20 years of room correction

Description of your audio system, your target and... how you have reached it
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Hans-Martin
Posts: 3
Joined: 20 Oct 2019 18:00

20 years of room correction

Post by Hans-Martin » 21 Oct 2019 14:39

Hello brotherhood of sonic quality addicted!
My first stereo was 1969 a BSR turntable with a ceramic cartridge. It allowed splitting the channels and my tube-based Telefunken mono r2r recorder and the kitchen radio did the replay (IACC???). Led Zeppelin II was the first record I heard in my room in stereo, that was an amazing experience! A Telefunken M204 replaced the vintage M75 and 2 fullrange Monacor SP50X speakers supported it, Perpetuum Ebner went bankrupt and I got a new turntable with Pickering magnetic cartridge for little money. A B&O SP6 cartridge and made a remarkable difference and this was the beginning auf audiophilia nervosia...
Educated as a radar technician at the airforce I did numerous nightshifts where we were quite free to use Hewlett Packard, Tektronix and Rohde&Schwarz measurement equipment for our own projects so I built my own amplifiers and speakers. ReVox A77 came into my equipment and set new standards.
As a student I organized a group DIY project, a reverence to Bose 901. I got a pair of Ionofane 601 plasma tweeter (like DuKane) and my first contact with measurement microphones at the local physics institute. An ERA turntable with SME3009 and Shure cartridge made the next major step (it was designed by Verdier...), it was a dirt cheap bundle sold in London, I could not resist buying it. It was replaced by a Technics SL110 /SME and this was the first time when I made a progress that turned out to be a step back actually. I spent much time in speaker DIY, horns, transmission line that later acted as corner-placed (sub)woofers for my Magnepan MG1 that were driven by 2 stereo transistor amps and 2 tube amps, a Pioneer D23 active crossover was a good step ahead.
The influence of a 10 band equalizer was no progress, it destroyed the depth of the soundstage, even a real time analyzer Rotel RY 1010 could not help much to bring me close to something fully satisfying.
At the Frankfurt HighEnd show I was fascinated by the TacT Millennium that could open the space way deeper that any amp I had experienced before. I still own one.
Then Digital Room Correction came into play and I had the opportunity to test TacT RCS2.2
First attempt to make a linear response led to a sonic desaster. Soon I found that the linear target curve is not what should be expected at the listening position. TacT RCS2.0 was released and it became the center of my interest.
Uli and I are of same age and we knew each other from at least 2 internet forums. When RCS2.2X was new, we found the same bugs, and Uli programmed some workarounds. Later his GoodVibration software made good improvement with the TacT and I brought in some ideas like excluding a defined range from being corrected (by converting measurement curve into target curve, I proposed that to Peter Lyngdorf in 2001).
I visited Ulis home and could see how his system changed by creating Acourate. We had different taste and I preferred a target curve tilted down 1dB more to feel happy.
After 20 years living with RoomCorrectionSystems (TacT and Acourate) I conclude that it is the most powerful tool if one knows how to use it. Wrong beliefs may lead to absurd results, I have attended several shows over the last 10 years and many companies still present their products in a way that the experienced user can easily say what beginner-mistakes have been done there.
Still I believe there is more than a good correction.
One easily finds poor recordings, the sweetest spot is the sweet spot in the room with RoomCorrection applied on it, the equilateral stereo triangle is often regarded as a paradigma, I rather say strict symmetry in every respect is the basic idea, etc.
I walk the stereo axis and find the sweet spot in the room modes, then I shift the speakers to complement the listening position. Then I apply the correction (on my 2.2 system with TacT W210 corner woofers and currently 2 coaxial units on open baffles, >95dB/w/m).
I still use my Squeezebox powered from a laboratory regulated power supply if the battery is low, it is clocked by a battery-driven LC-Audio clock or from one of my Millenniums (this clock-link allows to skip the input receiver for 44.1kHz data only), other sample rates are reclocked by Mutec MC-3+. Clocks and reclockers float on nylon strings for decoupling from surface vibration. Even batteries are sensitive to vibration...
All my cables are handmade and have my very own design, my audio interconnects have lesss than 12pF/m, my digital cables look like like sewing thread and speaker cables are woven from antiparallel wires with teflon sheath. The mains cable is a bunch of PTFE insulated dense stranded wire, the wires are grouped for every unit, but close to the rack all Neutral meet, all Live meet and all safety earth meet to create a star-supply. I use brass contacts with a high copper component (I dont like Rhodium here). There are wire fuses wherever possible, to avoid the complex structure of magnetic cable protectors.

What to do about poor recordings? This question is an open problem.
Playing with bass and treble control in the 1970ies was not satisfying, same with 10band EQ, one would not change it with a new recording every time it is played. Recording on harddsic is still my favourite method. I learned that replay of LPs add a diffusion (the crosstalk between L<>R is mainly antiphase), while from digital source the treble sticks to the tweeter because most of the recordings lack time information in bass required for good localization. In a UK HiFi-mag I found the Francinstien and phoned Richard Brice. He sent me a sample and I applied it with the impression that this could not be the whole story. Setting up speakers for best localization in stereo would lead to less treble than when listening to mono single speaker.
So I found a way to manipulate the stereo separation (Adobe Audition 3.0) to make treble meet bass, more separation in bass and less in treble. It gives the music its authenticity back to make a more credible replay. A postmastering method.
And then the absolute polarity comes into play, many recordings are simply inverted (I believe this has historic reasons, back in the mono time a fullrange speaker would create a more diffuse sound if the signal was inverted. With correct (authentic) polarity the single speaker can easily be located in a blind audition. What worked well in mono times became counterproductive in stereo, and if one goes for a high IACC one should check absolute polarity with every CD. No worry, one learns over the years the name of the companies with inverted music, there are very rare exceptions if one lists the traditional companies. Modern studios can be reliably correct, but there are exceptions like Bernie Grundman remastering Jennifer Warnes The Hunter album, the first release (mastered at Bernie Grundman) was correct, the remaster was inverted...
Once corrected by any WAV-editor software I have only playable versions on my harddisc. And If I find too hot treble I first apply the channel separation thingie. The result convinced Uli and he created Acourate FLOW :-:
If treble is not to my liking I can still apply EQ and store the result. Some old recordings really can benefit a lot from that.
So I spend my time with replacing DIY speakers and with modding music...
It can be very satisfying to experience the difference.
So this is a long story of a long life in listening with a number of improvements that turned out as mistakes.
I am still looking for something better... can somebody please stop music industry from applying so much compression ?
Cheers
Hans-Martin
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