Geddes multiple subwoofer method - 3 subs vice 4

@rauliruegas wrote:

Velodyne ( at least my HGS, not the DD models with Kevlar driver. ) were made for MUSIC sound reproduction systems and not HT where needs are different and especially on SPL.

Velodyne, REL and whatever else don't hold a monopoly on bass reproduction that's especially suitable for music. Subs that are deemed mostly that are usually too small to be an effective Home Theatre equivalent, and so they're really only good in the context of music reproduction at less than elevated SPL's. Home Theatre subs tend to be bigger (sometimes much bigger), for good reason, but the popular crux appears to be that many of them are ported variants. Whether ported or sealed is not the issue for me, but rather overall design execution and adherence to physics; both principles can deliver very good bass performance, but being sealed subs are usually smaller I'd wager they're winning the most hearts.

Therefore, as you can surmise, I don't buy into the music vs. HT subs distinction. Look at the DD18+ review and the section quoted by you. Obviously it's very good at HT duties in addition to music, so the two are not mutually exclusive - it's about having enough effective cone area to cover both bases, and moreover added cone area and higher efficiency equals lower distortion and a cleaner, more effortless bass. Win-win. 

Speaking of which: sealed or ported are only two ways to go about it. Some prefer open baffle iterations, while I myself opt for horn-based subs. Horn subs don't suffer from low efficiency or port noise, and with tapped horns in particular the horn itself does the heavy lifting, not the driver. High efficiency into the lower octaves means a very large air radiation area, and thus very little cone movement (especially from TH's, which have excursion minima at the tune) - even at prodigious SPL's. This is both the most musical, smooth, effortless and naturally full bass I've heard, and as well the most visceral, indeed downright scary powerful bass for movies to boot. The catch: they're large. 

Dear @deep_333  : I agree with you in everything and specially in " I am only concerned about my main listening position. ".

My 2 subs are rigth at the front stage side looking each to other: the drivers sound reproduction  does not goes " direct " to me as the sound from the main speas.kers.

My room is an inverted L with two parlors ( first smaller one ) in the second and main parlor is where the speakers/subs are seated in front of my listening position. Exist a left side wall behid de left sub but the rigth side sub has not a direct wall because there is is the dining room a big one with wood furniu.ture.

Through several months maybe over 1 year I tested every imagined subs positions and was exactly where are seated today what works in that room/system. 

Even that I can be seated at 4m. from the speakers my prefered and day by day listening sessions are at 2.5m ( around ).

 

R.

My room is an inverted L with two parlors ( first smaller one ) in the second and main parlor is where the speakers/subs are seated in front of my listening position.

@rauliruegas , An L shaped room makes things a bit more complicated on the sim domain. Talk to an integrator. It is hard to write technical essays on a thread. Nevertheless, the harman room mode calc will still work between any 2 parallel walls in that room.

Google harman room mode calculator. You would enter your room dimensions to determine where the hell all the strongest nulls/peaks are. The results would look like this....

 

Here’s another way to visualize it....(top view, scratch rough sketch)....Also how you deal with nulls and peaks. Goofy bass is all a guy hears unless he does stuff like this. (Basic Physics - Standing waves/nulls/peaks occur between parallel walls). This again shows you the advantage of larger rooms. The smaller the room, the harder it gets to deal with this.

 

Here’s some expansion on what i was trying to describe with the Harman virtual sub principles. By strategic placement of subs, you can get rid of many of the strongest peaks/nulls upto the sub’s crossover frequency. For nulls/peaks occurring at frequencies higher than the sub’s crossover, you have no other choice but absorption.

In short, you can use subwoofers to REMOVE nulls/peaks. It is not just for giving some oomph on the low end for a flaccid speaker.

 

 

If you had 4 subs, this is how you would place them and phase adjust them to get rid of the maximum number of the strong nulls/peaks in light of the above mentioned principle (up to the sub’s crossover point).

sub 1: 1/4 lengthwise, 1/4 widthwise position

sub 2: 1/4 lengthwise, 3/4 widthwise position

sub 3: 3/4 lengthwise, 1/4 widthwise position

sub 4: 3/4 lengthwise, 3/4 widthwise position.

 

If you only have 2 subs,

sub 1: 1/4 lengthwise, 1/4 widthwise position

sub 2: 3/4 lengthwise, 3/4 widthwise position.

 

Same principle works for the room’s heightwise modes. You ever heard of guys lifting subwoofers off the floor to the heightwise modal points? That is the reason and the physics behind it.

The idea is to tackle the max number of strong nulls/peaks with sub placement...and then use absorption to deal with the rest (modal nulls/peaks/frequencies higher than the sub’s crossover). It is also a very very good idea to get subwoofers with a variable phase knob (not just a 0/180 phase switch). Rythmik is a good example of subwoofer brands that give you a variable phase knob.

 

Everything else should be diffusion so you don’t kill the room with absorption all over the place. Focus only on the main listening position.

Hope that helps you...and some of the other confused guys here...

 

 

 

 

Dear @deep_333 : I really appreciated your post and you can be sure that I will do all those.

Tou touched a critical issue in the subs correct integration to the room/speakers: PHASE that almost no one really speaks about when are talking of subs and " playing "/changing with comes with very high rewards that for me were unexpected to say the least.

 

By coincidence and before read your post last nigth I was " playing " with subs Phase making some changes ( btw, we modified the phase control in the HGS to go from only two phase positions to almost continuous changes. My HGS have several modifications made it by a friend and me: I changed the stock internal wiring from the drivers to the amp for pure silver KK cable, I by-passed all the internal fuses and changes passive and active parts in the input board and internal crossover circuit board. Even I change the damping foam by long hair virgen wool. The subs are at around 20 cm. from the floor and have a dead weigth of 30kg at the top plate. ) and I did it using CD MUSIC source as " Day after Tomorrow " that at its very first track comes with deep bass made/using synthesisers and I use other film soundtracks as Gladiator and the like and late in the nigth I gone to sleep but not totally satisfied.

So, I wake up early today and followed playing with phase changes this time doing with LPs mainly using the Telarc 1812 that has a wide kind of different bass frequency ranges and recorded with acoustic instruments and not synthesiser that’s different and after the changes with the phase finally I was truly satisfied with and learned the critical importance of PHASE about.

Thank’s for your knowledge advise. I’m just learning what it’s exiciting to me in that critical sub/speaker subject. Thank’s again.

 

R.

Another advantage in my sub/speaker is that the sub driver is of pulp/paper cone as are the ADS speaker woofers drivers, so exist synergy in the sound reproduction.

 

R.