Shaker / Pro Speaker Crossover Points?

[RevvdMedia]

Does anyone know, or can anyone "test" the crossover points on the front speakers? I know the signal going into the factory amp is line level full range FL, FR, RL, RR. Somewhere along the line I assume the signals are being cut off / crossed over. I noticed when I did my front component install (6.5" woofer and 1" tweeters) I feel as if I am missing some frequency ranges as I disconnected the factory 3.5" speaker, mostly in the mids. Using the rear speakers as fill seems to "fill in" the missing frequencies, or at least it sounds that way. I would imagine if the woofers are limited to xxxxhz, and the tweeters start at xxxxhz, there could be a possible gap somewhere.

Is this crossed over in the amplifier (Woofers to ~1000hz and 3.5/tweeter everything above that point), or is it in the wiring to the speakers? I know some guys have done amplifier replacements but haven't reported a loss in fidelity, so I imagine the amp is doing some of the crossing over?

I'm probably going to throw in a couple 3.5" speakers down the road as I am going to take the doors off again and replace the push pins with new ones as I have a slight door rattle, probably from removing the doors cards over and over. Just wondering what we are working with.

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[nanotech]

According to the wiring diagram provided in the "Stereo Information" Sticky and shown below, the A-pillar tweeter and 3.5" door "tweeter" on each side receive the same signal. Based on this, I would agree that what you're hearing is likely a gap between the high-pass filter on the amp outputs feeding the tweeters and the low-pass filter on the amp outputs feeding the door woofers. The A-pillar tweeters just don't have the frequency response needed to reach down to the lower end of the range covered by the 3.5" drivers in the doors. Additionally, I haven't seen any evidence of passive filter components on the drivers themselves or in the wiring harness, so I believe you're correctly assuming that the filters are contained in the factory amp. (Correction: A-pillar tweeters have capacitors connected in series as described below.) As to the amp's crossover points, I wish I had more information to share. We'll have to wait for someone to connect an oscilloscope or spectrum analyzer to find the crossover frequencies and slopes.

 

[Redalty]

The frequencies are crossed over at the amp and the tweeter has a capacitor mounted to it that takes that frequency even higher.

 

[nanotech]

The frequencies are crossed over at the amp and the tweeter has a capacitor mounted to it that takes that frequency even higher.

Very interesting! Does the capacitor have a value printed on it? If it does, we can tell where the crossover frequency with respect to the 3.5" door midrange is since they're both fed the same signal. If it's simply a capacitor connected in series with the tweeter, then we also know it's a first order high-pass filter which would roll off at approximately 6 dB/octave.

 

[Redalty]

I want to say it had 4.5 uf printed on it but that can be completely off. I reused it as well as the factory plug while installing the new JBL gx components.

 

[GoBlues38]

I want to say it had 4.5 uf printed on it but that can be completely off. I reused it as well as the factory plug while installing the new JBL gx components.

4.5 @ 4ohms (2nd order) would be around 250 hz


http://www.tune-town.com/Cars/stuff/pac/pdf/crossover.pdf

 

[nanotech]

4.5 @ 4ohms (2nd order) would be around 250 hz


http://www.tune-town.com/Cars/stuff/pac/pdf/crossover.pdf

If it's a 4.5 µF cap, a first order filter on a 4 Ω load would yield a -3 dB point of 8842 Hz.

R1 * C1 = 1 / ω = 1 / (2 * pi * fc)

That's seems like a really high cutoff, but that could definitely explain the noticeable gap in frequency response when the OP eliminated the 3.5" drivers in the doors, assuming he also reused the factory capacitors.

 

[RevvdMedia]

If it's a 4.5 µF cap, a first order filter on a 4 Ω load would yield a -3 dB point of 8842 Hz.

R1 * C1 = 1 / ω = 1 / (2 * pi * fc)

That's seems like a really high cutoff, but that could definitely explain the noticeable gap in frequency response when the OP eliminated the 3.5" drivers in the doors, assuming he also reused the factory capacitors.

Man we have some smart guys here!

Great info everyone. I guess for the cost I really should just buck up and spend the 90 bucks on some matching Hertz 3.4" speakers and replace the factory speakers. I tried running the system with my new components installed and the factory 3.5's hooked up, but the new components sounded so much better that it felt like the poor quality sound coming out of the cheap paper 3.5's just made it sound worse.

I've been wanting to dive into the doors once more to put in new push pins anyway, so if I end up doing that, might as well just throw in some new speakers, it'll only take about 20 minutes anyway.

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