port size
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=106570
Printed Date: May 02, 2024 at 8:22 PM
Topic: port size
Posted By: bigbev
Subject: port size
Date Posted: August 04, 2008 at 3:58 PM
I am new to box building and nobody makes a prefab box for a 1995 chevy full size truck that will hold two 15's so i decided to build my own, the problem i am having is that my subs sound distorted at higher volumes but if i roll the windows up the distortion almost completely goes away. My subs are 15 inch kicker cvr's, the dementions of my box are 58" wide, 21" tall, and 20 1/4" deap, with 3/4" mdf, which if im right comes out to about 5.6 cubic feet per chamber not including the sub, i do have a divider so each sub has its own airspace. The thing i need to now is how big should my port be, im having trouble figuring this out because both subs share the same port. the picture below is of the port so you can get a better idea of what im talking about.
port
pic of the box
I can modify the port or the box if i need to. feel free to ask any questions, i will answer then as best as i can,
thanks
Replies:
Posted By: DYohn
Date Posted: August 04, 2008 at 5:17 PM
5.8 cuft is a little large for a CVR15, but certainly doable. What is your desired tuning frequency? What do you mean when you say they "sound distorted"? And you say that both subs share the same port, but that they are in separate chambers. Which is it? ------------- Support the12volt.com
Posted By: bigbev
Date Posted: August 04, 2008 at 6:23 PM
well the distortion is really hard to describe, at first i thought it was body flex making the noise so put braces in all of the places that had a lot of flex but the sound did not change. sorry if i described the port wrong, the picture kinda speaks for itself I have a divider in the box but just one big port . as far as the tuning frequency, what would you recomend? Im new to building boxes so im trying to learn. the internal volume of the box is 11.95475 without the divider according to the calculator on this site.
Posted By: DYohn
Date Posted: August 04, 2008 at 6:39 PM
Well, if you have one port that connects both enclosures, that can work. What are the dimensions of the port as you have it constructed? ------------- Support the12volt.com
Posted By: bigbev
Date Posted: August 04, 2008 at 7:06 PM
the port is 23" wide, 5" tall, and 15" deep.
Posted By: DYohn
Date Posted: August 04, 2008 at 7:51 PM
Assuming those are the inside measurements of the opening, you are tuned to about 30Hz, which is not absolutely optimal but should work fine with CVRs. Leave it like it is, and make sure the enclosure is well braced and all the inside seams are sealed, and then make certain your gain is set properly and the LP filter is set to between 80-100Hz, and you should get about the best performance you can expect from that setup. Those Autoteks have a subsonic filter which should be activated and set to about 25Hz. Also, they ARE mounted separately and do not actually penetrate the enclosure, right? ------------- Support the12volt.com
Posted By: bigbev
Date Posted: August 04, 2008 at 8:44 PM
yes those are the measurements of the inside of the port, I will double check all the settings on the amp and set like you said, also the amps do not penetrate the enclosure, they are mounted to the outside they just have a cover board over them to hide the wires. Just wondering, what would be the optimal hz to tune the box to in case i decide to rebuild it in the future. here is a pic without the cover board [IMG]https://i169.photobucket.com/albums/u217/bbevil09/CopyofHPIM2786.jpg[/IMG] Thanks for all your help.
Posted By: DYohn
Date Posted: August 04, 2008 at 10:32 PM
That design makes for a clean look, but beware of the amps getting hot since the cooling fins of the heat sinks are covered. Otherwise, nice work! A 15" CVR can be ported much lower since their Fs is 20Hz with optimum probably around 22, but that requires a much longer port. Your setup should sound pretty good. ------------- Support the12volt.com
Posted By: bigbev
Date Posted: August 05, 2008 at 3:17 PM
i did think about the fact that the amps might get hot so i let a little gap around the cutout so some air can get through, the truck is not my daily driver but i do plan on installing a few cooling fans to get some air to the amps. Just one more question, I ask this same question about port size on another site and they told me that i needed to cut my port size in half and make it smaller to around 95-90 square inches. can you think of any reason why they might be telling me that? thanks for your help with eveything 
Posted By: bigbev
Date Posted: August 05, 2008 at 3:19 PM
I meant 85-90 square inches, oops
Posted By: DYohn
Date Posted: August 05, 2008 at 5:06 PM
Making a port smaller will lower the tuning frequency but create more port noise. Changing from 115sqin X15 to 85sqin X15 will lower it by approx. 3Hz in your enclosure. ------------- Support the12volt.com
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