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Bass disappears in all seated positions

post #1 of 44
Thread Starter 

Hi everyone, I'm new here and this is my first post but I have been into HT for the last few years and have been slowly building up my primary HT which is located in the basement and which is also a man cave. I have been pouring through all the information in this forum for weeks and I have to say that it has been a great education. After reading through the threads on subwoofer positioning and good bass I realized that my seating position may be less than good. So I started to move around the room with some heavy bass tracks playing and to my dismay found that my primary seating position was the worst place for bass. 

 

I sit in the center of the room (length wise). I just recently learned that this is a bad spot to sit. No problem, I can move forward a foot or two but the problem is, that doesn't seem to be my only issue. What I found out is that in every seated position around the room the bass disappears, but it is strong in a lot of standing positions. It is especially good two feet in front and a foot off to either side of my sofa (the primary listening position). When I say it's good I mean it's good as long as I am standing.

 

I did some searches to see if there were any threads on the subject of bad bass in seated positions but I didn't see any. If there are any out there I apologize for starting this one. But my question is: has anyone run into this problem before? I really don't plan on standing up for movies or music listening.

 

Here is some information that might be helpful:

I have a Denon 3313CI running a 7.2 system with an infinity Alpha 1200 and an infinity CSW 10 as my subwoofers (I am also looking to upgrade my subs but want to figure this out before I drop the money on new subwoofers). 

 

My room is a rectangle of about 3250 cu ft with a single hallway running off to one side. 

 

I just can't figure out why the best bass seems to be floating around at about 6 feet in the air.

 

Any help is greatly appreciated. Thanks.

post #2 of 44
Put the subwoofer in the listening position and walk around the room. Wherever you hear the bass is strongest is where the sub should be placed.
post #3 of 44
Quote:
Originally Posted by Jon S View Post

Put the subwoofer in the listening position and walk around the room. Wherever you hear the bass is strongest is where the sub should be placed.

Make that crawl.
post #4 of 44
Ditto on the sub crawl. Sounds like you have a null, are you sitting in the middle of the room? You can also get into REW or Omnimic to do freq sweeps and get some graphs of your room. I am new to omnimic as I have just purchased one. Also I would say that you may think of adding another sub or going with bigger dual subs. Now that you have joined AVS, be prepared to spend all your money as we will help assist you in upgrade and help you go broke. biggrin.gif
post #5 of 44
Thread Starter 

Lol Reefdvr, I'm sure you guys will be happy to help me spend any extra money I may have. I better not let my wife see any of this. It sounds like the first thing I should do asap is the bass crawl. I may have to do that tomorrow if I can get a chance.

 

I am planning on getting more powerful subwoofers in the next month or so as well. Right now I'm leaning strongly towards PSA XV15. I Plan on starting with one and then if i find need more bass adding a second one. I looked at the XV30s that they have in outlet but I really don't have a great place for something that size. I have also looked at SVS PB12-NSD or HSU VTF-MK4. They all seem like they would work pretty well to pressurize my room. If anyone has any thoughts which way to go with any of those companies I would love to hear them. 

 

To sum up I am leaning towards the PSA XV15 but am also considering the offerings from SVS and HSU. I think the Rythmik FV15hp is out of my budget. Is there anything else out there that would compare to these listed that I'm missing?

post #6 of 44
Quote:
Originally Posted by Hopinater View Post

Lol Reefdvr, I'm sure you guys will be happy to help me spend any extra money I may have. I better not let my wife see any of this. It sounds like the first thing I should do asap is the bass crawl. I may have to do that tomorrow if I can get a chance.

I am planning on getting more powerful subwoofers in the next month or so as well. Right now I'm leaning strongly towards PSA XV15. I Plan on starting with one and then if i find need more bass adding a second one. I looked at the XV30s that they have in outlet but I really don't have a great place for something that size. I have also looked at SVS PB12-NSD or HSU VTF-MK4. They all seem like they would work pretty well to pressurize my room. If anyone has any thoughts which way to go with any of those companies I would love to hear them. 

To sum up I am leaning towards the PSA XV15 but am also considering the offerings from SVS and HSU. I think the Rythmik FV15hp is out of my budget. Is there anything else out there that would compare to these listed that I'm missing?
I sent you a PM

IMO PSA is one of the best companies to deal with ever. Tom and Jim are two of the best guys in the business and they will go the extra mile to help you. I am on my third set of subs from PSA and plan on many more down the road. Email Tom at PSA and I am sure you will be very pleased at the customer service you get. PSA subs are also top notch. They have a sub to fit anybody's needs. Just quality all around the board.
post #7 of 44
Well, I wonder if vertical modes can be easily solved by sub crawling--how often does a crawl result in a change to the sub's elevation?

Conversely if the sub's elevation isn't changed, then how likely is it that his vertical modes will be affected by the crawl?

I also noticed a huge difference between standing and seated bass in one of my systems a long time ago--it's present regardless of any sub position that's available. It's not terrible because there's still plenty of bass when seated; just notably less. Has anyone specifically tried to adjust for vertical modes? How many of you guys put your subs on risers?
post #8 of 44
Thread Starter 

That's the same question that was running through my mind, has anyone tried putting their sub on a riser to get rid of vertical dead areas for bass?

post #9 of 44
Your Bass may be out of phase.
Check your wiring.
If it sounds like it is flouting and not centered it is wired out of phase.
Change the polarity and them it will be fine.
Edited by dr.sound - 10/29/13 at 12:08pm
post #10 of 44
Thread Starter 

thanks dr. sound, I checked my subwoofers and one was out of phase with the other. This seemed to balance it out better. I still have more bass in a standing position but it is not as bad as it was, so I'm a little closer to solving the problem. I still haven't been able to do the bass crawl yet so I'm hoping that solves the rest of the problem but the phase issue seems to have helped some. 

post #11 of 44
Thread Starter 

If I do the sub crawl with my current subwoofers will I need to do it again when I order the new subwoofers? Or is the right placement for one subwoofer the right placement for all subwoofers? Remember I plan on going from the current Infinitys to PSA XV15 (or maybe something similar but I am heavily leaning towards PSA).

post #12 of 44
Once you find the optimal position for the subs, it will not change if you buy new subs unless the room changes (furniture add/moved/removed, flooring changes or wall tratmentss)...
post #13 of 44
Quote:
Originally Posted by Hopinater View Post

I sit in the center of the room (length wise). I just recently learned that this is a bad spot to sit. No problem, I can move forward a foot or two
A foot or two will probably make little to no difference. The number one cancellation null issue is the distance from the LP to the wall in the rear of the room. If that distance is 1/4 wavelength in the sub passband you'll get a huge dip at that frequency. That 1/4 wavelength range from 25 to 80Hz is 3.5 to 11 feet. The easiest way to eliminate that dip is not to have the LP within that zone. Adding a sub at the rear of the room is the next best method.
post #14 of 44
Quote:
Originally Posted by Bill Fitzmaurice View Post

A foot or two will probably make little to no difference. The number one cancellation null issue is the distance from the LP to the wall in the rear of the room. If that distance is 1/4 wavelength in the sub passband you'll get a huge dip at that frequency. That 1/4 wavelength range from 25 to 80Hz is 3.5 to 11 feet. The easiest way to eliminate that dip is not to have the LP within that zone. Adding a sub at the rear of the room is the next best method.
Thanks for the simple explanation, Bill smile.gif

I will have to get my tape measure out tonight! lol

I'm guessing we're pretty screwed regarding nulls under 25Hz because the 1/4 wavelengths get so long that you'd require a hugely long room? but that Room Gain should have kicked in nicely by then?
post #15 of 44
Quote:
Originally Posted by MemX View Post

I'm guessing we're pretty screwed regarding nulls under 25Hz because the 1/4 wavelengths get so long that you'd require a hugely long room? but that Room Gain should have kicked in nicely by then?
The opposite. If the room is so large that the distance from the LP to the wall behind the LP is in excess of 11 feet or so then the room is probably too large to get much, if any, cabin gain.
post #16 of 44
Quote:
Originally Posted by Bill Fitzmaurice View Post

A foot or two will probably make little to no difference. The number one cancellation null issue is the distance from the LP to the wall in the rear of the room. If that distance is 1/4 wavelength in the sub passband you'll get a huge dip at that frequency. That 1/4 wavelength range from 25 to 80Hz is 3.5 to 11 feet. The easiest way to eliminate that dip is not to have the LP within that zone. Adding a sub at the rear of the room is the next best method.
My room length is about 19' and I believe my HT seats are about 4' to the back wall. Are you saying, I might have a better bass from 25-80Hz if I move the seats closer to the back wall, say 2 or 3 feet from it? What about 25Hz and lower? My sub is currently located in the front wall. Thanks.
post #17 of 44
Quote:
Originally Posted by Cowboys View Post

My room length is about 19' and I believe my HT seats are about 4' to the back wall. Are you saying, I might have a better bass from 25-80Hz if I move the seats closer to the back wall, say 2 or 3 feet from it? What about 25Hz and lower? My sub is currently located in the front wall. Thanks.
Four feet to the back wall places your null around 70Hz. There's an awful lot of bass energy there. Below that frequency any deficiency isn't the fault of the reflection off the back wall.
post #18 of 44
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post


A foot or two will probably make little to no difference. The number one cancellation null issue is the distance from the LP to the wall in the rear of the room. If that distance is 1/4 wavelength in the sub passband you'll get a huge dip at that frequency. That 1/4 wavelength range from 25 to 80Hz is 3.5 to 11 feet. The easiest way to eliminate that dip is not to have the LP within that zone. Adding a sub at the rear of the room is the next best method.

Bill, my LP is just at 11' from the back wall but I as I said I can easily move forward a foot or two putting my rear wall to 12 ft or so. I know above you say a foot or two won't make much difference but does that hold true as you are coming out of that dreaded 3.5 to 11 ft range? If not, how much farther away from 11 feet would I have to move before I found the right spot (in theory, I know that you can't say specifically for my room set up).

post #19 of 44
Quote:
Originally Posted by Hopinater View Post

Bill, my LP is just at 11' from the back wall but I as I said I can easily move forward a foot or two putting my rear wall to 12 ft or so. I know above you say a foot or two won't make much difference but does that hold true as you are coming out of that dreaded 3.5 to 11 ft range? If not, how much farther away from 11 feet would I have to move before I found the right spot (in theory, I know that you can't say specifically for my room set up).
Use this to find the cancellation frequency based on the distance from the LP to the rear wall:
http://www.padrick.net/LiveSound/CancellationMode.htm
post #20 of 44
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post


Use this to find the cancellation frequency based on the distance from the LP to the rear wall:
http://www.padrick.net/LiveSound/CancellationMode.htm

Thank you

post #21 of 44
Quote:
Originally Posted by MemX View Post

Thanks for the simple explanation, Bill smile.gif

I will have to get my tape measure out tonight! lol

I'm guessing we're pretty screwed regarding nulls under 25Hz because the 1/4 wavelengths get so long that you'd require a hugely long room? but that Room Gain should have kicked in nicely by then?
Quote:
Originally Posted by Bill Fitzmaurice View Post

The opposite. If the room is so large that the distance from the LP to the wall behind the LP is in excess of 11 feet or so then the room is probably too large to get much, if any, cabin gain.

D'oh, of course! Apologies, that was a silly question :facepalm: lol


I measured up last night before bed. The centre point of my sofa is 9' from where the front wall and subs are, and also 9' from the rear wall. I'm guessing that this is not ideal...

Going from that table, if I'm reading it correctly, if the subs are on the front wall and the rear wall is 18' away, that makes around 16Hz a major null across the room? And because I'm sitting bang in the middle of the room, it makes it even worse? (because of the standing wave null?)

And 32Hz-ish is a room mode so will be a bit boomy?


Gnargh, I need more sleep so I can get this clear in my head...
post #22 of 44
Quote:
Originally Posted by MemX View Post

Going from that table, if I'm reading it correctly, if the subs are on the front wall and the rear wall is 18' away, that makes around 16Hz a major null across the room? ...
It's the nine feet from the LP to the rear wall that's a problem. The initial wave passes you, reflects off the rear wall, and reaches your ears again 180 degrees out of phase at 31hz, give or take. A null related to the sub position would be based on how far it is from the front wall, and the side walls and the ceiling. There's also the matter of how far the LP is from the side walls and ceiling. The number one enemy of good bass is symmetry, not only with sub placement but also LP placement. Making a few deep nulls into a lot of smaller nulls is the cure, and that starts with not having both subs up front, or equidistant from the side walls.
post #23 of 44
Thanks Bill smile.gif

I think I am screwed with regard to placement frown.gif I only really have one place to put subs in my room, and as it's a all-in-one lounge/kitchen/diner there's only really certain layouts that work, with the sofa pretty much right in the middle!

I think I will look at moving it perhaps a foot or so back/forwards - that should hopefully move it slightly out of the null...

It still sounds alright, it's just that I have monster bass in the rear corners and less in the middle of the room!


I guess the other option is a wall of bass trap foam on the rear wall, although that might be a bit overkill and not please the missus... lol
post #24 of 44
Quote:
Originally Posted by MemX View Post

I guess the other option is a wall of bass trap foam on the rear wall, although that might be a bit overkill and not please the missus... lol
Most 'bass traps' are inaccurately named, as they trap midbass. To effectively damp below 80Hz a trap would have to be high density, at least six inches thick. What your observations should be telling you is that the bass is there, just not where you want it. You can't change the laws of acoustics, so to have the sound you want you must change your sub and/or LP placement, or live with what you have.
post #25 of 44
Dammit, the truth not the answer I want to hear tongue.gif lol

I will measure up my room properly at the weekend and then see if I can improve things by moving furniture wink.gif
post #26 of 44
Thread Starter 
Quote:
Originally Posted by MemX View Post

Dammit, the truth not the answer I want to hear tongue.gif lol

I will measure up my room properly at the weekend and then see if I can improve things by moving furniture wink.gif

Memx what subs are you running? I'll tell you why I ask:

 

When I started this thread I thought I was screwed as well with placement of subs and LP. It seemed my bass was only good if I stood up in a certain spot. So I took the advice given here and did the sub crawl to locate the best place for subs and discovered that one of my subs was in the worst location it could be. But the other one was in a great spot. So I co-located the subs to the that spot and sure enough I had good bass, but still not what I wanted. Then I learned that even the two subs I had were a bit small for my size room. So I ordered the PSA XV15 and replaced my two weaker subs with it. Now I'm happy. I have great bass. I watched World War Z yesterday and was blown away with the bass. I do plan on ordering a second one to smooth out the room and get better bass in more LPs but I need to save up for that.

 

I don't know if any of this may apply to your situation but I thought I would share my experience.

post #27 of 44
Hey Hopinater smile.gif

I currently have a SVS PB12-Plus/2 which I'm fairly happy with smile.gif I am hopefully moving to a more substantial dual DIY setup soon wink.gif but it has been a slow process! lol

My main issue is that my room only really works in one arrangement. I might have to move the sofa forward a bit, meaning it's not the same distance from the front and back walls, but the sub(s) can only really go in one alcove, at the front of the room, behind the telly. I could perhaps attempt to split the duals up when they are built, in an attempt to reduce standing wave cancellations/nulls, but realistically I think I will have to stack them in the one position! frown.gif I've not been too unhappy with the current one sub/position arrangement, and Audyssey XT32 seems to have set the in-receiver LFE channel to -4 so I must still be getting a reasonable amount of bass, but it's the "what if..." factor that is enticing!

That said, nothing is impossible - I will have to measure all my furniture up and see if I can find a second location... (The missus will hate me - she knows I am getting a replacement for the noisy box in the corner but I don't think she appreciates what yet wink.gifbiggrin.gif LoL)
post #28 of 44
Thread Starter 

Hey men x.

 

Lol, my wife looks at me like I'm crazy when I talk about bass and subwoofers (which I do a lot). :D

 

I can relate to your situation and finding the right spot. Then the ever nagging question of "what if I do this or move that?" I guess it's the never ending quest for the perfect bass. I read somewhere here in the forums that perfect bass is a journey, not a destination. I believe it.

 

Let the journey continue!

post #29 of 44
Haha I think you're right! biggrin.gif

A slow tumble down a slippery slope may be even more accurate! tongue.gif
Edited by MemX - 11/14/13 at 3:50pm
post #30 of 44
Thread Starter 
Quote:
Originally Posted by MemX View Post

Haha I think you're right! biggrin.gif

A slow tumble down a slippery slope may be even more accurate! tongue.gif

True, very true.

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