As a result of that breakdown, there were three essential elements which became clear to us.

The first of these is that the sound produced by the artist must be accurately reproduced, just as it was originally expressed. An important function of a stage monitor is making it possible to check for yourself how things like the smallest differences in singing, including breathing and the faintest vocals, are conveyed to the audience. The same is true for instruments like the guitar and bass.

The second element is the ability to properly ascertain the balance between the instruments. It’s important that the sound of the vocals and instruments on stage stand out and can be heard distinctly. Obviously, if these are all mixed up you can’t play your part. A stage monitor must accurately express the sound and emotion intended by the artist.

You said “incorporated more than three BA units”, exactly how many BA units are there in these models?

Kuwahara:
There are five BA units in the IER-M9 and four in the IER-M7. And the main ranges handled by each of the BAs are also separated. This means that the IER-M9 is a 5BA-5WAY system and the IER-M7 is a 4BA-4WAY system. We actually tried making versions with more than six, but upon testing we found that more isn’t always better. To achieve the desired sound, we feel that, at the moment, a 5BA-5WAY set up is best. Furthermore, for the miniaturised BA, in addition to developing a new woofer and full range system, we are also developing a super tweeter.

Were there any other issues that caused you trouble when assembling the multi-BA system?

Tobise:
It wasn’t just the pattern with which the BA units were put together. Including the shape of the acoustic paths for mixing the sound from each BA and tweaking the network circuits to split up the frequencies, there were a countless number of adjustment patterns possible. Trying all of these was truly a slow and difficult process.

Kuwahara:
The middle range for these models is split mainly between two full range BA units. One assists the woofer, increasing the groove, while the other works in conjunction with the tweeter to put out clean high-frequency audio. That direction was visible to us from early on in the process, but in the end, we were able to far exceed the audio quality we had imagined at the start. What made that a reality was the network circuitry that Tobise worked so hard on. By completely rethinking the design concept, he succeeded in improving the connection between each BA. We can proudly say that this is quality which goes far beyond our greatest expectations.

What sort of sound does an artist want from their stage monitor?

Ohmura:
For example, it’s important for a vocalist to have such things as the tone and speed of their voice reproduced authentically. Of course, I think that sort of basic feature was mostly realised as early as the prototype stage. However, the reproduction of the heavy and low sounds of the bass drum that are so important to drummers was a bit weak, so I requested that they do more in that regard. With small in-ear monitors, it's typically not possible to reproduce the type of heavy, low sound that makes the air move, but I told them that I wanted to be able to feel that.

Kuwahara:
That was something we were surprised by. We were thinking that if you just want to hear your own voice or the attack of the bass drum, it was fine to have the low frequencies subdued. We were under the impression that we were putting out more than enough, but he said that for the musicians to perform, that still wasn’t enough. That’s the biggest change from the prototype. We learned that to give a good performance on stage, the reproduction of heavy and low frequencies is important.

Was that advice reflected in the final product?

Ohmura:
Yes. Yes. I just tried listening to audio using the final version, and I can say I could definitely feel the air move. (laughs)

For example, just like the sound directed toward the audience, the sound that is broadcast to the vocalist’s stage monitor is usually a mix of all the instrumentation. The ability to make adjustments so that a well-balanced reproduction of that sound can be listened to is one of the main characteristics of a stage monitor. So, while it is a monitor, it can also be used for listening, killing two birds with one stone as it were.

Tobise:
This was a new challenge for Sony, and in carefully searching for direction in creating the sound, we discovered that the final product had a balance that was suitable for everyday listening. The sound of the instruments is accurate, as are the rhythm and balance, and on top of that we think it’s a product that plays audio in a way that’s exciting to listen to.

Please tell us the differences between the IER-M9 and IER-M7.

Tobise:
The IER-M9 has an additional tweeter for smoother and more refined reproduction of high frequencies, allowing the fine nuances of the timbre to be expressed. Because we put a lot of our focus onto reproducing sounds like the linger of cymbals and high hats, and the breathing of the artist, it would be the IER-M9 that I would recommend to anyone who wants that level of exacting reproduction. Of course, the IER-M7 also feature all the important parts so I believe you should be just as satisfied with a pair of them as well. We think that those who regard the mid-range frequencies, particularly the vocals, to be especially important will find them to their liking.

What level of music player or audio source are you imagining this will be connected to?

Kuwahara:
Try it first with your normally preferred music player, even if it’s a smartphone. After that, if you have the budget, try a Walkman® that supports balanced connections (NW-ZX300, NW-WM1A, and NW-WM1Z) to enjoy the pure acoustics of a balanced connection. I would also recommend using the highest quality audio source available. High quality headphones are able to properly express differences in source quality, so I think it would be fun to listen and compare.