Acoustic room optimization

[BenWatts]

Hi everyone,

I feel particularly silly for not understanding, but I’m exhausted from not getting it and I’m reaching my limit here.

I’m diving into acoustic measurement for my room, but I’m running into some technical misunderstandings despite having the supposed relevant equipment. Here’s my current setup:

- iMac with a 2.1 Focal system
- REW
- Zoom H5 (used as a USB audio interface, powered by the Mac)
- 5m XLR cable (connecting the iMac to the central listening point)
- ECM8000 microphone

My issues:

1. Calibration
I’ve selected the Zoom H5 as the audio input in my iMac’s preferences and set it to audio interface mode. However, when calibrating at -18 dBFS in REW, I can’t reach the required sound level. How do I adjust the gain on the H5 or in REW to get a usable signal?

2. ASIO Driver
In REW, the list of audio drivers doesn’t offer ASIO. Is this a problem? How do you handle this?

3. The Measurement Principle Itself (yes, I’m embarrassed to ask these questions).
I don’t understand why the calibration sound needs to come from the iMac’s speakers (located in a corner of my living room) when I want to measure my main hi-fi system (listening point in the center of the room). I don’t get the principle at all. In my mind, it was about sending a test signal (e.g., a specific frequency from Qobuz) through my system to measure the response.

My goal is to optimize the acoustics of my room for a system that feels too intrusive and oppressive to me. After watching YouTube videos, I still don’t understand the procedure.

Thanks in advance for your help.

 

[abacus]

You would be better off getting rid of the mic and replacing it with a UMK-1 (More expensive but the go to for calibration) and then from within your calibration program loading the supplied mic calibration data.

When making measurements you need to remove any external sounds (No idea where you got the idea that your iMac speakers need to be on) so as not to interfere with the measurements.

Room correction is the final icing on the cake, it is not a substitute to acoustically treating your room and finding the best position for your speakers in the room.

Print out the REW instructions on calibration (Or have them on your phone or tablet) and keep them in your hand and follow them step by step.

Bill

 

[BenWatts]

Thé ECM8000 is fair enough for general measures. 22€ vs 99€ for a 10 min usage? No debate on that.

Speaker positionning have been already worked. Now, I want to measure the balance in the room to assess furniture, curtains…

 

[abacus]

Thé ECM8000 is fair enough for general measures. 22€ vs 99€ for a 10 min usage? No debate on that.

Speaker positionning have been already worked. Now, I want to measure the balance in the room to assess furniture, curtains…

You cant do room tests or calibration on the cheap (You need to have a calibrated mike for a reason), plus when you have finished, you can sell on the UMK-1 for a decent the price as it is highly regarded.

Bill

 

[BenWatts]

Not my approach. An ECM8000 is enough.
Dealing with calibration, yes I did. I am just not happy with the settings and my questions are focused on the very first steps of the process I dont understand

 

[abacus]

Not my approach. An ECM8000 is enough.
Dealing with calibration, yes I did. I am just not happy with the settings and my questions are focused on the very first steps of the process I dont understand

As I said in my 1st post: Print out the REW instructions on setup and use (Or have them on your phone or tablet), and keep them in your hand, then follow them step by step.
If you still cannot get it, then get a professional (Or see if you have a friend locally that can help) in to help or do it for you.

Bill

 

[BenWatts]

No need to reply if you don’t know. It’s okay.
Maybe my questions are not clear. Don’t feel bound to reply

 

[abacus]

As you don't seem to be interested in fixing your problem unless it is done your way, then by all means ignore my advice, (Which is just a basic guide for those who have little experience) and continue as you are.

This video and the link it provides may be more up your street , as it is more DIY then pro , which a lot of other videos use to explain and can be difficult to understand.

 

[BenWatts]

I understand you feel driven by a mission to guide others toward your vision, but unfortunately, that’s not what this is about.

My original question was simply to understand the basic principle, and of course, I’ve already carefully reviewed all the tutorials. However, I’ve expressed that I still don’t understand and I feel stupid not understanding.

You don’t have to respond. It seems you didn’t grasp my initial issue. I don’t hold it against anyone for not answering—it’s not your responsibility. Stay at peace.

Measures have been done and analysis is under scrutiny. Bass trap seems to be the solution.

The initial issue was to modify input and output from my iMac and to select R and then L speakers. I could not fix it previously.
Now it works. MMM measures are not necessary at my poor level. Just find a way to manage 60hz reverb.

 

[RoA]

Never used REW but I understand that it can be complex and that it involves a learning curve.

As to why your test signals do not come from your main speakers ... ?

My WiiM has a simple room optimizing app which works just fine (measured from listening position and through main speakers, obviously). I have a significant room bass mode which it deals with it relatively successfully as does Roon's DSP using WiiM measurements.

This leaves vinyl and CD. Unfortunately I can't compensate there and bass traps are out of question (it's a living room).

Have to add that I use room EQ very (!) sparingly and only to compensate for the one main mode under 100hz. I leave anything above that untouched as it seems detrimential to overall SQ.

Room problems can be a right a***. I hope you can sort yours out.

 

[BenWatts]

Thank you RoA for your reply.
I am definitely not the brilliant guy I would have expect to be.

What I learnt from this experience in addition to my hurry:
- Plug the Zoom H5 and select: audio board, than phantom 48V supply from the device.
- Apple: my preferences / sound : input -> H5 & output -> my/your streamer (in airplay or usb... whatever)
All the rest is quite well explained in tutorials except the selection of R or L speakers.
I finale got my results after 3 days of total misunderstanding.

Here are the screenshots and the analysis of Mistral AI : https://mistral.ai











Here is just a synthesis. The full analysis is quite long.

Key Findings:​

1. RT60 (Reverberation Time)​

• Left Speaker:
  
  • Highly variable RT60 in low frequencies (20-200 Hz), with peaks at 60 Hz (~700 ms) and 100 Hz (~500 ms).
  • Stable RT60 (~400-500 ms) in mid frequencies (200 Hz–2 kHz).
  • Gradual decrease in high frequencies (>2 kHz).
• Right Speaker:
  
  • Extreme peak at 40 Hz (~900 ms) and a sharp drop at 60 Hz (~300 ms).
  • Shorter RT60 (~300-400 ms) in mid frequencies compared to the left speaker.

Issue: Both speakers suffer from modal resonances in low frequencies, but the right speaker is more affected, especially at 40 Hz.

---

2. SPL & Phase Response​

• Left Speaker:
  
  • Generally flat SPL from 100 Hz to 10 kHz.
  • Peaks at 50 Hz (+5 dB) and 200 Hz (+3 dB); dip at 80 Hz (-3 dB).
  • Unstable phase in low frequencies (20-200 Hz).
• Right Speaker:
  
  • Similar SPL trend but with more pronounced peaks at 40 Hz (+6 dB) and 150 Hz (+4 dB).
  • Dip at 70 Hz (-4 dB).
  • Phase instability in low frequencies, more pronounced than the left speaker.

Issue: Both speakers show SPL imbalances and phase instability in low frequencies, with the right speaker exhibiting more extreme variations.

---

Recommendations:​

1. Acoustic Treatments​

• Bass Traps: Place bass traps in room corners and along walls to mitigate modal resonances.
• Absorption Panels: Add absorption panels on side and rear walls to reduce early reflections and balance RT60.
• Diffusers: Use diffusers on the ceiling and rear wall to improve sound diffusion.

2. Speaker Placement (already done)​

• Distance from Walls: Move speakers away from walls to reduce resonances and early reflections.
• Symmetry: Ensure symmetrical placement of left and right speakers to minimize imbalances.

3. Digital Corrections (I won't. My devices do not have this function).​

• EQ Adjustments: Use REW measurements to apply targeted EQ corrections (e.g., parametric EQ) to smooth out SPL peaks and dips.
• Phase Correction: If possible, use audio processors to address phase instability in low frequencies.

​

Issue​	Solution​
Resonances at 40 Hz & 60 Hz	Bass traps + EQ corrections
SPL imbalance (L vs. R)	Digital correction + symmetrical speaker placement
Long RT60 in mid frequencies	Absorption panels on side walls
Phase instability in lows	Digital correction + acoustic treatment

Final Thoughts:​

The measurements reveal typical room acoustic issues, particularly in low frequencies. The proposed solutions (bass trap) should significantly improve sound quality.

Final Thoughts:​

The measurements reveal typical room acoustic issues, particularly in low frequencies. The proposed solutions (acoustic treatments, speaker placement, digital corrections) should improve sound quality.

If you’ve faced similar issues or have additional tips, feel free to share!

 

[landco]

This video and the link it provides may be more up your street , as it is more DIY then pro , which a lot of other videos use to explain and can be difficult to understand.

In the video, this dude only talks—he doesn't provide any practical examples.

Beware of such people.

 

[RoA]

Thank you RoA for your reply.
I am definitely not the brilliant guy I would have expect to be.

What I learnt from this experience in addition to my hurry:
- Plug the Zoom H5 and select: audio board, than phantom 48V supply from the device.
- Apple: my preferences / sound : input -> H5 & output -> my/your streamer (in airplay or usb... whatever)
All the rest is quite well explained in tutorials except the selection of R or L speakers.
I finale got my results after 3 days of total misunderstanding.

Here are the screenshots and the analysis of Mistral AI : https://mistral.ai











Here is just a synthesis. The full analysis is quite long.

Key Findings:​

1. RT60 (Reverberation Time)​

• Left Speaker:
  • Highly variable RT60 in low frequencies (20-200 Hz), with peaks at 60 Hz (~700 ms) and 100 Hz (~500 ms).
  • Stable RT60 (~400-500 ms) in mid frequencies (200 Hz–2 kHz).
  • Gradual decrease in high frequencies (>2 kHz).
• Right Speaker:
  • Extreme peak at 40 Hz (~900 ms) and a sharp drop at 60 Hz (~300 ms).
  • Shorter RT60 (~300-400 ms) in mid frequencies compared to the left speaker.

Issue: Both speakers suffer from modal resonances in low frequencies, but the right speaker is more affected, especially at 40 Hz.

---

2. SPL & Phase Response​

• Left Speaker:
  • Generally flat SPL from 100 Hz to 10 kHz.
  • Peaks at 50 Hz (+5 dB) and 200 Hz (+3 dB); dip at 80 Hz (-3 dB).
  • Unstable phase in low frequencies (20-200 Hz).
• Right Speaker:
  • Similar SPL trend but with more pronounced peaks at 40 Hz (+6 dB) and 150 Hz (+4 dB).
  • Dip at 70 Hz (-4 dB).
  • Phase instability in low frequencies, more pronounced than the left speaker.

Issue: Both speakers show SPL imbalances and phase instability in low frequencies, with the right speaker exhibiting more extreme variations.

---

Recommendations:​

1. Acoustic Treatments​

• Bass Traps: Place bass traps in room corners and along walls to mitigate modal resonances.
• Absorption Panels: Add absorption panels on side and rear walls to reduce early reflections and balance RT60.
• Diffusers: Use diffusers on the ceiling and rear wall to improve sound diffusion.

2. Speaker Placement (already done)​

• Distance from Walls: Move speakers away from walls to reduce resonances and early reflections.
• Symmetry: Ensure symmetrical placement of left and right speakers to minimize imbalances.

3. Digital Corrections (I won't. My devices do not have this function).​

• EQ Adjustments: Use REW measurements to apply targeted EQ corrections (e.g., parametric EQ) to smooth out SPL peaks and dips.
• Phase Correction: If possible, use audio processors to address phase instability in low frequencies.

​

Issue​	Solution​
Resonances at 40 Hz & 60 Hz	Bass traps + EQ corrections
SPL imbalance (L vs. R)	Digital correction + symmetrical speaker placement
Long RT60 in mid frequencies	Absorption panels on side walls
Phase instability in lows	Digital correction + acoustic treatment

Final Thoughts:​

The measurements reveal typical room acoustic issues, particularly in low frequencies. The proposed solutions (bass trap) should significantly improve sound quality.

Final Thoughts:​

The measurements reveal typical room acoustic issues, particularly in low frequencies. The proposed solutions (acoustic treatments, speaker placement, digital corrections) should improve sound quality.

If you’ve faced similar issues or have additional tips, feel free to share!

It will be interesting to hear how exactly you will tackle this. Perhaps you could also do this with some supporting photos?

 

[abacus]

In the video, this dude only talks—he doesn't provide any practical examples.

Beware of such people.

If you click on the link he mentioned Linik all the details are there (Although you do have to sign in)

Bill

 

[Geoff P.]

Sorry Ben -I have no solutions to your problem, aside from - if the room is such a problem, ditch it and use a set of headphones.
Your situation has, however, prompted me to consider how on earth we got into a state where it's so problematic to simply listen to music. Some folks seem more keen to listen to their equipment.
As others have said - feel free to ignore my comments. I'm old school so I have an excuse. I hope you find what you are looking for.

 

[landco]

If you click on the link he mentioned Linik all the details are there (Although you do have to sign in)

Bill

The link is the same chatter. This dude does not give practical recommendations, only general phrases.

 

[nopiano]

I’ve never used REW though a friend has and he definitely talks about a long learning curve - and he’s very clever!

I’ve only used manufacturer proprietary systems - specifically Linn’s Sound Optimisation, which uses physical measurements only, and Wiim’s system that can work with an iPhone microphone held at ear level.

There is a very thorough tutorial on REW at ASR which looks worth reading. On general points, I’ve found that reducing the extreme adjustments a system might implement is easier on the ear. And it’s best to concentrate on the cuts you need rather than boosting any suck outs - as these are generally less audible and can cause unwanted overload issues. Up to 200Hz is worth measuring - above that you can balance by ear/preference.

Also, I’d not rush to buying bass traps and suchlike unless you’ve exhausted speaker positioning. That itself can be time consuming but well worth it. Try to find the Sumiko Master setup process and see how far you can follow it. It’s the best I’ve found.

Bon chance!

 

[abacus]

The link is the same chatter. This dude does not give practical recommendations, only general phrases.

That's why I selected it, as the OP was having problems fully understanding the in-depth videos.

Bill

 

[BenWatts]

Thanks Nopiano. You are too kind with me.
I am not very patient with myself and cannot understand why I do not understand fast as I would like to. Anyway. Things are getting clear and I propose some support if anyone here is about to step into measures.

One thing that is really amazing is the differences of the waterfall. The left speaker will be discussed. I moved the former speaker from behind and let the speaker breathe on the four sides.

Here are the results.

1. Measurement Context​

• First measurement: on Sept. 5th, 2025.
• Second measurement: on Sept. 7th, 2025).
• iMac + H5 Zoom + ECM8000

---

​

2. Common Parameters​

• Time window: 500 ms.
• Temporal resolution: 3.04 ms per slice.
• Frequency resolution: 1.7 Hz.
• Response time: 301 ms.

---

​

3. Visual and Comparative Analysis​

a. Low-Frequency Response (20 Hz – 200 Hz)​

• First measurement (Sep 5):
  • Strong resonances around 40 Hz, 60 Hz, and 80 Hz, with significant lingering (persistent red/orange colors).
  • These resonances indicate issues with the impulse response (reverberation or uncontrolled room modes).
• Second measurement (Sep 7):
  • Resonances around 40 Hz and 60 Hz appear attenuated (less red/orange lingering).
  • The response is "cleaner" and decays faster, suggesting an improvement (acoustic treatment, filter adjustments, etc.).

b. Mid and High-Frequency Response (200 Hz – 10 kHz)​

• First measurement:
  • Generally stable response, but with amplitude peaks around 1 kHz and 3 kHz.
  • Moderate lingering present.
• Second measurement:
  • Amplitude peaks are less pronounced, and lingering is reduced.
  • The response appears more linear and uniform, which is ideal for accurate sound reproduction.

c. Temporal Behavior (Resonance Duration)​

• First measurement:
  • Resonances (especially in the lows) persist longer (up to 300 ms).
  • This may indicate a poorly damped room or incorrect subwoofer/speaker settings.
• Second measurement:
  • Resonances decay faster (less lingering after 200 ms).
  • Better control of the impulse response.

---

​

4. Color Interpretation​

• Red/Orange: High sound pressure levels (strong resonances).
• Green/Yellow: Moderate levels.
• Blue: Low levels (attenuation). The reduction of red/orange areas in the second measurement is a sign of improvement.

---

​

Conclusion: Reduced resonances in the low frequencies.​

• Better linearity in mid and high frequencies.
• Faster decay of lingering effects.

Super positive impact : just removing speakers!​

Only one removal, no investment and these changes are so important I am now considering acoustic treatment as a major impact on my listening sessions.

One important point on curves is that you can find peaks on charts with the precise distance.
I noticed a peak at 10ms => 0,001s
0,001s x 340 (speed of sound) => 3,40m far away from left speaker. The wall in the back between the living and the open kitchen.


Last but not least:



We can observe a drop of the RT60 within 77hz (bass)
RT60 is the time it takes for sound to decay by 60 decibels in a given space after the sound source has stopped => too much reverb in bass frequencies.
Curves are not regular. Not satisfying and current when rooms are not balanced.
Bass freq are the main issue in my room such you can have observed in previous charts.


As a conclusion:

• Low-frequency resonance: A high RT60 in the low frequencies may require acoustic treatment (such as bass traps).
• SPL response: Irregularities in the low and mid frequencies can be corrected using an equalizer or by repositioning the speaker.
• High-frequency absorption: If the highs seem overly attenuated, check the environment (carpets, curtains, etc.) or the audio system settings.

 

[BenWatts]

For neophyte as me :

Beware of your settings. I have wasted too much time in stupid settings.


Personal device a Zoom H5 (as a guitar player and singer, I recorded a lot in the past with my GF).



Preferences => input & output




Select carefully the speaker you want to measure.

At your disposal for any question.

 

[DougK1]

I p*ssed around with Dirac some years ago. Gave up after a few days. I just want to listen to music, not faff around with a ruddy PC.