Designing 2-way Vifas (For car) (1 Viewer)

[Chris Tsutsui]

I've finished designing a 2-way speaker for my Car.

Since the baffle will be made of MDF and mostly fiberglass in a door panel, I am not concerned with baffle step and other audiophile related factors. The tweeters are not even aimed at the listener, but are pointed more in the general direction, and there IS no sweet spot.

Anyways here's the design:

It is using:

269-370 VIFA 1" ALUMINUM DOME TWEETER .. $18.77
299-490 VIFA PL18WO-27-04 7" WOOFER .. $37.54

The tweeter has 90db sensitivity, and the woofer has 89. I was going to add 2 resistors to attenuate the volume of the tweeter to 89db if that becomes an issue.

I'm also adding a zobel network to the woofer consisting of a 44uf cap and a 3.75ohm resistor.

The tweeter is 6ohm and the woofer is 4ohm which shouldn't be too hard on my soundstream 40wpc car audio amp. Does anyone know how I calculate the impedance of the completed speaker? I could always use an 8ohm woofer instead if the impedance is too low for my amp.

The crossover will be at either 3k or 2500 depending on which one I like better. (or something in between). It will be a 12db 2nd order linkwitz Riley. If you suggest a 3rd order or a 4th order will suit this speaker better please let me know.

The box will be a sealed 4L door enclosure with a QTC of .71. I will try and reduce the cabinet resonance as much as possible with bracing, MDF, and damping material. The F3 is at about 95hz sealed. in a vented enclosure tuned to 55hz, the F3 is 63hz. The Speakers will likely be the sealed version crossed over at like 100hz with a Tempest tuned to 24hz in a 3.5CF box.

If you're wondering why I chose the tweeter and woofer.. One reason is because they are "Infinity" buyout at partsexpress. The other is because the tweeter is protected with a grill in case somebody accidentally trys to kick the dome.

Please post any suggestions.

 

[Dave Milne]

Chris,
I, too, am contemplating some autosound projects. This weekend, I'll try some modeling with the drivers you listed. With regard to your impedance question, I would guess it would be effectively 4ohm nominal, since most of the range of significant power is covered by the woofer. Your Soundstream amp should have no problem with this.

You might want to consider upping the Q and F3 slightly (to 100Hz) with a smaller sealed box and then pairing a 12dB 100Hz highpass with a 24dB L-R lowpass for overall 24dB symmetrical L-R response.

 

[Chris Tsutsui]

Thanks!

A 12db 100hz high pass with a 24db L-R low pass? What components do you mean to put those on?