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Winisdpro, Infinity Perfect Box


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jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: July 08, 2005 at 11:11 AM / IP Logged  

Hey you Winisd experts out there, could I get some assistance modeling a box I'm thinking of building?

I am not that handy with that program, and even when I do model something up, I am still learning how to interpret the graphs into meaningful information from a listening perspective. I am currently running an Infinity Kappa Perfect 12 in a small 1 cubic foot sealed enclosure. I am underpowing the sub (MTX amp pushing 210 watts RMS) and the sub is rated at 300rms which I believe is lowballing it. I like the sound of the sealed enclosure, but I know that I need it to be larger and I need to feed the sub more power. I like the sound quality, but want more SPL out of the system.

I was going to go ported, but now I think I am going to add a second sub to the system and put them both in a sealed enclosure. However, I want to give each sub more volume to work with (1 cubic foot is factory recommendation, but from what I've heard it will perform better with more volume). I want to build a dual chamber sealed enclosure for the two subs. I will be powering them with 400 watts to each. These are the single 4 ohm voice coil model. I don't have the room for a dual ported enclosure (the box would have to be huge) so sealed it is. This will be going into an Explorer, and I have an area about 40"W x 25"L x 15" H to work with.

Any input would be greatly appreciated.

2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
stevdart 
Platinum - Posts: 5,816
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Joined: January 24, 2004
Location: Pennsylvania, United States
Posted: July 08, 2005 at 12:02 PM / IP Logged  

jdog0411 wrote:
I have an area about 40"W x 25"L x 15" H to work with.

That's 6.5 cubic feet.  A dual ported enclosure will take only 4 to 5.  That may be the type of sound you're looking for, after all.  With either type of box, try going with 1" MDF instead of 3/4", and use extra bracing.  But I don't see the need to try to find an answer by using a modeling program for those subs if you're doing a sealed box.  Infinity wants to stick with 1 cu ft with those, but with the use of the thicker walls.  If you want to make it bigger I would suggest increasing no more than 25%. 

wrote:
the sub is rated at 300rms...I will be powering them with 400 watts to each.

Now that's treading dangerous territory.  If you do this, keep them in no more than 1 cu ft each sealed, extra thick walls and corner braces.  And check the amp's output, too, with a meter.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: July 08, 2005 at 1:48 PM / IP Logged  
Stevdart, do you really think that 400rms would be too much for these subs? I have heard multiple accounts of people running more wattage to the perfects. I'll keep it at 300 if that is going to be a problem.
2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
Poormanq45 
Silver - Posts: 597
Silver spacespace
Joined: October 27, 2004
Location: United States
Posted: July 08, 2005 at 3:11 PM / IP Logged  
Gonna throw in my $0.02 and try to save you the effort.
STuff that box with Polyfill. I mean the box that you currently have.
jdog0411 
Copper - Posts: 150
Copper spacespace
Joined: January 05, 2005
Location: United States
Posted: July 08, 2005 at 3:37 PM / IP Logged  

The box is already stuffed with polyfill from partsexpress.

2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12
Poormanq45 
Silver - Posts: 597
Silver spacespace
Joined: October 27, 2004
Location: United States
Posted: July 08, 2005 at 3:53 PM / IP Logged  
oh, didn't realize that. So you're already giving the sub ~1.25~1.5ft^3. Hmm.
stevdart 
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Location: Pennsylvania, United States
Posted: July 08, 2005 at 5:16 PM / IP Logged  

I'd say this:  don't exceed 300 per if you're going to try ported.  Keep the box at specs if you want to use 400 because the extra volume in the enclosure will make that extra power a critical factor.

The doubling of subs and the big increase in power that you're thinking about will most assuredly make a big difference in the SPL.  You may not want to fudge the recommended specs along with all that.

How thoroughly is the car damped?  A little increase in sub SPL and you normally need more;  a big increase means you need a lot more.  Good damping and strong walls will be the key.  My next box I'm going to use a 2-ply method...3/4" MDF plus a layer of 1/4" exterior grade plywood on the outside, making a very strong 1" thick box.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Poormanq45 
Silver - Posts: 597
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Joined: October 27, 2004
Location: United States
Posted: July 08, 2005 at 5:32 PM / IP Logged  
Stevdart: Unless they are completely bonded together you won't gain much strength.
I suggest using 6ply furniture grade plywood with the inside sealed and covered with anything to absorb sound.
stevdart 
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Location: Pennsylvania, United States
Posted: July 08, 2005 at 5:45 PM / IP Logged  

Yes, of course they will be bonded.  Gorilla glue and screws.  Long time ago I learned that a key to stopping flex is not only the thickness but the number of layers.  For example, required for minimal flexing underlayment for large floor ceramic:  1 1/4" thick in TWO layers, nailed or screwed in a 6" grid pattern.  That same principle would apply anywhere you want the least flex, and the bonding materials  and grid measurements are varied as appropriate for the project.

With the flooring underlayment, layers don't mean the layers in a single piece of plywood because each one of the two layers are multi-layered themselves.

And exterior grade plywood uses bonding between the layers that will withstand some moisture conditions without delaminating.

...just an idea I want to try...

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
sedate 
Silver - Posts: 1,173
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Joined: July 03, 2004
Location: Colorado, United States
Posted: July 09, 2005 at 3:18 AM / IP Logged  

Yo jdog.

Hmm.  Whoa...   from a guy that has installed 2x12" Perfect's in a half-dozen sealed enclosures.. (not one more than 1.25/cft/sub) ....  I tell ya .. that woofer is.. eh..  small and sealed.  Lotsa power.  No ports.. larger boxes to gain flatter response curves.. not with this woofer.. and..... screw polyfill or acousitstuff.  No.  Not a Kappa Perfect .

The Kappa Perfect likes a nice small sealed box.  *Empty inside*  1 c/ft at most.  Read the woofer man.. 96dB in car at 1w?  Huh?  Truth be told, I don't get it either.  It is LOOOSE.  Like.. if it were a woman.. it'd blow your mind but leave you wondering why... eh?

Hehe.  Naww.. BS semantics aside, that woofer personfies 'boomy'   ...  it quickly overextends and sounds horrid in large boxes..... granted... playing smoother music (I really like rap so what do I know about sq? =) it always plays nice.. but.. for any sort of sq at any sort of output.. this thing really doesn't do well in large enclosures.  Very quickly sounds like an over-gained, over-extended 8". 

You want two of these?  Okay.  Install both of them in a common 1'/sub enclosure and give'm 500/watts between 'em.  I *seriously* doubt you will have output issues.

Oh yea... lets kill this thing right here.. I've made this mistake:

what I've heard it will perform better with more volume

No.  'Perform better' in terms of a stereo is massively under-qualified term. 

What a larger box does for a woofer is nothing so much as 'perform better' as 'have a flatter reponse curve' ...

Woofers, IN GENERAL, sonically perform better with larger airspace to work with.  This is because as airspace increases, the pressure exerted on the woofer cone also commensurately decreases, even concurrent with the depth of the note being played.  As such, deeper, more power intensive notes, sound louder because they take a wee bit less power to play b/c of the larger enclousure not resricting woofer-cone movement as much. 

Now, what the general *theory* is behind the operation of a speaker in an enclosure and *actual performace* are.. especially in this case..  sometimes totally different.  The 'voicing' of the driver.. power available... construction in every aspect..  all totally effect this particular dynamic. 

Like I say, the Perfect 12 just isn't a woofer that works like this... very quickly.. espeically when plied with any sort of power..  gets quite loud and then quite boomy and muddy.  Any box I built for my pair larger than 1.1 or 1.0/cft just had a nasty porky quality.  Poke around message boards.  This is a popular speaker.. lotsa others had the same experience!

"I'm finished!" - Daniel Plainview

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