Placement of Single Subwoofer Affecting Sound of Main Speakers

 Sounds like you should just get rid of it. You haven't been using it anyway, and now its causing problems.Sell it. Just my 2 cents....

How is the sub connected? If you are using a line level splitter at the preamp, it may be loading down such that you can hear the difference even with the sub off.

 Even having a second set of line outs on a preamp is no indication that it might not be happy driving a sub.

Disregard this if you are using high level connections or have a dedicated subwoofer output on your preamp.

Oz

Maybe I should.. We'll see how it goes as I've just invested in some springs to enhance the sub's performance, still in transit.

How is the sub connected?

It’s connected to the amp’s preout with a pair of RCA interconnects. That’s the only method of connection that is available.

With the long transmission wave bottom octaves produce, sub placement is a tricky thing to do well depending on the room. Experiment multiple places and go with 1. what sounds best 2. has WAF 3. doesn't degrade from the main speakers.

Two or more subs helps produce more even sound throughout the room, so IMO I would look at adding another sub as I think that would provide the bass you want and eliminate some of the problem a single sub can provide. Read a little about the SWARM subwoofers, lots of good info there to think about.

Good luck!

sub can make everything sound worse...but a single sub if you have a single listening position can work quite well...crossover, phase, volume settings crucial, and take time to get right...I like the put the sub where you sit and crawl around the room, then put the sub where everything sounds best when crawling...

I have done both number 2 and 3 while one of my subs was getting fixed. Number 3 worked pretty well. I was using a highpass crossover at the time. 

+1 jl35's crawl test suggestion.

Most any room has an optimum location for a single subwoofer that will result in efficient performance at the listening position. 

You'll need a pair of long interconnects and an extension power cord. Monoprice or Blue Jeans cable offer custom length interconnects at reasonable prices.

Playing a test CD or file with a low frequency cadence will aid in hearing the loudest area or mode in your room.

You don't necessarily need to crawl around your room but it can provide a more dramatic sound.  

Positioning the subwoofer at or near this area should provide a satisfactory location to begin the other adjustments. Good luck with the aesthetics.    

Ideally you want one sub front and center. Front and slightly off center is next best. Avoid the corners. Rear center is another decent option especially if you sit closer to the sub than the front mains.   You can get away with a lot with sub placement though when needed especially if sub is set to not do much above 60-80 hz or so. 

Hey, and yes, but I didn't know it could happen with a direct radiating subwoofer. :)

The effect you may be having is that the sub is acting like a tuned bass trap, OR you are finding it's reflecting a lot from the speakers.  The latter can be tested with a blanket.  If the blanket covering the sub fixes your problem it's purely an acoustic reflection issue.

If it sounds about the same it's probably because the sub is sucking an octave out of the room.

Thanks for all responses. I find the below from Mapman particularly useful.

Ideally you want one sub front and center. Front and slightly off center is next best. Avoid the corners. Rear center is another decent option especially if you sit closer to the sub than the front mains. You can get away with a lot with sub placement though when needed especially if sub is set to not do much above 60-80 hz or so.

The corner placement with a single sub mirrors my experience. The current placement at the rear of speaker slightly away from the corner yields much better result. However, the effect or impact of a working sub is minimal since I have to set the crossover quite low at around 50 Hz. I tried setting it up to 60-80Hz and the sub is doing more harm than good with the bass sticking out like a sore thumb. Turning down the volume helps but there’s very little to no difference with the sub switched on or off.

I will likely try the 3rd option by pushing the sub further out to the centre of the room / speakers but it cannot be directly at the centre. When I tried this placement about a week ago, I recall the sound to be good but again the impact of the sub was minimal. Pushing the crossover and volume up too much and the bass sticks out too much. I will attempt this placement again once I receive the Nobsound springs.

I understand 2 subs(or more) are better but it is out of question. It is either 1 or nothing at all.

Should ask what sub are you using and what speakers? Also consider using white noise and a sound meter ( app on smartphone) to get an idea of what is going on in regards to sub filling in lowest octave at your listening location smoothly. Some speaker sub combos may not be matched well to accomplish that.

The effect you may be having is that the sub is acting like a tuned bass trap, OR you are finding it’s reflecting a lot from the speakers.

Yes, either one must be true. Somehow any furniture in the room will affect the sound, especially things placed very close to the speakers. I tried placing a 2nd set of speakers just beside the main speakers in an attempt to run 2 pairs of speakers in the system. I hoped it would work but the sound was ruined. In the end only a pair of speaker can remain in the room.

Should ask what sub are you using and what speakers? Also consider using white noise and a sound meter ( app on smartphone) to get an idea of what is going on in regards to sub filling in lowest octave at your listening location smoothly.

The sub is a PMC TLE1 (dual 6.5" woofer, transmission line) and the speakers are Marten Duke 2. Will try the more advanced set up method you brought up sometime. At the meantime, using the ears will do it for me. I have a Radioshack SPL meter though.

The previously mentioned "crawl" method does have some credibility. Also the "swarm" setup may be the optimum option for using subs but since you are limited to only using a single sub that option is out.

Sub integration into any system/setup is one of the most challenging for audio/HT listening, A sub can offer so much enhancement to any system if done right. I have read MANY  posts since I once faced the same challenge. After reading about a lot of different scenarios people on this forum several times I have responded with a link that explains almost everything about subs. It's lengthy and quite technical bit if you look through the info you may find something that helps......

http://www.soundoctor.com/whitepapers/subs.htm

If you only have three (?) locations for the sub that "work" (WAF at work here?) but none of them really work, get rid of the sub unless you're willing to find the actual optimum position for the sub sonically.  Placement in the wrong position in the room can result in bass suck-out and a non-integrated sound that is worse than no sub.

One other possibility in those locations is to move the sub up off the floor a foot or two and see what happens.

Also, if you don’t have a room measuring system, try this:

if you have a tv in your listening room that can connect to your audio system and to YouTube you can run a frequency sweep video and listen from your seated position and you will hear the peaks and nulls. Then move your sub around and see what changes… hopefully the room isn’t too bad and you can improve things at the listening position with slight moves left right forward backward or up off the floor… and you might find the solution by moving the mains or even the seating position just a few inches as well.

Good Luck

What components do you have?  What subwoofers do you own?  What is the size of your room?  Sounds like you don’t have room for your subs anyway?

I don't know anything about your sub but I'd still try to set the crossover low like you have been. I really enjoyed one REL Britannia B1 sub set deep in a corner away from both speakers but crossed at 30Hz or so.

My main speakers go way low (not high passed yet) but B1 sub made the bottom two octaves fill in for a solid foundation that was very enjoyable from my singular listening position. I even achieved a +- 2dB from 31-200hz in the 'seat'. It was smooth and deep.

I've since moved to three sealed SVS subs for a distributed bass array and need to get one more sometime soon so as to have four total. (I still have to explain what the two old RELs and single DefTech subs are for... (TV and home theater rooms, 2).

I'd try in between the mains. I did that twenty years ago and it worked well in another home.  Good luck!

I can echo others in stating that integrating a sub or subs can be a big challenge. I’ve fought many rooms and many single sub setups over the years trying to get things to sound right.

My advice is to keep trying since that sub you have seems to be a very nice piece and should add quite a bit of enjoyment. Move things, change settings, etc. as you have been doing until your ears tell you it’s right.

I’m a firm believer in a dedicated outboard crossover too where you can just assign low frequencies to the sub (low pass filter) and roll off the low end to your main speakers (via high pass filters). As stated a million times on these boards, getting those low frequencies out of your main / satellite speakers really reduces intermodulation distortion and makes a world of difference.  For me (but other persons experiences may vary), having that dedicated crossover makes integration of low frequency cabinets much easier.  I've never had too much sucess with running the main speakers full range, then adding in a sub with just a low pass crossover (which is typically built into self powered subs).  24 db per octave minimal slope helps too on both high pass and low pass.

I have 4 systems in my home ranging from decent stuff to stuff that’s in the garage. Three of the systems have subs and I don’t think I could live without subs, especially on the two critical listening systems I have set up.

Hello,

Besides all of the good things to try above I would also check the Phase of the sub. If it’s out of phase it can really mess with the sound if it’s in a bad location. Sometimes there is a switch on the sub itself. If you don’t mind spending $150+ IsoAcoustic makes a sub platform that come with spikes. I think it’s called Alperta Sub. It works great as long as you subs don’t have a driver on the bottom of the sub like a REL T9. I think putting the sub in the listening position and crawling around is your best option. People sometimes turn the sub too loud. Turn up the crossover to 60 hz and turn down the volume until it disappears from its location. 
If you are in the Chicagoland area this store is an IsoAcoustics dealer and they can help with the sub placement. Maybe a wireless kit is the trick. 
holmaudio.com

They let you try before you buy something in your home. Very easy to deal with. I hope you can get the sub to work. It really made my system great. 

Hello Ryan!  The sub will absorb energy since its cone is moved by the sound in the room (especially bass) and since its cone moves, it generates sound itself even though its just sitting there not connected to anything. That's the problem with listening rooms with multiple speakers at a dealer's showroom. You could just put a pillow in front of it, connect the two terminals together, move it out of the room, or throw a rug over it. If you decide t use it, be sure it's in phase with the main speakers. Listening and then switching the leads listening some more will tell you what's right. Good Luck.

Have the sub to the left of your left floor standing speaker or to the right of your right floor standing speaker. The sub parallel in line with either. And at 0 phase. With the best crossover chosen(60 Hz? 40Hz? 80Hz?) for your room....I dial between 50Hz and 70Hz. And the volume low but just enough. 

That will give you the best chance with 1 sub as that is what I have currently. 

An update. To cut a long story short, the sub is staying. I’ll keep this short and avoid being long-winded. Most experienced folks would have known about this. After moving the sub around, I figured out that the placement of the sub is everything. The difference it makes is just massive.

As expected, the current best placement of the sub is between the speakers. It’s not at the centre but closer to the left speaker. I also found that the front of the sub needs to be on the same plane as the main speakers after moving it front and back. The sub now has about 2 feet from the rear wall (previously 5 inches).

With the new placement of the sub, the volume and crossover settings are completely changed. After trying several settings with different music, I’ve settled with these. The crossover frequency can now be turned up higher without the bass sounding forced or unnatural. Please feel free to comment if the settings need some adjustment. The volume and crossover settings are most important, phase setting is least important as I’ve always left it at 0, presuming the sub is in phase.

The volume is at 75%, rather high.

Crossover frequency is currently at 62 Hz.

Phase at 0.

I’ve also replaced these lowly interconnects

with some decent ones as below. Van Damme cables.

I’m not sure if it has made a difference but the new one is certainly more sturdy than the thin flimsy wires I was using before this.

The Nobsound isolation feet will be the icing on the cake.

You might want to put your sub in your listening position and then move to various points of the room and listen for the best sound.  Then simply put the sub in the location where you were located.  

Did you replace the stock power cord? If not, even a $100 after market power cord should make a difference.  Many will tell you that unlike other components, a subwoofer does not need a power cord upgrade; but, doing so ending up providing a subtle but noticeable improvement for me.

It’s still a stock power cord. Will look for some better cords soon.

I’m amazed at the transformation of the system. It is quite rewarding once the integration of the sub to the speakers is close to seamless.

FWIW.....

I have my Rythmik F12G next to my left MMG in the exact spot #3. It is pretty much on the same plane as the mains, maybe a couple inches behind (sealed sub, about 8" from wall). I’ve mentioned this before but I’ll say it again because it was one of the best pieces of sound system advice I’ve ever gotten, courtesy of the A’gon member who I purchased the sub from:

If you have a speaker distance setting ability anywhere in your pre-pro stage, you should get a much more accurate presentation and much better bass integration if you add distance to the actual distance between the sub and listening spot in the speaker settings - I know I certainly did. In my case, my listening position is an actual 14’ away from my mains/sub. I have the sub set at about about 22.5’. This really, really tightens and focuses the bass integration. Call it smoother, call it seamless.....whatever. Depending on your listening configuration, your optimal setting will vary. I dial it in to 0.1 of a foot, with changes made depending on how we may have rearranged the living room, which we do with some regularity.

It may not be purist, but in a combined 2.1/HT system with a decent bass management DSP (Denon AVR-X4000) and an acceptable preamp (Parasound P5) I’ve had very good success integrating my single sub into the system. I plan on adding a smaller sub to the back of the room, behind me and to my right which will be a bit diagonal from the front mains/sub, so that should enhance things even more.

But this advice that I got was spot-on.

Added some isolation to the sub. Bass now sounds tighter and more seamless. Crossover frequency is bumped up from 62 to 68Hz without any ill effect, an increase of 6 Hz. Volume on the sub is now lower to compensate for the higher crossover frequency.

In summary, it’s an improved performance with these isolation feet which is a worthwhile addition. Previously on spikes or the sub sitting directly on the floor without spikes.

The image below shows the previous set up where the sub was sitting on the floor without any spikes.