Adding a tweeter seemed to also increase bass response

Question

I recently added a pair of tweeters to my car's front pair and what "baffles" me is that after adding them, I hear more bass besides the added highs. (electrically, it was a simple parallel connection, with no other than the tweeter's included "internal" 3.3 uF capacitor)

I'm trying t learn whether this is some psycho-acoustic effect or electrically caused, in order to read further. I don't think it is simple "placebo" as I was expecting no effect on bass. I'm reading about "Virtual pitch", but I seriously doubt it can "happen just by chance", my understanding is that it's used in some modern devices but it is done through complex digital processing, not just the physics of the drivers/enclosures.

I have fiddled several times with speaker drivers before, but never experienced a perceived bass response by adding tweeters. Sadly I do not have any measurement equipment, and the installation requires removing the door panel and some more screws, so a quick A-B comparison is not possible.

I know this is subjective, but to illustrate what I hear: I usually had this radio tuned with the treble adjustment to the max (And it was never enough, never felt a balanced sound, so I added the tweeters) and the bass adjusted about 3 notches bellow max, somewhat 5 notches over it's neutral point. The H.U. provides about +/- 10 notches of adjustment, the control is not numeric, so, it's hard to tell. After adding the tweeters I use treble one or two notches up and bass about three notches up and still think I hearing louder bass than before. For reference, I mostly listen to 60-80's British and American rock and its derivatives, and some Latin, Afro-Caribbean music. I'm not a "bass head" and do not listen to techno or rap very often.

I have some experience empirically building bookshelf speakers (with mixed good and bad results, so I thrust my ears more than not). Also, I've had this car for more than 11 years. The head unit and front speakers are the original O.E.M ones, and the only prior change I made to the system was connecting aftermarket speakers to the previously unused rear channels, and it was done more than two years ago, that is, I'm pretty confident "I know how it sounds".

If it matters, this unit has the feature to reduce bass progressively as volume increases. I have always though it is some fixed EQ profile. Could that circuit be affected by an external component?

I also posted this question on the electronics S.E. :https://electronics.stackexchange.com/q/616506/214993

Answer 1

At 100Hz, a 3.5uF capacitor has an impedance of 480ohms. In relation to the involved real impedances, this is quite large and so will not make a difference in the bass response as such.

Now it's totally unclear what you consider "more bass". "Trusting your ears" means absolutely zilch without having constant exposure to references and/or measuring equipment. In particular it means zilch if your listening habits and material are as you describe them, with the focus on car audio, bass-heavy music, turned up tone controls and so on.

Now assuming that with "bass" you don't mean non-reed organ pipes, bass recorders or similar but rather (typically electric) basses used for laying bass lines in popular music, those have significant overtones for cutting through and anchoring both their harmonic and rhythmic function. Those overtones that provide the audible "cut-in" part of the bass rather than the "body-shake" component are more situated in the low mids (or even higher mids) of the soundscape, and those may have seen a bit of different emphasis due to your not having dialed up the trebles as absurdly high as previously (there is even the possibility that the logic for a digital implementation of a "loudness" kind of bass/treble emphasis at lower volumes throws up its hands and does not do a lot when the treble is already dialed up beyond the point of no return).

Answer 2

I think this is off topic and will be closed but…

the addition of higher frequencies won’t have an effect on the bass response but, if everything is as you say, the part of adding another speaker that COULD increase the loudness of the bass compared to your volume knob position is the total load in the amp. You said you wired it in parallel so you lowered the resistance allowing for more output wattage at the same setting.