REW Measurements - What does a good system measure like in the time / frequency domain?

[TomJ]

Could you attach the REW files? Curious to see what the raw measurements look like

Hey David, here's a zipfile of the .mdat files from our previous place. I never saved the files from our current place (first post).

It makes sense that the number of reflections is the same before and after DRC and only their properties differ.

Good luck with your project, hope you get to a final result that you like. Wish I could be more helpful as to the interpretation and practical value of the IR analyses. It does seem to be a general consensus that FR is the primary consideration, but you're on the right track to use ETC latencies to identify the principal reflections and assess room treatment options.

cheers, Tom

 

[ernestcarl]

David, nice analysis and mitigation.
FYI here's how DRC alone with no room treatment or furniture changes improved the temporal response of the same sound system 2 years ago in our previous place, a "concrete box" with lots more acoustic problems (eg top chart) than our current place. I just found those .mdat files and generated ETC charts on the IR before and after DRC (middle, bottom). I never looked at the IR before, surprised actually by how much Dirac improved it in such a difficult space.
cheers, Tom

View attachment 191105

I'd be curious to see the before and after moving microphone measurements (MMM) rather than just only from a static single point.

Uncorrected IR is inverted. DRC seems to have done a good job -- notwithstanding a few elevated decay peaks after correction and remaining long decay with strong boundary reflections still visible in the cumulative decay graphs & wavelet spectrograms -- those can only truly be fixed with improved room acoustics.

 

[TheBatsEar]

...those can only truly be fixed with improved room acoustics.

The last, and i think most pricey, frontier. Gear and massaging the signal can only do so much ...

 

[ernestcarl]

The last, and i think most pricey, frontier. Gear and massaging the signal can only do so much ...

That is quite unfortunately true. Even the author of DRC-FIR says that his software works even better in a room with good acoustics already in place.

 

[TomJ]

I'd be curious to see the before and after moving microphone measurements (MMM) rather than just only from a static single point.

Uncorrected IR is inverted. DRC seems to have done a good job -- notwithstanding a few elevated decay peaks after correction and remaining long decay with strong boundary reflections still visible in the cumulative decay graphs & wavelet spectrograms -- those can only truly be fixed with improved room acoustics.

Thank you for your further analyses and thoughts. Yes, everything you say is consistent with the acoustics of that large room which had stone floors, concrete ceilings, a glass wall, ceiling beams, HVAC duct resonances and more. Dirac 3 improved the SQ more than I expected. The SQ of the grand piano was unfortunately hopeless, beyond redemption. This was temporary housing for us, in Taiwan actually. When we moved back to San Francisco the following year I didn't save any data files from this project except for what I posted here.

 

[ernestcarl]

Thank you for your further analyses and thoughts. Yes, everything you say is consistent with the acoustics of that large room which had stone floors, concrete ceilings, a glass wall, ceiling beams, HVAC duct resonances and more. Dirac 3 improved the SQ more than I expected. The SQ of the grand piano was unfortunately hopeless, beyond redemption. This was temporary housing for us, in Taiwan actually. When we moved back to San Francisco the following year I didn't save any data files from this project except for what I posted here.

No prob… I actually thought it was DRC-FIR used not Dirac… well, good to know. I’m always wondering what room correction EQ method people use. Not always so obvious to me just looking at measurements as some of these perform very similarly.

 

[TomJ]

For the ETC I think we're not actually looking at less reflections, only a more sharply defined first peak, and thus when scaled to % it looks like the rest is all attenuated - but I could be wrong here.

FYI here's another view of the same raw data showing IR not ETC during the 1st ms, without (top) and with Dirac 3. Note the interesting differences in pre-ringing and transient recovery, also how short the latency appears to be for Dirac filter processing on the SHD Studio.

A transient like this is useful for modeling and analysis but too short for us to hear. It's helpful to think of an audible transient response as an "event", and in this case, the μs scale Dirac test pulse as one subcomponent thereof. Our temporal hearing limit is about a half ms (shorter than previously thought) according to a Genelec sponsored study published in IEEE/ACM Trans. 2021 which has probably been discussed elsewhere on this forum:
summary - https://www.newswise.com/articles/the-human-ear-detects-half-a-millisecond-delay-in-sound
publication - https://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=6570655

 

[TheBatsEar]

FYI here's another view of the same raw data showing IR not ETC during the 1st ms, without (top) and with Dirac 3. Note the interesting differences in pre-ringing and transient recovery, also how short the latency appears to be for Dirac filter processing on the SHD Studio.

A transient like this is useful for modeling and analysis but too short for us to hear. It's helpful to think of an audible transient response as an "event", and in this case, the μs scale Dirac test pulse as one subcomponent thereof. Our temporal hearing limit is about a half ms (shorter than previously thought) according to a Genelec study published in IEEE/ACM Trans. 2021 which has probably been discussed elsewhere on this forum:
summary - https://www.newswise.com/articles/the-human-ear-detects-half-a-millisecond-delay-in-sound
publication - https://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=6570655
View attachment 191327

That looks awesome. I guess everything behind the signal was the room or reflections? Someone should measure this at pre-out or something, to remove room/reflections.

But this shows clearly that Dirac does more than just bend the FR.

 

[Naughtius]

After two weekends of dragging furniture (and guest bedroom mattresses) around, spreading blankets all over hard surfaces I could find, playing with REW, RePhase, DRC, Equalizer APO and Dirac Live, and listening to all my favorite songs, I have arrived at the most satisfying audio setup I have ever had in any of my homes.

My main complaint at first was that although my frequency response looked quite good, the sound was "messy". Most improvements I found were in the higher frequencies in the time domain - the before / after ETC comparison shows a lot:

Pretty much in order of most to least significant increase in perceived sound quality, these were the steps I took in the process:

• Moved the coffee table out of the way and placed woolen blankets all over the floor
  • Helped against first, and second / third reflections from the ceiling
• Rotated my entire setup 90 degrees, moved my speakers closer together and moved the sofa closer
  • Not super practical, but gives a symmetrical setup with side walls at 1.5 meters from the speakers
  • No more reflections from the right wall
  • Final speaker to speaker distance is 2.2m, listening position is 2.8m from each speaker.
  • Great increase in imaging / stereo width compared to the asymmetrical setup
• Switched to a different amplifier
  • Less audible noise
• Places mattresses behind the speakers
  • Minor increase in mid bass performance
• Placed a woolen blanket over the sofa
  • Removed minor reflections coming from the back cushioning
• Time domain EQ to align speaker drivers (Dirac / RePhase)
  • Looks very pretty in the graphs but I haven't heard a difference (yet)

In my EQ I removed 90% of the filtering I originally had. I'm now listening with only a high shelf against the Klipsch's (RP280F's) famous treble and 3 peaking filters to dim some of the room modes - all below 150hz - and am honestly amazed by the sound these $449 speakers produce.

I'd like to thank everyone that helped me out with this - Especially @ppataki for introducing me to time domain corrections in Dirac Live, @Hipper for the great pointers on improving systems in general, @ernestcarl for personally diving into my measurements.

I also hope to inspire anyone ever reading this to spread metaphorical blankets on their floor - I hugely underestimated what room acoustics / room treatment could do and couldn't have imagined the increase in enjoyment I'm getting from these speakers.

All the best!
- David

 

[Holmz]

…

I also hope to inspire anyone ever reading this …
All the best!
- David

It’s working.

 

[Trouble Maker]

At what point did your partner leave the house and you didn't notice?

So glad your journey went well, definitely inspiring! Unfortunately one of those 'one day' kind of things at the moment.

 

[Hipper]

I also hope to inspire anyone ever reading this to spread metaphorical blankets on their floor - I hugely underestimated what room acoustics / room treatment could do and couldn't have imagined the increase in enjoyment I'm getting from these speakers.

Same here when I first started on this road. It's too easy to get into the 'spend more on equipment' frame of mind. More expensive (perhaps I should say 'better') equipment, chosen wisely, can improve things, particularly speakers and an associated amp, but it pales in comparison with positioning, room treatment and DSP/EQ.

Anyway, congratulations on pursuing this project. You now have tools and concepts to create good sound in any domestic setting.

PS. Is your sofa leather? They do apparently reflect. I use a fabric chair.

 

[tjcinnamon]

'I'm still not quite happy with the sound as it is.'

Are you able to pin point what you are not happy with? Bass, vocals, imaging?

What does a good system measure like in the time / frequency domain?​

Generally you want a smooth measuring response. For example the frequency response should not have sharp ups and downs but smoother undulations aiming towards flat, especially in the bass region - around 30-300Hz (bearing in mind your speakers probably go down to 30/40Hz). Overall I like flat but some like a slope with, say, 30Hz being 6dB higher then 10kHz (what are called 'house curves' and there are various preferences with these).

Actually, the best question is 'what does a good system sound like'. It's too easy to get caught up in measurements. It's what it sounds like to you that is the most important.

Generally it is best to solve bass problems first. These are the most difficult to deal with but when done allow the rest of the music to be revealed.

To solve bass issues involves up to four methods which can be use individually or together depending on your domestic situation and finance.

1. Positioning of speakers and listening chair (Ears).
2. Room treatment - bass traps etc..
3. Sub woofers - one or more carefully positioned.
4. DSP/EQ (e.g Dirac).

1. Cost's nothing but time and effort.
2. Costs something and may not be domestically acceptable.
3. Costs and takes time and effort to integrate.
4. Costs and takes time and effort to learn and understand. Dirac is about as easy as it gets.

I posted some stuff on my efforts here (I use 1, 2 and 4 - no subs) - see post 60 - which may help:

https://www.audiosciencereview.com/...in-room-measurements.13540/page-3#post-411614

100%

The best sounding curve to me is a massive boost from 20Hz to 90Hz then a check mark that starts to rise around 6000Hz. I've stumbled into this a few times with a few DRC solutions. I can DRC flat if I want too.

 

[ppataki]

The best sounding curve to me is a massive boost from 20Hz to 90Hz

+1
I can totally second that - in my experience that will give you a very pleasant and impactful bass experience