Why the fascination with subwoofers?

@rauliruegas 
You are really mad at Ralph. Oh well...

FWIW:

and he still posting that he needs only two subs because his speakers goes down 20hz ( solid hz. ): so what?, that confirms that he did not understand yet the overall subject in this thread and in the reality of any room/system

I believe he's talking about the same approach Earl Geddes, Hartman, etc do: 4 sources playing subwoofer frequencies to flatten response across multiple seating positions. In his case, per his comments, his mains go down to 20Hz so they are playing in the subwoofer region as well. He will add two subs in parallel to the mains so he will end up with 4 sources playing subwoofer range. That's all. Common sense to me (coupled with some theory/knowledge). 

rauliruegas,

I don’t understand why you’ve been going after atmasphere/Ralph, either. Yes, his primary business is designing and selling high quality tube gear but it’s a mistake to assume his audio knowledge and experience is limited because of this.
I’ve been reading his posts for years and it’s obvious he has an abundance of knowledge on a wide range of audio subjects that I’m sometimes surprised by. For example, he knows Duke Lejeune, owner of Audio Kinesis that sells the Swarm and Debra 4-sub distributed bass array systems, and is well versed on the subject of attaining good bass response in rooms smaller than recital halls.
He’s been setting up very good sounding systems in small audio show rooms for years, often utilizing subs and dbas to get the bass sounding right in these rooms which is almost always very difficult to do.
His personal system speakers are capable of very good deep bass output down to 20 Hz but he’s still adding a couple of custom subs because he already knows through experience that this is the best method to further smooth and improve bass response in his entire room.
I’ve explained the above because it appears from a few of your posts that you’re unaware of Ralph’s breadth of knowledge and experience and the value many Audiogon members, including myself, place upon the information, opinions and advice he shares on a consistent basis.

Thanks,
Tim

pwhinson:
" I have to admit that with my Magnepan 20.7's I have toyed with the idea of adding a subwoofer but in the case of the 20.7's in my room they measure flat down to about 28hz and only then start to roll off.  So I would not want to crossover the signal "from" the maggies to a sub, rather I would want to blend a sub in beginning at around that point of 28hz.  BUT of course there's just very little music down there I don't believe however."

Hello pwhinson,

     I've only listened to the Magnepan 20.7s once (driven by either Boulder or Bryston amps at Audio Connections near Chicago) but still know I'd definitely already own a pair if I was only richer.
     I remember the sound as the usual great Magnepan midrange, treble and imaging  of their top model combined with a much deeper bass response than I was expecting.  It was not only well extended deep bass but incredibly high quality bass that was just as fast,smooth and highly articulate as the midrange and treble response, resulting in a seamless quality to the sound from top to bottom that was very impressive.
     You're correct that there's not a lot of musical content requiring reproduction of frequencies much below the 20.7's bottom limit of 25-28 Hz. 
     I'd only suggest adding subs to your system if any of the following is important to you:
1. A system that's completely capable of reproducing all humanly audible frequencies from 20 to 20,000 Hz.  While it's true that there are few recordings with deep bass down to 20 Hz, and if it exists it's probably summed L/R ch mono bass, there are some that do contain bass this deep (but not none on vinyl) and you'll only know it's there if your system is capable of reproducing it. There's also the possibility that new physical or downloaded music formats are introduced that allow for full range (20-20K Hz) recording and playback.  I have no advanced knowledge of any new formats but even some existing formats (like cds, blurays and hi-res digital files) are currently capable of full audible range recording and playback.
    It may also be useful to consider the types of music you listen to.  I believe only pipe organs, classical, some rock/jazz and electronica contain notes this deep. 
2. A system that is currently used for both music and home theater or you're considering using it for ht use in the near future.  There's an abundance of sound effects and even some music that has very deep bass content on ht content like regular and 4K bluray discs as well as many premium channels on subscription HDTV services.

     If either of the above is important to you, I believe adding subwoofers to your system would be beneficial.  I think you have 2 options if you're interested in extending and improving the already very good bass performance of your 20.7s.
     One option is to add 2 good powered subs of your choice and experiment with their positions in your room as well as the volume, crossover frequency and phase control settings on the subs until the bass sounds best to you (smoothest, most natural and most seamless integration with the 20.7s). 
      I suggest you use 2 subs, rather than a single sub, because 2 will provide faster and more agile bass that more closely resembles the bass supplied by your 20.7s as well as better smoothing and adding impact to the overall bass response in your room. I would also advise you to calibrate the best bass response for music because, in my experience, this will also work well for ht use, too. 
     Of course, the brand and model of the subs is your choice but I'll recommend a few that I think might work well in your system and room:

JL Audio F110- 10" long-throw aluminum driver, 1,200 w amp in a sealed enclosure, 13.5"W x 14.24"H x 16.51"D and 52.7 lbs., about $1,500 ea.

REL T9i- 10"  long-throw aluminum driver, 300 w amp in a sealed enclosure, 13"W x 15.2"H x 16"D and 41.3 lbs., about $1,300 ea.

SVS SB1000- 12" fiber composite driver, 300 w amp in a sealed enclosure,  13"W x 13.5"H x 14"D and 27 lbs., about $500 ea.

     I'm fairly certain the addition of 2 subs, properly positioned and configured, would prove to be a good improvement to your system's overall bass response for both music or ht. The major downside to this approach is that it would only extend your deep bass response to about 24-25 Hz.  You would clearly perceive a smoothing to the bass and additional bass impact but, unfortunately, no deeper bass extension.


     However, I'm certain that another option, a 4-sub distributed bass array (dba) system, would prove to be the greatest improvement to your system's overall bass response and, in my opinion, the best solution I'm currently aware of for supplementing and extending the bass response and integrating seamlessly with any pair of speakers, but especially with 'fast' and detailed speakers such as planar-dynamic and electrostatic panels. 
     I'm certain this system would work very well for your system because I've been using a dba system with my fast Magnepan 2.7QR speakers for about 4 years now.  I realize the 20.7s are far superior fast speakers than my older models, but the forces behind dba systems' excellent bass performance and integration work equally well with virtually any pair of main speakers.
     This system has worked so well for my system that I started a thread about it a few years ago, here's the link if you'd like to know more details:

https://forum.audiogon.com/discussions/anybody-else-using-a-distributed-array-sub-system

      Also, here's a link to an Absolute Sound review of the Audio Kinesis Swarm dba system, which is almost identical ( the Swarm subs are just a bit wider and shorter) to the AK Debra dba system that I own:

http://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/

     There are 2 options if you're interested in setting up a dba in your system:

Complete AK Swarm or Debra complete dba system- these include four 4 ohm subs with removable port plugs for either sealed or ported operation, each sub has a 10"aluminum long-throw driver, 14.5"W x 23.75"H x 10.375"D and 43 lbs., and a Dayton Audio SA1000 1K watt class AB mono sub amp that powers all 4 subs, about $2500 for the complete system.

Custom dba systems- these would involve buying 4 powered subs of your choice and positioning them asymmetrically within the room for optimum performance.  This is the most flexible method of creating a dba system since you can choose the quality of the subs used for bass extension and maximum spls. 

     Either AK dba complete dba system will provide flat frequency response from 20-100 Hz with a maximum output of 113 db at 20 Hz. The bass extension and frequency response performance levels of a custom dba system will vary depending on the exact subs selected.  The excellent bass integration quality with your 20.7s, however, will not vary depending on the exact subs selected and will remain constant.  Which means a very good dba system could be created for as little as $2,000 if 4 SVS SB1000 subs were used but an 'ultimate' dba system could be very expensive if very hi-end subs are used.  Considering this, either AK dba may be the best bargain given their high level of performance in bass extension, accuracy and maximum spl level.  

Sorry I wrote you a book but I wanted to give you as much info as I could.

Tim

Dear @lewinskih01 : Good that make sense to you but I think that you are losting a main critical premise/parameter/characteristic on the subs overall subject, been 2 or 4, and is that separated subs ( 2-4 . ) is the way Harman speaks and I additional posted that a main target integrating ( at least. ) two subs is to put at minimum the IMD levels in the main speakers and both targets, the Harman and mine, can’t be accomplished in the way your " common sense " says to you.

Got it the huge differences? 2 or four subs permits to place it in the ideal position for the room/system and the same time that the IMD in the main speakers goes way lower than ever.
You can't or maybe is almost imposible try to find out/playing with several positions of two subs along the main speakers woofers . Normally the main speakers mid/high frequency range we already has/set up in the rigth main speakers position and we can't make many position changes to see if the bass improves and with out lowering the main speakers IMD ! ! 

In the other side and again makes no sense to me follow talking of more than one seat position to listen a stereo room/system because exist only one seat position that is " rigth/correct " to listen spot-on the mid and high frequency ranges.
Who cares other than one seat position to listen it if really does not exist. Makes sense to you? or is that you only listen to the bass range? ! ? ! ? ! !

My post is not against atmasphere and again I’m only disclosing facts that he showed don’t understand very well yet. I’m sure that when he already have his two subs his way of think could be a little different or maybe not ? !.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Dear @lewinskih01  : but how can a universal amplifier design handled  woofers ( passive speakers. ) in better way that the dedicated amplifier on a self powered subs that was designed in specific to fulfill the woofer needs?

makes you sense too?

I'm sorry but now your last posts to me make no sense at all. Please don't lost or move from the subs focus/specific subject. Forgeret about atmasphere but not because you want to " deffend " it ( that tehre is no reason to do it because you have to deffend him for nothing because no one is against him. ) lost the main subjects in this thread.

R.