Room Measurement Tutorial for Dummies Part 2

[RayDunzl]

how did you do the DSP corrections?

REW plays a swept sine tone through the speakers, and listens with a measurement microphone.

A sine wave (swept from low to high frequency) is the test. Takes a few seconds (or longer depending on what you set for the time).

A sine wave is easily described mathematically, both for generation, and for comparing the return to what was sent. FFT does the magic of transforming what the mic heard into a graphic format.

That's for "just looking".

REW can create some corrective filters for various devices, but I don't use it for that.

---

For correction:

AcourateDRC (software at the PC) sends three swept sine tones, Left, right, and Left again.

It records the results from the microphone.

It compares what was sent, to what was received, and its non-trivial software creates a "filter" to adjust the signal (amplitude and phase) to (somewhat) match a user selected "curve".

In my case, if I look at the filter data, I can display it in a spreadsheet, graph the data, and it graphs as an Impulse Response, with (in my case) 6144 data points. If the filter were empty (no modification) it has only one data point set (to 1), the rest are 0. I remain ignorant as to exactly how the filter coefficients modify the sample data that pass through it.

Here's some of my FIR filter data:
b0 = 0.0,
b1 = 0.0,
b2 = 1.1500598650487914e-13,
b3 = 6.905641965378184e-13,
b4 = 2.303613029497331e-12,
...
b6139 = -1.567789734840952e-12,
b6140 = -4.622445004889841e-13,
b6141 = -7.591199397598627e-14,
b6142 = 0.0,
b6143 = 0.0,


Graphically, zoomed in near the center (400 of the 6144 data points)

That filter is downloaded to a miniDSP OpenDRC-DI, which sits in the digital path between the source and the DAC.

The signal (music, TV, whatever) is adjusted by the filter applied to the DSP (the signal data is "convolved" with filter data. I'm ignorant on this part).

Other folks may perform that function in the PC, if they are using the PC as a source, which I mostly don't, so I picked a little box to set on the rack and intercept any digital signal source over S/PDIF.

 

[Deleted member 65]

REW plays a swept sine tone through the speakers, and listens with a measurement microphone.

A sine wave (swept from low to high frequency) is the test. Takes a few seconds (or longer depending on what you set for the time).

A sine wave is easily described mathematically, both for generation, and for comparing the return to what was sent. FFT does the magic of transforming what the mic heard into a graphic format.

That's for "just looking".

REW can create some corrective filters for various devices, but I don't use it for that.

---

For correction:

AcourateDRC (software at the PC) sends three swept sine tones, Left, right, and Left again.

It records the results from the microphone.

It compares what was sent, to what was received, and its non-trivial software creates a "filter" to adjust the signal (amplitude and phase) to (somewhat) match a user selected "curve".

Here, that filter is downloaded to a miniDSP OpenDRC-DI, which sits in the digital path between the source and the DAC.

The signal (music, TV, whatever) is adjusted by the filter applied to the DSP (the signal data is "convolved" with filter data. I'm ignorant on this part).

Other folks may perform that function in the PC, if they are using the PC as a source, which I mostly don't, so I picked a little box to set on the rack and intercept any digital signal source over S/PDIF.

I'll give this a go since I don't entend to aquire any new SW/HW - - > http://i.nextmedia.com.au/Assets/evolution_acoustics_mmmicroone_speakers_review_test_lores.pdf

 

[amirm]

I guess my question is how to process the result from measurements and generate something I can load into Roon correcting whatever needs to be corrected.

You are forcing me to do this write-up sooner than later .

For now, all you need to do is go into Roon and use the parametric EQ to dial down those two peaks at low frequencies. Once there, you may need a "shelf" to boost them to higher level.

 

[FrantzM]

Ok It's official... ASR is NOW .... my new "have-to0-visit-each-and-every-day" place on the Internet... You are simply G-R-E-A-T!!!.

I have the LSR 308 for what I thought would be "educational" purposes ... so far .. they're play9ing above what we, audiophiles, would tend to think for such a small cash outlay .. no correction yet ...

 

[Sal1950]

Ok It's official... ASR is not my new "have-to0-visit-each-and-every-day" place on the Internet... You need to discuss other stuff more people .. You are simply G-R-E-A-T!!!.

What?

 

[Deleted member 65]

Followed this tutorial from Roon Community - - > https://community.roonlabs.com/t/a-guide-how-to-do-room-correction-and-use-it-in-roon/23800

1. Measured Left speaker (LS)
2. Measured Right speaker (RS)
3. Pressed EQ having focus on LS
4. In the equalizer window selected:
4a. “Var smoothing” from options
4b. Selected “Generic” equalizer
4c. Selected “None” as speaker
4d. Pressed “Set target level” text
4e. Finally pressed “Match response to target”
5. Repeated steps 3 - 4e for RS.
6. In REW's main window, selected menu “File -> Export -> Export filter impulse response as wav”.
7. In Roon:
7a. Settings - Audio - Select Device – DSP Engine – Convolution - Load Wav-file created in step 6.

Result: Extremely distorted sound ... :-(

 

[RayDunzl]

Followed this tutorial

"If you have to read the directions you don't know what you're doing." -RayDunzl

(I've been there, its just that I suddenly thought that up as a quotable quote and have committed it to eternity here)

 

[Deleted member 65]

"If you have to read the directions you don't know what you're doing." -RayDunzl

(I've been there, its just that I suddenly thought that up as a quotable quote and have committed it to eternity here)

So the tutorial is garbage?

 

[RayDunzl]

So the tutorial is garbage?

I don't know.

Try again.

Here's a longer version: https://community.roonlabs.com/t/a-guide-how-to-do-room-correction-and-use-it-in-roon/23800

---

Oh, duh.

That's the same one you referenced.

(imagine me looking embarassed)

 

[Deleted member 65]

I don't know.

Try again.

Of course I will, either something breaks or I'll eventually succeed. As a temp step I manually created a PEQ in Roon based on my REW measurements below, microstep forward ...

 

[amirm]

Did the PEQ make it sound better? The great thing about that approach is that you can turn the individual filters on and off and listen for effect.

 

[DonH56]

What exactly was distorted about the sound?

Was the mic moved at any time during the process?

 

[gingerbeer]

https://www.bhphotovideo.com/bnh/controller/home?A=details&O=&Q=&ap=y&c3api=1876,{creative},{keyword}&gclid=Cj0KCQjwn6DMBRC0ARIsAHZtCePATW5ZQ883H-iMA5E5hFnI2JwXnT-oul4bmfIGchQLrNojJ9s8M2IaAq4hEALw_wcB&is=REG&m=Y&sku=576064

Yup but, if one really wants to use a tripod, there are adapters.

Duct tape works a treat

 

[Biblob]

Will part three be coming soon? I have been reading these with pleasure!

 

[amirm]

Thanks. I have such a deep backlog of review equipment that won't let me write that for at least a couple of months. But keep reminding me. That is a good way to keep me motivated to write it.

 

[Krunok]

Oh man, I'm busted again...

Mine's on a short heavy HAM desk stand, on the top of the couch, with velcro markers on the couch and a velcro 'limiter", as it leans forward (to be at ear position).

View attachment 5837

It lets me remove and replace it with really good positional repeatability, with that last horizontal quarter-inch found via the pink noise response at 20khz.

Nice. Where is the microphone pointed at?

 

[RayDunzl]

The Phantom Center mid-height on the MartinLogan panels.

 

[Krunok]

The Phantom Center mid-height on the MartinLogan panels.

I see, thank you.

Which software from this list would you recommend using instead of AcourateDRC, as miniDSP 2x4HD cannot use it?

https://www.minidsp.com/applications/advanced-tools/fir-filter-tools

 

[RayDunzl]

Which software from this list would you recommend using

I've used rePhase with my OpenDRC-DI. I'm generally cheap, and it's free and powerful, but very manual. That unit has 6144 taps for each channel at 48kHz.

The 2x4HD doesn't have many taps available for FIR filters, maybe a pool of 4096 that can be allocated as you see fit across the 4 channels at 96kHz internal rate, so there's a lack of precision/capability with FIR as the target frequency decreases.

I've only used the PEQ (IIR) and Crossover and Delay settings with my 2x4HD so far, as I'm using it for subs only.

I tried generating FIR filters with the limited taps in rePhase, but didn't like what it said the result would be, and haven't playied with that since.

(I'm no expert here, so I might be missing something or just be wrong)

 

[Krunok]

I've used rePhase with my OpenDRC-DI. I'm generally cheap, and it's free and powerful, but very manual. That unit has 6144 taps for each channel at 48kHz.

The 2x4HD doesn't have many taps available for FIR filters, maybe a pool of 4096 that can be allocated as you see fit across the 4 channels at 96kHz internal rate, so there's a lack of precision/capability with FIR as the target frequency decreases.

I've only used the PEQ (IIR) and Crossover and Delay settings with my 2x4HD so far, as I'm using it for subs only.

I tried generating FIR filters with the limited taps in rePhase, but didn't like what it said the result would be, and haven't playied with that since.

(I'm no expert here, so I might be missing something or just be wrong)

Yes, 2x4HD has 4096 taps. What do you mean when you said you didn't like what it said the result would be? You couldn't get the curve right playing with those EQ sliders?