Neil Green wrote:
> "Matt Ion" <soundy106@[EMAIL PROTECTED]
> wrote in message
> news:fvohu4$ion$1@[EMAIL PROTECTED]
>> 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)
>
> 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?
Well the "flapping" is likely a result of attempting to get more bass
out of the speakers... solve the bass issue, and the flapping should
take care of itself :) A backless box over the cutout really doesn't
help the problem, as you still get the "leakage" through other cutouts
in the metal.
>> 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.
I'd say that's your first stop then. If possible, use the cardboard
insert as a template to ensure your new insert covers the entire rear
deck - remember, the ultimate goal is no places for air movement between
the top and bottom of the shelf.
>> 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.
A meter won't tell you if the polarity is right. The speakers will be
labeled, the positive terminal probably marked with red and maybe wider
than the other. If you're using the factory wiring, one will PROBABLY
have a larger/wider terminal lug on it. However, if they're the same
size or have had new connectors spliced on to them, you may need to dig
a little deeper.
Is this car running the stock deck as well, or is it an aftermarket deck?
>> 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.
A basic sealed box with an 8" sub will give him nice clean bottom end
without need of massive amounts of amp power. The bass can then be
filtered out of the 6s.
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