Re: discussion between Drubin and Audioguy 123.
Sorry guys, I have to set a few things straight. Audioguy 123 is absolutely right that the TacT 2.0 does not comply with any of the existing standard techniques for speaker measurements. This is absolutely intentional. I will give you a bit of background information: Back in 1992 I bought a 50% stake in the high-end speaker company Snell Acoustics. Kevin Voecks, who is now head of REVEL - the Harman owned speaker company, was the chief engineer. At the time I was also the majority shareholder of NAD electronics. The president of NAD electronics was Marty Borish who had previously been president of AR speaker company. AR had a very bright engineer, Bob Berkowitz. Bob was probably the first person to realize that someday it would be possible to do room correction. Bob also made some of the first mathematical equations that would someday lead to the development of room correction systems.
During one of many meetings with Marty Boris I became intrigued by the idea of room correction, so when one day Kevin Voecks came to me with the idea that Snell Acoustics should cooperate with an engineering company to make a 6-channel room correction system, I was all for it. Kevin then worked with Sigtech for some time to develop a 6-channel version of their correction system. After a short time Kevin realized that the drawback of the Sigtech was the lack of correction resolution at low frequencies, which was – and still is – 20 Hz.
At this time my company in Scandinavia (AudioNord), the largest Hi-fi retail company in Europe, was the distributor of Audio Alchemy, the company owned by Mark Shifter. Knowing that AA was capable of making very nice digital electronics I connected Kevin Voecks and AA/Mark Shifter and subsequently (Autumn 1992) Snell entered a development agreement with AA to design a room correction system.
Mark Shifter announced in “Stereo Review” in April 1993 that Audio Alchemy/Snell Acoustics would have the correction system available “this spring”. However, after working on the project with AA for one year it became apparent the AA was not able to make a workable solution and Kevin gave up the project with AA.
Then in the autumn of 1993 Kevin met Dr. Radomir Bozovic (Boz) at the AES convention in New York. Boz was showing his DSP engines which were capable of astounding performance - far beyond anything Kevin had experienced. In November 1993 a development contract was signed between Snell and Boz and within a few months Boz had designed a correction system that in Kevin’s opinion was far superior to anything on the market. The product was later sold as the Snell RCS 1000 at a retail price of $18,000.
In 1997 I had bought all of the shares of Snell Acoustics and become the sole owner. In 1997 Kevin was headhunted to Harman International to start up the Revel speaker company. Harman also tried to hire Boz, but Boz and I decided it was better for us to use the technology in NAD Electronics, which was still controlled by me. I found another excellent engineer – Dave Smith to head the development of speakers at Snell Acoustics and sold the company to my good friends at Boston Acoustics. Boz and I continued to work together developing products that were intended to be sold as NAD products. However, in 1998 Boz and I decided to start a new company owned 50/50 with the purpose of developing the world's best sounding audio products. I had become so involved and enthusiastic about this new venture that I decided to sell NAD to some of my other friends at Lenbrook industries in Canada. (Selling NAD actually hurt a lot. I had been closely involved with the company since 1978 and very involved with product development. NAD have consistently made products that just sound so much better than almost any products in the price category. ) .
The room correction system is now in the fourth generation since the first system designed for Snell. The unique combination of talent at TacT Audio has catapulted the company to become the most successful start-up in the high-end arena.
In the daily development of the room correction systems, Boz is responsible for all the advanced mathematics and DSP code. With regards to resolution, distortion etc. there is no match for the systems designed by TacT audio. When it comes to listening tests, etc., I am the person responsible for that department. My office and listening rooms are in Denmark. Denmark with a population of 5 million educates more specialized acoustical engineers than the USA, so it is no coincidence that Denmark has some of the best speaker driver manufacturers in the world: Vifa, Peerless, Scanspeak, Dynaudio, Dali and Audiotechnology, and the most famous manufacturer of acoustical measurement equipment and microphones: B&K. I know the engineers and/or owners of all of these companies, so any questions regarding measurement techniques etc. have been bounced on a number of the best brains in the industry. The engineer that developed the first B&K microphone worked as a consultant for me for 5 years, and he is still a good friend. For good measure, I own the very successful speaker factory, DALI with some of the best acoustical engineers in Denmark.
What I am trying to say in not so few words is: Boz and I did not just stumble over a few lines of code and decide to make a correction system.
One of the things that were discovered very early on when Boz and Kevin started to work on the correction system (before I got so heavily involved) was that none of the standard measurement methods were useable for correction. A big part of the development has been concentrated around making measurements that are consistent with what we actually hear and at the same time do not lead to side-effects.
When you want to measure the perceived frequency response, you can’t treat all frequencies equally with regards to filtering, gating and smoothing. Also, you have to take into account the wavelength versus correction resolution, the way the sound decays at different frequencies etc., etc.
It is a mistake to have flat frequency response as your target, unless you live in an anechoic chamber. To get a natural sound you need to adjust the target curve in a way that mimics the response you would be getting in an average listening without any specific resonances, cancellations etc. In other words it could be the average response of a thousand different good rooms. To put it in simple terms, you do not want to get the frequency response you would get in an anechoic chamber, but the response you would get in a real listening environment without any specific resonances etc. The target curves suggested by TacT are meant as a starting point for correction. “TacTA1” Is the most universally accepted for large speaker systems with good bass extension. This curve has an increase of around 6 dB in the lower bas region – to mimic the room gain at low frequencies and a gradual roll-off at higher frequencies to mimic the higher absorption of higher frequencies in listening rooms.
The curve can be modified very easily with a drag and drop tool where you can directly compare your loudspeakers' response with the target curve in the target curve editor. (The measurements brought into the target curve editor are the calibrated – and thereby accurate – measurements. The measurements on the main screen are for quick view only.)
If you wish to maintain the general character of your speaker system you can tailor the target curve to follow the general tendency of the speaker itself.
It is absolutely a false claim by Audioguy 123 that the 2.0 does not follow the target curve. Any change in the target curve will result in a corresponding change in the acoustical result accurate to within 0.2 dB. It is true that it does not follow conventional measurement techniques – and that is absolutely intentional - and essential to the success of the product.
Peter Lyngdorf, TacT Audio
