T/S determinants vs. manufacture recommen

Here's the deal. I ran the T/S parameters through the ported.xls spreadsheet that I got from Brian Steele's The Subwoofer DIY Site. What I came up with is an optimum box of 1.03 cu.ft. The thing that gets me is that Pioneer reccommends a 1.65 +/- 10% enclosure. That's a big difference if you ask me.

I'm assuming when you say "optimum" you mean that it is for a .707 alignment correct?  Well that alignment just provides the flattest response anechoic.  When you put the driver into a vehicle, things change. You might want a larger or smaller enclosure depending on personal tastes/goals.

Also, some manufacturers recomend enclosures based on the market the driver is designed for.  If it is for a teen that wants it as loud as possible, they might recomend a smaller enclosure to get a boost in the response.  We actually recomend a little larger enclosure to give a little more low end.

Here's how it works: Qtc. goes up when enclosure size goes down.  The higher the Qtc. the more ringing you will get, and it looks very similar to harmonic distortions.  Going with a smaller enclosure you get more ringing, less low end and an increasing peak in the response.  Try playing with that program and see what happens to the response as you change the size of the enclosure.

Steven Kephart

Adire Audio

If this is the same as Qb, then actually the alignment was set to .90, however that only affected the sealed box (and resulted in a Vb of .30 ???). The Qb of the 1.65 cu.ft box is .49, and the 1.03 cu ft. is .56. I did go back and realize that I didn't input these numbers correctly though becuase I didn't carry them over from the alignments page.

This is exactly what I started building the box to. I have it set now to where it will be right around 1.75-1.80 cu. ft when finished (Pioneer reccommends 1.65 +/- 10%). However, this was before I downloaded the excel sheet and pluged in any theile-small parameters. 

I've been playing with this program for a few days now, and I can tell that the larger the box, the more low end. I actually have a picture of the FR curve up here: http://www.j-body.org/forums/read.php?f=4&i=81624&t=81624 (I did update it after i realized i did not carry over the correct quantities for Qb).

hence why when the "optimum's" came up so small on the excel spreadsheet, I got worried :)

Ah, you are talking about ported enclosures.  Well in that case, the reason why a manufacturer would recomend a larger enclosure is to shorten the port length a little bit.  BTW, if you want a good free box building software, I would recomend Unibox.  It seems to be the most accurate out there.  Here's the link: http://www.danbbs.dk/~ko/ubmodel.htm

But even still, I wouldn't fully trust any freeware's ported recomendations fully. 

Steven Kephart

Adire Audio

dpaton wrote: Steven Kephart wrote: But even still, I wouldn't fully trust any freeware's ported recomendations fully.  And beyond that, I don't fully trust manufacturer's specifications (no offense Steven) Every driver I've ever used differed from it's spec sheet. Sometimes it wasn't enough to matter, other times it was too much to stand. In my profession, everything gets measured in house to determine what it does in reallife, not just on a spec sheet. I guess it carries over into my hobbies as well. It also keeps manufacturers on their toes when they know people are checking their work -dave

Absolutely no offense taken.  You actually bring up a good point on another reason to really not trust the programs.  It is because of driver tolerances (which is the reason you see such differences in parameters).  Typical driver tolerances are about 20%.  These huge tolerances are mainly due to the spider, which is why I can't wait till we get our new Arachnid spider on our drivers which will pretty much eliminate driver tolerances. 

Also, manufacturer enclosure recomendations are to give people who don't know what they are doing something to go by.  If you look at our site, you will see we offer not one, but several sizes and explain what to expect from each. 

Steven Kephart

Adire Audio

Thanks guys. It's that exact reason that I turned here to seek some advice on how I should build the box. What I think I will just do is build it to 1.8 ft^3, and insert dividers until I'm happy with what I hear. I'll try it at just the 1.8 first, then the 1.0, then inbetween, and so on and so forth. 

I'm aslo going to play around with that other box program a bit. I don't have the patience for it right now, I'm too distracted by the weather channel and that damn storm that is delaying my FSU vs. UM game.

I'm trying to prove to some guys at work that the products themselves are not nearly as important as the building process of the box. Some of my buddies seem to think the only way to get anything good is to spend thousands of dollars. I've spent around of $600 total (HU, speakers, sub, amp, deadening, and materials/accessories). I know I'm not going to have the best stereo system in the world, but I'll be out much less if it get's stolen (like one already has), and I have another car to put my good stuff in