Installing an amp, tips?

[Figit090]

I just got my OEM radio working, FINALLY...and i realized trying to revive the thread about my first attempt at this was a dumb idea, and i have new questions anyway...

So..

What's the best way to go about wiring up an amp? I have a Toyota head-unit with an external OEM amp currently. I also have a Kenwood KAC-746 amp that I am hoping will make things better.

I was planning on running my sound like this;
OEM Head Unit ---> OEM Amp ---> Kenwood Amp ---> Dash harness to speakers

How's that look?

Will that help my sound? I have JBL 3.5in 2-ways up front and the rears are 4 or 5 inch Pioneers. right now they sound O.K. but at higher volumes (not blasting, but loud) they have a little trouble. I have to cut the bass a lot to avoid over-working the fronts. I figure the OEM toyota amp doesn't have enough juice... and might help the sound quality overall with the kenwood anyway. thoughts?

I also need tips on power wiring, i'm not sure where to get it from. I'm planning to mount the amp under the passenger seat.

Here are the specs on my Kenwood amp;

Thanks in advance!
Andrew

 

[speed]

Why are you retaining the OEM amp? You can't have amps wired in series, you can "daisy chain" them (parallel)... but theres no real point in doing that for your situation.

As for where to get power, run a 8ga wire from the battery to the amp. There are some rubber plug things underneat the rear seats that make excellent entry points for power wires.

Yes, aftermarket amps will drastically help the sound at higher levels. But just like any other sort of modification, its not the sole fix. A good amp can be made better with better speakers, and both of those can be made better with a better head unit. Think of it like your fuel system. Bigger injectors are pointless without a better pump and afpr

 

[Figit090]

Well, here's the reasons I'm keeping the OEM amp;

1 - The head unit is externally amplified, and that makes changing the wiring a hassle, i just got it to work with the OEM amp and since the head unit doesn't have an amp, it doesn't have positive and negative speaker outputs. I dont know how to remedy that, maybe one common negative for all the speakers? I dont know.

2 - Other stock head units would have an amp built in and i would virtually be doing the same thing if i had an internal amp, and I had the impression that was common. one reason for that is #3

3 - my Kenwood amp has "speaker level inputs" as well as "line in" inputs. I took this to mean 'this is where you connect a strong signal' and 'this is where you connect a weak signal'. I was planning on running the OEM amp to the "speaker level inputs" as my manual directs.

4 - I vaguely remember someone telling me to keep the OEM amp. It will make things eaiser because i would have to cut off the OEM amp plug and rewire it, and even then I'm new at this and I might screw that up and end up with a hacked harness and nothing working.

This is what the manual shows;

it has common input ratings up to 25 watts, and I assumed the OEM amp was at or less than that...and that what i'm planning on doing was O.K.

I'm guessing that most after market stereos have line outs, and thus i would use that, but mine does not. Tell me what you think.

edit: it does say no more than 25 watts though... do you or anyone else happen to know the common OEM external amp output?

 

[speed]

1) Okay I see what you're saying. Headunits with externals amps are yes, a major PITA to wire. Running a "common ground" won't work, as each channel has its dedicated positive and negative leads. To join them would turn your "stereo" to a "mono". Also, the changes in the resistance would be highly unpredictable and most definitely shorten the life span of your equipment.
2) err um... I at a Dairy Queen tonight.
3) Yes, you understood that correctly. Not all amps have the "speaker level input." If it didn't you'd be in trouble, but because it does, you're ready to rock.
4) Yea, don't want to do that.

So yea, now that that is cleared up, you've got it set. (my original impression was that you wanted to have the power of the first amp PLUS that of the second amp... which i was wrong about.) I'm sure you already know this, but matching the input sensitivity to the voltage coming out of the OEM amp is critical to sound quality. underadjusting it will make the stereo louder, but will severely hinder SQ. Turn on the stock HU and amp, play something.. and measure the voltage with a voltmeter, then set the amp to that reading.

Umm as for any other tips... keeping a short distance from the amp to a grounding point is always good. In a setup such as yours its not that critical but its a good habit to get. Um yea, just make sure you ahve a clean ground connection, and that the power wire isn't rubbing up against any jagged metal. IMO you should run new wires to the speakers (16ga) instead of using the factory harness, but that can be tedious.. especially going through the door jam.

Hope that helps.

 

[Figit090]

Yes, yes it does!

Thanks a loot speed!

Dairy queen? That one was hard to understand then? I am tired and i can make sense of it but it actually took me a second. sorry. i'm trying to get my sleeping habits changed, i was almost nocturnal for a bit (bed at 4ish, up at 1ish) ...hence my troubles. The point i made was mute now anyhow.

I wont be rewiring the speakers, i dont believe the setup is overall good enough to benefit from that effort. thank you though. I dont have time to get behind the dash. and into all the panels right now. school starts on the 22nd.

Now, should i unplug a speaker and take the voltage on the output amp socket, or find a spot to read it on the wire, while the speaker is being driven?

I'll go get a length of the wires i need tomorrow.

would you mind giving me a tip on where to route the battery wire to get from the battery to the holes under the seat? at least how i should go thought the firewall? I know of a hole on the passenger side firewall...

i'll know more tomorrow once i have a look at it, but if i have a rough idea i can better guess how much wire to get.

thanks again!

 

[speed]

Well, the dairy queen thing was that i had no reply for it. your statement was accurate and i'm loony, so I told you what I had for dinner.

As for reading the voltage, it doesn't matter if you check it at the amp's output, or at the speaker end of the wire, the voltage will be the same.

As for routing the power wires, because your amp is low powered enough you could get away with 8ga, maybe even a 10ga wire. Wires this small are pretty easy to get through the firewall and route inside. However with my car, i've got 2 amps in the trunk, and for that I ran the 2ga power wire down the frame rail, then up into the car via one of the rubber plug things underneat the rear seat. I carefully drilled a hole in the plug thing so the wire barely fit through, and it was a snug fit (to keep it as sealed as possible, and keep the wire from rubbing against metal. Then it was just running it under the seat, and into the trunk. For you, you could run it down the side by the door sill and then under the seat, or do something like that.

I thought I had a pic of how i ran mine but I can't find it.

Also when buying wire, don't listen to the guys saying "OMG YOU HAVE TO GET THIS WIRE ITS THE ONLY THING TO USE FOR AUDIO!!". Pretty much any wire will work, there's no need to buy the expensive stuff at radio shops. I used to work in an electrical department at a factory, and bought a spool of their 4ga power wire. It works perfectly. The big thing to look for with wire is that the individual copper strands are large. This makes it less flexible, but the larger the individual strand, the more efficient the wire will be. Again, at the level your stereo is at this isn't a big concern, but its another good habit to get.

I'm not firmilar with whats underneat the seats on the supra, but just look for a good body ground. If its got paint on it, sand it down to bare metal.

I'll be out of town for a few weeks, so sorry if I don't reply to any further questions. I'm sure someone else on here would be able to answer your questions. Good luck, let us know how it works out and how it sounds!

 

[thelonerider]

Hmmm, No one mentioned that there may be an issue with using 3.5 speakers... As you mentioned, you needed to turn down the bass on the front speakers to make them sound like they are not trying to destroy themselves... 3.5 speakers are not recommeded to produce bass, so even an amplifier with more power may not solve the sound quality issue.

 

[88mkIIIproject]

For the ground, I used one of the bolts that mounts the black platform in the trunk (the thing the rear wooden deck is hinged to). I just sanded the paint down, and put the ground between the car and the platform, without the rubber spacer that is there initially.

And for the power, I ran mine from the battery through a hole that is near the master cylinders, on the inner fender wall. There is a plug there with a hole that is perfect for the power cable. Then I ran it straight behind the fender and into the door jamb, and through the hole where the harness for PW, PM, and PL runs to the driver's door. Then straight under the carpet, next to the driver's seat, under the rear seats, and through one of the two half-circled holes in the rear hatch carpet. I ran the ground and input wires through the other hole, and I think it looks pretty good.

Let me know if you need any pics, GL!

 

[Figit090]

Thanks guys! just to clarify i'll be placing my amp under the passenger front seat. so i'm going to look for a route on that side of the car. i might go up to the firewall and then over to a hole in the firewall, following the main harness. then i dont know where the hell it goes so hopefully its not too much of a bitch to find the wire as it comes out. then i'll see if i can run it along the door sill and through a hole in the carpet. I will see what's available but i will most likely mount the ground to the seat bolts.

i'm leery putting my amp next to the heater vent but hopefully that doesn't heat it up to bad.

and yes, i was afraid that the 3.5's would need help despite the new amp. I may have to turn the frequency cutoff pretty high to avoid clipping at high volume levels...

later if i keep the car i will install a small powered sub and call it a day. most likely. it all depends on what goes on in my life as far as a daily driver.

basically, i'm making this car as nice as I can and then determining what i want to do. it's either this or my next choice, a MR2 (gas mileage)

the one pic i could benefit from would be the specific path of the battery wire IN the engine bay. it's a hot area with lots of vibration and i don't want to FUBAR the wire. but i think i'll be ok. the supra has always been a learn-as-you-go thing for me so...i'll just have at it and see how i do.

how do you recommend figuring out the length of wire without buying a ton extra and waisting money?

 

[3p141592654]

The signal connections on a stock Toyota head units (< model year 2004) with external amp are all single-ended and should be compatible with most 3rd party amps using RCA inputs.

Since the head unit gets its power from this connector as well, you also need to hook up the power connectors as well (+B, ILL+, ILL-, ACC, GND) and also the ANT+ if you have a power antenna.

I've attached the pinout of the headunit to external amp for 2000-2003 model year Toyota HUs that use the 20 pin connector. To connect to an RCA amp, you would use pins 8, 9, 18, 19 for the center pins and pin 10 for the ground outer shield. I believe you can get these harnesses pre-made, but I always make my own.

 

[Anth505]

Is there any particular reason for keeping the stock HU? I can understand wanting to retain the factory look but other than that?

A new HU won't cost that much and will probably sound better on it's own compared to hooking up your factory deck to an external amp.

3.5 speakers aren't meant to handle bass. I would toss em and replace with 5.25's from a good manufacturer.

I would also suggest that you not try to do the installation yourself. I don't mean to be rude in any way, but you seem new to car audio installation and although it's nice to do things on your own, in this situation it's probably best to let a knowledgeable shop or friend do the work.

If you are determined to do it yourself, do some research before you start.
Learn different wiring techniques, installation techniques and read up on car audio in general. ie speaker sensitivity ratings, the difference between line level and speaker level inputs, etc.

It's alot to take in and I wouldn't play around with your cars wiring until you have a sound understanding of what you are doing.

Just my .02

 

[Figit090]

The signal connections on a stock Toyota head units (< model year 2004) with external amp are all single-ended and should be compatible with most 3rd party amps using RCA inputs.

Since the head unit gets its power from this connector as well, you also need to hook up the power connectors as well (+B, ILL+, ILL-, ACC, GND) and also the ANT+ if you have a power antenna.

I've attached the pinout of the headunit to external amp for 2000-2003 model year Toyota HUs that use the 20 pin connector. To connect to an RCA amp, you would use pins 8, 9, 18, 19 for the center pins and pin 10 for the ground outer shield. I believe you can get these harnesses pre-made, but I always make my own.

Thanks. actually you gave me a pinout before on the headunit i have. the one you just gave me is different and newer, but either way...I dont think I have the time to custom wire that. right now all ineed to do are run wires from the external amp to my kenwood amp, run power, attach a ground (easy) and put my seat back in

Yep...my seat is already out and after vacuuming i'll pop up the carpet and start routing things.

I really appriciate your help, but if the setup i had before will work, i'm going to have to try it first. At least I will have the amp mounted.

Is there any particular reason for keeping the stock HU? I can understand wanting to retain the factory look but other than that?

A new HU won't cost that much and will probably sound better on it's own compared to hooking up your factory deck to an external amp.

3.5 speakers aren't meant to handle bass. I would toss em and replace with 5.25's from a good manufacturer.

I would also suggest that you not try to do the installation yourself. I don't mean to be rude in any way, but you seem new to car audio installation and although it's nice to do things on your own, in this situation it's probably best to let a knowledgeable shop or friend do the work.

If you are determined to do it yourself, do some research before you start.
Learn different wiring techniques, installation techniques and read up on car audio in general. ie speaker sensitivity ratings, the difference between line level and speaker level inputs, etc.

It's alot to take in and I wouldn't play around with your cars wiring until you have a sound understanding of what you are doing.

Just my .02

Stock headunit - Reasons:
- I payed a whopping ONE dollar for it.
- another member said he liked to see people working with OEM looking systems, and I was determined to make it look factory again. I've been living with a hole in my dash for 2 years.
- I like the stock look, and have less to worry about with no aftermarket things peeking out ready for a thief to see.
- I do not want to spend 40-50-80 dollars on a nice headunit when I have a decent one that I discovered I like to use is currently in my hands. You have to understand that this is a low budget project that i intend to look clean and give me sound that is decent. I have been driving my supra for over 2 years without a stereo because I have had other priorities...this is good enough.
- I have underlying plans of selling the car that might come into effect. If i get a stereo that sounds good in the car I have it that much eaiser selling the car without a gaping hole in the dash. Should I have to sell the car it will be that much eaiser and I won't be hitting myself for dropping lots of extra money in only to see it taken away. I dont know if i will sell her though, i hope not.

I'm in school and can't blow lots of money on my car for pleasure. I just spent money on my drumset too so...lots of extra cash is not what I have. (i know...so why did i buy stuff for the drumset? its higher on my priority list and I have reached my feasible spending limit for a while. plus I had no plans on upgrading a stereo i didn't actually HAVE in the car. it felt illogical in my current position.)

I appriciate your comments, and yes you are right. If this was my SURE daily driver for years to come, with no lingering worries about mechanical failure, I would drop at least 100 dollars in a good head unit, high end fronts, a good mid-power amp and a small sub to round it out, but those alternatives are too expensive for me at this time..


I am new to this and to be clear I'm not offended by telling me to research first. its a good idea and good advice. However it doesn't seem that complicated to me and I feel like I know enough to get this done with a little help. I already have my seat out and I understand the basic concepts of sound amplification so i'm not really over my head. I have a manual with this amp and overall this stuff doesn't seem complicated enough to screw up.

For me it's about experimentation and first hand experiance I guess. I've been messing with audio stuff in my home and in music for years and this isn't too much different. Also I don't think I need to worry about the speaker sensitivities at this level, seeing as how you and I both think the OEM head unit won't be that great anyhow.. Don't worry too much, I will take all the help I can get but I'm not worried so you shouldn't be I'll try not to do anything stupid

i know the difference between line level and speaker level ins as well haha

In heed to your reccomendations I will research a bit before actually going out and getting wire and routing things. For now I am going to go shop vac and remove my passenger seat carpet to see what's what. I will take pictures too ...if anyone cares to see my progress.

to clarify my money situation, i am in college and have no job. (but i'm looking for one and applying, dont think i'm a slacker!)

 

[3p141592654]

Makes sense. The reason to not use the speaker level inputs is of course to reduce distortion, but given your goals its probably not an important consideration, and will simplify the installation. In any case, you can always go back and switch to line level inputs if you find distortion a problem with the speaker level inputs.

I am wondering though why you are bothering with the Kenwood amp at all. I doubt you will notice a big difference between it and the stock external amp and its adding extra complexity. I would focus on the speakers, especially the 3.5" front ones, or did you mean 4" which is the stock size.

 

[Figit090]

they are 3.5... I remember looking for the model number and specs a while back.

I was hoping the kenwood amp would add enough power to keep the drivers from flapping around on low wattage. i am thinking before I bolt it all down I should check too see though.

can you give me any tips on how I could "jimmy-rig" this to test it out? i mainly need a good power source from the battery and I can handle all the grounding and wiring myself. I just want to make sure I have a good wire. could I use a speaker wire TEMPORARILY to test it or will the current overload that type of wire?

my dad has lots of extra wire from when he wired our garage power, maybe I can use that? it's solid copper wire designed for 120 AC... i'm not familliar enough with wire properties to tell if that will have the right resistance.

I think that is my next step, I need to test out my idea before i mount this thing. if it doesnt help the speakers I have I will use it to power a small sub instead. I dont know though its kinda trial and error.

in a minute i will have pics of my progress.

 

[Figit090]

Ok my front speakers are like these but a slightly older model, these are rated at 25watts RMS, 70 peak. I'm guessing that the kenwood's normal output of 35 watts would be well suited for these. they aren't designed to go handle below 90Hz though,

I'm hoping that with the amp, they will have better all around sound, i'm not hunting for a ton of bass or even much for that matter, i just dont want the speakers to get harsh at higher volume levels like they seem to be doing now and I want to give the amp i got a while back a try at least.

Here is where I plan to stick the amp, excuse the mess;

Here it's all cleaned up now.

I found an old power cable from the PO's amp, i'll tie the new cable to this and yank it through, re-routing it better than they did - once it gets to the floorboard of course;

I finally did a quick test fit with the amp, FM signal booster, and head unit all tucked in the dash and it just fits perfectly. I am pleased with how it should look once finished!

I'm wondering if my car wasn't once in a minor flood... its got remnants of rust in places i wouldn't expect, not cancer but confusing rust...i'm not even sure what's rusting.;

 

[Dan_Gyoba]

If your aftermarket amp has "high level inputs" these are intended to take a speaker level source and convert it. With these, it's a done deal.

Alternately, you can buy line level adapters. These have wiring pins on one side, and a femalr RCA jack on the other. These are used to convert a speaker level source to a pre-amp source. They're cheap, and work reasonably well.

Neither of these is what I'd consider to be a real high end solution, but both would work just fine, and be at least equal to the factory deck.

Making a wire harness adapter to get rid of the factory amp is a cleaner solution, but it's not really necessary.

 

[thelonerider]

IMHO... I think you are barking up the wrong tree thinking that the Kenwood amp will make the 3.5 speakers sound better. Even though the JBL speakers are spec'd to play down to 90hz, you have to look at what power level this spec was taken at. At mid to high volume, those cones will be traveling way too much (the flapping you were mentioning in a previous post) and will sound like crap. Another indicator is that you are turning down the bass on the head unit.
Another item no one mentioned is the fact that OEM / stock head units are EQ'd to help with their limited power and usually have a far from flat signal. There are aftermarket OEM to external amp connection units that help keep the signal flat. Check out RE-Q and 3Sixty.1 for an explaination on what I am talking about.
3SIXTY allows aftermarket car audio equipment to be integrated into existing OEM environments by utilizing artificial intelligence to automatically correct OEM inadequacies by restoring a flat frequency response.

 

[Figit090]

Thanks, but those links you gave me don't work or go to RF's site. I didn't know the EQ's are changed but that's believeable. Thankfully my head unit has a bass/mid/high EQ i can mod so hopefully that has enough modulation to counteract any funnyness.

as far as the small speakers...yes it's not going to help much, but i just need it to help a little. lol they did allright but they just seem like they could be better off with more power.

OK, well it seems almost to be split 50/50 on what would be worthwhile for me, so I am going to test it out myself. That's the only way I'm going to get settled on this quickly. I won't route or wire anything permanently until i decide firsthand.

BUT I dont think I have a length of large enough gauge power wire.

what is the smallest gauge i can use to temporarily power up my amp? not for long, less than 1 or 2 minutes at a time.
also, i'm not sure where to connect my 'remote on' cable, should I just voltage test for the cable that recieves power in the "ACC" position and splice it in with that one? I found it earlier but didn't record it. shouldnt be too hard...i think thats right.

 

[Anth505]

A fellow drummer!! Believe me, spending $$ on your drums is never a bad thing!

I didn't realize you were trying to do this on a short budget. Also I didn't mean that you didn't understand the difference between line level and speaker level inputs or that you needed to know about speaker sensitivity to do this job, they were just examples. All I meant was to research all the ins and outs of what your doing.

Lonerider is right, the external amp won't help with the sound quality at all. The job of an amplifier is to take the sound from a source unit and make it louder. If the source doesn't produse good sound, the amp won't make it any better.

Your speakers aren't flapping because of low wattage, they're flapping because of too much input. If you are going to keep these speakers Iwoud recommend a passive crossover of at least 100hz to keep the bass out of the speakers.

As said before, the factory amp should be all that's needed to power these. If you want to use the kenwood, bypass the factory amp. Also running speaker level inputs from the factory amp to the kenwood might introduce alot of distortion.

As far as wiring goes for this particular application, you should use 8 gauge all around. Bigger is always better, but 8 gauge will be just fine for this. So, run an 8 gauge from the battery to an inline fuse, then to the amp. 8 gauge ground from amp to chassis. 8 Gauge ground from battery to chassis and 8 gauge + from alternator to battery.

Good luck with the install!

 

[Figit090]

would it be ok to not use an inline fuse for testing?

I'm not even sure what the inline fuse will look like do they stock them at hardware stores? the closest car audio dealio is miles away.

thanks!