Dual Subwoofer Placement

Hello DB,

     Back at it again?  Good.  I'd suggest that as long as you have 4 subs active in your room (the 2 HGS-15 and 2  HGS-10), and they are properly positioned in a distributed bass array configuration, then you will certainly attain excellent bass performance for both music and HT throughout your entire room.  
     For best results, you should position each sub sequentially around the perimeter of your room using either mics and frequency spectrum analysis software tools or using the crawl method.  Both are very effective and you can always run your room correction processing afterward, to see if the bass, in your opinion, is even further improved or sounds better without it.  It's completely your choice how you distribute the 2 larger and 2 smaller subs throughout your room.  The essential factor is that  4 subs are launching bass soundwaves into the room from independent, and typically asymmetric, positions in the room.  This 4-sub distributed bass array (DBA) concept has been both scientifically and anecdotally proven to be tremendously effective in virtually any room and with any pair of main speakers.   
     If you utilize the crawl method of sub positioning, begin the search for the optimum position of sub#1 in the right front corner of your room, begin by positioning the 2 HGS-15s as sub#1 and #2 and continue to progress counter-clockwise around the perimeter of your room for positioning the 2 HGS-10s as sub#3 and #4, I believe this will result in both larger HGS-15s being optimally positioned along your front wall and the 2 smaller HGS-10s being optimally positioned elsewhere, likely in a well separated and distributed configuration.
     I located my 4 identical subs sequentially around my 23'x16'x8' room using the crawl method.  The optimum positioning turned out to be 2 along my front 16' wall, about 2' away from each corner, and 1 along each 23' side wall, toward the rear of the room and also with each about 2' away from each rear corner.  I'm thinking your 4 subs may be optimally positioned similarly, but likely not identically, in your room.
     I'm willing to continue to assist you, pm me if you'd like.

Later,
 Tim

Would it be preferable to use the subs 3 & 3 or 4 & 2?

You lost me. Do not understand why different setups. Sound is sound, and the best is the best, movies or music. What is 3&3? What is 4 & 2? Besides 6 I mean.

jimmy225: "To those asking about my setup, I will be setting up two Martin Logan 1100X subwoofers with a pair of Martin Logan ESL 9’s. I’m estimating my crossover will be around 60-80Hz. I have about 10’ from where the speakers and subwoofers will be placed to the listening position (longer if I measured at the actual angle from the placement to the seats). The room is approximately 30’ wide."

Hello jimmy,

     Sorry, dbphd kind of sidetracked the thread temporarily.

     You seem to have a rather large room, based on your prior statement that it’s 30’ wide. If your room’s length is even half its width and you’re goal is to attain near state of the art bass response not only at your listening seat but throughout your entire room, I am certain that a custom 4-sub DBA system would be your best option/solution. If you’re goal is only or mainly to attain very good bass response at your listening seat, I’m fairly certain that your current two ML 1100X subs will be adequate if both are properly positioned in your room in relation to your listening seat.
     Before you decide whether to use dual or quad subs in your room and system, however, I think it’s important you understand that quad subs will definitely provide significantly higher bass quality performance than dual subs are capable of providing. Yes, this is my opinion based on my own results of using both dual and quad subs in my 23’x16’x8’ room and large Magnepan 2.7QR and 3.7i main speakers.
     But my opinion is also based on many hours of research on the subject of attaining very good bass performance in domestic sized rooms, which include scientific White Papers as well as professional reviews on quad sub systems such as this review by The Absolute Sound on the Audio Kinesis Swarm 4-sub DBA system linked to below:

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

     I actually purchased the very similar and identically priced Audio Kinesis Debra 4-sub DBA system about 4 years ago on a 30-day free in-home trial basis. The above review served as another major impetus for me to give the 4-sub DBA concept an in-home audition.
     With the help of a buddy, we were able to set the entire bass system up, including running all connecting wiring under my room in a crawl space, by about 4pm on a Saturday afternoon. Within an hour of listening to music and HT, there was absolutely no doubt in my mind I was going to keep it. I also discovered the Absolute Sound review, that I linked to above, is an extremely accurate description of what to expect from a 4-sub DBA system.
Based on my experience beginning with upgrading from a single sub to the use of 2 optimally positioned subs, the bass will become more powerful, more dynamic and have a seemingly effortless quality due mainly to the fact that there are 2 subs sharing bass duties with neither operating anywhere near its limits.
     Upgrading from a single sub to the use of 2 optimally positioned subs, the bass will also noticeably become smoother, faster, more detailed. better integrated with the main speakers and the soundstage will become wider, deeper and more open. This is mainly due to physics and the fact that there are 2 separate, independent and optimally positioned subs, in relation to the listening seat, launching bass soundwaves into the room. This is true even if both subs are operated in mono configuration for reasons I explained in a previous post.
     Upgrading from dual subs to a 4-sub DBA system provides even further improvements in all the bass performance qualities I already described in upgrading from a single to dual subs but with the added benefit of providing near state of the art bass performance quality throughout your entire room, not just at your listening seat.
     I suggest you take your time, learn more about the physics and psychoacoustics involved with utilizing multiple subs in a domestic home audio/video room and seek out a local audition of a 4-sub DBA system if possible. I don’t know where you live but I live in a suburb just north of Indianapolis. You’re more than welcome, if you live nearby or are ever in the area, to stop by my home for a demonstration.
     Whether you ultimately decide to utilize dual or quad subs in your system, however, I’m willing to assist you in optimizing either configuration.

Best wishes,
     Tim

WOW! I really appreciate the detailed response. Unfortunately, I live in an apartment and don't have the space to go with four subs, my neighbors will already hate me having two. I was in the process of getting a house, and then setting up my equipment, but that has since gone out the window and now I'm trying to make the best out of a bad situation. Not having the correct spacing for everything definitely makes it a little difficult but, if done correctly, I think I can still turn the space I do have into a solid listening stage, thus why I am asking for experienced feedback while trying to plan out my own layout. Again, thank you for taking the time to offer your advice.

Hello jimmy225,

     Okay, you want to keep it at 2 subs for now.  That's fine, the most important thing to do is position each sub sequentially in the optimum spot, in relation to your listening position,  along the perimeter walls of your room.  Please don't expect these positions to be just one next to each main speaker with the drivers pointed directly at your listening seat.
     I can describe exactly how to do this but, before I do, I need the width, length and ceiling height of your room along with a description of what's currently  along the room's perimeter (couch, chair, windows, system equipment rack, speakers, subs, tv, doors, openings and their approximate dimensions). 

Thanks,
  Tim