My side projects, generally optimizing stuff to the n-th degree. Anything goes.

Julien ARNAUD

High end multi-room sound system (offline/no-cloud)

Goals of the system In plain english : It allows me to play music of my Android phone on Spotify, or play a Youtube video on my Debian laptop, or start mixing on my XDJ-XZ, or play a movie on the Chromecast 4K in the movie room and... have the sound automatically get out of each and every speakers of the house, with state of the art quality on each of them. Keys to reach the goals Components of the system Audio routing The audio routing goes as follows :…

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Julien ARNAUD

House's solar and monitoring system

Here are the specs : Monitoring is done via Home Assistant running in a Docker container, itself running in an LXC container on Proxmox. Most sensors communicate in zigbee, including the Linky via a tiny self-powered module. To communicate with the solar inverter, a Solarman Integration via Wifi is used. The first 4x 435W string is installed on the roof, but the 6x 400W are still on the ground for now, as the hardest part is climbing on the roof with large fragile objects of 20 Kg each and not…

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Julien ARNAUD

Everyday laptop, and computer history

Until around 2007 [0], I was a big fan of powerful desktops as my daily driver. At that point my computer was liquid-cooled PowerMac G5 Quad 2.5 Ghz. This was a beast and I loved it. I then switched to a MacBook Pro 15" Penryn complemented by a NAS to compensate for lack of local storage. I kept on the laptop + NAS train for a while : more recently with availability of 4TB SSDs I went to a laptop-only setup. My previous laptop was the IdeaPad Pro 5 (5800U,…

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Julien ARNAUD

Machine learning desktop

I built a new computer to play with some machine learning. It uses what seems to be the best scoring case for airflow and temperature : Fractal Torrent Compact. The full setup is : The 4090 is capped to 65% TDP as going any further quickly hits drastrictly diminishing returns (anything above 75% should be considered OC). When capped, the card only runs at about 60° ! That thing really is a crazy object and product. During training the computer draws about 400W at the wall. Which sits perfectly in…

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Julien ARNAUD

US-48-500W power supply repair

One of our US-48-500W died at work. Since Ubiquiti has bumped the price and shifted the range quite a lot, I decided to repair it to keep it as a spare. I first confirmed that the PSU was the culprit by powering the switch with my lab PSU. Using a meanwell PSU (RD-125-2448) providing both 24V and 48V rails ,we don't reach the original 500W of PoE power, but that's still enough for our needs (some phones, cameras, and access points). I didn't put much efforts into PSU placement in…

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Julien ARNAUD

Sizing of my heat pump (Daikin 3MXM52)

Summer 2023, I finaly decided to equip our house with a heat pump. When we first renovated it in 2016, this didn't fit in our budget but I always dreamt of having a heat pump (who doesn't?). Bellow are my calculation and considerations. Plus some conclusions and retrospective data once the installation was completed. It is a 3 story house built in 1947, all joined by open stairwells without doors. The first level is partially underground. It has been renovated to French standard RT2012 in 2016. If you aren't unfamiliar with…

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Julien ARNAUD

Reloading 300AAC Blackout for accuracy

Since I purchased a Ruger Ranch in 300AAC to complement my DDM4 in the same caliber, I have been attempting to find a high accuracy load. Currently the best result seem to be with very lightweight bullets (110gr Hornady V-MAX with flat butt). I've tried pretty much everything in between. I have tried getting very close to the lands. I have tried N120, N110, N105. I have sorted the brass by weight, sorted the brass by length. Trimmed the brass from the shoulder. All sorts of attempts. Nothing really give…

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Julien ARNAUD

Ruger SR22 USP-style thread cover

A friend had accuracy problems on his SR22, due to the slide having too much play. I was inspired by HK's use of an o-ring on their USP and machined a piece of 4140 into some kind of a muzzle break that also doubles as a slide centering device, using a small o-ring for perfect centering.

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Julien ARNAUD

Sig P322 Suppressor, 3D Printed

I was inspired by The SilencerCo Maxim 9 (Not imported in France) to design my own suppressor following a similar philosophy : maximizing the suppressor volume with a very specific design.  Disclaimer : Suppressors are perfectly legal and non-regulated items in France. If you use any part of this post to produce a suppressor in the USA - or any country where this is illegal, you are sole responsible for any legal consequences. Drawing was done using Sketchup (a fairly old version). As I don't have access to a metal additive…

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Julien ARNAUD

MX-30 lowered with 19" rims

I quite like my MX-30 but the rims and the ride height always seemed off. Using H&R springs (-35mm front, -40mm rear) and Borbet "V" rims, the result is most satisfying. I carefully researched tires, as I was forced to go from 215 to 225 width and didn't want to sacrifice too much range to that. It is after all, a tiny 32kWh battery ! Turns out Goodyear Eagle F1 Asymmetric 5 in 225/45/19 have better rolling resistance (A) than stock Bridgetone T005A tires in 215/55/18 (B) without sacrificing on…

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Julien ARNAUD

Twizy 2.2 DSP corrected sound system with 3D printed subwoofer

I designed a soundsystem for my Renault Twizy around the following elements Subwoofer The subwoofer enclosure was designed to fit in the narrow space behind the passenger seat. This gave the subwoofer a kind of rounded/organic shape. From this shape I got an internal air volume. I looked for speakers that would work in such a small volume and still produce the desired level of bass (I aimed for around 45Hz -3dB). The software popped out a 6.5" Audax with dual coils. The simulation has some compromises though, at full…

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Julien ARNAUD

Blocking hard drive I/O with sound

I replicated the results of Connor Bolton, Sara Rampazzi, Chaohao Li, Andrew Kwong, Wenyuan Xu and Kevin Fu. in "Blue Note: How intentional acoutic interference Damages availability and integrity in hard disk drives and operating systems". I set up one of my DIY Cabasse Spheres in front of a Fujitsu MJA2160BH. Doing a frequency sweep from 850Hz to 1.1Khz at around 102 to 105dB. When reaching close to 975Hz +/- 25Hz, the bitrate of the read file drops from 70MiB/s to a few KiB/s. Data was generated from /dev/random, secondary…

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Julien ARNAUD

Motion simracing rig

Components Intel i7 7700K 16 GB DDR4 512 GB NVMe 2x nvidia GTX 1080 in SLI 750 W Corsair PSU 3x 43" 4K TVs (11520 x 2160 px) ProSimu T1000 2DOF Fanatec Clubsport 2.5 Wheel base ClubSport Wheel Rim SPARCO® Rally ClubSport Porsche 918 Wheel ClubSport Steering Wheel F1® Esports V2 Fanatec Clubsport V3 Pedals Fanatec ClubSport Shifter SQ V 1.5 4.0 audio using 2x 8" Samson Resolv A8 active monitors (front) 2x 6" Samson Resolv A6 active monitors (rear) The whole system draws about 460W idle, and around 700W…

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Julien ARNAUD

Re-enclosed JBL SB210 Subwoofer

Unsatisfied with my JBL SB210 low frequency, I designed and built replacement enclosures. The SB210 is a dual 210mm subwoofer, using ceramic cones in a polymer enclosure. Specifications of JBL's original SB210 are My redesigned enclosure offers The first hurdle was the absence of datasheet for the speakers themselves, as they were never distributed outside of the SB210 system. After contacting JBL Professional, they were kind enough to provide me with the data. These specifications were entered in Dominique Petoin's database and you can now find it there. As I was…

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Julien ARNAUD

DIY Cabasse Sphere Archipel 17 ICD

Inspired by Cabasse's La Sphere high end system, I went on to design and build my own tiny spheres. I like coaxial speakers for their realism in human voice reproduction and cabasse may have a lead in that with their SCS technology. I have been a happy user of their Java MC40 using such technology. I decided on affordable Archipel 17 ICD (300€ the pair delivered). Like with the JBL SB210, datasheet for the low frequency driver were not published. But contrary to JBL, Cabasse gave me no love in…

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