I'm confused because I see microphones placed one meter away, and others only 20cm from the speaker.
And while we're at it, any advice on what to take to measure with quality.
the latest generation sound card, which should also be purchased, but I already have clearer ideas, will have the best features.
I just installed REW
And while we're at it, any advice on what to take to measure with quality.
the latest generation sound card, which should also be purchased, but I already have clearer ideas, will have the best features.
I just installed REW
ChatGPT (with some help):
You don't want the MiniDSP for loudspeaker design work though.
I did ask the AI what is best when accurate timing is important. Impressive how we evolved ever since Google came around. It went wrong on the SoundID mike though, that one is very analog and very well suited:
Great follow-up — accurate timing is crucial if you’re doing:
When timing accuracy is critical, the entire signal chain matters — not just the microphone, but also the interface, ADC, and whether you’re using USB vs. XLR.
If your interface supports loopback (or has dual inputs), you can:
You don't want the MiniDSP for loudspeaker design work though.
I did ask the AI what is best when accurate timing is important. Impressive how we evolved ever since Google came around. It went wrong on the SoundID mike though, that one is very analog and very well suited:
Great follow-up — accurate timing is crucial if you’re doing:
- Impulse response measurements
- Time alignment of speakers or subwoofers
- Minimum phase/phase coherence analysis
- FIR filter design
- Precision crossover tuning
When timing accuracy is critical, the entire signal chain matters — not just the microphone, but also the interface, ADC, and whether you’re using USB vs. XLR.
🧠 What affects timing accuracy?
- Mic itself: Most measurement mics are passive and don’t affect timing much. What matters more is:
- Audio interface clock stability
- USB vs. analog mic
- Driver latency & sample synchronization
- Calibration file delay compensation (important!)
✅ Best Options for Accurate Timing:
🥇
XLR Mic + Audio Interface
(recommended setup)
- Use mics like:
- Dayton EMM-6
- iSEMcon EMX-7150
- Audix TM1
- Why: These rely on the audio interface for A/D conversion, which ensures consistent sample timing (especially with loopback or dual-input measurements).
⚠️ USB Microphones (like UMIK-1 or SoundID)
- USB mics introduce an independent clock from your audio interface.
- Makes loopback timing or multi-device sync difficult.
- Some software (like REW) compensates for this to a degree, but not ideal for high-accuracy timing.
🔁 Loopback Timing Setup
If your interface supports loopback (or has dual inputs), you can:
- Feed the signal output directly back into the input (or loop through a speaker + mic path).
- REW/ARTA/etc. can then calculate exact delay and correct for interface latency.
🔍 Calibration Delay Compensation
- Some mic calibration files (especially for USB mics) include a delay offset, usually in milliseconds.
- Make sure your measurement software applies this delay compensation, or your impulse response will be off.
🔧 Suggested Setup for Timing-Accuracy
| Component | Recommended |
|---|---|
| Mic | EMM-6 / EMX-7150 / Audix TM1 |
| Interface | Focusrite Scarlett, MOTU M-series, RME Babyface, etc. |
| Software | REW, ARTA, Smaart, REAPER (with JS plugins) |
| Timing Method | Loopback input, or dual-channel impulse response |
TL;DR
Microphone spacing is very important because of (1) the baffle step and (2) avoidance of reflections.
Re: the baffle step. This is a volume loss of about 6dB which occurs over four octaves. Its centre frequency (f3) can be roughly calculated with 115824/W (W = baffle width in millimetres) or 4560/W (baffle width in inches). If your driver is in the operating range of the baffle step, you need to space your mic about 2 baffle widths away (about 1m) to account for it.
Re: reflections. The further away the mic is spaced from the speaker, the greater the likelihood of early reflections contaminating the measurement. At some point, wavelengths get so long that reflections arrive at the mic before the speaker has finished producing the sound, so there is always a lower limit where meaningful reflection-free measurements can be taken. If you want to lower the frequency limit, the mic should be as close to the speaker as possible, the speaker should be taken outdoors and elevated, etc.
As you can see, these two are in conflict with each other. Even if you take every precaution you can, at some point wavelengths get reallllly very long and meaningful reflection-free measurements become impossible. So you need more specialised techniques like ground plane measurements, suspension from cranes or gantries, half space measurements, etc.
I don't know if anybody has developed this technique before me, but what I do is to take a nearfield measurement of the driver (mic centred on axis, about 10cm away). I take a measurement, then use a baffle step calculator like this one. I generate two curves for 2 microphone distances - one for 10cm, and the other for main listening position (for me, about 3m). First, invert the 10cm baffle step sim and convolve it with your windowed measurement to get a 0cm response. Then convolve that response with the non-inverted 3m baffle step sim to obtain the actual driver response in the baffle.
Re: best microphone. XLR if you can afford it. It needs to be calibrated.
Your AT microphone is 100% useless for measuring, it is for DJ anouncements and vocals maybe.
You need a phantom powered XLR input for REW and dedicated measuring mike. Don't waste money on a USB type.
With such gear, in the EU, you may buy at Thomann. In most cases it will be (USB interface and microphone) cheaper to buy new than used, because of P&P, even if you ignore the 3 years guarantee you get there.
If you go for a non calibrated microphone, you must be prepared to have no correct data in the low and high end. The midrange usualy is linear. To know that your measurements are correct is more value than the 50€ premium you pay, compared to the cheapest Behringer mike with very inconsistant tollerances.
If we look at Thomann, you get a calibrated Sonarworks for 77€, which is a very fair price and will serve you well for many years.
https://www.thomann.de/it/sonarworks_soundid_ref_measurement_micro.htm
Throw in a ESI Maya 22 USB 2-channel USB interface for 39€ and you are ready to go.
https://www.thomann.de/it/esi_maya_22_usb.htm
This is nice combination, compact and solid.
If your budget is a little higher, a Focusrite Scarlett 2i2 3rd Gen for 116€ is a safe bet and has no weak points. May be considered a little more audiophile by some.
It may be interesting to know, if you spend these 114€, which includes P&P and a return option, you get something you can resell with very little loss if you don't like the hobby any more. Have a look what eBay offers you find and you will see they are rare and expensive in used condition.
You need a phantom powered XLR input for REW and dedicated measuring mike. Don't waste money on a USB type.
With such gear, in the EU, you may buy at Thomann. In most cases it will be (USB interface and microphone) cheaper to buy new than used, because of P&P, even if you ignore the 3 years guarantee you get there.
If you go for a non calibrated microphone, you must be prepared to have no correct data in the low and high end. The midrange usualy is linear. To know that your measurements are correct is more value than the 50€ premium you pay, compared to the cheapest Behringer mike with very inconsistant tollerances.
If we look at Thomann, you get a calibrated Sonarworks for 77€, which is a very fair price and will serve you well for many years.
https://www.thomann.de/it/sonarworks_soundid_ref_measurement_micro.htm
Throw in a ESI Maya 22 USB 2-channel USB interface for 39€ and you are ready to go.
https://www.thomann.de/it/esi_maya_22_usb.htm
This is nice combination, compact and solid.
If your budget is a little higher, a Focusrite Scarlett 2i2 3rd Gen for 116€ is a safe bet and has no weak points. May be considered a little more audiophile by some.
It may be interesting to know, if you spend these 114€, which includes P&P and a return option, you get something you can resell with very little loss if you don't like the hobby any more. Have a look what eBay offers you find and you will see they are rare and expensive in used condition.
These cheaper mics may come with a cal file, allowing accurate measurements. But in my experience they drift quite a bit, making the cal file moot after a couple of months.ChatGPT (with some help):
If you are interested in long-term stability, I would recommend something a bit higher quality than these.
I was just thinking about it last night, about what to get between a sound card and a microphone.
@markbakk
without going on excessive expenses, max 200 for usb audio and max 100 for the calibrated microphone.
@Turbowatch2
Just last night I took a good hard look at that Sonarworks microphone
@mbrennwa thankU
@markbakk
without going on excessive expenses, max 200 for usb audio and max 100 for the calibrated microphone.
@Turbowatch2
Just last night I took a good hard look at that Sonarworks microphone
@mbrennwa thankU
I think the above posts give your clues. And although mbrennwa shares one consideration, think of this: even buying a new Sonarworks every now and then is cheaper than a professional Gras or B&K. Alternatively you could get a cheap reference by getting it measured every once in a while.
I don’t share his experience by the way. My cheap mikes seem to be quite steady. But let others chime in on this.
I don’t share his experience by the way. My cheap mikes seem to be quite steady. But let others chime in on this.
Jeff, even if you're not using Vituixcad, I found this instruction document really useful. It recommends two measurement sets when using REW; far field at around 1m and nearfield, almost touching the driver. It also recommends using a turntable for off axis measurements, but I didn't as I'm probably not as serious as I should be about the hobby... 😳
There are options between very cheap and very expensive. EMX and Earthworks come to mind. There may be others.
If a cheap (and stable!) reference for frequency response calibration would exist, we wouldn't be here and discuss the issue.
Why would those be more stable? I’m curious about the experience of the lot here on this.
It is not a choice not to use VituixCAD, it is a convenience to avoid using Win and stay in Ubuntu. 🙂
I'd argue the other way. Any old USB audio dongle will be good enough for loudspeaker testing as long as it's 44 kHz/16bit/stereo (or better). You might be able to find one for EUR 20 or so. Or use the built-in sound interface of your computer, if it has one.
Spend as much as you can on the mic.
That's my experience. Back when I was doing acoustic measurements on a more routine basis, I sometimes pulled out all my mics and compared them. The EMX and Earthworks were always consistent, while the Behringer and Beyerdynamic drifted away from these.
It is not a choice not to use VituixCAD, it is a convenience to avoid using Win and stay in Ubuntu. 🙂
BTW I don't use VituixCAD even though I do use Windows. I only use REW and XSim. But I do take a lot of shortcuts and don't pretend I'm good at speaker building! My main point was that I think the tutorial is useful as a general guide.
we put the internal sound card aside, so I take the opportunity to record some strums with my Fender '89 stratocaster.
I opted for the Scarlett 2i2 3 third generation that will arrive in the next few days.
the doubt remains on the microphone, let me explain:
this > Sonarworks SoundID reference - requires a license?
if there is another microphone that you use and it is well made, tell me...
Not sure what you mean by "another", but, as I wrote before, the EMX/Isemcon and Earthworks microphone worked well for me.