Focal iBus 20 installation and impressions

Intro
I had installed an aftermarket headunit, which cleaned up the sound of the stock Bose system surprisingly well as I had control over high pass filters, eq's and DSP. However, I was still not happy with the Bose sub, particularly as I had the HPF set at 100hz which would clean the mid-bass but would also mean the Bose sub would only play to 100hz.

I was looking for a replacement underseat sub from the onset as I did not want to complicate the install nor did I want to lose any boot space. There were several options available and at one stage was looking at importing a Rainbow Intelli 8 AFE underseat sub.

I finally settled on the Focal iBus 20, an underseat active subwoofer (built in amp) sourced locally for $400 (RRP $500) from Carbon Car Systems. I hadn't actually heard the sub so was taking a risk at spending money which could easily fund a proper sub setup in the boot. But with limited options, a decent review and from a reputable brand, I had reserved hopes.

Installation
The iBus actually accepts speaker level inputs with the use of ISO connectors. However, I opted to install the traditional way of RCAs, with a seperate power and ground. The installation is very straight forward.

1. RCA and remote turn-on was routed under the middle console with a small slit in the carpet to poke through the cables
2. The Power cable was routed under the carpet along the passenger side and came through the carpet from a pre-existing hole where the factory bose was bolted
3. The Ground cable was grounded where the factory bose sub was anchored (second picture) and also came out the same hole in the carpet the power cable did.
4. I also moved the factory bose harness/passenger seat cables (second picture) as it was getting squashed by the mounting plate I made.
5. I made a mounting plate from 16mm MDF (first picture). Thanks to @RedDjinn for the idea. The cuts were rough as guts as I used a freakin hack saw. But it was to be carpeted so I didn't care too much. The sub would be bolted to the plate which would then use the 2 factory bose bolt posts to secure and a third anchor point where I bolted the ground cable. You have to recess the holes for the two factory nuts to go back on. There is also an aircon vent right where the sub is. Hence the U shape of the plate. I stuck some foam on the vent to prevent direct contact with the sub. The third picture shows the clearance of the sub and vent.
6. The second picture shows the final result (bottom of pic being front of car)
7. The forth picture shows the clearence of the sub and the passenger seat (at least 2-3cm from memory)

With the passenger seat in, you can barely see the sub and in the normal position, feet from rear passengers don't hit the sub.

Tuning
At first I was slightly disturbed as I couldn't feel the sub working. I adjusted the gain knob to full and finally could feel sub and hear the bass. However it still wasn't what I had expected. I then connected the sub-remote and turned that up to full. Finally and to my relief, the sub came to life. I tried also turning the sub levels on the headunit to max, that really got the sub going but sounded awful. So I tuned it down to suit.

The reason for maxing out everything on the sub-amp is that at moderate listening levels, the method I used to connect the factory bose amp to the headunit doesn't produce enough volts for the sub RCA output. That is, the bose amp gain is set high even at low volume levels. My headunit volume goes up to 40, but it starts getting pretty loud by about 15. Not ideal, but without any gain adjustment on the bose amp, this is all that can be done.

I spent an hour tuning the cut-offs and eq to suit. These settings may not work for everyone as the roll-off on the LPF/HPF can be vary between different models of headunits and the preset cut-off points may also be different. More importantly, the settings are to suit my ears

Headunit settings:
- HPF 100hz
- LPF 63hz
- Custom EQ +1 800hz, +2 2khz, +1 5khz
- Sub woofer levels 0
- Staging (DSP) Music studio

Sub Amp settings:
- subsonic filter: 30hz
- gain: Max
- bass boost: 0
- LPF: max (as I let the headunit filter)
- Remote control: Max

You will notice that there is a big gap between the HPF and LPF. I initially had the LPF set at 80hz but found the sub to be playing too much of the mid-bass. this would mean I could easily hear the sound coming from under the seat and my left ear was getting a bit tired of it. Low bass should not be detected by the human ear in terms of placement. I set HPF at 100hz as the factory speakers seem to be a bit muddy when set at 80hz.

Initial Impressions
Now the most interesting part, the sound. I will edit this post after the sub has broken in for a more detailed impression, but for now the initial impression. Was it an improvement over the stock bose sub? Definately yes. Is it earth shattering, mind swelling bass? Definately no. This sub isn't about loudness, its all about filling the bottom end, which is does remarkably well.

The settings I used above means the low bass integrated seamlessly as intended by the music. Currently the bass is quite punchy. I hope that once it has a few hours playing, the speaker will loosen up a bit and hence the low end will become a bit fuller and richer.

You can definately feel the seat vibrate from the sub, something I have yet to test with my partner... It is so vitally important that the sub is secured for the best performance. The velcro they provide to secure the sub is far from adequate and will almost ruin the sub's ability to produce bass.

I am very happy with this purchase and can finally say the sound is more than acceptable compared to stock form. I would recommend this to anyone who wants an underseat sub. Unfortunately no sound files as all I have is a mobile phone, which wouldn't pick up the low end to do it justice.

If anyone would like to hear my setup in Brisbane, send me a PM.

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