Neil Green wrote:
> "Matt Ion" <soundy106@[EMAIL PROTECTED]
> wrote in message
> news:fvof11$8ee$1@[EMAIL PROTECTED]
>> Neil Green wrote:
>>> Hi all
>>> My son bought some 6" Kenwood speakers from a local
>>> shop, not cheapies, and we installed them on the
>>> rear parcel shelf of his car on Sunday.
>>> If we crank the volume (to around 75%) and bass up
>>> the distortion is really severe.
>>> You can see the cones bouncing up and down and they
>>> make a vibrating sound which is very unpleasant so
>>> he has to either lower the volume of reduce the
>>> bass to eliminate this noise.
>>> What I'd like to know is if this effect is just a
>>> limitation of 6" speakers or whether the speakers
>>> themselves aren't up to par or if there's any way
>>> of reducing this distortion to acceptable levels.
>>> Would housing the speakers in boxes placed above
>>> the shelf help?
>>> Thanks
>>> Neil.
>> What sort of car? What sort of parcel shelf?
>> Without the speakers being mounted in a solid
>> baffle, you'll lose some bass production simply
>> through cancellation.
>
> It's a Nissan sedan, the parcel shelf has cutouts in
> the steel for the original speakers which suit the 6"
> Kenwoods.
> It also has a fabric covered composite board insert
> over the steel shelf.
> I thouhjt I could make some MDF boxes and mount them
> on top of the shelf, but if that doesn't reduce the
> distortion it will be a waste of time.
>
>> Most 6" speakers won't produce a lot of bass to
>> begin with, but proper mounting will produce a
>> better bass response and you won't need to crank the
>> bass knob as much.
>
> So is it worth making the boxes?
> I was thinking 12mm MDF, and paint them matt black.
Those type of speakers are generally designed for an "infinite baffle"
type setup, meaning they're not intended to have a box behind them.
It'll work, and probably get rid of most of the "flapping" of the cones,
but it won't really give you much better bass response simply by the
lack of air behind the speakers. (see
http://www.the12volt.com/caraudio/boxes1.asp)
The problem you have is that there are probably other cutouts in that
steel deck, and the cardboard panel (since that's really what it is,
just stiff cardboard) over it is effectively "transparent" to most of
the bass frequencies, so the mounting location has limited usefulness as
a baffle. The ideal solution for using those speakers would be to build
a more solid deck to replace or complement the cardboard insert. Even
1/4" (6mm) MDF would be a significant improvement.
One other thing you want to check is the speaker phase - make sure both
+ terminals in the wiring are connected to the appropriate + terminal on
each speaker. If the speakers are out of phase with each other (+/-
reversed), the two cones will be working against each other and
canceling bass that way.
Ultimately, you want a separate sub and amp to get any sort of decent
bass - 6" speakers like that simply aren't designed to move a lot of
air, and most decks don't produce the power to move them very much.
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