Dual subs vs bass traps

[outrun]

Hello all,

I am slowly setting up and upgrading my first music room. Currently exploring options regarding to the low end. Now I understand the importance of bass traps, but I wonder if building those huge boxes could be avoided or at least reduced with dual subwoofers. As I understand setting up two subs instead of one, would smooth out the bass response in the room.

Another somewhat related newbie question, is it possible to cut off the low frequencies going to my main speakers somehow, I don't think they will add anything of value after installing a sub. My amps are just analogue stereo and don't have any filters, are there DSPs or something like that could sit in between of the signal?

 

[DVDdoug]

I'm not an acoustics expert...

I wonder if building those huge boxes could be avoided or at least reduced with dual subwoofers.

There are membrane style bass traps that don't take-up a lot of space.

If you are going to all this trouble, get a measurement mic... and measure your room/speakers (diagnosis before treatment)

Another somewhat related newbie question, is it possible to cut off the low frequencies going to my main speakers somehow, I don't think they will add anything of value after adding a sub.

AVRs have have an optional built-in active crossover called "bass management". That's the easiest way to do it.

BTW = The "point one" LFE channel in movies ONLY goes to the subwoofer already. You loose it with a regular stereo setup... You need an AVR or some other surround processor/decoder.

Some active subwoofers have a built-in crossover. You feed-in the line level signals and there is a high-passed line-level output that goes to your regular amplifier.

You can also buy an active crossover or program a miniDSP as a crossover.

My amps are just analogue stereo and don't have any filters, are there DSPs or something that could sit in between of the signal?

Equalization can knock-down bumps (standing wave anti-nodes) but it doesn't help much with dips (standing wave nodes) where the waves cancel. You need nearly infinite power and infinitely-large woofers to overcome cancelation. Also, EQ only fixes one place in the room (one place in the standing wave).

 

[moonlight rainbow dream]

Ideally, you would have both, because they are effective in different frequency ranges. Multi-sub is really effective down low below the crossover frequency where bass traps become too large to be practical. Absorbers around 4" thick will help deal with issues around and above the crossover.

 

[MRC01]

Tube traps are another room treatment option. They can be compact size at very low frequencies relative to other treatments. The ones I built are about 2' diameter and effective down to 30 Hz, placed in the corners of the room running floor to ceiling.

 

[Bjorn]

They don't really compare. Two subwoofers will seldom give a much more even response vs one that's optimally placed. But two will give more output and lower distortion.

Bass traps, depending on frequency, normally needs to cover a good size of the surface to be effective. The lower the frequency, the more surface area needs to be covered for good effect. However, above about 100 Hz a few bass traps can make a solid improvement and that's an area where two subs don't necessarily improve much in the response. Plus two subs will not improve the important time domain behavior in this frequency area.

Treatment works in the time domain behavior and in the amplitude. Multiple subwoofers, normally minimum three are needed, primarily works in the amplitude but can also improve the time domain behaviour some below 80 Hz or so

Different approaches that don't really compete. The most audible bass is above 80 Hz and up to about 200 Hz where treatment is the only option that works really well

 

[Flaesh]

two subs instead of one, would

A subwoofer can be a good absorber. See SSS in Fazenda's Perception_Modal_Control https://audiosciencereview.com/foru...gh-fidelity-home-reproduction.1259/post-32185
Not as good or efficient as a double array, but easier and simpler.

 

[Elkerton]

They don't really compare. Two subwoofers will seldom give a much more even response vs one that's optimally placed.

I beg to differ. Welti and Devalier found that 2 subs at mid points on opposite walls do wonderfully well at controlling a room's standing waves, and that, in a worst case scenario, a square room. I have been using the method for years to great aural advantage. See section 4 paragraph 3 if you care to avoid all of the data:

https://audioroundtable.com/misc/Welti_Multisub.pdf

 

[Wesseling Audio Lab]

Having designed and built 2 rooms with extensive broadband absorption and corner traps. I can more than safely say that the improvement in bass response is dramatic - measured and subjective. The rooms are full surface(ceiling and walls) coverage. one room had 2 walls with drywall attached to resilient channel and dense insulation behind the wall.

The measured improvement is average 6db leveling of dips and peaks below 300hz. CSD shown much less stored energy after treatment.
subjectively, bass response is tight and unmasked across the band. Also back wall and corners become more than acceptable areas to listen to movies/music without(or very little) annoying phase distortion..

Although, it starts with low resonant speaker systems as this will activate room modes with more energy!

 

[Willem]

Although, it starts with low resonant speaker systems as this will activate room modes with more energy!

Room modes are a room property, and not a speaker property.

 

[Willem]

By and large there are three ways to defeat room modes: bass traps, multiple subs and dsp room equalization. For most people bass traps in the right (large) size are just too ugly in a domestic context. The combination of at least two subs (but more is always better) and dsp room eq works very well. Multiple subs do not have to be identical and do not have to be that large (although it helps if one of them is larger). The advantage of using multiple subs in combination with room eq is that the combination allows the equalization to be optimal over a larger area of listening positions. Best software for this is Multi Sub Optimizer, but it takes some time to master it.

 

[holdingpants01]

There are also active bass traps like PSI Audio AVAA, very effective below 50Hz where traditional passive stuff becomes unpractical, I have two for sale but I keep one stuffed above the door, no way to replace it with passive absorption, not enough space

 

[Bjorn]

I beg to differ. Welti and Devalier found that 2 subs at mid points on opposite walls do wonderfully well at controlling a room's standing waves, and that, in a worst case scenario, a square room. I have been using the method for years to great aural advantage. See section 4 paragraph 3 if you care to avoid all of the data:

https://audioroundtable.com/misc/Welti_Multisub.pdf

The question is how much time was spent on optimization of both the listening position and the first subwoofer. When that is done, usually as second subwoofer doesn't achieve a flatter response.
In the rooms I've tested, two subs at mid points in the rooms have never worked well BTW.

 

[Willem]

One sub can easily be equalized, but only for one listening position. The benefit of multiple subs is that this listening position can be much expanded. I use three subs (one largish, one medium size and one small), and not only is the bass response very clean and tight, but using Multi Sub Optimizer it is so in almost the entire listening room. Thus far, it is optimized at seated height, so when I stand up response is less good. My plan is to get a fourth sub and have it at 2 meters or so.

 

[Wesseling Audio Lab]

The rooms that I've mentioned have been rebuilt. Drywall removed and start from scratch etc, so there is no bass treatment inside the room but rather built into walls and ceiling, except for addition of corner traps which are seen. Extensive bass treatment like this needs to be experienced before conclusions can be determined, objectively and subjectively. I haven't seen to many people who have done it. when I see photos of rooms stated to have "many bass traps", its simply not a lot of treatment for sub 300hz. The walls and ceiling in my new room have been removed and will be reworked soon. Its also my aesthetic preference over adding additional sub boxes.
This type of room along with low resonant speakers( bass ringing and sustain can put more energy into the room and increase the room problem) proves to be very effective and relaxing for my auditory system..