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-   -   What Q box to match car room gain? (http://www.diyaudio.com/forums/car-audio/36062-what-q-box-match-car-room-gain.html)

Matttcattt 14th June 2004 09:28 PM

What Q box to match car room gain?
 
What sort of Q box would I want for my sub (Adire Tempest) so that it matches the room gain in my car (Ford Fiesta if that helps).

I guessing quite a low Q, as the room gain in a car seems to be massive.

tool49 16th June 2004 05:08 AM

No car is exactly the same but the usual assumption is that a car cabin offers 12db/octave of boost down 3db at 70Hz so you can probably get away with a Q of .707 centered around 70-75Hz. The thing is that most people find "flat" bass in a car too thin, so you can up the Q quite a bit and get more punch around 90Hz (where the chest thump is felt)

My liking in that department is 0.900 or so around 60Hz with little to no equing.

Hope this helps!
Sébastien

Matttcattt 16th June 2004 10:10 AM

Quote:

Originally posted by tool49
No car is exactly the same but the usual assumption is that a car cabin offers 12db/octave of boost down 3db at 70Hz so you can probably get away with a Q of .707 centered around 70-75Hz. The thing is that most people find "flat" bass in a car too thin, so you can up the Q quite a bit and get more punch around 90Hz (where the chest thump is felt)

My liking in that department is 0.900 or so around 60Hz with little to no equing.

Hope this helps!
Sébastien

Im thinking of using the Linkwitz Transform to adjust the F3 point and the Q so I just need to experiment really, and find out what I like best. I like low bass, so ill probably try an F3 point of about 30Hz, with a low Q of about 0.5 so it hopefuly wont have too much of a peak.

richie00boy 16th June 2004 12:36 PM

:eek: Tempest in a Fiesta!!! 10 inches would be OK for that, and a heck of a lot cheaper and smaller.

As mentioned, there is no set Q for a car interior. I would expect a Fiesta to have a high-Q response as it's not well damped, so to match properly you need a low-Q sub.

As a rule of thumb, take the longest dimension of the cabin and that will be the wavelength where room gain begins. You usually need an additional 6dB boost or so to make up for road noise, or just use some of the room gain to give you your boost.

Frequency = 344 / Dimension (in m)

Matttcattt 16th June 2004 02:08 PM

Quote:

Originally posted by richie00boy
:eek: Tempest in a Fiesta!!! 10 inches would be OK for that, and a heck of a lot cheaper and smaller.

As mentioned, there is no set Q for a car interior. I would expect a Fiesta to have a high-Q response as it's not well damped, so to match properly you need a low-Q sub.

As a rule of thumb, take the longest dimension of the cabin and that will be the wavelength where room gain begins. You usually need an additional 6dB boost or so to make up for road noise, or just use some of the room gain to give you your boost.

Frequency = 344 / Dimension (in m)

I like to go OTT. I want to reach <20Hz. I may use a Tumult if I can afford one...

Thanks for the formulae.

tsmith1315 16th June 2004 03:01 PM

Matttcattt wrote:

Quote:

I like to go OTT. I want to reach <20Hz. I may use a Tumult if I can afford one...
The best LF extension I heard in my car audio days consistently came from IB subs.

Tim

Matttcattt 16th June 2004 04:02 PM

Quote:

Originally posted by tsmith1315
Matttcattt wrote:



The best LF extension I heard in my car audio days consistently came from IB subs.

Tim

You wouldnt get a very infinite baffle in a car... Or do you mean mounted in the parcel shelf?

richie00boy 16th June 2004 05:59 PM

I think he means a sealed box. Which you would have no option but to use if you intend on using a Tempest in a Fiesta.

I do hope you are going to do something decent with the sound from the front of the car, i.e. bass-mid and treble of suitable quantity and quality to match the Tempest, else it will be quite a novelty at first but soon become tiring.

S.C 16th June 2004 07:12 PM

WoW If you could do something like this will be cool !http://www.jlaudio.com/stealthbox/f150_console.html#

Matttcattt 16th June 2004 08:06 PM

Quote:

Originally posted by richie00boy
I think he means a sealed box. Which you would have no option but to use if you intend on using a Tempest in a Fiesta.

I do hope you are going to do something decent with the sound from the front of the car, i.e. bass-mid and treble of suitable quantity and quality to match the Tempest, else it will be quite a novelty at first but soon become tiring.

Yes, there is going to be a whole "system" when I can afford it, I cant just have a hugely expensive subwoofer and keep the factory speakers.


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