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 understanding distortion

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Michael Green
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PostSubject: understanding distortion   Sat Jun 02, 2012 5:35 pm

Do you understand distortion?

The meaning of distortion is the adding to or taking away from a source, wave or signal. If this is true than amplification can be distortion.

Let me help you a little with this term so you know how to use it with your system.

Distortion in the reproduction sense is when the signal is "out of tune from the original".

What is one of the signs of system distortion?

One of the biggest problems in high end audio is the issue of real size and real space. In reality our systems should be able to reproduce the same size signal as the signal that is recorded.

In 2003 we put this to the test on Music Row. On one side of the building we had the recording studio and on the other the listening room. The goal was to see how close we could come to a real size real space playback system. Having access to tons of audio gear made the job interesting as we could then see if the equipment was faithful to the signal. Several of Nashville's engineers were in on the playing and testing. We did two versions of these test. One was a plug and play setup where we would take the equipment in and out of the audio chain. The other was a more tweaky version of the same test.

On the studio side of things we made measurements of the rooms used in the recording. All instruments were acoustical and we used micing techniques commonly use when picking up a bigger or appropriate space. We used 3 iso-booths that were different sizes so we could see how they fit into the sound stage, and 2 main rooms for bigger effects. In the main room we used an omni-directional mic to pick up the overall space. The mic was placed in the middle of the room.

On the playback side of things we used a 14.5' X 17.3'X 8' room with basic treatment. The starting system was done with no chassis and free resonant speakers. Cables were solid core with minimal jackets. Power was hooked up directly to the fuse box. We tuned the starting system so it would play back the same size space as the studios space.

The first thing that we found interesting was how the speakers that were lighter in weight full range monitors (weighing 7lbs) had the biggest sound stage. The heavier monitors created a very pin point but small stage, as if you shrunk down the size of the space and instruments. This stayed consistent through the testing. The heavier the speaker in relationship to mass vs size were consistently casting the smaller sound stages and never were able to break past the side walls of the room or cast an image behind the listener. For the what we ended up calling over massed speakers we decided to give them a much bigger room to play in. This told us from the speaker end of things that speakers are very dependant on size of room the more mass you add to them. The heaviest/mass speakers completely collapsed in the sound stage in the 14X17 room. Even the 23X28 room had a hard time accommodating the bigger speakers, so this disqualified a few of the models from making it to the testing. it was surprising to us how few of the speakers were able to cast a sound stage that went past the edge of the speakers. Again the lower mass speakers could play music beyond the sides of the room but the speakers that used MDF and rubber had a very hard time with placement and getting the music out of the speakers. There were only 4 speakers out of the 27 tested besides our own brand that were able to cast sound stages bigger than 11'X6'X8' in the room. This was a little alarming since the size of the main recording room was 24X36X15. At this point as a little detour I modified the speaker that did the best job of size besides the free resonant ones. I simply removed 2/3 of the internal poly fill and took off the rubber grommets used to hold on the grill. Then I took out the air seal gasket and loosened the driver screws. Finally I removed the glue that was dampening the crossover. Not only did the speakers open up sonically but the size of the stage grew to going past the outside of the room on the sides and front of the room. Instruments became more believable and much closer to their real size and tonality, less plastic and dampened sounding. Even though the sound of these did not approach the full blown free resonant speakers in tonality and spaciousness it started to let us know the dampened speakers distort by removing much of the music from the signal which in turn causes the stage to shrink. The set free speaker was also much more in tune where as the dampened ones made the instruments sound like they were out of tune with each other.

Once we got past the speakers basic testing we moved to the electronics. We were in shock to find the heavy very expensive electronics that are on the A list jump right into the speaker. The heavily damped electronics were extremely fussy and did not let you hook them up to the rest of the audio chain without completely collapsing the sound stage and sending the image right into the speakers or grouped in the center of the room. It took days to setup up the heavy electronics and was almost always a tweaking battle. There were dark circles around the instruments and you got no sense of real studio space the way the non-chassis components gave. I had Mike from Warner Brothers listening with me and he was in shock. He described the sound stage as artificial and cloud covered. It was like removing yourself from the music altogether and creating a new definition for each instrument. There were hallow spots and spaces between the instruments that were never in the recording or recording room. Much of the high end audio equipment sounded like they made their own version of what was there and packaged it into a small room. With much of this gear the music went from real in the studio to small and syrupy in the listening room. When these components were opened up they were full of dampening materials and heavy sub chassis and parts. Rubber and glue were all over the place. These components never did give the true sound of the instruments no matter what we did. Again the more light weight simple designs blew away the bigger products in the real space and real sound department. The one main problem though with the lighter weight products was the cheaply built chassis that were begging to be removed. When doing so they opened up huge and delivered a very close to real life sound that the over built components never did. Even when most of the over built products had their mass removed there was something weird sounding about the circuit design itself. Almost as if the dampening was intentional to give these dark closed in sounds. Some of the lighter weight high end gear with their chassis removed sounded good but surprisingly we all found the mass produced products that had extremely light weight parts to be the most musical once the chassis, rubber and tight screws were removed. People who we brought in off the street to listen all chose the what is considered by audiophiles to be midfi over the high end products. There was no question that the light weight gear was far more open and musical when compared to the real sound of the in studio sound.

As our tests continued to the rest of the audio chain the results were the same. For example interconnect and speaker wire reacted the same way with the heavier more mass cables seeming to close things in while the lighter weight cables opened things up.

In the 14X17X8 room we were able to reproduce a fairly close replica of the studio, but it was not able to be done by the limited over built products. We were able to do fairly well with several components and speaker setups once we found the formula that worked. Did this system look anything like an audio system? I would guess that would have to be in the eyes of the beholder, but we did prove that real space and real sound is a reality on several levels.

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