"Jay" wrote in message
...
Sorry, that was a bit uninformative..
They weigh about 2 or 3 pounds/piece. They didn't come with back braces,
and they would probably mount ok... my concern is the shock of slamming
over wakes over time, cracking the perimeter...

Get yourself a piece of 3/4" birch ply. Cut a square for each speaker, about
2" bigger than the speaker. Cut your holes in the fiberglass. Make them
perfect. Put the birch ply behind the holes you've made, trace the holes
onto the plywood, and cut holes in that, too. Actually, do that ***BEFORE***
you've cut it into squares. The big piece of ply will be easier to clamp to
a work surface than the smaller squares. Mount the speakers with the wooden
squares as bracing from behind.

One thing you didn't mention: What will be the enclosure BEHIND the
speakers? For any speaker, there's a very small range of correct enclosure
size. Get far from that range and the speaker becomes all but useless in
terms of bass response. Trying to get decent bass by dicking around with
tone controls will just overdrive your radio or amplifier, and blow up your
speakers in short order. Hint: In even the quietest cars, you need about 75
***CLEAN*** watts per channel to overcome road noise. If you intend to run
this stereo in a boat while the engine's running, you need about twice that
much power. Otherwise, you'd better be a big fan of distortion and blown
speakers.

The birch idea sounds good..
Can't say I gave enclosures much though.. sounds like I need to though. .. .

-j


"Doug Kanter" wrote in message
...
"Jay" wrote in message
...
Sorry, that was a bit uninformative..
They weigh about 2 or 3 pounds/piece. They didn't come with back braces,
and they would probably mount ok... my concern is the shock of slamming
over wakes over time, cracking the perimeter...

Get yourself a piece of 3/4" birch ply. Cut a square for each speaker,
about 2" bigger than the speaker. Cut your holes in the fiberglass. Make
them perfect. Put the birch ply behind the holes you've made, trace the
holes onto the plywood, and cut holes in that, too. Actually, do that
***BEFORE*** you've cut it into squares. The big piece of ply will be
easier to clamp to a work surface than the smaller squares. Mount the
speakers with the wooden squares as bracing from behind.

One thing you didn't mention: What will be the enclosure BEHIND the
speakers? For any speaker, there's a very small range of correct enclosure
size. Get far from that range and the speaker becomes all but useless in
terms of bass response. Trying to get decent bass by dicking around with
tone controls will just overdrive your radio or amplifier, and blow up
your speakers in short order. Hint: In even the quietest cars, you need
about 75 ***CLEAN*** watts per channel to overcome road noise. If you
intend to run this stereo in a boat while the engine's running, you need
about twice that much power. Otherwise, you'd better be a big fan of
distortion and blown speakers.

Basic physics: take note of the distance sound leaving the rear surface of
the speaker has to travel through the air to reach the front of the speaker.
Any sound with a wavelength longer that this distance will cancel itself out
as the sound from the front is perfectly out of phase with the sound from
the rear. No bass in other words. An enclosure effectively creates an
infinite distance from front to rear as the two out of phase sound waves
can't get to each other. they are blocked form meeting by the walls of the
enclosure. If the enclosure is too small the speaker ends up using up most
of its power trying to compress the air inside the enclosure resulting in
little low bass as well. So the enclosure has to be both well sealed and
big enough to be effective. It is possible to vent an enclosure with a
tuned port (often called bass reflex) allowing a smaller enclosure but that
isn't simple physics any more...
--
Ken Heaton
Cape Breton Island, Canada
kenheaton AT ess wye dee DOT eastlink DOT ca


"Jay" wrote in message
...
The birch idea sounds good..
Can't say I gave enclosures much though.. sounds like I need to though. ..
..

-j


"Doug Kanter" wrote in message
...
"Jay" wrote in message
...
Sorry, that was a bit uninformative..
They weigh about 2 or 3 pounds/piece. They didn't come with back
braces,
and they would probably mount ok... my concern is the shock of slamming
over wakes over time, cracking the perimeter...

Get yourself a piece of 3/4" birch ply. Cut a square for each speaker,
about 2" bigger than the speaker. Cut your holes in the fiberglass. Make
them perfect. Put the birch ply behind the holes you've made, trace the
holes onto the plywood, and cut holes in that, too. Actually, do that
***BEFORE*** you've cut it into squares. The big piece of ply will be
easier to clamp to a work surface than the smaller squares. Mount the
speakers with the wooden squares as bracing from behind.

One thing you didn't mention: What will be the enclosure BEHIND the
speakers? For any speaker, there's a very small range of correct
enclosure
size. Get far from that range and the speaker becomes all but useless in
terms of bass response. Trying to get decent bass by dicking around with
tone controls will just overdrive your radio or amplifier, and blow up
your speakers in short order. Hint: In even the quietest cars, you need
about 75 ***CLEAN*** watts per channel to overcome road noise. If you
intend to run this stereo in a boat while the engine's running, you need
about twice that much power. Otherwise, you'd better be a big fan of
distortion and blown speakers.

Ken Heaton wrote:
Basic physics: take note of the distance sound leaving the rear surface of
the speaker has to travel through the air to reach the front of the speaker.
Any sound with a wavelength longer that this distance will cancel itself out
as the sound from the front is perfectly out of phase with the sound from
the rear. No bass in other words. An enclosure effectively creates an
infinite distance from front to rear as the two out of phase sound waves
can't get to each other. they are blocked form meeting by the walls of the
enclosure. If the enclosure is too small the speaker ends up using up most
of its power trying to compress the air inside the enclosure resulting in
little low bass as well. So the enclosure has to be both well sealed and
big enough to be effective. It is possible to vent an enclosure with a
tuned port (often called bass reflex) allowing a smaller enclosure but that
isn't simple physics any more...

Good explanation. It also helps to know the wavelengths. Sound travels
about 1127 ft/second in air and wavelength = velocity/frequency so...

freq. wavelength
(Hz) (ft)

20 56
40 28
80 14

"-rick-" wrote in message
...
Ken Heaton wrote:
Basic physics: take note of the distance sound leaving the rear surface
of
the speaker has to travel through the air to reach the front of the
speaker.
Any sound with a wavelength longer that this distance will cancel itself
out
as the sound from the front is perfectly out of phase with the sound from
the rear. No bass in other words. An enclosure effectively creates an
infinite distance from front to rear as the two out of phase sound waves
can't get to each other. they are blocked form meeting by the walls of
the
enclosure. If the enclosure is too small the speaker ends up using up
most
of its power trying to compress the air inside the enclosure resulting in
little low bass as well. So the enclosure has to be both well sealed and
big enough to be effective. It is possible to vent an enclosure with a
tuned port (often called bass reflex) allowing a smaller enclosure but
that
isn't simple physics any more...

Good explanation. It also helps to know the wavelengths. Sound travels
about 1127 ft/second in air and wavelength = velocity/frequency so...

freq. wavelength
(Hz) (ft)

20 56
40 28
80 14


All good points. If he can't build a perfect enclosure, a good ballpark
figure (at least with my experience) is that most car doors are a "pretty
good size" for decent 5" to 6" speakers, assuming they've got at least 10-15
watts of CLEAN power driving them.

"-rick-" wrote in message
...
Ken Heaton wrote:
Basic physics: take note of the distance sound leaving the rear surface
of
the speaker has to travel through the air to reach the front of the
speaker.
Any sound with a wavelength longer that this distance will cancel itself
out
as the sound from the front is perfectly out of phase with the sound from
the rear. No bass in other words. An enclosure effectively creates an
infinite distance from front to rear as the two out of phase sound waves
can't get to each other. they are blocked form meeting by the walls of
the
enclosure. If the enclosure is too small the speaker ends up using up
most
of its power trying to compress the air inside the enclosure resulting in
little low bass as well. So the enclosure has to be both well sealed and
big enough to be effective. It is possible to vent an enclosure with a
tuned port (often called bass reflex) allowing a smaller enclosure but
that
isn't simple physics any more...

Good explanation. It also helps to know the wavelengths. Sound travels
about 1127 ft/second in air and wavelength = velocity/frequency so...

freq. wavelength
(Hz) (ft)

20 56
40 28
80 14


Holy cow. This ain't rocket science folks.

"JimH" wrote in message
...

"-rick-" wrote in message
...
Ken Heaton wrote:
Basic physics: take note of the distance sound leaving the rear surface
of
the speaker has to travel through the air to reach the front of the
speaker.
Any sound with a wavelength longer that this distance will cancel itself
out
as the sound from the front is perfectly out of phase with the sound
from
the rear. No bass in other words. An enclosure effectively creates an
infinite distance from front to rear as the two out of phase sound waves
can't get to each other. they are blocked form meeting by the walls of
the
enclosure. If the enclosure is too small the speaker ends up using up
most
of its power trying to compress the air inside the enclosure resulting
in
little low bass as well. So the enclosure has to be both well sealed
and
big enough to be effective. It is possible to vent an enclosure with a
tuned port (often called bass reflex) allowing a smaller enclosure but
that
isn't simple physics any more...

Good explanation. It also helps to know the wavelengths. Sound travels
about 1127 ft/second in air and wavelength = velocity/frequency so...

freq. wavelength
(Hz) (ft)

20 56
40 28
80 14


Holy cow. This ain't rocket science folks.


Actually, it's *is* science, although it's not always possible to apply it
accurately in cars & boats. You just do the best you can, using the rocket
science as a guideline. And even if you're building freestanding speaker
cabinets for home or stage use, the science assumes a perfect speaker cone
which doesn't add color of its own, which is pretty much fiction. Even so,
the science works.