Twingo 3 EV custom soundsystem (Focal + Visaton + Pioneer)

Julien ARNAUD

Following the purchase of this car, I planned on having some decent sound.

I initialy purchased a cheap (50€) chinese 1 DIN + 6" Android Auto compatible head unit. My plan was to couple it with my MiniDSP + 24V step up converter + 4x100W from the Twizy. While the head unit did work with Android Auto wireless (which is insane for the price), it turned out to be a mess to wire in the DSP, step up and amp. I'd have to run wires from the battery or use relays to have a solid rail that turns on with the car.

So instead I ordered a Pioneer head unit SPH-DA97DAB. It has the advantage of being able to handle my new DIY subwoofer on its own. It's capable of HPF on the front speakers (Focal IS RNS 165), with custom cuttoff frequency and custom slope. And able to bridge the rear channels into a single 70W 2Ohms, perfect to wire my 60W dual coil sub in parallel. All with LPF and custom slope built-in. So basically plug in and forget.

Regarding the subwoofer, the goal was not to be loud but to be accurate. I aimed for 35/40Hz flat in-car.

I salvaged the Visaton W 130X that was used in the Twizy's subwoofer and measured the space available under the rear seat (which oddly has vacant space underneath them!).

Initial plan was to use a truncated corner to give a gentle double 45° angle bent on the vent

I came out with 38cm x 24cm x 10cm. Running this in a simulation gave a reasonnable vent lenght but requires that I use a slot vent, a first for me.

So the box is 6.7L usable space, and the vent is 8 x 1.6 x 36cm. I had to compromise on the vent length versus air speed. By flaring both side, I ended up with zero audible air noise. I glued the magnet of the driver to the back of the box, to strengthen it without loosing much volume in reinforcements. 

I tried it in the living room, using the awesome web UI of the Crown CTD 8125 to quickly filter it, muting other speakers but one ambiance channel. It's very capable and convincing down to around 38Hz basselines and kicks.

As a reference, it makes these three tracks from my 38Hz playlist sound "full" : 

  1. Royals - Lorde
  2. Trouble on my Mind - Pusha T
  3. Call me - Kimbra

The next playlist down is 35Hz where the bass is pretty much absent : 

  1. River - Ibeyi
  2. Unfaithful - Rihanna
  3. Kars 1 - Tigran Hamasyan

 The next one is the 29Hz playlist, and there is absolutely nothing, obviously : 

  1. White Teeth Teens - Lorde
  2. Home - Rudimental

I then measured in the car, and oh surprise, it's flat down to 25Hz with the natural cabin gain (no EQ or boost). 

Overall I'm very pleased, it's crazy what you can extract from a 14 cm driver. The bass from the sub is hard to fault, the rest of the spectrum is not ideal due to the doors being bare and untreated. Yet the overall presentation is quite convincing once time-aligned. 

The biggest pain was the 10mm MDF. It's too thin and you have to be super carefull using small nails, small screws, etc. But that was the compromise to extract the largest possible internal volume.

Also, the Focal kit I ordered was refurbished on LDLC. Turns out the previous owner likely wired the tweeters without filters and cooked the shit of them. Crazy thing : the coils survived but the membranes did not.

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