Installing a 3rd party amplifier on TJ with factory amp and sub

[AdelaideTJ]

I did not know the screens were removable... I went with a 7" screen Alpine.

They are bolted on, not removable per se. Just for first time installation and adjustments, but it's usually held in place by screws

 

[bobcat]

I used to look at it that way, but I moved on to my current reasoning about ten years ago.

IMO, it's all good for the amp's power capability to be higher than a sub can handle...because that means it's an easy life for the amp when you dial back the gain on the amp to match the power requirement of the sub. I specifically try to run a higher-power amp than the subs are rated for, and you can find folks with more experience than me who encourage us not to run an amp at more than 75% of an its power capability (for the longevity of the amp).

You don't have to follow this logic, but it's certainly safe (and arguably safer). I've run Sundown 12"s and 10"s this way long before doing so on this build. It's nice knowing the amp isn't being overworked, and I dial in the power that the subs see so they are happy. Also, working the amp less means less heat and more efficiency.

Side note: I also run a 160-amp Durango alternator (Amazon for $120) to ensure there's sufficient power for all systems, and I run 4awg power/ground wire to limit voltage drop.

It makes sense if you dial back the gain on the amp. The amp I am using does not have a gain knob, but it has an input sensitivity knob (from 0.2V to 5V). I was reading online and my takeaway is that the sensitivity is somehow related to the gain. I have set it to 2.5V which is the pre-out level of the HU.

I was tinkering with the crossover settings of the HU and setting to 2 way crossover is giving the best sound quality.

 

[MikeE024]

It makes sense if you dial back the gain on the amp. The amp I am using does not have a gain knob, but it has an input sensitivity knob (from 0.2V to 5V). I was reading online and my takeaway is that the sensitivity is somehow related to the gain. I have set it to 2.5V which is the pre-out level of the HU.

I believe your sensitivity knob is doing the same thing my gain knob is doing. It's generally used to match the output of the amp/sub so it's not underpowered or overpowered at the volume level you play your deck. Relevant link.

Many (if not most) systems don't have perfectly matching specs between the subwoofer, amp, and deck so adjusting the gain/sensitivity gets you to where you want to be. Notice that the preamp output varies from deck to deck which affects where you would set your sensitivity knob on your amp. Put your volume at the 80% or so mark of the highest you will listen to your music at and then bump up the sensitivity on your subwoofer amp starting from super low to a point that achieves good clean sound (loud enough for your liking without distortion). Done.

I'm no expert on this, so I can't discuss the theoretical side. I know how to achieve what I want in a practical setting similar to how I'm able to turn an adjuster knob out when a shock is too stiff.

You have the unfortunate choice of either wiring the current sub to 4ohm or 1ohm. You expressed that you aren't happy being wired at 4ohm, and that does not surprise me because you would need a stronger amp than what you have in order to make it thump.

My little subwoofer thumps way more than I thought it could and I'd yank it right out if it sounded anemic. I don't have distortion because I turned my gain/sensitivity down so that the output matches the deck's volume output.

For reference:
My amp's max RMS is 350 watts at 2ohm.
Amp

My 4-ohm DVC subwoofer's max RMS is 150 watts at 2ohm.
Sub

I've adjusted the gain/sensitivity accordingly. I won't say anything more about it you know where I stand.

I was tinkering with the crossover settings of the HU and setting to 2 way crossover is giving the best sound quality.

Sounds awesome glad things are coming along!

 

[bobcat]

To close on this: I was able to get a good amount of 'thump' by turning the input sensitivity of the amp to a low value (set to 0.7V for the knob which goes from 0.2V to 5V)
Also set the cross over settings on the HU to two way. I am happy with the setup and will likely stick to it for sometime before the itch to upgrade to a 5- channel amp and bigger subwoofer surfaces.

Thank you all for the inputs!

 

[Akitadog]

These photos will also help explain what Jodh is talking about.
View attachment 401404

View attachment 401405
I might have a PDF with measurements at work... no find...

Ah ha! Found the drawing, made a pdf. Good for the column bolt spacing for a DIY.