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    Thread: 4-way active setup in a Polo with 15 inch subwoofer

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      4-way active setup in a Polo with 15 inch subwoofer

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

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      I was approached to help in building a setup that could be used for both SQ as well as 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 some head banger as well.

      List of Equipment:
      Amplifiers - 3
      : Audison LRX 4.1K (4-channel amp), Hertz HDP4 (4-channel amp) and Hertz HDP1 (monoblock).
      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) - Hertz Mille components
      Subwoofer: Digital Designs 15 inch (4 ohm single or as 2 ohm dual voice coil in parallel)
      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 close to company specs as possible.
      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.

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      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:

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      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.

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      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 suggestions, please post here.
      Car Audio: 4-way active
      Home Audio: Passive

    2. #2

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      Congratulations ! Clearly well thought through, planned and well executed build, workmanship on A pillar pods and sub box is great.
      DigiOne Signature | 7" Tablet | AP NZ6W | AP NZ3 | Biketronics BT4180 | Adire Audio Brahma | Rockford T1000-1bdcp | MiniDSP 8x12

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      Very nice work sir, gear and pillars look awesome i really like the a-pillar install and tweet location as well, great work with top quality parts.
      Nice job on the sub enclosure looks clean too.
      Audible physics Avatar 136 Active/MPS cables /Tru Tech Billet stage 2/SounDigital SD600.1/Sub -Audible physics Avatar 10"/ Focal Fps/Dayton 408

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      Wideband Low Pass

      Kannan sir

      both wide band and tweeters will play high frequencies?
      Isn't it best to have minimal drivers to play all frequencies without overlap (except for the octave slopes)?
      what happens in such a case? Or is it better because NZ3s ability to play high frequencies beautifully and tweeter shall have same sound signature as well?

      Wideband: High passed at 289 hz (at 12db). (No low pass
      Tweeters: High passed at 12600 hz


      Quote Originally Posted by gkannan View Post
      [COLOR=#141414][FONT=&amp]3-way front stage active with rear passive and 15 inch subwoofer in a Volkswagen Polo

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      Last edited by Nomad; 27th May 2019 at 09:37.

    5. #5

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      Quote Originally Posted by Sarabpreet View Post
      both wide band and tweeters will play high frequencies?
      Isn't it best to have minimal drivers to play all frequencies without overlap (except for the octave slopes)?
      what happens in such a case? Or is it better because NZ3s ability to play high frequencies beautifully and tweeter shall have same sound signature as well?
      The latest NZ is an excellent wideband driver and I personally can live without tweeters with it. However, adding a pair of tweeters will add a bit of airiness if crossed properly and positioned accordingly.
      In this case the RG-50 is a very responsive tweeters more suited for 2-way or a 3-way with ideally a midrange and not a widebander.
      So I had to cross it quite high and attenuate it accordingly to keep it from peaking at the shared frequencies with the NZ.

      For someone who wants to go for tweeters with widebanders, I would suggest tweeters with f/s of 5khz or more. Some planar, ribbons and AMTs will suit this category as they can play really high into the 40khz region. There are also some select soft domes, but they will be quite pricey.

      I run a similar setup in my car, but the AMT tweeters I use are crossed at arouns 11khz/6db using a capacitor as my active headunit only supports 3-way active. The widebander I use has a natural roll off at 13khz from where the AMTs take over without a sweat. Though the tweeters are only attenuated at 6db slope, the responce below 9.5khz is almost inaudible as the f/s is high at 6khz
      Car Audio: 4-way active
      Home Audio: Passive

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      Glad to see educated and knowledgeable pros venturing into ICE commercially in Chennai. Wish you all the best!
      FiiO X7 Mark II - HELIX DSP PRO MK2 - TRU Billet v2 B41-S - MOREL Elate Ti 602 - MOREL Ultimo Ti 102

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      Quote Originally Posted by keerthi View Post
      Glad to see educated and knowledgeable pros venturing into ICE commercially in Chennai. Wish you all the best!
      Thanks for the compliment Keerthi. I am just chartering the shallow waters. Still a very long way to go. Hope that I can make a difference and contribute
      Car Audio: 4-way active
      Home Audio: Passive

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      Quote Originally Posted by gkannan View Post



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      Wow, Such a elaborate set up, looks like lot of money and hardwork went into the set up.

      But i have a question, putting something on those A pillars , is it not a safety issue in case of a collision ? in this case i can see that those tweeters in front of passenger seat would clearly obstruct the airbags from deploying. it also enhances the blind spots of the driver to some extent. more over there is always a possibility of anything not part of the original shell or A pillar construction will fly off in case of a collision hurting the passengers.
      Last edited by Nomad; 27th May 2019 at 09:49.

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      Quote Originally Posted by Nomad View Post
      Wow, Such a elaborate set up, looks like lot of money and hardwork went into the set up.
      Thanks for the compliment.
      Quote Originally Posted by Nomad View Post
      in this case i can see that those tweeters in front of passenger seat would clearly obstruct the airbags from deploying
      No airbag deployment is not affected, it was confirmed with the Volks guys. The customer has no problems while driving with respect to any blind spots.
      However I cannot comment on the 3rd point you raised as to if the speakers in the A Panel will act as projectiles. You do have a practical point there.
      They have however been properly screwed in to both the dashboard and the A Pillar metal. I don't expect them to fly off but possibly crumble with the A Panel in a major collision.
      However I think audio enhancement are much safer that the huge mods that the youth do nowadays to cars what are I guess called remapping and other such stuff.
      Car Audio: 4-way active
      Home Audio: Passive

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      Quote Originally Posted by gkannan View Post
      I don't expect them to fly off but possibly crumble with the A Panel in a major collision.
      I still suggest, as an installer, one should put in the disclaimer in the job order, else later on it might come back and haunt the installer in case of an accident, injury or death and medico-legal-insurance case making such installation to be the cause of the accident and the consequences there off. our country is slowly becoming litigation heavy economy and more over any litigation is long drawn.

      personally i would not do as a supplier or consultant, anything that might remotely put the life of my client and his business in danger, even though client himself is willing to do so. in such cases having a clear job order with this disclaimer and waiver clause will help.

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