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DIRAC AND ROOM TREATMENT
- Thread starter Georgeadv
- Start date
Is the front of your speakers (drivers) 1.2m from the front wall (wall behind the speakers)? That would explain the 70Hz null.
Regarding your previous question about reflections, the best way to see the first reflections is to go to Impulse response in REW. Let's take for example the window reflection coming from your Left speaker. You can calculate the distance in meters from speaker to window, window to listening position. Say for example it's 3.4m, divide it by the speed of sound 343. Then measure your listening distance (for example 2.4m), divide that by 343. Subtract the results. In this case, you should see a big peak in the impulse response at 0.003s = 3ms. Same thing with the reflections from the wall behind your head. If the wall is 50cm away you should see the reflections in the Impulse response at ~1.5ms (Edit: of course 2x1.5ms since the sound travels first 50cm farther and then 50cm reflected). And so on. Then add an absorption panel, remeasure and you can verify if the reflection is attenuated
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See these helpful guides from Genelec & Neumann. So the front wall seems to cause the ~90Hz dip.
It's certainly possible the 70Hz null can also be caused by a room mode in your listening position. You can add your room dimensions to REWs Room Sim to get clues what's behind the null.
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Another, perhaps simpler way to approach the Impulse response is that the direct sound from the speaker hits the listening position/mic at 0ms and for every 1ms delay in time the sound has travelled 34cm longer. You'll get the hang of it! But again, this would be what I'd look at primarily if/when you get the absorption panels up on the back wall.
it's very strange for them to say long distances are 'unacceptable' when they don't advertise their speakers to extend that low to begin with.
i would take that 2 meters distance and cross to a subwoofer instead.
True, if you look at the Neumann guide with 'Bass managed loudspeakers' the only bad distances are 1m and 80cm since the SBIR null is close to the typical sub crossover area.
- Thread Starter
- #87
Thanks I will study it.
I will go with Vicoustic since I have a local retailer who can source me.
With respect to the 40 hz spike, I can't see anything that might work that low from their range....
So from what I understand absorption should be kept at minimum as it would intervene - mess up other frequencies which seem okay? is this correct?
Well, as you see on the RT60 graph your decay times at higher freqs are actually already quite good. You want to avoid thin absorption panels that absorb only treble and upper mids. Definitely add absorption on the back wall directly behind your listening position. If you want to add more elsewhere then something similar to GIKs diffusion/scattering plates (on top of broadband absorption panels) would be a good idea to keep some of the high freq energy 'alive' in the room. But again, since the back wall is so close to listening position, put 'pure' absorption (no diffusion/scattering) there.
Have you tried EQ'ing the 40-50Hz peak, how about your plan to use Dirac?
- Thread Starter
- #89
Hmm okay I will send my graphs to Vicoustic to make an offer.
Shouldn't the RT60 values be lower?
I tried with Dirac and the boomy bass is largely gone however it sounds thinner compared to before. Also I read that is not good to eq more than +/- 2-3db.
Also I need to find a way to only eq up to 300mh and not all the way or learn how to eq with REW and import those in Audirvana.
Shouldn't the RT60 values be lower?
I tried with Dirac and the boomy bass is largely gone however it sounds thinner compared to before. Also I read that is not good to eq more than +/- 2-3db.
Also I need to find a way to only eq up to 300mh and not all the way or learn how to eq with REW and import those in Audirvana.
Depends if you prefer a studio/headphones-like sound or more airy, spacious sound. Something like 0.4s I mentioned before could be a good compromise between the two and at high freqs you are close to that. Probably due to your curtains, rug and sofa.
You can modify the Dirac target curve to your liking, try the Harman house curve for example.
It's okay to attenuate more than that but yeah I wouldn't add more than +3dB, actually I don't try to correct dips/nulls at all with EQ.
Just follow the steps in the video in post #10 and you should be able to create EQ filters with REW in no time!
- Thread Starter
- #91
thank you again!! really helpful stuff! I will try tonight
Just a question harman Target level is set at 75.0 dB and so I did set my measure level (approx) when testing sound level with REW however in REW my graphs at the bottom state different Db.
If you dont mind and time allows can you tell me if I have done something wrong?
- Thread Starter
- #92
Moved the speakers closer to the front wall and indeed the dip almost was eliminated however it increased that spike at 50hz
I did some reading and found out that the peak 50hz cannot be treated by reasonable room treatment..
The bass traps have to be huge and from what i can see vicoustic does have something to target 50hz effectively.
Therefore, it wouldnt be efficient to try to fix that problem with bass traps or room acoustics...
So what are my options then? Eq that spike 3-4db i think would not be enough..
your options are getting two subwoofers (or four preferably), they would complement each other so the dips and peaks would not be so huge.
- Thread Starter
- #94
Would 1 make any difference or it has to be more than 1?
one would definitely make a difference as the distortion would go down and you can place it independently from the speakers.
However to get that region really smooth without Home cinema level bass traps you need two or more.
First I would put some bass traps on the wall behind the listening position to smooth the 100Hz to 300Hz region. then I would get a subwoofer.
@Georgeadv
How does the Frequency response look after you pulled the speakers away from the front wall?
How does the Frequency response look after you pulled the speakers away from the front wall?
- Thread Starter
- #97
I am waiting for a proposal tomorrow from vicoustic
I will let you know what they suggest.. i assume a lot..
I can put some on the back wall and was looking for the small kef sub however is rather expensive..
Here are the graphs..
Green line taken with the speakers pulled back
Green looks good above 100Hz! how far is the listening position from side and back walls again?
- Thread Starter
- #99
Thats good to hear!!
From the back wall it is approximately 60cm now and 1.40m from the side walls
I don't see a dip at ~140 Hz but I do see a peak at 280. but we need more conclusive evidence (perhaps a DIRAC average of a several mesurments?)
If no dips are caused by the back wall i would not get bass traps just yet, as peaks can be neutralized with EQ decently.
you should have a peak 120 Hz and a dip at 61Hz, perhaps the peaking from the side wall is fixing the dipping from the back wall? that's a nice coincidence.
The 61 Hz dip is very visible
I'm using this calculator http://www.mcsquared.com/wavelength.htm
1/4 wavelength = dip
1/2 wavelenth = peak
