Separate subs for music and HT/surround


My stereo setup is comprised of Ayre 5/20 series digital hub, preamp and amp that drive KEF Ref 1s through a passive Marchand high-pass filter. For HT and surround, LR side and rear surround from an SP3 go to NAD Class D amps that drive LS50s. The SP3 receives HDMI from an Ayre DX-5 DSD, and its front LR output goes to a balanced by-pass input of the KX-5/20. I have two Velodyne SMS-1 bass managers that provide acoustic room correction, two HGS-10 subs, and two HGS-15 subs.

Question: Should I use one SMS-1 with the two HGS-10s for stereo and the other SMS-1 with the two HGS-15s for HT and surround music? I realize there are advocates for using 4 subs, and I could daisy-chain the SMS-1s, but separating the SMS-1s seems a neat way to keep stereo separate from HT.

db
Ag insider logo xs@2xdbphd
Hello DB,
     Wow, you've been busy, too.  Why the heck do your Velodynes keep going on the fritz?
     You may be better off performance and cost wise by just selling your Velodynes to your Baldwin Hills repair guy and buying an Audio Kinesis 4-sub DBA system for about $3K.  It'd be easier to move the subs around at 44 lbs each and the included 1K watt class AB amp/control unit would be more convenient since you'd be able to set the optimum volume, crossover frequency and phase on all 4 subs once as a group rather than individually as I think you do now.
     I'm currently finalizing a plan for treating my entire room with GIK room treatment products and buying apre-owned Levinson 326S preamp and pair of Magnepan 3.7i speakers.

Later,
 
Tim,

I’m using my 205 in the living room with an Audio Engine until i get the Marantz Model 18 serviced. An Ayre A7e & Codex for Roon also reside in that room.

The Velodyne HGS-15 that was not serviced seems has developed a barely audible low frequency hum and the HGS-10 an occasional chugging. But 4th order low-passing the KEF Reference 1s at 40 Hz to the two remaining subs sounds very good to me.

For HT I’m using a Bryston SP3 to NAD 22 and 238s with six LS50s.

I’ve been occupied with a tube-analog setup using a Thorens TD 124 with SME III arm and Ortofon 30H cartridge as source through an Audible Illusions Modulus 3 to Cary CD 572 SE monoblocks. The speakers will be the Reference 1s or stacked Reference 102.2s wired in series. The Ref 1s would have to be switched between the Ayre amp and the Carys, but the 102.2s could be dedicated if I can find room for them.

db

Hello kgveteran,

     I don't know what millercarbon has against "horrid sounding HT" but, I know that with 1 to 4 subs optimally positioned in a room, HT does not sound horrid at all and works equally well for HT and music.  I know this because I've been doing and listening to both HT and 2-ch music with a 4-sub DBA for over 5 years now.  
     I also wanted to let dbphd know that I recently bought an Oppo 205 for a reasonable to me premium of $2,100 and won't be needing his.  
     I haven't been following this thread as closely as I was earlier and was wondering how dbphd was doing with his system.  Hopefully, he'll post again soon to let us know.
     On a side note, I've been busy lately upgrading my own system from 1080p to 4K.  I bought an Oppo 205 to replace my 105 and ordered a 4K LG C9 77" OLED hdtv to replace my Panasonic 1080p 65" plasma.  I'm also having a local hi-end retailer treat my room fully as soon as I receive my order of required room treatments from GIK. This should be interesting and educational.
     I'm also looking forward to watching that Over Lord disc you posted about.

Thanks,
 Tim
Post removed 
Hello DB,

     Happy Thanksgiving!  

     I'm disappointed, you're not even going to give the 4-sub DBA concept a try?  Please trust me, you'll be amazed if you give it a try on music or HT.  I certainly was.  C'mon, be adventurous.

Tim
Tim,

I think we are expected for Thanksgiving at out cousins in the Hollywood Hills.  We may make a two day trip of it and drop off the subs in LA the day before.  When we have four working subs, I'll try them with the stereo setup.
Hello DB,

Yes, I remember now you’ve never had 4 working subs in one room. I’d just like you to at least experience the near state of the art bass quality attainable in your room by utilizing all 4 subs in a properly positioned 4-sub DBA.
My opinion is that there’s a higher degree of elegance in a single system that’s capable of high quality performance for both stereo music and HT, especially if it incorporates a 4-sub DBA producing very high quality bass for both, because it requires more thoughtful design and will offer superior bass and overall performance on both.
I think it’d be a shame not to even try out the 4-sub DBA concept on either music or HT in your room because you have all the necessary component parts, once both subs are repaired, and I sincerely believe you’ll be amazed by the bass seamless integration with your main speakers as well as the extremely high bass quality. You'll probably have both subs repaired in any case, right?

Tim
Tim,

I've never had four working subs in one room.  Previously the HGS-10s were downstairs, the HGS-15s upstairs.  Since moving them all upstairs, two at any given time have needed repair.  Another dreaded trip to LA is required to have four functional subs in any configuration.  Notice I wrote "current plan" and my thinking is in a state of flux, but the elegance of separate stereo and HT setups is appealing to me.

db 
dbphd:
"Tim won't like this, but my current plan is a stereo setup comprised of Ayre Series 5X Twenty components and KEF Ref 1s, and a surround/HT setup comprised of an Oppo 205, NAD M22, and a pair if NAD 268s with six LS50s.  Current thinking is to use the Velodyne HGS-15s for stereo, the HGS-10s for surround, but that could be reversed.  An Audible Illusions Modulus 3 might be used with the Thorens TD 124 in the stereo setup, making Roon, discs, and vinyl sources for stereo.  HDMI from the disc players would be for video only."

Hello again DB,

     I'm not upset, it just makes me think of that old saying: "You can lead a man to a DBA, but you can't make him use and enjoy it".  Besides, it's really your loss if you decide not to deploy all 4 of your subs in a DBA for both music and HT.  
     Perhaps you just have some rare psychological or medical condition that causes an irrational aversion to near state of the art bass response.  Sota Bass Phobia?  Less Than Optimum Bass Conundrum?  Compromised Bottom Syndrome? 


Tim      
 
OP here.  As noted in my 11/2 post I've settled on separate stereo and HT setups, each with a pair of subs.  Both setups reside in a single rack, but do not share any cabling.

db
As i said, agree to disagree....

as to the OP, i have always had best performance running all subs from a single LFE output, most times running my subs hot for HT and backing off the SPL for music.

kgveteran,

     I think we should be respectful of the OP and thread readers by ending this crawl method sidetrack and returning to the original post topic.  
     But, just for your entertainment, I wanted to let you know that I've been using the crawl method successfully since I moved out from underneath that proverbial rock.

You're welcome,
      Tim
Hello kgveteran,

    ?...Wtf... ? You've chosen to be a cowardly baby chicken?

Tim
Calling a $65 mic expensive, when discussing subwoofer systems costing thousands is plain silly.

no need to discuss what we do for a living since its pointless, and im sure you throw around what you do wherever and whenever Lol, no one really cares.

i suggest to new subwoofer Owners to do some reading on subwoofer placement, and further do some research on affordable microphones and free software. There are a lot of really good threads in other forums which take the scientific method of subwoofer placement, delay, gain settings, DSP ,So they can get all that good money they spent on the subwoofers to really pay out at the listening position.

Tim, have fun crawling, but in a world full of great methods and scientifically accurate procedures with results proving all i have stated, you Sir do nothing to progress, which is why you offer the methods you speak of. My guess its only because you just dont know your way around laptops and software, i do understand your plight 

Tim won't like this, but my current plan is a stereo setup comprised of Ayre Series 5X Twenty components and KEF Ref 1s, and a surround/HT setup comprised of an Oppo 205, NAD M22, and a pair if NAD 268s with six LS50s.  Current thinking is to use the Velodyne HGS-15s for stereo, the HGS-10s for surround, but that could be reversed.  An Audible Illusions Modulus 3 might be used with the Thorens TD 124 in the stereo setup, making Roon, discs, and vinyl sources for stereo.  HDMI from the disc players would be for video only.

db 
Hey Ozzy,

      You know what they say: 2 subs perform twice as well as 1, 4 subs perform twice as well as 2 and 8 subs are good grounds for a divorce. 
     I'm just using the four Audio  Kinesis Debra subs, 1'x1'x2' with 10" drivers, and I'm getting near sota bass performance in my room for both music and HT.  The only way I can even imagine the bass being improved is by using four JL F-113s


Enjoy,
 Tim
nobel100,

2 of the F-113's are used as Masters and 2 as slaves. 2 are V2 and 2 are V1. I purchased them individually until I accumulated the 4.

With Hometheater I am still using the JL Audio subs (via HT pass through on my Ayre Preamp). The Denon receiver adds another 4 other subs, M& K Sunfire, Outlaw Audio for a total of 8 subs.

ozzy
Hello Ozzy,

     I didn't realize you're a 4-sub distributed bass array concept adherent on your 2-ch music system.  It seems like you  decided to try the 4-sub DBA concept out with a vengeance; employing four $4,000 JL F-113 very high quality subs in one's 2-ch music system not only represents the most impressive example of any custom 4-sub DBA system I'm currently aware of, it's also extremely cool. 
     Congrats!  I'm very interested in how you learned of the 4-sub DBA concept,  what convinced you to give it a try, why you decided to use such high quality/expensive subs, how much of a discount you got buying the 4 JLs and your overall DBA performance impressions in your room.  
     Oh yeah, I disagree with your comment about the quality of subs being more important on music than HT.  I believe using higher quality subs on both are easily discernable and improve performance.  I think you and most would likely agree with me if they swapped out lesser subs for JL F-113s in their music or HT systems.

Thanks,
 Tim
I thought I had posted to this thread but I can’t find it.
So here goes my take on the subject.
With my 2 channel I use 4 JL Audio F-113 subs. With my home theater equipment it adds 4 more subs of various quality.

Yes, I believe with 2 channel audio the quality of the sub (s) matter. But with home theater you just need subs that can do deep for crashes, explosives and such.

ozzy
Hello kgveteran,

     ?...Wtf... ?  You've chosen to be a cowardly baby chicken?

Tim

    Oh Tim......you didnt......a surgeon......ur gross......i find this pathetic......i have to bow out of this exchange.
Hello millercarbon,

     Okay, thanks for elaborating and clearing things up.  I didn't realize you were referring to music being played back via a 2-ch system compared to a multi-ch system. I was perceiving your comments more in the context of how I utilize my own combination system, using 2-ch exclusively for music playback and using multi-ch exclusively for HT playback.
      I completely agree with you that, when comparing music played back on 2-ch vs multi-ch systems, by far the most important factor when it comes to being believable is quality and it matters far more than the number of channels. More channels in this case is not necessarily better.
      I know many have built and enjoy high quality multi-ch music playback systems. While I readily admit that I currently have no experience or desire in doing so, I still suspect I'd be highly impressed by the sound quality of many multi-ch music systems others have built.
      Reconsidering your comments in this context, however, I believe you're actually commenting more on the importance of quality in general rather than the superiority of 2-ch or multi-ch as a quality playback method more specifically.  
     I definitely agree with you on the importance of quality but also know it's possible to combine both in one system with shared components and speakers; a high quality 2-ch system for music playback and a high quality multi-ch system (up to a 9.1 with Atmos) for HT playback. I think we're both in agreement on this.

Tim
 Okay listen first off its not gonna sound like it but I totally get it. People with HT setups love their HT setups in spite of the horrid sound. Or maybe even because of the horrid sound. I get that. Do not understand why anyone would want to waste their money on horrid sound but they do and so I totally get that.


Thought I would clear things up and expand on this, being the guy who wrote it and all.

Its not satirical, and only a little over the top, which I love, for trigger value if nothing else. 

First off, not talking about the 0.01% of cinemaphiles who really do want to watch movies with the best sound they can get. If that is what I meant to say then that is what I would have said. Instead I said, "People with HT setups love their HT setups" the emphasis being on "HT setups" and NOT getting the best sound.

This to me is the whole problem in a nutshell. The whole HT industry has pushed their multi-channel approach from THX on down to where people are totally brainwashed to the point they seem to think watching movies with less than 7 channels isn't even watching movies. So much so that when it comes to HT they aren't even capable of giving serious consideration to the patently obvious fact that two speakers are perfectly capable of better performance than 4 or 5 or 7 or even 7.1.

Think about it. Multi-channel is so horrid, to stick with the original term, it was abandoned for serious music not years ago but decades ago. Why? Many reasons, but by far the most important is that when it comes to being believable quality matters far more than quantity. More in this case is not better.

Anyone seriously into this, especially if shopping for HT, should do what I did. Go and listen. Compare. What you will find, without exception and without a doubt, nothing multi-channel sounds anywhere near as good as stereo, at least not without spending many times as much money. Which is bad enough. But worse, above a certain threshold, which is reached a whole lot sooner than you might think, no amount of money will get you surround anywhere near as good as stereo. 

Just to beat this dead horse to pulp, take any $5000 A/V component you can find, new or used, don't care. Best one you can find. Hook it up and compare side by side with any $5k integrated amp. Any. Worst one you can find, brand new, whatever. Does not matter. Won't even be close. Compared side by side with stereo the HT component will sound.... not even close. Horrid.

And yet a lot of HT people love their demonstrably horrid sounding HT systems. Listen to what they say- because stereo is missing surround. They love the extra channels. That create the horrid sound. Therefore, logically, they literally do love their HT setups because of the horrid sound.

Its not satirical at all. Its actually a pretty straightforward conclusion.
Hello kgveteran,

Being a surgeon for over 40 years, I have developed a deep appreciation for accuracy, detail and precision. I’ve always strived to utilize the optimum instrument for every procedure, acutely realizing that utilizing the optimum instrument has the possible consequences of literally life or death.
In my 50 years of building and configuring my personal home audio/video systems, however, I’ve discovered that failing to utilize the optimum instruments in configuring and positioning my system transducers has possible consequences that are significantly less dire.
The truth is that there are at least two methods of optimally locating subs that individuals can utilize, the free crawl method I mentioned and the more expensive and technical method you mentioned.
Just as the Joker suggested to the Thief, there’s no reason for us to get excited, right?  Individuals are rightly free to utilize either method or try both and adopt the configuration they perceive as best. Based on my experience, I can predict with confidence that the resulting sub room positions of the subs, no matter how many subs positioned, will not be significantly different and, more likely, will be remarkably similar.
Can we agree on this?

Timmie

Timmie,
Keep Crawlin brother :0)

Cheers and best to you

KG

  ps: i understand your fear in not really being able to operate test equipment, you’ll get it if you really try, the investment will pay off in. Good luck Timmie, you add a lot of useful advice here !
kgveteran: " Tim,
            We will agree to disagree, cheers mate !"

Hello cagey veteran,
     
     How about we agree that the crawl method, even after 6,000 years of continuous successful usage, continues to be an excellent tool for optimally positioning subs in any room and it's free? You're always free to use your expensive measuring equipment to validate optimum sub positioning if you'd like.

Cheers to you, mate!
         Tim
Hello dbphd,

     I've missed talking with you!  I think you forgot the basic truth about deploying subs in any given room:
Two subs perform twice as well as one, 4 subs perform twice as well as two and eight subs are valid grounds for divorce. 
     I know you realize that, unfortunately, the best course of action is to repair both non-functioning subs.  The spectacular bass results of a 4-sub DBA system can only be realized with four functioning subs and non working subs have almost zero dollar value since they're of no use to almost everyone.
     What repairs were done on the first subs you had repaired?  The sooner you have them repaired, the sooner you'll be enjoying world-class bass performance on both music and HT.

Later,
  Tim  
Tim,

As luck would have it, the Velodyne HGS-15 and HGS-10 that were not recently repaired have now developed problems.  So I'm using a single HGS-15 with 4th order crossover at 40 Hz.  I think the sound is quite good: bass in jazz is free of boom while organ pedal notes are well portrayed.  I'll try adding the repaired HGS-10 later today for a two sub setup, albeit a very asymmetrical one.

db  
kgveteran: " a comprehensive multiple subwoofer array setup scheme combined with proper calibration equipment will get you much closer than archaic “crawl” method."

Hello kgveteran,

I think we both owe a big thank you to m-db for informing us that even a manufacturer of subs containing room correction hardware and software realizes the effectiveness of the timeless ’crawl method’. Thank you m-db.
Sure, individuals are free to buy and utilize expensive calibration equipment and software to determine the optimum positioning of subs in a multiple sub bass system. But the crawl method has proven its effectiveness since ancient times when the Greeks first invented the technique circa 3480 B.C. Aristotle and Plato actually put it best when they stated numerous times in oral and written form, " why bother? Crawles fideles!".
The reason the crawl method has since been used continuously for approaching the last 6,000 years is because it works so well. A bit more recently in this country, it’s a well known historical fact that Thomas Jefferson was observed teaching the method to George Washington in the upstairs living quarters of the White House when George was setting up his system just after his Inauguration. Interestingly, it is recorded that they did so while dining on beer and pizza. Also of note, Jefferson was introduced to the magical secrets of the crawl method by Benjamin Franklin at a clandestine Freemason meeting just years earlier in Philadelphia.
Given its long, proud and extremely effective history spanning centuries, I consider your attempt to abandon, or at least foreshorten the effective lifespan, of such a beloved, archaic and globally respected sub locating tool as the crawl method to be reprehensible, heretical, counter-productive, nonsensical and possibly criminal in most legal jurisdictions world-wide. My god man, Leonardo Da Vinci used the crawl method in establishing his controversial, and humankind’s first, 4-sub DBA system over 500 years ago.
I fail to comprehend your logic in casting aspersions and apparent lack of respect for a literally free technique, that has been so cherished, reliable and effective throughout the long and historic record of sub locating efforts, solely on the basis of not being sufficiently technologically sophisticated enough for your approval.
Well, we now clearly understand you’re not a Freemason.

Tim

   The SVS Ultra appears to be the first affordable subwoofer with an application that offers needed low frequency crossover related adjustments as well as three customizable memory EQ presets within a single frequency band between 20 and 200Hz.
   Velodyne, JL Audio, Vandersteen, Magico, and Von Schweikert, understand the importance of multiple frequency bands of discreet equalization within a higher crossover region without reducing gain and not simply a set point where the subs kick in.
   SVS claims (SB16-Ultra Owners Manual page 15), "in some cases, reversing polarity - can be used to fix bass nulls or overly boomy spots in the listening area". While it may have a minor affect reversing polarity simply restores the polarity of the recording which is most noticeable in the bass drum and can vary as often as from track to track. If the listening position is located within a null or mode the sub will require proper physical relocation. With the sub at the listening position you don't actually need to crawl around to locate a rooms modes.  
   I'd venture subwoofer sales are related to affordability rather than flexible frequency integration. If they've never heard it how would they know what to listen for? After all, almost any sub sounds better than no sub.
No wonder SVS is climbing toward the top in subwoofer sales, design, R&D

if i read SVS recommends crawling around rather than a $60 mic and free software and a lsptop, i’ll throw in the towel Lol

Actually, on page 25 of the Velodyne Digital Drive Plus User’s Manual under the heading of Optimize for Subwoofer Placement, "you place in the room according to the information in the general section and optionally the "Crawl Test" section in the Subwoofer Placement Recommendation Guide" (where the "Crawl Test" is explained in more detail).
As a multiple DD Plus user I can confirm that DD Plus Room Optimization can compensate for time and phase issues that may arise from less than optimal positioning. Its ability in dealing with any rooms unique modes and nulls is far less effective, if at all, compared to beginning with the suggested "Crawl Test".
Sadly, the Velodyne facility is now used for Velodyne LiDAR.
OmniMic or REW are more accurate Measuring devices. Promoting anything other than measuring with instruments is misguided advice. 
While multiple subwoofers are accurate advice, and provides enduser with a smoother response at the LP, this is 2019 and we have software and hardware that are affordable and accurate.

a comprehensive multiple subwoofer array setup scheme combined with proper calibration equipment will get you much closer than archaic “crawl” method.

If crawling around was a conclusive method, Kef and Velodyne would scrap their testing facility and hire professional “Crawlers” :0)

Kg



     Just as I suspected, you had no legitimate purpose or reason for including and misconstruing millercarbon's prior post.  Thanks for confirming this.

Tim
" Okay listen first off its not gonna sound like it but I totally get it. People with HT setups love their HT setups in spite of the horrid sound. Or maybe even because of the horrid sound. I get that. Do not understand why anyone would want to waste their money on horrid sound but they do and so I totally get that."

Hello kgveteran,

     Just wondering why you quoted the above comments from an earlier post by millercarbon?
     I believe millercarbon intended these comments satirically and was referring to lower quality and more generic sub installations, not dbphd’s higher quality installation. I believe this because I know that millercarbon is very well versed on the theory and excellent bass performance levels obtainable through a properly positioned and configured 4-sub distributed bass array (DBA) system, having recently built four subs and deploying them in a custom DBA system in his system and room.
     He has first hand and extensive experience, as I do, listening to a 4-sub DBA systems in our own rooms. We’re both very familiar with the near state of the art bass response performance these systems produce for both music and HT.
     Exactly which "horrid sounding HT system" are you referring to and why'd you feel the need to repost millercarbon's comments?

Thanks,
Tim
Okay listen first off its not gonna sound like it but I totally get it. People with HT setups love their HT setups in spite of the horrid sound. Or maybe even because of the horrid sound. I get that. Do not understand why anyone would want to waste their money on horrid sound but they do and so I totally get that.

I was watching Over Lord last night, if anyone wants a demo scene on their Horrid sounding HT :0) , this is the ticket,the first 15min is a roller coaster.
 
And that was the 5.1 version on PrimeVideo upmix to DolbyD+DDS, I immediately ordered the 4K Atmos disc
Hello DB,

     Okay, I understand. 
     If you like the looks and sound of a HGS-10 aside each KEF Ref 1, I'd suggest you try positioning your two HGS-15s in the following manner:

     Leave both of your 10s exactly where they are aside each main speaker.  You already know these sub positions result in very good integration with your main speakers which is virtually the same as utilizing the crawl method to locate them.  I suggest you just consider their current positions are the optimum positions for your sub#1 and sub#2 in the 4-sub distributed bass array (DBA) system you're creating and just proceed to optimally locate your two 15s, as sub#3 and sub#4, in your room. 
     To do this, just do the following:

1.  Hook up one of your 15s and place it at your listening position.
2.  Play some of your jazz with good repetitive bass through the 15 and your two 10s.
3.  Use the crawl method, starting at the left side of sub#2 (located aside your left channel main speaker) and continue walking counter-clockwise around the perimeter of your room until you determine the exact spot that the bass sounds best to you (best integrated and the most natural). 
4.  Position sub#3 at this exact spot.
5.  Hook up your other 15,place it at your listening position and repeat steps #2-4 to optimally locate it.
6.  Once completed, sit at your listening position, play the same music with all four subs playing and verify that the bass sounds seamlessly integrated and natural.  Note: You will likely need to precisely adjust the Volume and Cutoff Frequency controls on both 15 subs until you determine the overall bass performance has been optimized at your listening position.  It's best if you recruit a volunteer for assistance on this step.

     If you follow this procedure precisely in relocating your pair of HGS-15s, I believe you'll notice a few things. 
     First, you may be surprised at the locations that the two 15 subs actually wind up positioned at in your room when optimized for bass sound quality.  However, I can't predict even generally where they'll each be positioned in your room since it depends on the subs used, your ears/brain and your room qualities (dimensions, wall/ceiling/floor materials, furnishings and any room treatments present).  I just suggest you follow the procedures strictly and make sure you pay close attention to bass quality when locating them.
     Secondly,  I'm almost certain you'll prefer the overall sound quality using all four of your subs when compared to using just the pair of HGS-10 subs.   Remember, I'm speaking from experience using not only a pair of subs but a 4-sub DBA as well.  You'll notice the bass is even smoother, more detailed and with the realistic bass power, impact and dynamics that are usually only heard and felt when you're present listening to music played live. 
     But don't worry, the high quality bass is always there but the volume control still allows you to choose the overall volume level for playback.

Enjoy,
 Tim
Tim,

I'm willing to sacrifice a bit of acoustic perfection for visual appeal.  And acoustic room correction can help with the residual problems.  I strive for good organ pedal response without bass boom from jazz recordings.  A setup with a HGS-10 aside each KEF Ref 1 results in satisfying full range sound free of obvious sub involvement with the HGS-15s turned off.  An HGS-10 on either side of the Ref 1s, i.e., four of HGS-10s, might sound even better while remaining visually appealing.  The HGS-15s provide the slam for movie special effects, and may ultimately fit in for music.

db
   I was unable to get two of my subs in the perfect crawl tested locations but they were close. The Auto EQ did take up the slack in my room.
   I ran my Earthquake, the DD-18 and two DD-12 Plus mastered from one of the 12s. I was able to closely match the equalization of the 18 to the others with the calibration mic at the listening position, individually running Auto EQ followed by a few minor Manual EQ adjustments on the Velodyne's. 
   Your listening space may not need all four units. What sounds good to you is key. There are no absolutes. 
 Hello DB,

     It seems like you positioned your subs symmetrically in your room to make your system as visually appealing as possible.  However, I strongly suspect this positioning fails to optimize the audio bass response performance quality attainable in your room utilizing your four high quality subs. 
      I believe you'll obtain significantly improved bass performance, primarily noticed as improved seamless integration with your KEF main speakers, improved bass impact, dynamics, smoothness and naturalness, by positioning all four subs along the perimeter of your room in a distributed bass array configuration.  
     This is accomplished by sequentially utilizing the 'crawl method' beginning the search for the ideal positioning of the first sub at the front right corner of your room and proceeding counter-clockwise around the perimeter of your room.  
     Just continue positioning each sub optimally and sequentially until all four are located.  It's really up to you to decide whether you prefer to locate the larger 15" subs first, last or alternate between a 15" and 10" sub.  No matter the distribution pattern you choose, the ultimate audible result will be excellent bass response quality throughout your entire room.

     The bass results will be similarly smooth, natural and well integrated with your main speakers whether you deploy your current pair of 15" and 10" subs or if you deploy four 10" subs.  Including the larger pair of 15" subs will provide overall bass response that extends a bit deeper, has a bit greater impact and slightly better dynamics.

Tim
The Velodyne HGS-15s are now behind the KEF Ref 1s, an HGS-10 aside each Ref 1.  The HGS-10s are connected to one of the SMS-1s, the HGS-15s to the other.  With the SMS-1s daisy-chained I can turn one off if I want only the HGS 10s or HGS-15s.  I've been listening with just the HGS-10s active and I like it for music.  Makes me wonder about replacing the HGS-15s with another pair of HGS-10s.

The Sanus rack makes equipment very accessible and is a joy to use.  Should have done that years ago.

db   
@Clearthink i could probably place the level inbetween...... gonna give that a try, hmmmm -8db and call it quits

kgveteran
"
I just recently realized for music (in stereo) i have to dial back my subs to -12db"

It sounds like you're Music Reproduction System is improperly aligned, tuned, or installed for this to be the universal result with you're setup.
I just recently realized for music (in stereo) i have to dial back my subs to -12db, for movies i go back to -4.5b where Audyssey put it. I leave Audyssey engaged and DynamicEq on also, for my low level music its works
the two surround modes (Denon X4300), dts and Dolby both stink for surround music, I miss Prologic II.......
my subs are on either side walls 1/3rd into the room from the front screen wall, my LP is 1/4 into the room from the back wall, no EQ needed, it was all about the level. 
I have a rolling 600lb door that seals off the room for late nite watching, but I prefer the door open for music.........
Hello DB,

     For best results, I seriously suggest you ignore Velodyne's recommendation of placing one HSG-15 near each main speaker and instead just position them where they sound best using the crawl method.  They're probably catering to users who don't understand stereo deep bass is a myth with almost all music source material below about 80 Hz actually recorded as summed L+ R mono bass.  It's best, therefore, to just run all subs in mono and position each where they'll sound best sequentially which will also be the same positions the four will sound best playing in unison as a whole DBA system. 
     To prevent moving the 2 HSG-15 heavy subs more than once, you could place one of the 10s at your listening seat, use the crawl method to determine the optimum position of the first two subs likely along your front wall and place the two HSG-15s at both of those positions instead of the HSG-10s. Then use the crawl method to optimally locate the remaining 2 HSG-10s as normal, which could be anywhere along the side walls or long the rear wall.   This will result in the optimum bass response in your room for both 2-ch music and HT.
     You can properly set up the master and slaves in the proper order  and equalize them after the optimum positions are established.

Tim
For the two HGS-15s I think I'll start with Velodyne recommendation to place each next to a front LR speaker.  Each HGS-15 weighs 95 pounds, and I use Auralex SubDudes under them so sliding on the carpet is not easy.  I can lift the HGS-10s.  Right now, the big subs are in the corners and the small ones are next to the speakers.

In rereading the SMS-1 manual I realized I missed a step in daisy-chaining the units:  The slave unit should be set up independently first, then daisy-chained to the master unit and a full equalization performed of the combined acoustic output of the four subs.  I had not set up the slave unit.  Eventually I'll get it right.

I discovered the lack of slam I thought might be endemic to smaller speakers like the KEF Ref 1 is an artifact of some problem between the Bryston SP3 and Ayre KX-5/20 when playing Blu-rays.  Large orchestrations sent by Roon to the QX-5/20 digital hub have satisfying slam, but I've been using Roon for chamber and jazz music.  I'll explore the Blu-ray link when I install a Sanus rack next week that will make access to the rear of the components much easier.

db
dbphd: "The four subs, 2 Velodyne HGS-10s and 2 HGS-15s, are installed and the SMS-1s daisy-chained, although I’ll need some help in relocating each HGS-15s from a corner to behind the Ref 1s. I did an initial set up of the SMS-1s, but it will need to be redone when the subs are moved into place. I need to read the manual carefully, because there are subtle parametric adjustments I do not yet fully understand. One notable change with the additional subs is the elimination of the mild roll-off from 20 and 15 Hz. A first listen suggests the four sub array might sound superb."

Hello DB,

I know we previously discussed the optimum sub positioning and configuration of the four subs in a custom 4-sub distributed bass array (DBA) system but I think a few important points bear repeating.
For optimum performance when positioning the 4 subs in a DBA system each sub is run in mono mode and positioned sequentially in the room position that the bass sounds best to you (most accurate, detailed and natural). It’s best not to place subs in positions that are the most convenient or positions that you suspect the subs may sound best. The optimum results will be attained by just trusting the proven procedure of systematically and sequentially positioning each sub in the precise position the bass sounds best to you. You’ll also avoid the need to position any single sub more than once.
A properly positioned 4-sub DBA system requires zero room correction but, if you insist on using it, it won’t have any negative effects as long as you wait to run it until after all four subs have been optimally positioned in the room utilizing the very effective "Crawl Method".

Best wishes,
Tim

Don't forget to printout that Outlaw manual from the Velodyne site I posted above. Its a different format with some useful tips which might be of help.