub on the inside of the mains close to the right speaker.The one thing that is CRITICAL is the phase setting. I have 4 choices. 270 degrees is vastly superior to the other 3 in my system. The difference is dramatic and quickly selected. The DB1 properly set up is absolutely seamless..it really is and that’s with the crossover set high for most situations. Last thing. I’ve had too many speakers for my own good and each needed a particular phase setting. Go figure.