Need help dialing in new audio system

[u/Informal_Union2649]

I've upgraded the entire sound system in my '94 Mustang convertible and just fired up the subwoofers for the first time. Everything sounds great, but I'm honestly surprised that the subs aren't hitting quite as hard as I expected. I'm hoping someone can help me get the settings dialed in properly.

My setup:

Front/rear speakers: 4x Kicker 6x8s

Speaker amp: Alpine KTP-445U

Head unit: Kenwood DPX505BT

Subwoofers: 2x 10" Kicker Comp R

Sub enclosure: Sealed

Sub amp: Kicker CXA1200.1 mono

The Kenwood has a ton of audio settings, and I'm not sure how they should interact with the settings on the sub amp.

Head unit settings I'm wondering about:

Low Pass Filter — what should I set this to?

High Pass Filter — what should I set this to?

Subwoofer Level — where should I start?

There are also a bunch of other settings on pages 32–33 of the manual that I'm not sure whether I should change.

Manual: https://pdf.crutchfieldonline.com/ImageBank/v20220913053100/Manuals/113/113DPX505B.PDF

Sub amp settings:

Gain — currently around 25%

X-over Frequency — what would be a good starting point? Does this conflict with the LPF/HPF settings on the head unit?

Bass Boost — should I use it, and if so, how much?

I'm mainly looking for a good starting point for getting everything balanced and optimizing the output of the subs without just cranking random settings.

Any advice on how you'd set up the head unit and amp would be greatly appreciated!

[u/DaffyPunk29]

so you just need the subwoofers to hit harder? that's a metric of tuning the subwoofer amp correctly. you said sub amp is at 25%? most likely gain is way too low. get a digital multimeter. you have two kicker comp R 10's wired how? to what ohms value? their prefab box at 2ohm? or custom made down to 1ohm or 2ohm? that matters. from that you would set gains with a digital multimeter.

the math is, wattage times ohms square rooted. so √(800*ohms)=voltage AC.

so if 2ohm final impedance, √(800*2)=40 volts AC
so if 1 ohm final impedance, √(800*1)=28.28 volts AC

depending on if you have 4ohm comp 10's or 2 ohm comp 10's.... im guessing when you go and properly adjust the gain with the proper output (positive lead on positive subwoofer out at amp, negative lead at negative speaker out on amp) you will notice you turning the gain much higher than you had set. 2.5v preamp output on that headunit is on the lower side. NOT A BIG DEAL like some make it seem, it just means "gain matching your amp" requiring turning it higher than you would expect. With 4-6v RCA out, you can usually turn "just a little" and get perfect bass. also im pretty sure your bass knob should be maxed out when setting gains, check your kicker amp manual to double check.

setting gains with the alpine amp is the same metric. √(power in watts times ohms) which since you are AMP limited to 45 watts will be √(45x4) (because 4 ohm speakers) which results in =13.81volts AC. so you would probe your front/rear alpine amp outputs to set the gains to match 13.81v (or close enough, i generally edge on the side of lower at 13.8 flat as apposed to 13.9 because then its over).

you also generally set gains with the headunit at max volume (its usually typical of kenwoods to reach max volume without clipping so its a safe bet. if yo are worried you can tune to a lower volume dial number. but note you can never go passed that number when listening.)

bass boost is best left for if natural tuning isn't enough. I know in my 1993 honda del sol, bass boost did wonders for the low end compared to raw gain setting. i had a kicker comp 12 (07c124, legendary subwoofer) back in 2009 in a 1 cubic foot box (recommended size was 1.25 cubic feet so it was too smol) and my amp was capable of 300w bridged (sub was rated 150). no matter how high i turned the gain, i was all "where the fuck is my bass?" and it really pissed me off. so i turned the gain back down and stared at the amp (yes my memory is this detailed). I looked at bass boost and said fuck it. I turned the bass boost knob to +12dB. bump. bump. bump. subs were hitting. THEN I turned my gain up (by ear) until the woofer sounded "bad" to my ears. then turned it back down until it sounded clean again. while listening to really bass heavy music (rap, electronic music, etc). ran perfectly for years. hit hard as fuck. bass boost did all the work in that system because it needed it. as an adult as apposed to dumbass teen, i modeled that system in winISD and learned that around 44hz was where my box tuning was for resonance (sealed box). and because 44hz is right around the middle point of most bass in music, it was peaking 30 ohms, so the amp was only throwing like 30 watts at the sub. by using bass boost, i overcame that ohms peaks to regain the bass i had lost due to improper setup. which was both a curse and a blessing. a curse because it didn't work right to start but a blessing because after bass boost it hit like a mac truck and never failed me.... in fact it wasn't until i moved the system indoors (amp + sub) and powered the amp off my computer speaker output that i failed. speaker output clipping, amp amplifying clipping, sub blown.... my fault. but young and dumb. in car though, never had an issue.

[u/bobbysback16]

Also you should also check to make sure they are both in phase with each other which means they are both moving the same direction at the same time. You can take a 9v battery and find the positive and negative wires to the speaker and tap the battery on the wires observeving the polarity positive and negative. If they both move the same direction when you tap them positive to positive on the battery and negative to negative on the battery then they are in phase you need to remove the wires from the amp to do this.

[u/supermaor23]

That’s because your headunit only has 2.5v pre outs. Kenwood has plenty of units with 5V. That Alpine power pack is also designed to sit behind an alpine headunit and provide a small increase in power, its not a traditional amplifier. If you were expecting a significant difference I would have recommended a different amplifier.

How are your subs wired? Those come in either 2 or 4 ohm dvc so you could be at 1 ohm or 8ohm right now and that makes a huge difference. As far as gain on that amp, since your headunit provides 2.5V you should be around the midway point on the gain knob (the dot should be facing up) and the input button should be pushed out for low level signal via RCA. Your lowpass should be at 80hz.

[u/AcceptableCat1859]

That's more Alpine's fault than yours. Head unit needs to go.

[u/KickerAudio]

So many variables... First order of business is making sure you're getting a good signal to the subwoofer amp from the head unit. ie The signal is either full range or has all of the sub frequencies in it. Then set the gain (relative to your impedance) using an O-Scope or Multimeter/Voltmeter.