Need advice on car stereo speakers

[zomby woof]

I'm a big fan of the Infinity stuff, and you can often get last years, or display units at a significant discount on ebay

[billfitzmaurice]

Infinity and JBL are both good, but the list prices verge on absurd. I put some JBL tweeters in my car, which I never would have considered at the $109/pr list price, but at the Amazon price of $39 they made sense, especially as that included adequate HP filters. At $99 on Amazon the JBL GTO 609C is a reasonable price for a pair of woofers, tweeters and full crossover, but there's no way it's worth the $249 you'd pay buying at retail.

[breadfan]

I have more questions, what would be a good crossover point for these? Now I'm really going to look stupid but if I don't ask, I will not know. Say I pick a X0 point of 3500mz, I go to a X0 calculator (2nd order butterworth) and put in the impedance of 4ohm for the woofer and 4 ohm for the tweeter, why does it come out with the exact same cap and inductors? I know this can't be right. I'm really trying to learn this stuff but I can only read what is on the web and, well, it obvious I am lost. Going to the Metallica concert tonight so I will pick up on this up tomorrow, hopefully my ears will still have some hearing left!

[6thplanet]

Basically that calculation assumes that the tweeter and woofer are purely 4ohms across its full FResponce, which they are not. That's the problem with calculators like that.

[billfitzmaurice]

For dispersion you want as low a crossover as the tweeter is comfortable with. Based on Fs and FRD that Peerless should be fine to 2kHz with a 3rd order filter, and the cost going from 2nd order to 3rd order is only that of one additional capacitor. Leave the LP 2nd order, there's no reason to go 3rd order there.

[Millstonemike]

when deviating from auto speakers, make sure you stick to 4 ohm drivers. Most auto amps rated power are into 4 ohm speakers.

[breadfan]

Basically that calculation assumes that the tweeter and woofer are purely 4ohms across its full FResponce, which they are not. That's the problem with calculators like that.

So when you buy an 4ohm or 8ohm speaker, it may or may not be the rated impedance? And if that is true, how would one go about calculating (even in the ballpark) a basic crossover without knowing how to use and owning all of the measuring instruments?

[breadfan]

when deviating from auto speakers, make sure you stick to 4 ohm drivers. Most auto amps rated power are into 4 ohm speakers.

Yes, I understand that, big difference, thank you.

[breadfan]

For dispersion you want as low a crossover as the tweeter is comfortable with. Based on Fs and FRD that Peerless should be fine to 2kHz with a 3rd order filter, and the cost going from 2nd order to 3rd order is only that of one additional capacitor. Leave the LP 2nd order, there's no reason to go 3rd order there.

Understood. Another question about these calculators, how do you know what gauge wire to use for the inductors?

[Millstonemike]

Understood. Another question about these calculators, how do you know what gauge wire to use for the inductors?

Your earlier question on how to calculate the XO given the changing speaker impedance ... there is modelling SW that uses the driver's impedance graph (in data form) to model the XOs effect over a range of frequencies (e.g., 20hz to 20Khz). It's fairly complicated for a new comer to absorb all the modelling aspects (maybe someone here will design an XO for you).

Your question above ... the type, gauge and inductance of a coil will determine its DCR (DC resistance) - included with coils' specifications. That figure is entered into the above SW and its effect is included in the overall model. A designer may choose a coil with a different DCR (ex, different gauge) to see it's effect on the model.

Not from me but from what I've read from other users with auto experience... car cabins are extremely difficult to model given their nature. The effect on the low end is known to increase bass; "Cabin Gain". The effect on mids and highs is variable as each cabin if different. Therefore more experienced users have suggested using a head unit with graphic equalization (or separate graphic equalizer) to tailor the finished system to your liking.

[Sydney]

... how do you know what gauge wire to use for the inductors?

Don't take this the wrong way; this strikes me as being over-analytical for what started out to be just an upgrade.

[zomby woof]

Says the pot to the kettle...

[Sydney]

I want to upgrade my four 6.5 coaxal speakers in my car.....

I'm not trying to blow my mind with car audio,

Kitchenware platitudes aside

[Thumper Tom]

You could also look at going active, replace your factory radio, use the 4x50 amp to power the tweeters and woofers, and not use the rear speakers. Then you can save money on crossover parts and use that for the new head unit and remove a lot of the complexity. Trust me, you don't need the rear speakers if you invest in the fronts. My recommendation for a head unit, Pioneer DEH-80PRS.

[breadfan]

Don't take this the wrong way; this strikes me as being over-analytical for what started out to be just an upgrade.

That's funny! I knew going in what would happen. This site is way above me, sure I can solder together a bunch of little parts from a proven XO, hook them to a speaker and make them sound good. But, I can't tell you how I'd come up with those parts. Frustrating to say the least.