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Hello everyone! This is Takimoto from Hi-Fi Do Kyoto Repair Department. I cannot count how many times have I said "hot!" this summer but I just said another one. It seems I will add some more event it is already September. These days I feel the climate is changing from what I am already used to.

The other day, a similar feeling happened while repairing a pair of speakers. It was not about my sense of seasons. It was about something else same kind of feeling.
One of important procedures of repair at Hi-Fi Do is the final check after every components are repaired and reassembled. On that day, it was a pair of JBL L101 Lancer. We were going through sound check.
	JBL L101 Lancer is stereo two way floor speakers. The look is very classic and reminds me of good old days with marble top boards and lattice grills.

This model consists of woofers LE14A, tweeters LE175DLH, and net work LX10. The sound is seductive and mellow, which people say sounds great with jazz records. The size is not too big and it isn't hard to match other interiors. We sell a lot of these.

Left) LE14A Right) LE175DLH
LX10
You can see some images HERE from our archive as well.
Anyways, I was checking the speakers with test CD including sound pressures, sound field, and frequency sweep. It was the time I felt something was different. It was not something that I was used to. "The sound spreads out unusually…?" It is due to wiring and repair procedure, we first use radio as a source before CD. After radio, Pablo de Sarasate's Zigeunerweisen (Violin) for stereo channel check follows. At the point of the two steps I was already slightly sensing incongruity. At the third stage, sound stage check, the difference was obvious. Treble was sounding from somewhere deeper and higher.
	For your reference, currently we use Denon Audio Check CD regularly. That made me automatically sound-check whenever I hear Zigeunerweisen or Rakhmaninov’s Liebesfreud (Kreisler).
Now we figured out what "something wrong" was. But there appeared another problem. Sadly, it is my lack of experience. I was not able to tell if it was the sound the speakers were supposed to produce or not. They was not sounding wrong as legitimate speakers. Some might say the sound got more expanse. The problem was that I couldn't judge. While keeping up with daily tasks, a trainee like me learn characteristics of speakers through sound checks. By repeating that, our ears eventually learn how each speaker sounds.
	For example, you will gain your own thoughts on each brand like: "Eeach JBL speaker has strong individuality while there is similar vividness in sound image." "This softness in sound is very Tannoy-like." or "It is comforting to hear very average and balanced sound of monitors even there is no clear characters".

Sometimes I miss valuable opportunities to listen to rare speakers if I was taking care of other units or am off. In such case, I need to wait until the next chance when Hi-Fi Do encounters the speakers. About the L101, it had been about one year ago that I listened to the pair the last time. And it was the only opportunity I have ever had. My image on L101 was far from establishment at that point. However, even based on my poor experience, after asking myself if it was really a natural and comfortable sound if the model, my answer was NO. One thing I need to make clear is that all the equipments are repaired under the supervision of experienced engineers at Hi-Fi Do. We all usually consult them in case we face such issues. This time, they let me go on by myself for better learning.
In such cases, we usually check wiring mistake of positive/negative electrode. But this time was not the case and I had an idea, which was wiring of LC10.

For models we are not familiar with, especially for a trainee like me, we sometimes consult the state of the same components we have or our customers have us repair. Networks of JBL LX series adopts numbers instead of positive/negative signs as you can see in the picture above. This time, I followed wiring of a LX10 we had as a stock. But I had a feeling that it was not something I had in my mind from my past experiences. So it was the point that I doubted first. After changing the wiring, all the incongruity was gone and now everything sounds right and clean. Compared to this, I could tell that it was wrong, the sound I began with. The corrected sound had seductiveness and mellowness with perfectly adjustment of dry & clear treble and bass. Now I could overwrite my impression of L101 with a right one.
To me, it was very interesting to realize once again that phase could change the entire impression of sound. However, at the same time, I find it very dangerous that I could still easily be lost because of prejudice and lack of confidence. One thing I learned was to be royal to basis. I double checked with JBL's manual in the end. Just like the saying, this case told me "haste makes waste".

For your reference, above is the chart from the manual I used this time. JBL systemizes the combinations to optimize sounds with their products if you just follow. As well as the wiring, one thing that is very complicating is that there are some changes in orders of connections depending on which era the networks are produced. This time, it is too much to explain here and I am not experienced enough to do so. I might be able to do that here someday. I now must ask you to wait until then if you are interested.
LX10

LX5


I will do my best to establish my sense of speaker sounds even that of season will keep drifting away... Until next time.

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