[Bloodstain]

Hello,

I've been thinking of improving my listening room acoustics with two bass traps. I made some plans and measurements and I think I need some help and opinions.

First, here are some information about my listening room:

ModeCalc and dimensions
Layout

The X marks the listening point and the two blue X's in the corners would be the placing points for the bass traps. I have very little (or almost nothing) possibilities to change speaker/listening points. At the moment the sound is acceptable, but the sound is actually quite thin. Not boomy. With the bass traps I'm hoping of reducing the bad nulls and peaks and get a smoother response.

I have 10 ecophon acoustic panels (120x60x3cm) and I made measurements with all of these 10 panels placed in a one corner at the time. The final bass traps would be bigger and placed in both corners, but this gave some information what would be expected. I've used few of these same panels at the back wall to reduce echo.

The measurements are made at the listening point with room eq wizard.
Red=without the "bass trap" and green=the panels in the right corner (this had a bit more effect than in the left corner, although the effect was very similar)
Frequency responses
Waterfall
Waterfall with the panels in the corner

And there really is some differences. Placed in the left corner, the 65Hz peak wasn't attenuated, but above that the effect was very much like. I would very much like to see the 80-120Hz nulls reduced with the bass traps in place and also the 65Hz peak doesn't look that nice.

A word about my speakers: 2-way MTM floorstanding speakers with 6,5bass drivers in a reflex box tuned around 33Hz. I've made these speakers myself and they perform very nicely.

Here is a scetch of the bass traps I've been planning in the corners:
BassTrap
Filled fully with RockWool and stuffed quite tightly to increase the density of the wool (which is optimal for thermal insulation if not stuffed).

Now, if you look at the ModeCalc, room layout and measurements, could you tell me which room modes are most likely to cause the nulls at 80-120Hz and peak at 65Hz? I'm not that experienced of researching room acoustics myself so I'm not sure at all and I would like to think of possible ways of mayb improving the bass traps I've had in mind.

The 80-120Hz region attenuation seems to be consisted of two different nulls.

I'm also a bit concerned not to dampen the 200-500Hz region two much. Do you think this plan of two big bass tarps would be worth of making?

Edit:
I just made measurements also from all of the front corners as I thought it could be valuable information.
Corners

[Ethan Winer]

The X marks the listening point ... the sound is actually quite thin.

The sound is thin because you're exactly centered front to back. That location always has a huge bass null. If you move your seat forward even a foot or two, that alone will help a lot.

The final bass traps would be bigger and placed in both corners

Ideally, you'll have more than just two bass traps. But two is a good start, and infinitely better than none.

Here is a scetch of the bass traps I've been planning in the corners:

Yes, that's the right idea.

if you look at the ModeCalc, room layout and measurements, could you tell me which room modes are most likely to cause the nulls at 80-120Hz and peak at 65Hz?

Peaks and nulls are just as likely caused by placement issues as by room modes. ModeCalc is meant to assist designing a new room, not so much to help you figure how to treat an existing room. The good news is you don't really need to calculate anything. The solution is as many bass traps as you can manage. Remember that rectangle rooms have 12 corners, not just four where the walls meet.

--Ethan

[Bloodstain]

The sound is thin because you're exactly centered front to back. That location always has a huge bass null. If you move your seat forward even a foot or two, that alone will help a lot.

Unfortunately I live in a studio flat, so there isn't too much space and with my sofa and my bed in the same room there aren't any other practical solutions

But do you think the nulls could even up some with the two big bass traps?

[Ethan Winer]

do you think the nulls could even up some with the two big bass traps?

Yes! Having two bass traps is infinitely better than having none.

--Ethan

[Bloodstain]

Well, I made the bass traps and now I have made some measurements. I haven't finished the traps yet as I thought I first decide if they are any good and worth finishing.

I only have two of the four traps I made (each 120cm tall, and on top of each other 240cm) in my apartment for the measurements and a pack of acoustic panels I used in my initial measurements. But the results should present pretty close to the final situation. I tried all different possibilities placing the traps and panels (front right/left corners) and the "damped" measurement I now present is with the both traps on the right and the panels on the left, as this had most effect.

Red is without damping, blue with damping. No SPL calibration.

Responses
Waterfall
Waterfall damped
Waterfall Both
RT60

Responses: Nice to see the 65Hz bump slightly damped and the 100Hz null is smoother. but I was a bit surprised to see what happened around 150Hz.

Waterfall: What is stange here is that the undamped measurement is quite a bit different to the earlier measurement I made (first post). In the first measurement there was quite a lot echo in the 100-120Hz range, but this new measurement doesn't show this. The only differences I can think of in the measurements is that this time the volume level was probaply a bit lower, and the bass traps was located in the next room which has an open door. But I tought neither of these would have any affect.
In the new measurements I can see very little differences in the waterfall measurements.

RT60: This looks good, but I'm not sure if this should be measured again with bigger volume levels. And I don't understand that if this shows this much difference, why there is so little difference in the waterfall graphs?

And listening impressions? Well it's a bit hard to say. Maybe the bass some more punch now.

-Ari

Edit: I just made the same measurements with higher volume and I moved the bass traps further away from the listening room when measuring undamped. Results: Frequency responses and waterfall, exactly the same. RT 60, way different, and not for the good. This doesn't seem to be reliable measurement in this case. When I changed the "dacay measure" to 20, the measurements was more similar, but I would say that the difference between undamped and damped is quite small.

[Nyal Mellor]

Like Ethan said, getting rid of that big peak at 60hz is going to be difficult without moving your seat away from the middle of the room. The only other alternative would be EQ which can work quite well for only one listening position.

I'm not sure how far your speakers are from the back wall but that 100hz dip looks like speaker boundary interference. Try moving your bass traps around to find the position that has the least null. Moving your speakers so they are not the same distance from side and back wall will also help.