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WinISD what does it mean?


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jl_tulane 
Member - Posts: 6
Member spacespace
Joined: March 24, 2005
Location: United States
Posted: June 01, 2005 at 8:44 AM / IP Logged  

I have some questions about WinISD I was hoping someone could help me with.  I am limited with space and I already have a pre-fab box to fit under my back seat.

1. I have a 2 subwoofer divided enclosure . Should I make the number of drivers 2, and just double the space for 1 of the divisions, or do them separately?

2. How much "volume" can I expect to make the effective enclosure by adding polyfill?  I have heard that 10% is tops.  How accurate is this?

3. What does the -3db line represent?  The enclosure is sealed, so there are no ports to tune.  I read the help index and it kind of explains that this is where the box in effect "runs of steam."  But what does this mean?  This brings me to my next question:

4. When setting my amplifier what should I set the frequency at?  Should I set it at the corresponding -3db frequency, or the frequency that obtains max SPL or what?

5. Lastly, when setting my amp gains, what frequency test tone should I use, and does anybody know where I can download one?

Thanks for any help.  Oh and by the way I am trying to squeeze as much SPL as possible out of 2 12's in a Chevy extended cab.  I know I may be asking for much and I would probably be better going with 10's, but I just like the deeper sound of the 12's and if I could get them to sound like they were in a car without sacrificing too much space then it would be awesome.

Nodestiny 
Copper - Posts: 85
Copper spacespace
Joined: May 26, 2005
Location: United States
Posted: June 01, 2005 at 8:55 AM / IP Logged  
1. if you put in multiple subs, it figures a common chamber box. If you are going to seperate the airspace inside the box, just use 1 woofer in the dedicated airspace.
2. There was actualy a good study done on this, i wish i could find the link. Basicly, up to 30% gain with 1.5lbs of pollyfill per 1 cubic ft UNDER 3 cubes. Anything over 3 cubes and best results were 1lb of pollyfill per 1 cubic ft OVER 3 cubes (offering i think up to 25% increase). It might have been more or less, but 1.5lbs per 1 cube was found to offer the most gain.
3. Your -3dB point, or commonly known as F3, is the point where, in a large unrestricted airspace such as outdoors, approximatly 3 ft in front of the sub, would drop 3dB in volume. This is useful to know because if you compare sub or box A and B, and the F3 is 4Hz lower in one or the other, it lets you know which one will hit lower notes better (and commonly a flatter response, AKA better SQ). Just remember, -/+3dB is the common point where the human ear detects volume change. Though some people can hear up to 1dB change.
4. What is the goal of the system? If it is SPL, do the lowpass Xover at aprroximatly 90Hz. If it is SQ, it depends on your front end. If you front end plays easily down to 60Hz, Xover around 60Hz. My front end is a highpass Xover at 50Hz and subwoofer is lowpass Xover at 50Hz. Since the Xover point puts a -3dB in (so at 50Hz in my case either way), the center point (50Hz) will basicly gain its 3db since they are playing the same frequency, creating a near seamless transition.
5. It seems 55 or 60Hz is the best way to set gains (whenever using a DMM, anyways). I used to have a link, but cant find it to test tones. Use Adobe Auditition (free trial @ download.com) and use the generator, you can create your own tones.
Hope that helps
04 dodge neon SXT
(2) Oz Audio Matrix Elite 12"s sealed in 4 cube fiberglass enclosure, powered by HiFonics BX1605D
Oz Audio Matrix 180cs 6.5" component set power by HiFonics ZX4000
jeffchilcott 
Platinum - Posts: 2,483
Platinum spacespace
Joined: April 11, 2002
Location: United States
Posted: June 01, 2005 at 9:42 AM / IP Logged  
If you already have win ISD, It has a tone generator on it.     I have the program loaded on my laptop so I just run out to whatever vehicle I am working on and plug it in.
2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place
jl_tulane 
Member - Posts: 6
Member spacespace
Joined: March 24, 2005
Location: United States
Posted: June 01, 2005 at 3:59 PM / IP Logged  

I was looking at the help index and found a paragraph that said you could help achieve extremely low cutoff frequencies with sealed boxes by building something called a "Linkwitz-Transform equalizer."  Is this possible, and if so, what does it really mean?  Is it difficult to construct?  I found a website where I could just plug in Fsc and Qtc and what that weird -3db number you are trying to get to and it would tell you what size caps and resistors to put in.  I was wondering if you think this may help increase SPL at all.  I want to squeeze as much as possible out of my system, without sacrificing the space to build a huge box.

PS, a pound and a half of polyfill seems like it is going to be a lot.  Should I be squeezing it and squishing it down in there?

Nodestiny 
Copper - Posts: 85
Copper spacespace
Joined: May 26, 2005
Location: United States
Posted: June 01, 2005 at 4:12 PM / IP Logged  
basicly, get a 20oz bag per 1 cubic ft. It will be kind of tight... ill have to try to dig up the link again... somebody did some very good testing and this is what the outcame was...
04 dodge neon SXT
(2) Oz Audio Matrix Elite 12"s sealed in 4 cube fiberglass enclosure, powered by HiFonics BX1605D
Oz Audio Matrix 180cs 6.5" component set power by HiFonics ZX4000

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