"Matt Ion" <soundy106@[EMAIL PROTECTED]
> wrote in message
news:fvp0di$crg$1@[EMAIL PROTECTED]
> Neil Green wrote:
>> "Matt Ion" <soundy106@[EMAIL PROTECTED]
> wrote in message
>> news:fvohu4$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.
I follow.
>
>>> 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.
A job for the weekend, thanks for the advice.
>
>>> 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.
Mine does.
A minus sign displays if the polarity is wrong as you
measure the voltage.
All OK.
<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?
The stock deck was a cassette player (it's a '92 model
car).
We put a Pioneer head unit in, can't remember the
model but all the reviews were good.
>
>>> 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.
No room for a sub I'm afraid, he'll have to live with
less bass or maybe beef up the 7 x 5's in the front
doors and fade more to the front.
Either way he'll have to live with the limitations of
the system.
Thanks very much for your time.
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