Hi all,

I am a long time reader but first time poster. On the weekend I have made a custom ported box for my 2 subs but have come across a problem I haven't had before. The box is ok and everything fits, and I am pretty sure my wiring is all good but when both subs are connected there is hardly any bass. It has me confused as when only 1 is hooked up (I tried it with both), it is bloody loud. The subs are Fusion Powerplant 12" DVC 4ohm with the coils wired in parallel to a 2ohm load and bridged to my Fusion Powerplant 600wrms 4 ch amp (I know my amp isn't rated for 2ohm bridged but i'm OK with that). The box is approx 3.5 cu ft with a 4" port at 7.5" long made from MDF. I have tried reversing the polarity on both or individual subs and it sounded a little better with them on different polarities but I am still getting muffled soft bass that doesn't hit. I used various box calculators before I made it and read many tutorials too.

Anyone have any ideas what I did wrong? Any help would be appreciated.

Here are some pics of my setup

http://i422.photobucket.com/albums/pp304/c...DC081020003.jpg
http://i422.photobucket.com/albums/pp304/c...DC081020002.jpg

hrm. if you've tried each sub and they both work fine, then you hook them together and they dont work...I suspect....

its the wiring!

you need to give a bit more detail about how your subs are wired up.

Is each sub (wired in parralel to 2ohm) bridged off two channels? so that sub No. 1 is on channels 1+2, and sub no. 2 is on channels 3+4?

or,

Is each sub (wired in parallel to 2ohm) then paralleled together, so that the final load is 1ohm, or seriesed togther so the final load is 4 ohm? Do you then run this configuration off channels 3+4?

this is what it should look like:

Each sub is wired to 2ohm and run from seperate channels on the amp. The subs are not connected to each other in any way. I am 99.67% sure the terminals I put on the back don't have any bridging plates on the back but will pull a sub out to double check at lunch.

So you use the 4 channel solely to power the subs is that right? So 1 and 2 power sub1, 3 and 4 power sub2? It could be that the amp isn't able to cope with a heavy demand if you're using it solely for subbass duties, and as such the power supply can't keep up and you're getting less power being output.

To test, wire the subs in series (to show 8ohms) and wire them back up, if the bass improves then it is the fact you are both wiring the subs wrong for the amp and the amp is not able to cope with a heavy load.

if my powers of deduction serve me correctly, you have a 2ohm sub bridged on channels 1+2, and a 2 ohm sub bridged on channels 3+4.

this means each channel on your amp sees 1ohm. I've written extensively elsewhere about the dangers of this (!), if in doubt follow the quote in 92gen2's signature block.

hence, when you hook up both subs, the amp simply cant cope, and does its best to shut down.

Do what louie says. Wire them up to 8 ohm, then bridge at the amp. like this:

I have been using this amp to power both subs for a few weeks now without any problems. They were previously in different boxes, 1 ported and 1 sealed. That is why I made the new box. I have tried different gain settings and volume settings without any improvement. I have taken a couple more pics of the back of the sub and the terminal on the box

http://i422.photobucket.com/albums/pp304/c...DC081020005.jpg - Sub in parallel
http://i422.photobucket.com/albums/pp304/c...DC081020006.jpg - Back of box terminal
http://i422.photobucket.com/albums/pp304/c...DC081020007.jpg - Amp wiring to box terminal



I am also aware of the dangers of wiring the amp in this way and have read many threads about it. There is no protection coming up on the amp and it still maintains a fairly low temperature and both channels are still working. The only thing I have changed in the setup is the box. It was wired this way 2 days ago without any problems.

Thanks for the ideas so far.

I will try the series setup soon and see if there is any difference

so you have each sub bridged over 2 channels each?

sub1 bridged on channels 1+2
sub2 bridged on channels 3+4?

yes Matt, that is correct

I have just tested the subs wired in series and got pretty much the same result. When only 1 is hooked up it works great with hard hits but when both are hooked up it goes a fair bit softer and doesn't really hit. I did notice that one of the subs is Excursing (if that is the correct term for bouncing more) more than the other when they are both connected. This is really starting to annoy me, i have setup, installed, or configured dozens of stereos and never had this problem.

Could it be a problem with the box? This is the first box I have made. I tried to space the subs at the same distance from the sides and the port on the center line of the box.

hmmm....have you checked each sub individually? on each set of channels?

recheck all your wiring, ie connections at the sub (could be a loose wire?), connections at the amp, power and especially ground connections.

wired in series, as shown above to show an 8ohm load. That way you can be sure its not the impedence load causing the problem.

ie test sub 1 on channels 1+2
then test it on channels 3+4

then do the same for sub2.

I strongly doubt its the box. Is it a single chamber or dual chamber box?

I have checked and double checked all of the wire connections so I know they are all OK. The amp is drawing plenty of current as my interior light is more like a strobe when I turn it up even with the engine running.

The box is a single chamber approx 3.5 cu ft with a single 4" port.

Could the excursion problem be caused by having the subs wired with different polarities?

its possible but not to the extent you're describing. grab a 1.5v battery, grab the leads and touch them briefly to the battery's terminals. That way you can see if the cone goes in or out depending on the polarity - make sure they're both pushing out. Then wire them back up to the amp correctly and bang. you're done.

I'm also at the extent of my knowledge helpfulness too...might have to ask someone like Shiny_car in the beginners section!

OK, I think I may have partially solved this problem. I think part of the problem was with my RCA's not connecting properly. I had a spare splitter so I split the signal with the good plug and presto, instantly it sounded better. They are still wired in series so after work i might try and run them in parallel again (an overload the amp) to see if the problem comes back again.

I did notice that they are hitting full excursion easier when they are both connected. Is there anything I can do to reduce this?

turn the gains down?



2 subs off approximately 100 watts each shouldnt be hitting "full excursion"....?

of course. I forgot I cranked up the gains when I wired into series. I was also playing a bass mechanik song at high volume with plenty of bass in the EQ settings. Oops.

Thanks for all the help Matt. It is most appreciated.

baaahahahahaha!

nice way to "test" an amp!