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About mitchco

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  1. mitchco

    Article: A New Listening Room Part One

    Bravo Chris @The Computer Audiophile! What a wonderful audio journey you are on. You just got to hear first hand how a room can have such an impact on sound quality with the same equipment. One item you may want to bring up in the next article is the comparison of room decay time or RT60 with REW. There is a recommended target response, based on room volume as to what the decay time should be. In the case of your room and most peoples for that matter, there is a range typically between 400 and 600 milliseconds. The rule of thumb is to aim for as much liveliness in the range, as too dead of a room sucks the life out of the music. Speaking of room ratios May I make a suggestion and I know it is after the fact. If you look at room ratios, some are better than others for the distribution of low frequencies, which sounds better to our ears. One can use a Room Mode Calculator to punch in the dimensions of ones listening environment and basically get the gist of the distribution of room modes. There is even audio output so you can hear first hand the trouble spots as you move the mouse cursor along the graph. Don't forget to turn down the volume before you try it. https://amcoustics.com/tools/amroc My room ratio sucks and near the 2nd worst ratio one can get outside of a cube. This is why I am into DSP, as no amount of bass traps can unf&*k the physical dimensions of my room. My reviews of Acourate and Audiolense are testament on how good these DSP products work, but if you can start out with a decent room ratio, you are further ahead to begin with. Which brings me to my recommendation for your room. Looking at your dimensions that I popped into the room mode calculator: https://amcoustics.com/tools/amroc?l=21&w=13.9&h=9&ft=true&re=DIN 15996 - Studio Note I reduced the length from your 25' 8" to 21 feet length. Have a look at the Bolt area chart. That room ratio is a favourable ratio. Now punch in 25" 8". How much audible difference will it make? Well, the bass is unlistenable in my room without DSP. Having worked in a number of well designed studio control rooms and listening rooms with favourable room ratios, always best if you can do it. So it means putting up a false wall... the false wall could also help with low frequency damping... like a Helmholtz resonator. Whether practical or visually appealing, of course is an issue. If it is a potential room mod, Vicoustic would have to run the math to confirm. Regardless of any changes, this room will sound better than the 6.5' ceiling room. Congrats! All the best on your audio journey Chris! Mitch
  2. Hi Mitch,


    My setup is stereo, two-way speakers in MTM configuration. I use JRiver MC to play my music and use the convolver with wave files created using REW and Rephase. These files are made up of the crossover and amplitude correction of each driver. The driver acoustic offset is contained in the config file header section. What I can’t get to grips with is, having done an in room measurement at the LP and generated a correction file, how do I combine the crossover filters with the room correction. This is where I turned to Audiolense and Acourate to see if I could bring all the measurements and corrections into one workflow.


    Having read all of the documentation and your e-book there does not appear to be a start to finish workflow describing the correction of a fully active system. The correction of individual drivers and room/system correction seems to be treated as two separate processes. For example, in your (excellent) book you start with room correction of a passive crossover system and end with driver correction for an active system. This means there is a gap in the workflow when starting with driver correction and ending with room correction. It is this gap I was hoping you could fill in.

    1. mitchco


      Hi Iain, the missing piece is convolving digital XO with room correction. This is what both Acourate and Audiolense performs in the software. I sent you a detailed workflow via PM. Hope that helps. Mitch

  3. Hi @hifi_swlon Yes, they had a very nice midrange up to about 4 kHz and then got way too bright for me. Also the bass quality is different. Don't know how best to describe it, but certainly no cabinet sound. Here is an overlay of the D&D and Phantom Gold frequency response measured at the listening position: One can see a smoother and flatter low frequency response of the 8c due to is unique passive cardioid design and DSP . Then both perform more or less equal from about 300 Hz to about 4 kHz - like I say, nice midrange and directivity. Then from 4 kHz on up, the Phantom simply has way too much high frequency energy for my ears. Of course, I can easily apply external DSP. But that can be applied to any speaker... So what can the speaker do itself? Unless something has changed with Devialet, it is a shame that they don't at least have a treble or tone contour control. But then that leaves the bottom end peak and dip...
  4. Hi Arnaud, Can you take measurements? I would suggest trying the on board DSP first. If you can get ±3 dB tolerance in the frequency response using the on board DSP, then you have achieved studio control room frequency response accuracy. If not, then yes, external DSP control can be used to achieve the goal. It would be nice if the external DSP correction is from about 500 Hz on down and leave the natural voice of the speaker alone above 500 Hz. Even in my problematic room ratio room, I was able to achieve ±3 dB accuracy with the on board DSP. Good luck! Mitch
  5. Hi @Emlin I reached out to Martijn again. I have seen part of his travel schedule and could be a while May I suggest you reach out directly to Dutch and Dutch at their website, Facebook or twitter contacts.
  6. Hi @ianmc Send me a PM with what you have and want to accomplish, as I am not sure about the context of your question. Thanks, Mitch
  7. mitchco

    How About Soundstage HEIGHT?!

    Folks may be interested in giving this a listen: https://www.audiocheck.net/audiotests_ledr.php
  8. mitchco

    Article: Kii THREE Loudspeaker Review

    Thanks @Chiptech It took a while to find a doc on what Space Optimisation does: http://docs.linn.co.uk/wiki/images/8/84/SpaceOptimisation.pdf I have no doubt it makes a difference, as room modes, factoring in distances, absorption coefficients in an open or closed space is well known in small room acoustics. Both the Kii THREE and the D&D 8c use a similar technique for room boundary issues. It would be interesting to see before and after measurements to verify the effectiveness... Have you seen any? Thanks for the link to the electricity article. I will look at it in more detail when I have some time. Happy listening!
  9. Wow, I am curious at what sound pressure level this is being listened to at the listening position? Do either of you have a SPL meter or can use a SPL meter app on your phone as a rough indicator? I only managed to get the limiter to kick in on some very bass heavy tracks approaching maximum output. That's perceived as 4 times louder than reference level of 83 db SPL... So what are folks measuring SPL wise?
  10. Hi @Emlin I reached out to Martijn @mensink and he said he would try to answer the q's today or tomorrow...
  11. mitchco


    Hi Dennis, To answer your question, there were 2 issues with the recording. One was the tube amp was switched out with an unknown amp and I heard something similar as you are describing during music playback and of course it got recorded. Arch heard it too and we did not have any time to troubleshoot the playback issue. The other problem is that the little Sony action cam has a built in automatic gain control that can't be disabled. Had I done it a 2nd time, I would have brought my own amps and the Hilo ADC would have produced a much better recording. Alas, it was a one time only shot and turned out reasonably good. But you are indeed hearing what you describe. PS. I tried to not move my head during the recording... I need to listen to the other recordings listed in the thread. In the meantime, folks might find these interesting: https://3diosound.com/pages/examples
  12. mitchco

    MQA The Truth lies Somewhere in the Middle

    @jabbr I just watched the video and was about to write similar to what you have written. Well said and agreed. Chris @The Computer Audiophile well done presentation! It is most unfortunate about the rude and unprofessional behaviour by a few folks. I give presentations in the software industry and that type of continual interruption is unacceptable in my industry. Folks that persist are asked to leave or escorted out. Kudos to you Chris for remaining professional throughout - respect! @Archimago and I had a great time at the Vancouver Art Gallery recently. You can even hear Arch speak on one of the binaural recordings - LOL. If Arch wishes not to use his real name, so what. The measurements and claims stand on their own merit. No-one in the "industry" has refuted Arch's measurements and claims. MQA is a company with considerable resources, so if they wanted to refute the measurements and claims, they could have done so and still can. The "fact" that they have not should be all the proof one needs 🙂 Keep up the great work Chris!
  13. Archimago, myself, and our lovely wives met up at the Vancouver Art Gallery where we viewed and listened to Kevin Schmidt’s: “We Are the Robots” exhibit. The exhibit runs to Oct 28, 2018. It is an incredible audio visual experience! Words and pictures can only convey so much of the experience, so I made three binaural recordings to share the audio experience. Listening to binaural recordings over headphones puts you in the room, listening to the exhibit. I first became aware of Kevin’s exhibit via a thread on diyAudio forum. Needless to say, as a diyAudio member, I had to experience the exhibit. Reaching out to the Gallery’s Communication Specialist, we arranged a time when our group could visit the exhibit. An interview was arranged with Kevin and I chatted with him just before making my way there. I asked Kevin if those were Nelson Pass KleinHorns. “Yes, I found Nelson’s plans on the Internet and tried to replicate them using the dimensions as best as possible.” I asked why these speakers. “They are ridiculously big.” He found it interesting that the entire architecture of the huge horn is designed to boost the low frequency response of the Lowther DX55 full range driver. What makes the design of this driver unique is its fast transient response with an equally fast damping factor, at the expense of low frequency extension. This is where the huge horn comes into play. There are easier ways to design for low frequency response in a much smaller enclosure, but usually with bigger speaker drivers. That’s the difference, as the magic is in this small, full-range driver. However, it requires this size of horn length and mouth to extend the low frequency response down to 40 Hz. The quality of the bass sound is as unique as its design. The binaural recordings do a reasonable job of representing this bass quality. Kevin saw images online of different audiophile listening rooms and some people constructing exotic speakers. He liked the audiophile discussions around the idea of the full range driver to give a truer sound without any sound loss versus traditional designs that used multiple speaker drivers and passive crossovers. Kevin created the exhibit to bring a DIY Audio sound reproduction system and acoustically treated listening room for folks to experience in a public place. An audiophile system like this is normally reserved to few private residences. The Exhibit Arriving at the Gallery, we took our LP’s up to the 2nd floor and had a look around. It wasn’t obvious where the exhibit was located, and the Vancouver Art Gallery is a large place. Before long, though, we found an entrance to a hallway along a wall towards the back corner of the floor. The hallway became a passageway lined with acoustic panels that really dampened the sound level. We became aware of the change in sound with our senses heightened. Nearing the end of the hallway, we could hear music playing. Turning right at the end is the entrance to Kevin’s exhibit: This picture was taken later on in our visit. When we first turned the corner, we saw a half dozen or so women dancing to Abba in front of the speakers, having a great time! One woman exclaimed that we had to dance before we could put our music on. That sums up the mood of the exhibit. Awesome! I am in the chair on the left with binaural mics in my ears, recording on a Sony HDR-AS100V Action Cam. We are all enjoying the music. During the two hours we were at the exhibit, a constant stream of folks wandered through. It was quite busy. In classic West Coast, Vancouver style, the acoustics and esthetics of the room had a welcoming feeling. With the music playing, it feels like you are hanging at your friend’s place, who happens to be an audiophile with an incredible sounding stereo, playing your records! While people were still dancing, Arch and I looked around the exhibit. This was on the back wall as we entered into the exhibit from the acoustically dampened hallway: I can relate, as my sound system is partly DIY Audio, including a pair of Nelson Pass ACA kit amps that I assembled. diyAudio’s motto: “projects by fanatks, for fanatics.” During my conversation with Kevin, he spoke about the details of the diffuser panels that make up the Excess Dispersion exhibit. Kevin used QRDude’s Quadratic Residue Diffuser (QRD) calculator for calculating the acoustic dispersion pattern for each type of diffuser panel. The software program automates the math calculations required to design the acoustic panel. When sounds bounces off the panel, rather than bouncing directly back like a mirror reflection, the sound is spread out in a pattern that diffuses the sound. Sounds that bounce directly back to the listener, produces what is called a comb filter, which colors the sound. In true audiophile style, we don’t want any coloration to our sound reproduction. Why not use more acoustic absorption panels, like the ones used in the hallway leading into the exhibit? Too much absorption sucks the life out of the sound and therefore the music. Some absorption is good, but the room needs to be a bit lively. Diffusing the sound instead of absorbing it, allows the room to be livelier, but with the comb filtering diffused or mathematically randomized: This is a close up of a 2 dimensional QRD panel. While the panel was constructed using reclaimed wood scraps, the mathematical pattern behind the design of the panel also reduces slap or flutter echo. The goal is to reduce the room coloration to the sound quality without making the listening room an anechoic chamber. While the mathematical calculation can be performed quickly with a computer, cutting each length of wood to a specific length, times the number of variations, times how many pieces of wood… … is a significant amount of manual effort. Same goes for the sidewall one dimensional diffuser panels. In fact, all of the furniture in the room including the equipment stand was designed and built by Kevin. On the back wall are 1D diffuser panels that Kevin constructed, again out of reclaimed wood: Photo courtesy of Mike Lee from diyAudio One will see this type of diffuser panel on the sidewalls of the exhibit as well. Let’s zoom in on the audio gear: That’s a lovely Thoren’s 320 turntable connected to a NAD phono preamplifier. Arch was spinning the Beatles and the women were still dancing. Unfortunately, the fun ended soon, as it turns out the needle in the cartridge was damaged, and that needle had just replaced the one before that. I can sympathize with the Gallery, as it is a public exhibit and not everyone knows how to operate a turntable. @Archimago made mention that he had a spare Shure cartridge at home and could have brought that. We then tried spinning Peter Gabriel’s Shock the Monkey, which confirmed another issue, the tube kit amplifier: Increasing the volume beyond a certain level simply increased the level of distortion, but not the volume, which was already too low level. KT66 output tubes is what I can remember. Arch and I were looking at the inputs to the amplifier thinking of plugging in our phones, as we both have large digital music libraries… who doesn’t these days. This is one of the themes of the exhibit re: the commercialization and commoditization of products and services in our world today. I had at the last moment decided not to pack my kit of cables and adaptors. It would not have made much difference as the tube amp needed servicing. Then the Art Gallery’s A/V person came in to rewind the Pioneer reel to reel tape deck: The reel to reel is playing a field recording of nature sounds that were captured at Peace River Valley in BC, Canada. The situation there is juxtaposed in the exhibit. In order to listen to records, one must turn off the nature sounds. Both Arch and I started a conversation with the A/V person. Yes, unfortunately, the needle for the record player was damaged again. And yes, the tubes in the amp need replacing and re-biasing. However, the A/V person had a solid state amplifier on the floor, as a plug-in replacement while the tube amp goes out for servicing. She asked us if we would like the amp swapped out now. Sure! Arch asked if she had adapter cables where we could plug our phones into the amp. Yes, please! We were excited, as we had a chance to experience the loudspeakers and the room: Listening Impressions How does one go about describing the sound quality heard at the exhibit? It’s hard to convey the “size” of the sound coming from the KleinHorns. It’s a wonderful blend of sound from the speaker drivers, the huge back loaded horns, and the acoustically treated room. Big and lively, not overly absorbent or “dead” sounding, but not colored either. Just a huge stereo image where you are fully immersed in the sound. As you will hear in the binaural recordings, the bass was smooth and articulate. Rather than me using fancy words to describe what I heard, why not experience the auditory scenes yourself by making a trip to the exhibit. If that isn’t possible, then try these binaural recordings. Binaural Recordings As mentioned at the beginning of the article, these binaural recordings are intended to be listened to with headphones. Ideally, use closed back or phones that seal well and isolate as much of the outside noise as possible. The idea is that you are hearing the auditory scene at the exhibit, which includes the sound from both the loudspeakers and the room. You are hearing what I heard, as if you were sitting in the listening chair in the picture above. Closing your eyes, sitting in your favorite chair, in a quiet environment, is the ideal way to experience this binaural acoustic event. The binaural mics I used have a measured flat frequency response down to 20 Hz, as verified in this article on measuring headphones. While I could have hauled my Lynx Hilo reference AD/DA converter and a stereo mic preamp, the point of the binaural recordings are simply to give a sampling of the acoustic event. Disclaimer: The binaural audio clips are not full song recordings and conform to the spirt of “fair use” for copyright material for the purpose of education and research. The author nor the publisher derives any financial benefit from these audio clips. The clips are in lossless FLAC and ALAC (Apple) formats recorded at 48 kHz sample rate. Don’t forget to turn up the volume a bit to hear both the speakers and the room, as the dynamic range is pretty good. From Arch’s collection, we listened to Daft Punk, Game of Love. Daft Punk binaural DR10.flac download (28 Meg) Daft Punk binaural DR10.m4a (Apple) download (28 Meg) I left the ambient noise in at the beginning of this clip so that one can hear the room. I was also adjusting the binaural mic in my right ear which is that rustling sound you will hear. Throughout the clip you will hear people talking and moving about, which gives a really good sense of the acoustic space. By the time the drums come in, you can hear the liveness of the room. The overall frequency balance sounds very good. Not too dark, not too bright, just right. The bass on the KleinHorns is tight and articulate. The high frequencies sound extended for a full range driver. One can hear it on the drum kit’s hi hat sounds and “s” sounds on the vocals. Next we listened to Giorgio By Moroder off Random Access Memories. Giorgio binaural DR14.flac download (28 Meg) Giorgio binaural DR14.m4a (Apple) download (28 Meg) What I really like is the spoken voice in the acoustic space. At about 1:50 into the clip, there is just Giorgio’s voice being reproduced over the speakers in the room. Really gives one a sense of being there. The bass sounds low and solid, the drums snap, and the voice natural sounding. Listen closely to the bass line as it moves up and down with each note sounding solid and even. Enya off the Lord of the Rings: Fellowship of the Rings soundtrack (“May It Be”). Enya binaural DR9.flac download (30 Meg) Enya binaural DR9.m4a (Apple) download (30 Meg) Get ready for goosebumps... At the very beginning of this clip, way off to the left and behind, is a door leading into a stairwell that you can hear being closed. Right after that, you can hear Archimago say, “Let’s try some Lord of the Rings” after he pressed play on his phone located where the gear is. Arch is saying this as he is walking back towards me to my left and up. Up because I am sitting in the chair and Arch is walking. This should give one a good sense of being in the acoustic space. What can I say? This is one of the reasons why folks build this type of speaker. It is an incredibly immersive audio experience. The Lowther drivers are known for their articulate vocal reproduction and one can certainly hear it on this clip. The big horns with their huge imaging makes Enya sound ethereal to say the least. Every nuance articulated with the room adding liveliness without coloring the sound. It’s a great example of Kevin’s DIY Audio and Excess Dispersion exhibits working together to produce a wonderful sonic experience. Epilogue If you’re in or around the Vancouver area this October (2018), come see and hear Kevin’s exhibition. As tapestryofsound says on diyAudio, “…right now possibly the only place in the world where someone can hear in a public place a unique and unforgettable sonic experience.” The two hours we spent at the Exhibit went fast. We were listening to Enya and were told that the Gallery was now closing. The Gallery is well run, everyone is approachable and friendly. Security let us know what we could touch, which was the DIY Audio exhibit, but not the Excess Dispersion diffuser panels. What does this have to do with computer audio? Computer audio is so ubiquitous that the public will rarely see or hear anything like this again. The KleinHorns and diffuser panels require significant time and effort to construct. They also require a fairly large space to operate in. Juxtapose that with plugging in headphones into a phone and having instant access to 40 million digital audio songs. While one is convenient, the audio visual experience is not the same. The resurgence of vinyl in recent years probably has more to do with a certain demographic that dislikes the overly compressed music being pumped out of their digital devices. Turntables, tonearms, cartridges and needles are not convenient and finicky. Tube amplifier kits require maintenance of tube replacement and periodic biasing. Again not convenient, but for some, offers unique sonic benefits that are unachievable any other way. Kudo’s to Kevin Schmidt: We are the Robots Exhibit. Not only an audio visual treat, but the underlying theme of the exhibit is thought provoking and happening right now. Don’t forget to bring your records! And as backup, your digital audio library on your phone ☺ Thanks Archimago for the great photos. It will be interesting to hear your take on our wonderful visit! Thanks Mike Lee from diyAudio for providing the front page and back wall diffuser panel photo’s. I wrote this book to provide the audio enthusiast with an easy-to-follow step-by-step guide for designing a custom digital filter that corrects the frequency and timing response of your loudspeakers in your listening environment, so that the music arriving at your ears matches as closely as possible to the content on the recording. Accurate Sound Reproduction using DSP. Click on Look Inside to review the table of contents and read the first few chapters for free. Mitch “Mitchco” Barnett. I love music and audio. I grew up with music around me, as my mom is a piano player (swing) and my dad was an audiophile (jazz). My hobby is building speakers, amps, preamps, etc., and I still DIY today. I mixed live sound for a variety of bands, which led to an opportunity to work full-time in a 24-track recording studio. Over 10 years, I recorded, mixed, and sometimes produced over 30 albums, plus numerous audio for video post productions, in several recording studios in Western Canada.
  14. Several near field monitors are active and typically already have digital XO's and if lucky, time aligned/linear phase operation. Genelec, HEDD, Adam, Neumann, PMC, Fostex, Amphion, are just a few brands that come to mind. JBL larger speakers like the M2 and Cinema speakers like I have require external XO and amps. So there is no passive XO network. For other speakers that say they are biamp-able, it usually is indeed still passing through the legs of a passive XO... One has to look really carefully as a "real" biamp scenario is where the amps connect directly to the drivers. I am a diyAudio guy and have built/modified speakers and have either unhooked the passive XO and ripped it right out, depending on whether reselling or not. That's another possibility... As soon as I get some time, I will start looking into this deeper...