Want to design and build a Subwoofer for my car. In terms of design principles, what parameters I should consider differently??

[Naveenbnc]

Hi All...

Im thinking of building a 12" ported sub for my car.
In terms of design, what difference will be there between a hometheater sub and a car sub?

(I am not asking about the overall size and shape. I will match to fit in the boot)

In terms of design principles, what parameters I should consider differently.
I mean, the "gain" of the car internal volume is different to the room.
I don't know how it affects the design. Or any other such points to consider ???

Any suggestions please ....

 

[Aniket]

Hi Naveen,

In car audio, you should follow the recommended design/volume given by the manufacturer of the driver. Of course you can tune it to your requirements, but there's no need to go deep into calculations and designing. As the car itself acts as a big enclosure you can get good amount of gain and LF extension. Just simply follow the manufacturer's recommendation.

Design principles are a lil different for both.

For car audio you may follow this channel on youtube: https://www.youtube.com/user/meade916


Regards,
Aniket

 

[Naveenbnc]

Thanks a lot Aniket !!! That clears my dout regarding car enclosure gain.

These guys with lot of tattoos look crazy, but in the background, they do things in a very professional way.
Thanks again for the link

 

[Kannan]

In car the low end can sound quite dynamic as explained by Aniket above.
However if it is a hatchback, I would suggest you to stick to sealed 10 inch sub.

Even if a sedan, I would still suggest a sealed sub as you cannot go wrong with it in design if you stick close to the company specs. A sealed enclosure has a natural roll off, though it will demand more power, but most mono blocks in car have enough juice. Even of you are bridging a 4-channel for sub duty, that should be fine.
Also a sealed sub will need a much lesser volume.
If you are going to go with a 2 ohm sub, be sure your amp can drive it.

With ported if you do not get the port properly tuned, there will be bloat in some frequencies.
You can either place the sub facing the boot door or put it facing sideways, avoid it facing towards the front.

Another important thing you need to do it to properly damp the boot doors and the cabin metal with tarfelt sheets like dynamat or any cheaper stuff to arrest door resonance. This is very important.

A very good and informative site for car audio enthuciats
http://www.bcae1.com/

A useful software for designing sub enclosures
https://www.ajdesigner.com/speaker/

I have used some very good subs in my car audio journey.

The Morel Ultimo 12 (considered a holy grail). It was driven by a monster Celestra monoblock
The Infinity Kappa driven bridged by Pioneer 944 amp (an all time favorite of mine)
and now I am two 6.5 inch midbass in a isobaric design due to power constrains in my old car. It is driven by a simple TPA3116D2 mono board.

 

[Naveenbnc]

In car the low end can sound quite dynamic as explained by Aniket above.
However if it is a hatchback, I would suggest you to stick to sealed 10 inch sub.

Even if a sedan, I would still suggest a sealed sub as you cannot go wrong with it in design if you stick close to the company specs. A sealed enclosure has a natural roll off, though it will demand more power, but most mono blocks in car have enough juice. Even of you are bridging a 4-channel for sub duty, that should be fine.
Also a sealed sub will need a much lesser volume.
If you are going to go with a 2 ohm sub, be sure your amp can drive it.

With ported if you do not get the port properly tuned, there will be bloat in some frequencies.
You can either place the sub facing the boot door or put it facing sideways, avoid it facing towards the front.

Another important thing you need to do it to properly damp the boot doors and the cabin metal with tarfelt sheets like dynamat or any cheaper stuff to arrest door resonance. This is very important.

A very good and informative site for car audio enthuciats
http://www.bcae1.com/

A useful software for designing sub enclosures
https://www.ajdesigner.com/speaker/

I have used some very good subs in my car audio journey.

The Morel Ultimo 12 (considered a holy grail). It was driven by a monster Celestra monoblock
The Infinity Kappa driven bridged by Pioneer 944 amp (an all time favorite of mine)
and now I am two 6.5 inch midbass in a isobaric design due to power constrains in my old car. It is driven by a simple TPA3116D2 mono board.

Dear Kannam, many points to learn and a lot of info
Thank you so much for sharing !!!

 

[Hari Iyer]

As the subwoofer enclosure has limitations to size in your car, check for high compliance drivers sothan you can design a low compliance box of small size. Look for compliance greater than 1mm/ N.

 

[Naveenbnc]

As the subwoofer enclosure has limitations to size in your car, check for high compliance drivers sothan you can design a low compliance box of small size. Look for compliance greater than 1mm/ N.

Dear Hari,
Thats a nice suggestion in driver and box compliance. Thank you very much

 

[Kannan]

There is an advantage in using higher compliance drivers in car apart from the advantage of keeping the enclosure size smaller.

The problem with subwoofers in car is their location, which primarily has to be in the boot, not the most ideal as the midbass drivers are usually mounted at the base of the front doors and the integration becomes difficult unless you have an active DSP with lots of features to adjust crossover, gain, phase etc.

Even in the most airtight door install of midbass (I have seen installs where fabrication has been done to create a dedicated sealed enclosure in doors), it is almost impossible to achieve an inert condition. The doors themselves will resonate and add their own character, how much ever you damp them. I have myself done special fiberglass fabrication with multiple spacers to increase the door depth for midbass in my car by utilizing the cabin space. My doors are very well damped with aluminium backed tarfelt sheets with woolen pads behind the driver to absorbe rear waves.
Here is the pic of the midbass in my car.



Here without the grill



To lower the impact of the high frequency noise perpetrating into the car cabin, some absorbent, diffusion materials and I have also read some cancellation techniques are used to keep the noise to frequencies under 250hz...so usually in cars, with all windows up we usually only hear a kind of rumble. This rumble too adds to the lower midbass and sub frequencies.

So ideally most car midbass drivers will perform poorly if the HPF is under 100hz, and 80hz in well damped doors. Anything below 80 will start to bottom out and bring down the life of the midbass.
So a subwoofer with a lower f/s and a higher Q works favorably in cars as the subs cam be conveniently crossed at 80 with a deeper slope.
Such subwoofers are usually of higher compliance in nature with not that stiff a suspension, so installing then in lower sized box will give a good enclosure air spring to the driver cone.
If you want a bigger enclosure without increasing the size, just add some glasswool, it could though push the F3 a few notch.
if you see commonly, the car subwoofers also have huge magnets.

 

[Hari Iyer]

To avoid all your above issues, I am using a pair of my micro- TL Speakers in my car.

 

[Naveenbnc]

There is an advantage in using higher compliance drivers in car apart from the advantage of keeping the enclosure size smaller.

The problem with subwoofers in car is their location, which primarily has to be in the boot, not the most ideal as the midbass drivers are usually mounted at the base of the front doors and the integration becomes difficult unless you have an active DSP with lots of features to adjust crossover, gain, phase etc.

Even in the most airtight door install of midbass (I have seen installs where fabrication has been done to create a dedicated sealed enclosure in doors), it is almost impossible to achieve an inert condition. The doors themselves will resonate and add their own character, how much ever you damp them. I have myself done special fiberglass fabrication with multiple spacers to increase the door depth for midbass in my car by utilizing the cabin space. My doors are very well damped with aluminium backed tarfelt sheets with woolen pads behind the driver to absorbe rear waves.
Here is the pic of the midbass in my car.

View attachment 29701

Here without the grill

View attachment 29702

To lower the impact of the high frequency noise perpetrating into the car cabin, some absorbent, diffusion materials and I have also read some cancellation techniques are used to keep the noise to frequencies under 250hz...so usually in cars, with all windows up we usually only hear a kind of rumble. This rumble too adds to the lower midbass and sub frequencies.

So ideally most car midbass drivers will perform poorly if the HPF is under 100hz, and 80hz in well damped doors. Anything below 80 will start to bottom out and bring down the life of the midbass.
So a subwoofer with a lower f/s and a higher Q works favorably in cars as the subs cam be conveniently crossed at 80 with a deeper slope.
Such subwoofers are usually of higher compliance in nature with not that stiff a suspension, so installing then in lower sized box will give a good enclosure air spring to the driver cone.
If you want a bigger enclosure without increasing the size, just add some glasswool, it could though push the F3 a few notch.
if you see commonly, the car subwoofers also have huge magnets.

Ooh !!!!
You have put in huge amount of time and efforts on your car audio. Particularly on the doors and other areas.
Now i feel designing and and adding a sub can be done easily. But refinement and balancing the whole system is the real challenge !!! Thank a lot for the pics and explanation

 

[venki7744]

Hi Naveen,

Just my .002 cents, designing subwoofer for car is no different from designing subwoofer for home. However the catch is the room response (aka Cabin gain in car), which is totally different from that of home. Car Audio manufacturers take advantage of this to recommend sub optimal enclosure which usually have a very bad low frequency response (< 50Hz) when played @ say a home environment. However in car due to the cabin gain, the lower Frq gets a boost up to 9 db, if you truly want to design a sub for your car, you would need to measure the cabin gain and design the sub so that LF does not boost too much due to cabin gain. Alternatively you could used published cabin gain as a reference to come up with final FRQ of your enclosure, something like this >> https://goo.gl/images/fFa3jf.

To avoid all your above issues, I am using a pair of my micro- TL Speakers in my car.

Can you share some pictures .

Ooh !!!!
You have put in huge amount of time and efforts on your car audio. Particularly on the doors and other areas.
Now i feel designing and and adding a sub can be done easily. But refinement and balancing the whole system is the real challenge !!! Thank a lot for the pics and explanation

Kannan sire's car is well known among car audio guys .

Cheers,
Venki