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excursion/air velocity too high?

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=98031
Printed Date: May 11, 2025 at 5:00 AM


Topic: excursion/air velocity too high?

Posted By: dtundra578
Subject: excursion/air velocity too high?
Date Posted: October 16, 2007 at 7:33 PM

Alright,
So I have been trying to put together my first real system for the past couple of weeks and unfortunately did not find this forum until last night. Which by the way has already been very helpful.

My problem, I already bought the subs and started building the box before I got my hands on winISD, and since then I have some concerns with the setup I am attempting to use.

Let me intro a little;
I have an 07 Tundra, with very little room to work with under the back seats. I bought two 12" Pioneer Premier shallow mounts (TS-SW1241D). I picked up an Eclipse 34230 Amp.

Now for the box that I have already 85% built...I only have .66 cu ft in one chamber and .65 in the other. Now here is the part where I think I f'ed up. I ported one of the enclosures thinking I would have the nice tight response from the sealed and get a little more SPL (right use?) from the ported enclosure. BUT, I didn't see the recommended port specs in the sub manual before I built one....first oops.

Now I need to know can this be fixed? Can I just make the port longer? Can I seal it back up?

I took some screenshots of widISD for those of you that know everything, from what I read I gather that my "rear air velocity" of ~227ft/s @ ~70Hz is going to sound like crap?? Also the cone excursion looks like it could be fatal for my sub?

Here are the screen captures:

Ported Air Velocity with current port dimensions
posted_image

Ported Air Velocity with extended 11 inch port
posted_image

Cone Excursion chart @ 350 RMS Watts
posted_image

Just for more input here are the SPL and Transfer Function Magnitude levels
posted_image
posted_image

My bottom line questions are: is my box shot? Is it going to sound like crap? If so is it fixable? Thanks a million for any info the experts out there throw my way.




Replies:

Posted By: dtundra578
Date Posted: October 16, 2007 at 7:35 PM
I just realized you can't hardly see any of those pictures...how to I upload them so they are visible?




Posted By: stevdart
Date Posted: October 16, 2007 at 9:48 PM

You can't unless you use a pic server, but don't bother because it doesn't matter.  What matters is:  Use ONE type of alignment for your subs, not both sealed and ported.  It's a myth that you can "get the best of both worlds" by trying what you intended;  if it really worked (as in sounding better than ***) you would see it as commonplace, as you are not the first one who thought of it.  posted_image

.66 cu ft is far too small for any vented sub enclosure and is on the small side for the majority of subs using sealed alignments as well.  Fix the damage by replacing the baffle that you cut the hole in.  Make both chambers sealed.



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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: dtundra578
Date Posted: October 16, 2007 at 10:32 PM
Almost too simple..ha, ok. Thanks for the quick reply! You were just the guy I was hoping would respond, awesome info on winISD also.

I didn't think I was re-inventing the wheel...Im just a noob...

Anyways one follow up question, in attempting to make the look of the install clean I used one piece for the whole face of the box (the part closest to the front of the seat) and that is where the port is...can I put another 3/4" piece on the inside and seal the crap out of it or should I start over or.....??

Thanks




Posted By: sarcomax
Date Posted: October 17, 2007 at 1:12 PM

As long as you have an air tight seal you will not have any problems. If it was me I would replace the front panel, but your cutting skills might be better than mine. I have the genitics of my mom, as I can't draw a straight line with a ruler, much less follow one with a saw...



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Posted By: dtundra578
Date Posted: October 18, 2007 at 2:33 PM
well, I cut a piece and slapped it in there nice and tight...I think it should be fine. Thanks for the help!

I would replace the front baffle but the face is designed to go all the way across my under seat area (covering my amp area and another box front. Its easier to keep in place and looks a little nicer.

So replacing that would totally screw up my other 90% complete box





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