After doing a few tests, I feel confident in saying that there are no crossovers in the non-hifi stereo. All the 6 speakers in the setup receive a full range signal. The front speakers are wired in parallel so they present a 2-ohm load to the stereo. Check out my other post titled OEM Stereo Frequency Response to see the audio signal the stereo is putting out.

My guess on the hifi setup: I don't think there are any real crossovers in this one either. I've read that there is a first order high-pass filter(aka. capacitor) for the tweeters. The other speakers probably also get a full range signal just like the tweeter. If the system does have some kind of crossover, I'd say they are probably active filters before the power amp stage. If this is the case, the built-in filters will not affect aftermarket crossovers like others have mentioned. I really dont see them designing a custom amp with passive crossovers but maybe they did.

In both systems, the speakers themselves act as poor filters.

Edit:
Some of you noticed what seems to be a contradiction: I said there are no crossovers in the system yet the rears seem to have a high-pass looking response. To me, this doesn't show a "crossover". It shows that the preamp or the power amp is high-pass filtered.

I don't consider the rears to have a crossover because it is a single output single input setup. Crossovers are used to send different sets of frequencies to more than one device using a single output. Take a look at the pic in post #4. It should clear things up.

 

Then why would a professional installer feel the need to use a Cleansweep on a non-hifi system? Perhaps there is something about the Cleansweep I don't understand.

In my HIFI system, all the bass seems to go to the 5.25" speakers in the front, and the 6x9 in the back only get mid to high. This is what my ears tell me.

 

robin - a little late to say that since he already posted graphs showing exactly that in another post.

it does contradict his OP though.

it reminds me that when I had replaced just my fornt speakers how I was saying the fronts put out much more bass than the back - I thought it was just from having higher quality speakers up front.


It IS strange though that the biggest speakers in the system don't get the lowest lows in the system.

 

Some of you noticed what seems to be a contradiction: I said there are no crossovers in the system yet the rears seem to have a high-pass looking response. To me, this doesn't show a "crossover". It shows that the preamp or the power amp is high-pass filtered.

I don't consider the rears to have a crossover because it is a single output single input setup. Crossovers are used to send different sets of frequencies to more than one device using a single output. Take a look at the pic below. It should clear things up.

 

The Cleansweep attempts to correct the frequency response of the stereo. It tries to make it so that all the frequencies output at the same level. If you try to use the Cleansweep to "clean" up the rears, you still wont get the same low end as you would in the front. There is not enough clean signal present to match up with the rest without introducing a ton of noise.

Edit: I just realized that the other OEM integrators are also called Cleansweep. I was refering to the 441dsp above. JL also makes a signal summer (CL-SSI) that could be used to combine the front and the rear if you wanted to.

The HiFi probably uses the same stereo so the response will be similar unless the external amp tweaks the signal.