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inverted subs in slot ported


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yungen2003 
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Posted: May 25, 2008 at 9:28 PM / IP Logged  
I realize my first post is a question. Not the best way to start off but I have browed through the forums for a few months. I've searched for this already and read every post about 8. Basically what I'm asking is this. I have 2 Power Bass 12" 4ohm SVC subwoofers RMS 350. Running on a SoundStream XTA 600.2 Amp. Running in Parallel 2ohm resistance. In a Slot ported box made specifically for the subs. If I was to Invert in a box made just for those subs would I need to reverse polarity since I'm Inverting both subs. But they would be out of phase from my other compnent speakers. 2 Polk Audio 5.25"s in the front and 2 PB xtreme 6.5" s in the back. Also the reason I'm asking about the polarity is because other posts havent exactly been clear on Slot ported boxes most were sealed boxes people inverted in. So since a ported box is made for the air movement wouldn't I then keep the subs pos to pos and neg to neg. Since I'm going to be pushing more air into the box and out of the slot port (in the middle of both of the subs)
yungen2003 
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Posted: May 25, 2008 at 9:31 PM / IP Logged  
We'll it wouldn't let me edit my post above but on a side note this is a 1995 nissan altima SE coupe. Figure I'd let you guys know. Don't know if anyone has done this in a Altima 1995 before or not would love for some tips if anyone has before :)
wvsquirrel 
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Posted: May 26, 2008 at 3:08 AM / IP Logged  
I'm not a fan of inverted mounts, but yes you should invert the phase (180degree phase). I just checked the specs on your amp and you don't have a phase switch, so yes I'd say reverse the polarity on both the subs.
As for the enclosure being "made" for the subs, you need to know if it was made for a traditional mount or an inverted mount. The volume of the sub is taken into account when designing enclosures, and when you invert a sub you increase the volume of the enclosure. The port is "tuned" using a particular volume of airspace. If you want to keep an inverted mount then you may need to adjust the enclosure volume to get a better sound.
Sealed enclosures typically give you more "wiggleroom" when manipulating the volume and are a lot easier to deal with than a ported enclosure. However a lot of people will say that a properly tuned ported enclosure will kick the s**t out of sealed one.
Squirrel
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yungen2003 
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Posted: May 26, 2008 at 3:45 AM / IP Logged  
It was made for a Traditional Mount not inverted. Think I should play it by ear and hear how it sounds?
wvsquirrel 
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Posted: May 26, 2008 at 4:27 AM / IP Logged  
I guess the big question is why are you wanting an inverted mount? Some people believe that you get better SPL, but I personally don't believe you do. Or are you just wanting it for the "look"? A lot of prople bought Audiobahn subs because they blinged out their baskets for inverted mounts.
I would hook everything up normally and listen to how it sounds first. Then invert the subs (remembering to reverse the polarity on both subs) and see if you can hear any difference. If it doesn't sound right after you invert the subs then add some boards to the inside walls of the enclosure to decrease the air volume (compensates for the volume of the sub). If you know the displacement volume of your subs then you can figure out exactly what size boards to use. Otherwise you'll just have to experiment a little (make small adjustments at a time). Remember to use screws and secure the boards, otherwise they will vibrate and cause all kinds of havoc and possible damage to the subs inverted subs in slot ported -- posted image.
Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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DYohn 
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Posted: May 26, 2008 at 9:54 AM / IP Logged  

What squirrel says above is correct - the reason your system performs differently is because you've changed the effective volume of the enclosure by inverting the subs - but actually you don't have to change the wiring if both speakers in a 2-sub system are being inverted.  The wiring on the subs can stay the same, although you may have to change the phase of the signal at the amplifier to compensate for total system phase.  But as long as both subs are in the same relative acoustic phase with each other, you can wire them any way you like.

Oh, and as an aside, there is no performance-related reason on earth why someone would want to invert their speakers - although there may be system design reasons why this is done.  But in 99% of the cases, it is only to show off the bling.

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yungen2003 
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Posted: May 26, 2008 at 12:30 PM / IP Logged  
ooo reason...I have had the system for over 2 years :P and I'm about to get some p3's but before that I wanted to invert just to hear how it sounds and if it sounds better then not buy the p3's
wvsquirrel 
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Posted: May 26, 2008 at 6:21 PM / IP Logged  
I'm a fan of Rockford, I run (2) 12" RF Punch HX2's powered by an RF 1000bd.
Which P3's are you looking at? I'm assuming the 12's since that's what you are already running.
If you decide to go with them, the IMO the best match with your amp is (2) of the 4ohm p3's (P3D412), NOT the 2ohm DVC's. Your amp isn't listed as being 1ohm or 2ohm Mono stable, so by using (2) 4ohm DVC's you have 2 options (actually there are more, but only 2 suite your amp):
1) Wire each in parallel for the 2x300w@2ohm Stereo rating.
inverted subs in slot ported -- posted image.
2) Wire the subs in series/parallel for the 1x600w@4ohm Bridged rating.
inverted subs in slot ported -- posted image.
Either way gives you apx. 300w per sub. Since the subs are rated at 500rms you're more than safe. Plus you would have some room for a more powerful amp in the future if you decided to upgrade that too.
Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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yungen2003 
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Member spacespace
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Posted: May 26, 2008 at 7:20 PM / IP Logged  
The amp is 2 ohm stable not 1 ohm I currently have the 2 PowerBass 12's running at 2 ohm Bridged. But yea I see what your saying.
wvsquirrel 
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Posted: May 26, 2008 at 7:45 PM / IP Logged  
All I had to go off of were the specs from Soundstream (which only rate to 4ohm mono stable). That amp has what they call a "phantom channel" that allows you to run (2) 4ohm speakers in stereo as well as (1) 4ohm sub in mono. I believe it's like a 3.6ohm load or something like that.
If you're running (2) 4ohm SVC's bridged wired in parallel then yea you're at a 2ohm mono load. If the amp can take it then you could go for the (2) 2ohm DVC's wired in series/parallel and hope that it holds out.
inverted subs in slot ported -- posted image.
If your amp blows then you could always replace it with a mono-block amp that is rated around 1000x1@2ohm like the RF Power 1000bd or JBL BP1200.1
I used to run stereo amps bridged for subs until I discovered mono amps. You can usually get more watts per dollar, and they tend to hold up a lot better under the abuse inverted subs in slot ported -- posted image.
Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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