34hz ported sub?
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=118480
Printed Date: May 12, 2025 at 2:47 PM
Topic: 34hz ported sub?
Posted By: napew2008
Subject: 34hz ported sub?
Date Posted: December 13, 2009 at 11:11 AM
Hi. I'm having trouble understanding my system and what's been built for me. I have a 1999 for expedition. I took out the original console, and had one custom made with a 10 inch DD 9510 subwoofer (looks great but not the problem). Its a ported box with a tuning of 34HZ is what the guy says (he says he did a sweep using something to help determine the tuning of box and port). What has me baffled is that my deck has settings of 50-80 hz for subwoofer, and so does my amp. (I have a pioneer f90 and an old rockford punch mono 1000bd), but why then is the box tuned to 34 HZ if my deck filters from 50 Hz minimum? Should the port be shortened to match the deck's filtering? Is the sound or performance afftected in any way? Should the box be tuned to 50 Hz then? any suggestions?
Replies:
Posted By: i am an idiot
Date Posted: December 13, 2009 at 12:35 PM
The crossover allows 50Hz and below to get through the amp. Or 80 and below. A ported box does not like to play any frequency below the tuned frequency. If you tune it any higher than it is now, you will not be happy.
Posted By: napew2008
Date Posted: December 14, 2009 at 4:05 PM
So does that mean I should re-tune the port or shorten the port so the box is tuned at 50 hz instead of 34 since my decks crossover is adjusted from 50 hz?
Posted By: j.reed
Date Posted: December 14, 2009 at 4:08 PM
No it does not. I think "i am" was pretty clear. Your deck is crossed at 50Hz. So the deck is sending 50Hz- 20Hz to the sub. Nothing higher than 50hz is going to the sub. If you rasied tune to 50Hz. Everything lower than 50HZ would be muted and roll off to nothing because of the enclosure tune. Everything higher than 50Hz would be cut off by the crossover.
What are your box dimensions and port dimension? Is there a problem with what you are hearing? ------------- 
Posted By: napew2008
Date Posted: December 16, 2009 at 1:40 PM
No. I only wanted clarifying to why the box is tuned to 34 hz and and my amp is crossed at only 50 hz. That's what I set it as.
Posted By: stevdart
Date Posted: December 16, 2009 at 4:30 PM
napew2008, you're looking for a relationship of those frequencies that does not exist. They are not relative to each other. The 50Hz is a crossover frequency that acts to separate the musical content from the midrange speakers to the subwoofer. The 34Hz is the tuning frequency of the enclosure that holds the subwoofer, so that, centered at that frequency, the box adds additional tone to the subsonic music. If it were a sealed box you would not have a tuning frequency to be confused about. ------------- 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: j.reed
Date Posted: December 16, 2009 at 4:42 PM
stevdart wrote:
napew2008, you're looking for a relationship of those frequencies that does not exist. They are not relative to each other. The 50Hz is a crossover frequency that acts to separate the musical content from the midrange speakers to the subwoofer. The 34Hz is the tuning frequency of the enclosure that holds the subwoofer, so that, centered at that frequency, the box adds additional tone to the subsonic music.
If it were a sealed box you would not have a tuning frequency to be confused about.
Well put. -------------
Posted By: i am an idiot
Date Posted: December 16, 2009 at 5:06 PM
I do not know what kind of drivers you have for mid bass, but chances are you are missing a lot of usefull information by having your subs crossed at 50Hz. 80 would probably be a much better choice.
Posted By: napew2008
Date Posted: December 16, 2009 at 5:16 PM
Thank you for responding. I have a separate amp to power my fronts. Its a jl 300/4;good amp.
Posted By: i am an idiot
Date Posted: December 16, 2009 at 10:28 PM
Mid bass driver = speakers. Unless you have some 8 inch woofers connected to the 300/4 you have to be missing the info from 50 to at least 150Hz. I would at least listen to it crossed over at 80 or maybe even 120 Hz.
Posted By: napew2008
Date Posted: December 17, 2009 at 3:42 AM
My fronts(mids) are crosed at 80 hz,yes. They sound pretty good there.
Posted By: stevdart
Date Posted: December 17, 2009 at 6:30 AM
Crossover the sub at the same frequency as the mids. So if the mids are responsible for upwards of 80 Hz, the sub is responsible for all that is lower than 80 Hz. With the setting as you have it now, the sub crossed at 50 Hz, there is a huge hole in the music...that is, 50 to 80 Hz is missing or at least severely attenuated. Get it? It's important that you understand the reason for crossovers if you are to tweak this system yourself. ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
|