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Old 3rd August 2011, 00:42   #1
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Arrow Does a car tuning frequency play a role with sub-box design

I have a 15" sub in a box with following specifications.



I want to make my sub play as flat in cabin as possible , with respectable amount of punch and ability to play t to 100hz easily.

I decided to tune it at 33 hz and decreased the port length.The box can really move some air , but i miss out my 10"/8" sub warmth .

I have tried various different configurations passing it at 80hz at 12db slope, at 63 at 6/12db also at 50 and lower with 6/12db slopes . subsonic is at 25hz and ts being powered by a blaupunkt vpa 1500pro mono amplifier , which delivers 1500rms@ 1 ohms .

I can change the port length to vary the tuning but i once read it on Hertz mille subwoofer manual , that if its a slot port box and the port is along the wall then , we have to keep it 30% shorter then calculated to achieve the tuning frequency ! else it gets tuned even lower - well it makes perfect sense!

If i go by hertz audio suggestion - it means my current box is also tuned much lower than what i intended it to be. I also wanted to tune it to 35hz but was scared to make my sub bottom out at tracks having below 35hz content , which is play at time to move some serious air. The sub is AA havoc 15" rated 1250rms , an excellent SQ sub by the way !

my question is - does the car cabin tuning frequency ( not the box ) play a role with a box design , for it to play flat in car cabin ?

If yes, can anyone explain how to achieve it ?

Last edited by amangujral06 : 3rd August 2011 at 00:47.
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Old 3rd August 2011, 10:21   #2
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Default Re: Does a car tuning frequency play a role with sub-box design

Hi

Excursion below resonance can be controlled with subsonic filters.

Depending on what kind of music you listen to you may be able to get away with a high enough cutoff frequency.

If you assume the cabin is the room you will get a second resonance at each of its modal frequencies. Unfortunately this is detrimental so if you rely on that to tune your bass output you will suffer at other frequencies. Remember modes create both resonant and suckout zones.

One way to avoid all of this nonsense is to use multiple, small woofers (not really feasible in a car), or a smaller than optimal sub with a high enough Fb. Another way is to use a sealed box. Assuming that's not to your taste?
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Old 3rd August 2011, 10:41   #3
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Default Re: Does a car tuning frequency play a role with sub-box design

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Originally Posted by amangujral06 View Post
I also wanted to tune it to 35hz but was scared to make my sub bottom out at tracks having below 35hz content...my question is - does the car cabin tuning frequency ( not the box ) play a role with a box design , for it to play flat in car cabin ?
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Originally Posted by cranky View Post
Depending on what kind of music you listen to you may be able to get away with a high enough cutoff frequency.

If you assume the cabin is the room you will get a second resonance at each of its modal frequencies. ...use multiple, small woofers (not really feasible in a car), or a smaller than optimal sub with a high enough Fb. Another way is to use a sealed box.
Aman, firstly like Cranky said above the subsonic filter will ensure the woofer is not being pushed too hard.

Cranky, for the multiple woofers theory you stated to work they have to be in different locations which as you correctly stated is a bit diffcult to do in a car unless you are doing some serious modictions to the car's interior.

Lastly one option is to use multiple (given your assumed SPL needs I'd say 3) 10" woofers with a Fb that is high enough to provide the small band of bass you need. A sealed box will protect these subs from being overdriven.

Alternately a bandpass sub can work (if you dont need a very tight bass) but it would require careful tuning (which is a lot of work for bandpass).

Last edited by navin : 3rd August 2011 at 10:42.
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Old 4th August 2011, 00:00   #4
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Default Re: Does a car tuning frequency play a role with sub-box design

In real world , i have seen subs ( including mine) bottoming out , with the voice coil slap, even with subsonic filter on . So subsonic filters aren't full proof.

A simple song like - basstronic - bass i love you , had made every subwoofer in ported box bottom out at respected rated power, that i had tested it on, with subsonic filter anywhere between 25-30hz . This music track has notes down to 14hz, nobody tunes there boxes that low.

But that is not even my main concern . My concern is to get those upper ocatves from 60-100hz that are most affected with current tuning of my box. To somehow make my sub play as flat as possible from 30hz to 100 hz in car.

Is that because of the hertz suggestion i read ? my slot port is along the wall, so does it my mean my box might have been tuned even lower ?
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Old 4th August 2011, 10:29   #5
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Default Re: Does a car tuning frequency play a role with sub-box design

Quote:
Originally Posted by amangujral06 View Post
My concern is to get those upper ocatves from 60-100hz that are most affected with current tuning of my box. To somehow make my sub play as flat as possible from 30hz to 100 hz in car.

Is that because of the hertz suggestion i read ? my slot port is along the wall, so does it my mean my box might have been tuned even lower ?
Your best option is to go sealed or dump a cotton sock in the port and make it an Aperiodic vent instead. The later option wont cost you much 'cept a few old socks. Try it.
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Old 4th August 2011, 12:48   #6
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Default Re: Does a car tuning frequency play a role with sub-box design

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Your best option is to go sealed or dump a cotton sock in the port and make it an Aperiodic vent instead. The later option wont cost you much 'cept a few old socks. Try it.
Navin Ji it is slot port not a round one. He will need to put a towel I think !!!
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Old 4th August 2011, 16:30   #7
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Default Re: Does a car tuning frequency play a role with sub-box design

Quote:
So subsonic filters aren't full proof.
If your filter slope is low enough (say, 6dB/oct) it will be ineffective.

The filter implementation needs to be correct to work correctly.

Sealed boxes have no problem with excursion below resonance for a correctly sized box.
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Old 9th August 2011, 12:13   #8
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Default Re: Does a car tuning frequency play a role with sub-box design

Please remove the post !!!
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