Is it possible to get room-modes for an L-shaped room?

[GIK Acoustics]

Room modes can be tested in the room, which is the correct way to go about it. Calculators are only estimates in the first place. See if your peaks or dips are correlated to your room dimensions (or very close to).

You can drive room modes harder purposely by sitting a speaker in a tri-corner of your room, and by placing the mic in an opposite tri-corner. Perhaps you could place your speaker on the floor in a corner, the mic next to the ceiling in a corner (via duct tape or whatever you have to use) and do a test. The really strong peaks will be your room modes (you can verify by looking at the waterfall as well).

[JLiRD808]

Yeah Ive tried using the room calculator based on the skinny and fat parts of the L, neither seems to match to the results I get.

Not sure which corners ur suggesting I run my own test from, but Im thinking the most lower left corner and upper right most corner (based on the floorplan in the linked thread).

Just run an SPL freq measurement test?

THANKS!!

[GIK Acoustics]

Originally Posted by JLiRD808

Yeah Ive tried using the room calculator based on the skinny and fat parts of the L, neither seems to match to the results I get.

Not sure which corners ur suggesting I run my own test from, but Im thinking the most lower left corner and upper right most corner (based on the floorplan in the linked thread).

Just run an SPL freq measurement test?

THANKS!!

Yes, but viewing the waterfall will clearly show the modes with a bit less ambiguity. I would actually place the speaker on the lower right hand cornered pictured in your other thread, and place the mic above the corner where your right speaker is. This would at least give a better idea of the 'relevant' modes (or at least the ones that hold power closer to the listeing position) if that makes sense.

Also, you can check out our video on REW on how to view your results and what to look for. Waterfall graphs are very important for seeing the real problems your room is having. For example, your 150 Hz peak might not actually be too large of a problem compared to a possible large resonance somewhere else lower down the spectrum. Room EQ Wizard Tutorial Video

[Jens Eklund]

Room Correction Mic

[JLiRD808]

I'll run the waterfalls tonite! Thanks...

Thanks too Jens...u always post stuff thats WAY over my head lol...but I'll catch up one day I hope!

[JLiRD808]

Ok wow check this out...I havent had a chance to run waterfalls yet....there's some kids playing music outside my window.

But what I did do was something I nvr tried before. I looped REW's "log sweep" in the generator between 30hz-450hz and held an SPL meter at my listening position. I watched it peak and dip in accordance with my measurements found here.

But then what I did was place the SPL meter at different spots/corners and ran the same log sweep (Glenn, I know this is similar to ur flicker wave test, and really spawned this idea). I found a HUGE peak around 60-75hz down around the floor/wall corners, particularly on the left side of my desk. Then I used REW's generator to just run a sine wave, starting at 60hz, and then I slowly incrementally raised the freq while watching the meter. I was able to determine that 62hz rang the loudest.

With the sine wave still emitting at 66hz, I returned to my listening position and instantly noticed how quiet it had gotten. I stuck my head down by those floor/wall corners again and WOW....pretty loud! The difference was so much, I had to adjust the rotary knob on my SPL meter to get an accurate reading or else the dial would fly off the scale.

So what does this mean now? If I can contain/trap that 66hz area down by the floor, will it bring it back up at my listening position? Are the freqs stacking there, and trapping them would give me a more even response?

THANKS!! Gonna keep working some more...

[Jens Eklund]

How to treat nulls

[JLiRD808]

Did a bunch of waterfalls last nite...these 3 were pretty good averages..ranging from the worst to the best.

Is it normal to have variations like this btw? I never really get the same graph twice.

Seems like I definitely have a problem from 30-40 & around 60hz (matches the freq I found booming down by my feet).

[AwwDeOhh]

If you have a few extra traps laying around, try placing a couple approx 4' 8" from a trouble boundry (1/4 wavelength of 60 Hz). This should make an extremely effective absorber at that frequency.
You should be able to move them (traps) to different walls (at the 4'8" distance) to find the most effective wall to treat. Of course testing all the while to confirm.

Though... having a trap that you trip over isn't ideal... but once you find the spot that works best, maybe making a free-standing "soffit" type trap that doubles as a coffee table type thing might not be as bad?

[JLiRD808]

^ Not totally read up or knowledged about boundaries exactly...and particularly what would be my "trouble boundaries". Is that the flanking walls?

In the pic below, the area where the electric bass and amp is and behind the desk down low is where I pick up the MOST 60hz with the SPL meter. By my feet too actually, underneath the desk.

Also, what size trap u think? I have plenty access to 705 as I think I mentioned somewhere.

[AwwDeOhh]

In the diagram you show, it looks like there is already a table in front of the couch and loveseat. How far from the 'back' wall is that? Try, just for test purposes, taking an existing trap (say, from by the doorway) and standing it on the table. (again, 4ft 8in from the wall)