"Matt Ion" wrote in message
...
Neil Green wrote:
"Matt Ion" wrote in message
...
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)
It's the "flapping" as you call it that's the major
concern for my son, and not the bass response as such.
I could leave the bootom of the box open and place it
over the cutout with some cloth or similar to restrict
the air flow to the back of the cones.
Would that work?
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.
Easily done.
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.
Checked that with a meter, all OK.
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.
I thought as much, but all he really wants is a nice
clean sound without the rumbling.