Dirac and similar

[digicidal]

Yeah that's what I figure... but as the post was preceded by:

The Speaker Boundary Interference Response or SBIR as depicted in my previous post. Or also that interference introduced at listener seat (by boundary interaction). I am sure this is very trivial knowledge here. I don't adjust for that in EQ, it is already fixed in speaker design and setup.

I found it a little confusing... but it is late and I am quite tired and maybe a little stupid (well a little more than normal I mean).

 

[Thomas_A]

Can you pls post that graph with 1/12 smoothing?

Btw, it seems that panels you put behind your speakers didn't really prevent that dip at 80Hz.

No, and it should not, panels are designed for higher f. I can post with 1/12 smoothing but I am occupied at the moment, so later.

 

[Krunok]

No, and it should not, panels are designed for higher f. I can post with 1/12 smoothing but I am occupied at the moment, so later.

It would actually be interesting if you can post measurements with and without rear panel (both with 1/12 smoothing) to see the difference.

 

[Thomas_A]

Also the center of the mid woofer (80-3000 Hz) is 35 cm from wall, so the reason for the dip @ 80 Hz is not known at the moment. Since I am building new subs and will include parametric EQ <100 Hz I have not bothered yet with this.

 

[Krunok]

Also the center of the mid woofer (80-3000 Hz) is 35 cm from wall, so the reason for the dip @ 80 Hz is not known at the moment. Since I am building new subs and will include parametric EQ <100 Hz I have not bothered yet with this.

You didn't specify details about measurement you posted: is it showing onne or both speaker response? Is it a sweep or RTA? Was it made on a single spot or is it a spatial average?

It is hard to judge that dip without knowing if it occurs only at a isolated spot or throughout a wider area.

 

[Thomas_A]

You didn't specify details about measurement you posted: is it showing onne or both speaker response? Is it a sweep or RTA? Was it made on a single spot or is it a spatial average?

It is hard to judge that dip without knowing if it occurs only at a isolated spot or throughout a wider area.

One speaker, 1 s sweep, single spot, listening position (the above one is an older one, I've made changes in the x-over since that, but that only affects some dB in the 1-3 kHz range). I will disconnect the subs and unplug the ports to use the top speakers to measure +/- panel and different wall distances; the will be good from 40 Hz and up. But it takes a while, these sweeps are neither really family- nor neighbour-friendly.

 

[Krunok]

One speaker, 1 s sweep, single spot, listening position (the above one is an older one, I've made changes in the x-over since that, but that only affects some dB in the 1-3 kHz range). I will disconnect the subs and unplug the ports to use the top speakers to measure +/- panel and different wall distances; the will be good from 40 Hz and up. But it takes a while, these sweeps are neither really family- nor neighbour-friendly.

LOL Very true!

I actually use RTA (pink noise) and move microphone around LP to get spatial averaged measurement. I use sweeps only when I need to correct phase.

 

[Thomas_A]

This is another measurement made previously, left speaker, 1s sweep, listening position, one point. Now smoothed 12dB/octave.

 

[Krunok]

This is another measurement made previously, left speaker, 1s sweep, listening position, one point. Now smoothed 12dB/octave.

View attachment 32808

From 160Hz upwards it looks ok. Everthing below that I believe can be fixed with room EQ. Pretty much usual room related stuff.

That dip at 74Hz seems to be part of the wider depression in the 60-160Hz range. Below 60Hz response is obviously dominated by that huge peak at 46Hz.

 

[Thomas_A]

From 160Hz upwards it looks ok. Everthing below that I believe can be fixed with room EQ. Pretty much usual room related stuff.

That dip at 74Hz seems to be part of the wider depression in the 60-160Hz range. Below 60Hz response is obviously dominated by that huge peak at 46Hz.

i

Yep that basically summarise it but not sure yet if there is something else 100-200 Hz. The panels also loose capacity sharply in that region. I had other ones previously good to 100 Hz. But since I don't really have a sub worth being called a sub, I'll wait to work with Thebissues after that. The new ones will be tuned to 21 Hz. I used to have the 46-47 Hz peak tuned down when I had the Behringer parametric EQ. But that system is long gone now.

 

[Krunok]

i

Yep that basically summarise it but not sure yet if there is something else 100-200 Hz. The panels also loose capacity sharply in that region. I had other ones previously good to 100 Hz. But since I don't really have a sub worth being called a sub, I'll wait to work with Thebissues after that. The new ones will be tuned to 21 Hz. I used to have the 46-47 Hz peak tuned down when I had the Behringer parametric EQ. But that system is long gone now.

Maybe that dip is not a result of cancellation because of reflection from the rear wall but from the other surface.

Anyway, I'm very curious to see measurements with and without rear panels.

 

[Thomas_A]

Maybe that dip is not a result of cancellation because of reflection from the rear wall but from the other surface.

Anyway, I'm very curious to see measurements with and without rear panels.

Yes, I agree, this interesting. In the meantime, waterfall plots show that ≈47 Hz and ≈87 hz peaks show up. It is the same as the theoretical modes in the room. Other than that, rather clean.

 

[Krunok]

Yes, I agree, this interesting. In the meantime, waterfall plots show that ≈47 Hz and ≈87 hz peaks show up. It is the same as the theoretical modes in the room. Other than that, rather clean.

View attachment 32818

It looks quite nasty. Can you pls show it after 500ms instead of 1000?

 

[Thomas_A]

It looks quite nasty. Can you pls show it after 500ms instead of 1000?

 

[Krunok]

View attachment 32824

This is how my left channel looks, right is similar.

 

[Thomas_A]

Is that before or after EQ?

 

[Thomas_A]

The reverbant in numbers;

 

[Krunok]

Is that before or after EQ?

After.

 

[Krunok]

The reverbant in numbers;

View attachment 32828

That one really looks good and is better than mine for app 100ms throughout the range.

Btw, usually Topt is shown instead of T20.

 

[Krunok]

I just ran into this interesting paper from Dr. Geddes. Although it is about placing multiple subs it contains many interesting thoughts related to what we discussed here.