Raul,you are correct in about 50% of your arguement.But about 100%(almost)of the time,when speaking about analog subjects -:) ...First of all you simply cannot make the statement that in ALL cases two subs are the way to go,as you say it is "simply physics".Sorry,not so!And,in fact,the laws of physics CAN break down,under certain circumstances, current science believes.Also,the "Harmon" website discussion is concerning even bass response from multiple listening seats,like a movie theater.Most audiophiles have a far narrower sweet spot,as our rooms are not theater sized.
Speaking of theory,I believe your non-bending arguement is based on this(theory,not actual experience).I don't mean to be insulting,and wish to have a debate,without getting too hot under the collar.Just god fun,so here goes.....
Firstly,I have owned,in two separate dedicated rooms,the BIG dual bass systems you feel are the ONLY way to go!From my experience,your arguement ONLY has merit under certain conditions.One would be if the crossover point approaches or goes into the "mid bass".In your set-up,from what I can see,you have little ability to move the main speaker(not subs) into the listening room.So,if your ADS speakers actually go as low as you claim,the corner placement would kill bass definition.THAT itself is probably good physics,but I'll settle for my own assumption here....So,it is most likely a better scenario,for you,to cut of the main speaker,and use your subs for the remaining "non boomy" bass(due to not ideal main speaker placement).A good alternative!As I see it,your subs are out further into room,so if this is actually the case,I understand your assertion,but you do nobody total justice by hammering away,about everyone HAVING to have two subs,as ideal always!Not so!
If someone,like Downunder for example,has a superb "main speaker"(the Strads fit this),which plummet far enough in depth,why should it's design be compromised,if it is going low and with good definition.He makes a good point about affecting the design's specific design goal sound.Some of us(myself included)just wish to "tickle the bottom octave" in order to lend a bit more weight to an "exsisting superb speaker".The ROOM,and "room/specific" set-up will absolutely impact whether two subs are "needed",not to mention the owner of that system!Also,in my case,I would FAR prefer my main speaker's "sealed" box design's bass definition,over the sub's ported pitch definition,at the frequencies you adhere to!
Also,sorry,but LOW bass is NOT stereo,and if the freq is "low enough",it should NOT seem to be coming from a specific area.If it "is",you don't have it set up right!
I have had a previous dedicated "single sub set up",and two different BIG Infinity four tower designs,so I know,from actual experience what I am talking about.Those designs specifically have the ability to crossover as far up as 120 hz,so the "two sub option" is a MUST in that configuration,for best results.
In the case of someone like Downunder(I must assume),or myself(now)the MAIN speaker is SO well implemented,in the room,giving enough good low freq response,that we simply want to "goose the extreme bottom octave" a bit.What don't you understand about this?...One very good sub(sorry if you don't like REL,btw)can easily do the trick.In "this scenario",two is NOT mandatory or necessary.
Personally,my current configuration has more believeable low freq,than "any" of my previous set-ups,so I can confidently save the "few" posters, who actually care about this,some money.You don't HAVE to go with two,based on the room/set-up in specific use.Period!
Raul you are also incorrect in stating "servo bass" is the best.These types of systems(I've owned one or two)do not provide miracle cures.They are an alternative design concept,with their own advantages,and disadvantages.
The main benefit,is for a given freq response,a smaller enclosure can be used,than would otherwise be needed.This comes at the expense of requiring greater amplifier power,that is,lower effective efficiency in the woofer.
This can be a valid design choice in some situations,although in many cases cone "excursion" or "thermal" dissapation(there's your distortion,again) becomes the "limiting" factor in achieving extended bass response.
The servo controlled system has the ability to correct for non-linearities in the low freq driver itself.BUT,the "superior" approach is to employ a well designed driver that needs no correction,just as a well designed amp can be built using no negative feedback.
Concerning transient response,there is NO advantage to using other alternative systems compared to a non equalized system.This is because the transient response merely describes an alternative view of the freq response.So,by utilizing a servo controller adjusted to obtain the "perfect" transient response of a sealed enclosure with a Q factor of .5(which my current main speaker has,btw),the freq response will necessarily be the same for "both" systems,regardless of how that freq response was attained!
Although electronic methods allow for easier adjustment of the system parameters,most systems are designed for impressive anechoic freq response at the expense of "accurate" transient response!
The vast majority of bass systems(even in main speakers)store resonant bass energy.Many folks like this sound,and it is one reason why ported designs are so popular,but the ONLY way to have "accurate transient bass response" is from a sealed design,with a Q of .5!The "original" Avalons ALL adhered to this(unlike the new designs,which are just fine,but designed to "sell"),as do the current Magico designs.What these designs seek,is the absence of "stored resonant energy" particularly in the bass frequencies.To have a ported sub design substituting for "some" mid bass frequencies,that a good main speaker already has is tantamount to "throwing out the baby with the bath water".My current sealed Ascents would positively "kill" any sub,in bass definition.Unless one likes Heavy Metal as a staple for good audio.
So,if one wanted the best subwoofer,it would have to be a sealed box,but it would also have to be BIG!That is why we see so few.
I have a close friend who got the superb Magico Minis six months ago.He has low bass down to a recently measured 31 hz,in his room.Yet,some of my other audio pals are adamant that he attempt to get deeper bass.Personally I think his low freq performance is absolutely stellar and I have heard it shake his room beautifully,but the other guys want more deep bass(one of them owns BIG Pipe Dreams using two separate 18 inch subs...which suck,IMO)...If "any" sub were employed in that set-up(my friend's Magicos),to come in as high as you,Raul,have mentioned is almost universally necessary(I think you stated up to 200 hz!!) for the business of IM distortion etc,I can guarantee the "magic" of that speaker would be gone!!!No sub can match the speed,and definition of that mid/bass driver from what I have heard from that speaker.
So,we all look for something,maybe a little different from oneanother.One reason to adhere to the "logic" of there is always "more than one way to skin a cat".A popular expression,from where I come from.
Best.
