Ok, so I finally broke down and bought a couple subs. not the greatest things on the world but it sounds decent. The subs are 4 ohm and single voice coil. They are rated at 150 rms and 400 peak(Rockford Fosgate).They are also in a sealed box. The amp I am running is 75 x 2 and 150 bridged mono(older Rockford Fosgate).

My question is how should I hook them up to get the best "bang for the buck" so to speak?? Right now they are just hooked up in parallel, one sub + to the other sub + to the amp + and same with the negative.

Right now I have to turn the gain all the way up, the sub level on my deck all the way up and the bass on the deck all the way up to get any kind of bass. My thoughts were to either find a better way to hook up the subs, or port the box. What should I do??

That is the best way to wire the subs to get the most power. I don't think you amp can handle that low of a load (2ohms mono). You can get a ported box made to specs, but honestly, you need to upgrade to a better amp. And make sure it is 1ohm stable (stereo, ie. 2ohms mono).
Sorry if that isn't what you wanted to hear.

Allan
2008 Magnetic Black 350z NISMO /1976 Austin Mini 1098 Special (export)

Member# 1980

Damn I am stupid.. its been a while since I have done car audio stuff. So my amp is almost undoubtedly a 4 ohm stable amp and I am trying to run a 2 ohm load on it by running the subs in parallel. Basically I am overpowering the amp... ok well thanks for the input, looks like I need to do some changing around.

In a sealed enclosure, I personally would put anywhere from 200 to 300 watts to them. Don't pay much attention to the limits of the speakers. You have several ways of setting the level to them, so where no th blow them up! You will actually destroy a speaker quicker by underpowering it. I would find an amp between 400-600 watts X 1 @2ohms.

Allan
2008 Magnetic Black 350z NISMO /1976 Austin Mini 1098 Special (export)

Member# 1980

actually, the "older" fosgate amps (pre 98ish) are much more robust and caple of handling lower impedences than the newer ones. even if the power was 150 watts, you should still get quite a bit of sound out of those subs (of course, this is subjective, but it should be enough to be "heard", LOL). i wouldnt worry a ton about underpowering the subs, as low power doesnt matter, its thermal overload as a result form inadiquate cooling due to square wave signals and small boxes that leads to sub destrution. you arent sending enough power to the subs to really cause that though.

the first thing i would check is the mechanical polarity of the system. make sure your +s and -s are hooked up correctly. try running one sub off of each channel of the amp just to see if it sounds different, you never know what could happen.

another problem might lie in box placment. our cars tend to be loudest when the subs are at the very back of the trunk facing backwards or upwards (toward the glass). if you have to box sitting in the backseat facing forward or somthing that might be the problem.

of course, the box might be the problem. you mentioned it is sealed, but didnt mention the airspace it has. does it sound great on stuff like kickdrums but lacks in low bass? its possible the box is too small, resulting in an f3 point (the point at which the system begains to get quiter as the frequency decreases) higher than would normally be usefull in your system.

naturally, check all of the levels, gains, etc. to make sure you are not overlooking anything.

last but not least, make sure you didnt burn out your RCA outputs on you headunit. disconnect the RCAs at the amp and turn on the system. does the amp turn on? if it does, ignor this suggestion. if it doesnt, you have problems, an let me know. ive explaind this concept several times in my previous postes, and i dont feel like re-typing it.

hmmm...thats all i can think of right now. good luck you yo

:shhh: i do cocaine :/shhh:

Well I said screw it and bought another amp tonight. I ended up getting a Phoenix Gold QX300.1. Its already louder, I need to tune it a bit but I will let you all know how it sounds tomorrow.

>i wouldnt worry a ton about underpowering the subs, as low power
>doesnt matter

No offense, but that is not correct. Underpowering will kill a sub before overpowering it. Underpowering causes distortion which will kill a voice coil.

Allan
2008 Magnetic Black 350z NISMO /1976 Austin Mini 1098 Special (export)

Member# 1980

"No offense, but that is not correct. Underpowering will kill a sub before overpowering it. Underpowering causes distortion which will kill a voice coil."

incorrect. there are two ways to kill a sub, through mechanical and thermal failure.

sub "distortion" is caused by overpowering in which the cone travels in a non-linear fashion (due to overpowering or a large box). this will cause mechanical failure due to over exurtion of the mechanical parts of the sub, much in the way an engine might fail from revving too high.

preamp "distortion" results in a square wave signal. because the sub relies on smooth travel from the maximum points of excursion (both inwards and outwards) to cool its voice coil, a square wave can result in a "pause" of sorts at the peak of travel (almost similar to a dc signal), resulting in ineffecient cooling of the voice coil and ending up in thermal failure. this failure is not a function of power output as much as the signal being delivered. a low wattage square wave will be within the tolerences of the subs cooling capacaties, especially in a large vented box. a high powered square wave is different however. it is virtually impossible to kill a sub with low wattage, regardless of the signal being sent.

im glad you brought this up though, its a great topic of debate that has many different viewpoints behind it. i gave you points earlier because im glad you are willing to add somthing new to the mix.

i welcome any info you can find to support your opinion.

:shhh: i do cocaine :/shhh:

Heh, another question.

I hooked up my amp and all, and bridged it like I would normally. Then I got to thinking.... this is suppose to be a one channel mono amp. But yet it appears to have two channels. So I read in the manual that the speaker terminals are wired in parallel INSIDE the amp.

The amp is 150X1 @ 4ohms
300X1 @ 2 ohms
400X4 @ 2 ohms (dynamic power)

So how should I go about hooking my subs up to THIS amp? I want it down to 2 ohms but the way the terminals are "internally wired in parallel" has me confused. And what does that "dynamic Power" mean?

Thanks SPL_Eclipse, but I am still sticking to my story You are extremely helpful as well. Debate is always fun! I will give you a simple example. Alright, we already established that distortion is bad for a speaker, right? Alright, well a speaker will distort at lower levels when it has less power. If you take the same speakers and give them more power it won't distort at the same level. Now alot of other things play a role, ie. the quality of the components being used and what not. Like if you take a factory HU and blast it, it will distort at a certain volume. Now if you were to upgrade to an aftermarket HU with a higher power amp, it will get much louder and distort at a higher level. I know there are more technical terms out there but it is almost 1am and I am very tired! I do agree with pretty much everything you said and have said in the past, but I am going to have to stick to my guns this tim As far as FasterGS's latest question, I will leave that up to you, because I have no experience with Phoenix Gold (too expensive IMO). Thanks Bud and keep up the good work

Allan
2008 Magnetic Black 350z NISMO /1976 Austin Mini 1098 Special (export)

Member# 1980

Ok so I got to thinking about it and I think I have it figured out. Basically they did the wiring for me, all I have to do is run each sub to its own "channel" and with the parallel wiring inside the amp it automatically drops the impedance in half.

I typically agree about PG being too damn expensive. This amp I got for 200 bucks brand new though, the store I went to was dropping the PG line so all their stuff was on clearance. Not too bad IMO.

dynamic power is a made up term that refers to ideal conditions where the voltage remains at about 14.4 volts consistantly. the RMS term is more important (although all watage ratings on any audio equipment are a bit of a joke considering it all depends on the charging system and the music itself, but i digress).

if the amp is truely wired in paralle inside, it shouldnt make any difference how you hook up the subs, wether you connect one to each channel or wetch you bridge them with one + on one channel and one - on the other. i made a crappy picture to illustrate how they both wind up as the same circuit:




i would suggest at least trying to wire one sub per channel, however, as you never know what is going on inside the amp, and there might be unexpected results.



edit: thanks for the points jersey i agree that a nice debate is fun, but im going to come back to it tomarrow. i can agree that its too late for this LOL!!

:shhh: i do cocaine :/shhh:

Good answer! I agree with ^^^^^ It really shouldn't matter how you wire them, it should all be the same.

Allan
2008 Magnetic Black 350z NISMO /1976 Austin Mini 1098 Special (export)

Member# 1980

Just an update...

I got everything installed today and it sounds sweet! I figured out what I did, I had my decks internal x-over turned on as well as the amps internal crossover. So basically I had most of the signal crossed out

Another thing I realized is my deck has a setting for which way the subs are facing. I set that them facing 180 degrees away and that helped too. Don't know why that would matter but I am getting it all figured out.

LOL, its always somthing simple like that. soemtimes i envy people who just put good ol' plain systems in thier cars for ease of tuning.

good to hear you got everything sounding good though.

:shhh: i do cocaine :/shhh:

I totally agree! Some times less is more

Allan
2008 Magnetic Black 350z NISMO /1976 Austin Mini 1098 Special (export)

Member# 1980