Bass Traps: Do they fix this common problem?

[dtximages]

Ive read all on here about room modes, nodes, null spots, dead spots etc.. I want to make SURE bass traps will fix my problem. Let me describe.

Front speakers: Chorus II & Forte II stacked for diappolito (ms?) design

Center: Forte I

Rear: Quartet

SUB: Velodyne HGS 18

Listening Position: Middle of speakers, about 3/4 of the way back. (22ft front wall to rear wall)

So im used to hearing these bad boys pump out the noise with bass and kick that will move you. However, i rearanged and built a HT in my basement and my primary viewing position sits right in a dead spot for bass. I used the old trick of putting your sub in your seat and walking around the room to find the "best" sub placement. DID NOT WORK. So i tried several different locations. my listening/viewing position is DEAD. Move your head forward or back 2 feet and bass is deep and powerful. my primary position is the deadest in the room. So, im hoping that bass traps in the rear corners (floor to ceiling) will cause my dead spot to become alive again! Since i have huge cool speakers, im thinking something big like the megalenrd from auralex would be my best bet. I hear that the regular lenrds are no good below 50hz and my sub pumps out plenty below that frequency.

Anyway, am i right to assume that bass traps would solve my problem?

Please help before i go blow $400 or more on this.

Thanks guys

Home Theater Diminsions.pdf

[mark1101]

I know next to nothing about this but bass traps absorb / remove bass. Why are you considering them? If you want to reflect bass into your seating position you probably need something reflective.

[dtximages]

Well, I paid like $3500 for the sub but i dont like it. i could get rid of it, but its heavy. i could turn it down but i dont wanna get up.. so ill just buy some bass traps and trap all my bass in.. plus they look cool.

HHAHHA just kidding. Sorry Mark1101 i couldnt resist. Its almost 3pm and im getting ready to leave work for the weekend so i decided to be smart.

anyway, Bass traps to not effect the original bass wave because it hits your ear first. They will however, "trap" the wave after it has passed your hear. This means that the wave will not bounce back and cancel itself out. For me, the bass wave reflection is cancelling itself out. I want to catch it with the trap. Thats my alabama explaination hahaha. The effect should be removing most room dead spots and smoothing the bass response making it more natural sounding.. hopefully less boomy as my walls are concrete brick and contrete foor with some rugs.

[Groomlakearea51]

Change the angle of attack or the axis of the front outer speakers to 60 degrees, so the imaginary "on axis" line from the speakers intersects in front of you, then try it to intersect behind you, etc.

What is the size of the room? Is it "equal" sides?

Bass traps..... Extremely simple version. Bass "collects" in the corners. Without getting overly technical, you may be in a position where you've got cancellation due to the reflections. Just for the heck of it, make four "triangles" about 24" on each side out of some styrofoam board about 1" thick, and stick them in the corners up next to the ceiling at about a 45 degree angle, with the sides of the styrofoam up against the walls and the ceiling. You will have to use a long picture hook on the center of the backs of the triangles and a picture hook up un the corner. Use a very light duty bungee to connect and pull tight into the corners.

Then hang a rug or something in the middle of your back wall (temporary) and see what happens.

Send a PM to MAS or Dr. Who. They can help you alot more.

[PrestonTom]

Well, It is not actually clear what the specific problem is. So until then hang onto your checkbook and take all advice with a grain of salt.

My guess (from your comments so far)

If the bass is strong in some positions but not in other positions, then you may be having problems with room nodes (most probably). This is certainly not uncommon and if it is a low frequency (and you may be using the term "low" differently than me) then a bass trap is useful. If it is very strong then a Helmholtz (resonator) trap could be the answer. However, it is not so simple, do not try the later solution unless you know what the troublesome frequency is. The Helmholtz solution is quite frequency specific, and would require some measurement ahead of time (otherwise do not bother). The measurement need not be terribly expensive. Guess-ti-mating from room dimensions will probably not be close enough.

A broader band solution could use the the triangular wedges as described above. However, do not use Styrofoam!. The material of choice is compressed (semi-rigid) fiberglass. Styrofoam will not work. This is most effective if placed in corners (the deeper the better) and may require multiple locations.

If it is a truely low frequency (big wavelength), then a rug on the on the wall will target a fequency range well-above the bandwidth of the sub-woofer (although it may change other room interactions - at a few/several octaves above - and not necessarily for the better)

Search previous threads (here and Audio Asylum). There are DIY solutions.

Good Luck,

-Tom

[Groomlakearea51]

P.Tom is right; the use of the 2" styrofoam only indicates that the problem may be corner issues. I'm using it as a low volume test and if I start getting "loud", the effect becomes negligible. The "wedges" need to be at least 2" thick and be covered with some cloth (I used some scrap carpet, which probably does more than the styro).. The room being "tested" will eventually get some of the Roxul Rockboard 60 when it arrives for the other "man cave" room.

You should also seriously consider getting ahold of, borrowing, etc. some testing equipment to really find out the problem. I'm a "tinkerer" on alot of this stuff and like to try things, but when all's said and done, until I measure the "man cave" (under construction) I really cannot predict what I'll have to do.

[djk]

Tube traps are too broad, and don't work down low.

These work well, about $600 a pair.

Available in 63hz, 71hz, and 80hz, for 9', 8', and 7' ceilings.

http://www.rpginc.com/products/modexcorner/index.htm

[mas]

Ive read all on here about room modes, nodes, null spots, dead spots etc.. I want to make SURE bass traps will fix my problem.

Listening Position: Middle of speakers, about 3/4 of the way back. (22ft front wall to rear wall)

So im used to hearing these bad boys pump out the noise with bass and kick that will move you. However, i rearanged and built a HT in my basement and my primary viewing position sits right in a dead spot for bass. I used the old trick of putting your sub in your seat and walking around the room to find the "best" sub placement. DID NOT WORK. So i tried several different locations. my listening/viewing position is DEAD. Move your head forward or back 2 feet and bass is deep and powerful. my primary position is the deadest in the room. So, im hoping that bass traps in the rear corners (floor to ceiling) will cause my dead spot to become alive again! Since i have huge cool speakers, im thinking something big like the megalenrd from auralex would be my best bet. I hear that the regular lenrds are no good below 50hz and my sub pumps out plenty below that frequency.

i could turn it down but i dont wanna get up..

Several mixed issues masquerading as one...

. Let me try to address them rather quickly without the 6 page discourse. Besides, you have read most of them anyway... ;-))

So let's deal with the simple issue first. Room modes and excessive

boominess.

First, you are mentioning methods used to reduce the room mode peak resonance and the resultant boominess. I am going to generalize and say that just about every room has this problem,...it's a

function of the room geometry and not your system. And you are certainly on the right track in wanting to address this issue with traps.

But, the LENRDS do not even get close to 50hz! They are pretty useless below 200Hz. I don't care what the specs say. They are simply far too small for the wavelengths involved.

And if you are looking at MegaLENRDS, you are looking at well over a grand for a simple room. Allot to pay for a trendy color.

I would start with corner traps consisting of Roxul Rockboard 60 with stacked wedges cut from diagonally cut 2x2' pieces hidden by stretched open weave material..

Beyond this there are a variety of resonant panel traps and various Helmholtz resonators, which are all narrow (high) Q devices and not broadband LF devices. And if you are going to deal with any of these or the the binary absorptive/diffusive panels from RPG and spend the money involved, I would definitely first take measurements!

So, back to your problem. And thus far, while we have mentioned the problem with room modes and the solutions heretofore proposed, we still haven't covered your problem.

And here is the problem.

You are in affect trying to address 2 separate problems with one simple solution.

First, you are looking at solutions for mode peak resonance - bass boominess.

But you are complaining about a null. And traps will NOT restore a null.

While they (room modes and peak resonance and nulls) are aspects of the same phenomena, they are not the same thing. Nulls are determined by the room geometry.

Traps are NOT going to help you a bit with this. And the only thing that will 'resolve' nulls (meaning 'move them') are 'obstacles that are large relative to the wavelength. Think BIG partitions - like walls! - which are not very practical. While we can damp resonances, we cannot damp nulls in a 'positive' manner.

In this case, without resorting to extravagant solutions, you don't have much choice other than moving your listening position.

The only other technique that might work is to locate the sub sufficiently near the seating such that the direct signal precedence is dominant over the room reinforced null. Experimentation would be the rule here.

Note: But what really confuses me is the comment that you don't want to get up to turn the sub down... It has a remote volume control!!!

[Fast1]

Ive read all on here about room modes, nodes, null spots, dead spots etc.. I want to make SURE bass traps will fix my problem. Let me describe.

Front speakers: Chorus II & Forte II stacked for diappolito (ms?) design

Center: Forte I

Rear: Quartet

SUB: Velodyne HGS 18

Listening Position: Middle of speakers, about 3/4 of the way back. (22ft front wall to rear wall)

So im used to hearing these bad boys pump out the noise with bass and kick that will move you. However, i rearanged and built a HT in my basement and my primary viewing position sits right in a dead spot for bass. I used the old trick of putting your sub in your seat and walking around the room to find the "best" sub placement. DID NOT WORK. So i tried several different locations. my listening/viewing position is DEAD. Move your head forward or back 2 feet and bass is deep and powerful. my primary position is the deadest in the room. So, im hoping that bass traps in the rear corners (floor to ceiling) will cause my dead spot to become alive again! Since i have huge cool speakers, im thinking something big like the megalenrd from auralex would be my best bet. I hear that the regular lenrds are no good below 50hz and my sub pumps out plenty below that frequency.

Anyway, am i right to assume that bass traps would solve my problem?

Please help before i go blow $400 or more on this.

Thanks guys

I am really curious as to why you want to get rid of your Velodyne?? What don't you like about it? I have one but have not heard any other 18s to compare to. I am looking to compliment it with another HGS15 for more punch. Just curious.

[dtximages]

Haha ok first. thanks for all of your ideas. i really liked my fantasy of the megalenrds solving all of my problems in life though but i understand its not that simple. I thought the megalenrds would control down to 50hz etc. i also though these bass traps would not allow that reflected wave to cancel my original wave.. therefore, it would remove my null spot.

clarifying points:

1. my single problem is a dead spot. no bass at my listening position. move fwd or back and you have bass (not the greatest sounding bass but i can deal with that later). i want the dead spot GONE.

2. my velodyne remote does not work anymore

3. i was kidding about selling the velodyne in response to the second post. however, im reading alot of terrible things about their customer service and amp failure. mine has started popping and velodyne has already replaced the amp once.. this time its gonna cost big time and im not happy. im looking for better alternatives.

ANYWAY@!!!! I know that a rug or something similar will do nothing for a large bass wave, so i need somethingthat will work.. moving my listening position is not very practical.. i have a 126" carada screen that i want to be "prime" distance from. check out the pics at www.myspace.com/crokrokitman

thanks

[dtximages]

Hey what do you mean when you say,

"I would start with corner traps consisting of Roxul Rockboard 60 with stacked wedges cut from diagonally cut 2x2' pieces hidden by stretched open weave material.. "

Can you please be more specific? Im all about saving money. Ill post pics of the room when i get a chance.

[Fast1]

NOw you have me worried about my Velodyne crashing. To this day, it has run flawlessly and I do nothing but torment it. Mine is the Older but yet, identical FSR18 with the piano finish. Any ideas what is failing and if it can be curbed in any way? Does it cause speaker failure when it happens?

[dtximages]

well ive never researched it until i recently listened to my hgs18 by itself and it popped really loud when a deep or loud note hit (note: im not talking about excessive levels). this should NEVER happen as i never increase the volume past 00db or half way up on my sub plus its servo should never allow audible distortion... ANYWAY, i started to read forums and this is a very common problem with the hgs subs (maybe others as well). all i have heard was the price to fix, and the problem reoccurs every couple years and velodyne is pretty much silent on the issue. i freakin LOVE this sub but were having our differences right now.

i think i can actually see my pants leg move with this sub (well not in my current listening position which is a BBH (bass black hole).

[dtximages]

This is my first attempt to attach a file.. This is a quick pdf blueprint of my room. more info:

ceiling: straight up flooring with 2x10s exposed no insulation painted black. its the underflooring of the second floor if you will.

right and rear wall: concrete brick with texture

floor: concrete slab painted black with three shag rugs in the middle.

ok lets try the attachment:

Home Theater Diminsions.pdf

[mas]

You will hate me for this,but you did ask!

The first change I would definitely make (if at all
possible!!!) would be to flip the room and put the alcove at the rear
with the front of the theater at the narrow 15' end. The asymmetrical front
end is going to wreak havoc in a number of ways, beginning with
imaging. And the alcove is going to act as a prominant coupled space.

Where is the subwoofer located?

[Hemihorn]

Do your homework before you spend your money. I have included

links to what I think will help solve your problem. Please look and read through

them and jot down notes that you think are pertinent to your problem. I had

basement rooms in the past and it was a lot of work to get good sound out of

them I attribute that to room dimensions low ceiling. It is always easier to

get good sound when you start of with ideal room dimensions. Ideal dimension

are not always possible so you have to compensate with room treatments .It

sounds to me your sitting in a null this is just my assumption with the little

information you gave about your room. I think your on the right track as far as

bass traps read about bass traps in this link http://www.ethanwiner.com/acoustics.html

The other thing I think is pertinent to your problem is the 38% rule read link.

http://www.realtraps.com/art_room-setup.htm

The other thing I tried your diappolito stacked configuration I didnt like it to

because it causes a blurred point source and bloated bass. Well here is bunch

of links a lot of good reading easy to understand and I like the approach Ethan

Winer takes on room Acoustics.

http://www.ethanwiner.com/acoustics.html

http://www.realtraps.com/art_room-setup.htm'>http://www.realtraps.com/art_room-setup.htm

http://www.realtraps.com/videos.htm'>http://www.realtraps.com/videos.htm

http://www.realtraps.com/

[Fast1]

well ive never researched it until i recently listened to my hgs18 by itself and it popped really loud when a deep or loud note hit (note: im not talking about excessive levels). this should NEVER happen as i never increase the volume past 00db or half way up on my sub plus its servo should never allow audible distortion... ANYWAY, i started to read forums and this is a very common problem with the hgs subs (maybe others as well). all i have heard was the price to fix, and the problem reoccurs every couple years and velodyne is pretty much silent on the issue. i freakin LOVE this sub but were having our differences right now.

i think i can actually see my pants leg move with this sub (well not in my current listening position which is a BBH (bass black hole).

You know, the very first day I got the 18, it started doing that and I called the guy at Velodyne. He said the gain was just too high on the amp and the speaker was trying to over-travel and the servo was doing it's job. I pulled the gain down to maybe a 1/4 and it does not happen anymore. I am very observant of that though and understand it can blow things up. The subs dbs seem to fall off anyway so I don't think I am sacrificing output (I hope). I could sure be happier with things below 30hz though. Maybe 2 18s will get the job done. I am also sitting on a subfloor with a crawl space and not in a corner with the sub so that might be hurting me a bit. I am suffering the same problems as you with dead zones in the bass. I will not be in this house much longer so not too worried I guess.

[dtximages]

Brandon, if youre sitting on a subfloor with the HGS18 you should be PLENTY satisfied with the sub30hz response. that sub will dig. turning down the gain is not what i want to hear from velodyne. i dont push mine anywhere near its limits and it sounds like the voice coil is slamming the back of the magnet. regualar bass still sounds good and is not scratchy... weird////

anyway, my sub is placed in between my center and right speaker in front. under the screen. i looked into many different placements.. same dead spot. move my listening position front or back 1.5 to 2 feet and you have tons of bass. i was hoping to hear more positive things about bass traps.

ok flipping my room, youre right i dindt want to hear that haha. now you have me wasting more work time drawing out new plans! i think ill move the main speakers over there and see if music sounds good.

Thanks for all the links.. ill try to gravel through them soon. theyre gonna give me a huge headache i know!

ok SO, BASS TRAPS WONT FIX MY LIFE??????? EVEN BIG ONES? I thought they were meant to smooth out bass and stop the the reflected bass wave thats cancelling my good wave out. is that just good theory and doenst really work?

[Fast1]

You are fighting near the same problems as me and with a similar room setup. Just walking the room, you can hear the standing waves in the corners very bad. I would NOT say I have TOO much bass at 30hz and everyone tells me it should just about hurt with my sqft and setup. The windows shake but that is about it. I am convinced I have some serious wave cancelations in the room. My 18 runs clean up to where I think it gives up. I can see that woofer going for it but I don't think the sound in the room matches the work it is doing.

I really think an SPL meter can really help. I never bought one but will soon. The way I look at it, if I can determine exactly what freqs are in the dip, I can study the dynamics of the room and figure out what is causing the dip. It is also needed to properly tune an HGS with an EQ.

I know the dead spot you are talking about and had to rework my room for that reason. Dead spot right on top of the Lazy Boy ain't cool!!! I see that as a pure learning experience in modes and nodes I guess. I plan to take my HGS to my brothers theater that we designed to see if it will work better with our theoretically sound improved room. If it lifts his roof, then I know it is just my piss poor room.

[dtximages]

Yeah. im not sure an spl meter would help me now.. i think it would just confirm what i DONT hear. i find it hard to believe that the hgs is lacking in any bass frequency. ive had mine in a number of rooms and situations, its never let me down one time.. i usually walk away proud that my frineds cant TOUCH my bass! hahaha

im scared to death that im going to have to rearrange my room.. its not easy to fit a 126" screen. im confident that some kinda room treatments will lend an incredible listening experience.. however, ive already dumped soooo much money into this room.. im attaching some pics (hopfully).