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For room measurements, does setting higher sampling rate than 48khz make sense?


dericchan1

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Hi everyone, not sure if this is the right place for my question.

 

After reading the thread by the Computer audiophile here and his comment about the importance of a good quality recording mic VS a usb mic, I decided to invest in a sonarworks soundid condenser mic and an Artpro mic preamp.

 

Both the Sonarworks mic and the mic preamp supports up to 24/192 and I wonder if there is indeed any advantage to record my room measurement using higher sampling rate than 24/48 for use with audiolense convolution filters?

 

Nowadays, qobuz has more and more albums that are 24/96 so I wonder if it makes sense or perhaps there are technical reasons that measuring the room at 24/96 or higher would be better than sticking with 24/48?

 

Thanks


Deric

 

 

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7 minutes ago, dericchan1 said:

Hi everyone, not sure if this is the right place for my question.

 

After reading the thread by the Computer audiophile here and his comment about the importance of a good quality recording mic VS a usb mic, I decided to invest in a sonarworks soundid condenser mic and an Artpro mic preamp.

 

Both the Sonarworks mic and the mic preamp supports up to 24/192 and I wonder if there is indeed any advantage to record my room measurement using higher sampling rate than 24/48 for use with audiolense convolution filters?

 

Nowadays, qobuz has more and more albums that are 24/96 so I wonder if it makes sense or perhaps there are technical reasons that measuring the room at 24/96 or higher would be better than sticking with 24/48?

 

Thanks


Deric

 

 

 

Hi Deric, I remember looking into this last year and deciding that it didn't make much sense for measure at higher than 48 kHz. One likely reason is that the microphone used is likely not going to capture much audio higher than 24 kHz (the limit of a 48 kHz signal). 

 

Perhaps @mitchco from Accurate Sound can chime in. 

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5 minutes ago, The Computer Audiophile said:

By the way, I just checked at I have that same microphone. It's specifications are:

 

  • Frequency response: 20 Hz - 20kHz with supplied calibration profile

 

Also, smart move to step up your game with a good mic and preamp. It really matters. 

Thanks Chris, yes, that was a great advice as I will be doing more measurements for both my main system and my bedroom as well, I figure the investment will be worth it. 

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13 minutes ago, mitchco said:

Hi Deric,

 

Frequency resolution = fs / N where fs is the sample rate and N is the number of filter taps.

 

So a 65,536 tap FIR filter at 48 kHz has a frequency resolution of 48000/65536 = 0.732 Hz. 

 

The frequency range spans 0Hz to 24 kHz (i.e. fs/2). So thinking of a FIR filter as a graphic equalizer: 24000/0.732 = 32,768 sliders for our FIR equalizer. Remember 1/3 octave (i.e. 31 band) eq's? Our FIR example has 1000 times the frequency resolution of a 1/3 octave equalizer.

 

A rough rule of thumb is that the effective low frequency limit of the filter is to multiply the frequency resolution by 3, which is 3 x 0.732 Hz = 2.2 Hz.

 

There is not much to gain (if anything) by using a 131,072 tap filter as the 65,536 tap filter is well beyond our ears frequency resolution and low frequency limit.

 

One can certainly try lower/higher tap counts, but 65K seems to be the sweet spot for DRC. You could try generating the same filter at different filter tap lengths and import the correction filters in REW and look at the frequency responses. You could also load them up in HLC for example and compare level matched filters of various tap lengths to see if you can hear a difference...

Thanks Mitch for the insight. much appreciated!!!

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13 minutes ago, El Guapo said:

I have an Earthwork M50 measurement mic and a Merging interface so I have three strategies for different scenarios:

1. 48KHz for friends’ home theater / immersive systems. 65k taps is the default length but will see the delay to adjust the length to 32k or less. It’s the most suitable setup.

2. 96KHz for friends’ hi-end stereo systems. This setup has less aliasing issue in high frequency range. Also will use 131k taps for the final FIR wav (131k taps at 96KHz the resolution is equal to 65k taps at 48KHz).

3. 352.8KHz / 1 million taps for my immersive system. 😊

I’ve been using HLC to upsample my filters with the increasing sample rate. 

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34 minutes ago, El Guapo said:

I have an Earthwork M50 measurement mic and a Merging interface so I have three strategies for different scenarios:

1. 48KHz for friends’ home theater / immersive systems. 65k taps is the default length but will see the delay to adjust the length to 32k or less. It’s the most suitable setup.

2. 96KHz for friends’ hi-end stereo systems. This setup has less aliasing issue in high frequency range. Also will use 131k taps for the final FIR wav (131k taps at 96KHz the resolution is equal to 65k taps at 48KHz).

3. 352.8KHz / 1 million taps for my immersive system. 😊

 

35 minutes ago, El Guapo said:

I have an Earthwork M50 measurement mic and a Merging interface so I have three strategies for different scenarios:

1. 48KHz for friends’ home theater / immersive systems. 65k taps is the default length but will see the delay to adjust the length to 32k or less. It’s the most suitable setup.

2. 96KHz for friends’ hi-end stereo systems. This setup has less aliasing issue in high frequency range. Also will use 131k taps for the final FIR wav (131k taps at 96KHz the resolution is equal to 65k taps at 48KHz).

3. 352.8KHz / 1 million taps for my immersive system. 😊

Question - how does reducing tap count from 65k to 32k improve on delays? Do you mean group delay or like pc playback delay?

 

thanks

 

deric 

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5 minutes ago, dericchan1 said:

Update:

Invested in an Artpro USB ii mic preamp and a Sonarwork soundid xlr condenser mic.
Tested in the bedroom system with my focal Aria bookshelves.

I am definitely seeing much improved stability (only using 1 device for playback and recording hence no clock drift issue). Once I have the mic in the listener position, absolutely no interference unlike the umik. I took 20 measurements in various time length, 0 Ms in time delays in every single measurement. When I used the umik, I normally get maybe 2 or 3 times out of 20 trial measurements showing no time delays 

While overall the measurement curve looks alike between the sonarworks mic and the umik, there are certainly some differences in the high frequencies starting at around 7khz and to 20khz. The measurement curve in the noted high frequency with the sonarworks mic looks closer to Amir at ASR estimated in room measurement for my speakers - could just be placebo but it does seem like the soundstage depth has improved…

Cheers

Deric

That’s great to read. 

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Here's a question for anyone who owns the Sonarworks mic. The microphone comes with three different calibration files as most of you know. 

 

I was just thinking tonight, I've always used 0°.... And pointed the microphone completely straight, and leveled at the listening position. So basically aimed in between the two speakers. 

 

Wouldn't it make more sense to use the 30° calibration file. My speakers are roughly 25° off to the left and right.... Although it may not make a lot of difference, wouldn't that be better to use?

 

I also use Audiolense for my corrections.

 

Thanks

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32 minutes ago, cjf said:

Just to muddy the waters a bit, I did all my room correction measurements/filters/files..etc at 24/192 because that was the highest the Lynx Hilo AD could muster. But thinking back on it all, unless I had a M50 Mic like @El Guapo has, or better, there probably wasn't a reason to go anywhere near that high. But I think my reasoning for doing so at the time was based on the Up/Down target Sample Rate I was hard coding on the DAC side. 

 

I guess the ideal MIC and Measurement range would be chosen after first considering what Freq range all of your speakers are capable of reproducing cleanly. I wouldn't want to have a Mic or AD that wasn't at least capable of capturing that whole range all your speakers are expected to be playing at. Freq and SPL ranges that is. Some Mic's peter out at higher SPL ranges to add to the fun.

I'll get the chance to do mine all over again in a few years in a new space but for now I'm just running with my original choice for better or worse.

My main system speakers fr from 35hz to 100khz. 

IMG_8234.jpeg

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If your microphone and/or its calibration are good to "only" 20kHz, then performing the measurements at 48kHz makes sense. Ideally, in that case, the filter design software limits the correction to 20kHz but produces filters that pass ultrasonic content untouched (with only appropriate delay and level adjustment). So, when listening to music from higher sample rate sources (greater than 48kHz), ultrasonic content is preserved by the correction filters.

If your microphone and calibration are good beyond 20kHz and you wish to take advantage of that, measurements must be done at 88.2 or 96.

 

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On 9/27/2023 at 8:23 PM, dericchan1 said:

My main system speakers fr from 35hz to 100khz. 

IMG_8234.jpeg

Which speakers do the above specs go with?

 

The Earthworks Mxx MIC's go down to 3Hz and are good up to 140db SPL levels but even their best one (M50) "only" goes to 50kHz. If I wasn't so cheap at the time looking back on it I should have bought the M50 myself instead of the M30 so I could capture the advertised upper range of my speakers (50kHz). Despite not being able to hear anything at that range, I would sleep better at night knowing that I captured everything possible that I paid for in terms of the speakers being used.

 

I'm afraid to ask what measurement equipment might cost that could capture from single digit bass up to 100kHz accurately. In this case I would let it go and live with the M50.

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1 hour ago, cjf said:

Which speakers do the above specs go with?

 

The Earthworks Mxx MIC's go down to 3Hz and are good up to 140db SPL levels but even their best one (M50) "only" goes to 50kHz. If I wasn't so cheap at the time looking back on it I should have bought the M50 myself instead of the M30 so I could capture the advertised upper range of my speakers (50kHz). Despite not being able to hear anything at that range, I would sleep better at night knowing that I captured everything possible that I paid for in terms of the speakers being used.

 

I'm afraid to ask what measurement equipment might cost that could capture from single digit bass up to 100kHz accurately. In this case I would let it go and live with the M50.

My speakers are the Monitor Audio Platinum PL200ii floorstanders

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