Adding an Amp Questions

[matthewxeric]

SO I have a Rockford p4002 amp that I took out of my old car to put in my new cx-5. I also took out the polk crossovers i had, but didnt take out the polk component speakers. Before I get started and take everything apart, I have a few questions I'm hoping you guys could help me with.

1. Is their a front and rear output on the back of the oem head unit to go to my amp?
2. What Materials will i need beside a bunch of speaker wire and power cables? I havent seen the back of the unit and dont know if i need some sort of signal converters.
3. I have the polk db351 in the dash and a jbl gx602 in the front. Should i use my crossover to split the signal even though my jbl is a two way coaxial.

Any help would be greatly appreciated. I installed two amps, all new speakers and 2 subs in my last car over ten years ago. Everything is a little fuzzy, but i'm hoping when i start it will all come back to me.

Thanks

 

[squibcakes]

Hi,

For interest you didn't say which HU version you have, Bose, Non bose with navigation etc... In any case there are no pre outs that I know off (Bose version does but they are fed into the bose amp which people have had issues tapping into)

What you can do, is use a non powered High level to low level converter (like PAC audio ) which is the cheap way of doing it and works well.
You could use a powered converter like the LC2i or LC6i from audio control but will cost you more.

You will need a fuse and fuse block for your power cable at the battery end. Some dynomat in the doors would go well to since you are fitting speakers.

Since you have already fitted two subs in the past - you will be very disappointed with the bass in this car. To be honest I think you will wast a lot off effort doing what you plan to do without a sub.

I would bridge your p4002 amp and use it for a sub 400W, and get a 4 channel amp to drive the front door speakers and the dash speakers. Use the amps crossovers to fine tune those speakers.

Better amps can take a high level input so that can save you some coin on the level converters....

 

[matthewxeric]

I'm sorry, that was a typo. My amp is a 4004. 4 channel x 50rms. I also have the touch screen display without bose and without nav.

So you're saying it would be better to use a 4 channel amp for just the front and dash, and leave out the rear? I was planning on using one channel for the front and dash, and hook it up to the crossover to split. Is that wrong?

 

[squibcakes]

Okay you have the same head unit as mine - so def. no pre out.

Both your set of speakers should already have bass blockers fitted so really no crossover unit is necessary.

You really don't need coaxial speakers in the doors - too much high frequency since you also have those in the dash. I would swap out for components or cut the tweeter in the coaxial (but that is just me) to turn it into a woofer.

Here are your best options with that amp and speakers:

1.

Use first 2 channels for the front door coaxial speakers (60W GX602 2 Ohm) at 2Ohms that amp will deliver 100W each channel.
Use other 2 channels to drive the dash speakers (db351 4Ohm 35W) at 4 ohms that amp will deliver 50W each channel.
Drive rear speakers off the head unit​

I would not parallel the dash and door speakers - this will be about 1.5 ohms and may overload the amp!

2.

Buy a second mono amp and add a subwoofer​

3.

Buy a second 3 or 4 channel amp add a subwoofer and also power the rear door speakers.​

There are other ways and options too but think this is enough to get you thinking... keep asking question and don't buy any more stuff until you have a proper plan. Keep asking questions.

 

[matthewxeric]

Thanks a lot for anwsering my questions. I do have a few more.

1. I read that the front and dash are from the same output from the HU. If thats so then are both wires that are going to the front and dash accesible from behind the HU.
2. You say that it would be more benificial to use my amp to power the dash rather then the rear. As of right now, i hear a little distortion coming from the dash when i go to around 40. Would adding an amp to that not make it worse?
3. The dash db351s came with what i believe are 200hz base blockers. If i put a, lets say 600hz on there would it make it distort less? or..
4. if i use that crossover coming from one channel to power both front and dash, wouldnt that take care of not sending highs to my jbls (instead of cutting the tweeter out), and keep the bass from going to my dash?

I'm just brain storming here. I also am not an expert like you guys so anything helps

 

[squibcakes]

Yes they are wired in parallel. From memory the connector where they are paralleled is not easy to get to - deep in the dash somewhere. The connectors at the back of the HU on the other hand is easy to get to. I took my signals from there to the amp.

If you remove the dash speakers - you can run your own speaker wire from there down to the foot wells and to the amp. If you are good at yoga this should be a breeze.

When I put a cro on the HU output it started to distort around 47 on the HU volume. This was my max volume setting when setting the amp gains. I think you distortion due to having a dash speaker of 35W 4 ohm in parallel with the 60W 2 ohm and impedance mismatch. This is why I said before not to parallel the same way the Mazda has even though the Mazda HU wouldn't be putting out that much power anyway... You could try disconnecting the door speakers and see if you have the same distortion.

I don't think putting bass blockers (HPF) on the dash speakers would do anything but you can try. I'm not clever enough to have the answer.

Putting LPF on the doors speakers would block the high frequencies. But you still have the impedance mismatch. Basically you shouldn't be putting both speakers on the same channel. I'm no expert, but i think in an ideal world you would have drivers from same manufacturer so that all drivers have a uniform sound (esp in the front sound stage) - but in the real world it probably doesn't matter.

Another thought, you could use your 4 channel amp to drive each door speaker (using HU rear speaker channels only, use amp 2 channel to 4 channel mode) and then use the HU front to drive just the dash speakers - so no re wiring for for dash speakers. Only thing is you loose fading option between front and rear door speakers.

 

[tibimakai]

If the dash and front door speakers are installed in parallel, what is the resistance? I have never measured it.

 

[matthewxeric]

also, where did you mount your amps. I was thinking about doing it under the passenger seat. I suppose i'll need to take the seat out, but how could i fasten it to the floor?

 

[squibcakes]

Yep front passenger seat. I didn't fasten it diwn as it is heavy enough and fits the foot print under the seat perfectly. Also helps when taking amp out to tune the across over.

 

[tibimakai]

I have made some aluminum spacers, 1.5" long(can be 2" too. I have used some long screws to mount the amps. I have placed them on top of the plastic air duct and at the back, I have used the two spacers. I have drilled into the floor. Not easy, because the sound deadening material gets stuck on the drill bit as it turns.
I have the sub's amp, under the driver seat and the four channel, under the passenger seat.
Sub amp under the drivers seat:
http://www.mazdas247.com/forum/attachment.php?attachmentid=209021&d=1413672051
Four channel amp under the passenger seat:

 

[tibimakai]

Double post, sorry.