[gkannan]

3-way front stage active with rear passive and 15 inch subwoofer in a Volkswagen Polo




I was approached to help in building a setup that could be used for both SQ as well as a a decent SPL in a Volkswagon Polo.
The owner had quite a bit of equipment of which the most challenging was the 15 inch Digital Design subwoofer.
The car being a hatchback, it was tricky to design one to satisfy both the needs of listening which oscillated from pure sound quality to a bit of head banger as well.

Amplifiers - 3: Audison LRX (4-channel amp), Hertz HDP4 (4-channel amp) and a Hertz HDP1 (mono).
Speakers: Frontstage (Fully Active) - Audible Physics RG50 tweeters, Audible Physics NZ (3.5 inch) wideband and Audible Physics Brahma (6.5 inch) midbass
Rear Fills (Passive) - Hertx Mille components
Subwoofer: Digital Designs 15 inch (4 ohm single or as 2 ohm dual voice coil)
Head Unit: Pioneer 5000 series
Digital Source: Allo Digione
Processor: Helix DSP mkii pro
Cables: Belden coaxial, Connectix interconnects and Belden Speaker Cables

SUBWOOFER
The biggest challenge in this setup was to design the subwoofer due to limitation of space.
I did my Maths and decided on a 3.2 to 4 cubic feet 2nd order bandpass enclosure.
As it was the persons daily ride, and mostly within city, he was open to give away the wheel well for the fiberglass/wood fabrication.

I will let the pictures speak here.









Boot Cover made with thick MDF and two vents to let the bass into the cabin




This way of designing the subwoofer had many advantageous with respect to this car.
1. i could get good depth in the enclosure and get both the bandpass accurate.
2. The 1st bandpass located at the bottom, trapped the back waves and directed it out via the 2nd bandpass which was facing up and at the farthest end from the sub.
3. As the base of the sub was completely locked into the wheel well (which was completed damped on all sides), there was no rolling or vibration even at the highest SLP levels.
4. It left enough space to mount all the three amplifiers in the boot along with the DSP and the digione. All I had to do was run one RCA cable from the Pio head unit to the DSP. I could keep rest of all the signal cables short, except ofcourse the speaker cables.

Front Tweeters and Wideband:
This was another big challenge due to the shape of the dashboard, limited depth, airbags, puny A Panel and external air vents close to the A Panel in the dashboard.
For the wideband to play its capable bandwidth from as low as 250hz, I needed minimum 1 to 1.3 liter enclosure.
I managed to fabricate this by cutting out a portion of the A Panel cover and utilizing the entire cavity of the A Panel. Then the wideband and tweeters were properly angled to keep them as away from the windscreen and side windows as possible and still minimize it from getting off axis to the driver's seat. The wideband compensated for stage height and the tweeters for width in the design.
The A Panel at he bottom had a little vent for routing cables etc, this I left deliberately open to reduce encosure resonance. The metal face of the A Panel was covered with a 8mm layer of rock wool pad to prevent reflection from the metal surface.

The pics:











Rear Tweeter fabrication:
As the rears were only fills to be used when there were rear passengers, I fabricated the tweeters as close to the midbass on the doors.



The install was completed in 8 working days as the installers could not work continuously.
It took another 8 hours to troubleshoot the nitty grity and fully tune the setup.

The Helix DSP pro is a marvel, a super SQ beast with tons of active tuning features

I finally settled for
Wideband: High passed at 289 hz (at 12db). (No low pass
Tweeters: High passed at 12600 hz
Midbass: Bandpassed between 80 hz (18db) and 289 hz (12db)
Subwoofer: Low passed at 80 (18db).
Db levels set individually for complete blending of the all the drivers.
Time aligned for proper imaging and staging.

Totally phase aligned, time aligned and gain matched with ears using a collection of tuning tracks and later fined tuned with familiar songs.

The DSP comes with a remote which can/was mounted in the front under the Pioneer headunit. It can store up to 30/40 presets and the user can switch to a needed preset instantly with a flick of a button.
I provided three preset options:
One pure SQ setting with only frontsatge, one with the rear also paying and one full SPL setup.

Impressions:
The depth is almost a foot outside the windscreen, superb height and width as well. No digital grain or fatigue. Expecting further refinement in another 100 to 150 hours of break-in.
The output from digione has better fidelity than the output taken from Pioneer.

I have kept it brief, if there are any queries and sugesstions, please post here.

[Kosfactor]

The placement of speakers on A pillar is something i have been dreaming of , its perfect, just the way it should be. i hope with some 3d printing we can better integrate this to the A pillar.

[deepfusion]

Please share the delay settings.

[navin]

Originally Posted by gkannan

I have kept it brief, if there are any queries and suggestions, please post here.

Great install. It's been a long time since I have seen a real quality audio install done with passion.

The challenge I have found with large heavy woofers is that if the cone is too heavy you get a sag of the spider over time. I don't know which model of 15" woofer you used and what the Mms of the driver is but I would be wary of this if installing a woofer facing up or down.

[COMMUTER]

Thats by far the most intricate setup I have seen.

I want to know whether you took the alternator capacity in to consideration before starting on this endeavor.Would you be able to share how many amps will this setup be drawing on a regular volume setting and while at max.

[gkannan]

Originally Posted by COMMUTER

Thats by far the most intricate setup I have seen.

I want to know whether you took the alternator capacity in to consideration before starting on this endeavor.Would you be able to share how many amps will this setup be drawing on a regular volume setting and while at max.

Yes the alternator capacity was taken into consideration. The average draw from the audio setup is well under 50 amps and peaks at around 80 in SPL mode at short bursts which the customer rarely uses.

Even in the peak SPL, I did not observe any dimming of electrical etc. A capacitor could help but is really just a luxury in this case.

[gkannan]

Originally Posted by deepfusion

Please share the delay settings.

TA set by distance:

Left Tweeters: 41 inches, Right Tweeters: 32,07 inches
Left midrange: 43.5 inches, Right midrange: 33.05 inches
Left midbass: 53.99 inches, Right midbass: 40.02 inches

[salman_ferrari]

Originally Posted by gkannan

Yes the alternator capacity was taken into consideration. The average draw from the audio setup is well under 50 amps and peaks at around 80 in SPL mode at short bursts which the customer rarely uses.

Even in the peak SPL, I did not observe any dimming of electrical etc. A capacitor could help but is really just a luxury in this case.

Great setup Kannan, would love to catch-up and have a demo.

Electricals in my Polo is dimming at times & I'm not sure what causing it. The VW service weren't able to figure it out either. Only things changed electrically speaking were front co-axial speakers changed to Focal VW IS 165 & have OSRAM Xenon kit installed on the low beam. Could it be one of these?

[gkannan]

Originally Posted by salman_ferrari

Great setup Kannan, would love to catch-up and have a demo.

Electricals in my Polo is dimming at times & I'm not sure what causing it. The VW service weren't able to figure it out either. Only things changed electrically speaking were front co-axial speakers changed to Focal VW IS 165 & have OSRAM Xenon kit installed on the low beam. Could it be one of these?

Hard to say what is causing it. You are welcome to have an audition. Please PM me your number.

[Chillout]

Wow, this looks like a terrific setup, would definitely love to see this in person. Reminds me of a similar setup I had in my Nissan. It was obviously a bit bass heavy, but would turn heads wherever I drove it.

[invincible7]

Congrats Kannan for the install, well planned and executed.