[Mister.Lull]

Simple question this time.

Will a foreward facing box (ports and driver facing the back seat from
the trunk) run into any problems air-space wise?

Mister.Lull

[MOSFET]

Every situation is different so I think it is nearly impossible to give you
a definitive answer.

But my experience has been that subs that face the rear of the car, instead
of forward towards the back seats, are ALMOST ALWAYS louder.

I believe this is because of cancellation effects. Think about a home
subwoofer. Does it work better sitting in the middle of a room or against a
wall or in a corner? Obviously, against a wall or corner. This is because
bass is omni-directional and the farther you place a sub from a wall or
barrier, the better the chance that reflected sound waves will cancel each
other out.

Example: I had a car once (a long time ago) where I had a custom enclosure
made with two 12" subs facing the back seats, in fact they were nearly
touching the back of the seats. They were in sealed enclosures in the right
amount of airspace for this type of enclosure (they were Soundstream SPL12's
in 1.5 cubic feet of air-space each). The bass sounded OK, but what was
REALLY weird was that when I opened the trunk, the bass (in the driver's
seat) multiplied by four!!!!! Back then, I didn't understand exactly what
was happening, but now I realize that some of the sound waves (which are
omni-directional) were bouncing off the back of the trunk, becoming 180
degrees out of phase, and canceling out some of the sound waves.

Ever since then, I have always experimented with this (just because it
interests me) and have found that it is nearly ALWAYS the case that there is
more bass if the subs face the rear of the trunk or, even better, face the
rear corner of the trunk.

The exception to this would be if you could COMPLETELY ISOLATE the trunk
from the subs so no bass waves could bounce back. This is a little tricky
to do but SPL vehicles do it all the time.

MOSFET
"Mister.Lull" wrote in message
ups.com...
Simple question this time.

Will a foreward facing box (ports and driver facing the back seat from
the trunk) run into any problems air-space wise?

Mister.Lull

[Matt Ion]

MOSFET wrote:

But my experience has been that subs that face the rear of the car, instead
of forward towards the back seats, are ALMOST ALWAYS louder.

I believe this is because of cancellation effects. Think about a home
subwoofer. Does it work better sitting in the middle of a room or against a
wall or in a corner? Obviously, against a wall or corner. This is because
bass is omni-directional and the farther you place a sub from a wall or
barrier, the better the chance that reflected sound waves will cancel each
other out.

Well, Nick, I hate to nit-pick, but you're talking about a phenomenon known as
"boundary reinforcement". You'll actually get MORE chance of cancellation the
closer you move a sub to a wall or corner, because the reflected out-of-phase
waves are that much stronger... but so are the IN-phase waves.

There's a good article on it he
http://www.stereophile.com/features/706deep/index1.html

[MOSFET]

Well, Nick, I hate to nit-pick, but you're talking about a phenomenon
known as
"boundary reinforcement". You'll actually get MORE chance of cancellation
the
closer you move a sub to a wall or corner, because the reflected
out-of-phase
waves are that much stronger... but so are the IN-phase waves.

Well, OK, fine, I'm no engineer. I'm sure you're probably right, Matt, and
thank you for not trying to dazzle us with a whole bunch of acronyms and
terms we don't understand.

And Matt, I DO think this DOES fall under the category of nitpicking because
although you do clarify some things, DOES IT FUNDAMENTALLY CHANGE MY ADVICE?

SHOULD HE FACE THE SUBS TOWARDS THE REAR SEATS?

These are the questions I want you to ask yourself when you respond to my
posts. For instance, I responded to your iRiver post ONLY because what you
said was not good advice (there are cheap pre-amps he can buy for his
iRiver). NOT because you didn't dot your "i" or cross your "t".

Was my post bad advice, Matt? If it is, let's hear it, let's have a debate
and if your argument is stronger I'll happily concede. Otherwise, please
leave my posts alone because this nitpicking (correcting irrelevant details)
is getting REALLY, REALLY OLD (or block me).

Nick

[Matt Ion]

MOSFET wrote:
Well, Nick, I hate to nit-pick, but you're talking about a phenomenon

known as

"boundary reinforcement". You'll actually get MORE chance of cancellation

the

closer you move a sub to a wall or corner, because the reflected

out-of-phase

waves are that much stronger... but so are the IN-phase waves.


Well, OK, fine, I'm no engineer. I'm sure you're probably right, Matt, and
thank you for not trying to dazzle us with a whole bunch of acronyms and
terms we don't understand.

And Matt, I DO think this DOES fall under the category of nitpicking because
although you do clarify some things, DOES IT FUNDAMENTALLY CHANGE MY ADVICE?

What advice? You gave a bunch of anecdotes.

SHOULD HE FACE THE SUBS TOWARDS THE REAR SEATS?

....and your anecdotes don't answer that question. It's worked in YOUR cars,
with YOUR subs... his system may not be affected the same way.

These are the questions I want you to ask yourself when you respond to my
posts.

Yes, mommy. Whatever you say, mommy. You are the boss of me. I am here to
cater only your needs and desires.

Was my post bad advice, Matt?

Not at all. I only pointed out an inaccuracy in your home-subwoofer anaolgy.

and if your argument is stronger I'll happily concede. Otherwise, please
leave my posts alone because this nitpicking (correcting irrelevant details)
is getting REALLY, REALLY OLD (or block me).

You really need to get a grip. IT'S NOT ABOUT YOU. It's about helping the OP.
If your information is inaccurate, that doesn't help.

[MOSFET]

Matt, you are obviously knowledgable when it comes to car audio and I have
learned a lot from you. I don't want to fight with you so PLEASE hear what
I am saying, as a friend.

I do not mind being corrected when I make a fundamental mistake which leads
to bad advice. In fact, I would want ANYONE to correct me if I ever gave
bad advice to someone (and, of course, I HAVE in the past!!). We are here
to help people, first and foremost.

But what you do is different. PLEASE try to hear what I am saying. You
correct terms used incorrectly, concepts not "properly" explained. While to
you, this may SEEM like an important service. And I can certainly see
situations where someone might completely bungle an explanantion of
something and clarification might be needed. But with you it is a constant
barage of small corrections that do not fundamentally change the advice
given. You're like some grade school techer-from-hell whose RIGHT THERE to
rub your nose in the smallest missuse of a term or concept.

Perhaps in your proffesion, this is encouraged. Perhaps it is MANDATORY in
your profession (if you are designing airplane wings, I certainly don't want
ANY mistakes). But this group is for recreation. Car audio is about fun,
Matt. But this constant badgering does not make it fun for me or for other
people who you also badger.

Again, please try to see the difference between getting something
fundamentally wrong like offering bad advice and just using a term
incorrectly. WE ARE NOT DOING ROCKET SCIENCE HERE.

I know you don't give a rat's ass if I block you or not, but I am
considering it and I REALLY don't want to because you are SO KNOWLEDGEABLE
and I can learn from you. I am just hoping you will see my point. This is
about fun. We are not building the hydrogen bomb here.

Thanks,

Nick

[Matt Ion]

Here's some advice back: LIGHTEN UP.

This is rec.audio.car, not rec.audio.car.nick's-ego

Someone disagreeing with you, or correcting you, or in some way contradicting
you, is NOT A PERSONAL ATTACK. DON'T TAKE IT AS SUCH. Everyone is NOT out to
get you!

This may come as a shock to you, but YOU TOO can be wrong now and then. Accept
it, learn from it, and move on. Don't argue it to death.

You didn't create this group, you don't own this group, you don't run this
group. You have no right to tell others how to conduct themselves. If I want
to give someone terse, smart-ass replies, I can. If I want to provide long,
rambling, detail-laden explanations, that's my right too. Just because YOU
don't, can't, or don't want to understand it, doesn't mean someone else doesn't
find the information useful. My methods are not for you to criticize. Neither
are anyone else's.

[Rick Brandt]

Matt Ion wrote:
Here's some advice back: LIGHTEN UP.

This is rec.audio.car, not rec.audio.car.nick's-ego

Someone disagreeing with you, or correcting you, or in some way
contradicting you, is NOT A PERSONAL ATTACK. DON'T TAKE IT AS SUCH. Everyone
is NOT out to get you!

This may come as a shock to you, but YOU TOO can be wrong now and
then. Accept it, learn from it, and move on. Don't argue it to
death.
You didn't create this group, you don't own this group, you don't run
this group. You have no right to tell others how to conduct
themselves. If I want to give someone terse, smart-ass replies, I
can. If I want to provide long, rambling, detail-laden explanations,
that's my right too. Just because YOU don't, can't, or don't want to
understand it, doesn't mean someone else doesn't find the information
useful. My methods are not for you to criticize. Neither are anyone
else's.

One should always remember that newsnet groups are *discussion forums*. You
make a post and a discussion follows. If a question that is asked is eventually
answered that is all fine and good, but it is not the end-all purpose of the
group's existence. Only in moderated groups is the discussion subject to any
one person's whims.

There is no such thing as a hi-jacked thread. When a post isn't of interest to
you, ignore it. When the thread becomes of no interest to you, move on.
Expecting anything else will only aggravate you.

[[email protected]]

What a ****stick you are. Little girly bitch. slap!!!! Such a ****ing
victim.


MOSFET wrote:
Matt, you are obviously knowledgable when it comes to car audio and I have
learned a lot from you. I don't want to fight with you so PLEASE hear what
I am saying, as a friend.

I do not mind being corrected when I make a fundamental mistake which leads
to bad advice. In fact, I would want ANYONE to correct me if I ever gave
bad advice to someone (and, of course, I HAVE in the past!!). We are here
to help people, first and foremost.

But what you do is different. PLEASE try to hear what I am saying. You
correct terms used incorrectly, concepts not "properly" explained. While to
you, this may SEEM like an important service. And I can certainly see
situations where someone might completely bungle an explanantion of
something and clarification might be needed. But with you it is a constant
barage of small corrections that do not fundamentally change the advice
given. You're like some grade school techer-from-hell whose RIGHT THERE to
rub your nose in the smallest missuse of a term or concept.

Perhaps in your proffesion, this is encouraged. Perhaps it is MANDATORY in
your profession (if you are designing airplane wings, I certainly don't want
ANY mistakes). But this group is for recreation. Car audio is about fun,
Matt. But this constant badgering does not make it fun for me or for other
people who you also badger.

Again, please try to see the difference between getting something
fundamentally wrong like offering bad advice and just using a term
incorrectly. WE ARE NOT DOING ROCKET SCIENCE HERE.

I know you don't give a rat's ass if I block you or not, but I am
considering it and I REALLY don't want to because you are SO KNOWLEDGEABLE
and I can learn from you. I am just hoping you will see my point. This is
about fun. We are not building the hydrogen bomb here.

Thanks,

Nick

[MOSFET]

Who is this? Captain?

MOSFET

wrote in message
oups.com...
What a ****stick you are. Little girly bitch. slap!!!! Such a ****ing
victim.


MOSFET wrote:
Matt, you are obviously knowledgable when it comes to car audio and I
have
learned a lot from you. I don't want to fight with you so PLEASE hear
what
I am saying, as a friend.

I do not mind being corrected when I make a fundamental mistake which
leads
to bad advice. In fact, I would want ANYONE to correct me if I ever
gave
bad advice to someone (and, of course, I HAVE in the past!!). We are
here
to help people, first and foremost.

But what you do is different. PLEASE try to hear what I am saying. You
correct terms used incorrectly, concepts not "properly" explained.
While to
you, this may SEEM like an important service. And I can certainly see
situations where someone might completely bungle an explanantion of
something and clarification might be needed. But with you it is a
constant
barage of small corrections that do not fundamentally change the advice
given. You're like some grade school techer-from-hell whose RIGHT THERE
to
rub your nose in the smallest missuse of a term or concept.

Perhaps in your proffesion, this is encouraged. Perhaps it is MANDATORY
in
your profession (if you are designing airplane wings, I certainly don't
want
ANY mistakes). But this group is for recreation. Car audio is about
fun,
Matt. But this constant badgering does not make it fun for me or for
other
people who you also badger.

Again, please try to see the difference between getting something
fundamentally wrong like offering bad advice and just using a term
incorrectly. WE ARE NOT DOING ROCKET SCIENCE HERE.

I know you don't give a rat's ass if I block you or not, but I am
considering it and I REALLY don't want to because you are SO
KNOWLEDGEABLE
and I can learn from you. I am just hoping you will see my point. This
is
about fun. We are not building the hydrogen bomb here.

Thanks,

Nick

[Stephen McLuckie]

Matt Ion wrote:
Well, Nick, I hate to nit-pick, but you're talking about a phenomenon
known as "boundary reinforcement". You'll actually get MORE chance of
cancellation the closer you move a sub to a wall or corner, because
the reflected out-of-phase waves are that much stronger... but so are
the IN-phase waves.

There's a good article on it he
http://www.stereophile.com/features/706deep/index1.html

Have you read this article? For example:

"At low frequencies, the phase difference between these sources becomes
negligible because of the long wavelength, so their outputs combine
constructively. One boundary thereby adds 6dB to the sound-pressure
level, two boundaries add 12dB, and three boundaries add 18dB, assuming
that they reflect perfectly and that the loudspeaker's radiation is
omnidirectional (which at low frequencies is usually the case)." And....

"With a subwoofer we can learn the lesson taught by Roy Allison many
years ago: that if we put the bass driver (and port, if the subwoofer is
reflex-loaded) sufficiently close to as many boundaries as possible, the
boundary lift can be exploited to achieve a smooth overall bass
response." And...

"In the case of fig.2a, the sound source is positioned 3.3' (1m) away
from all three boundaries, as a result of which there are a series of
deep notches in the response beginning at 100Hz. If we move the source
much closer to the corner, so that it is just 9.4" (24cm) from one wall,
7.5" (19cm) from the other, and 4.7" (12cm) up from the floor—distances
that are not unrealistic with a downward-firing subwoofer—we get the
much improved result of fig.2b."

In fact, this article disproves your statement quite nicely. Please look
at fig. 6, the in-room response measurement, and tell me where the
cancellations are.

Stephen

[GregS]

In article , Stephen McLuckie wrote:
Matt Ion wrote:
Well, Nick, I hate to nit-pick, but you're talking about a phenomenon
known as "boundary reinforcement". You'll actually get MORE chance of
cancellation the closer you move a sub to a wall or corner, because
the reflected out-of-phase waves are that much stronger... but so are
the IN-phase waves.

There's a good article on it he
http://www.stereophile.com/features/706deep/index1.html

Have you read this article? For example:

"At low frequencies, the phase difference between these sources becomes
negligible because of the long wavelength, so their outputs combine
constructively. One boundary thereby adds 6dB to the sound-pressure
level, two boundaries add 12dB, and three boundaries add 18dB, assuming
that they reflect perfectly and that the loudspeaker's radiation is
omnidirectional (which at low frequencies is usually the case)." And....

Sounds like somebody added incorrectly. If you add one boundry, it would be 6 dB.
3 Boundries would be 12 dB.

greg


"With a subwoofer we can learn the lesson taught by Roy Allison many
years ago: that if we put the bass driver (and port, if the subwoofer is
reflex-loaded) sufficiently close to as many boundaries as possible, the
boundary lift can be exploited to achieve a smooth overall bass
response." And...

"In the case of fig.2a, the sound source is positioned 3.3' (1m) away
from all three boundaries, as a result of which there are a series of
deep notches in the response beginning at 100Hz. If we move the source
much closer to the corner, so that it is just 9.4" (24cm) from one wall,
7.5" (19cm) from the other, and 4.7" (12cm) up from the floor—distances
that are not unrealistic with a downward-firing subwoofer—we get the
much improved result of fig.2b."

In fact, this article disproves your statement quite nicely. Please look
at fig. 6, the in-room response measurement, and tell me where the
cancellations are.

Stephen

[GregS]

In article , (GregS) wrote:
In article , Stephen
McLuckie wrote:
Matt Ion wrote:
Well, Nick, I hate to nit-pick, but you're talking about a phenomenon
known as "boundary reinforcement". You'll actually get MORE chance of
cancellation the closer you move a sub to a wall or corner, because
the reflected out-of-phase waves are that much stronger... but so are
the IN-phase waves.

There's a good article on it he
http://www.stereophile.com/features/706deep/index1.html

Have you read this article? For example:

"At low frequencies, the phase difference between these sources becomes
negligible because of the long wavelength, so their outputs combine
constructively. One boundary thereby adds 6dB to the sound-pressure
level, two boundaries add 12dB, and three boundaries add 18dB, assuming
that they reflect perfectly and that the loudspeaker's radiation is
omnidirectional (which at low frequencies is usually the case)." And....

Sounds like somebody added incorrectly. If you add one boundry, it would be 6
dB.
3 Boundries would be 12 dB.

It would be really hard or mpossible to cerate more than on boundry, since only
half the output is really being reflected. Getting more than 10 dB in any scenereo
is very difficult, unless its resonance.

greg

[Mister.Lull]

Thank you gentlemen.

Hmmm. Certainly, sub direction is something to think about.

No matter what, I was thinking about blocking off the trunk from the
rest of the car (just with 3/4" MDF, so I realize that bass will still
get through that). I'm getting tired of having an almost un-usable
trunk for fear of damaging some part of the stereo, ya know? But in
order to not have to worry about damaging anything, that means (to me)
a blank, carpeted wall facing the trunk.

Now that only (absolutely) cancels out one of six surfaces on a box.

So it all boils down to the very basic part of the original question
that I didn't articulate very well... regardless of which direction
the sub and ports face (not necessarily the same direction, mind you)
does Air Space outside the box play much of a factor? An example: Say
I decide to go with a downward firing sub and forward facing ports.
The sub would probably only have one inch of clearance (sub poised 1
inch above the floor of the trunk [already cut off from the rest of the
trunk, snugged up next to the back seats]), is that enough space or
will that somehow mess with the sound or volume of the bass?

~Mister.Lull
MOSFET wrote:
Every situation is different so I think it is nearly impossible to give you
a definitive answer.

But my experience has been that subs that face the rear of the car, instead
of forward towards the back seats, are ALMOST ALWAYS louder.

I believe this is because of cancellation effects. Think about a home
subwoofer. Does it work better sitting in the middle of a room or against a
wall or in a corner? Obviously, against a wall or corner. This is because
bass is omni-directional and the farther you place a sub from a wall or
barrier, the better the chance that reflected sound waves will cancel each
other out.

Example: I had a car once (a long time ago) where I had a custom enclosure
made with two 12" subs facing the back seats, in fact they were nearly
touching the back of the seats. They were in sealed enclosures in the right
amount of airspace for this type of enclosure (they were Soundstream SPL12's
in 1.5 cubic feet of air-space each). The bass sounded OK, but what was
REALLY weird was that when I opened the trunk, the bass (in the driver's
seat) multiplied by four!!!!! Back then, I didn't understand exactly what
was happening, but now I realize that some of the sound waves (which are
omni-directional) were bouncing off the back of the trunk, becoming 180
degrees out of phase, and canceling out some of the sound waves.

Ever since then, I have always experimented with this (just because it
interests me) and have found that it is nearly ALWAYS the case that there is
more bass if the subs face the rear of the trunk or, even better, face the
rear corner of the trunk.

The exception to this would be if you could COMPLETELY ISOLATE the trunk
from the subs so no bass waves could bounce back. This is a little tricky
to do but SPL vehicles do it all the time.

MOSFET
"Mister.Lull" wrote in message
ups.com...
Simple question this time.

Will a foreward facing box (ports and driver facing the back seat from
the trunk) run into any problems air-space wise?

Mister.Lull

[Matt Ion]

Mister.Lull wrote:

So it all boils down to the very basic part of the original question
that I didn't articulate very well... regardless of which direction
the sub and ports face (not necessarily the same direction, mind you)
does Air Space outside the box play much of a factor? An example: Say
I decide to go with a downward firing sub and forward facing ports.
The sub would probably only have one inch of clearance (sub poised 1
inch above the floor of the trunk [already cut off from the rest of the
trunk, snugged up next to the back seats]), is that enough space or
will that somehow mess with the sound or volume of the bass?

The thing about bass in a car is, there's a lot of voodoo involved... you can
calculate some of the factors, but some things just aren't quantifiable.
Certainly the airspace in the trunk, and indeed the rest of the car, are a part
of the whole subwooder *system*. It all affects the bass response, usually in
ways that you can only determine yourself, once the box is in the car. What
works in one car may work in yours, or it may not. Google the term "transfer
function" (WITH the quotes) for more details.

Even the SHAPE of your trunk/hatch/etc. can play a role - those guys back in
high school (well, when I was in high school anyway) who got nice pounding bass
from the 6x9s in the rear deck of their Trans Ams were (usually unknowingly)
taking advantage of the curve of the rear window, which effectively horn-loaded
the speakers and created a reinforced sound wave; it's a principle used a lot in
live-sound reinforcement to get a lot of sound out of a small package.

Basically, you need to experiment with it once the box is in, to find out what
works best FOR YOU.

[[email protected]]

Matt Ion wrote:

Even the SHAPE of your trunk/hatch/etc. can play a role - those guys back in
high school (well, when I was in high school anyway) who got nice pounding bass
from the 6x9s in the rear deck of their Trans Ams were (usually unknowingly)
taking advantage of the curve of the rear window, which effectively horn-loaded
the speakers and created a reinforced sound wave; it's a principle used a lot in
live-sound reinforcement to get a lot of sound out of a small package.

hee-hee. i second that! ever been in a volkswagen beetle with a
couple 6x9's in the back aimed straight up? that round backwindow and
rounded roof make one heck of a means for waves to follow.

vee-dubs... mmm, mmm, mmm

:~)

[Matt Ion]

wrote:
Matt Ion wrote:


Even the SHAPE of your trunk/hatch/etc. can play a role - those guys back in
high school (well, when I was in high school anyway) who got nice pounding bass
from the 6x9s in the rear deck of their Trans Ams were (usually unknowingly)
taking advantage of the curve of the rear window, which effectively horn-loaded
the speakers and created a reinforced sound wave; it's a principle used a lot in
live-sound reinforcement to get a lot of sound out of a small package.


hee-hee. i second that! ever been in a volkswagen beetle with a
couple 6x9's in the back aimed straight up? that round backwindow and
rounded roof make one heck of a means for waves to follow.

vee-dubs... mmm, mmm, mmm

Oh yeah, and just to clarify: it's NOT necessarily "good" sound when you do this
- just as some frequencies are reinforced, others are cancelled - it's by no
means ACCURATE sound, but it's a useful design when pure SPL is more critical
than accuracy (like in a concert system). It makes for some impressive thump in
the car, but it ain't gonna win you points on the RTA