The issue you are experiencing is the Fletcher/Munson effect that low and high frequencies are not heard at the same level when dB are lower. No curve is going to fix that without negatively impacting how the system sounds at higher dB. What solves this is what's typically called the 'loudness' feature on AM head units. They factor in the Fletcher/Munson curve and add low and high frequency on a scale to match the curve depending on the volume you are playing at.
I had the exact same issue as you. Always had to play my system loud to enjoy it. Anything lower than that sounded dull. Then I read a thread that said don't be afraid of your loudness feature - it won't bite. I started using mine on 'low' and have never looked back. The system sounds so much better enjoying it at any volume level now and I find myself not turning it up as much constantly to enjoy a song.
The red curves show the amount of extra SPL it takes for humans to perceive the loudness at lower frequencies to be equal to the loudness at midrange frequencies. Remember that this is a "perceptual" thing and all humans perceive things differently. The curves are "representative" of the perceptions of most people.
if you turn them off for the left side you still need to turn them down 6db for the right side...
if you tune everything else sided without subs you can then play both sides together and tune the subs at 0db to the two sides played together... that does the same thing as turning the subs down 6db and tuning left with sub, right with sub, then together with sub turned back up 6db...
whichever you do you need to end up with everything playing looking like the house curve
Sorry i'm a complete novice can you explain turn down the subs by 6db? I'm using auto tune and i'm tuning with sub off. It's also right hand drive car if it matters. I do both sides of the car without the sub then i do the sub then i do all drivers together. Which point am i supposed to turn down the sub by 6db?
Cheers
I haven't messed with it, but if your Helix model supports the Augmented Bass Processing, it's something to look in to.
Augmented Bass Processing
Audiotec Fischer’s proprietary “Augmented Bass Processing”, consisting of the two revolutionary sound features “Dynamic Bass Enhancement” and “SubXpander”, has been especially developed to dramatically improve the bass reproduction of subwoofers.
The “Dynamic Bass Enhancement” ingeniously combines maximum deep bass and highest sound pressure – regardless of the music style or the tone controls in the head unit. Depending on the input signal, the “Dynamic Bass Enhancement” gains the lower frequency range and varies the cut-off frequency of the subsonic filter. The result is a significantly more powerful and deeper bass response at low and medium volume levels without the risk of overloading the subwoofer neither mechanically nor electrically at high volume levels. It is simply fascinating which bass performance is suddenly possible.
If you want an even lower and “darker” bass reproduction, the “SubXpander” can be additionally activated. Therefore, subharmonic tones are added to the fundamental tones in the frequency range between 50 and 100 Hz.
as long as both left and right are turned on you don’t need to turn the sub down...
think of it like this...
left plays at 90db, right plays at 90db... if your ta is correct and you get perfect summation the two together will play at 96db
if you instead play your sub with the left at 90db and then the right at 90db but then you play both sides together your front end is now at 96db and your sub is still at 90db and sounds anaemic...
you tune the sub at -6db so it matches left at 90db, do the same with the right... then turn both left and right on so they play at 96db and turn the sub up 6db then everything plays at 96db and all is in balance
That's why i like using two channels for sub in my Mosconi D2.
Just mute one sub channel and adjust the sub to the left (or right side for that matter) and then unmute everything when playing together.
SYNC3 headunit
Mosconi Pico 8/10 DSP
Mosconi D2 500.1
Gladen Zero Pro 165.3 DC
JL Audio 10w3v3 in custom enclosure (Blueprint by Mark @Caraudiofabrication)