An experiment with ScanSpeak 5cm SP unit

Due to the action restrictions for COVID-19, I can spend a lot of time for my house cleaning.

I discarded old pens, dry ink, and old mechanical pencils, so I had two empty pen stands.
An acrylic cylinder case purchased from the MUJI store, with a diameter of 8 cm and a height of 10 cm. The same thing has already disappeared in the MUJI web shop.

It would be a little fashionable if a speaker was installed in it. However, the only unit that fits this size is ... only ScanSpeak 5cm full range (5F/8422T03) from Stereo magazine appendix some years ago.


When I removed the unit from the sleeping SP box and tried to match it, I needed something to support the unit. It was necessary to cut a 7mm thick MDF into a circle.
However, this has become a few daunting task. Using a free cone, I first made a hole in the unit diameter and then cut out the surrounding area, but the diameter slightly shifted. I decided to make some double-layered discs and pick out some of them. At this work, I spent all afternoon.

In addition, I was thinking of adding duct-like things to the acrylic pillars. There was no tool to open a hole of about 10 mm, and cracks were likely to occur when trying to forcefully open it, so only the hole for the cord was made.


I finished this work and connected the unit. I measured the frequency response without using any sound absorbing material, and it was similar to a bare unit. It fell smoothly below 100Hz, and it felt like a closed type.


When I tried to connect another unit here, there was no sound. The resistance value was not stable even when measured with a tester, and it was broken. I gave up listening to the stereo sound with the pair units.
This unit is still selling at the ONTOMO net shop, so I would like to try it again if I have the opportunity.

This time I will record it as an experiment.

Note: Handcraft speaker using ScanSpeak 5cm full range "5F/8422T03", 2017/3/20
posted by toons at 19:44 | Audio


New handmade SP using YAMAHA 8cm full range units

I found the SP units for YAMAHA audio system while cleaning my house in this holidays.

Since the units spec only was shown 8 cm and 6 , I designed a new SP based on the installation location and the remaining amount of MDF material.

I decided the height to be about 195mm for the purpose of fitting it on the TV shelf.
Since the width of the MDF is 110 mm, the baffle size is 110 mm + plate thickness 12 mm x 2 = 134 mm. The SP box capacity will be about 1.5L.


Since the duct port is facing downward, the bottom plate was raised a little to raise it to the bottom state. The duct length is about 90mm.

The cutting was completed in 30 minutes, and the assembly took about 30 minutes due to the simple structure. It was completed by waiting for the woodworking bond to dry overnight and then installing the SP unit.


I measured the frequency response of this speaker by "Audio Frequency Analyzer" app. When measuring 1 m on the axis with pink noise, 125/160 Hz was slightly lifted, so it seems that the duct is working.


When I put it in the actual installation place, the height was perfect. It feels good for TV sound, and human voices are easier to hear.
posted by toons at 12:20 | Audio


Nakamichi SR40 STASIS Stereo Reciever


Nakamichi SR-40 STASIS Stereo Receiver

An amplifier with a tuner released in 1987. My audiophile friend asked me to this amp if I could repair it.

gSR-40h has a STASIS power amplifier circuit. STASIS is a non-feedback type amplifier developed by Dr. Nelson Pass at Threshold.

Nakamichi received a patent license in 1985, and in the following year it was first commercialized in the power amplifier "PA-70 / 50" series. At that time, Threshold released only super-high-end products and licensed Nakamichi to develop products in the middle range and below.

There was no pre-main amp product at Nakamichi at that time, and the stereo receiver product with STASIS was the SR-40 (SR-4 in overseas), and it was a high-end model with a sales price of 148,000 yen. There seems to be a product called gSR-30 / 20h in the lower model.

Until this "SR-40" was manufactured in Japan, but the models after that seem to have been manufactured overseas, and the product quality seems to have deteriorated considerably. The successor model was renamed gTA-40 / 30 / 20h and was released until around 1990.


At that time, stereo receivers were very popular in North America, and the market size was also large. In the catalog of gSR-40h, gThe Audiophile Receiverh and gRemote Control STASIS Receiverh are displayed and it seems that it was appealing as a stereo receiver for audiophiles.


The appearance of the gSR-40h is so good that it cannot be seen by an audio product 32 years ago. The owner said that sound was coming out, but sometimes it was also mixed with noise.
However, I was drowned to turn on the power suddenly, so I opened the case and checked it.


The lower board is the main amplifier board, and a fairly large heat sink is placed in the center.
Dust was piled up on the board, but no electronic parts were burned or burned out.
The old famous device Sanken 2SA1491 / 2SC3855 was placed in a 2 parallel configuration in the final stage.


Since it is almost composed of discrete parts, the repair is a little easier.
However, this is the first time I have seen an amplifier with so many styrene capacitors. Styrene capacitors are famous parts because of their good sound, but they are very sensitive to heat (heat-resistant temperature is about 85C), so if a damaged part is found, it will be very difficult. Since it is already discontinued as a part, whether there is dead stock somewhere ...


Since there is also an AM / FM tuner board on the front panel side, it is a fairly complex and high-density mounting. To improve the sound quality, it may remove the tuner circuit.


The power supply has a large toroidal transformer, and the two large electrolytic capacitors were still safe.

I tried to leave it for a while after turning it on, but it did not generate any heat, abnormal vibration, or smoke. Because of the large heat sink, the temperature rise of the transistor is also mild.

When I was fine and put the music signal in the CD input and turned up the volume, the sound came out from the speaker properly. The main volume can be controlled smoothly without any rust, but the volume knob is quite heavy because of the motor control.

I also found that the display brightness of the AM / FM tuner was low, making it very difficult to see. When the FM antenna was connected, the signal meter was also displayed and the FM received sound could be played properly. I was surprised that the reception sensitivity was better than my FM tuner.

After a while, there was a symptom that sometimes the left channel was not output, but I found that the tone control volume seems to be poorly touched.

It seems to be mainly due to poor contact of the signal path, so it seems to be okay to not complete overhaul. For the time being, I'm trying to clean the contacts in questionable parts.

I've never heard of a STASIS amp, but it sounds like a high-end amp rather than a stereo receiver.
It's not particularly powerful, but it's a bit of a beautiful sound!

The reason why it was not popular in Japan was probably due to the product form of the receiver.

According to reviews from overseas users on the Web, the gSR-40 (SR-4)h has the impression that it sounds better than the gPA-50 (PA-5)h power amplifier with a STASIS circuit.

Around 1990, Nakamichi broke down in terms of contract with Threshold, and was unable to sell amplifier products with STASIS circuits.


This gSR-40h is a complex implementation, so it would be troublesome to completely disassemble and clean it.@I got a service manual, so I would like to repair it in the meantime.B

Note (2019/12/11):
In the running test, sometimes the left channel was not output! Not only due to poor contact in the tone control section. I seem to have to overhaul it.
posted by toons at 23:58 | Audio


OSAKA High-end Audio Show 2019


I went to Osaka High-end Audio Show 2019 last weekend.

After 16:00 on Friday, each listening room was full and most of them seemed to be in their 50s and 60s.

This year, the venue was only the Hearton Hotel Shinsaibashi, so it may be because people were concentrated.



The Bayz Audio's gCouranteh speaker was very interesting, with a very large and unique pipe shape.


The Burmester amplifier, which was placed in a corridor in the hallway, was created a strong presence. (Is the power amplifier's top-plate flat for listening equipment?)



As an audio sound, I was impressed that JBL EVEREST speaker, which was playing in Mark Levinson, was producing a stable good sound.
posted by toons at 16:24 | Audio


SANSUI AU-907 Limited


SANSUI AU-907Limited

Released in 1994, the third-generation limited products of Sansui 907 integrated amplifier.

Equipped with a HYPER -X balance circuit, it featured a clean sound in the mid-high range of Toshiba's old MOS-FET (2SK405 / 2SJ115). This is still popular as the best sounding device for audio power MOSFETs along with Hitachi 2SJ49 / 2SK134.

Last night, after a long time, I tried to play an analog record to adjust my 2way speaker, but the amplifier was out of order and no sound was produced (CD direct input was sounded).

This morning, I opened the top plate to clean the inside, and after removing dust for the first time in several years, it started to sound normal.

# Inside of amplifier

# 6mm thick aluminum bonnet with copper powder coating

# Left channel power block

# Right channel power block, preamplifier section (black box at right end)

# Power block (large power transformer with a total weight of 13kg)

It was a total weight of 34kg, so I was concerned that it would hurt my waist when placed on the floor, but there was enough reward to clean it!
posted by toons at 03:15 | Audio


MarkAudio OM-MF519 vs OM-MF5, Fostex speaker frequency characteristic comparison - extra edition

Extra edition report of my handcrafted speakers characteristic comparison.

I tried to measure the frequency characteristics of MarkAudio OM-MF519, last year's model OM-MF5, and some FOSTEX products under the same conditions as much as possible.

The amplifier volume position was the same, pink noise, and the measurement position was fixed at 1m on the axis, but the height of the unit was adjusted precisely, and there were a difference of several centimeters.

This was measured frequency characteristics with RTA app "Audio Frequency Analyzer".

OM-MF519 double bass reflex vs OM-MF5 bass reflex

# MarkAudio OM-MF519iDuct 15cm + 2.5cmj


# MarkAudio OM-MF5 (Tw is removed.)


As expected, the rich bass of OM-MF519 double bass reflex!
It seemed that the level around 30-50Hz is higher than OM-MF5 bass reflex.
For hearing, the left handed sound of the piano was resonated deeply. The loudness of the contrabass was also rich. And the mid-high range resolution is quite high, and the sound image localization was good due to the narrow baffle.

On the other hand, OM-MF5 bass reflex feeled like being pushed by energy. Since 60-100Hz was the same level as the mid range, the force of the base went up here. Full orchestra was a little difficult, but it was more suitable for Pops and Jazz.

The OM-MF519 double bass reflex was a 12mm front MDF, so I intended to reinforce it, but I found that the top plate was vibrating a little.

Since OM-MF5 bass reflex had 18mm side plate and bottom plate, it may be affected by the difference in rigidity.

Compared to the playback sound of two speakers, I prefered the normal bass reflection.

And measured other speakers under the same conditions!

Fostex FE83n


Fostex FE83n mini bass reflex, installed in the enclosure in the Ontomo MOOK appendix.
The sound pressure level was the same, and the low frequency response was attenuated gently from 100Hz, making it easy to hear.

Fostex M800


2016's Fostex M800.
This box was a simple square shape, but the inside is actually elaborate. It had a hard reinforcement and air venting duct port, but was almost a sealed design.

The low frequency response feeled better than FE83, but was less conservative than OM-MF5. Since the sound had a peak in the high range of the unit, there were a feeling that it will be a little audible, such as a scratching sound. The low range was neutral and sound power can be put in as it fully.

Each units and boxes had very different characteristics and sounds. How far I can get to my favorite sound is a long way off.
posted by toons at 02:12 | Audio


MarkAudio "OM-MF519" Speaker assembly Part 7 - frequency characteristics


After painting, I played a lot of music with this speaker for sound aging.

My personal impression is that the bass sound is very loud despite the 8cm full range. This is probably due to the bass enhancement effect of the double bass reflex.

# frequency characteristics (distance 1m, Pink noise, measurement by RTA app "Audio Frequency Analyzer"j

However, looking at the frequency characteristics measurement above, it seems that the elasticity and tightness are retreating compared to a general bass reflex type, probably because 125-200Hz is slightly depressed. In a sense, 100Hz or less is too high.

Next, I adjusted the length of the second duct and examined how the frequency characteristics changed.

# Original duct (15cm)


I prepared a paper pipe with a slightly smaller diameter and measured it in units of 2cm.

The level of 100Hz decreased in the duct +2cm. It may be the effect that the duct area is slightly reduced.

# Duct +2cm


After that, the length of the duct was increased by 2cm, but no significant change was observed. It is also possible to pick up ambient noise.

# Duct +4cm


# Duct +6cm


# Duct +8cm


# Duct +10cm


# Duct +12cm


As a trial, I changed the length of the upper and lower ducts extremely. But, it did not be much different from closing the duct.

# Duct +2cm, +10cm


These results was not clear, so I have to try several times with different dates. I try listening with a duct length of + 4cm for a while.
posted by toons at 03:20 | Audio


MarkAudio "OM-MF519" Speaker assembly Part 6 - external painting


As usual, the back and top plates were painted with black spray. To change the taste a little, I started to paint blue to the side plates, but the gas ran out during spraying on both sides.


I gave up and overlaid with black from above. After all, it doesn't look good in the surrounding black.

And then I found the remains of the cork sheet!


If the front baffle is cork-lined, I expect a retro feel. The baffle surface is where the woodworking bond is diluted and bonded, and the surface is coated with a thin aqueous varnish to increase strength.
The baffle edge was not able to be processed well and it floated a little around the middle.

It was made by cutting out round to fit the unit.
The sound absorbing material was inserted with the weight of the left and right channels matched.



Finally, the speaker was completed by tightening the duct screws!

posted by toons at 00:17 | Audio


MarkAudio "OM-MF519" Speaker assembly Part 5

MarkAudio OM-MF519 Double bass reflex speaker is almost completed.


However, the entire box is still under consideration for external painting.


For trial, I painted only the duct part of back side.

posted by toons at 01:50 | Audio


MarkAudio "OM-MF519" Speaker frequency characteristics, part 3

MarkAudio OM-MF519 Double bass reflex speaker is being adjusted.

The characteristic (1) was the result of adjusting the sound absorbing material to match my listening preference.

This was a measurement result at 1m above the unit axis (tilt about 15 degrees to the front of the baffle). The peak at 250Hz dropped, and the characteristics seemed to shift to 200Hz or below.

The characteristics of the second duct seemed to be concentrated around 60-100Hz. Then this area may not change unless the duct length is changed.

(1) Frequency characteristic of adjusting the sound absorbing material

Incidentally, the characteristic (2) was measured on the front axis of the unit. The peak of 12k-16kHz which is the high frequency characteristic of this unit was appeared.

(2) Frequency characteristic on the front axis of the unit

The characteristic (3) was the result of distance from the baffle to 2m.
Although a peak was seen at 100Hz, I thought that it was possible to get around 50Hz as a low frequency characteristic.

(3) Frequency characteristic from the baffle to 2m

As for my impression, I could hear the profound feeling of the bass and strings with the feeling of adding a subwoofer.

However, the feeling of tightness in the low frequency area will be reduced, so the rhythm may be lighter in jazz and pop music. I don't know if this is a characteristic of the box, or if the work accuracy or adjustment is insufficient.

Since the internal adjustment is over, I will consider finishing the box surface.
posted by toons at 02:54 | Audio