[ctviggen]

My HT room is about 23 feet, 8 inches long by about 17 feet, 6 inches wide (I say "about" because it's the bottom of a raised ranch, meaning some walls are on the foundation and come up half way into the room, then the wall bumps outward about 10 inches, and the room isn't perfectly rectangular).  For multiple reasons, I'm going to place one sub approximately half way along the length of the room, basically pointing to where the first row of people will be.

Where should the second sub go, if the goal is to even out the bass response?  I'm going to run wires soon and can run to possibly two locations; I'm just not sure where the second location should be.

Any hints are welcome.

[bpape]

Based on the Harman research, a sub centered on each side wall is a good layout.  This will help to tame some of the modal issues in the room. 

Bryan

[Mr Peabody]

Many subwoofer manufacturers such as REL and SVS recommend corner loading subs.  Low frequencies are typically not localized.  Meaning you shouldn't be able to tell where they are coming from, so no need to try to place them by the viewers.  Corner loading increases the subs output into the room.  So either in or close to each front corner would be a good placement.  With that being said, any time you are trying to place a sub experimentation with placement is in order.  And, hopefully you are using a SPL meter.

[Duke]

If the goal is smooth, even bass, then I suggest asymmetrical placement.  The idea is you want the subs to be significantly different distances from the room boundaries in as many dimensions as possible.  This way the two subs will interact with the room modes quite differently, each producing a unique, dissimilar peak-and-dip pattern at any listening location within the room.  In general the more dissimilar these two peak-and-dip patterns, the smoother the net in-room response. 

So for instance if one sub is 2/5 of the way down one side wall, you might put the other sub 2/3 of the way along the nearer of the two adjacent walls.  Face one sub towards the wall and the other parallel to the wall, or have one of them a foot or so closer to the wall than the other, or find some other way to stagger the woofer-to-nearest-wall distances.  If possible introduce some vertical asymmetry as well.

[ctviggen]

Thanks.  You know I forgot totally about this. 

My current thought is relatively asymmetric placement.  I will place one sub in the corner and another near the middle of the opposite wall.  Will put pictures here soon...gotta go, hear the toddler getting up.

[zybar]

Thanks.  You know I forgot totally about this. 

My current thought is relatively asymmetric placement.  I will place one sub in the corner and another near the middle of the opposite wall.  Will put pictures here soon...gotta go, hear the toddler getting up.

Bob,

Asymmetrical is definitely the way to go.

In the coming weeks I am going to hopefully have 4 subs in my HT plus a couple sets of butt kickers!!   

My goal is to start off with the subs in a asymmetrical fashion (but not corner loaded), but I will definitely be measuring and using that input for final placement.  I am also going to try and elevate one of the subs off the floor. 

Once I have things locked in, I'll try and remember to post back to here or start another thread.

George

[Mr Peabody]

Are the subs same brand and model?  Both using same output?

It would seem not being symmetrical would introduce separate placement issues for each one.  Why would this be better?  Just curious as it's not what sub manufacturers generally recommend.  Keep in mind that when same sound frequencies meet they increase amplitude at that frequency, no cancellation as long as they are in phase.

[budyog]

I have mine placed under my speaks all coupled together to become one with the floor and house! They sound great! I do use a R-DES and that fixed any loading issues.
See my gallery.

[ctviggen]

Thanks.  You know I forgot totally about this. 

My current thought is relatively asymmetric placement.  I will place one sub in the corner and another near the middle of the opposite wall.  Will put pictures here soon...gotta go, hear the toddler getting up.

Bob,

Asymmetrical is definitely the way to go.

In the coming weeks I am going to hopefully have 4 subs in my HT plus a couple sets of butt kickers!!   

My goal is to start off with the subs in a asymmetrical fashion (but not corner loaded), but I will definitely be measuring and using that input for final placement.  I am also going to try and elevate one of the subs off the floor. 

Once I have things locked in, I'll try and remember to post back to here or start another thread.

George

I would appreciate another thread, as I'm also interested in butt kickers (or other transducer type devices).  That sounds like an awesome setup.  I still have a long, long way to go until I can start actually testing everything, as the pictures will show.

I have two VMPS larger subs, powered off of 1000w amps with phase, amplitude, and (single) notch filter control.  Both subs will be on platforms (sub stands, they're called). 

In the past, I've had single subs, but I could always locate the sub.  I then moved to stereo VMPS larger subs, which seemed to be OK (with an AVS thrown in for movies).  These were placed behind my main speakers. 

I've done various amounts of reading, and can't quite decide whether placement in corners or asymmetrical placement is the way to go.  This site argues that asymmetrical is better (as are more than two subs, which is my goal):

http://mehlau.net/audio/multisub_geddes/

My room is still back to the studs (no drywall), so now is the time to run sub cables.  I can obviously run more cables than I need, to more locations than I need.  But ideally, I'd like to minimize the number of runs, for reasons including it's a lot easier to say to run extra runs than it is to actually run those. 

[zybar]

Bob,

If you aren't sure about ultimate placement, why not run conduit to allow for choices later on?

I have tried corner/symmetrical placement and unless you can do some eq'ing, it doesn't produce the same results as asymmetrical placement - at least in the three rooms I have compared.

Good luck with the build.

George 

[Duke]

It would seem not being symmetrical would introduce separate placement issues for each one.  Why would this be better?  Just curious as it's not what sub manufacturers generally recommend. 

Good question, Mr Peabody.

Herein lies the answer:

Keep in mind that when same sound frequencies meet they increase amplitude at that frequency, no cancellation as long as they are in phase.

Remember that once the sub is in a room, you cannot separate its response from what the room does to it.  And the room's effect is dominant.  We do not even hear "direct" and "reverberant" bass energy in our home listening rooms; it takes the ear more than one cycle at low frequencies to even hear bass, and by that time the room's effect is in full swing.

For a single subwoofer, there is no possible placement that will result in smooth in-room bass.  Let's say we have in-room response that is plus or minus 6 dB, with those peaks and valleys caused by the way the reflected low-frequency energy re-combines in-room - sometimes adding in-phase, and sometimes adding out-of-phase and thus cancelling.  Now suppose we have two subs placed asymmetrically.  Each by itself will produce a plus or minus 6 dB response, but they will be dissimilar.  Combined, they will be audibly smoother than either one alone would have been because they will not both be zigging and zagging at the same frequency.  They will smoothe one another out precisely because their room-modified outputs will not be adding in-phase.  And because it takes the ear a long time (relatively speaking) to hear low frequencies, these multiple sources don't actually sound like multiple sources (though you need a steep enough low-pass filter to prevent audible lower midrange energy from leaking through).

By the way, Earl Geddes and yours truly are two sub manufacturers who recommend asymmetrical placement of multisubs.  Earl recommends three subs with one in a corner, one along an opposite wall, and one near the ceiling.  My system uses four subs with slightly looser placement requirements (in-room smoothness goes up as the number of distributed bass sources goes up, so if you can't place one near the ceiling then you can make up for that to a certain extent by adding another sub).

[ctviggen]

I meant "SVS" (a sub manufacturer) not "AVS".  This sub, I placed about 2/3 of the way down the wall.  At that time, I didn't consider playing all the subs at one time, and I sold my SVS.  Darn it!

Hmmm....a sub near the ceiling?  That could be tough.  The two VMPS Large subs are so big that even though the room is about 17x23, there aren't many places left for subs.  One more smaller one might be possible, two would also be possible but would be a stretch. 

This weekend, I'll draw up a quick sketch of the room and post some pictures.  This will make my quandary clearer. 

[Mr Peabody]

Interesting.  I had to move some cabinets into the front corners of my room and wondered what would happen with a sub near the ceiling.  I'm using only one SVS PC13 Ultra in my room.  The U13 is an excellent sub.  I haven't used anything that blended into the other speakers that well. 

My processor has the built in auto set up and room equalization but I haven't applied it yet.  I probably should to see if any improvements are made.

It would seem with multiple subs you wouldn't need those seat devices.  You all are going to have your inside anatomy rearranged

[Phil A]

I've been using 4 Rels in my main system for years (left and right -Storm III, center - Q150, rears - Strata III). 

[Mr Peabody]

Nice subs.  Do you have the REL's hooked to the speaker posts for everything or a dual hook up, one for music to speaker posts and one for HT via line level?  REL was in the running with me when I was looking for a sub but they were almost emphatic about corner placement.  My SVS is on the side wall a few feet out from the back wall, it was not possible for corner placement.  I was surprised the U13 took to that spot well and I didn't have to do much experimenting.  I was hoping the cylinder shape and down firing woofer wouldn't be as critical on placement.

[TRADERXFAN]

The Geddes recommendation is just to be nearer to the ceiling. Should be above the centerline of the wall.

And you dont have all of the subs up loud necessarily. It is usually one sub, the "LFE" is turned up to meet the mains output, and then the other ones are lower in output so they aren't very noticable.

There is a whole discussion of this in GedLee speaker thread.

I think Duke's application is easier for most people, though.

Tony

[Duke]

Thanks for correcting where I was imprecise, TraderXfan.

Earl uses different sized subs, and his ubersub is a bandpass sub with a long vent (actually a cluster of vents) that extends vertically far enough that its exit is above the midpoint of the walls, thus meeting his criteria of having one low frequency source closer to the ceiling than to the floor. 

[Mr Peabody]

I'll have to check it out because it seems a waste to have extra subs then turn the volume below the other sub or rest of speakers.  My thought process would be to have all the subs at the same level to pump increased air pressure into the room which what I thought the goal was.

[Phil A]

Nice subs.  Do you have the REL's hooked to the speaker posts for everything or a dual hook up, one for music to speaker posts and one for HT via line level?  REL was in the running with me when I was looking for a sub but they were almost emphatic about corner placement.  My SVS is on the side wall a few feet out from the back wall, it was not possible for corner placement.  I was surprised the U13 took to that spot well and I didn't have to do much experimenting.  I was hoping the cylinder shape and down firing woofer wouldn't be as critical on placement.

The center and rear subs are just high level connected with the crossover set to match the speaker's response (I have a one-third octave RTA).  The subs for the left and right are connected both ways but at the moment with the gain I have (I have them connected balanced via a custom balanced Y splitter I made) they are set-up using analog inputs from a Blu-Ray player (my pre/pro does not have HDMI) so they (the fronts with the subs) are playing full range.  I'll be moving my old universal (Marantz DV9600) to the basement so until I have an HDMI pre/pro (perhaps in less than 6 mos.) I define everything except the rears as full range.  When I have the flexibility of crossovers via a digital connection, I can do more.

[poseidonsvoice]

Thanks for correcting where I was imprecise, TraderXfan.

Earl uses different sized subs, and his ubersub is a bandpass sub with a long vent (actually a cluster of vents) that extends vertically far enough that its exit is above the midpoint of the walls, thus meeting his criteria of having one low frequency source closer to the ceiling than to the floor.

Here are pictures of what Duke is talking about:

Earl's ULF sub or the CANNON:



Here is a closeup with the multiple vents:



Great discussion y'all...

Anand.