What’s a bass trap do I need one ?

[ultumax]

I was curious about these were do you find cheap affordable high quality ones and , how much better are expensive ones?
Cheap? Starter kits or packages
Premium ?
High end traps ?

Can any household materials or packaging products work for a diy trap ?

Does it make home theater better in rooms with poor acoustics?

 

[JoeESP9]

They generally smooth the bass. It's not an HT or audio thing. Using room acoustic treatments always results in better sound. Bass traps help smooth out the in room bass response. I have a couple of them in addition to half a dozen 2' x 4' x 2" DIY acoustic panels. Acoustic panels help to reduce first reflections, slap echo and reverb time.

The cheapest bass traps are regular pillows placed in the corners (stack them 2 or 3 high). They may not be as effective as true bass traps but they will have a positive effect on the sound.

There are numerous websites that give step by step instructions for making you own room acoustic treatments. It's actually quite easy.

I made my panels and bass traps 30 years ago. Some Owens Corning Fiber Glass panels, cheap wooden frames and speaker grill cloth. 3 years ago I recovered all of them as after 30 years there was some "discoloration".

 

[cunningr]

I found this guy on youtube that specializes in home recording studios and doing room treatments. Wish i could remember the dudes name, whole series. Talks about bass traps and finding first reflection point using a mirror.

I was think of trying to use some canvass wall art with sound absording panels but not sure would be affective.

 

[Brett a]

You can improvise bass traps. Just bear in mind they are called bass traps for a reason. Bass energy passes through them and gets trapped behind. Which means the trap needs to have an open back with space between it and the wall (or corner). I have a pair that I purchased from ATS Acoustics several years ago. They are an excellent source for ready-made panels. Their prices are very reasonable. The ones I bought could be easily made. They are 4" of Owens Corning 703 surrounded by an open-backed wooden frame and covered with a burlap material. I have them mounted in the corners behind my speakers.

Steve Albini talks about trapping bass on the cheap in his first studio at the 16:55 mark of this video (and at 26:20).

 

[ultumax]

You can improvise bass traps. Just bear in mind they are called bass traps for a reason. Bass energy passes through them and gets trapped behind. Which means the trap needs to have an open back with space between it and the wall (or corner). I have a pair that I purchased from ATS Acoustics several years ago. They are an excellent source for ready-made panels. Their prices are very reasonable. The ones I bought could be easily made. They are 4" of Owens Corning 703 surrounded by an open-backed wooden frame and covered with a burlap material. I have them mounted in the corners behind my speakers.

Steve Albini talks about trapping bass on the cheap in his first studio at the 16:55 mark of this video (and at 26:20).

So it trapps the non needed bass waves for better sound ?

 

[SaSi]

What a bass trap is doing is attenuating reflection of low frequency standing waves, and in effect taming the resonances (i.e. room modes). In a small room, these will start at around 30-40Hz for the longest dimension, with two more modes for width and height and all their harmonics. It's not a simple as that as there are also oblique dimensions giving some lower resonances at a lower amplitude as well.

Bass traps are made of material that allows sound waves to go through but attenuating them by converting air movement to heat, by friction with the material. Mineral wool is a good material to use, at medium-high densities, like 60kg/m3 or higher. That is always wrapped in sound breathing fabric that keeps the fibers inside.

It is not the best location to place them flush with the walls. These are the points of higher pressure and almost zero air speed. As you move into the space of the room, pressure gets lower and air speed increases. The rule of thumb best recipe is for a 4" thick pad (2'x4') at a distance of 4-8" from the wall.

A good placement for the panels is to angle them against a corner, especially behind the speakers. If you can stack two of them high, all the better. Cylindrical or square cross-section traps are also made and are easy to stack in corners. They do work, but the material touching the corners is actually wasted. In terms of material used+space lost vs effect, they are not that much effective compared to panels spaced from the walls.

For low frequencies, the issues related for first reflection points are not relevant as the sound travels at 4π direction and not in "rays", like the output from the tweeter.

I prefer treatment behind and around the loudspeakers,so that they don't become very effective in the high frequencies (which are much easier to attenuate than low frequencies). You can't place too many treatment for low frequencies in a small room but you can do that for mid-high frequencies, turning the room towards being dead acoustically.

 

[JoeESP9]

It would seem we differ. IME acoustic panels are not a replacement for bass traps. Using both in my listening is where my opinion comes from.

 

[SaSi]

If by acoustic panels you refer to relatively thin, foam panels, then yes, you are correct, they simply don't function in low frequencies. In fact, using too much of these in a room can reduce high frequency reflections to the point the room will sound dead and boomy.

In my description above, I am describing the effect of rather thick (4" minimum) panels made of 100kg/m3 mineral wool.

 

[E-Stat]

I use a small forest of tube bass traps using this DIY recipe. They helped to provide measurably neutral bass in the bottom octaves. After experimentation, I placed most behind the stats with a couple narrower ones at the other end of the room.

 

[twiiii]

All rooms have acoustic issues. Room gain, standing waves, and other issues. Bass traps help break up and absorb extra bass energy in a room that maybe undesirable. The problem is unless you have trained ears or sophisticated test equipment bass traps can cause even more issues than you started with. There is the direct sound of the speaker and there is reflected sound of the room. The idea of a bass trap is to prevent the reflected sound from smearing and covering the direct sound to a point. Then below certain point you need the reflected sound to extend the bass in the room. And you don't want the traps to rise to high or they will over effect the upper bass and lower midrange. Un fortunately it takes a lot experience with a FFT or TEF analyzer to get it right. Using just your ears is hap hazard at best. I deal frequency response is only one parameter on the quest for the best sound. Arrival times is another. Bass traps can only remove certain energies, they can't change arrival times.

 

[E-Stat]

Un fortunately it takes a lot experience with a FFT or TEF analyzer to get it right.

No it doesn't. How many traps do you use in your room?

Placement of mine was determined by extensive experimentation of placement measuring the results along the way. While this is but a third octave plot - and a RT plot would most certainly be more variable, I get audibly and measurably neutral response with a gradual rise in the first octave.