I went through a similar excercise last year. I assume you are measuring at ear-level listening position? Did you also use REW’s function to plot room modes? My spectragraph looks lot like yours, but room has a massive 50Hz spike simply due to the size of the room and my listening position. Perhaps your 40Hz boost is because of the same? I managed to bring it down just a little by tweaking the sub’s phase a little and absorbtion via what is arguably the ugliest DIY bass trap in all of Amsterdam, but since it’s a room mode I can’t get rid of it entirely - except by moving my seat.
I think your right about the40hz going to have one last go by moving the shelving unit. Then bass traps here we come! I am encouraged by the influence of adding the single panel.
Less sure what to do about the attenuation in the middle of the plot.
Its a fun journey though!
Have you noticed that in the spectrogram with the duvet ove the TH, the 40Hz dies away a LOT more quickly.
This gives me an idea…
Try folding up the duvet and using it to fill the space behind the TV. Listen to the effect that has and also do a waterfall plot comparing with and without. There is a small chance that this could be a significant contribution to the bass traps required.
If this makes a significant difference, then the space behind the TV can be filled with foam (of course use fire retardant foam!) giving a useful bass trap that is very cheap and also doesn’t impinge on the aesthetics of the room.
Of course if you turn on the TV make VERY sure the cooling slots aren’t obscured!
Ive added the plot from just moving the speakers forward (No Duvet) similar as with, Will try the duvet behind the TV later
Your on to something!
Moving the speakers forward makes the biggest improvement to the waterfall chart.
and improvement in the SPL Orange
I then placed as many cushions and duvets I could find behind the TV and cabinet Blue
Then removed from behind the TV but left behind the LH speaker RED Very similar result so I think this could be a quick win add an absorber behind the LH speaker on the wall
It’s made a big difference to the impulse trace.
Does the music sound better as well?
I honestly think music does sound better. Thank you so much for your advice and guidance.
Dropped a note to the guys at GIK to see what they think about the attenuation between 400-1000hz as ive convinced myself that the top end feels too forward because of it! Could look to attenuate the top end but ive never heard of anybody doing that!
Leaving the corner bass traps until last as these will be the hardest to gain approval for!
With a complex room setup like that, it’s often very difficult to isolate specific problems in the FR traces to individual causes, other than by a process of elimination. This is particularly true in the lower midrange where you tend to get a lot of panel and cavity resonances e.g. from tables, bookshelves, cabinets, doors, and lighter structures (such as boxes round doors!), etc!).
You could try tapping things to see if they resonate in that frequency range, but you’re likely to find a lot of things do; which ones cause or contribute to the issue is another matter though.
My simple if somewhat clumsy plan is to buy some 600x600 traps from GIK, they come in a box of 4. Move them around the room and measure the effect. Starting with the wall behind the speakers and the 1st reflection points.
Nothing at all wrong with moving them about on a trial and error basis. But don’t just measure them , listen to them in all their various positions. Also , I know they are more expensive, but I would go for the Monster bass traps over the 244.
Monster bass traps are a given once i get wife approval! Smaller ones (242 or alpha pro) hopefully resolve some of the reflection issues
The reason I suggest Monsters is that the full range version is ideal for first reflection points but you get the added bonus of bass treatment as well. Obviously that assumes you get approval .
Great discussion and analysis btw. Very instructive, thx!
When I had my main system combined with telly I had a panel behind it and SWMBO was happy with that. I also put some acoustic absorber behind a picture on the wall which helped a little behind the listening position.
My main system is now in smaller room with 6 GIK panels and counting. Strangely I get more bass with the panels than without!
Putting aside the lovely graphs and waterfalls, I’d suggest the following basics:
Have the TV in the centre of the cabinet and as close to the windows and curtains as possible.
Move both speakers forward about 1 m from the window / wall - at least so the drivers are in front of the TV cabinet.
Move the right speaker further away from the side wall.
For critical listening, move the sofa forward slightly from the rear wall, and about the same length from the listening position to each speaker, as the distance between the speakers.
Try the sub next to one of the speakers (and between the speakers), drop the cross quite low and then set the gain so that you can’t hear it without putting your ear close to it when playing music.
Good luck.
Is that more or a more even bass response?
"Good’ is something subjective.
Treatment has two parts. One is objective and the other subjective.
The objective one is reflected in the measurements:
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Frequency response as flat as possible across the spectrum.
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Decay time as even as possible across the spectrum.
The subjective part is a matter of taste.
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RT60 more or less short
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Acoustic comfort of the room: energy is preserved (diffusion) or the energy is dissipated to the maximum (absorption).
My listening room is not finished.
I don’t know what its frequency response will be. I have an idea, based on models, but it’s just an idea. There is no substitute for measurements.
When the room is finished I will post a plot.
This kind of info is easily found on the web. It will allow you to see what the plot of a well treated room looks like.
Here is one :
Here’s another one. Before and after treatment. It should be noted that before the treatment the frequency response was already good.
Thanks Thomas
Just to clarify my ‘Good’ = The measurement is the quantification of the subjective. In the same way as we can measure and quantify all of the attributes that make a car ‘feel’ like it handles really well. Or a gear change that feels really satisfying thanks the the careful balancing of quantifiable attributed like clutch and gear lever effort profiles, ergonomics ect.
Of course the tough part is the interpretation and implementation of solutions rather than taking the measurements themselves