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!