Ok.. this outta be fun!
I am contemplating cutting a hole in the cab (under jump seats) to install 2 amps and one ported sub enclosure. Then having the metal "cage" and carpet cleaned up professionally for a nice amp rack/sub display.
Catch my drift?
Anyhow, To this end I am trying to determine the exact size of the box (H x W x D) I will build into the floor as well as the port length & size. I was looking at the specs/instructions directly from the manual my sub came with, and thats where I started to encounter some problems. The size of the box and the port length seem to conflict with each other. So I began to do more reasearch. I found a few port and enclosure calculators, and snagged a few fomulas & calculated stuff on my own; and things just don't quite add up. I can tweak the formulas to get it close to what the manual says, But not without some minor discrepancies.
I know it's probably not THAT big of a deal to go into all this detail to get it "perfect", but now that I'm in this deep, I can't let it go. I gotta find the "right" answer even if I can't build the box just "perfect". This has become more of a PUZZLE to me than just needing an answer, and I got sucked in. Know what I mean?
I have a DLS MW10 I am putting in a ported/vented enclosure.
First, here are my sub specs directly from the manual:
This is the recommended enclosure size directly from the same manual.
Some of you audio nuts probably already know this, but for those reading that don't here are some Additional details provided by the manual:
I was having trouble coming up with the measuements for a box small enough, yet still have a 3 inch port 10.2 inches long. So, I Then found a few formulas to calculate the optimal size & length of the port and I come up with some completely different values.
Minimum vent (port) diameter:
dv - is the required diameter of the port in inches.
Fb - is the tuning frequency of your enclosure in Hertz.
Vd - is the volume displaced by the driver (in cubic meters) traveling through it's full excursion (peak-to-peak). To figure out Vd for a speaker, find the Sd value for your driver in the table below, and multiply that number times the Xmax (in meters) of your speaker.
Vent Length:
Fb - is the tuning frequency of your enclosure in Hertz.
Lv - is the length of your port in inches.
R - is the inside radius of your vent tube.
Vb - is the internal volume of your enclosure in cubic inches. To convert cubic feet to cubic inches, multiply by 1728.
Oh.. and just for giggles... for someone that might want to use a square or retangular port instead, here's the formula to figure that out! Just put this formula in place of "R" and solve, where "a" is the area (L x W) of your port.
NOW THE FUN BEGINS!!!
According to the manual, the size of the sub and port are already figured into the volume requirement; SO, I need to build a box to 0.85 cu feet. A port 3 inches x 10.2 inches long. Cannot come within 3 inches of the rear wall. (If it was a 4 inch port, it would be 4 inches from wall). At a tuning frequency (Fb) of 40 Hz. Well that doesn't leave me with many options, does it? The closest I can come with a single port is a wedge shaped box of 10.5"H x 13.75"W x 6.5"D1 x 14"D2. (D1 is top, D2 is bottom). That's a pretty tight fit for everything, but that gives me a box of 0.856 cu ft. Close enough!
But I'm thinking the best route would probably be a curved shape port of the same length. That would cut down the depth of the port allowing me more flexibility on the shape & size of the box. However, I punch these numbers into one of the calculators online and get an error. My numbers just don't match. I can't get that frequency with the size of the port, box, etc. So i tried using the formulas...
Using the formula for Minimum Vent (port) diameter, it says I need a port 4.19 inches wide (ok, 4 inches is cool). Immediate red flag! Is it supposed to be 3 or 4 inches?!? :shrug:
Then using the vent length formula using the value I just got, I get a required length of 24.26 inches. Houston, we have a problem!! :silly:
Sorry, 24.26 inches just ain't going to work. However, if I just arbitrarily plug in 3 inches on the second formula is spilts out a length of 11.81 inches. That's at least close to the manual...
So what is the real answer?
If I buy a ported box directly from the manufacturer, it is actually 2 liters larger than the recommended size for my sub and 2.8 liters smaller than theer other 10" reference sub. That an error of 15% or more. I'm assuming that's ok, but not optimal, right?
So how close do I have to be to the manuals spec to be "good enough"?
Or is it the manual's spec that is just "good enough" and I can do better by calculating the correct formulas?
Given the info I have provided, what do you think is the optimal size for my box & port?
I know 0.85 cu ft sounds small for a ported enclosure, but that is in fact what the manual is saying. How much performance would I use going a little bigger. I currently have a basic ported for a 10 inch sub. It's not custom tailored to mine, but it sound ok. It just won't fit where I want to install my custom box. (I'll get the dimentions later). Will I notice a difference if I try to make it "perfect?
In the end, I'll probably just get as close as I can, and call it good.
what do you guys think?
I am contemplating cutting a hole in the cab (under jump seats) to install 2 amps and one ported sub enclosure. Then having the metal "cage" and carpet cleaned up professionally for a nice amp rack/sub display.
Catch my drift?
Anyhow, To this end I am trying to determine the exact size of the box (H x W x D) I will build into the floor as well as the port length & size. I was looking at the specs/instructions directly from the manual my sub came with, and thats where I started to encounter some problems. The size of the box and the port length seem to conflict with each other. So I began to do more reasearch. I found a few port and enclosure calculators, and snagged a few fomulas & calculated stuff on my own; and things just don't quite add up. I can tweak the formulas to get it close to what the manual says, But not without some minor discrepancies.
I know it's probably not THAT big of a deal to go into all this detail to get it "perfect", but now that I'm in this deep, I can't let it go. I gotta find the "right" answer even if I can't build the box just "perfect". This has become more of a PUZZLE to me than just needing an answer, and I got sucked in. Know what I mean?
I have a DLS MW10 I am putting in a ported/vented enclosure.
First, here are my sub specs directly from the manual:
Code:
TECHNICAL SPECIFICATIONS FOR DLS REFERENCE SUBWOOFERS
Type/Model MW10
Size "25 cm (10"")"
Impedance 4 ohm
Nom. power (RMS) 400 W (max 600)
Freq. range 25 Hz- 2 kHz
Sensitivity 89 dB
Voice coil diameter 75 mm (3”)
Voice coil height 24 mm (0.94”)
Re 3.23 ohm
Voice coil inductance 1.26 mH
BL product 14.2
X-max +-9 mm (0.35”)
Suspension compliance CMS 202
SD- Effective piston area 314.6 cm2
Resonant freq. (Fs) 35.1 Hz
Vas (liters) 28
Vas (ft3) 1.51
Qms 2.32
Qes 0.36
Qts 0.31
Cone material Magnesium
Magnet weight 100 oz (2.83 kg)
Magnet diameter "6.14"" (156 mm)"
Installation depth "5.11"" (130 mm)"
Mounting hole "9.21"" (234 mm) "
Outer diameter "10.31"" (262 mm)"
Weight 14.77 lb (6.7 kg)
Code:
[B]Subwoofer Volume (liters/ft3) Port Damping F3 Fb[/B]
MW10 vol: 24/0.85 3”x26cm/10.2” Line inside 46.3 Hz 40.0 Hz
[B][FONT=HelveticaBold][SIZE=2][COLOR=#231f20]F3 [/COLOR][/SIZE][/FONT][/B][FONT=Helvetica][SIZE=2][COLOR=#231f20]= approximative lower frequency forvented boxes in Hz. [/COLOR][/SIZE][/FONT]
[FONT=Helvetica][SIZE=2][COLOR=#231f20]Often called F-3 dB point = the point where the power is 50% lower.[/COLOR][/SIZE][/FONT]
[LEFT][B][FONT=HelveticaBold][SIZE=2][COLOR=#231f20]Fb [/COLOR][/SIZE][/FONT][/B][FONT=Helvetica][SIZE=2][COLOR=#231f20]= Box resonant frequency[/COLOR][/SIZE][/FONT][/LEFT]
Code:
- All volumes are inside measures.
[LEFT][B]- Volumes occupied by speaker and ports have already been added to the [/B]
[B]given enclosure volumes.[/B]
- Use conical bass ports for best result. (DLS BP-75 or BP-110). If the ports
are too long for the box you can use a bend. Either cut the tube and glue it
together in angle, or use factory made tube bends. It´s easier to use the
factory made ones. The total length must be the same as for a straight tube.
Make the measure in the center of the tube.[B] The port opening inside the [/B]
[B]enclosure must not be closer to an interior wall than 3” (75 mm), otherwise it [/B]
[B]will have negative effects on the airflow.[/B]
- The enclosure must be very steady and completely airtight. Use 22 mm
particle board or 19 mm MDF-board. The particle board has a self resonant
frequency of 14 Hz while the MDF has a resonant frequency of approx. 400
Hz. [B]It´s important to do some type of bracing inside the enclosure to avoid [/B]
[B]vibrations. Volume taken up by bracing should be added to the enclosure [/B]
[B]volumes.[/B][/LEFT]
[LEFT]ENCLOSURE DAMPING
[B]Most enclosures should be damped inside with syntetic (acoustic) wool or[/B]
[B]damping mat (line). Attach the damping material on the wall opposite from [/B]
[B]the speaker and port.[/B] A sealed enclosure should be filled up to 70-100%
with acoustic wool. In a vented enclosure the speaker and port should be on
the same side, otherwise a fade-out of some requencies can occour.[/LEFT]
Minimum vent (port) diameter:
dv - is the required diameter of the port in inches.
Fb - is the tuning frequency of your enclosure in Hertz.
Vd - is the volume displaced by the driver (in cubic meters) traveling through it's full excursion (peak-to-peak). To figure out Vd for a speaker, find the Sd value for your driver in the table below, and multiply that number times the Xmax (in meters) of your speaker.
Vent Length:
Fb - is the tuning frequency of your enclosure in Hertz.
Lv - is the length of your port in inches.
R - is the inside radius of your vent tube.
Vb - is the internal volume of your enclosure in cubic inches. To convert cubic feet to cubic inches, multiply by 1728.
Oh.. and just for giggles... for someone that might want to use a square or retangular port instead, here's the formula to figure that out! Just put this formula in place of "R" and solve, where "a" is the area (L x W) of your port.
NOW THE FUN BEGINS!!!
According to the manual, the size of the sub and port are already figured into the volume requirement; SO, I need to build a box to 0.85 cu feet. A port 3 inches x 10.2 inches long. Cannot come within 3 inches of the rear wall. (If it was a 4 inch port, it would be 4 inches from wall). At a tuning frequency (Fb) of 40 Hz. Well that doesn't leave me with many options, does it? The closest I can come with a single port is a wedge shaped box of 10.5"H x 13.75"W x 6.5"D1 x 14"D2. (D1 is top, D2 is bottom). That's a pretty tight fit for everything, but that gives me a box of 0.856 cu ft. Close enough!
But I'm thinking the best route would probably be a curved shape port of the same length. That would cut down the depth of the port allowing me more flexibility on the shape & size of the box. However, I punch these numbers into one of the calculators online and get an error. My numbers just don't match. I can't get that frequency with the size of the port, box, etc. So i tried using the formulas...
Using the formula for Minimum Vent (port) diameter, it says I need a port 4.19 inches wide (ok, 4 inches is cool). Immediate red flag! Is it supposed to be 3 or 4 inches?!? :shrug:
Then using the vent length formula using the value I just got, I get a required length of 24.26 inches. Houston, we have a problem!! :silly:
Sorry, 24.26 inches just ain't going to work. However, if I just arbitrarily plug in 3 inches on the second formula is spilts out a length of 11.81 inches. That's at least close to the manual...
So what is the real answer?
If I buy a ported box directly from the manufacturer, it is actually 2 liters larger than the recommended size for my sub and 2.8 liters smaller than theer other 10" reference sub. That an error of 15% or more. I'm assuming that's ok, but not optimal, right?
So how close do I have to be to the manuals spec to be "good enough"?
Or is it the manual's spec that is just "good enough" and I can do better by calculating the correct formulas?
Given the info I have provided, what do you think is the optimal size for my box & port?
I know 0.85 cu ft sounds small for a ported enclosure, but that is in fact what the manual is saying. How much performance would I use going a little bigger. I currently have a basic ported for a 10 inch sub. It's not custom tailored to mine, but it sound ok. It just won't fit where I want to install my custom box. (I'll get the dimentions later). Will I notice a difference if I try to make it "perfect?
In the end, I'll probably just get as close as I can, and call it good.
what do you guys think?