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

[Naughtius]

I've been looking to (and working on) improve the stereo setup in my new place for a while now; Mainly moving the speakers around, applying EQ (on a miniDSP-like setup), and recently (making quite a large impact) moving aside my large oak coffee table. The current setup is quite basic:

On the left is open space for ~5 meters, on the right is a hard wall / window with curtains, and behind the couch I'm sitting there's about 1 meter of space before the back wall. There's no room treatment besides a 200 cubic feet foam bean bag against that wall. The current (MMM) frequency response over the 3 seater sofa (with EQ) looks like this:

I'm still not quite happy with the sound as it is - I've heard many better systems, but am not really sure on what to improve from this point onward. I've been looking at step responses and impulse responses, but can't quite find information on what these should look like and how (significantly) that influences the sound. The same goes for waterfall graphs and spectrograms.

Room treatment wise I read that rugs are heavily recommended, thick absorption behind the speakers 'helps', ceiling treatment is good, side reflections can kinda stay, and generally filling your walls with panels helps dampening the room - but - I find it hard to link those improvements to actual measurements (and thus keep track of whether it's objectively helping).

Could some of you provide some guidance on these time / frequency domain measurements translate to perceived sound? I'd love to be able to work towards measurable goals in treating the room / perhaps purchasing new speakers / bi-amping these to time align the drivers (if that does anything significant). I've included my REW measurements of the room as it is.

Many thanks!
- David

Appendix pictures:

 

[Trouble Maker]

Not an expert, but this lower area around 350-800hz can't be great right?

Note: Not any particular target curve, just a quick and dirty visual linear best fit to show that area more easily. Blue line at same slope offset down to easily show about how many dB down on SPL scale.

 

[TomJ]

Congrats on your new place, nice view! DRC can be very effective and at a much lower cost than the other options you've mentioned. For example here's the post-DRC in-room FR of my 20+ year old B&W 805 Nautilus at my typical listening level. I didn't measure the temporal response. I use the miniDSP SHD Studio for Dirac v3 DRC, also network streaming. Hope that's helpful.

 

[Naughtius]

Not an expert, but this lower area around 350-800hz can't be great right?

View attachment 190337
Note: Not any particular target curve, just a quick and dirty visual linear best fit to show that area more easily. Blue line at same slope offset down to easily show about how many dB down on SPL scale.

Thanks for checking! I think this happened after moving another sofa on the left side of the picture - I'll have to dial that in again. You'd personally aim for frequency response only? I'm mostly wondering what I should aim for at the time domain side.

Congrats on your new place, nice view! Dirac v3 can be very effective and at a much lower cost than the other options you've mentioned. For example here's the Dirac filtered in-room FR of my 20+ year old B&W 805 Nautilus at my typical listening level. I didn't measure the temporal response. I use the miniDSP SHD Studio for network streaming and DRC and couldn't be happier with it. FWIW its nanoPi/Volumio network interface is completely stable over RJ45 cable but unstable on wifi if you use the USB dongle they provide. I stream wifi by using a small router next to the stereo rack as a WAP and running an RJ45 cable from that to the SHD. That's 100% stable with 192/32 UPnP Qobuz and local file streams on Audirvana and Internet radio streams on Volumio, no dropouts. Hope that's helpful.

View attachment 190341

Thanks! That's looking damn pretty for such small speakers. Do you have any room treatment / have you ever looked at the time domain in your room?

 

[thorvat]

Thanks for checking! I think this happened after moving another sofa on the left side of the picture - I'll have to dial that in again. You'd personally aim for frequency response only? I'm mostly wondering what I should aim for at the time domain side.

Phase response looks perfect but that wide dip centered around 450Hz is audible so you may want to correct it. As getting the frequency response right is far more important than šhase response you may want to base your correcttion on the spatially averaged measurement rather than on a single sweep.

 

[TomJ]

Thanks! That's looking damn pretty for such small speakers. Do you have any room treatment / have you ever looked at the time domain in your room?

No room treatment. It's a mid size living room with some acoustic complications, eg a grand piano on one side and glass wall along the other. Re LF, I used to have a sub but eventually stopped using it. Temporal response is a complicated subject. That was a factor when I bought these speakers two decades ago to replace my KEF 105's (the 805N sounded more musical and coherent to me than the 802N and 803N, was surprised by that), but ever since I've been so happy with the imaging that I haven't thought further about it.

 

[Naughtius]

Phase response looks perfect but that wide dip centered around 450Hz is audible so you may want to correct it. As getting the frequency response right is far more important than šhase response you may want to base your correcttion on the spatially averaged measurement rather than on a single sweep.

I'll get to it once the furniture has found more definitive places! The measurement shown is a 2 minute MMM average across the entire 3 seater sofa, should be average enough. What's your opinion on managing the time domain? That's what I'm most curious about, but all the responses so far focus solely on the frequency response.

No room treatment. It's a mid size living room with some acoustic complications, eg a grand piano on one side and glass wall along the other. Re LF, I used to have a sub but eventually stopped using it. Temporal response is a complicated subject. That was a factor when I bought these speakers two decades ago to replace my KEF 105's (the 805N sounded more musical and coherent to me), but ever since I've been so happy with the imaging that I haven't thought further about it.

For me the realization I should dive in there happened when moving my coffee table out of the way and noticing the improvement in clarity it brought - I want more of that.

 

[ppataki]

Dirac Live 3 will manage your time domain perfectly
It will sync the drivers in the time domain (yes, even for passive systems, by applying frequency dependent time shifting)
You will see that very clearly on your step response curve before/after - and you will hear the difference too
I have done that on at least half a dozen systems - I will post some measurements here later today about one of my previous system's step response curves (Nubert nuVero 140 speakers; 3.5-way passive towers)

 

[Naughtius]

Dirac Live 3 will manage your time domain perfectly
It will sync the drivers in the time domain (yes, even for passive systems, by applying frequency dependent time shifting)
You will see that very clearly on your step response curve before/after - and you will hear the difference too
I have done that on at least half a dozen systems - I will post some measurements here later today about one of my previous system's step response curves (Nubert nuVero 140 speakers; 3.5-way passive towers)

That's quite interesting! I'd love to see those before / after measurements

 

[EEE272]

I also really look forward to the measurements. Cool!

Stupid question but in the images I only see one measurement. Is this for left or right? Are the two similar?

I think your problem might be mostly related to the asymmetry, not the frequency response.
Is there a possibility to place everything diagonally? I assume you don't want to place the speakers in front of the really nice view.

With diagonal, I mean moving the right speaker symmetric to the corner on the right wall and shift your listening position to the forward left.

I would also move the speakers a bit away from the walls. The reflection could be responsible for the hole around 300-800 Hz.

 

[thorvat]

I'll get to it once the furniture has found more definitive places! The measurement shown is a 2 minute MMM average across the entire 3 seater sofa, should be average enough. What's your opinion on managing the time domain? That's what I'm most curious about, but all the responses so far focus solely on the frequency response.

Yes, that is certainly enough.

Regarding the time domain, assuming you are going to do phase correction mannually, the things pretty much boil down to 3 areas:

- compensating for the phase error of the passive XO - judging by the look of your step response you already did that succesfully
- making the phase in the LF range between left and right speaker as equal as possible in order to avoid bass cancellation
- getting phase response as close to the minimum phase so excess phase is as clode to zero as possible

When making phase filters use low Q values (1, or max 2) and keep number of filters to minimum, otherwise you will introduce preringing. This will be audible and also visible in step response.

Be aware that phase correction doesn't improve sound quality not even nearly as frequency correction does. Once again, be aware that if you introduce preringing with phase correction you will get things worse and not better.

 

[abdo123]

I've been looking to (and working on) improve the stereo setup in my new place for a while now; Mainly moving the speakers around, applying EQ (on a miniDSP-like setup), and recently (making quite a large impact) moving aside my large oak coffee table. The current setup is quite basic:

View attachment 190319

On the left is open space for ~5 meters, on the right is a hard wall / window with curtains, and behind the couch I'm sitting there's about 1 meter of space before the back wall. There's no room treatment besides a 200 cubic feet foam bean bag against that wall. The current (MMM) frequency response over the 3 seater sofa (with EQ) looks like this:

View attachment 190320

I'm still not quite happy with the sound as it is - I've heard many better systems, but am not really sure on what to improve from this point onward. I've been looking at step responses and impulse responses, but can't quite find information on what these should look like and how (significantly) that influences the sound. The same goes for waterfall graphs and spectrograms.

Room treatment wise I read that rugs are heavily recommended, thick absorption behind the speakers 'helps', ceiling treatment is good, side reflections can kinda stay, and generally filling your walls with panels helps dampening the room - but - I find it hard to link those improvements to actual measurements (and thus keep track of whether it's objectively helping).

Could some of you provide some guidance on these time / frequency domain measurements translate to perceived sound? I'd love to be able to work towards measurable goals in treating the room / perhaps purchasing new speakers / bi-amping these to time align the drivers (if that does anything significant). I've included my REW measurements of the room as it is.

Many thanks!
- David

Appendix pictures:
View attachment 190323

View attachment 190327

View attachment 190325

Great decay times for a residential space! Might wanna invest in some helmholz resonators for the lowest of octaves.

 

[ppataki]

That's quite interesting! I'd love to see those before / after measurements

Here are the step response of my former Nubert nuVero 140 speakers (3.5-way tower speakers)

(highlighted curve is with Dirac)

You can see that:
- it synced the drivers so there is only one peak at 0ms (instead of the three separate peaks in the before curve)
- it seriously reduced the amount of ringing (you can see the peaks around 30 and 70ms are much smaller)
- it did not introduce pre-ringing since it uses a mixed-phase algorithm (pre-ringing would be a slight hump before 0ms)

So I would strongly recommend trying it - the sound will be way better vs only using regular EQ corrections

 

[alex-z]

First, you have a pretty big difference in the response of the left and right channels between 600 and 2000Hz which shows through in the impulse response as well.

That could have a pretty detrimental effect on stereo imaging, and I would try more symmetrical speaker placement within the room. If that is not possible, absorption for the right wall. Even something 2" thick would help, although 3.5" is a better bet.

You have some weird distortion peaks at 1000, 2000, 3000, and 4000Hz. Is there a problem with the measurement mic, or the amp powering the speakers?

All things considered, the response below 400Hz is pretty good, but there is still some elevated decay times. Nothing terrible, but I would put some 5.5" absorbers on the ceiling just to balance it out. Plus that will help with the nature of your speakers having lackluster vertical directivity but good horizontal directivity.

The entire treble region seems a bit elevated. I would consider pulling down 2-3dB above 1000Hz and evaluating if you like the change.





Adding a properly integrated sub would help with the bass deviations below 100Hz, particularly that 55Hz dip.

 

[LTig]

For me the realization I should dive in there happened when moving my coffee table out of the way and noticing the improvement in clarity it brought - I want more of that.

Then try a carpet between sofa and speakers, to reduce reflections on the floor.

 

[TheBatsEar]

Here are the step response of my former Nubert nuVero 140 speakers (3.5-way tower speakers)

(highlighted curve is with Dirac)

View attachment 190397

Awesome. I have ordered a MiniDSP Flex, for now without Dirac, but i'm considering it even more now.

 

[Hipper]

'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

 

[Naughtius]

Yes, that is certainly enough.

Regarding the time domain, assuming you are going to do phase correction mannually, the things pretty much boil down to 3 areas:

- compensating for the phase error of the passive XO - judging by the look of your step response you already did that succesfully
- making the phase in the LF range between left and right speaker as equal as possible in order to avoid bass cancellation
- getting phase response as close to the minimum phase so excess phase is as clode to zero as possible

When making phase filters use low Q values (1, or max 2) and keep number of filters to minimum, otherwise you will introduce preringing. This will be audible and also visible in step response.

Be aware that phase correction doesn't improve sound quality not even nearly as frequency correction does. Once again, be aware that if you introduce preringing with phase correction you will get things worse and not better.

This is good stuff! How did you judge the phase error from the step response? I was considering bi-amping the speakers to have a separate EQ with filters / delay on all LF-L, LF-R, HF-L and HF-R.

Interesting read on preringing on FIR filters, I haven't properly looked at that yet, thanks for all the knowledge so far

 

[Naughtius]

Great decay times for a residential space! Might wanna invest in some helmholz resonators for the lowest of octaves.

Thanks! Which figures did you look at for this? And what values would one typically aim for here?

Any improvements over the big concrete box I'm in are probably due to my 110kg foam beanbag, here's a photo from when I just moved in:

 

[Naughtius]

Here are the step response of my former Nubert nuVero 140 speakers (3.5-way tower speakers)

(highlighted curve is with Dirac)

View attachment 190397

You can see that:
- it synced the drivers so there is only one peak at 0ms (instead of the three separate peaks in the before curve)
- it seriously reduced the amount of ringing (you can see the peaks around 30 and 70ms are much smaller)
- it did not introduce pre-ringing since it uses a mixed-phase algorithm (pre-ringing would be a slight hump before 0ms)

So I would strongly recommend trying it - the sound will be way better vs only using regular EQ corrections

That's a good looking improvement! I activated a Dirac Live trial on my laptop and give it a go as well - Here's the measurements I'm getting compared to the IIR filters I was using. How would you interpret these differences?