The Resonance Point is Getting ANNOYING...

[TLS Guy]

I'm not really planning on getting that new, larger sub until I get this issue, somehow, under control; I am under the realization that a larger, more powerful sub such as an SVS I have been eyeballing, is going to make that rattle even worse.

Get rid of the decoration! It sounds as if it should be at Goodwill anyway.

 

[highfigh]

Thanks for all the input, fellas. Much appreciated; with regard to my comments about switching my sub from the 350 to an SVS or HSU, it's not that I wanted to upgrade subs thinking this was going to solve the rattling problem, I was merely pointing out that I was getting ready, finally, to consider dumping my POS 350 -- of course, I am aware of the fact that by swapping in a new, more powerful sub like an SVS or HSU the rattles won't disappear and will most likely be progressively more aggressive...

I will consider the suggestions regarding adding treatments to the source of the rattles, which I believe is a metal decoration we purchased at Home Goods that sits above the fireplace, but I think I would want to go the "sub on an absorbing platform" route first. Any other input on these platform kind of devices? Are they worth buying?

There are three ways sound is transmitted- acoustical signals causing the object itself to vibrate, conduction (structure-borne), and acoustic signals causing the large panels in the room to vibrate so strongly that they cause the metal object to vibrate. Since it's unlikely that the vibrations are traveling through the structure and causing the metal to rattle, a subdude or gramma will do nothing because the wall is more rigid and massive and in order for this to happen, you would feel it a lot more than you do. Place your hand on the wall next to the metal object and press on it- if the vibrations stop, you'll need to stiffen/add mass to the wall. It's unlikely that the sub is causing the wall to vibrate so strongly that it's making the metal vibrate unless the wall has wide spacing between the studs. The most likely cause is the subwoofer's output hitting the metal object's resonant frequency and if it's just metal/wall contact, the rubber or foam pads should help.

 

[PearlcorderS701]

PSW350 SITUATION UPDATE:

Okay. Did an entire rewiring of my system last weekend to try and find the culprit of a buzzing/ground loop-like hum that ripped through my main speakers when I jiggled or moved the tangle of wires and cables behind the system and wall unit...I cleaned up all the wiring, bundling and separating power from interconnect and signal flow routes with cable ties, and in the process, I discovered something about the subwoofer situation we're discussing here...

My wall unit housing the system and TV had been moved out from its position nearly two or so feet so I could get to the back of everything for the rewire, and in so doing, I moved the sub off the wall a good few inches, maybe a half a foot or so. I also upped the sub calibration number one dB in the AVR's setup menu. Playing bass heavy tracks like the DTS mix on War of the Worlds or even the DTS-HD Master Audio track on the Taken Blu-ray, the vibrating and buzzing coming from that decoration on the wall has severely been reduced and nearly eliminated, which leads me to my next question...

Is it possible moving the sub further from the wall is eliminating some "port chuffing" or has changed the aspect of the wave to the point the resonance area has altered? If so, was this a good move to rearrange the sub a bit further from the wall? The LFE now seems less pressurized and in-your-face than before (well, as best as this total POS sub could) and during Taken, the bass seemed tighter and better controlled, if my ears weren't tricking me...

How far should a sub be from a wall, ideally? It shouldn't be right up against the wall, or inches from it, should it?

 

[TLS Guy]

PSW350 SITUATION UPDATE:

Okay. Did an entire rewiring of my system last weekend to try and find the culprit of a buzzing/ground loop-like hum that ripped through my main speakers when I jiggled or moved the tangle of wires and cables behind the system and wall unit...I cleaned up all the wiring, bundling and separating power from interconnect and signal flow routes with cable ties, and in the process, I discovered something about the subwoofer situation we're discussing here...

My wall unit housing the system and TV had been moved out from its position nearly two or so feet so I could get to the back of everything for the rewire, and in so doing, I moved the sub off the wall a good few inches, maybe a half a foot or so. I also upped the sub calibration number one dB in the AVR's setup menu. Playing bass heavy tracks like the DTS mix on War of the Worlds or even the DTS-HD Master Audio track on the Taken Blu-ray, the vibrating and buzzing coming from that decoration on the wall has severely been reduced and nearly eliminated, which leads me to my next question...

Is it possible moving the sub further from the wall is eliminating some "port chuffing" or has changed the aspect of the wave to the point the resonance area has altered? If so, was this a good move to rearrange the sub a bit further from the wall? The LFE now seems less pressurized and in-your-face than before (well, as best as this total POS sub could) and during Taken, the bass seemed tighter and better controlled, if my ears weren't tricking me...

How far should a sub be from a wall, ideally? It shouldn't be right up against the wall, or inches from it, should it?

If the port is facing the wall, it should be away from the wall at least 10". with the amount of turbulence you describe, 14" would be better.

 

[j_garcia]

No, your sub should never be right next to the wall. In general, most speakers should not be close to nearby walls.

 

[Digi]

Subs aren't as prone to wall location variances as much as towers/surrounds due to mostly low frequencies they produce. Hsu actually recommends placing their sub (at least the VTF-15H) in the corner, which is how I have mine currently.

Ymmv, but with my current setup, speaker/ports are front facing and the unit is within inches of my wall. The sub is well isolated from the floor (and could be even more). Standing waves and oddball resonance may be highlighting the weakness of your general listening area. You may just want to turn the thing down a notch .

From the HSU Manual:
• Avoid the center of the room: In general, avoid placing the subwoofer half way between the front and back walls. This is where you get a strong null from your room’s standing waves. You should also avoid sitting in that area. No matter how powerful the subwoofer is, there will not be much bass around the center of the room.
• Use corner placement: Subwoofers usually sound best tucked in a corner. A good corner is far from wall divisions and has at least 6 feet of wall to either side. If you have more than one good corner, use the one farthest away from large room openings or the one closest to the listener. Keep the subwoofer within 1 foot of the wall.
• Use nearfield placement:A good subwoofer usually sounds best close to the listening position. As an added bonus, the subwoofer’s volume level will be lower so neighbors are less disturbed. We strongly recommend this method if your couch is up against the back wall and your room is over 18 feet deep.

No, your sub should never be right next to the wall. In general, most speakers should not be close to nearby walls.

 

[j_garcia]

Subs aren't as prone to wall location variances as much as towers/surrounds due to mostly low frequencies they produce. Hsu actually recommends placing their sub (at least the VTF-15H) in the corner, which is how I have mine currently.

Ymmv, but with my current setup, speaker/ports are front facing and the unit is within inches of my wall. The sub is well isolated from the floor (and could be even more). Standing waves and oddball resonance may be highlighting the weakness of your general listening area. You may just want to turn the thing down a notch .

From the HSU Manual:
• Avoid the center of the room: In general, avoid placing the subwoofer half way between the front and back walls. This is where you get a strong null from your room’s standing waves. You should also avoid sitting in that area. No matter how powerful the subwoofer is, there will not be much bass around the center of the room.
• Use corner placement: Subwoofers usually sound best tucked in a corner. A good corner is far from wall divisions and has at least 6 feet of wall to either side. If you have more than one good corner, use the one farthest away from large room openings or the one closest to the listener. Keep the subwoofer within 1 foot of the wall.
• Use nearfield placement:A good subwoofer usually sounds best close to the listening position. As an added bonus, the subwoofer’s volume level will be lower so neighbors are less disturbed. We strongly recommend this method if your couch is up against the back wall and your room is over 18 feet deep.

I mean right next to the wall as in within a few inches. Subs are less affected, but the behavior really depends on the rest of your room. In my old room, I sat just behind center of a nearly square room and my sub sounded best closer to the corner. In my current room, putting any of the subs I've tested in there except one, all sounded better when pulled away from the corner. So those are pretty general recommendations for people who are not going to pull out their SPL meter and see what is going on in their room I'd say.

 

[PearlcorderS701]

No, your sub should never be right next to the wall. In general, most speakers should not be close to nearby walls.

John,

So the sub shouldn't be nearly inches from a wall -- it is best to pull it around a half a foot or so as I did? Could this be why the resonance vibrations stopped?

And what about with regard to my RTi12 mains -- those are a good foot off the wall as well; is this okay for the tower main channels?

EDIT: I see that the recommended manufacturer instructions for placement, based on the clipping from that other member, is to have the sub at least a foot from the wall...

Did I read this right?

 

[PearlcorderS701]

If the port is facing the wall, it should be away from the wall at least 10". with the amount of turbulence you describe, 14" would be better.

Yes, the port is facing the wall -- this is, from what I understand, a front-firing sub, so shouldn't the port face the wall?

At least 10 inches from the wall?? Is this standard practice? Wouldn't 10 to 14 be too far for waves to develop?

But perhaps you're right -- I think moving it off the wall as I did helped in eliminating the rattling at that resonance point I was talking about in this thread...is that possible?

 

[Digi]

Of course, every room is different, but yes, within a foot from the wall, give or take a few inches depending on your layout should suffice. On my sub, all ports face the same way as the speaker unlike my speakers that have rear-facing ports. There's a lot of trial/error as no speaker was built for your room and subs aren't the easiest to move around.

Walls help direct sound waves which explains some of the other recommendations in Hsu's directions.

Yes, the port is facing the wall -- this is, from what I understand, a front-firing sub, so shouldn't the port face the wall?

At least 10 inches from the wall?? Is this standard practice? Wouldn't 10 to 14 be too far for waves to develop?

But perhaps you're right -- I think moving it off the wall as I did helped in eliminating the rattling at that resonance point I was talking about in this thread...is that possible?

 

[PearlcorderS701]

Of course, every room is different, but yes, within a foot from the wall, give or take a few inches depending on your layout should suffice. On my sub, all ports face the same way as the speaker unlike my speakers that have rear-facing ports. There's a lot of trial/error as no speaker was built for your room and subs aren't the easiest to move around.

Walls help direct sound waves which explains some of the other recommendations in Hsu's directions.

Thank you for your continued assistance, Digi.

That's a strange arrangement with regard to your sub -- on mine, the woofer is facing one side, out, and the port is to the back where the knobs and controls are...should I have this side facing the wall?

Thanks for confirming the distance for the sub from the wall; indeed, it seemed like some odd reflection or room hump was causing a nasty resonance point on a decoration -- since moving the sub away from the wall a bit more (not actually turning the volume down, as you suggested, amazingly) the rattling has stopped. I can't believe it, but that's what happened...

I suppose what I am asking is, is this remotely possible that this happened, or does it sound..."normal"?

What about large, floorstanding tower speakers and their relation to walls -- should they also not be right up against a wall? My Polk RTi12's are large towers that have those "Power Port" things in the back, but since doing my rewire recently, these speakers have been pulled off the main wall a good ways -- perhaps two or so feet. Is this okay for the main speakers to be so far from the wall, especially these which can produce more bass (reportedly) than my sub does?

 

[Digi]

For sure. Every room has its quirks and obstructions/standing waves/void areas, etc. It sounds looks like you've solved your issues. Using an SPL meter, you can find the sources of these if your ears aren't finding them .

Your towers can be moved out farther and you may gain some benefits. The rear ports aren't meant to be butted right up against the wall. The added distance you have may help in smoothing out the low-end response and give you a better balanced sound. You may also want to turn-in your towers some if they aren't already. AH has many articles about HT setup and advice. It just needs to sound good to you.

Thank you for your continued assistance, Digi.

That's a strange arrangement with regard to your sub -- on mine, the woofer is facing one side, out, and the port is to the back where the knobs and controls are...should I have this side facing the wall?

Thanks for confirming the distance for the sub from the wall; indeed, it seemed like some odd reflection or room hump was causing a nasty resonance point on a decoration -- since moving the sub away from the wall a bit more (not actually turning the volume down, as you suggested, amazingly) the rattling has stopped. I can't believe it, but that's what happened...

I suppose what I am asking is, is this remotely possible that this happened, or does it sound..."normal"?

What about large, floorstanding tower speakers and their relation to walls -- should they also not be right up against a wall? My Polk RTi12's are large towers that have those "Power Port" things in the back, but since doing my rewire recently, these speakers have been pulled off the main wall a good ways -- perhaps two or so feet. Is this okay for the main speakers to be so far from the wall, especially these which can produce more bass (reportedly) than my sub does?

 

[j_garcia]

Yes, the port is facing the wall -- this is, from what I understand, a front-firing sub, so shouldn't the port face the wall?

At least 10 inches from the wall?? Is this standard practice? Wouldn't 10 to 14 be too far for waves to develop?

Low frequency waves are FEET long. Down in 40s you are talking about something like 20-30 feet, so 10-14 inches certainly isn't going to let any waves set up. The port isn't really used to generate sound, it is to allow proper air movement inside the cabinet to create the tuning of that cabinet, but it needs to be unrestricted to work correctly. Right up against the wall isn't really unrestricted.

 

[PearlcorderS701]

For sure. Every room has its quirks and obstructions/standing waves/void areas, etc. It sounds looks like you've solved your issues. Using an SPL meter, you can find the sources of these if your ears aren't finding them .

Your towers can be moved out farther and you may gain some benefits. The rear ports aren't meant to be butted right up against the wall. The added distance you have may help in smoothing out the low-end response and give you a better balanced sound. You may also want to turn-in your towers some if they aren't already. AH has many articles about HT setup and advice. It just needs to sound good to you.

Thank you!

Indeed, I know about toe-in; it would probably benefit our room, but right now we have the towers flush straight against the ends of the wall unit for aesthetics in the room.

Let me ask you with regard to the ports of the towers out back -- if they aren't supposed to be right smack against the wall (well, or even a few more inches), how can the bass waves develop from them? As you said, though, pulling them away as I did may have made for a better balanced sound...

 

[PearlcorderS701]

Low frequency waves are FEET long. Down in 40s you are talking about something like 20-30 feet, so 10-14 inches certainly isn't going to let any waves set up. The port isn't really used to generate sound, it is to allow proper air movement inside the cabinet to create the tuning of that cabinet, but it needs to be unrestricted to work correctly. Right up against the wall isn't really unrestricted.

Could -- or should -- a sub be pulled 20 to 30 feet from a wall!? Or would this just be to deliver those ultra low 40s?

Thank you for the explanation regarding the cabinet and port.

 

[Theresa]

under sub dampening

I recently read of a DIY where a sandwich of "acoustic" foam dampening was placed underneath a sheet of "styrofoam" and the sub on top of that. Claimed to reduce resonances although I'd expect that it also reduced output slightly by back and forth movement on such a pliable surface. I intend to try it with my smaller sub as I want it the same height as the larger one.

 

[Theresa]

No, your sub should never be right next to the wall. In general, most speakers should not be close to nearby walls.

Actually, up against the wall is often the best place for a sub. For satellites or towers its better for imaging to be out away from the wall but this depends on how much baffle step compensation is used. This doesn't apply to subs though.

 

[highfigh]

Could -- or should -- a sub be pulled 20 to 30 feet from a wall!? Or would this just be to deliver those ultra low 40s?

Thank you for the explanation regarding the cabinet and port.

You may have seen references to a 'ModeCalc' download but if you haven't, google that and download it. This will tell you which frequencies will cause problems.

If you were to draw a single, complete sine wave on each wall (length and height) and on the ceiling/floor (length and width), you would be able to determine the frequency of the wave, based on the speed of sound. Where you or the speaker is, in relation to this wave, determines its affect on the sound. If you're sitting at the points where the wave passes through the center line, you're in a position where energy is at its lowest and if you're at a point where the wave is at it's maximum amplitude, that's where the sound's energy is highest. Any multiple of this wave will have an affect on the correct placement of your best listening position and speaker location.

When you moved the sub and speakers, you took them out of the locations that coincide with the frequencies that are at their maximum energy.

 

[PearlcorderS701]

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.

 

[Pyrrho]

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.

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.

Here is a case in point:

http://www.audioholics.com/tweaks/speaker-setup-guidelines/subwoofer-placement-guidelines

And an interesting quote:

The worst place for a subwoofer is in the middle of a room.​

I don't know of any reputable source that claims otherwise. In fact, I don't know of any disreputable sources claiming otherwise, either.