2 hook-up questions:

[slow6]

What is PRE-out?
Is that the same thing as Low output?
Its on the back of my head unit / stereo.
I was trying to hook up my amp to it.
But the system barely does anything.


Is it okay to run an amp bridged at 4 ohms and your sub can only run at 8 ohms?

thanks

[Tom Rs]

Re: 2 hook-up questions:

a pre-out is just an outlet to plug your rca cables to

[slow6]

Re: 2 hook-up questions:

so its probably the 4ohm amp mixed with 8ohm sub is the reason its not loud AT ALL? thanks

[99FirebirdSPL]

Re: 2 hook-up questions:

sounds like it. I had this problem a while ago when I had a rockford fosgate xlc 15 that was 8ohms running off of a 100 watt alpine amp. all you can do is turn the gain (on your amp)up as far as you can.
The gain is supposed to match up to your head units preamp voltage.

[95Batmobile]

Re: 2 hook-up questions:

The 4 ohm and 8 ohm thing doesn't matter.

Have you turned up the gain on the amp? That would be what controls how loud it gets. Just don't turn it all the way up to where it will clip.

[StrtRacer98]

Re: 2 hook-up questions:

also check the bass settings in the headunit itself... that can be a big factor.

if its a "sub out" it will have sub control built into the functions and may be turned all the way down.

[96firebird311]

Re: 2 hook-up questions:

The 4 ohm and 8 ohm thing doesn't matter.

Have you turned up the gain on the amp? That would be what controls how loud it gets. Just don't turn it all the way up to where it will clip.

I certainly wouldn't say it doesn't matter. Infact that's probably at least half his problem.

And secondly, the gain is not entirely what controls "how loud it gets"....To which you will surely respond "I know that. I know the gain isn't a volume knob!"....But yet, that's almost word for word what you posted. You are prescribing him the oh-so-common recipe for disaster. Using the gain knob to make up for an under-powering amp.

Also insure that your crossovers are set properly. You may have it set to high pass 100Hz or similar. (And your headunit's low pass set to 100Hz on top of that LOL) Hell.... with you being unsure of what pre-out you have where..... you could have the headunit's built in high-pass set, and RCAs plugged into the front output. Could be a number of things really....

[slow6]

Re: 2 hook-up questions:

yea the amp is set on LPF only

96firebird311.. you bring up a good point!
That PRE-OUT could be a HIGH pass out!
Its the ONLY RCA on the old head unit.

Maybe I should use one of those convertor / adaptors that have speaker wire In and rca low-pass out? like $20
I have one, I'll take a picture if you need me to.

[Earnhardt132000]

Re: 2 hook-up questions:

Do you have a manual for the head unit? It will explain what type of signal is being outputted through the pre-out. Mess around with your head unit.

[usmcyoung]

Re: 2 hook-up questions:

a big problem ur having is ur amp is 4 ohms and ur sub is 8. First of all if ur using a sub thats running 8 ohms of resistance then uvegot a very low grade sub that cant handle very much power in the first place, a general rule of thumb is the lower resistance a sub is intended to provide the harder you can run it/ more power you can SAFELY run through it. your second problem is the differance in resistance between the two peices of equipment, it is absolutely crucial that your amp annd sub are running at the same level here. what happens is ur amp has a surge in power (for a strong bass hit), and when it amplifies the signal and sends it to your sub it shorts out (if your sub is running at lower resistance than your amp), or in your case the sub destroys the signal by sending it through a larger res. set up than the amp sent it through in the first place. Too many people tell others that may not know as much about electricity and audio equipment to just turn up the amplefier or the gain, when in fact the biggest problem is the set up will never allow for true quality sound just because these two peices of equipment were never intended to be used together in the first place! my suggestion to you would be either get rid of your sub or amp. since your amp seems like a fairly common unit. two channel bridgable 4ohm stable. i would suggest you get rid of your sub and find a more common sub that will fit your amp. either a sub with dual two ohm voice coil, Which is what i would personaly go with. or a four ohm single voice coil. however you also have to make sure that at its max potential your amp wont blow your sub. in other words match numbers if its a 1000 watt amp find a 1000 watt sub. and as far as ur preouts they are moste likely for bass and even if they arent the cross over in your amplefier will take care of that for you all you have to do is set it accordingly. higher frequencies are for higher speakers lower frequencies are for lower speakers. if set properly the x-over will filter out the higher frequencies so that they do not destroy your subwoofer. but thats another topic for another time! oorah!!!

[95Batmobile]

Re: 2 hook-up questions:

I certainly wouldn't say it doesn't matter. Infact that's probably at least half his problem.

And secondly, the gain is not entirely what controls "how loud it gets"....To which you will surely respond "I know that. I know the gain isn't a volume knob!"....But yet, that's almost word for word what you posted. You are prescribing him the oh-so-common recipe for disaster. Using the gain knob to make up for an under-powering amp.

Also insure that your crossovers are set properly. You may have it set to high pass 100Hz or similar. (And your headunit's low pass set to 100Hz on top of that LOL) Hell.... with you being unsure of what pre-out you have where..... you could have the headunit's built in high-pass set, and RCAs plugged into the front output. Could be a number of things really....

LOL it really doesn't matter. I need to find the article about it, but basically in order to lower the impedence of a driver you also lower the sensitivity. The lower impedence driver pulls more power from the amp, but takes more power to produce sound. Higher impedence drivers also have higher sensitivities so they requre less power to get to the same sound levels.

About the amp gains... I gave no recipe for disaster. As long as he doesn't drive the amp into clipping he'll be fine. If he wants the correct way to do it and has the equipment JL Audio has a great link that shows the right way to do it :
http://mobile.jlaudio.com/support_pages.php?page_id=143

[96firebird311]

Re: 2 hook-up questions:

LOL it really doesn't matter. I need to find the article about it, but basically in order to lower the impedence of a driver you also lower the sensitivity. The lower impedence driver pulls more power from the amp, but takes more power to produce sound. Higher impedence drivers also have higher sensitivities so they requre less power to get to the same sound levels.

About the amp gains... I gave no recipe for disaster. As long as he doesn't drive the amp into clipping he'll be fine. If he wants the correct way to do it and has the equipment JL Audio has a great link that shows the right way to do it :
http://mobile.jlaudio.com/support_pages.php?page_id=143

LOL. So who cares what impedance the subs are and what an amp is stable to.... they all will have the same output huh? 2 ohms. 4 ohms. It doesn't matter. The sub will sound the same in the end huh? :naughty: Whether your claim that as impedance decreases, so does sensitivity, I have never heard such a thing. First if this holds true, I doubt it's proportional. And second, why does every major manufacture release their thiele-small parameters with matching sensitivity ratings for both 2 and 4 ohm versions of the same sub? And why even worry about wiring your two 4 ohm subs in parallel to the amp.... 2 ohms, 8 ohms... it'll all sound the same in the end huh? Come on man.

Next, you told some random person with little knowledge of car audio:
"Have you turned up the gain on the amp? That would be what controls how loud it gets."
As if he knows what clipping is or how he should even start properly setting his gain. You re-phrased the sentence "The gain is a volume knob." to someone with little/no experience.

[95Batmobile]

Re: 2 hook-up questions:

LOL. So who cares what impedance the subs are and what an amp is stable to.... they all will have the same output huh? 2 ohms. 4 ohms. It doesn't matter. The sub will sound the same in the end huh? :naughty: Whether your claim that as impedance decreases, so does sensitivity, I have never heard such a thing. First if this holds true, I doubt it's proportional. And second, why does every major manufacture release their thiele-small parameters with matching sensitivity ratings for both 2 and 4 ohm versions of the same sub? And why even worry about wiring your two 4 ohm subs in parallel to the amp.... 2 ohms, 8 ohms... it'll all sound the same in the end huh? Come on man.

Sigh.. I looked for the article and couldn't find it. It is really an interesting read. All other things equal on a driver, if you change the impedence it will change sensitivity, I believe proportionately too (been a while since I read it). Also, you're assuming the T/S paremeters companies believe are true. If they were all true we'd all be using audiobahn subs ;)

Next, you told some random person with little knowledge of car audio:
"Have you turned up the gain on the amp? That would be what controls how loud it gets."
As if he knows what clipping is or how he should even start properly setting his gain. You re-phrased the sentence "The gain is a volume knob." to someone with little/no experience.

Yeah, true. I could have worded it differently. I was hoping when I said "Just don't turn it all the way up to where it will clip" it would give the impression not to turn the gain all the way up :P

[slow6]

Re: 2 hook-up questions:

stupid question: what if I hook up a 10" 4ohm sub with the 12" 8ohm sub on a 4ohm bridged sub? Will that create a 4ohm load? no benefit?
I should probably just hook up the 10" and sell the 12"
thanks, please continue your debate

[95Batmobile]

Re: 2 hook-up questions:

I've always been told not to use speakers with different impedences together. I've never actually tried it though. Either way, using a 4 ohm and 8 ohm sub together won't give the ohm load you want on your amp.
What is the name/model of the 12" sub you have? And what is the name/model of the 10" sub you have?