completed my replacement of all sound equipment and polyfill of the soundbar and stock sub box, speakers are sounding nice and crisp, the final thing i need to get dialed in are the settings on amp for the sub. I've been through a few guides and am most of the way there, I think there's still a little room for improvement to get a bit more bass out of it and get it matching up more nicely with the rest of the system. Sub is an SWR-843D in the stock 2012 JK box, I constructed a 19mm spacer to fit it and stuffed as much polyfill as I could into the box with the sub being able to be pushed in without too much difficulty. Amp is a PDX V9 5 channel, feeding the sub 500w at 4 ohms.

To adjust the amp I switched off the subsonic filter and set the LPF a touch above 80hz. I then set sub output on the HU 2/3 of the way up and cranked up the volume on a 56hz sound clip while I notched up the gain until I noticed distortion, I then backed the gain off slightly. Is there a better method? Any tips or pointers to good guides would be very helpful to me, most of what ive done is based on yahoo answers type info.

 

other than using an o-scope (not what I would recommend) you pretty much hit the nail on the head as far as setting your gains.

as for crossover points, 80hz is a good starting point... I used to run everything crossed over as low as possible, but in the last few installs have started bringing the crossovers higher, letting the sub assume some of the low midbass (2-way plus sub setup, like our JK's) and have gotten better reliability and better overall day to day listening. So, subs low-passed at around 80 - 100hz, fronts and bar high crossed over at 80 - 100hz, 12db slope so there is a decent amount of overlap. (your ears will tell you where a good crossover point is, listen, tune, listen, tune)

Polyfill is really only useful for enclosures that have too little acoustic volume (airspace). the polyfil (about 1lb per cubic foot) slows down the air inside the enclosure effectively making it seem as though there is a little more airspace inside the enclosure. Too much polyfil and it will have the opposite effect, where it actually consumes the existing acoustic volume

 

This may be causing me some problems. Currently I've got the sub almost where I want it, but it's still coming up a little short especially on some of the more demanding tracks. I just can't seem to get enough out of it before it starts distorting. I know it's only an 8" but I'm not looking for any monster bass and what makes me most suspicious is that the infinity sub was able to produce A LOT more. I suspected I might have the wrong sub for the enclosure it's in, at the moment I have it packed pretty tight with polyfil though so will try removing half and then all and see if I can find any difference.

Which aftermarket subs are you guys having success with in the stock box? Two I think I've seen mentioned are the JL 8w3 and the 8" pioneer shallow mount?

 

[QUOTE=Surinam;3491245]other than using an o-scope (not what I would recommend) /QUOTE]

I'm of the theory that the human ear isn't sensitive enough to determine the breaking point between a cliped signal and a clean signal. Although most people don't have acces to ( or even know how to use ) an O-Scope, a multimeter is the next best thing. Using an instrament to identify where the cliping begins will atleast give you a referance of your maximum settings and help you localize any problems with your driver.

How to Set Amp Gain With a Multimeter | eHow.com

 

[QUOTE=JK-Ford;3516933]thanks for the link, will check and reset gains using this method when I pull the sub to remove polyfil. I've searched and found a few guys who have this sub sounding great in the stock box, seems i've got something wrong somewhere