Duel Sub problem.

[flyguy]

Okay... first of all...i hooked this up and built the box myself... so that could be the problem right there... buy anyways...it seems to me that one sub is doing all the work while the other is just hanging out. Its going... but I cant tell its there... My set up is a RF 400 amp in 2 channel mode bridged to two MTX 10" subs. The only wierd thing about my setup is that the subs dont exactly match... one is a MTX 6000 and the other is a MTX Blue Thunder (Legend series?) anyways... as far as specs go, they are very similar... both with a 250 watt rms capacity, 4 olms, and similar volume requirements... The 6000 series is waaaaaaay out thumping the blue thunder. but when I had them singled out... I could hardly tell the diffrence... hmmm... tomorrow Im going to fiddle with the wiring... but till then, I wanted to know whay you guys think...

nick

 

[flyguy]

I fiddled with the wiring some more... and now the 2nd sub is working better I think. Maybe its just "tighter" than the other one. Hmmm.. okay.. but a new concern has arose... my amp overheated in like 6 minutes. Or I assume its overheating...it gets real hot... and then the subs cut out. Whats up with that? Do I have it cranked up to much? Hmm...

nick

 

[Lamah]

fosgates have been know to suck like that =/. Your ohm load is probably too low. if you have them wired in parrallel, then they'd be at a 2 ohm load. i'm not sure if fosgate's are stable to 2 ohm.

on a side note, its usually not a good idea to mix sub types because, even tho they have similar specs. they will still sound different

good luck,
Jeff aka Lamah

 

[pacman]

Lamah is right, your amp may not like a two ohm load (if your subs are wired in parallel - i.e. both positive posts connected to positive feed from amp and both negative posts connected to negative feed from amp). You might want to try running in series (i.e. connect neg from amp to sub1 neg, connect that sub1 positive to the neg of sub2, then connect sub2 positive to amp positive - this will essentially give you an 8 ohm load). You could also run in stereo mode and connect each sub to a separate channel...

Also, be sure you haven't accidentally wired one sub out of phase (swapped wires on one sub but not the other). This can cause the bass response to "disappear".

 

[flyguy]

I tried to post earlier but no dice... anyways...ive got it wired up how the manual says... It should be a 4olm load. If I run them in series... wouldnt I only be getting half the power? Im not sure about these things.. but Im not doing anything that the manual doesnt say!

nick

 

[mrsteve]

Lamah - I ran my Rockford Fosgate amp bridged @ 2 ohms mono for six months with no overheating or distortion problem whatsoever. The amp was mounted behind a trim panel in the rear so it didn't even have proper airflow to help cool it down. My friend's have run their Fosgate amps @ 2 ohms mono also with no problems.

As for the problem with your subs. One of your main problems is the fact that you are using different subs. This is a big no-no. Different subs have different voice coil impedance, different sensitivities, and different frequency responses, not to mention many important differences. Check all your wiring there is probably a simple solution to your problem.

Steve

 

[flyguy]

What about my overheating problem? Eh? It would overheat when I only had one sub on it too.... but that was usually after about 2 hours... Sigh

 

[Lamah]

with 2 4 ohm subs, you can only have 2 ohm or 8 ohm loads. as for over heating, its probably because the amp doesnt like the load

 

[JTang]

When you're saying it's running on "2 channel mode" (see first post), is this a 2 channel amp, or is it a 4 channel amp that you're bridging to two channels each? The new RF 400s I think are only 4 channels. Even if you bridged one sub to each channel, it should be okay. If it's your normal 2 channel, don't bridge unless you're absolutely sure your amp can run the 2 sole channels bridged in 2 ohms *mono*. Many people get confused when they see the "Stable down to 2 ohms" feature. This usually means stable down to two ohms PER channel. If you bridge it with 2 ohms, each channel is actually running at 1 ohm a piece, way more than most amps can handle. I don't believe that even the current line of RF power amps run that low like they used to.

While your subs have similar specs, they are a little different. It won't hurt your subs, but there is a chance that it will actually be detrimental to the sound. Since they are different, their responses to the same signal will be different, and a chance of wave cancellation may occur in some frequencies. Not saying it's guaranteed to be that way, but in theory, very possible.

Good luck,
Jon

 

[flyguy]

Okay guys... This is getting hard... this is the manual for the amp I have... and Ive got it wired like it says for 2 channel mode.

http://rockets2.rockfordcorp.com/Download_EN/PDF/Amplifiers/Manuals/2000-PunchMultiCh-MAN.pdf

and I am running basicly 2 6000 series subs. I think they are 4 olm.

nick

 

[Lamah]

if its setup for 2 channel, then asside from the way it sounds, different subs wouldnt stop it from working properly

 

[flyguy]

but why am I overheating so fast! Sigh.

 

[mrsteve]

Where is your amp mounted? Is it getting proper airflow? Are your gains turned all the way up? Or your wiring could be wrong which would send a really low speaker load to the amp causing it to overheat. There could just be a problem with the amp entirely.

Steve

 

[flyguy]

Maybe everything that comes near me just breaks. I just bought a new CPU that wont work too. The amp is mounted on the back of my rear seats... so its got good airflow... the amp was professionally installed... and the gains are kinda high... how high can they be? I would say they are about 75% up or so. I guess thats a bit high? But the girls like the boom... the cars that go boom. Man...I need to get a Cap too... every time my sub hits my battery gauge goes nuts.

nick

 

[Lamah]

the cars that go boom .... that song sucks. heh

the gain can be pretty high. why would they have it if the amp couldnt take it ? just dont turn the hu all the way up too. Also, like i said, fosgates have been known to have that kind of problem. You might wanna take it to a shop and have them look at it.

i also need a cap. i can get a ppi 1.0 farad for ~75 shipped i think. but i need a body lift first =/

good luck in your qwest for bass,
Jeff aka Lamah

 

[flyguy]

Whats the Hu? hmmm..

 

[mrsteve]

HU=head unit

if your gains were set all the way the amp is producing maximum power very quickly. It's hard to diagnose your problem with out seeing it first hand. I'd take it in to a car audio shop and have them check it out.

Steve

 

[flyguy]

Yeah.. the gain is all the way up on the head unit... hehe. but...I should have the head unit all the way up and then the amp on the low side then?

nick

 

[JTang]

Hmm,

It looks pretty simple, no? I looked at the manual, and the only thing I can think of, short of miswiring would be not setting the switch to 2 channel mode. Why don't you unhook the speakers one day, and keep the amp on like you normally would with the stereo. See if it's still getting really hot or not. If it is, maybe it's grounding out on the chassis, if not, then the speakers aren't 4 ohms of you're just bumpin too hard!

 

[flyguy]

I must be bunpin to hard... cuz it doesnt overheat at all when the volumes down... only when its neat all the way up. Damn...I like it loud. hehe