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Hey guys, Im new to this forum but I joined in hopes that someone could help me out with my system before I take it to a shop and spend more money. I am driving a 2021 VW Jetta GLI S (no beats audio) and I decided since the factory speakers sound so good but have little sub bass that I wanted to install a sub into the car. Long story short the setup I have rn is good but the bass is lacking still. Almost sounds like I have a 6” sub instead of a high-power 10”.

Lets start from the battery and work our way back to the subwoofer so you have a clear idea of my system setup. I used a Shosche 1500W amp wiring kit from Walmart (which I assume is slightly higher than 4 gauge wire but is not OFC) to connect my factory battery to a 1-to-2 fuse block.
There is a fuse between my battery and the fuse block that came with the kit. From that fuse block I have wiring going to my Rockville Audio RXA-F1 (4 chan amp that produces 65x4 @ 4ohm and 95x4 @2ohm) which powers my front 2x door speakers which are wired to my factory tweeter location which I swapped with Skar TXT-1 tweeters (yes they are cheap but they work well for the price). The other exit of the “power fuse” block goes to my mono amp. I started with the Rockville RVA-M2 (rated for 440W RMS @2ohm). The mono amp powers my sub in a custom sealed box that used to house my now blown JL Audio 300W RMS sub (forgot the name) but now has a Skar VD10 D4 10” sub (rated for 500W RMS continuous). I had the problem with that amp still not giving enough unclipped power to my sub so I decided to take a leap of faith and purchase Rockville’s more more powerful and brand new Krypton-M3 (rated for 700W RMS @2ohm). I have a ground cable going from both amps to a 2-to-1 fuseblock and my ground is screwed underneath my carpet on the frame of the car with as much paint sanded off as I could.

However changing from the RVA to the Kyrpton somehow made my sub produce less sound. Its sounds better and definitely has a more balanced frequency range but it is not loud. My factory midbass speakers have more umph than my sub rn. Sound is sent via a 4 chan passive line-out converter that sends a 2 chan signal to my RXA-F1 amp which then sends signal to my Krypton-M3 (RCA from LOC to 4 chan amp and then RCA from 4 chan amp to mono amp).

On my factory radio I have the EQ set to +7 for highs +5 for mids and +9 for bass (range is -9 to +9) and when using bluetooth I have the volume strength set to minimum (other options are medium or maximum). On my phone I use Apple Music to stream HQ 192kps audio and the EQ in my settings is set to Hip-Hop since I listen to it more than anything else. So basically everything I have is set to as much bass as possible.

I used an oscilloscope to set the gains on all my amps and according to my oscilloscope my factory head-unit does not clip at max volume level so I set my gains at 90% volume. The 4 chan amp gain is set appx at 50-60% and the same is for the mono amp, anything higher starts to clip. On my 4 chan amp I am running in 2 chan mode with HPF set to around 1000hz since my factory mid-bass cant handle the bass with extra power above half volume. My mono amp has its “HPF” set to the minimum 15hz, bass EQ is set to +3db, and “PASS” is set around 100hz.

My sub is wired to 2ohm in a sealed enclosure (specifications are not known but I can find out if needed) and should definitely be getting more sound. When I first started my setup and only had the 4 chan amp, I bridged two channels on the amp to the sub which @4ohm gives 200W RMS but since it had a 2ohm load it overheated shortly after one song with intense bass. I have yet to hear my sub sound as loud and clear as when I had my system setup like that. Only reason I got the mono amp was to prevent my 4 chan from overheating while still giving the sub the power it wants.

I have yet to figure out a solution for my problem but I have a couple ideas that Im hesitant to give a shot at since it means, you guessed it, more work and taking the car apart again.

My first idea is to ditch the cheap passive line-out converter for a nice and shiny Audiocontrol LC2i. I assume itll be able to send a cleaner stronger voltage signal to my amps and the “Accubass” feature appears to be what I need to bring back the sub bass. However Im not sure if this will solve my problem or complicate it.

My second idea is to get a 5-10 Farad capacitor bank to ensure that my amps are recieving plenty of juice to power my speakers, however doing the math in my head I doubt it’s necessary unless I decide to get a larger sub or more subs.

Sorry about the long first post but I figured it would be better to go into as much detail to ensure there are no questions. Let me know what you think and if you have anymore questions please ask away.

Thank you
 

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A few things to try without spending any more cash.

1. Set gain by ear. Setting gain with a scope and sine waves works great for listening to sine wave but not for music. You're probably missing output here alone.

2. Move the box around. Location of the sub relative to any cabin modes can drastically effect output at the listening position.

3. Set all eq flat. You're fuxking up the response massively

4. Set mid bass hpf to around 80-100 hz. Sub lpf set to 80 hz and disable boost.

5. Bypass the loc and hu, use a headphone 3.5 mm to RCA as input. Your tie in to the factory system is **** based your description... You will need to reset gains probably but that's better than using a ****ting input signal.


The idea you presented are complete garbage. Fix your install.
 

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I agree with Lithium, time for a reset. Set everything to flat and turn the gain on the sub all the way CCW. Then get the rest of the system sounding how you want it before increasing the gain on your subwoofer amp. Turn the gain up until you start to hear distortion ( by this time the sub should be way to loud ). Then back it down until it blends with the rest of the speakers.
 
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Discussion Starter · #5 ·
A few things to try without spending any more cash.

1. Set gain by ear. Setting gain with a scope and sine waves works great for listening to sine wave but not for music. You're probably missing output here alone.

2. Move the box around. Location of the sub relative to any cabin modes can drastically effect output at the listening position.

3. Set all eq flat. You're fuxking up the response massively

4. Set mid bass hpf to around 80-100 hz. Sub lpf set to 80 hz and disable boost.

5. Bypass the loc and hu, use a headphone 3.5 mm to RCA as input. Your tie in to the factory system is **** based your description... You will need to reset gains probably but that's better than using a ****ting input signal.


The idea you presented are complete garbage. Fix your install.
How would I by pass the HU and LOC and use a 3.5mm jack instead? My HU doesnt have any inputs except USB type c and bluetooth
 

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Discussion Starter · #8 ·
Phone or laptop headphone jack to rca cable. Plug it into your phone and the 4 channel amp. Use the output from the amp or some RCA y splitters to send signal to the subwoofer amp.
Ahhh I see what ur saying now. Ditch the HU and LOC and go straight from the source, my phone. I have an iPhone 12 so I only have the lightning port. After some quick research I found a lightning to RCA on Amazon. Going to give that a shot. From what I read online the lightning port can provide up to 5V so should be plenty for the amps. Im also going to try reseting my gains and see if It makes a difference while I wait for the package to arrive. Thank you for your help, Ill update this thread after I do all of that.
 

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Hang on a minute. You had intense bass with the 4ch amp??? Then after adding a mono amp your bass was lower. Then after adding a bigger mono amp the sound is even lower? This sound more like an issue with settings or wiring to the mono amps. Or possibly the output rcas on the 4ch just plain suck. Make sure the 4ch doesn't have a xover setting or some other settings for the output rcas that might be set wrong.

Also try temporarily moving the rcas that feed the 4ch over to the mono amp and see if that fixes the bass issue.
 
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Discussion Starter · #10 ·
Hang on a minute. You had intense bass with the 4ch amp??? Then after adding a mono amp your bass was lower. Then after adding a bigger mono amp the sound is even lower? This sound more like an issue with settings or wiring to the mono amps. Or possibly the output rcas on the 4ch just plain suck. Make sure the 4ch doesn't have a xover setting or some other settings for the output rcas that might be set wrong.

Also try temporarily moving the rcas that feed the 4ch over to the mono amp and see if that fixes the bass issue.
Yeah it doesnt make sense. I know the rca cables I havent arnet garbage but Ill try that and see if it brings back the bass. Then I know its the 4chan fault.
 

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Something else is wrong.

You have enough power. Check VC wiring.

Also, it's poor practice to just go +++++ on every setting. Set the head unit to flat. Set the amp to flat. Start from there. You don't need boosts everywhere.
 

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As long as your dealing with the factory radio, whether its bluetooth or whatever, as long as your running it through the VW deck its controlling the frequencies. Aka rolling off the lows to protect the factory speakers. That's your issue. You can raise the bass all u want it's still going to do Volkswagen voodoo to the electric signal. You need to completely bypass the deck or your always going to have that issue.
 

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As long as your dealing with the factory radio, whether its bluetooth or whatever, as long as your running it through the VW deck its controlling the frequencies. Aka rolling off the lows to protect the factory speakers. That's your issue. You can raise the bass all u want it's still going to do Volkswagen voodoo to the electric signal. You need to completely bypass the deck or your always going to have that issue.
I was thinking the same for the OP but he mentioned having intense bass when he ran the sub off the 4ch. He couldn't have had intense bass then but not now if it was bass roll off from the factory head unit. But if by chance that is what it is then an Audio Control LC2i can fix the issue without having to bypass/replace the HU.
 

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I was thinking the same for the OP but he mentioned having intense bass when he ran the sub off the 4ch. He couldn't have had intense bass then but not now if it was bass roll off from the factory head unit. But if by chance that is what it is then an Audio Control LC2i can fix the issue without having to bypass/replace the HU.
Incorrect. That doesnt bypass that factory EQ. I have a 19 GLI. I run a dap as my source via coax. That's how you do it. If your trying to keep the factory radio and integrate you need something to manipulate that electric "input" signal. And even with those options it may not fully correct to flat. I had the same issue with same base model car. The only option to completely avoid that and the best option for me was a digital source running digital straight to dsp. Gave me a completely flat signal to start with. Accubass from audio control does not correct that issue. It's just an EQ for the bass output. His problem is the manipulation of the electric input signal period
 

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Incorrect. That doesnt bypass that factory EQ. I have a 19 GLI. I run a dap as my source via coax. That's how you do it. If your trying to keep the factory radio and integrate you need something to manipulate that electric "input" signal. And even with those options it may not fully correct to flat. I had the same issue with same base model car. The only option to completely avoid that and the best option for me was a digital source running digital straight to dsp. Gave me a completely flat signal to start with. Accubass from audio control does not correct that issue. It's just an EQ for the bass output. His problem is the manipulation of the electric input signal period
Can the head unit settings be changed with Vagcom? I drive a MK6 GTI, and that generation could be changed to a fullrange signal by using vagcom to defeat the OEM processing. I have no idea if this can be done on the newer models, but if it's possible, that would be the easiest solution.
 

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Incorrect. That doesnt bypass that factory EQ. I have a 19 GLI. I run a dap as my source via coax. That's how you do it. If your trying to keep the factory radio and integrate you need something to manipulate that electric "input" signal. And even with those options it may not fully correct to flat. I had the same issue with same base model car. The only option to completely avoid that and the best option for me was a digital source running digital straight to dsp. Gave me a completely flat signal to start with. Accubass from audio control does not correct that issue. It's just an EQ for the bass output. His problem is the manipulation of the electric input signal period

We were talking about bass roll off which accubass is a fix for. For a full factory eq then yes I agree you need something else.

You say it is the input signal so how do you explain the 4ch amp being able to give him more bass? If it was the input signal then even the 4ch would have sounded low.
 

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However changing from the RVA to the Kyrpton somehow made my sub produce less sound. Its sounds better and definitely has a more balanced frequency range but it is not loud.
A few have already mentioned VC wiring... have you verified polarity (9V or something)? "Verify the wiring" doesn't necessarily mean the same thing to everyone, so I'd hate for something that simple to be overlooked. No disrespect. The description above is how I would describe my subs 180 degrees out. Could have corrected it when hooked up to the 4 channel.
 

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Can the head unit settings be changed with Vagcom? I drive a MK6 GTI, and that generation could be changed to a fullrange signal by using vagcom to defeat the OEM processing. I have no idea if this can be done on the newer models, but if it's possible, that would be the easiest solution.
I have heard of this before although I'm not sure about the newer mk7+ platform.
 

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We were talking about bass roll off which accubass is a fix for. For a full factory eq then yes I agree you need something else.

You say it is the input signal so how do you explain the 4ch amp being able to give him more bass? If it was the input signal then even the 4ch would have sounded low.
Well... I'm assuming his 4ch amp gave him more bass than factory. I'm assuming hes comparing it to the factory speakers. At the end of the day I'm only speaking from experience.I have the same exact car, base model. I dealt with the same issue in the beginning when I wanted to factory integrate so I'm not speaking like a shot in the dark. This is my build. I am literally just suggesting what I did when I ran into the same issue and what my suggestion would be. If your interested in this as a hobby and possibly upgrading things down the line then the very first thing "I" did was figure out the best source possible. When your setting gains your setting them off of diff frequencies. So whether your using "accubass" or not, your gains are being set off the electric "input" signal. An LC2i does not give you the option to fix your input signal. If you read any basic gain setup tutorial one of the first instructions is to set everything to "flat". This guy has everything altered at the deck so he is setting his gains off that signal. All accubass does is boost a few lower frequencies at a specific volume level. That does not deal with his issue it's just a cheap bandaid. But who am I to judge maybe he isnt looking to maximize his setup. You cant setup your gains properly if the factory deck is EQing the signal first. You can get a dap cheap as ****. Also he mentioned playing lossless from amazon. Well none of that matters because his source doesnt play lossless back. The source is one of the most important parts of your system and avoiding dealing with it is like paying for equipment and only wanting it to work at 50%. I dunno about anyone else but I nipped this issue straight in the butt when I ran into it. Never looked back. Why spend money on a ton of equipment just to go cheap on install... that's the mindset right!? What do I know tho it's not like I design and built my entire setup myself literally from scratch...👨‍🏫
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Discussion Starter · #20 ·
Incorrect. That doesnt bypass that factory EQ. I have a 19 GLI. I run a dap as my source via coax. That's how you do it. If your trying to keep the factory radio and integrate you need something to manipulate that electric "input" signal. And even with those options it may not fully correct to flat. I had the same issue with same base model car. The only option to completely avoid that and the best option for me was a digital source running digital straight to dsp. Gave me a completely flat signal to start with. Accubass from audio control does not correct that issue. It's just an EQ for the bass output. His problem is the manipulation of the electric input signal period
Thank you for your input, I believe this is my issue and Im going to see if the lightning to RCA is a good substitute.

What DAP do you use in your car?

As for today I reset all my settings and set my gains by ear. I changed the eq on the HU to flat and set the gains on both amps to min and turned them up until either it was too loud or started distorting. Not sure where I set my HPF for on my 4 chan amp but I now have a bit more bass up front which helps balance the sound more. Its now good sounding music with clean responsive bass but its still not the trunk shaking I want.

Just got a quote from a well established audio shop near me, they suggest if I want to get more bass Id want to get 2 10” subs and they reccomended 2x kicker comp r’s in a pre-fab box with a kicker 800 watt amp. Theyre pricing was fair but they want to redo all the wiring and add an LC2i which would total to about $1300 after labor. I might just go through with it to avoid anymore headaches. But tbh is licker really worth $5-600 price tag? They gave me a demo of 1x comp r in a new g wagon and it shook the thing, so I can only imagine what 2x will do in my car.

Will update again once I recieve the l
 
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