[Billfitz]

I already told you what I think the problem is. Without knowing what sub you're using, including the driver Thiele/Small specs and the enclosure dimensions, I can't say any more.

[Redzsi]

Jbl 5501 amp with kicker L7s 12" subwoofer enclosure. 4 gauge cables, with LOC (I don't know exactly the name) and technic pnp harness. I know and thank you for the response!

[Billfitz]

That driver should have no problem playing louder than the rest of your system, assuming the enclosure isn't too small. The amp isn't all that powerful, but I'd think it would be adequate. You may have no alternative but to go to an expert shop with the right diagnostic tools to find out what the problem is.

[Redzsi]

Originally Posted by Billfitz

That driver should have no problem playing louder than the rest of your system, assuming the enclosure isn't too small. The amp isn't all that powerful, but I'd think it would be adequate. You may have no alternative but to go to an expert shop with the right diagnostic tools to find out what the problem is.

I was at the dealership and they didn't find anything. Yes I think that's gonna be the next step. If I will know the problem, I will let you know.

[Encanto]

Originally Posted by Redzsi

I mean if I turn up the volume. The low range (sub) stays on 60-70% and the mid and high range getting louder. If I turn the volume to max I'm not hearing the bass at all. Just only mid and high. My amp is set to 60hz. It's really weird.

If you connected the HK OEM amp woofer outputs directly to the high level inputs of the sub amp, and the inputs were not 40V max, then it could be possible that the input section of that amp was damaged.

Try another amp with either the correct LOC or an Audiocontrol amp.

[Billfitz]

Originally Posted by Redzsi

I was at the dealership and they didn't find anything.

I very much doubt that you'd find an audio expert at a dealership.

[James2019]

Maybe you can try to upgrade your car stereo system

[Johnny Chuttz]

You are barely giving that L7 a tickle with 500w. Especially if you have a ported enclosure.

Look at the chart on Kicker's site:

https://www.kicker.com/12-l7-subwoofer

With your gain cranked that high you are reaching peak output of the amp @ 60-70% volume.



You'll need a bigger amp to get any more output. Ideally 1000-1200w.

[Billfitz]

Originally Posted by Johnny Chuttz

You are barely giving that L7 a tickle with 500w.

Possibly, but the only way to be sure of what's happening is to measure the amp output to see if it's the problem. A good technician would have the tools and knowledge required to measure the output of his amp at the point where increasing the input level no longer has any effect.
Even if he doubled the power input to the sub that would only give a 3dB increase in output. Anything less than 6dB isn't worthwhile.

[Redzsi]

UPDATE: I found a guy who has a new 7 series with same harman kardon system like mine (option 688). He has the same problem. So I think it's a common problem. I tried it with a lot of amps, like rockford Fosgate 1200.1, Kenwood 9106D, Soundstream AR1.8000D. And I tried a lot of subs aswell, kicker compr single, after a dual, kicker L7, Jbl cx1200 single, right now it's a Sony 12" 500w RMS with a jbl 5501. If I put in a stronger amp with stronger sub, it's just stronger on the low and mid ranges of the volume. If I turn the volume in the high ranges, like 70-80% EVERY single amp, sub staying in the mid range like 50-60% of volume. I know I write the problem down a couple times, but I just want to let you know this problem is not with the aftermarket amps or subs. The oem HK sound system doing this. I just found a guy who can make a "little box" what is solve this issue. I give a try for this and soon as I can I'll let you know the results.

[Encanto]

If you are using an LC2i as your line driver/active LOC then you will have two gain controls, one at the LC2i and one at the aftermarket amp. If the OEM amp woofer outputs flatten at a certain OEM volume (that would be about 47 clicks of volume rotation) then any of the two gains could increase the sub-volume level over what you are hearing, up to the max level of that gain. In the case of the LC2i gain, that max gain can go up to 13.5V. In the case of the JBL 5501, max sensitivity of a low signal input is just 200mV, high level is 20V. Specs are in the LC2i and amp user manuals -all should match for proper installation.

Play a 30Hz tone from 0 clicks to full OEM volume (42-47 clicks or so) with both gains at minimum. Only your sub and woofers (you can unplug the woofers to only hear the sub) should be playing at that tone. Then increase LC2i gain until you hear clipping. Sub should be louder than before. Reduce gain until there is no clipping. That is the gain level to use. If that gain loudness is still not what you expect at that OEM volume then you need a much bigger amp and a much bigger sub -and perhaps a second battery with caps.

Polarity of the sub is also important.

Originally Posted by Redzsi

UPDATE: I found a guy who has a new 7 series with same harman kardon system like mine (option 688). He has the same problem. So I think it's a common problem. I tried it with a lot of amps, like rockford Fosgate 1200.1, Kenwood 9106D, Soundstream AR1.8000D. And I tried a lot of subs aswell, kicker compr single, after a dual, kicker L7, Jbl cx1200 single, right now it's a Sony 12" 500w RMS with a jbl 5501. If I put in a stronger amp with stronger sub, it's just stronger on the low and mid ranges of the volume. If I turn the volume in the high ranges, like 70-80% EVERY single amp, sub staying in the mid range like 50-60% of volume. I know I write the problem down a couple times, but I just want to let you know this problem is not with the aftermarket amps or subs. The oem HK sound system doing this. I just found a guy who can make a "little box" what is solve this issue. I give a try for this and soon as I can I'll let you know the results.

[notjakl]

Kinda old post, but I don't think you've found your answer yet.

What you are talking about is called bass roll-off. Basically, factory radios will stop letting low frequency levels (bass) increase at higher volumes. The rest of the frequencies will keep increasing. This is to preserve your factory speakers, so they don't damage themselves trying to produce the low notes.

You have an LC2i. This has a feature called accubass. Look it up, and fix your problem.