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Article: Audiolense Digital Loudspeaker and Room Correction Software Walkthrough

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Hi @mitchco,

Thank you for your article and ebook. They have been very helpful. I've redone my 2.1 with digital XO for the sub and tweeter using audiolense. I'm very happy with the results.

Unfortunately, I've only managed to get measurements using windows mme or directsound (I do click 'using separate playing and record streams'). Bernt said ideally ASIO4all, or Wasapi should be used. Unfortunately, I always get an error message saying 'perhaps too many channels', or PaInvalidChannelCount, unexpected host error etc... I've tried AL 5.5, &6.0 both in 32 bit and 64 bit. I've installed Jriver, activated WDM, etc but having no luck.

I must be missing something, or maybe I'm worrying about nothing and should stick with what works?

Do you have any suggestions?

Omid

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Hi @omid Welcome aboard! And thanks! Perhaps you can briefly describe your measurement mic, gear and signal path for taking measurements? I doubt you are missing anything, but always good to have a 2nd pair of eyes have a look. Having said that, if you are happy with the SQ, then stick with what works. But lets have look anyway 🙂

 

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For measuring, with audiolense 5.5 (32 bit), my laptop runs on Windows 10, 64 bit. My input is a Calibrated USB mic (UMM6). The output is a Xonar U5 external sound card, set to 5.1, 48kHz, 24 bit (both windows and the sound card are set to the same sample rate). The sound card's front output goes to the analog input of a benchmark DAC2 --> AHB2 --> Tannoy Stirling GR woofer. The R+L rear outputs go to the analog input of a single velodyne DD12 subwoofer (all equalizers, crossover defeated). The Center+Subwoofer outputs go to the analog input of a marantz NR1609--> Tannoy Stirling GR tweeter. 

The channels in AL are set to 4,5 for L+R subwoofer, 0,1 for woofers, 2,3 for tweeters, which works correctly when the driver is winmme, or directsound. Just can't get it to work with JRiver, Wasapi or ASIO4A.

For playback, I use Roon Rock and its DSP. USB output to Benchmark DAC -->woofers. Internal roon rock soundcard -->subwoofer. Xonar soundcard-->marantz--> tweeter. I then use Adobe audition to measure by how many milliseconds  the signal is delayed for each output and correct for that. I play sweep test tones through Roon, and measure with REW. I'm getting a decent step response and house curve matching frequency response. After DSP correction, the volume does drop by 10dB or so, which is annoying (I use partial correction, only correcting up to 9000Hz, so as to avoid a larger drop). 

Please let me know if I left out any info you need.

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Hi @omid Very nice! If you are getting a good step and frequency response with REW, then everything is fine.  Does the Xonar card come with an ASIO driver? One thing you could try if you have not already is to check the response of the signal path sans speakers and mic. But if you are getting a good step and frequency response out of the speakers, then it is likely there are no issues at all.

 

Wrt the attenuation of the digital filter, in JRiver's convolution you could click on normalize filter volume which would bring some gain back. Is there a similar setting in Roon? Another way is to add a digital gain stage. In JRiver, one could use the eq plugin just to add gain, but with no eq. There are VST plugins that can do this as well. I have used Blue Cat's Gain Suite to do this. Just have to watch for any clipping.

 

Seems like you have it all sorted. I think Bernt is working on some of the multichannel issues in AL V6, so this may also allow the use of Wasapi or ASIO. But it seems to me there is nothing to worry about.

Cheers,

Mitch

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Thank you. That helps. 

I moved my subwoofer yesterday, and tried to repeat the measurements. The first set of sweeps worked. When I tried another sweep, the sound stuttered (buffer under run?). After that, I started getting error messages PaDeviceNotFound or something like that (Puzzling since I hadn’t touched the driver or any settings). Tried numerous pc restarts and relaunchings of  AL, same result. 

I’ll try safe mode today, maybe there is a driver conflict. I was just curious if you knew of any tricks to sort out my problems. 

Wrt volume, Roon does let you amplify. It also has a clipping warning. Although the signal is diminished by 10dB or so, the signal clips if I amplify it (i guess some frequencies are boosted by more than 10dB).  

Benchmark DACs and amplifiers don’t have a lot of gain, so 10dB matters. 

I’ll eventually get rid of the xonar soundcard and marantz for the tweeter and get another DAC and amplifier (or maybe I’ll finish building my Nelson pass F5 v3). You’re lucky your Hilo can simultaneously process bass, mid and treble streams at the same time. I technically need 3 DACs. 

 

Cheers. 

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I’m having a puzzling problem, I’m hoping someone with DSP knowledge (hint, @mitchco) may help me solve. 

 

I made a convolution filter through AL making sure ‘all in one’ is selected (so R and L channel corrections are correlated). My mic was equidistant within 1/8 inch when I recorded and generated the correction.

 

I then implemented the convolution in Roon and recorded the output from the sound card directly into my laptop’s line in. The sound card handles the twitters (ie 1800Hz and above).  I recorded the signal using adobe audition. R and L channel signals start and stop at the same time without any DSP, whereas filter corrected sounds have 1 ms delay on the R channel (34 cm difference). The delay is not frequency dependent, ie not likely to be a phase correction related delay.  

 

I imagine the twitter signal should arrive at one’s ears at exactly the same time for a centered voice. Am I missing something, or is Audiolense tripping?

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