Chairs into Bass traps???? Bass trap on ceiling???

[Krazykaj]

Hi,

I am trying to figure out where I can place some sort of bass-traps or low frequency absorption, acoustic dampening etc. in my room without taking up to much space.

First . . . I was vacuuming under our sofas the other day and saw that they are virtually hollow.
I was wondering, especially for those of you who know their stuff about acoustics and how sound travels (especially Low frequency stuff) etc. . . .
Is there a way I can maybe fill the inside of the chairs with something (foam, fibreglass) and convert them into some sort of bass trap, or sound absorber?

There is a lot of wasted space there, and it would be great to convert it into something useful
Or would this not work very well, or not work at all?
Do bass traps need to be on the side walls, or in corners of the room to be most effective? Is it useless if they are in the middle, especially inside a chair?

My second question, regarding another possible placement position for some sort of acoustic treatment is . . .

My room is sort of strange, down the middle on the right-hand wall and across the ceiling in the middle; I have two protruding boxes that are hiding supporting pillars and beams.
Also, the front part of my room is not as high as my back half. See the attached pics for more detail.

Would it be effective to stick some sort of bass traps in the corners along the ceiling and along the right wall, where these boxes are sticking out?
SEE THE PICTURES (proposed traps in Blue)
If I do it in the corners that are facing the TV, no one will really see it unless you go into the front half of the room.

Or again, would this not be very effective?
Especially the one on the ceiling?
Would I realise little effect at my listening position?

Comments/suggestions most appreciated


Thankyou
KJ

(NOTE: The pics are not to scale
The First Pic is a side view from the right
The Second Pic is a top view)

 

[Rob Babcock]

I suppose your plan couldn't hurt, but the problem is that bass traps are most effective near room boundries. Plunking them down in the middle of the room may help somewhat but isn't likely to be as effective at low frequencies than if they were placed on/near the walls.

The ceiling, on the other hand, seems to be a good option, provided you can get them hung okay. Especially at the wall/ceiling boundary.

 

[tbewick]

I really can't see how you can expect to get that much improvement by playing around with things like bass traps. If your having trouble with boomy sound, try:

1) Moving your sub away from the room's corner.
2) Move your speakers further away from the room walls.
3) Move your speakers so that they're closer to you.

Looking at your configuration, I'd suggest you sit closer to the front speakers. Ideally, you'd place all your speakers (not sub) equidistant from your central listening position, with the rear-surrounds as far apart as possible. According to the THX guide on this site, in most home set ups, each speaker should be around 2 metres away from the central listening position (at most). In my experience, 1.5 metres is a good distance. The nearer you are to your speakers, the less room acoustics will matter. The front speaker separation should roughly equal how far you are sitting from them.

In my set up, I have the front speakers set slightly further forward (ie closer to the listening position) than the TV. It helps in stereo mode to have as much space around your speakers as possible, esp. in-between the units.

You could even try rotating your set up around; in doing this, the stereo speakers will be even further from the side-walls, improving sound quality. You'll also get an improved surround field with the rear-surrounds further apart.

 

[Krazykaj]

Thanks for the replies

I have actually played around alot with the sub position and the speaker placement.
And at the moment, the room sounds very good. IMHO
Also note that the pictures don't really show the distance of things to scale, i just drew everything up very quickly to show the 'boxes' on my left wall and the ceiling to give reference to show where i was thinking about putting some sort of bass traps/sound absorbtion/treatment.

Basically now, what i am trying to achieve as best i can with what i have, is to follow up on what i have been reading about; that your room is 90% of the sound. ( i realise now, that i am doing things a bit backwards with the room last, and that i'll have to re-calibrate everything afterwards, however it is better than not at all )

EDIT: Not doing the following anymore So i am currently getting ready to nicely cover the bottom (approx.) 1/3 of the side walls and the whole of the front wall and the front ceiling section in thick carpet. (It will also give it more a 'HT' feel/look ) However, i realise that this will only 'deaden' the room a bit in more the mid to high frequency range.
So what i am looking for, are ways to compliment the carpeting with some sort of bass traps, to help flatten the average room response. (mainly when you sit on the side of the room, things arn't so good with the LFE, the middle is pretty good otherwise)

So yeah . . . really i was just trying to explore a few 'stranger' possibilities of ways to execute sound absorbtion.
And i was mainly just curious if it was possible, if it would work, to make the chairs into some sort of bass trap by filling them with something, and if creating some DIY bass-traps/Sound-panels and putting them in the places shown in the pics would be any good?
Would either of these options, on paper, work in some helpful way?

thanks again,

Cheers
KJ

 

[Ethan Winer]

Kaj:

> Is there a way I can maybe fill the inside of the chairs with something (foam, fibreglass) and convert them into some sort of bass trap, or sound absorber? <

As Rob explained, bass traps are most efficient in the corners and, after that, near the walls. You might get some benefit by stuffing your furniture with fiberglass, especially a couch along the rear wall because that's near a wall-floor corner.

TB:

> I really can't see how you can expect to get that much improvement by playing around with things like bass traps. <

Placement can help to flatten the low frequency response somewhat. But placement alone can help only so much, and not nearly as well as bass traps. More important, bass traps also reduce modal ringing which is the primary cause of "one note bass." An untreated room can ring for up to one second at modal frequencies. You don't hear it as reverb because the frequencies are so low. But ringing is very damaging to bass instrument clarity. Another benefit of bass traps is they lower the Q of the room modes. So instead of large narrow boosts you have smaller broad boosts, and that too makes a big improvement in bass clarity.

--Ethan

 

[Krazykaj]

Ok thanks for the info,
I'll drop the idea of filling the chairs, and go for something more significant.

Though i think i will stick to creating the two Bass traps in the positions described above, and i will also place two in both front corners of the room behind the sub and behind the right front speaker.

Thanks for the input

Cheers
KJ

(P.S. Ethan, I hope it was ok, i sent you a PM regarding this site and the materials listed there)

 

[Ethan Winer]

Karl,

> I hope it was ok, i sent you a PM regarding ... <

I answered that PM just now. I always prefer to answer these questions in the public forums. That way, the effort I put into answering can help others, and you can benefit from the answers of others too. So I'll look for a new post from you about that.

Thanks.

--Ethan

 

[Krazykaj]

Karl,

I answered that PM just now. I always prefer to answer these questions in the public forums. That way, the effort I put into answering can help others, and you can benefit from the answers of others too. So I'll look for a new post from you about that.

Thanks.

--Ethan

Ok, no problems . . . sorry


I was going to quickly ask about the products here in this page Isolation Solutions AU
I am going to try a first attempt at creating some similar Bass traps and sound absorption panels as you have described in your article entitled “Build a better bass trap”

But down here in Australia, products aren’t or don’t seem as readily available, or at least they are just called different names.
But anyway, I was wanting to do some quick checks, before I go out and buy anything
First, I was hoping to find out if what I was looking at getting was appropriate, and that I will not be getting ripped off.

Basically the two products I was mainly looking at from the site are the:
Noise Control Batts™
Pinkpoly™ Acoustic Batts and Blanket
(there may be others but these two looked ok; to me anyway )

I still am at the bottom of the steep learning curve in all this, so I am not sure yet, but what exactly am I looking for in the ‘specs’/product details.
Should I get one product over another?
Which figures are relevant to look at, or are they just bogus numbers to sell the product?
Are these completely the wrong type of things to be looking at to create the sound panels/Bass traps you describe?


And to follow from that, if either of those two products would suit my needs, how does I work with getting the correct thickness and mass?

If I look at the ’Pinkpoly Acoustic Batts and Blanket’, especially comparing the PP2 to the PPSR I see the following:
Name – Nominal Thickness – Mass/Unit Area (gsm) – Nominal Density kg/m
PP2 - 50mm - 350 - 7.0
PP3 - 65mm - 500 - 7.7
PP4 - 75mm - 650 - 8.7
PPSR - 50mm - 1600 - 32.0

Now here, they are both the same thickness, however the mass and density in the PPSR is over 4x as much as PP2.
How does it work in choosing the right product? Why would I (not) get one over the other?

The same goes for the “Noise control Batts” (I won’t copy all the info here)
But looking at the 50mm thick and the 100mm thick ‘sound absorption’ specs:
50mm at 125Hz = 0.2 ‘Sound absorption coefficients’
100mm at 125Hz = 0.3 ‘Sound absorption coefficients’

Firstly, what exactly is ‘sound absorption coefficients’?
And would it be better to use two 50mm batts instead of one 100mm batt? It would still be the same thickness, but how do the numbers work when you multiply them by 2?

I wish to create the three types of panels similar to what you described, plus create the separate corner bass traps.
Can I just buy the same product and use it in each panel? (i'm assuming so) Just maybe for the bass traps and low frequency range acoustic panels, I can just do two layers instead of one?
Or should I get a specific material for the Highs as opposed to something else for the Mid-highs as opposed to something else for the Lows?

. . .


So yeah . . . basically I am asking if those products are any good to buy, and if so, which one should I prefer and why. Or do I completely drop them and go look for something else?
And within the products themselves, what exactly am I looking for? How should I read those numbers that they give you in the specs, and how do I go about choosing the correct thicknesses and masses and densities? And should I get different product to treat the different frequency ranges?

Sorry if that was a bit to much


But thankyou heaps again,

Kind regards
KJ

 

[Ethan Winer]

Karl,

> I was going to quickly ask about the products here in this page <

Absorption and isolation are completely different, and often are mutually exclusive.

> the two products I was mainly looking at from the site are <

The preferred material for absorption and bass trapping is rigid fiberglass. Until you get up to very thick materials - like one foot thick - the rigid types absorb much better than fluffy batts.

> what exactly am I looking for in the ‘specs’/product details ... Which figures are relevant to look at? ... what exactly is ‘sound absorption coefficients’? <

There's a good explanation of absorption and how such products are tested and reported in this article on my company's web site:

www.realtraps.com/art_measure.htm

> How does it work in choosing the right product? Why would I (not) get one over the other? <

The only thing that matters is how much is absorbed and at what frequencies.

> The same goes for the “Noise control Batts” <

That's sort of an oxymoron. To me, "batts" are sections of fluffy fiberglass, but "noise control" is handled best with rigid massive walls. However, fluffy fiberglass placed inside the walls is needed to get the most isolation.

> would it be better to use two 50mm batts instead of one 100mm batt? It would still be the same thickness, but how do the numbers work when you multiply them by 2? <

Two thin panels absorb the same as one panel of the same combined thickness.

> I wish to create the three types of panels similar to what you described, plus create the separate corner bass traps. <

For most rooms you'll get great results using only rigid fiberglass. However, larger rooms often benefit from the wood panel traps shown in my plans.

--Ethan

 

[Krazykaj]

Thanks
I'll do a bit more research, and see what else i can find . . .

Kind Regards
KJ

 

[Krazykaj]

Off Wall Bass Traps

Hi, again



Ethan, again, I have another few questions. sorry
I am still trying to determine if I should go for a normal Corner Bass-Trap, or for a ‘Membrane Absorber’/Panel trap.

My question is, regarding both:

You describe constructing these panels/traps as being built directly onto the wall.
The Corner Fiberglass Bass Traps Described in HERE
The Panel Trap design and construction Described HERE
Basically, once constructed, they are pretty much a permanent fixture to the wall.

However, I want to create something that is not fixed. Something I can easily remove/move around if I want to. Something I can temporarily fix to the wall, or add stands too.

So anyway, I have drawn some quick mock-up pictures of how I was thinking to construct either a Panel Trap, or a Corner bass trap (depending on what is chosen).
(I hope you don't mind that i put part of your construction plans in there for comparison purposes, i can remove it if inappropriate.)

Here is the Panel Trap. You can see that one would be built/fixed onto the wall, and one wouldn't.

This is the Corner Trap, again, compare to this pic to see that one would be built onto the wall, whereas the one i propose, would not.
You can also see in the 3D image how i plan to possibly place them in the corners of the room.

As you should be able to see, instead of using the wall as the backing plane for the panel and corner trap, I would use some sort of sheet of wood instead.

Otherwise, everything else would be constructed the same.

Is there anything wrong with doing this?
Do these Bass traps need to be solidly fixed to the wall for a reason?
Here I am specifically asking about the Bass trap/panel, not the mid-High panels as i realise with those, it doesn't matter so much.

Bascially, can i create these things as seperate components from the wall. That way i can move them around.
Or do they need to be fixed to the walls for best performance?
Thankyou Again.

Kind Regards
KJ

(maybe i should post this is a clean thread?? it is a bit off topic from the original question.)

 

[Ethan Winer]

Karl,

> I want to create something that is not fixed. <

Then go with rigid fiberglass instead of wood panel traps.

> instead of using the wall as the backing plane for the panel and corner trap, I would use some sort of sheet of wood instead. <

You can use a thick backing like 3/4 inch plywood bolstered with cross braces for the needed rigidity, but that's even more work and even more reason to go with fiberglass only.

> Do these Bass traps need to be solidly fixed to the wall for a reason? <

They don't have to be fixed to the wall, but they have to flat against the wall.

--Ethan

 

[Krazykaj]

Hello again,

-Then go with rigid fiberglass instead of wood panel traps.-
Sorry, maybe i missed something, but all of what i was describing above would be using rigid fibrerglass. And what about the Corner traps? Or is that what you mean, to go with the Corner Bass Traps and not the Panel Trap?


-You can use a thick backing like 3/4 inch plywood bolstered with cross braces for the needed rigidity, but that's even more work and even more reason to go with fiberglass only.-

Again, sorry, but what do you mean "to go with fiberglass only". You don't mean to just slap a peice of it on the wall with some sticky tape do you?

Really, what i am misunderstanding is;
How are you proposing that I make deep bass traps (using the rigid fiberglass of course ) if not creating them in one of the two ways shown above?? And to have them so they are easily moveable? You have me a little confused here Sorry . . . maybe i'm thick

Thankyou

Kind Regards
KJ

 

[Ethan Winer]

Karl,

> Sorry, maybe i missed something, but all of what i was describing above would be using rigid fibrerglass. <

You linked to my wood panel bass trap plans, so I thought maybe you were considering building those.

> And what about the Corner traps? Or is that what you mean, to go with the Corner Bass Traps and not the Panel Trap? <

Yes, exactly. If you want to build something portable, then get some 2x4 foot pieces of rigid fiberglass and wrap them with fabric.

--Ethan

 

[Krazykaj]

Thankyou

Now i just need to do some measurments, and then hopfully, start building.

Thankyou for you help again.

Cheers
KJ

 

[Krazykaj]

Hi,

Again quickly, to confirm;

This is the stuff the mean, when you mention something like "703 rigid fiberglass", and the stuff you highly recommend i get.
Owens corning - 700 series insulation
Just so i have some exact point of reference when asking around down here.


Thankyou again,

Kind Regards
KJ

 

[tom_b]

That website says 250 Hz to 2 kHz is "speech frequencies" and that range does not apply to music. I would argue that 250 Hz to 1.5 KHz is not speech but rather what frequencies a human can hear. Meaning you cannot hear sounds of a frequency outside that range. So this range is the only range you care about and 100% applies to MUSIC! If you have an instrument that plays below 250 Hz and you cannot hear it, do you care? If you have a sound above 2 KHz and you cannot hear it do you care? Of course not.

Now if the equations and coefficients do not apply that is a whole different story.

 

[Krazykaj]

What I am trying to fix: (this is regarding the ‘Bass’ stuff only)
When I walk around my room, in certain places the bass is fairly ‘boomy’, but in some places it is ok (at the sweet spot it is pretty good, but the edges of the room suffer a bit)
From my testing this ‘boomyness’ seems to occur around the 40Hz to 60Hz range. So when ever something is played, like a Bass guitar, a double bass, certain drums, certain explosions etc. you can notice something not quite right.

I also have the Velodyne DD-18 sub, which has the built-in Equalizer, so I use that to also check out the room. And it shows/confirms, depending on where I place the mike, that I have quite a large hump at around the 46Hz mark. Now I can EQ things a bit, to flatten the response nicely at the sweet spot, but things elsewhere in the room are still a bit rough.
The way I see it, if the room is acoustically ‘dodgy’ in the first place (as it seems my room is) no amount of electronic EQ’ing is going to fix it, especially not the whole room.
So what I hope to do, or try doing, is to change the actual properties of the room itself, to make it more ‘Bass’ friendly. That way, hopefully, I will require less EQ’ing with the Sub and the amp, and that the room on a whole, will sound a lot flatter no matter where you sit.

So i don't know and don't want to argue if i can 'hear' 46Hz or not, but i'm telling you, if you come to my room and sit and listen, things at certain parts boom alot louder in what i'd call 'bass' than in other sections of music.

I have the time, and this project is relatively cheap so I don’t mind having a go (should be a bit of fun also) but even if I do it and find that it makes no audible difference to the room, I don’t mind too much. However, I still want to do a half decent job of it, so that is why I am asking these things here first

Anyways,

Thanks for the comments,

Cheers
KJ
(p.s. on the weekend I collected a bunch of old foam mattresses, and thick blankets, pillows, beanbags etc. and strategically placed them around the room, more to see what happens in the mid-high frequency response in my room. . .
Wow . . . . first off, I didn’t realise how noisy the room was before. Also I was quite surprised at the difference it made when listening to Stereo audio. The centre sound stage was so much clearer and crisp is was amazing. And some of the harsher treble notes (from the likes of cymbals, violins etc) that I thought were originally part of the recordings, were gone, things were now smoother and clearer. It was even more of a pleasure to listen to music now.
I thought my room used to sound good before, but now I can’t wait to create these mid/high acoustic panels. Even if the bass traps don’t work, these other panels will be a huge improvement in themselves; it will also look good as well )