Goodbye, ONKYO!


Yesterday, ONKYO Home Entertainment went bankrupt. It is very unfortunate.

ONKYO is a famous Japanese audio manufacturer founded in 1946. The ONKYO brand will be deeply remembered by us audiophiles as a manufacturer that made a great contribution to the world of pure audio.

Thank you for all these years, ONKYO!
posted by toons at 21:47 | Audio


Replaced the insulator of YAMAHA analog record player GT-2000L.


Yamaha Analog Record Player GT-2000L.

This is a great piece of audio equipment in the golden age of audio that I continue to use with great care.

The weight of GT-2000L is quite heavy, about 28kg, and the genuine insulator was screaming under the weight of years of use.

The genuine insulators were made of rubber and spring composite structure, and they were strong enough to withstand more than 12kg of weight per insulator, even if they were replaced with 18kg gunmetal turntable "YGT-1".

Now, it's in such a mess!


Two of the four insulators were damaged, especially one where the rubber adhesive had completely peeled off and the enclosed spring had popped out.


YAMAHA didn't have any spare parts in stock, which is not surprising since the product was almost 40 years old.

I've been looking for it on the Internet auctions, but I couldn't find any genuine insulators, so I had no choice but to use other insulators.

Last year, I found interesting parts among all the junk, such as audio cables and radios, in an item called "Audio Junk Set" on online auction.

I decided to bid on it at a very low price, and when I checked what I received...


This was a set of four genuine insulators for GT-2000. This was truly a grab bag!

They were in very good condition with very little apparent deterioration, and had probably been installed in GT-2000 for a short period of time.


After disinfecting and cleaning with alcohol, it caused a blooming phenomenon of the rubber. So I applied a little bit of KURE rubber protectant, and it returned to its original black tint.


As a test, I tried to find out how much difference there was in the degree of shock absorption between the old insulator and the new insulator.
I put my iPhone SE2 on the turntable and used the vibration analysis app "Vibroscope" to measure the difference.

- Measurement result of vibration absorption at OLD insulator

- Measurement result of vibration absorption at NEW insulator

This measurement was made when the GT-2000L was placed on the YAMAHA GT-rack "GTR-1W" and the rack shelf was hit hard by hand intermittently. The results show that the new insulator dampens external vibrations better than the old one. I tried to apply the same force as much as possible, but it is difficult to apply exactly the same kind of vibration, so this was just for reference.

Now I can enjoy original sound of the GT-2000L for the first time in over a decade. I'm sure it will be fine for another 10 years or so.
posted by toons at 23:49 | Audio


Paco de Lucía


Today was the birthday of the great guitarist Paco de Lucía (Birth of December 21, 1947).

A genius who transcended the boundaries of flamenco and opened up new horizons in guitar music.

Whenever he came to Japan, I went to listen to his live concerts.

Speaking of live concerts, the super guitar trio with John McLaughlin and Al DiMeola in "Friday Night in San Francisco - Live" (1981) is famous, but I would like to mention "Live Under the Sky" (July 25, 1981, Denen Coliseum, Tokyo). I was particularly impressed by his performance with Chick Corea at this live. It was an unprecedented outdoor live performance in heavy rain.

When I received the sad news that he passed away on February 25, 2014 during a live tour in Mexico, I cried at his loss.

In his later years, he was playing guitar with the superb technique like his younger days, but I had admired his ever-evolving attitude and musicality.

The album entitled "Fuente y caudal" (1973) was the starting point of Paco's music for me. It was the beginning of Paco's creation of new music in the tradition of flamenco. If you have a chance, please listen to it.
posted by toons at 23:57 | Audio


Today is "The Day of Sound".

Thomas Edison invented the "Phonograph" on December 6, 1877. In other words, it can be said to be the birthday of audio.

When I traveled to Kanazawa city a decade ago, I had a chance to listen to various types of phonographs at the Kanazawa Gramophone Museum.

The one I remember well is the "Victrola Credenza", which was commercialized in 1925 and was called the "King of Gramophones". It was the pinnacle of mechanical phonographs. At that time, the price was enough to buy a whole house.

I had listened to many inexpensive SP gramophones before, but this Victrola Credenza surprised me with its special sound.

Even though it was a 78 rpm SP record played mechanically with no electric amplification and only horn speakers (a compactly folded 180 cm long horn), the sound was so deep and delicate that it was hard to believe it was monaural, and the sense of presence was especially wonderful. Moreover, the playback volume (dynamic range) was sufficient even for a small hall.

It is true that the reproduction frequency range is narrow, but it must have been exquisitely tuned by knowing the sweet spot of human hearing. It might be better to call it an musical instrument.

It was an experience that made me realize once again that 100 years ago, the technology for faithfully recording and reproducing music had reached its peak. Since then, I have come to respect SP record enthusiasts (for their good feeling and good ears).
posted by toons at 22:55 | Audio


Hand crafted SP with ONKYO "OM-OF101" vol.6 - finale


I put into action the addition of a tweeter to increase the high frequency energy of this loudspeaker.

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First, I checked the 30-degree characteristic of the OM-OF101 unit alone again, and found that it gently dropped from above 4KHz.

- Frequency response of OM-OF101 full range (30 degrees)

If the OM-OF101 unit was to be connected to a tweeter, I felt that an 8k-12kHz crossover was appropriate.

The additional tweeter was an Olasonic super tweeter included in DigiFi No.20 magazine.
I got it about a year ago at a bargain price, and it had been forgotten in a corner of my bookcase, so let's have it sing this time.

First, I tested the frequency response of the super tweeter only, using different capacitors that I have.

There were four types of capacitor capacitance: 0.22ƒĘF, 1.0ƒĘF, 1.5ƒĘF, and 3.3ƒĘF. The manufacturers varied, and included some that had been used quite some time ago. I didn't take a picture of them because they looked bad with butyl rubber stains and such.

To match the 30 degree response of the OM-OF101, I measured the frequency response at a 30 degree angle from the front axis of the Olasonic tweeter.

- Frequency response of Olasonic tweeter alone (30 degrees, 0.22ƒĘF)

- Frequency response of Olasonic tweeter alone (30 degrees, 1.0ƒĘF)

- Frequency response of Olasonic tweeter alone (30 degrees, 1.5ƒĘF)

- Frequency response of Olasonic tweeter alone (30 degrees, 3.3ƒĘF)

The 0.22ƒĘF capacitance had a low high frequency level. The 1.0ƒĘF capacitance extended to 16kHz. The 1.5ƒĘF capacitance had a lower level above 10kHz due to the phase. I thought that the 1.0ƒĘF capacitance was the safest choice.

Next, I measured the frequency response on the axis. I retreated from the baffle surface by 0 mm / 15 mm / 20 mm.

- Frequency response of OM-OF101+Olasonic tweeter (on axis, 00mm)

- Frequency response of OM-OF101+Olasonic tweeter (on axis, -15mm)

- Frequency response of OM-OF101+Olasonic tweeter (on axis, -20mm)

The offset of 20mm was quite low from 10kHz onwards. In the case of the 00mm offset, which is the same as the baffle surface, it seemed to go down gradually from 4kHz.

The offset of 15mm showed an increase in the high frequency range. This was because the voice coil position of the OM-OF101 unit was around 12-15mm, so I guessed it was standard practice to match the voice coil position. After that, I decided to fine-tune the position while listening.

I could also try changing the polarity, but I decided to play a few songs in this state (C=1.0ƒĘF, 15mm from the baffle surface, normal phase) to check the sound.

At first listen, the reproduced sound was clear and crisp in the high frequency range and the center position was clear. Because of the super tweeter, the connection between the mid and high frequencies was natural.

The female vocalist sang without any sense of clutter. The bass line in the low range also seemed to have changed to a tighter direction. This might have been an effect of aging the unit.

Finally, I compared the characteristics with those of the ScanSpeak 10F/8422-03 10cm full-range unit, which was included in the August 2012 issue of Stereo magazine.


I designed this box with a 3.7L capacity and bass reflex rear duct fd=108Hz. The box is designed to be installed horizontally, so I felt it would be a bit uncomfortable if it was installed vertically.

- Frequency response of ScanSpeak 10F/8422-03

- Frequency response of ONKYO OM-OF101

Their sound pressure levels seemed to be comparable, but this box had a significant drop below 100Hz. There was a 9 year difference between the two boxes, so it was hard to compare them under the same conditions.
posted by toons at 03:03 | Audio


Apple "HomePod mini" - Review and frequency response measurement.

I just got the Apple "HomePod mini" as an AirPlay evaluation device. The box was smaller than I had imagined.

HomePod min(2).jpg

I immediately took it out of the box and tried to set it up, but it took quite a bit of time because I had deleted the Home app or turned off Bluetooth.
After I managed to finish the setup, I can play music from Apple Music app without any problem.

So I decided to measure the frequency response of this device by playing sound from iTunes.

It was measured on a table at a distance of 1 meter with "Audio Frequency Analyzer" (AFA) app.

I played a sine wave at 1kHz to roughly adjust the playback level.
Then I played back pink noise and measured the frequency response by AFA app, holding the peak for about 15 seconds and doing a 1/3 octave band analysis.

- FFT measurement (playback level adjustment: 1m, Sine wave 1kHz)

- Frequency response measurement (1m, Pink noise, 1/3 octave band analysis, HOLD on)

In this measurement, the levels at 160Hz and 200Hz were a little low, probably due to standing waves, as they also appeared in other speaker measurements.

For the size of the enclosure, the bass extended well down to 63Hz. The high frequency range above 2kHz was about 2 to 4dB lower than the mid range, and the characteristic sound point seemed to be around 12kHz.

The auditory response was close to this frequency response, and the bass feeling was more than I expected, so it was easy to listen to music even at low volume. I felt that the drivers and passive radiator were well designed for this small size.

The HomePod mini does a very good job of playing music for background music!
posted by toons at 01:17 | Audio


Hand crafted SP with ONKYO "OM-OF101" vol.5 - Extensions

This gimmick is a duct plug!

Cut from a scrap piece of OSB plywood.


I had to cut it out six times in total to fit the diameter of the duct holes. The thing behind it is the auxiliary plate for the tweeter, which is in the process of being painte

Here is a comparative image of bass reflex mode and sealed mode.

- Bass reflex mode

- Sealed mode.

I immediately measured the frequency response of the bass reflex mode and the sealed mode.

They didn't seem to have any extreme differences, but the 63Hz level seemed to be a little lower in the sealed mode.

- Frequency response in Bass reflex mode

- Frequency response in Sealed mode

As a 10.5L sealed box, f0c (f0 of the unit when installed in the box) is calculated around 101Hz, which is a little higher frequency than bass reflex.

My impression is that the bass is a bit suppressed in sealed mode, and bass reflex mode is probably the better choice.

If sealed mode is used, it would be better to add a little more sound absorbing material.
posted by toons at 00:04 | Audio


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.


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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


Hand crafted SP with ONKYO "OM-OF101" vol.3 - painting

The temperature has dropped in September, and it feels a bit like autumn.

While I was waiting for the purchase of parts, I varnished the speaker box. (Really be satisfied with the way it looks?)


I lightly painted the back plate with black spray. This was only one coat of paint, so it was done in an instant.
“h‘•(— ).jpg

The only remaining step is to install the terminals and the unit.
posted by toons at 18:24 | Audio


Hand crafted SP with ONKYO "OM-OF101" vol.2 - assembly

Today is usually the last day of summer vacation for children.

Some areas have extended the summer vacation for COVID-19, so it will be hard for parents and teachers to take care of them.

I've been working on assembling the speakers since last weekend.

It's a simple bass-reflex structure, so it's easy to assemble in order, but there are a lot of difficulties due to the lack of precision in cutting by amateur.

The first step is to attach the auxiliary reinforcement plate and duct plate to the baffle plate.


The duct board is screwed so that it can be adjusted later.

Glued the diagonal side panels and side panels on both sides of the baffle board.


There is still a gap at the diagonal cut point. It may look like a straight cut, but it's probably slightly crooked. When the bond is dry, fill in the gaps with wood putty.


Install the back plate.


Lightly fill it with sound-absorbing material.


The back plate is made of the same size plate screwed together so that it can be adjusted later.

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This is what it looks like when the back plate is attached.

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Glue the top plate.


Due to poor cutting accuracy, the diagonal side panels and the top panel were out of alignment. If I get motivated later, I will try to adjust them by planing.

The box volume is about 10.5 liters, and the tuning frequency of the duct is calculated to be about 75Hz.

This is a little larger than the example and recommended box, and the duct frequency is lower, so I hope it will produce a relaxed bass sound.

After preparing the speaker terminals and the speaker unit, I found out that I didn't have any Faston 250 terminals in stock! Have to buy some.

As a result, this speaker craft will not be completed until after this weekend. So, I may try painting it with water-based varnish.
posted by toons at 13:06 | Audio