specific model/motor? complete t/s parameters?
dafobbishon3
10+ year member
CarAudio.com Elite
type of music you listen to?
lord baccus
10+ year member
Member
Fs = 41 Hz
Qms = 9.8
Vas = 1.6 cu.ft
Qes = 1.1
Re = 1.98 ohms
Qts = 1
1-W SPL = 86.5 dB
my suggestion is read this //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Qms = 9.8
Vas = 1.6 cu.ft
Qes = 1.1
Re = 1.98 ohms
Qts = 1
1-W SPL = 86.5 dB
my suggestion is read this //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
lord baccus
10+ year member
Member
S.P.L.: Theories and Tips
Now its time for the fun stuff, the coolest thing about this industry is the ability to
create a sonic discharge potent enough to shake foundations, tear metal, and set off car
alarms for a mile. So how do you make one 15” subwoofer produce 150dB+?
The evolution of SPL has taken place at a geometric rate. The reality is this; more
progress has taken place in subwoofer and amplifier design in the last 10 years than in
the 60 years before it. Those who have been following the industry for more than the
last decade can remember the “more is more” period of competition. In this golden age,
it was common to see large numbers of drivers with high current amplifiers. It was
during this time the “wall” became popular 5, 10, or 64 drivers in sealed enclosures
(individual chambers of course), and running off the lowest number of amps possible.
This was due to fact that classes were divided by rated power at 4 ohms. This was the
heyday of the high current amplifier. The most sought after bass amps were still class
A/B. Who doesn’t want a 25w x 2 amplifier that was 400wrms at ½ ohm mono or
200wrms at ¼ ohm stereo? Of course, you could cook on them at full volume, not to
mention they could drain a tractor battery to 10 volts in seconds. Nevertheless, the
numbers were impressive. Well if you’re satisfied with a 140’s with six 15’s behind your
head, help yourself.
Soon after this indulgence of more subs = more sound thinking, manufacturers
began performing a mechanical overhaul (necessity is the mother of invention…). Up
until now, subwoofers still looked and responded like their PA cousins, smaller motor
structures, voice coils, spiders, and low excursion were the Achilles tendon of
performance. Though they had a high sensitivity rating, they lacked power handling, the
suspensions were outdated, and true high excursion didn’t exist. Subwoofer design
went back to the drawing board to be revamped from top to bottom. Several companies
began offering subwoofers that could handle much higher wattage (1000wrms+),
suspension compliance was modified for long throw woofers that could function in
oversized ported enclosures, long excursion woofers with linear travel began to appear,
and cone materials changed to allow for stronger cone assemblies. These revolutions
lead to the death of pole piece venting as we knew it, the ultimate heat dissipating
innovation, Cross Vent™ cooling was its replacement. Next, we grew the diameter of
the voice coil improving heat dissipation even more, and more heat dissipation meant
more reliable power handling.
Then the final tumblers fell into place…the class D amplifier was designed,
engineered, and released. More power was finally available, more power than ever
available before. Enclosure design was reworked to produce huge gains in sensitivity
(10dB+). Finally science took center stage; less drivers equals less phasing issues; less
phasing issues = less cancellation; less cancellation = more output. Larger port size
increases the total radiating surface. Hitting the microphone with the peak of the wave
registers more output. This meant determining the wavelength and building an
enclosure to suit. Port placement and subwoofer placement began to be serious
concerns where in the past the idea was that it didn’t matter, because systems were
“pressurizing the entire cab”; not taking into consideration the idea of cancellation and its
effects on total measurable output. With this tutorial we will try to unravel some of the
mystery involved in creating monster bass. Moreover, Oz audio is proud to be able to
deliver innovative technology to the competitor and dealer alike through state-of-the-art
subwoofers and amplifiers. So if you are ready to wield this knowledge, continue on.
Increasing Displacement:
As you already know, you cannot physically make your subwoofer larger, but you
can increase the radiating area by increasing port area.
The first illustration represents a subwoofer in a sealed (acoustical suspension)
cabinet and you can see the appreciable output. This type of performance would be
considered normal output. The drawback of this subwoofer system is the output is
limited by both cone displacement (surface area of the cone x excursion) and power
handling. Really, the only way to get more output would be to add another driver (more
$ and may lead to phasing issues) or more power until you reach the maximum power
rating, after that you risk damaging the woofer through thermal saturation or over-driving.
This type of power can result in torn spiders, broken cones, or damaged voice coils.
Even though this design is practical for everyday listening, it is not the first choice for
unlimited SPL.
Meanwhile, in the second illustration, we are displaying your prototypical oversized
ported (bass-reflex) cabinet. Here you can see at the desired frequency (Fb), the output
from the subwoofer and the port are in phase, improving the subwoofer systems output
by roughly double (+3dB gain). Something that is not seen in this illustration is that near
the desired frequency (Fb) there is minimal cone movement due the large amount of
support being supplied to the backside of the subwoofer. Because of this phenomenon,
power handling is increased. This also minimizes the chances of overdriving the woofer,
unless the driver is grossly overpowered, or is forced to play below the vent tuning (see
Bass Reflex; Pro’s and Con’s).
As discussed in earlier tutorials, bandwidth is traded for sensitivity; this is true with
SPL enclosures as well. As the port area increases (and increasing total volume as a
result), the bandwidth will shrink. Although this is less favorable when building a
subwoofer system for “everyday listening” it is irrelevant in SPL, this is one of the rare
situations that a one-note bass cabinet is necessary. For maximum output, optimum
sensitivity and radiating displacement are priority one. So what does this all mean?
Here in the recommended “SQ” enclosure the response is very flat, very wide, and
with moderate gain (+1.22dB).
Here is the response curve of a Power 15 in a SPL enclosure, notice the radical
peak; this represents a gain of 12.4dB or roughly 16 times the output! Notice the narrow
bandwidth; how the output is dramatically reduced on the left or right of the Fb. Without
increasing the number of Power 15’s we increased our radiating area from 129in2 (cone
area of one Power 15) to 329in2 (port area + cone area). Of course, there are limitations
to these designs, but the limits are determined by the subwoofers ability to interact with
the enclosure. The subwoofers suspension has to be tough enough to control the
driver’s motion in a massive vented and to support a vent this size. As a rule of thumb,
most high performance woofers will support up to one-half of their cone displacement in
vent displacement. SPL subwoofers (Power 15.1 and 12.1) can sustain in excess of 2x
their cone displacement.
What’s next? Making sure all of the output (or as much as we can) reaches the
microphone.
Traveling at the Speed of Sound:
Everyone has heard the terms, cycles-per-second, frequency/freq, Hz/hertz (not the
rental company), sine wave, and wavelength. However, few understand what they
signify.
If we break the audio path down into its most basic parts, we could remove one sound
wave for examination, as in the illustration. Audio signal is represented by AC current
because the two function through alternating sine waves (the squiggly lines). For every
positive (peak), there is a negative (trough), by counting the peaks we can determine the
number of complete cycles per second or its frequency; in this case, it would be 15 Hz.
This number is directly proportionate to the number of times the cone would have to
travel (outward and inward) in the same period. As you may have guessed when the
frequency increases, the distance between peaks decreases. This phenomenon is
witnessed whenever watching a subwoofer working in a sealed cabinet. The lower the
frequency the greater the distance the cone must travel, likewise at higher frequencies
the woofer doesn’t appear to move at all. What does all of this have to do with making
the big numbers? It’s to show that higher frequencies (60Hz and up) are more efficient
for subwoofers to produce (more output), and it’s less demanding on amplifiers;
increasing their efficiency (more output), and brings us to the next lesson:
Calculating wavelength:
Because we know that the speed of sound is a constant {1131(fps) @ sea level}, we
can calculate the distanced required for a known frequency to complete a cycle. The
math is painless; let’s look at 60Hz (or 60 cycles-per-second)
1131/60 = 18.85 feet per second
Since both values are measured in seconds, no further conversion is necessary. Of
course, this distance is larger that any one measurement of the vehicles interior (in most
cases). It’s for this reason that competitors will base their target frequency on the ¼-
wave measurement. To determine this measurement divide the earlier quotient by 4:
18.85/4 = 4.71 feet per second
Now its time for the fun stuff, the coolest thing about this industry is the ability to
create a sonic discharge potent enough to shake foundations, tear metal, and set off car
alarms for a mile. So how do you make one 15” subwoofer produce 150dB+?
The evolution of SPL has taken place at a geometric rate. The reality is this; more
progress has taken place in subwoofer and amplifier design in the last 10 years than in
the 60 years before it. Those who have been following the industry for more than the
last decade can remember the “more is more” period of competition. In this golden age,
it was common to see large numbers of drivers with high current amplifiers. It was
during this time the “wall” became popular 5, 10, or 64 drivers in sealed enclosures
(individual chambers of course), and running off the lowest number of amps possible.
This was due to fact that classes were divided by rated power at 4 ohms. This was the
heyday of the high current amplifier. The most sought after bass amps were still class
A/B. Who doesn’t want a 25w x 2 amplifier that was 400wrms at ½ ohm mono or
200wrms at ¼ ohm stereo? Of course, you could cook on them at full volume, not to
mention they could drain a tractor battery to 10 volts in seconds. Nevertheless, the
numbers were impressive. Well if you’re satisfied with a 140’s with six 15’s behind your
head, help yourself.
Soon after this indulgence of more subs = more sound thinking, manufacturers
began performing a mechanical overhaul (necessity is the mother of invention…). Up
until now, subwoofers still looked and responded like their PA cousins, smaller motor
structures, voice coils, spiders, and low excursion were the Achilles tendon of
performance. Though they had a high sensitivity rating, they lacked power handling, the
suspensions were outdated, and true high excursion didn’t exist. Subwoofer design
went back to the drawing board to be revamped from top to bottom. Several companies
began offering subwoofers that could handle much higher wattage (1000wrms+),
suspension compliance was modified for long throw woofers that could function in
oversized ported enclosures, long excursion woofers with linear travel began to appear,
and cone materials changed to allow for stronger cone assemblies. These revolutions
lead to the death of pole piece venting as we knew it, the ultimate heat dissipating
innovation, Cross Vent™ cooling was its replacement. Next, we grew the diameter of
the voice coil improving heat dissipation even more, and more heat dissipation meant
more reliable power handling.
Then the final tumblers fell into place…the class D amplifier was designed,
engineered, and released. More power was finally available, more power than ever
available before. Enclosure design was reworked to produce huge gains in sensitivity
(10dB+). Finally science took center stage; less drivers equals less phasing issues; less
phasing issues = less cancellation; less cancellation = more output. Larger port size
increases the total radiating surface. Hitting the microphone with the peak of the wave
registers more output. This meant determining the wavelength and building an
enclosure to suit. Port placement and subwoofer placement began to be serious
concerns where in the past the idea was that it didn’t matter, because systems were
“pressurizing the entire cab”; not taking into consideration the idea of cancellation and its
effects on total measurable output. With this tutorial we will try to unravel some of the
mystery involved in creating monster bass. Moreover, Oz audio is proud to be able to
deliver innovative technology to the competitor and dealer alike through state-of-the-art
subwoofers and amplifiers. So if you are ready to wield this knowledge, continue on.
Increasing Displacement:
As you already know, you cannot physically make your subwoofer larger, but you
can increase the radiating area by increasing port area.
The first illustration represents a subwoofer in a sealed (acoustical suspension)
cabinet and you can see the appreciable output. This type of performance would be
considered normal output. The drawback of this subwoofer system is the output is
limited by both cone displacement (surface area of the cone x excursion) and power
handling. Really, the only way to get more output would be to add another driver (more
$ and may lead to phasing issues) or more power until you reach the maximum power
rating, after that you risk damaging the woofer through thermal saturation or over-driving.
This type of power can result in torn spiders, broken cones, or damaged voice coils.
Even though this design is practical for everyday listening, it is not the first choice for
unlimited SPL.
Meanwhile, in the second illustration, we are displaying your prototypical oversized
ported (bass-reflex) cabinet. Here you can see at the desired frequency (Fb), the output
from the subwoofer and the port are in phase, improving the subwoofer systems output
by roughly double (+3dB gain). Something that is not seen in this illustration is that near
the desired frequency (Fb) there is minimal cone movement due the large amount of
support being supplied to the backside of the subwoofer. Because of this phenomenon,
power handling is increased. This also minimizes the chances of overdriving the woofer,
unless the driver is grossly overpowered, or is forced to play below the vent tuning (see
Bass Reflex; Pro’s and Con’s).
As discussed in earlier tutorials, bandwidth is traded for sensitivity; this is true with
SPL enclosures as well. As the port area increases (and increasing total volume as a
result), the bandwidth will shrink. Although this is less favorable when building a
subwoofer system for “everyday listening” it is irrelevant in SPL, this is one of the rare
situations that a one-note bass cabinet is necessary. For maximum output, optimum
sensitivity and radiating displacement are priority one. So what does this all mean?
Here in the recommended “SQ” enclosure the response is very flat, very wide, and
with moderate gain (+1.22dB).
Here is the response curve of a Power 15 in a SPL enclosure, notice the radical
peak; this represents a gain of 12.4dB or roughly 16 times the output! Notice the narrow
bandwidth; how the output is dramatically reduced on the left or right of the Fb. Without
increasing the number of Power 15’s we increased our radiating area from 129in2 (cone
area of one Power 15) to 329in2 (port area + cone area). Of course, there are limitations
to these designs, but the limits are determined by the subwoofers ability to interact with
the enclosure. The subwoofers suspension has to be tough enough to control the
driver’s motion in a massive vented and to support a vent this size. As a rule of thumb,
most high performance woofers will support up to one-half of their cone displacement in
vent displacement. SPL subwoofers (Power 15.1 and 12.1) can sustain in excess of 2x
their cone displacement.
What’s next? Making sure all of the output (or as much as we can) reaches the
microphone.
Traveling at the Speed of Sound:
Everyone has heard the terms, cycles-per-second, frequency/freq, Hz/hertz (not the
rental company), sine wave, and wavelength. However, few understand what they
signify.
If we break the audio path down into its most basic parts, we could remove one sound
wave for examination, as in the illustration. Audio signal is represented by AC current
because the two function through alternating sine waves (the squiggly lines). For every
positive (peak), there is a negative (trough), by counting the peaks we can determine the
number of complete cycles per second or its frequency; in this case, it would be 15 Hz.
This number is directly proportionate to the number of times the cone would have to
travel (outward and inward) in the same period. As you may have guessed when the
frequency increases, the distance between peaks decreases. This phenomenon is
witnessed whenever watching a subwoofer working in a sealed cabinet. The lower the
frequency the greater the distance the cone must travel, likewise at higher frequencies
the woofer doesn’t appear to move at all. What does all of this have to do with making
the big numbers? It’s to show that higher frequencies (60Hz and up) are more efficient
for subwoofers to produce (more output), and it’s less demanding on amplifiers;
increasing their efficiency (more output), and brings us to the next lesson:
Calculating wavelength:
Because we know that the speed of sound is a constant {1131(fps) @ sea level}, we
can calculate the distanced required for a known frequency to complete a cycle. The
math is painless; let’s look at 60Hz (or 60 cycles-per-second)
1131/60 = 18.85 feet per second
Since both values are measured in seconds, no further conversion is necessary. Of
course, this distance is larger that any one measurement of the vehicles interior (in most
cases). It’s for this reason that competitors will base their target frequency on the ¼-
wave measurement. To determine this measurement divide the earlier quotient by 4:
18.85/4 = 4.71 feet per second
lord baccus
10+ year member
Member
This new number is much easier to work around and would be very practical for a
full-size pickup (extended cab of course) or SUV with rear seats removed. The beauty
of this equation is that it works well in either direction. Say you have measured the area
to be sacrifice for the enclosure, then measure the distance from the woofer location1 to
the microphone position, this distance will help you find your target frequency. For
example if the distance is 5 feet, multiply the distance by 4 (to find full wave distance)
and then divide this number into the speed of sound (1131fps)
5 x 4 = 20 ft
1131/20 = 56.55 Hz
Once you have determined your wavelength distance and target frequency tune your
enclosure 5 – 10 Hz lower to take advantage of peak output. This margin may need
adjustment depending on the woofers ability to interact with the enclosure. It’s important
to keep in mind that this equation is for front firing enclosures as in the illustration.
Another event to observe in this illustration is how the output from the backside of the
woofer (red) will travel through the vent (yellow), begin reinforcing the output from the
front side of the woofer (orange) and finally the acoustical output will be at full potential
at the microphone (dark red). When your system is setup is correct, you will experience
similar results.
The only obstacles left are deadening the interior, sealing the vehicle’s leaks, and
proving enough current and voltage for the amplifiers2.
full-size pickup (extended cab of course) or SUV with rear seats removed. The beauty
of this equation is that it works well in either direction. Say you have measured the area
to be sacrifice for the enclosure, then measure the distance from the woofer location1 to
the microphone position, this distance will help you find your target frequency. For
example if the distance is 5 feet, multiply the distance by 4 (to find full wave distance)
and then divide this number into the speed of sound (1131fps)
5 x 4 = 20 ft
1131/20 = 56.55 Hz
Once you have determined your wavelength distance and target frequency tune your
enclosure 5 – 10 Hz lower to take advantage of peak output. This margin may need
adjustment depending on the woofers ability to interact with the enclosure. It’s important
to keep in mind that this equation is for front firing enclosures as in the illustration.
Another event to observe in this illustration is how the output from the backside of the
woofer (red) will travel through the vent (yellow), begin reinforcing the output from the
front side of the woofer (orange) and finally the acoustical output will be at full potential
at the microphone (dark red). When your system is setup is correct, you will experience
similar results.
The only obstacles left are deadening the interior, sealing the vehicle’s leaks, and
proving enough current and voltage for the amplifiers2.
obrien202
10+ year member
I Race Dirtscooters
29hz
lord baccus
10+ year member
Member
Measure from where the cone of the sub is / to where you place the mic /
say its 6ft
6x4=24
devide 1131/24 = 47.13Hz
based on the 1/4 wave you can determin what to port your boxx to...
or if you want lower tunning go with the 1/8th wave
6x8 = 48
1131/48 = 23.57Hz
say its 6ft
6x4=24
devide 1131/24 = 47.13Hz
based on the 1/4 wave you can determin what to port your boxx to...
or if you want lower tunning go with the 1/8th wave
6x8 = 48
1131/48 = 23.57Hz
obrien202
10+ year member
I Race Dirtscooters
28hz //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif
galacticmonkey
5,000+ posts
Wants a button like that.
Tune to 1hz for the lows.
36 and call it a day
0hz actually.
Divide
Determine
Box
Tuning
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