Car Audio attracts the most ignorant people/RANT

exalted512

Mazeroth wrote:

nesticle, go sealed. The cabin gain will make up for the sealed sub's response drop and give you a pretty flat response. A ported sub's tuning frequency will get overcompensated with the cabin gain and sound like poo poo.

common misconception in car audio
-Cody

Mazeroth

exalted512 wrote:

common misconception in car audio
-Cody

Ummm...not really.

Vented subs inside a car are only OK if some care is taken to equalise the otherwise peaky resulting response. Examples:

- Low (below 35Hz) tuning inside big lossy cabins, like vans with a lot of seats and weak wall and ceiling frames.
- Low tuning with high efficiency, low Qts and high Fs drivers (from PA, rarely seen on car-audio) mounted in undersized boxes, resulting in a smooth in-car frequency response.
- Active equalisation involving a little (-6dB or so) notch tuned slightly above the tuning frequency, usually at 45Hz.
-6th bandpass enclosures designed in such a way that the front chamber provides more boost at high bass frequencies that the rear chamber provides in the low end (inside the car).
-Vented boxes undersized and intentionally tuned to have a low Q (around 3). That's usually achieved just by placing a vent in a corner with relatively small cross-sectional area. Such a vent provides very little gain (1dB or so) and thus sealed-like frequency response, but it improves power handling dramatically as cone excursion is usually reduced by more than 50% across a quite wide frequency range (around port tuning).

Of course, the usual "brute-force" bass reflex tuning practices are not suitable for in-car use because they result in a sort of peaky bass quite frustrating.

I've found cabin gain to usually be about 8-9dB/Oct starting around 60-90Hz depending on car, big cars start lower. because of this I find sealed boxes tend to work better generally but ported can work well if designed with this response in mind, which they rarely are. The best bet is if you want a lower hitting sub just build a large, sealed sub. Going ported is usually not recommended unless you want one note bass for rap.

karpiel666

All I have to say is that I have a 60$ 250watt 12inch infinity woofer in a 30$ sealed box powered by a 50$ 250 watt amp. The installers set it up horribly, and this was at frys. The rating on the woofer are 250 watt rms 1230 peak:rolleyes: and the amp is 250x2 or 500 bridged rms with peak of 1000. They had it set up bridged I found it hard to believe that professional installers were as ignorant as that, particularly at frys. My car system is crap but it makes me happy when people realize that a properly setup 170$ installed sub in a minivan trounces thier 5000$ dual 15'' setup in a 89 accord.

exalted512

Mazeroth wrote:

Ummm...not really.

Vented subs inside a car are only OK if some care is taken to equalise the otherwise peaky resulting response. Examples:

- Low (below 35Hz) tuning inside big lossy cabins, like vans with a lot of seats and weak wall and ceiling frames.
- Low tuning with high efficiency, low Qts and high Fs drivers (from PA, rarely seen on car-audio) mounted in undersized boxes, resulting in a smooth in-car frequency response.
- Active equalisation involving a little (-6dB or so) notch tuned slightly above the tuning frequency, usually at 45Hz.
-6th bandpass enclosures designed in such a way that the front chamber provides more boost at high bass frequencies that the rear chamber provides in the low end (inside the car).
-Vented boxes undersized and intentionally tuned to have a low Q (around 3). That's usually achieved just by placing a vent in a corner with relatively small cross-sectional area. Such a vent provides very little gain (1dB or so) and thus sealed-like frequency response, but it improves power handling dramatically as cone excursion is usually reduced by more than 50% across a quite wide frequency range (around port tuning).

Of course, the usual "brute-force" bass reflex tuning practices are not suitable for in-car use because they result in a sort of peaky bass quite frustrating.

I've found cabin gain to usually be about 8-9dB/Oct starting around 60-90Hz depending on car, big cars start lower. because of this I find sealed boxes tend to work better generally but ported can work well if designed with this response in mind, which they rarely are. The best bet is if you want a lower hitting sub just build a large, sealed sub. Going ported is usually not recommended unless you want one note bass for rap.

in low tuned ported boxes, say 28-35Hz, which is low for car audio, the peak in the frequency spectrum actually evens out the effect of cabin gain. Cabin gain, as you know, only happens in a small region of the subwoofer realm, and a lot of the time sealed boxes peak where cabin gain peaks, causing up to a 6 -9dB gain in the frequnecy spectrum. Ported boxes, like you said, if done right, sound better than sealed boxes.
-Cody

nesticle

Its good to hear that others have heard or have an ID sub, and if it makes any difference I drive a 94 VW Jetta. Right now my subs face the rear and so do the ports. I'm hoping to build the new single sub box to fit in the side, behind the rear wheel well. Also, the part that seperates part of the trunk from the cabin is very sound transparent. Its mostly foam and carpeting, and if the base goes high enough it'll shake. Would that make any difference in allowing low frequencies into the cabin?

riglehart

Best car stereo I have ever heard was my Volkswagen GTI in the late 80s. I had a pretty good kenwood amp on an alpine deck and Polk monitor 5's in the hatch back. You talk about filling a room with GOOD sound....

MacLeod

I agree with Cody that a ported box can be made to sound just as good as anything else.

The problem I have with them is theyre a little trickier to get tuned right and they are less forgiving of design and/or construction flaws as opposed to a sealed box.

nesticle

Polk Monitor 5's in the trunk.... I just might try that