The higher the Hz @ HPF, the less bass the speakers get right?
What does LPF do?

HPF (High Pass Filter): allows only frequencies above cut off point to pass through

LPF (Low Pass Filter): allows only frequencies below cut off point to pass through

Yeah, and the Ndb/oct is the slope of the cutoff.

12db/oct in a HPF means that for every halving of the frequency, the output will drop by 12db.

12db/oct in a LPF means that for every doubling of the frequency, the output will drop by 12db.


So, even though you have a HPF set up, the speakers are still getting some low frequencies and could be overworked trying to produce bass frequencies. A steeper slope (like 24db/oct) helps. 6db/oct (which is what you get using a capacitor on a speaker) is unsuitable IMO - the slope is not very steep.

I believe my headunit maxes out at 180Hz (so 18db/oct)?
I'll put that up and test it out then.

That will definitely help the main speakers from trying to reproduce any bass, but don't go too high because if there is too much of a gap between the main speakers and the sub, you'll notice a gap in midbass sound. And if you increase the LPF filter for the sub, the higher frequencies produced by the sub will pull the stereo imaging towards the sub (mids/highs are directional while bass frequencies are more omni-directional).

I would go around 140Hz on the main speakers and around 120Hz on the sub, even at 18db/oct.

EDIT: I just re-read your last post. Just because the HPF tops off at 180Hz doesn't necessarily mean it's 18db/oct. You should be able to find what the actual slope is for your device via a google search or the device's docs. Common values for "active" crossover slopes are 12db/oct (so-so), 18db/oct (good), and 24db/oct (best). Slopes higher than that are good too, but aren't common. "Active" crossovers are ones that use DSP or other active (powered) circuits to handle the crossover, and are done before the signal gets to the amp. "Passive" crossovers just use capacitors and inductors (and sometimes resistors too) between the amp and speakers, and do introduce insertion losses and can also reverse the phase, so are more difficult to build correctly.

Well, I didn't want to confuse him with the slope.... figured he was working with the built in crossovers in the head unit...no choice of slope there.

Yup, working with built in headunit crossovers.

But FWIW, my sub does have a knob for frequency (gain, probably) and phase?
I assume none of these will work with the HPF/LPFs.

It actually maxes out at 140Hz, so put the HPF at 140, and the LPF at 120.
Everything sounds much better!
This is sweet!

Pictures will be coming!

So, ended up getting a head unit with slopes built into the head unit..
I'd like to get this tuned up and stop it sounding TOO ratty.


Sooo any other recommendations?
Going to try the above tomorrow morning!

Still on stock speakers, so want to keep speakers on as much high/mids as possible, and leave the bass to the sub.

It can be quite difficult to set up an EQ properly to get the sound you want because the shape/size/materials in the car can play havoc with the sound. You could spend lots and lots of time hunting around for the ideal setting. Really, what you need to do is "calibrate" your system for your specific car, and then make adjustments to suit.

If your headunit has enough equalization bands (7 at the very least, but more is better), you could head to a shop that has a spectrum analyzer. They position a microphone in the car seat and play some "pink noise" over the system. Pink noise sounds like white noise, but while white noise is just random combinations of various and changing frequencies/amplitudes, pink noise is a combination of all frequencies at equal volumes. Then, adjust your EQ so the response curve on the spectrum analyzer is as flat as possible. Most analyzers I've seen have 31 bands, so if your HU has fewer EQ bands you might not be able to get a totally flat response, but better than nothing.

Once you get a baseline flat response, you can adjust from there to suit your preference. If your HU has the ability to store different curves, I would save that baseline configuration as profile #1 and then save your edits in a different profile so you still have your original. Or at least take a pic of your baseline EQ settings.

Be aware that replacing speakers with different size/brand, adding different carpeting, new floor mats, different HU will throw off the flat baseline response. So I would replace everything you plan on replacing and then doing the above procedure to be as consistent as possible.

If your HU only has a few EQ settings, you could get a 31-band EQ and put that between the HU and amp(s). This type of EQ has a band for each of the spectrum analyzer bands so is much easier to set right. This EQ is something that is only adjusted once and then put out of sight after you get the flat baseline curve using a spectrum analyzer - basically a calibration tool to match your car and that's it. Make sure your HU's EQ is set flat before you set the 31-band EQ though. And of course, this would only work if all speakers are amped.