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Article: Advanced Acourate Digital XO Time Alignment Driver Linearization Walkthrough


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Hello justM, have a look at the link in the article, just before the Conclusion, that points to Tony Knight's system. There is a diagram that is somewhat different than what you are asking for, but is conceptually similar.

 

Hello lazy, yes, the Hilo is connected via USB to the computer and Hilo's 6 analog outputs are input to the 6 amplifiers. Internally, the Hilo has a 32 x 32 channel mixer that allows one to route any input to any output, including digital and analog loopback. However, Acourate does not require patching manual loopback, but does require ASIO. With respect to measurement mic requirements, and how to hook up, please refer to the intro article on Acourate.

 

Hello Archimago, thanks for the kind words. Keep up the great writings!

 

Best regards, Mitch

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Hi Michael, thanks! While I was working at the state of the art studio, I gave up on my home system, which at the time were Magneplanar 2.6R's (with real ribbons) paired with a Classe Audio DR2 Class A amp. Nothing wrong with the gear, but the sound quality could not compare to the purpose-built acoustically designed facility. And for good reason, that state of the art facility cost several hundred thousand to construct (without gear).

 

I got back into it not too long ago when I came across high resolution DSP software designed to optimize ones speakers and room. At the time I had a very lo-fi setup (Logitech G51 plastic computer speakers :-) and to my surprise, I heard an inkling of what may be possible. The full realization of which is now contained in this article.

 

Hi scintilla, thanks for the kind words. Yes, Uli confirms that one can measure a passive speaker in the near-field (best in free-field to avoid as much reflections as possible) and derive an overall linearization filter. The filter can also be used as pre-filter in the LogSweep Recorder. The final room correction filter will contain both the speaker correction and room correction. Have fun!

 

Best regards, Mitch

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Hi Mitch,

 

Been a bit of a voyeur when it comes to Acourate, but your post has come at the right time and has persuaded me to push the button on the software and mic.

 

I have bought a Void Indigo speaker system, and need to use the XO function as well as the DRC of Acourate to get it up and running.

 

To that end i have bought an 8 channel ADC / DAC - the Lucid 88192 which i can find at a good price.

 

Jriver will take over the front end and volume control duties.

 

i will send digital audio out via the toslink on my computer and into the Lucid running at 48KHz (until i find a 24/192 card with a decent AES digital output.)

 

Is relying on JRivers volume control a safe option and are there any glaring problems you would forsee?

 

Thanks

 

Mike

 

Hi Mike, cool project!

 

With respect to 24/192 AES card, in addition to CA, you might try searching/posting at the Acourate forum and JRiver sound card forum if you haven’t already.

 

JRiver’s digital volume control has worked flawlessly for me. The volume protection works perfectly and the SQ is as good as it gets.

 

Let us know how your project progresses.

 

Best regards, Mitch

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  • 2 weeks later...

Hi Christian, I wish I could walk through the software you listed. Unfortunately, I am not a full-time audio reviewer, perhaps someone else on CA has experience with the software you have…

 

Hi Gordon, thanks for your comments. With respect to identifying frequencies, I like the classic Carnegie Hall chart that can be ordered separately or comes with Bob Katz’s excellent book on Mastering.

 

Re: amplifiers. As a system designer, using state of the art Digital XO, I can match individual speaker components to amplifiers of choice. My choice of amplifiers are based on what the best match is for each individual speaker driver to most accurately reproduce what is stored in digital media on disk.

 

As mentioned in the article, the 15” bass driver/cab requires some power and a reasonably high damping factor to accurately track the electrical waveform being fed to it. However, the compression drivers require very little (literally milliwatts of) power and low damping factor to accurately track. From a system design perspective, I can tailor fit a high power, high damping factor amplifier to provide the bass driver with transient impact and damping control at the same time. With the ACA’s sonic signature similar to Nelson Pass’s commercial Aleph J design, I can get a very detailed, yet smooth response from the compression drivers/horn combos, which have very different electrical load requirements compared to a 15” cone bass driver loaded in a BR cab.

 

Re: “The reason was that the differential in sound between the amplifiers was greater than the differential in sound of the drivers or the electronic xover.” I would say that the sonic signatures between the two Nelson Pass amp designs are somewhat audible if directly compared to each other. However, from a system design perspective, they are synergistic when used together to match the individual electrical load characteristics of each driver, which is what I am after.

 

Take a look at any of the acoustic frequency responses, distortion measurements, and impulse/step responses in this article. Even with the corrected responses, the variability is still greater than virtually any modern amplifier would measure today. Speakers and rooms have the most variability in the audio chain and can benefit the most from modern DSP. Hence the article on Advanced Acourate and by following the steps in the article one can get closer to accurately reproducing music that is stored digitally on disk.

 

perolater, thanks for your kind words. Acourate is state of the art Digital XO with capabilities to time align and linearize all drivers, and provide room correction. It is an ear opening experience. Let us know how your project goes!

 

Best regards, Mitch

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  • 2 months later...

Hi David,

 

Yes, in my case, the line out goes to the bass amps, the monitor out goes to the mid amps, and the headphone out goes to the HF amps. I have extensively tested and listened to each of the three stereo analog outputs and cannot detect any differences. The specs are virtually identical for each set of analog outputs.

 

The monitor and headphone outs have an independent analog volume control which allows one to trim and match the levels given the (very) different driver sensitivities (e.g. woofer versus compression driver). As a side note, low noise amps on the mid and treble compression drivers will be important.

 

I am extremely happy with the SQ of the Hilo. Personally, I feel its transparency is second to none. I had a Lynx L22 PCI card and while it is no slouch, I believe the Hilo is a significant improvement. The flexibility of the Hilo allows me to do virtually anything I want and I have yet to come across a patch/routing scenario that can't be done.

 

Here is a link to a few other converters: High-quality 8-channel analog output that may be of consideration.

 

Last point, ensure that the interface/converter has a quality ASIO driver. Hilo's is one of the best and is multi-client. Other's not so much and another check point on the list.

 

Let us know how you make out!

 

Cheers, Mitch

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  • 2 months later...

Hi chrisr, I am happy you found the article useful. Wrt SRC, I have tried several approaches/combinations, including using JRMC 19's SRC and Convolution engine. To my ears, all sounds transparent, and using null or difference testing, any measurable difference is below my auditory threshold. For myself, Acourate computes the filters and I use 48 kHz as the input sample rate as that is what I use in the LogSweep Recorder to measure. Cheers, Mitch

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  • 3 months later...

Michael, I am glad you found the guide useful. Uli has answered all of my technical and math questions, well above and beyond Acourate product support. I must say that Acourate is the most technically advanced and transparent audio DSP toolbox I have ever used/heard. Thanks to Uli for his most excellent software product and customer support.

 

The Lynx Hilo AD DA converter is vastly underrated for $2500. To my ears, one of the most transparent AD AND DA converter I have ever heard. According to one set of objective measurements, ranks #2 out of some 60 AD DA converters tested for transparency: Evaluating AD/DA loops by means of Audio Diffmaker

 

The Hilo’s ASIO/MME/DirectSound audio driver supports multi-client software applications. For example, one can be playing/streaming music in one application and record it in another at the same time. As a part time binaural recordist and musician, plus owning a turntable, I have yet to come across a routing scenario that the Hilo cannot support.

 

Another multi-client scenario is using REW to measure the acoustic output of ones speakers, while at the same time sending REW’s sweep signal via JRiver Media Center (ASIO input) with the Convolver engaged and loaded with Acourate FIR correction filters. No timing reference required. Use 48 kHz sample rate and ASIO drivers in both REW and JRMC. This is useful to confirm the performance of the corrected system and gives insight to what a good measurement looks like and correlates well with what one hears.

 

For example, aside from frequency response, time alignment/coherence is another important attribute for accurately/transparently reproducing recorded music to the listener’s ears. As mentioned in this Stereophile article, Measuring Loudspeakers, Part Two Page 2 | Stereophile.com one can use a step response measurement to show how time aligned or coherent ones speakers are. The Stereophile article points out what a good and not so good step response looks like, Measuring Loudspeakers, Part Two Page 3 | Stereophile.com. Mine look like this:

 

customspeakersstepreponse_zpsd739bd50.jpg

 

The acoustic step response of my system accurately tracks closely to the electrical input to the system. Also noted in the Stereophile article is that the step response is very hard for speaker systems to deal with and very few do it accurately. Personally, I feel a large audience of music lovers are missing out on this important aspect of music reproduction, which is just as audible in imaging as smooth frequency response is for tonality.

 

Enjoy the sound! Cheers, Mitch

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  • 1 year later...

Hi Reginal25SF, sorry it took so long to reply, I have been away a while. Yes, Acourate is completely transparent in my opinion, both from a listening and measurement perspective. There are other testimonials to Acourate's transparency you will find in the first article: Computer Audiophile - Acourate Digital Room and Loudspeaker Correction Software Walkthrough

 

Hi Ronnie, that's awesome! I am glad you found the article useful. It makes a remarkable audible difference moving to a digital XO, driver linearized, and time aligned system. Amplitude and excess phase correction are icing on the cake.

 

Have you settled on a target response? Fyi, REW measurement software has recently implemented frequency dependent windowing and psychoacoustic smoothing that closely matches Acourate's analysis window. That means one can use REW to validate Acourate's FIR filters to see how closely they match the target response. Here is a REW measure of my right speaker at the listening position with the new psychoacoustic smoothing applied, overlaid with the target response I used in Acourate:

 

 

REW psy with target overaly.jpg

 

Virtually identical. Measurement signal path is REW digital output routed to JRiver ASIO (digital) line input using Lynx Hilo internal mixer, through JRiver’s 64 bit Convolution engine, hosting Acourate generated FIR filters containing 3 way digital XO, time alignment, amplitude and excess phase correction, out to 6 channels of Hilo DAC to 6 amps and speakers, right speaker to mic at listening positon, mic preamp, to ADC Hilo converter to REW digital input. I have not got around to driver linearization with a recently changed HF compression driver and waveguide. It is amazing to me the level of precision between the target and measured response given the number of transfer functions in the signal path :-)

 

It would be cool to see some measures of your Emerald Physics in REW if you get a chance.

 

Best regards, Mitch

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  • 5 months later...

Hello Doug, thanks for your comments. I would suggest that you post your questions on the Acourate forum at https://groups.yahoo.com/neo/groups/acourate/info Based on my experience, you are likely to have more than one question :-)

 

Subs present a unique problem in the time domain as the peak of the waveform spans multiple samples, so what is considered the peak sample to time align the mains to? There are many knowledgeable people on the Acourate forum that have a sat/sub set up like yourself and can speak directly to time aligning that combo better than myself as I don't do subs. Time aligning subs to mains is worth the effort.

 

Best regards, Mitch

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  • 3 years later...

HI @malarz I am not sure I understand the context... Assuming you have 6 DAC channels for a stereo 3- way active setup and outputting the DAC channels directly to the input of 6 channels of amplification? If so, does the DAC analog outputs have level control?s Or do your amplifiers have an input level controls? If so, then the idea is to trim the input level of each amplifier so that the logsweep produces a reasonably flat response or tilting downwards response as the frequency increases over the full range. Usually you run the woofer amp channel wide open as the woofer has the least sensitivity, then the midrange and then the tweeter needs the most level attenuation to be in line with the woofer and midrange levels... I may have misunderstood your question...?

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  • 9 months later...

Hi @Victor Varga

 

Yes. I have been using the headphone output on the Hilo since 2012 in a variety of active 3 way systems. Sometimes on the bass drivers, one time on compression drivers and waveguides. You will either need some cable adaptors or make your own cable with the proper connectors for your setup. I did the latter and have had no issues, sounds very good!

 

Kind regards,

Mitch

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  • 9 months later...

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