Downfiring enclosure: To the wire
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=50712
Printed Date: May 15, 2024 at 10:33 AM
Topic: Downfiring enclosure: To the wire
Posted By: uthinkuknoaudio
Subject: Downfiring enclosure: To the wire
Date Posted: February 23, 2005 at 8:26 PM
Well, i finally got those blasted T/S measurements for my two Nakamichi SP-W120 subs. I checked out WinISD and i got some measurements. (LengthxDepthxHeight) 25.90" x 10.65" x 16.75". That 16.75" is the maximum i can go for the enclosure to fit under my roll over cover, so i will have to make the sides bigger and decrease the volume a bit. Any clues? WinISD suggested i also port them. A 4.02" circular port to be exact. I hate circular ports. I want to know how i can do this with a slot port instead and still have those suckers tuned down to 35 hertz. The box is 1.97 cubic feet. Here are those parameters: (Its a 12'' Woofer) Fs = 28.15 Hz Vas = 85.30 L Qms = 4.08 Qes = .36 Qts = .33 Xmax = 6.00 mm Re = 3.39 ohms Specs Sensitivity = 90 db Power Handling = 200 watts RMS / 400 watts peak Freq Response = 25 - 250 Hz 4ohm Impedance Mounting Depth = 5" ------------- "I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Replies:
Posted By: uthinkuknoaudio
Date Posted: February 23, 2005 at 8:54 PM
bump
-------------
"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Posted By: stevdart
Date Posted: February 23, 2005 at 8:59 PM
Check out the kingpin111 thread that says You guys have come highly recommended.......the way to change from round port to slot is in there.
Posted By: uthinkuknoaudio
Date Posted: February 23, 2005 at 9:17 PM
I checked that out but i'm still confused. My other questions haven't been answered, but what formula do i use to get lxwxh of the port? I like the whole square port thing that is far better for what i want. How deep should the port go if i know i can only go 10.65" total in depth and the circular port was 4.02" ???
-------------
"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Posted By: forbidden
Date Posted: February 23, 2005 at 9:38 PM
Find the port length for the circular port, this length stays the same for a slot port. Next you need to find the area of a circle and rectangle. circle = pie * r^2 or in this case a 4" port is 3.1415 * 2^2 = 12.57 square inches. rectangle = l * w = 12.57 eg. or a slot port of 6.26" * 2" * whatever the depth of the circle port was. ------------- Top Secret, I can tell you but then my wife will kill me.
Posted By: uthinkuknoaudio
Date Posted: February 23, 2005 at 9:41 PM
It says the vent length is 10.95 inches, impossible when the depth is 10.65"... unless i'm missing something. ------------- "I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Posted By: kfr01
Date Posted: February 23, 2005 at 10:04 PM
Is it really that big of a mystery? Bend it around the corner.
-------------
New Project: 2003 Pathfinder
Posted By: forbidden
Date Posted: February 23, 2005 at 10:24 PM
And use the flexible 1/2" mdf to do this with.
-------------
Top Secret, I can tell you but then my wife will kill me.
Posted By: stevdart
Date Posted: February 23, 2005 at 10:31 PM
Uthink, you should really just spend a little more time understanding how that program works. If you notice, 4.02 comes up as default with every new project that is vented. You can change it. Double click on it, type in the diameter that will give you a shorter length that will fit in your box. Convert to slot ala Rob's post.
Posted By: uthinkuknoaudio
Date Posted: February 24, 2005 at 4:21 PM
What does it mean when the vent mach number is in the red? Do i have to change it until it hits the green? To 0.0 perhaps?
-------------
"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Posted By: haemphyst
Date Posted: February 24, 2005 at 5:00 PM
Yes, you continue changing the number till it gets into the green area. The red indicates (probably - I don't use the program, so this is a guess) that the speed of the air in the port is going supersonic - faster than sound, and this will cause port noise. If this is indeed the case, you need to make the port bigger, so the air moves slower through it.
-------------
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: uthinkuknoaudio
Date Posted: February 24, 2005 at 5:27 PM
So you can really bend a port? Well, i tried doing a square port on there, and it took me almost a 5"x5" to get it into the green. That is huge. I tried 2 separate 2.5" square ports and it was in the green, although each port lenth exceeded 13". hm....
-------------
"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Posted By: kfr01
Date Posted: February 24, 2005 at 5:45 PM
Yes, you can bend a port.
-------------
New Project: 2003 Pathfinder
Posted By: uthinkuknoaudio
Date Posted: February 24, 2005 at 5:46 PM
are you supposed to bend the port even though it goes all the way to the back of the box and then you have to bend it? What should i build this port out of?
-------------
"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Posted By: uthinkuknoaudio
Date Posted: February 24, 2005 at 5:56 PM
Well i figured out how wide the port is. I'm using two of the ports, each 2.1"x2.1" (Square) in diameter. How deep should i build them in? I always build sealed boxes, so i've ne ver screwed around with building a ported. Usually, i have them built. This is my first stab at it.
-------------
"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
Posted By: stevdart
Date Posted: February 24, 2005 at 7:08 PM
I don't know what version you have that shows green and red, but the air velocity needs to be less than 1/10 the speed of sound. So as long as the graph "Air Velocity" shows less than 100 ft/second at the maximum wattage you will get to you'll be good to go. Ft./sec numbers are along the left of the graph vertical; freqency is along the bottom horizontal. https://www.carstereo.com/help2/Articles.cfm?id=4 https://www.carstereo.com/help2/Articles.cfm?id=31
Posted By: uthinkuknoaudio
Date Posted: February 24, 2005 at 9:26 PM
How deep should i build it? What should i build them out of? (Ports that is)
-------------
"I don't play games. I play Nakamichi and that for real yo" - Probably some japanese kid said this in the early 80's trying to sell stereo out of his trunk lol.
|