type x vent
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=97354
Printed Date: May 11, 2024 at 5:36 PM
Topic: type x vent
Posted By: s_abercromby
Subject: type x vent
Date Posted: September 23, 2007 at 12:01 AM
hey i'm building a custom center console with a sub box attatched to it for my truck, i have an alpine 10" type x and want a vented box, on their website (www.alpine.com) and manual they show what internal volume and vent length and volume should be, the only thing is that my box doesn't have a side that i can put an 11x1" vent, i want to put a 15x1" vent, i tried using the port length calculator on this website, but i don't know if it works the same for a rectangular vent because it is for a circular port. i've also read that a bigger area port requires more length for the same effect. if this is true than why wouldn't people just put a 1" port so that the box can be a lot smaller and so can the length of the port.
Replies:
Posted By: stevdart
Date Posted: September 23, 2007 at 12:29 AM
The reason is "port noise" by using vent openings that are too small or too oddly mishaped. Vent opening size ratio should be 8:1 or less. For example, 16" x 2" or 12" x 1.5". That's maximum. More square is better. If the website gives you dimensions for a 11 X 1 vent and you want to change the long side to 15", you have to... Obviously they are not following the 8:1 ratio rule when they give you build plans using a 11 X 1 slot opening. But, nevertheless, from that you know that they intend that the slot opening area should be 11 square inches in order to correspond to the vent length that they specified. (As an aside, if you have room for a 15 X 1 slot, you also have room for an 11 X 1 slot)........... So we look at rule #1 and see that an 8:1 ratio or less should be attained. 11 X 1 doesn't make it and neither does 15 X 1. To make your port the length that is specified, find a length to width ratio that is acceptable and that also equals 11 square inches. As long as the opening size in square inches is the same as the specification, the length of that port remains the same as specified. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: s_abercromby
Date Posted: September 23, 2007 at 12:38 AM
i don't understand why they would tell you to build a box that isn't right. i mean, they should know their subwoofer the best right.
Posted By: aznboi3644
Date Posted: September 23, 2007 at 12:01 PM
at port tuning frequency almost all of the sound comes from the port
Posted By: s_abercromby
Date Posted: September 23, 2007 at 1:07 PM
so should i have the port facing somewhere open, cuz i was gunna port it under the seat but have the sub facing up
Posted By: s_abercromby
Date Posted: September 23, 2007 at 1:31 PM
this is what i don't understand, alpine probably puts tons of money into the production and testing of their products. I mean i know people say they are sort of like nike where they have lots of money because the name is so big that everyone buys it. but you would think that with that money they would be paying some pretty smart engineers to build and test their woofers, with some very complex equations. And judging by their budget on their showcars, they probably tested millions of different shaped and ported boxes to find the one that would make their product sound it's absolute best so me, as the consumer would buy it. please somebody correct me if i'm wrong, i just wanna get started on building this thing, it bothers me to have it sitting here hahahha, but i do want to do this right. thanx
Posted By: aznboi3644
Date Posted: September 23, 2007 at 2:52 PM
show cars and competition cars are a lot different
Posted By: s_abercromby
Date Posted: September 23, 2007 at 9:15 PM
yes i realize that, what i meant was the company has a lot of money to build those cars, i think it is two guys who build it and have a huge budget, so think of the budget for testing boxes to make their subwoofer sound the best for their consumers. at least if it was me who owned a huge money making business like that, i would probably tell people how to construct a box that would make their sub sound the best.
Posted By: sarcomax
Date Posted: September 25, 2007 at 12:31 PM
I am sorry in advance for everyone taking this the wrong way...(two weeks vacation in hawaii, then I had to come back to work) You obviously don't visit the real world all that often. People that run huge money making businesses do not do it for the customer. They do it for the huge money. Don't get me wrong, I agree with your views on the subject, but I can't think of a large corporation that the owner has done anything to show me that they care about the money less than the customer. I get stuff in the mail all the time from various companies that say "because you are a valued customer" and then go on to tell me about something that I will be spending money on. Any time money is given out it is usually for tax write offs and lawsuit evasion. Most product development is not for making stuff last longer or sound better, it is for a subtle change, sometimes cosmetic that makes this years model a "must have" so you go out and spend more money to replace a perfectly good unit. The manual was not written by an engineer, it was problably typed by a malaysian sweat shop worker that does not have a car much less a stereo to put in a car, and probably does not speak english. The only 8:1 ratio that they know is they work 8 hours and get 1 dollar. It very well could be a misprint. What do I know. I am a sucker for new gum brands and flavors.
Posted By: audiocableguy
Date Posted: September 25, 2007 at 3:35 PM
Sound is one of those very subjective things. Look at how many speaker manufactures there are. Each one has designers and engineers that do nothing but make products. ABC Corp. intro's there top of the line coax. All involved, agreed this was the best they could do. As a consumer my tastes says they sound like ass. So I audition another speaker and love them. Was it ABC's bad or just my tastes were different?
For instance Alpine built a speaker that met price point X, Box size X, and Size X. The numbers say use a ported box, tune to this frequency and enjoy. Now my vehicle is a pickup with four doors, their test box fit in a hatchback. I listen to Speed Metal and Alpine used Classical... where I'm going with this is nothing is set in stone when dealing with something that is very subjective in a varied environment!
Posted By: sarcomax
Date Posted: September 25, 2007 at 4:33 PM
If you didn't like what ABC Corp put out then you are a worthless loser. We spent billions on advertising, billions on executive bonuses, and gave our designers and engineers a 40 dollar budget and 5 hours to come up with that design. Your ears suck! Get a new pair! Love, Owner of ABC Corp. 
Posted By: sarcomax
Date Posted: September 25, 2007 at 4:35 PM
Oh, yeah... +1 on what audiocableguy said too. I was too busy bashing coporate america to use my logic parts...
Posted By: audiocableguy
Date Posted: September 25, 2007 at 11:58 PM
hey sarcomax, two more weeks in Hawaii might be good for you 
Posted By: haemphyst
Date Posted: September 26, 2007 at 1:11 AM
audiocableguy wrote:
hey sarcomax, two more weeks in Hawaii might be good for you
But only if you're taking me, too... I haven't even HAD a vacation, let alone a Hawaiian vacation, in almost 2 years! ------------- It all reminds me of something that Moličre once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: jfinks
Date Posted: September 27, 2007 at 12:12 AM
The 8:1 ratio is a guild line but only aplies to a certain frequency. To answer some questions: You should have at least 3" of clear space in front of the port...this is a guild line...anything that impeads the movement of the air in the port will change the frequency that it resonates at or it 's tuning.. Yes as the frequency aproaches the tune of the port it is producing more of the sound...another reason you want the port out in the open. There is an effect called coupling that you can take advantage of with the port facing the ground. If you make the bottom of the box a uniform (well mostly uniform) distance from the floor...oh say 2 '', then the "Slot" that it forms can actually increase the output. This is also know as slot loading. This same effect can be used when placing two woofers next to each other because both cones are moving in unison they will also move the space of air between them effectively increasing the size of the moving area in front of the two speakers.... the port demensions are based on the ratio of the area of the openingof the port to the port length; so bigger opening means longer port. But don't fall into the trap that if you increase the port opening size you just increase the length the same ratio as the smaller port. There is another ratio involved that takes into account of the port volume vs. the box volume. this ratio is NOT linier! The shape has very little or nothing to do with how it functions unless, as stated earlier, it gets too small and begins to whistle. So as long as the the area is the same the port lenght is the same. Also as long as you don't change the area of the opening of the port tube you can bend it to fit your space. Ask Haemphyst about folded transmition lines and why the are called folded...Think of of a trumpet
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