Questions before getting started

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billgr
Posts: 4
Joined: 06 Nov 2021 03:56

Questions before getting started

Post by billgr » 12 Dec 2021 03:07

Hi there.

I have a number of questions (I'm sure many more will come later).

For recording the sweeps I expect I need to run the LSR software on a computer that is connected to my dac (I use USB).

I impulsively purchased an XTZ Microphone Pro. Is the XTZ good enough for this purpose"?

The XTZ microphone preamp has an analogue output. The XTZ manual states the analogue output is "Only needed if use of acoustical measurement software. For room correction softwares use your playback connection (e.g. external DAC)." Do I need connect the XTZ analogue output to the hifi?

My dac provides volume control and I don't use a preamp. What is the correct volume to run the sweeps and does this depend on the frequency range being generated? I could not bear to hear high frequencies at 90dB for example.

If I make changes to the system will it be necessary/desirable to make new FIR filters. I mean changes such as software player and it's settings, cables, preamp, amps (not speakers or equalization)?

Thanks, Bill
PhilActiveAudio
Posts: 55
Joined: 21 Jan 2021 21:51

Re: Questions before getting started

Post by PhilActiveAudio » 12 Dec 2021 11:08

Hi Bill

I think you are missing one element in the chain.

You have the DAC to play the sweep and a preamp with the mic, but you need a card to record the mic. I would suggest you to buy a USB card to be connected to your Mac, to the DAC (using digital connection if possible) and to which you will connect the mic (using the output of the preamp or directly connected to the mic if the card has a preamp inside). The card must be ASIO compatible to be used by Acourate. It must also be unique to properly handle timings.

There are many brands: RME, Focusrite, Motu, Behringer…

I would also suggest you to read the various articles made available on AudioVero site (Mitch, Archimago). You will find many answers there.
exaSound e68 DAC ==> class D / Accuphase / class D ==> Jensen Supravox / Arai Radian / Fostex
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dsnyder
Posts: 21
Joined: 22 Oct 2019 13:52

Re: Questions before getting started

Post by dsnyder » 12 Dec 2021 21:53

billgr wrote:
12 Dec 2021 03:07
Hi there.

I have a number of questions (I'm sure many more will come later).

For recording the sweeps I expect I need to run the LSR software on a computer that is connected to my dac (I use USB).

I impulsively purchased an XTZ Microphone Pro. Is the XTZ good enough for this purpose"?

The XTZ microphone preamp has an analogue output. The XTZ manual states the analogue output is "Only needed if use of acoustical measurement software. For room correction softwares use your playback connection (e.g. external DAC)." Do I need connect the XTZ analogue output to the hifi?

My dac provides volume control and I don't use a preamp. What is the correct volume to run the sweeps and does this depend on the frequency range being generated? I could not bear to hear high frequencies at 90dB for example.

If I make changes to the system will it be necessary/desirable to make new FIR filters. I mean changes such as software player and it's settings, cables, preamp, amps (not speakers or equalization)?

Thanks, Bill
Hi Bill. Welcome. :)

If this is the mic that you purchased: http://www.xtzhifi.com/product/microphone-pro.html
Image

…then you mostly have what you need. Looking at the manual for the supplied "Room Analyzer II" device, I do see a few issues, but they may not be impossible to overcome. The major one is lack of an ASIO driver, which Acourate LSR requires. It may be possible to use ASIO4ALL, but I've never had much luck with that. YMMV.

The other issue is that there's only one analog output from the device. They provide a splitter, but that's not helpful since, with Acourate, you want to measure each channel separately. As a workaround, you can measure the channels one at a time. Measure the left channel, mute your preamp, move the cable to the right input, unmute, and measure the right channel. This will quickly become irritating, so it may be worth investing in a Focusrite Scarlett Solo or similar. The Scarlett series of audio interfaces come with ASIO drivers and have separate outputs for left and right channels, making use with Acourate and REW much more convenient. I'm not able to find information on the phantom power requirements of the mic, but it's almost certainly compatible with the 48 volts provided by the Scarlett Solo and similar devices.

If you don't have one, you'll need a mic stand as well. Nothing super fancy, but something that is stable and can hold the mic at ear level.

I don't know if the XTZ Microphone Pro comes with calibration files. Ideally, you'd like to have a calibration file for 0º orientation, that is, the mic pointed in the direction of the loudspeakers instead of towards the ceiling (90º). If the mic came with a calibration curve and the manufacturer did not specify, it's almost certainly for vertical orientation. If that's the case, reach out to the folks at Cross•Spectrum Labs to see if you can send your mic to them to have calibration files created for 0º orientation. Also ask XTZ if they have a calibration file for 0º orientation.

You have the right idea about connections. When I'm doing measurements, I connect both analog outputs from my Focusrite Scarlett to the preamp in my audio system. I connect the mic to the XLR input and the USB cable to my laptop. Once everything is powered up, I engage phantom power and adjust levels. I usually set the volume on the preamp to whatever level is comfortable for listening and then fine-tune using the output gain knob on the Scarlett. I use a separate SPL meter or app on my phone to make sure that the loudest part of my sweeps is no more than 75 dB. This is important to avoid speaker and hearing damage but also to ensure that the sweep recording does not have excessive distortion.

Your filters should be stable across changes to electronics and cables; however, you'll want to rebuild filters after any significant change to the room. For example, adding or removing furniture or room treatments, any change to speaker placement or listening position, adding or moving subwoofers, different loudspeakers, etc.

Edit: I see that you don't have a preamp, that that's okay. Sometimes, I'll connect my Focusrite Scarlett interface directly to the inputs of my power amplifiers. It has a volume knob, so I start with it turned all of the way down and gradually increase the level until sweeps peak at 75 dB. If you're recording sweeps from within Acourate, there's a volume slider that you could use as well. Again, start out with levels very low and gradually increase while looking at your SPL meter or app. If ASIO4ALL works, you may be able to sort-of get by with the XTZ provided interface, but I think you'll be much happier with a proper external audio interface like the Focusrite Scarlett Solo. Good luck!
Acourate system: Roon -> Gustard X16 DAC -> Topping Pre90 -> Orchard Audio monoblocks -> Fritz Carrera 7 BE monitors + REL T7i subs
billgr
Posts: 4
Joined: 06 Nov 2021 03:56

Re: Questions before getting started

Post by billgr » 12 Dec 2021 23:22

Thanks for the replies.

I plan to connect in this manner
Sweeps: Notebook (Acourate LSR) > usb > DAC > XO > Amps > speakers

Recording: Mic > Mic Preamp > usb > Notebook (LSR)

I still don't understand why I need to use the analogue output from the microphone preamp. I'm not intending to use the XTZ interface. I want to use Acourate LSR but with the XTZ microphone. What am I missing?

I can run L or R sweeps from LSR so only the chosen channel (eg left) will be passed to the Dac with silent right channel, right?
Or does LSR put the left signal out on both channels, surely not?

It's good to know the volume can be controlled in Acourate.

I'll check whether the XTZ has an asio driver or else I'll test it with asio4all.

I have a couple of mic stands.

The XTZ Pro has a calibration file (for 0º and 90º) but it's generic and only accurate to 1dB. I probably wouldn't have bought it if I knew that at the time.

Thanks for the help, Bill
billgr
Posts: 4
Joined: 06 Nov 2021 03:56

Re: Questions before getting started

Post by billgr » 16 Dec 2021 00:06

Can anyone help with this question please? Maybe Uli can help?

Why do I need to use the analogue output from the microphone preamp if I want to use Acourate do make the room measurements?

I wonder if it seems too obvious to you all but not to a complete novice.

Thanks, Bill
JohnG2021
Posts: 1
Joined: 14 Dec 2021 05:34

Re: Questions before getting started

Post by JohnG2021 » 18 Dec 2021 06:07

billgr wrote:
12 Dec 2021 23:22
Thanks for the replies.

I plan to connect in this manner
Sweeps: Notebook (Acourate LSR) > usb > DAC > XO > Amps > speakers

Recording: Mic > Mic Preamp > usb > Notebook (LSR)

I still don't understand why I need to use the analogue output from the microphone preamp. I'm not intending to use the XTZ interface. I want to use Acourate LSR but with the XTZ microphone. What am I missing?
Hi Bill

From the above it seems that perhaps you are intending to use 2 separate usb interfaces which is probably not going to work as Acourate can only access one usb (ASIO) interface at a time, with both input and output channels for the LSR output to your dac, and microphone input, all in the same unit (eg a Focusrite Scarlett Solo as suggested or similar). If you intend to use a mic preamp then the analogue output from the microphone preamp would need to be patched into the usb interface that Acourate is using so that the LSR can record the input from the mic. Hopefully that clarifies things. :)
billgr
Posts: 4
Joined: 06 Nov 2021 03:56

Re: Questions before getting started

Post by billgr » 19 Dec 2021 02:42

Thanks for that explanation. I must say I'm a bit surprised that Acourate can only use one device at a time. Though perhaps there are technical reasons for it (possibly to do with measuring the delay between output vs input signals)?

The terrific sound of my system depends on the quality of my dac and I doubt that using a cheap audio interface is going to work all that well. I wanted to play the sweeps through my dac so I the filters are correcting the actual sound of my system, not a component that I won't normally use (eg a Scarlett Solo). I would want to use a very good adc for the measurements too.

Even small tweaks to the music server software can make a big difference to the overall sound (eg bass clarity and slam). And that sound is a function of the system and the room interactions, so I expect I'll need to tweak the convolution files when these changes happen. I am mindful that electronics are supposedly less influential in room correction than speakers and furnishings. But surely to get the best result, everything matters.

In summary, I guess my options are
1. use my XTZ microphone/preamp with a Asio4all and splitter cable, and manually disconnect cables for L and R speaker sweeps
2. try an inexpensive interface device like the Scarlett Solo that supports both output and recording of the sweeps on single and dual channels
3. use something other than Acourate to make the room measurements (if I can find something else).
Ecwl
Posts: 43
Joined: 19 Feb 2021 01:05

Re: Questions before getting started

Post by Ecwl » 19 Dec 2021 04:21

My understanding is that even though Acourate can use ASIO4ALL to access 2 USB devices at the same time (one for playback and one for microphone recording), there is no guarantee that the recording USB microphone timing wouldn’t be off because both USB devices would be accessing the clock or something like that. It is not so much that you can’t do it, it’s just that there is no guarantee of accurate measurements. I suspect you could have two computers and one to play the LogSweep file back and another to record with the USB microphone.

The other issue with the XTZ microphone pro is that the calibration file is rather generic and not microphone specific so from what I read elsewhere online, it can have errors.

I personally also think that It is also really not necessarily true that you want to use your high-end DAC to playback and measure because it depends on what you want to do. If you have a high-end DAC that has specific filters, e.g. long-tap-length, NOS, minimum phase, and you playback using your DAC and run Acourate, Acourate would change the filter to be minimum phase with the step response because that’s what you’re feeding Acourate to change your measurement towards your target. But if the goal is to just do room and speaker correction, even if you use a different DAC/microphone setup, once you have the correct measurements to create the correct convolution filter, once you apply it to your high-end DAC, you’ll be able to preserve the DAC’s original filter characteristics because your convolution filter only corrected for the speakers and room issues and not the filter characteristics of your high-end DAC.
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UliBru
Posts: 433
Joined: 19 Oct 2019 13:58

Re: Questions before getting started

Post by UliBru » 20 Dec 2021 08:53

billgr wrote:
19 Dec 2021 02:42
Thanks for that explanation. I must say I'm a bit surprised that Acourate can only use one device at a time. Though perhaps there are technical reasons for it (possibly to do with measuring the delay between output vs input signals)?

The terrific sound of my system depends on the quality of my dac and I doubt that using a cheap audio interface is going to work all that well. I wanted to play the sweeps through my dac so I the filters are correcting the actual sound of my system, not a component that I won't normally use (eg a Scarlett Solo). I would want to use a very good adc for the measurements too.

Even small tweaks to the music server software can make a big difference to the overall sound (eg bass clarity and slam). And that sound is a function of the system and the room interactions, so I expect I'll need to tweak the convolution files when these changes happen. I am mindful that electronics are supposedly less influential in room correction than speakers and furnishings. But surely to get the best result, everything matters.

In summary, I guess my options are
1. use my XTZ microphone/preamp with a Asio4all and splitter cable, and manually disconnect cables for L and R speaker sweeps
2. try an inexpensive interface device like the Scarlett Solo that supports both output and recording of the sweeps on single and dual channels
3. use something other than Acourate to make the room measurements (if I can find something else).
Acourate is designed to use Asio. There are mainly advantages and but also the disadvantage that multiple Asio drivers cannot be used at the same time.
Now with measurements we have the situation of analog input and outputs at the same time. For processing thus we need a AD and DA conversion. This is no problem with the same device using also the same clock inside. In case of USB mics the clocks for ADC and DAC are different and we can be pretty sure that they do not perfectly match. The results are time stretching effects.
Now it is possible to use such independent devices by Windows drivers and thus Asio4All gets into the game. Asio4All mimics an Asio driver but uses Windows drivers at the end. So we can do the desired recording but we must expect that at the end it is necessary to compensate for the time drifts.

At the end this problem is the same for all recording programs. As it is a problem by principle.

So my clear advice is to use a soundcard for ADC and DAC with a common clock. If this is not possible or desired you can use Asio4All and AcourateLSR3. AcourateLSR3 applies 3 sweeps in sequence left - right - left channel and detects the time drift. Thus it tries to compensate for it.
Stay well tuned
Uli

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Acourate system: JRiver/Roon -> AcourateConvolver -> miniDSP U-DIO8 -> TacT M/S2150 amps -> DIY horn speakers
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