My experience adding subwoofers to 2 channel

Hi Tim
Optional - exactly. I have followed Romeyn’s advice in my own LCS setup, and 95 percent of it was extremely helpful and good. But at some point, it becomes a matter of individual room integration and also listener preference. I do use phase reversal with one of the LCS speakers, it sounds a bit better than correct phase, but I should probably test this again now that I have changed the toe-in of the main Dream Maker speakers. This is, again, an "optional" issue, to my ears. Some like it when they cross in front, some - like me - prefer a more conventional toe-in where they cross behind me. I mailed Jim Smith (author of Get better sound) about this, since in this book, crossing in front is not recommended, it harms the tonality or harmonics. But he wrote back: It is a matter of preference.

Tim, how do you toe-in the Magnepans? Do the speaker axes cross in front of you, at your position, or behind you? I think this matters, also in terms of sub integration. To get my former system time-coherent I had to place the Velodyne DD18 a bit in front of the main speakers, if I remember right. Not a good thing, in our living / listening room. Your Debra system seems much more flexible. Happy to hear it works so well. Maybe I could complete my system with half of it - two subs. Although I have neighbours who complain with too much bass. 

Hello o_holter,

    My room is 23'x16' with an 8' ceiling. I have some pictures posted on my profile if you want to take a look. It's a combo music and ht system.
    I have a 65" hdtv wall mounted to the middle of the front 16' wall with my Magnepans straddling the tv,they're about 8' apart and 3-4' out from the front wall. My listening seat is in the middle of the rear 16' wall. The Magnepans are slightly toed-in and their axis cross at my position.

    For serious music listening sessions, I usually move the Magnepans about 5-6' out from the front wall and with no toe-in. I then move my listening seat exactly between them and about 3-6' away from the midpoint between them.   I find this positioning allows for an amazingly
three dimensional soundstage illusion on good recordings that is wide, deep, detailed, solid, stable and realistic.  
    You stated: "To get my former system time-coherent I had to place the Velodyne DD18 a bit in front of the main speakers, if I remember right. Not a good thing, in our living / listening room. Your Debra system seems much more flexible. Happy to hear it works so well. Maybe I could complete my system with half of it - two subs. Although I have neighbours who complain with too much bass."

    It makes sense to emphasize the importance of time-coherence of midrange and treble tone frequencies, that is that midrange and treble soundwaves reach the listener at about the same time since these frequencies have soundwaves that are relatively short in length, measured in inches.  It makes little sense to include deep bass tone frequencies in this emphasis on the importance of time-coherence, along with midrange and treble tone frequencies, since bass frequencies have soundwaves that are very long, measured in feet.  A 20 Hz soundwave is 56 feet long, a 30 Hz is 38 feet long and a 40 Hz soundwave is 28 feet long.   Expecting time-coherence of bass, midrange and treble tone frequencies, that is that bass, midrange and treble soundwaves reach the listener at about the same time makes little sense.
     Here's a quote from Duke Lejeune, Audio Kinesis owner and maker of the Swarm bass system:  
"Another factor is that it takes the ear a fair amount of time to hear bass frequencies. The ear cannot even detect the presence of bass energy from less than one full cycle, and it takes several cycles to detect the pitch. So considering the wavelengths and room dimensions, by the time we can hear bass tones the room’s effect is in full swing. Perceptually, in our home listening rooms there is no such thing as “direct sound” in the bass region; by the time we even begin to hear it, it’s all reverberant sound."
     So, moving a sub in front of the main speakers likely makes little to no difference in the perception of bass response performance in a normal sized room.
     I believe 2 subs will begin to provide smoother bass response, roughly twice as smooth as a single sub, but that 4 subs will be roughly twice as smooth as 2 subs.


Tim 

Hi Tim
Nice system - and interesting that we share some of the same experience, listening a bit more nearfield, for the best 3d immersive experience.
Bass and time coherence - I am no expert, just reporting what I heard. I first tried down-firing subs and next came to prefer front-firing ones. First, two Rel subs, didn’t get them to match the system, so next, one big Velodyne. I noticed better sound by positioning the subs precisely in relation to the woofers on the main speakers. But maybe it was room alignment more than time alignment. I did not use REW or other software, but mainly my ears. My audiophile imagination jumped to the idea that time does in fact influence the result. I very much agree with the idea that a main purpose of the sub(s) is to get the room ’in full swing’, smoothness, lack of boom etc. Still I wonder if distance to the subs plays a role also. Even if mainly indirectly / reverberant.Through the room, so to speak.

Hello holter,

     I'm certainly no bass expert, either.  James Romeyn mentioned to me how well his A K Debra system and its distributed bass array concept works and I just read all I could find out about the concept, mostly research done by Earl Geddes, Floyd Tool, Duke Lejeune and Todd Welti.  
     I learned a lot, its psychoacoustics basis made a lot of sense and James Romeyn's offer to let me try it out free in my room for a month convinced me to give it a try.  I can't overstate how well the Debra/Swarm system works with my main speakers on music and ht.
    You have a fairly large room at 20'x27', are already using A K main speakers and seem like an ideal candidate for a DBA system.  I think you'll be amazed by the results.  I'd suggest calling James Romeyn and see if he'll give you a 28-day in home trial period.  I guarantee you won't be returning it.

   Tim