Stereo Subs or Dual Mono??

I am looking to integrate a pair of SVS Sb13’s with my Tekton Impacts, and am looking for a bit of advice on which direction I should take.

Reading through multiple threads, books, and videos, my two options are setting up the subs in either: true stereo (left ch to left sub, right ch to right sub), or dual mono. The general consensus is that a stereo sub setup is better for music, but that dual mono would be better for minimizing nulls and modes in the room.

My room is less than optimal, 15x12 with a cathedral ceiling, one wall along the length is halfway open to the rest of the home. Due to WAF, room treatment is a no go. With my mains running full range, I have a 16db peak at 45hz, 5db suckout at 90hz, and a 5 dB peak at 110hz. I am hoping the PEq in the SVS can help with the peak at 45hz. Placement options are limited to flanking the main speakers or midway along the length of the room on both sides.

My preamp is a Parasound P6 which offers easy dual mono integration with xlr output and built in crossover. My rack is off to the side near the seating area, this made a significant improvement in imaging and depth of the mains. Wiring dual monos would be easy, running a 25ft XLR to the left sub and daisy chaining the right with a 15ft XLR. Stereo wiring would be a bit complicated, I would need to run the main outs using 30ft (60ft total) of XLR to the right sub and back, and 25ft (50ft total) of XLR to the left sub and back. Additionally, I would need to use the high pass/low pass filters in the sub, and would likely see a hit in sound quality of the mains.

Are running subs in stereo that much better than dual mono that it would worth the hassle? Is the DSP crossovers built into the SVS subs transparent enough to make it worth it?

 

I run my dual subs as left ch to left sub and right ch to right sub....is there another way to do it?

 

Most preamps that offer bass management only offer mono outputs for subs. Typically the only way to get stereo subs is run off of you main preamp outs

 

very interesting ... I don't have answers but it seems to me the only way to 'know' is to try it both ways. I may have a similar quandry when I finally move my system to our new house ...

Edit: I think just running both in mono/summed L+R makes the most sense ... low bass is pretty non-directional, and unless a low bass tone is 'imaged' off to one side, seems to me it wouldn't be noticeable if the subs were mono or L and R.

Also, unless the subs can be placed near the speakers and/or symmetrical WRT listening position, the 'stereo' effects wouldn't be set up very well anyway. Seems like it would mess with the overall imaging ... just my 2 cents ...

PS: OK seems like flanking the main speakers or directly to the sides ARE the setup options ... hmmm ... !!! now it's back to trying both ways ...

PPS: Stereo wiring ... ??? Do the 'Crossover off/on' and Low/High Pass controls on the RCA unbalanced outputs affect the BALANCED outputs? Doesn't seem like they should. Assuming that's true, running single XLR cables to the subs (one from Balanced L to the L sub, the other from Balanced R to the R sub) is all you need to do for stereo subs. Then use the subs' built in crossovers to set their low pass frequencies. They're designed for that so no degradation in sound quality seems possible (altho anything's possible I suppose).

THEN you could high-pass your main amp/speakers' signal using the RCA Main outs if desired. Trying it with/without the Crossover engaged/set would add more possibilities but may result in improved sonics. EDIT: I guess what you were talking about involves running the HIGH pass output of the sub all the way back to the main amp ... OK, if you insist on using the balanced outputs only ...

(I admit it seems somewhat 'iffy' but I use a KRK ERGO after my Parasound P-7 to split/EQ my sub and mains in a similar manner. I'm convinced after trying a few variations/iterations that it makes the best sounds in my system, and the A/D/A steps going thru the ERGO don't degrade the sound in any way I find objectionable.)

Seems like that's the way to go IMO. Then each sub's EQ or whatever can be tuned for its particular situation. Seems like then you will have to experiment, but at least things will be optimized for L and R individually, which to me seems like a better approach. If they end up both the same, then it seems like it's the same as 'dual mono' but with stereo capabilities if/when that becomes important (for a particular piece of music). If say you have an organ symphony where the organ/pipes are over to one side ... ! Seems like the best way to reproduce it!

I think I've just answered my own question about my new listening room, thanks for bringing it up!

 

That’s how I run mine: from the Meridian 502 pre-amp (no bass management) single-ended into the subs, balanced into the Meridian 605 mono blocks.

Use the sub controls for fine-tuning: dial back when you can hear/localise the subs from the listing position until you cannot.

 

I am going to start out running them with the sub-out from the preamp in mono and see how it sounds. If the best place for them is flanking the speakers, I’ll fork out for the cables and try them in stereo.

 

Unfortunately, the crossover affects both RCA and XLR outputs. If I find that I do not need to use any crossover on the mains, then this is definitely a path to consider.

I could use the crossover on SVS to cross the mains, but i’m weary of degrading the SQ

 

I don't necessarily agree with this. I can pretty much always tell where a sub is located when others say I can't. I don't understand how I can hear that but others can't, but alas that is the case for me with a lot of sonic attributes.

It is true that bass propagates in an omnidirectional manner but that doesn't mean that the direction of it's source can't be detected. That means that you will hear the bass whether you're in front of the speaker or behind it but you should still be be able to tell where it's coming from.

Another problem with summing bass is that you can end up with some cancellations.

 

?? I run my subs (REL's) off the amp outputs. I own mono amps, so the subs get their signal from the left and right mono bloc....left sub gets the left info, right gets the right...which is why i believe it is a stereo set up. The upstream preamp is where the signal is split to the amps. Not sure how why you would prefer to have two subs running the same mono signal...in a stereo set up?

 

Are you using the high level inputs on the REL? Most subs around these days do not utilize these, and only have RCA or Balanced inputs (REL is unique in having this)

 

In order to use the REL subs off the amp outputs, one has to use the high level connection. I think the REL connection at the amp through the high level makes a lot more sense than the typical low level connection from the preamp.
I also own a balanced output Jeff Rowland stereo amp...that is more difficult to hook up from the amp side with REL's....so much so that i had to have Jeff modify the ground on the amp for me.

 

With one of the 2.1 systems that I run in my main HT's room (see link below) I can feel/sense its SVS sub off to my left with some bass-heavy music tracks, which is why I continue to search for another of the same to place off to the right.

Regardless, I see no advantage to running dual stereo instead of dual mono. I know of only one music track where the low low bass that I sense / feel is different in each track, and in that case I can only detect the stereo separation when using my Denon headphones. (I'm talking synth notes way below even the lowest notes that a bass guitar plays.)

Jeff

 

or speaker level inputs

 

This is easy......since your P6 has the excellent bass management system, try both. I have a Parasound HINT and if I ever get another sub I'll just experiment with going stereo and then mono. Seems to me the stereo setup will take some careful dial in, especially with sub volume and phase setting. I think you need to adjust each sub on its own with the matched speaker if you are placing next to each L/R main, especially phase. I would want to make sure each sub driver is moving in phase with the main spkr woofer.
I remember reading a setup process for stereo I think on the JL Audio website.

I would listen for at least a week or two then swap to mono.

 

Put some time in last night getting setup. Did a sub crawl, but I had a hard time deciding what I liked, so i pulled out the umik and REW. The smoothest response was on the sidewalls near the center, so that's where I am setup for now. I also ran some sweeps with the mains, I tried plugging the ports on the back, and found that to smooth out the peak I had a 40hz. I believe the resonance frequency of the room is at 40hz, and the cabinet was reacting (good ole Tekton bracing, or lack thereof). Plugging the ports noticeably cleaned up the midrange, and vocals sound clearer, but it did thin out the bottom ever so slightly, the verdict is still out if I will keep them plugged.

I ended up wiring the the subs in stereo using the XLR outs to the sub, and RCA's to the power amp. I tried looping the sub lines back to the power amp through the SVS connections, but once I hooked up the return lines to the SVS, I got a noticeable white/RF noise coming through the mains. Bypassing the SVS and connecting the wires together, the noise goes away. So it looks like there may be something going on with the plate amps, an email went out to SVS. The bummer is that with the current configuration, I am unable to use an crossover on the mains. The good news, is that the extra cabling didn't seem to have an affect on sound quality, so if I can get the noise issue solved, I should be able to loop through the subs.

At this point, I have only level matched the subs with the mains, and crossed over the subs at 60hz, -24db slope, with mains at full range. Initial impressions, the sound stage has extended past the front of the speakers, giving an almost holographic depth. I put on a few jazz tracks, and in one instance I felt like I can almost see where stringed instruments are placed on the stage, very creepy stuff. Prior to this, the soundstage was only from the front of speakers and back. I am also hearing a lot more detail in everything, all of the mids and highs seem clearer. I do have a lot more work to do, adjusting phase and tweaking crossover points, but so far, so good. My only gripe is that I am not getting the slam I was hoping for, but hopefully that will come with tweaking. Even with the subs where they are, I am not getting any localization. Honestly, I cant even tell if they're there, it's very subtle. But I haven't had a chance to crank it up yet.

 

Wow, excellent! Maybe the new clearer sound etc. will outweigh the seemingly small negatives you discern. Possibly the lack of 'slam' or "thin(ning) out the bottom ever so slightly" is due to cleaner bass? An effect of reducing the magnitude of the resonant peaks?

Seems like an excellent improvement, gives me some good ideas, thanks !!!

PS: Is the 'wave' pic a sound treatment thing? I imagine a painting or print would have at least some sound absorption/diffusion qualities, just curious ...

 

No, it is a thin canvas print, but not a bad idea

 

I've said this before, as I am a new sub user. But when I understood the phase setting on my SB2000 and set up playing a tone at my crossover setting, everything came into place. I get more detail from my mains now and the low end seems very precise. Understand that phase will never be exact or perfect, you are looking for the best case scenario.

One question, how far away from back wall are your mains, you might get more bass or slam by pushing them back a tad, that might be a tweak you listen for, you've got nearfield listening with a lot of drivers.

Looks very nice and comfy.

 

The front panel of the main drivers is about 34" from the back wall, they were placed there as a balance between boomy bass and soundstage depth (before subwoofers came into play). I'll experiment with moving them back.

Does this method of adjusting phase work when only the subs are crossed over, and not the mains? I read the entire article by "sounddoctor" (the same article on the JL website). He calls for crossing over both at 80hz and running the subs in mono.

 

Well I am not sure, I think 80Hz is the "common" setting to start with, but I always understood you want to cross around 10-20Hz above where your mains start to roll off and use that range to find that seamless low end transition.
Phase to me is about getting the highest dB level at your crossover point, which tells me the sub and main woofers are in sync rather than opposing each other.

 

Thanks

 

Something interesting I found when setting phase using the above method. When setting the left sub to left speaker, phase is at 0. But when setting the right sub to right speaker, phase is at 90. Would this mean that the right speaker is wired incorrectly?

 

Wired backwards would be 180 deg.

Sounds more like a placement or reflection thing.

 

Glancing at your setup, looks like a reflection thing.

 

Thanks!