Hand crafted SP with ONKYO "OM-OF101" vol.4 - Assembly completion and evaluation

The summer heat has subsided and the mornings and evenings are becoming more pleasant.



Get the faston terminals, and the speaker box for the OM-OF101 is complete!


The size image of the box looks like this. The magazine is B5 size.


I installed the SP unit in the completed box and played music at a low volume to check the connections.


Polarity is OK with no unusual noises. First, I measured the frequency response of the left and right channels.


I used the "Audio Frequency Analyzer" to measure the frequency response of the pink noise playback, 1/3 octave band, after matching the level with a 1kHz sine wave.

- frequency response L-ch (Initial)

- frequency response R-ch (Initial)

It is wonderfully flat.

There is no extreme difference between the left and right channels in the low frequency range, so the SP box assembly seems to be fine. The low frequency levels at 63/80Hz are the same, so the duct tuning seems to be good.

Anyway, I listened to some songs in this state.
Instrumental music, female vocals, orchestra, quartet,... I could feel the rhythm of the bass well enough. And the separation of the instruments was sufficient, and the sense of localization was fine.

However, I felt that the sound was lacking something. The vocals did not come forward. I wonder if this is a matter of personal preference...

So I tried reducing the sound absorbing material a little.

- frequency response (reducing the sound absorbing material)

As a result, the 63Hz level dropped a little. The overall impression was the same, although I felt that the volume of the bass might have been reduced in the auditory sense as well.

At this time, the distance between the left and right speakers was about 130cm, which was a little too wide for a 10cm unit.

I narrowed the distance to 90cm and listened again. I felt that the vocals became a little clearer.

So, I measured again for confirmation.


- frequency response (On the axis 100cm, 0 degree)

I measured again at a different angle, 1m above the axis. I attached a 1m long string to the tripod leg and moved it to a 30 degree position.

By using "ClinoScope", I found the angle in one shot just by turning the iPhone.


The frequency response at 30 degrees showed a gentle drop in the frequency range higher than 5 kHz.

- frequency response (On the axis 100cm, 30 degrees)

The reason for the unsatisfying sound may be the high frequency characteristics, or may be a matter of the sound directivity when the space between the speakers is too wide.

I tried to measure the 60-degree response as well, but the sofa was in the way. I had no choice but to measure at 45 degrees for reference.

- frequency response (On the axis 100cm, 45 degrees)

As for this unit design, I felt that the emphasis would be on the low-mid range.

It reproduced enough bass feeling even with a simple bass reflex, and almost no unpleasant sound came out. I would have liked a little more sharpness, but that's a matter of personal preference.

As mentioned in the article on box construction in the magazine, this may be the reason why a box with moderate resonance may be more suitable.

The fact that it is not flavored with a specific frequency range means that it is a seriously designed unit.

It will be interesting to use it as a midrange speaker unit in a 3-way system.

As a future plan, I'm thinking of putting a tweeter on it.
posted by toons at 05:52 | Audio