Bass in small bedroom (effects of PSI AVAA, subwoofer and EQ, also passive absorbtion)

[DJBonoBobo]

May I ask again to make sure I got it right:
Do I understand correctly that on this basis one would assume that in my case (in my room, as I have shown it here), the AVAA has only a relevant (audible) effect on the extinction at about 27 Hz, but that everything else should not be audible?
And that this would also still be true if the difference in decay with/without AVAA below 100 Hz were greater?

So, to put it bluntly, I would have spent 4,700 Euros to have bass between 20 and 30 Hz?

The question is not meant sarcastically, and of course only related to the situation described.

 

[DJBonoBobo]

So, identifying if the room modes that are audible from your listening position are transversal modes, longitudinal modes or vertical modes, might help.

I tried, but could not get it right. I ended up just trying every reasonable and practical location as good as i could. In my experience placing the AVAA close to the speakers had a negative effect on the frequency response in my case.

I see on your frequency response a lack of energy from 70 to 110 Hz. This is often caused by the wall that is closest to the speakers, just behind them.
Maybe an AVAA could fill this dip. But in this case, the acoustic resonance is limited to the space between the speakers and wall (although the result is audible through the whole room). Since we are relatively high in frequency, and it is usually a quarter-wave cancellation, positioning the AVAA might be tricky. I think it may work with two AVAA, each one right behind each speaker, with their sensors and drivers turned against the wall in order to intercept the sound wave at the farthest point from the speakers, leaving the most possible amount of direct sound.

I didn´t try this position yet. Maybe i´ll do it some time. It is not very practical and i don´t know where to place the subwoofer then. I posted pictures of my room above - this would mean squeezing the AVAAs in front of the radiator and maybe placing the sub in the corner. I am not very optimistic this would help, but I don´t know.

By the way with the new EQ-settings (suggested by @QMuse) the dip around 80 Hz is almost gone. There is still one around 100 Hz. It got smaller by tuning the delay, as @hyperplanar suggested, so time aligning may be a good strategy for this particular dip. I did not manage to do it perfectly yet, but it is getting closer.

That´s how the last try looked like (dip around 300 hz has something to do with my desk/screen-situation and changes if i move the screen, so it can be ignored here):

RTA MMM of all speakers:

 

[QMuse]

I tried, but could not get it right. I ended up just trying every reasonable and practical location as good as i could. In my experience placing the AVAA close to the speakers had a negative effect on the frequency response in my case.



I didn´t try this position yet. Maybe i´ll do it some time. It is not very practical and i don´t know where to place the subwoofer then. I posted pictures of my room above - this would mean squeezing the AVAAs in front of the radiator and maybe placing the sub in the corner. I am not very optimistic this would help, but I don´t know.

By the way with the new EQ-settings (suggested by @QMuse) the dip around 80 Hz is almost gone. There is still one around 100 Hz. It got smaller by tuning the delay, as @hyperplanar suggested, so time aligning may be a good strategy for this particular dip. I did not manage to do it perfectly yet, but it is getting closer.

That´s how the last try looked like (dip around 300 hz has something to do with my desk/screen-situation and changes if i move the screen, so it can be ignored here):

RTA MMM of all speakers:
View attachment 57073

Measure left speaker + sub with sweep starting from 10Hz from your LP. Use Estimate IR delay to adjust delay of HF to zero. Go to Spectrogram and set Wavelet mode params as shown below. That graph should show sub delay relative to left main.

 

[DJBonoBobo]

Thanks, that was interesting! I wonder if i understood your suggestion correctly.

Before:

After (added 14,2ms):

What i got (RTA MMM - black is new, red the last one i posted above; ignore >200hz as this is due to screen-position) - Dip between 80 and 100 Hz ist gone. EQ is a little bit different, that´s why there´s difference under 70 hz, too.

 

[QMuse]

Thanks, that was interesting! I wonder if i understood your suggestion correctly.

Before:
View attachment 57180

After (added 14,2ms):
View attachment 57181

What i got (RTA MMM - black is new, red the last one i posted above; ignore >200hz as this is due to screen-position) - Dip between 80 and 100 Hz ist gone. EQ is a little bit different, that´s why there´s difference under 70 hz, too.
View attachment 57184

You did understand it correctly, and IMO your response is clearly much better now. You can try to add few ms more to see if spectrum response would improve further.

Btw, what you can also try is to boost a little 100-160Hz region a little with filter at 125Hz, Q=4, Gain=+3dB

 

[DJBonoBobo]

Just to close this chapter correctly, here is my preliminary final result. I will now listen to it for a while and see how satisfied I am in the long run.
First of all, thanks again for the interesting suggestions. I learnt a lot and got some motivation to improve my situation, even I finally did draw some other conclusions. Again I speak only from my experience and I can´t and won´t generalize.

After some time of listening with a longer delay for the mains I was still not really satisfied. It´s hard to explain, but subjectively i thought something was "off". Maybe that was just psychology - i don´t know. I then had the opportunity to get advice from an technical expert who is especially (very) familiar with the KH 750. He strongly recommended to use the delay settings suggested by the Neumann app when entering the listening distance (in my case ultimately 2ms delay for the mains). He did not recommend group delay measurements or the wavelet-spectrogram for this situation. For improvement, he recommended above all to find a better position for the sub. I then tried a lot of things again and in the end I changed the position only slightly but decisively. I turned the sub slightly (front diagonal facing to the wall and even closer to the wall). I also experimented with the position of my desk, which had a surprisingly strong effect on the bass FR.

It also helped a lot that I learned that it can be very useful to set eq-filters with positive values. In the past I had the wrong assumption that you should avoid this.

Below are RTA MMM measurements of all speakers together (upper bass and lower mids are influenced by window in front wall, desk and screen - please ignore, quite low bass level relative to other "house curves" is intentional because of my personal preference).
Green is the new one, black is the last one i posted above (15ms delay, different positions of sub, desk and screen, different EQ-settings).

Please note that i don´t think the new (green) FR is "better" than the black one below 100Hz. Over the whole spectrum the black one is much better, of course. My point is that it was possible to get a good response below 100Hz without setting an additional delay of 15ms instead of 2ms. Even if it´s only for psychological reasons i´m subjetively more satisfied with the new settings. I will not argue against opinions or empirical findings that this kind of delay should not matter, though. It´s just my personal perception.

PS: The new dip around 100Hz is clearly some phase-cancellation i avoided with the older setting.

Settings in the Neumann app:

 

[QMuse]

Well, dip at 90-100Hz is back, suggesting sub integration problem. As it is accompanied with quite uneven response in 100-200Hz I really doubt that green can sound better than black. In fact I'm pretty sure it does not.

 

[DJBonoBobo]

Fair point, but hopefully i will see/hear in the long run.
Indeed, dip between 90 and 100 is back. But at least the original dip between 70-100 is smaller now compared to where i started.

 

[QMuse]

But at least the original dip between 70-100 is smaller now compared to where i started.

Not really. Dip at 70-100Hz has the same depth with green and black curve - all you need is a small adjustment of black curve 65Hz and 90Hz to make it equal to the response of the green curve.

Don't get me wrong here - green line indeed points you have found a better location for the sub, but all other things you did IMHO opinion resulted in worse curve.

 

[DJBonoBobo]

I meant the one in the first post of this thread, not compared to this black curve.
I´m not arguing against your opinion - i see what you mean. As i wrote - maybe it´s only psychology.

 

[QMuse]

Thanks, that was interesting! I wonder if i understood your suggestion correctly.

Before:
View attachment 57180

After (added 14,2ms):
View attachment 57181

What i got (RTA MMM - black is new, red the last one i posted above; ignore >200hz as this is due to screen-position) - Dip between 80 and 100 Hz ist gone. EQ is a little bit different, that´s why there´s difference under 70 hz, too.
View attachment 57184

I don't what arguments your expert friend has for setting the delay to 2ms as this measurement clearly proves you did it the right way.

 

[DJBonoBobo]

I don´t know the arguments because it´s not actually a friend and i didn´t talk to him directly. Maybe the advice was specific to the Neumann-setup with 750 and 310, because the 750 DSP includes specific additional filtering for the connected analog Neumann-mains (you specify what monitors you use when setting the app up). But i´m not sure about this.
I think i made clear that i had no intention to question your advice generally.

 

[QMuse]

I don´t know the arguments because it´s not actually a friend and i didn´t talk to him directly. Maybe the advice was specific to the Neumann-setup with 750 and 310, because the 750 DSP includes specific additional filtering for the connected analog Neumann-mains (you specify what monitors you use when setting the app up). But i´m not sure about this.
I think i made clear that i had no intention to question your advice generally.

I don't mind if you or him question my advices, I was just curious about arguments he provided.