The Resonance Point is Getting ANNOYING...

[j_garcia]

Can anyone confirm Theresa's sentiment regarding a sub being right up against the wall? That seems to be in contradiction of every theory that's been opinionated here.

Since you have first hand experience with it already in your room, I will say that there is not one perfect answer. Every room is different. In my experience, some subs may work fine that way and others may not. In my current room, as I said before, only one sub did OK shoved all the way in the corner. All others needed to be pulled away from the walls.

Sticking a sub right up against the wall reinforces its output, causing the bass to radiate out from that location. This is why comparing different placements (preferably with measurements) is key for getting the best performance out of a sub in a given room.

If Theresa didn't follow the rest of the thread when responding, she may have misread what I said, because we are talking about the difference between 1-2 inches from the wall and 6-12 inches, NOT placing the sub in the middle of the room.

 

[PearlcorderS701]

Almost everyone says to put a subwoofer up near a wall, and not out in the middle of the room.

If you doubt that, just do an online search of diagrams of recommended setups online, and try to find any that recommend putting the subwoofer in the middle of the room.

I'm not talking about putting a subwoofer in the middle of a room -- I am well aware of the fact that they're not designed to be placed there, and it's asinine to even assume one should go there. I was asking if anyone else agrees that a sub should be smack right up against a wall with no spacing between the port and wall at all like Theresa suggests...it seems every post on this matter, at least on AudioHolics, claims the opposite...that is, the sub should be pulled from the adjacent wall at least a few inches to a foot for best delivery...

 

[PearlcorderS701]

Since you have first hand experience with it already in your room, I will say that there is not one perfect answer. Every room is different. In my experience, some subs may work fine that way and others may not. In my current room, as I said before, only one sub did OK shoved all the way in the corner. All others needed to be pulled away from the walls.

Sticking a sub right up against the wall reinforces its output, causing the bass to radiate out from that location. This is why comparing different placements (preferably with measurements) is key for getting the best performance out of a sub in a given room.

If Theresa didn't follow the rest of the thread when responding, she may have misread what I said, because we are talking about the difference between 1-2 inches from the wall and 6-12 inches, NOT placing the sub in the middle of the room.

John,

THAT'S what I was trying to explain in my last reply -- I didn't mean placing a sub in the MIDDLE of the room, I was referring to the opinions that subs shouldn't be RIGHT UP AGAINST THE WALL with no space between the port and wall, versus what she suggested regarding a sub definitely needing to be right against the wall with no room between...

 

[Pyrrho]

I'm not talking about putting a subwoofer in the middle of a room -- I am well aware of the fact that they're not designed to be placed there, and it's asinine to even assume one should go there. I was asking if anyone else agrees that a sub should be smack right up against a wall with no spacing between the port and wall at all like Theresa suggests...it seems every post on this matter, at least on AudioHolics, claims the opposite...that is, the sub should be pulled from the adjacent wall at least a few inches to a foot for best delivery...

Since you have first hand experience with it already in your room, I will say that there is not one perfect answer. Every room is different. In my experience, some subs may work fine that way and others may not. In my current room, as I said before, only one sub did OK shoved all the way in the corner. All others needed to be pulled away from the walls.

Sticking a sub right up against the wall reinforces its output, causing the bass to radiate out from that location. This is why comparing different placements (preferably with measurements) is key for getting the best performance out of a sub in a given room.

If Theresa didn't follow the rest of the thread when responding, she may have misread what I said, because we are talking about the difference between 1-2 inches from the wall and 6-12 inches, NOT placing the sub in the middle of the room.

John,

THAT'S what I was trying to explain in my last reply -- I didn't mean placing a sub in the MIDDLE of the room, I was referring to the opinions that subs shouldn't be RIGHT UP AGAINST THE WALL with no space between the port and wall, versus what she suggested regarding a sub definitely needing to be right against the wall with no room between...

Theresa never said in this thread that a subwoofer should be touching the wall so that a port is blocked. In practice, a subwoofer will usually not need to be very far at all from a wall to not block a port. After all, all of the air moving through the port is moving through a fairly restricted space, which will be far less restricted at the end of the port unless it is incredibly close to the wall. With one round port, I would imagine that a distance of half the port diameter would be enough space away from a wall, though having someone measure these things would be better than guessing. I do, however, know of some speakers that are designed to be wall mountable, with rear ports, and are such that they are very close to the wall if one mounts them that way.

On the other hand, I would not particularly recommend orienting a subwoofer with the port aimed at the wall in the first place, unless the manufacturer recommended it.

 

[PearlcorderS701]

Theresa never said in this thread that a subwoofer should be touching the wall.

It was taken that way by me:

Actually, up against the wall is often the best place for a sub.

Now...perhaps she didn't mean with the port being blocked it was "so far up against the wall," but I took it to mean literally "right against the wall"...

Further, it's important to note that I did not mean a sub should be "in the middle of a room" by questioning her theory...

Out of curiosity, why shouldn't a port be facing the wall in your opinion? On my particular sub, the controls and knobs are on the same side as the port, so it would seem odd that I should turn the sub with the control side outward or even sideways...

 

[Pyrrho]

It was taken that way by me:



Now...perhaps she didn't mean with the port being blocked it was "so far up against the wall," but I took it to mean literally "right against the wall"...

Further, it's important to note that I did not mean a sub should be "in the middle of a room" by questioning her theory...

Out of curiosity, why shouldn't a port be facing the wall in your opinion? On my particular sub, the controls and knobs are on the same side as the port, so it would seem odd that I should turn the sub with the control side outward or even sideways...

I would not want to block the port, and have no worries about it (more on that in a moment). However, from your description, it sounds like your subwoofer is designed to be placed with the port toward the wall. I suggest following the recommendation of your manufacturer regarding this.

After very briefly considering the matter again, if we look at down-firing subwoofers, typically the woofer is very close to the floor (or the bottom plate on down-firing subwoofers with bottom plates), and some also have bottom ports as well. From that, my guess is that in any normal positioning near the wall as close as is generally going to be practical is likely to be fine. In other words, unless it is touching the wall, or very, very nearly touching it, it is probably much ado about nothing.

 

[Matt34]

I would not want to block the port, and have no worries about it (more on that in a moment). However, from your description, it sounds like your subwoofer is designed to be placed with the port toward the wall. I suggest following the recommendation of your manufacturer regarding this.

After very briefly considering the matter again, if we look at down-firing subwoofers, typically the woofer is very close to the floor (or the bottom plate on down-firing subwoofers with bottom plates), and some also have bottom ports as well. From that, my guess is that in any normal positioning near the wall as close as is generally going to be practical is likely to be fine. In other words, unless it is touching the wall, or very, very nearly touching it, it is probably much ado about nothing.

Agreed. Unless the port is physically being blocked or you can actually hear noise from the port because of the proximity of the wall I wouldn't be concerned. Most manufactures of ported subs recommend anywhere from a couple inches to a foot away from the wall.

 

[j_garcia]

Agreed. Unless the port is physically being blocked or you can actually hear noise from the port because of the proximity of the wall I wouldn't be concerned. Most manufactures of ported subs recommend anywhere from a couple inches to a foot away from the wall.

He IS having an issue with something on the adjacent wall vibrating and moving the sub away from the wall a few inches solved the issue. I think this thread has gotten out of hand, since the problem is already solved.

 

[TLS Guy]

Can anyone confirm Theresa's sentiment regarding a sub being right up against the wall? That seems to be in contradiction of every theory that's been opinionated here.

If the port is not on the rear, then often a sub against the wall will increase room gain.

However a rear port needs to be a good distance form the wall. A lot (most) commercial subs are not very good, and have ports that are far too small, giving vent air velocities well over 18 m/sec, and some chuff so much they must exceed 30 m/sec.

If the port air velocity is in the correct range then placing a port a few inches from the wall will be fine. However if the sub impersonates a leaf blower you need about 14".

In general if a sub uses a tube vent, that the port air velocity more likely than not is too high. If it has a slot vent, then the port air velocity is likely in the correct target range.

 

[Matt34]

 

[PearlcorderS701]

He IS having an issue with something on the adjacent wall vibrating and moving the sub away from the wall a few inches solved the issue. I think this thread has gotten out of hand, since the problem is already solved.

Thanks John,

Indeed, this was going in several different directions; the initial problem was that something in my room was rattling something awful during low-pitched bass hits, and long story short, when I rewired the whole system and subsequently moved the sub away from the wall a couple of inches from where it was -- now totalling nearly a foot -- this horrendous resonance seems to have stopped...only during ridiculously low bass drops and drones does something rattle in the room in different areas now, but nowhere near what it did and only occasionally.

 

[yepimonfire]

pearl, not that this will or will not solve your problem, but i just realized you have RTi12's for fronts, why are you even messing around with that crappy PSW350? you do realize your fronts have a lower frequency response then the sub? the sub is -3dB at 38hz 25hz -10dB, the fronts, 30hz with a -10dB point at 18hz. im pretty sure those speakers can produce much better bass then that sub, polks speakers have good accurate bass. their subs, well they suck.

 

[PearlcorderS701]

pearl, not that this will or will not solve your problem, but i just realized you have RTi12's for fronts, why are you even messing around with that crappy PSW350? you do realize your fronts have a lower frequency response then the sub? the sub is -3dB at 38hz 25hz -10dB, the fronts, 30hz with a -10dB point at 18hz. im pretty sure those speakers can produce much better bass then that sub, polks speakers have good accurate bass. their subs, well they suck.

LOL -- indeed I know Polk subs suck; I'm just using the PSW350 (which you actually told me in your Polk sub review thread some time back wasn't nearly as bad as I was making it out to be) until I could scrape up enough for a real replacement (probably an SVS) and then I will move the POS Polk to the two channel system for some bass reinforcement in that rig.

The reason I have the PSW350 and the RTi12s is because the sub is from an old previous system that made its way through all my systems over the years, so I had it before I bought the 12s for main channel duty...

 

[yepimonfire]

LOL -- indeed I know Polk subs suck; I'm just using the PSW350 (which you actually told me in your Polk sub review thread some time back wasn't nearly as bad as I was making it out to be) until I could scrape up enough for a real replacement (probably an SVS) and then I will move the POS Polk to the two channel system for some bass reinforcement in that rig.

The reason I have the PSW350 and the RTi12s is because the sub is from an old previous system that made its way through all my systems over the years, so I had it before I bought the 12s for main channel duty...

well considering your mains have much lower and more accurate bass response then the sub i would set the fronts to large the sub to none and the sub on fire

i had a psw10 in my old systems and when i got the monitor 70's i just went subless. IMO, not all towers really need a sub. if you were to buy a real sub that had a response lower then 30hz (say atleast 25hz) then it would benefit you, the biggest advantage of having a sub would probably not be the extra bass response but the ability to decouple the bass from the mains giving you better placement options. the drivers in the rtis are crossed over and built to act as subs, the drivers are actually crossed over with a 2nd order lowpass at 120hz, they have deep inverted dustcap cones large highroll surrounds etc etc. contrary to popular belief i actually have had a GOOD subwoofer at some point in time until i ruined it and i still stand by the statement not all towers need a subwoofer. try this - play a bass heavy movie like wotw with your sub, then shut off the sub and route the lfe through the mains, im sure the results will surprise you.

 

[PearlcorderS701]

well considering your mains have much lower and more accurate bass response then the sub i would set the fronts to large the sub to none and the sub on fire

LOL -- believe me, I wish I could set the sub on fire...I'd roast marshmallows right off its 10 inch driver...

But I think once I get a real sub into the HT system, the PSW350 should be okay for two channel duty in my stereo room...

i had a psw10 in my old systems and when i got the monitor 70's i just went subless. IMO, not all towers really need a sub. if you were to buy a real sub that had a response lower then 30hz (say atleast 25hz) then it would benefit you, the biggest advantage of having a sub would probably not be the extra bass response but the ability to decouple the bass from the mains giving you better placement options. the drivers in the rtis are crossed over and built to act as subs, the drivers are actually crossed over with a 2nd order lowpass at 120hz, they have deep inverted dustcap cones large highroll surrounds etc etc. contrary to popular belief i actually have had a GOOD subwoofer at some point in time until i ruined it and i still stand by the statement not all towers need a subwoofer. try this - play a bass heavy movie like wotw with your sub, then shut off the sub and route the lfe through the mains, im sure the results will surprise you.

I totally hear what you're saying -- and it makes sense on many levels; however, many will say that if you have a sub -- even if it's a worthless piece of crap like the 350 in question -- it is perhaps more effective to actually put it into service because of that dedicated ".1" LFE signal from DVD and BD soundtracks...there's something about feeding tower speakers, even huge capable ones, with the sub bass from .1 soundtrack signals that doesn't seem "right" to me. In the meantime, to at least let the RTi12s flex some of their muscle, I am keeping the crossover for these at 60Hz inside the AVR, as advised by Polk personnel; this seems to allow for a good balance of letting the 12s pound a bit while the sub gets even lower frequencies -- even though the PSW350 may not be able to handle those as well...

 

[yepimonfire]

*facepalm* i'm running the LFE out of my towers and its enough to piss off the neighbors.

 

[Pyrrho]

LOL -- believe me, I wish I could set the sub on fire...I'd roast marshmallows right off its 10 inch driver...

But I think once I get a real sub into the HT system, the PSW350 should be okay for two channel duty in my stereo room...



I totally hear what you're saying -- and it makes sense on many levels; however, many will say that if you have a sub -- even if it's a worthless piece of crap like the 350 in question -- it is perhaps more effective to actually put it into service because of that dedicated ".1" LFE signal from DVD and BD soundtracks...there's something about feeding tower speakers, even huge capable ones, with the sub bass from .1 soundtrack signals that doesn't seem "right" to me. In the meantime, to at least let the RTi12s flex some of their muscle, I am keeping the crossover for these at 60Hz inside the AVR, as advised by Polk personnel; this seems to allow for a good balance of letting the 12s pound a bit while the sub gets even lower frequencies -- even though the PSW350 may not be able to handle those as well...

yepimonfire is giving you good advice. You ought to move that subwoofer to the two channel system now.

However it may seem to you, there is absolutely nothing wrong with sending the LFE channel to the main speakers, if they are capable of dealing with it. The ONLY reason such a channel exists is because most speakers are not good at dealing with deep bass, so it is unwise to even try to do so. The origin of the LFE channel goes back to movie theaters, where there was a desire to add more bass, but without making the theaters replace all of their main speakers, which would have been unreasonably expensive to do. So they just added an LFE track, that, if a theater did not add any new subwoofers, would simply not play back in their theater, and it would not cause their main speakers to distort by trying to reproduce so much bass that they were incapable of doing. But for any theater that did add the subwoofers, they would play that channel to the subwoofers and have the bass.

In your case, your tower speakers are much, much more capable than your subwoofer, which means that your subwoofer is pretty much worthless in your system, and by using it, you are not getting all of the bass that you could be getting. You see, in the LFE channel, the frequencies below what your subwoofer can do, you are not getting too well. But you could be hearing some of them, if only you would redirect the LFE to your main speakers which play deeper.

Really, if you want the best sound from your system, you ought not use that subwoofer at all.

If you wanted maximum volume, you could send the LFE channel to both the front and it, but it would not be giving you maximum fidelity that way.

I almost never recommend running the main speakers as large, but in your case, you absolutely should, until you get a subwoofer that plays deeper than the main speakers. Right now, you are throwing away deep bass that you could be hearing, if you set it up as yepimonfire has suggested.

 

[yepimonfire]

not only is he throwing away that bass, polks subwoofers just aren't that accurate the only way i can describe their sound is "lumpy" even if you never decided to get a sub there isn't much you would be missing with -10dB at 18hz at least give it a shot and do what i said by playing some LFE heavy stuff with the speakers and not the sub. if anything wouldn't seem "right" to me it would be the fact that you are virtually wasting those towers capabilities, crossover at 60hz? even if you did have a sub that was decent i would still recommend either running them as large and letting the sub handle only the lfe or crossing them over at 40hz. those speakers were built to produce their own bass, like i said before three 7" drivers that are deep in each tower, and if i remember correctly the "subs" in those towers are in their own enclosure and ported seperately from the mid-range drivers.

must i go on and on about why you don't need to be using that stupid sub?

 

[PearlcorderS701]

Jeez Guys...

Take it easy; it's only a sub! I realize it's "stupid" and "useless" and I will get around to replacing it -- but there's another factor here beyond just the LFE element I mentioned: I do not want to tax the AVR I have powering the RTis any more than it is right now, because it's already a mismatch...by running the RTi12s full range, it's going to put too much stress on the AVR, which is unerrated for the RTi12s to begin with (well, I was advised by Polk that these towers COULD handle 500 watts RMS each, but you don't need to FEED them that on a steady basis to enjoy them and assured me my AVR is fine enough for now in terms of power...the 12s don't have a difficult ohm load or sensitivity, etc.)...and so I'd like to keep them crossed at 60Hz even though they're capable of doing more by themselves...

That said -- what would be a recommendation for a good, powerful sub to replace the PSW350 with that would definitely dig below what the RTi12s could deliver? What would make a good sub-bass match for delivering low notes beyond what these towers could do?

 

[Pyrrho]

Anything from SVS would get you deeper bass. Buy the best one you can afford, particularly if you like your bass loud or have a large room.