My experience adding subwoofers to 2 channel

Noble100 - re: debra / swarm system - phase changes. I have found reasons to not always follow Audiokinesis advice "mechanically" - it depends on your room and a bit on your listening tastes also. So I’ve now found that my main Dream Maker speakers - to my ears, in my room - sound better crossed a bit behind me, not in front of me like Audiokinesis advices. In other words, a more conventional speaker setup with less toe-in. This may apply to my use of the LCS effect speakers also. Not sure yet. Based on Audiokinesis philosophy the idea is to spread the reverberant sound around and "decorrelate" it as much as possible. Based on advice from James Romeyn at Audiokinesis, I run the effect speakers so that one channel phase (polarity) is shifted. And some other mods that I am not sure about. The great thing with the Swarm and Debra system - and the Dream Maker / LCS system I have - is that it is very much up to the user. Position the speakers right, in the room, adjust phase / polarity, and the reward will be there.

Hello o_holter,

     James Romeyn at Audio Kinesis is the guy who convinced me to give the AK Debra 4-sub DBA system a 28-day free home trial.  I started off a big skeptic but, after hearing the bass response in my room and system, I'm now probably one of their biggest proponents.  By a wide margin the best bass I've ever experienced in my room and the integration with my large Magnepan panels is absolutely seamless.
     I followed the Audio Kinesis Debra sub positioning procedure exactly and it turned out very well.  However, their advice was to sequentially reverse the polarity on a sub at a time to determine if it improves overall system bass performance.   After spending half a day setting up my DBA system I was a bit tired and wanted to listen to it.  I figured I'd get to that step when I could. But that was over 4 years ago and my subs still sound great running in-phase, so I now consider this phase reversal step to be optional.

Tim

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