OEM Tweeters and Crossovers

Phoenixcolt · Post by **Phoenixcolt** » Tue Apr 07, 2009 12:52 pm

Hope everyone is well.

I am just about to order the dash piece i need from Japan to get a standard headunit into the new Rex and a din pocket. Here's what one guy did that I will be doing except my hu will be on top: http://www.iwsti.com/forums/gr-i-c-e-se ... tenna.html

I would like to run two channels of my RSd 500.4 to the front speakers and bridge the other two for the sub. Nice and solid, yet simple system. I would leave the stock speakers and tweets for now because they r actually pretty good.

First off, Is it a bad idea to run speaker wire from the amp in the trunk up to the oem wiring behind the headunit and amp the front speakers from there, through the oem wiring? Or do I run a good chance of burning up all of that oem speaker wire if it is being powered by this amp and going thru oem speaker wire before it gets to the speakers?

Also, do you guys think that the oem tweets likely have an inline crossover or that the oem headunit has a built in crossover? I would guess that, unless there are seperate wires going out to the tweets and doors behind the oem headunit that there is an inline crossover.

If you guys think amping through oem wire is a risky practice, I may just run headunit power and amp the sub for now. Just trying to get it figured out, I am anxious t get something going.

Thanks.

Post by **Bfowler** » Tue Apr 07, 2009 1:30 pm

the eiasest answer is yes and no.

the 500.4 will make about 150 max watts.

using ohms law, voltage = root(watts x ohms)
we get v= root(150x4)

= about 25 volts at full tilt

that IS a little more then 18 (which is what oem wire usually is) is rated for

so it will get warm...and while doing so the wires resistance will rise, which will reduce the power that the amp is making. it isnt a big enough difference that i think the heat would be a problem.

so it will be ultimately ok and probably wont be dangerous. but it will effect the sound too.

Phoenixcolt · Post by **Phoenixcolt** » Tue Apr 07, 2009 1:43 pm

Bfowler wrote:the eiasest answer is yes and no.

the 500.4 will make about 150 max watts.

using ohms law, voltage = root(watts x ohms)
we get v= root(150x4)

= about 25 volts at full tilt

that IS a little more then 18 (which is what oem wire usually is) is rated for

so it will get warm...and while doing so the wires resistance will rise, which will reduce the power that the amp is making. it isnt a big enough difference that i think the heat would be a problem.

so it will be ultimately ok and probably wont be dangerous. but it will effect the sound too.

All very good points : ). Maybe I should consider just running deck power until I am in the mood to upgrade speakers down the road.

Now how about the crossover question, likely an inline crossover right?

Post by **Bfowler** » Tue Apr 07, 2009 2:27 pm

yes, if it doesnt have a factory amp. then USUALLY there is just a capacitor in line with the tweet.

Phoenixcolt · Post by **Phoenixcolt** » Tue Apr 07, 2009 2:29 pm

Bfowler wrote:yes, if it doesnt have a factory amp. then USUALLY there is just a capacitor in line with the tweet.

Cool, I sure hope it doesnt have a factory amp, i doubt it but it was the premium sound...hope it doesn't because an inline crossover would be just fine.

So Bri, you think you would run the amp to the oem wires?

Post by **stipud** » Tue Apr 07, 2009 3:10 pm

Assuming 4 ohms you'd only be doing sqrt(75*4) = 17.3 volts. Distribute that over a crossover and you'd see even less.

I use factory wiring from my stock amp (kickpanel) to the front speakers, because the wires run through through chunky connecting blocks into the doors. I didn't want to mess with them, so I tried slinging the wire across (without pulling it through the door) to see if there was a difference. I didn't notice any, so I just soldered it up nicely to the factory wiring and haven't looked back.

The stock wire must've been at least 16g though...

Post by **Bfowler** » Tue Apr 07, 2009 4:33 pm

it wont sound as great as rewiring the whole thing. but it would be fine. i did it in my brothers maxima just fine.

i would go for it, then upgrade the wire when you have more time

Post by **ttocs** » Tue Apr 07, 2009 4:44 pm

Bfowler wrote:
using ohms law, voltage = root(watts x ohms)
we get v= root(150x4)

what formula is that?

Post by **Bfowler** » Tue Apr 07, 2009 4:51 pm

ohms law with Voltage as the "solve for" variable (bottom right quadrent of their ohms law circle

http://www.the12volt.com/ohm/ohmslaw.asp

Phoenixcolt · Post by **Phoenixcolt** » Wed Apr 08, 2009 4:40 pm

Any installers out here worked on an 08 or 09 WRX or STI yet?

Post by **Bfowler** » Wed Apr 08, 2009 8:55 pm

no....a 05...
and a 07 legacy...

whats your question

Phoenixcolt · Post by **Phoenixcolt** » Wed Apr 08, 2009 9:10 pm

Nothing yet, I hope it goes smooth that's all. Put that awesome equip to work

! Some Subie guys on Nasioc told me the PG comps will be no prob to fit as long as I get some spacers, so everything is looking awesome from where I sit at my computer desk, haha, actually doing it will be a whole other animal. Just have to start gathering the parts I need to order.

Post by **Bfowler** » Thu Apr 09, 2009 9:19 am

yeah, in the other wrx installs i have done. the back of the door Dannel is a VERY sng fit. it either wont pop back down all the way, or you will hit your speaker.

i had to grind and smooth out the back of the factory grill

Phoenixcolt · Post by **Phoenixcolt** » Thu Apr 09, 2009 5:51 pm

I found a guy who did a really nice job on his STI.

http://www.iwsti.com/forums/gr-i-c-e-se ... dx-jl.html

This guy has been a great help as well, he was saying how important he feels it is to maintain coaxes in the doors and tweets in the a-pillars for imaging.

I may end up sacrificing my tweets in the a-pillars all together and just run the RSd comps with the tweet angled for imaging the best I can in the grille under the door and time align. This guy said he thinks my comp setup was much more thin than the CDT coax setup he had to get the door panel over which was good to hear.

If I want to add the CDT HD-2 Upstage kit to the a-pillars, i guess the xover will receive the signal before it goes onto my RSd comps which is good because I won't need more power or amp channels but I will never be able to time align a system that has the same signal going to two different speaker locations on each door.

How do you feel the imaging would be with this RSd setup under the door panels, time aligned, and Eq'd through the hu?

Do you guys think that the physical soundstage is more important to get in line before you start adjusting time alignment and things?

I think the RSd comps in the doors alone might be sufficient but you guys usually know better. I can boost the tweet signal some through the eq in the hu, and if that isn't enough, I can even switch the +2? tweet boost that is built into the xover if I need more tweet to compensate for them being low on the door. I wouldn't mind some other imaging opinions though, I can't say it is my forte : ).

Post by **stipud** » Fri Apr 10, 2009 10:31 am

Coaxes with extra tweeters up top? That sounds silly to me. Major treble overkill, and lots of point sources to ruin your imaging. Just run RSD comps with the tweets in the a-pillars and it will be great

Phoenixcolt · Post by **Phoenixcolt** » Fri Apr 10, 2009 12:08 pm

Yeah you're right, 4 tweeters is outrageous.

So you think tweets in the a-pillars and mids in the doors will be sufficient?

I would lose my time alignment, that's my only complaint about that.

Will tweets in the a-pillars, mids in the doors give me a better soundstage than comps mounted coax style in the doors?

Post by **stipud** » Fri Apr 10, 2009 12:18 pm

In my experience, putting the tweeters in the a-pillars has worked the best overall, especially if you ever have passengers.

However I do recommend you experiment. Temporarily mount the tweeters on some long wires and move them around to see where you like them best!