Do I need more amp or a higher preout voltage?

[grampi 10+ year member]

I don't get it. My HU is an Alpine 9887 with 4V preouts. My amp is a Kicker KX 600.4. I'm running it in 3 channel mode with 75wrms going to my comps and a bridged 300wrms going to my sub, an ED e12k in a 1.25 c.f. sealed enclosure. I have amp #1 (which is the amp for the comps) gain set right at half and they get more than plenty of signal. However, I have to have amp #2 gain all the way up AND the amp's bass boost all the way up to even get a decent amount of sub output (and I'm not basshead by any means, I just like to feel my bass as well as hear it). What's wrong with this picture? I'm running doulbe the power on my sub as I'm running on my comps, and yet the sub output is the one I have to crank the gains on. Makes no sense. The sub sounds clean even with everything cranked up (no distortion at all) so it doesn't seem like the amp is running out of power. It acts more like it isn't getting enough of an input signal from the HU. I would think if I was overdriving the amp I would hear indications of clipping. I suppose I could try a line driver on the preouts to the sub, but a lot people have said to stay away from line drivers. That would however be a lot less expensive than the alternative which would be to bridge my entire amp for 600wrms, but then I'd have to buy a sub that could handle that much power, and I'd have to buy another amp to drive my comps. What to do?

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[helotaxi 5,000+ posts]

The sub is inefficient. Mids and highs are very efficient. Gain setting as a percentage doesn't really mean anything.

Make sure that the coils are wired right on the sub. Make sure that the sub volume is all the way up on the HU. Make sure that you don't have your low pass set too low or SSF set too high.

 

[Audio Master 10+ year member]

i have a similar problem with my setup my sound is crystal clear but the HU runs out of guts i can turn it up to 35 and its still crystal clear but the comps and the subs just dont sound like they are getting enough and also sound like they are screaming for more signal i know they go loauder as my freinds got the same setup with a pioneer HU and different amps but same subs and comps hes got one less sub than me and gets quite a bit louder i figured it was the HU but upon changeing it from a 9885 to a 9850 it was still the same so i installed caps with a voltage metre and found the problem my voltage at high volumes was dropping below 12V getting at times as low as 11.1v so thats the issue the voltage drops and being AB amps the signal drops same goes for the monblock just not as bad so i wired in another battery in parralel still no joy so now im uping the anti im going to wire the batts in series and upgrade the wireing to larger wire 0gauge where nessesary and 4gauge everywhere else and the biggest **** speaker wire i can use also i will be putting in high end rca connects used for BIG DOLLER home theatres and then with my rewound alt and my extra alt on braket all wired in im told by my installer that my system will be bullit proof and even with the AC on it wont drop below 12-13v so maybe thats your issue the voltage drop or the size of the wire if you dont have enough power and enogh size to run and charge the power the amps compesate by makeing it produce less signal thus less sound or so im told ill try it and see whats wat but the other thing to do would be check on http://www.12volt.com as its great source for trouble shooting

 

[grampi 10+ year member]

The sub is inefficient. Mids and highs are very efficient. Gain setting as a percentage doesn't really mean anything.
Make sure that the coils are wired right on the sub. Make sure that the sub volume is all the way up on the HU. Make sure that you don't have your low pass set too low or SSF set too high.

I have the amp gain and bass boost turned all the way up so I can have a little bit of adjustment at the HU for different sources. All sound sources have a different level of bass content. Even then I have to have the sub level adjustment on the HU between 10 and 15 almost all the time. The sub coils are wired correctly and I just checked the impedence using a DMM and it reads 3.9 ohms. The low pass is set at 80hz @ 18db per octave, and I don't know what SSF is.

 

[grampi 10+ year member]

Audio Master

I will check out that site. I'm running 4 ga power wire from the battery which should be plenty sufficient for a total system power of only 450 watts. Maybe I am experiencing low voltage.

 

[audioholic 5,000+ posts]

Telling us you have the gain and bass boost turned 'all the way up' just tells us you dont understand how to set them properly. Unless your h/u's maximum signal voltage is like .5 volts, you have your gain set way too high and are just asking for clipping your amplifier when you turn it up.

As for volume output differences, the lower the frequency being reproduced, the more air that needs to be displaced in order to maintain a constant volume level. Therefore to compare output volumes of two different system playing vastly different frequency bands, and only relying on input power as a differentiation, will likely lead to false conclusions.

You have a relatively low powered, single sub, in a sealed box. You decribe your bass needs as pretty minimal, but without us hearing it we cannot agree its too little or too much given the situation. Is it buried in a trunk for example? Maybe your comp amp is set artificially high too, and compensating it down to normal would alleviate the issue with the sub output. *shrug* In any event, you are right to be trying to blend the front stage and substage together. But, you are very wrong in trying to do so by turning your subwoofer up to meet the fronts. Always always set amplifier gains to their proper level (maximum setting just before starting to clip, see amp setting tutorial), then adjust the loudest ones DOWN to meet up the lowest output speakers in your system. This level matches the system, while keeping everything out of clipping.

 

[DBfan187 5,000+ posts]

What volume level did you set the gain @? I'm betting you set it very low! Try setting it like @ 33.

 

[azbass 5,000+ posts]

need more cowbell

 

[grampi 10+ year member]

Telling us you have the gain and bass boost turned 'all the way up' just tells us you dont understand how to set them properly. Unless your h/u's maximum signal voltage is like .5 volts, you have your gain set way too high and are just asking for clipping your amplifier when you turn it up.
As for volume output differences, the lower the frequency being reproduced, the more air that needs to be displaced in order to maintain a constant volume level. Therefore to compare output volumes of two different system playing vastly different frequency bands, and only relying on input power as a differentiation, will likely lead to false conclusions.

You have a relatively low powered, single sub, in a sealed box. You decribe your bass needs as pretty minimal, but without us hearing it we cannot agree its too little or too much given the situation. Is it buried in a trunk for example? Maybe your comp amp is set artificially high too, and compensating it down to normal would alleviate the issue with the sub output. *shrug* In any event, you are right to be trying to blend the front stage and substage together. But, you are very wrong in trying to do so by turning your subwoofer up to meet the fronts. Always always set amplifier gains to their proper level (maximum setting just before starting to clip, see amp setting tutorial), then adjust the loudest ones DOWN to meet up the lowest output speakers in your system. This level matches the system, while keeping everything out of clipping.

Like I said, the sound of the sub is completely undistorted - not an indication you'd get if the amp was clipping. If the amp was clipping, you'd definitely hear distortion. I could set the gains where they're "supposed" to be, but I already know what the result will be; too low of an output. If I were to set the sub gain where it's supposed to be, then bring the comp amp's gain down to where they balanced out, I would hit the upper volume limit of my HU and end up with hardly any sound from the system at all. Also, I do have my sub in the trunk which is where I've always had my subs.

 

[tcguy85 10+ year member]

see the post i just left you on DIYMA.

it sounds to me like you are not getting enough power through the rca's to the amp. i had the same problem when i had an older alpine head unit. a line driver fixed the problem. see my post over there though for more info, i'm to lazy to type it again. lol

 

[GMCJimmyslt2000 10+ year member]

by the way u cant hear clippin. ur gonna either fry ur amp or blow ur sub. If u want more output port it, or get a better amp, or get a new sub.

 

[tcguy85 10+ year member]

^ or it could be that his amp isn't getting enough power through the rca's. i had the same problem when i had my alpine HU years back. a line driver fixed it for me.

 

[helotaxi 5,000+ posts]

see the post i just left you on DIYMA.
it sounds to me like you are not getting enough power through the rca's to the amp. i had the same problem when i had an older alpine head unit. a line driver fixed the problem. see my post over there though for more info, i'm to lazy to type it again. lol

If he's getting enough signal from the front channel preouts he should be getting more than enough from the sub out. If the HU signal was the problem, turning the gain ot max should still get full power from the amp. Most need only around 250mV to make full power.

There are three possibilities, either something is actually broken, you are expecting too much from the sub or you have it set up wrong. I'm voting one or both of the latter two. In any case a line driver isn't the answer.

 

[tcguy85 10+ year member]

In any case a line driver isn't the answer.

he could possibly have a different problem or is simply expecting to much from the sub. but i was just stating that i had the same problem and the line driver fixed it for me.

on my post on DIYMA i told him a very easy way to figure out if the amp was seeing enough to put out full power. so hopefully he will try it.

 

[DBfan187 5,000+ posts]

I still think he set his gains using a low volume setting.