Everyone’s had this issue before at some point in life. You’re mixing a song, and you realize that you can’t hear the extension of the bass in your mix down to the lowest point. You export the song, play it in the car, and then get instantly blown away by the sub notes. Frustrated, you leave the car and wonder why you can’t get this right.
It’s no easy thing to solve, but I’m going to try to give you a couple of obvious solutions, as well as a few more underrated ones.
Take your Laptop/Computer to your Car
If you found the problem by listening to your track in the car, then it makes sense that you’d probably be able to fix it by taking your computer to the car, connecting the Bluetooth, and streaming the audio to your car speakers from your DAW. There’s a bit of a setup process required to get it to work, depending on what operating system you use(you might have to use asio4all in windows and then play around with certain settings in the actual asio4all window), but eventually you’ll probably find the way there. One thing I found with Mac OS and my car, is that you can only play projects in 48khz, not 44khz. This may be problematic, try not to mess up your projects accidentally in the process. Pro Tools has a nasty habit of completely breaking in situations like this(sometimes with no point of return).
Reference your song against commercial songs with something like metric AB and try to match your bass like that in the car. You should be fine.
Headphones?
I’m not going to suggest headphones, because the truth is, they’re incredibly hard to hear when judging bass, no matter which set you to get. Yes, some sets have extended bass frequencies, but depending on how well your ears are trained to hear it on headphones, it’s probably not going to be suitable for you. Rather focus on the other ways.
Buy speakers that go low in frequency range?
Obviously, if you could do that, you wouldn’t be in this problem in the first place.
High-Quality Full-range speakers tend to cost a ridiculous amount of money, and for the most part, are not accessible to most people. You can definitely add a sub to your speaker set, but there are some issues on how much the room is going to interact with your sub, as well as sub placement that can really mess things up. The issue with this is that most subs are too powerful for the room they’re placed in, and there’s usually not enough proper acoustic treatment in a room to be able to handle a sub and give you the information you need(despite what you may think).
Dave Pensado Trick
Dave Pensado showed this trick on his one into the lair episodes.
He’d filter off all the high frequencies with an EQ on his master bus, say, everything above 100hz, and then mix the bass like that. He said that even with speakers that go down to 35hz, you can still get more information on the bass than if it’s being masked by all the other frequencies as well. I’d definitely recommend referencing against other songs in order to get this right(also filtering off their top end, so put the filter after say, metric AB and then switch between the two tracks).
Mix Visually
This sounds like terrible advice. And to some extent, it is.
But there are ways to make this work. You could, for example, get bass stems of popular songs(you could probably separate them using a website like https://www.lalal.ai/) and try to reference the volume of the separated stem to the volume of the track you separated it from. Then, try to reference your bass to the volume of the separated stem(once you’ve ensured that both your entire track and the full reference track are the same volume).
A bit of a confusing, complicated mess to get this to work, but if you understand it, you could technically find a path forward. You could then look at the spectrum analyzers in detail, and ensure that you are matching db to db on EQ. Of course, you could also use something like Tokyo Dawn Labs Nova GE Edition, which would read your current bass track, and then simply match the spectrum of your bass track to the one you’ve pulled with lalal.
Again, nothing’s ideal, but when you’re desperate, you’ve got to find a way.
Acoustic Treatment
Now, this isn’t really going to increase the extension of your low frequencies if your speakers don’t support it, but it’s going to make the frequencies you do hear much clearer, which will help you make accurate decisions about the bass. You should probably put a huge amount of Rockwool in the corners of your rooms, but each room is different and might require more, or less. Always do measurements before and after to see if it’s decreased the RT60 and etc.
Hopefully, that helps!