As Gaudi is a multi-amplifier system, the level of each band has to be
adjusted. You may think it's an easy task only to turn the knobs. In fact
it is very difficult.
There are several ways to adjust the multi-amp system. To make a long story short, the best way is adjusting little by little while listening to various kinds of sounds of various kinds of music and sensing frequency balance. I played many records and CDs that I am familiar with one and all. It takes a month or two one thing and another.
I have been using live recordings recently in order to improve efficiency. That is, I record voices of my family members and friends and performance of musical instruments, and play the recordings for adjustment. I can adjust more quickly since I know the original sounds. I use headphones when I am at a loss. (equipment: microphone: Audio Technica AT822, recorder: TASCAM DR-1, headphones: Audio Technica ATH-PRO700)
It is the worst method to adjust the level so that frequency response should be flat by reading a meter that indicates SPL measured by a microphone and an oscillator connected to Gaudi, although it seems to be scientific and most appropriate. Once I tried this method, sensory frequency balance was not flattened out. The tone became weird; the midrange sounded so loud and the woofer was so quiet as if it had been broken. (instruments: oscillator: KENWOOD AG-203D, microphone: Audio Technica AT822, recorder (meter): TASCAM DR-1)
Just after I finished adjustment by this method, a friend of mine came and visited me. I let him listened to Gaudi. He criticized severely, saying bass was not heard at all and localization of sound was unstable, etc.
（2012/12/04） ｛After upgrading the midrange of the loudspeaker SS-309 to horn-loaded drivers (Fostex D1405+H400), I feel physically flat response sounds really flat. Now it is effective to adjust the levels with a VU meter. Tuning of Gaudi, which used to be troublesome task, is not so now, although numerous listening tests are still necessary for fine tuning. It takes one week or so to tune Gaudi.
I measured frequency response again after the fine tuning, and found the level of midrange is a bit lower than the other drivers. If the response is flat, the sound of Gaudi is too aggressive. The lower level of midrange makes the sound milder. This may be caused by low compatibility of the amp DAD-M100pro and the driver D1405, and lack of aging of the driver.
The figure below is the frequency response of Gaudi as of December 4, 2012. The microphone was placed at the listening position. Gaudi played a CD that contain various frequencies of sine wave. I recorded them by using DR-1. I read VU values displayed by a sound editing application, SoundEngine. I input the readings in an Excel spreadsheet and made the figure.
The curves have many peaks and dips, especially that of the left channel. Now I know the room acoustics is not good. I should spend more time and labor for improving the room acoustics than for improving the amps and speakers｝
Geometry of drivers of SS-309 (especially on-axis position) is adjustable, because it is a multi-enclosure system. The fc (crossover frequency) between the woofer and midrange is 720Hz and the wave length at the frequency is about 47cm, so there is no need of fine adjustment of the geometry of the woofer and midrange. The midrange baffle should be flush with the woofer baffle to make the looks good.
The fc between the midrange and tweeter is 7200Hz and the wave length is as short as 4.7cm, so it is necessary to adjust the position of the tweeter accurately so that phases are matched at fc. I adjust it listening to music so that stereo field becomes the widest and sound image the clearest.
（2012/12/04） ｛Now I have to adjust the position of each driver from start, because I changed the midrange drivers to horn-loaded type. I haven't found the best geometry yet.
The lower fc has been changed to 800Hz｝
Let me list up disks I often use for adjustment as follows. Most of them are vinyl records. As for SACD, I recommend ones the source of which is DSD recording. I seldom use CDs.
The concrete steps of adjustment are as follows:
It is very important to adjust channel balance of each driver. If this adjustment is skipped, sound images become blur. If channel balance is fine, sound images become sharper and localization becomes more accurate than single driver speaker systems.
（2012/12/06） ｛I found out that the perfect channel balance deteriorates the sound quality. The room in which Gaudi is installed is not symmetrical. The left hand side wall reflects sounds more than the right hand side. Localization of sound tends to be shifted to left. The level of the left channel must be turned down by 5-6dB, in order to localize a monaural sound source to the midpoint of the loudspeakers. If it is done, however, a sound image becomes blurred. I believe adjustment of more than 3dB causes this problem.
Currently, I adjusted the channel balance so that the sound image is shifted left by small degree as shown in the figure below. The stereo sound field is kept wide, because the left most sound is heard from left of the left hand side speaker. The whole sound field is shifted to left a little bit.｝
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