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msmith wrote:

Tom... In this particular case, it's not fair to dismiss Eddie as a
silly, uneducated, myth-propagating dummy.

I've never done that Manville if you've been following the thread you'll have
noticed that this started when Eddie attacked me, quite impolitely, for
pointing out that his 'explantation' of low frequency acoustics in a car didn't
fit with acoustical reality. But he's respomnded in exactly the way you
describe above.

Anyone who has installed more than a few real-world car subwoofers
knows that subwoofer orientation/loading has an effect on the quality
and quantity of perceived bass at the listening position.

Boundary loading is a different issue and Eddie doesn't seem to recognize or
discuss it. As far a orinetation goes this is a function of vehicle size and
frequency range.

The
significance of the effect varies from car to car, but it is definitely
an important factor.

Depending on frequency range. The 'idea that opening a hatch "increases" bass
in the car, when it may introduce a peak but radically reduce lower frequency
sound pressure in the cabin, is largely a myth and that woofer-face direction
changes frequency response below the lowest modal frequency in the cabin is
another.

Be that as it may location/orientation is a useful tool but we need to
understand how and why. Eddie has a simplistic veiw that he won't let go of no
matter what.

So instead of discussing things rationally he simply blusters.

In fact, one of the primary "tuning" aspects of designing Stealthbox
systems (vehicle specific subwoofers) here at JL Audio revolves around
finding an optimum location, orientation and loading for the woofer. I
wish it were as simple as just picking any spot in the car for the sub,
but it isn't. Sometimes a location that is more practical or desirable
doesn't sound as good as another.

Of course; but if you'll recall in 1999 I tested 4 vehicle specific subwoofer
systems (one of which was a JL) in a '99 Sierra for Car Stereo Review and 4
different systems with different woofer face orientation in 2 differing
radiating locations showed that below 60 Hz the cabin transfer function was
identical.

That's the only question here.

Quoting Beranek, or citing physics that contradict these observations
is like saying that a rainbow does not actually have multiple colors in
it.

This came from an earlier discussion where Eddie claimed that his single wall
'cartoon' was a standing wave phenomenon when in fact it was just a single
boundary interference which wouldn't occur at the input frequency but well
above it.

A car is not a square room, nor is it a uniform pressure vessel...
orientation and proximity to boundaries (loading) has an effect on the
acoustical impedance matching between the woofer and the listening
environment... Partially sealed trunks act as resonant chambers which
often cancel out desirable bass energy...
small, semi-captive volumes
of air between a rear-firing sub and a rear hatch affect the acoustical
impedance match as well... the relationship between the listening
position and the front and back boundaries of the cabin also plays a
role... the vehicle is lossy at very low freuqencies... etc. etc. etc.

So? The possible problems that are encountered in any given situation do not
affect the acoustical issues here. Of course there are a multitude of possible
effects BUT simply moving a woofer to a diferent location is not a end-all
solution. And it's very misleading to insist that it has any effect below the
modal range in a car.

An understanding of what, how and why is useful. But Eddie simply wants to hurl
insults for the most part or offer misguided discussion about what happens and
why.

It should also be noted that 99.9% of car audio customers listen to
bass at louder levels than you find comfortable... I'm not sure if that
fact has any effect on the whole equation.

Bass at louder levels is not an issue. Louder SPL at higher frequencies is.

As far as I know, nobody has been able to accurately model a car's
transfer function based on pure measurements with any degree of
precision... one can measure it, but it is devilishly complicated to
predict.

Depends on the frequency range in question. I can measure the low frequency
transfer function at frequencies below the lowest modal frequency with great
reliability. It's true that there is great variation above this frequency (60
Hz in a Corvette or Sierra X-cab, for example) but in the pressure zone it's
quite reliably measured if not predictable in advance.

This is not the issue here. I've never said that location/orientation isn't
important. I'm just trying to outline how and where it can be used to benefit.

But Eddie just wants to defend his web-site and hopefully discredit anyone who
might show he's wrong about some things.

Maybe some of your OEM buddies think they have the answer, but
I have my doubts.

Manville Smith
JL Audio, Inc.

I agree that no one that I know can model an acoustical transfer fucntion prior
to manufacturing a cabin. But nobody even tries. The audio system comes after
and is adapted to the car just as a home audio system is adapted to the room in
which it will be used.

But, on the whole, Eddie is not advancing the discussion on helping everyone
make better sounding car audio systems.