Audio Install in the STI, Completed!

Discussion in 'Electrical & Stereo' started by mcglsr2, Sep 8, 2016.

  1. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Hey everyone, decided to do an update to the audio in my '11 STI. I already have an aftermarket head unit in the car (I'm pretty sure I had a thread on this but I can't find it) and I currently have an old Rockford Fosgate amp and an old Rockford Fosgate Punch P2 10" sub. Otherwise, stock speakers. Typically I just install an amp (either bridged or a mono) to run a sub and run the other speakers off the head unit. Lately though, thinking about a potential "new to me" car, I got the itch to update the STI. I decided to see what running the other speakers off an amp was like.

    I did some looking around to see what's out there as it's been quite a while. I'm not excited about running 2 amps but what else could I do? Ah ha! I see now there are 5-channel amps. Two amps built into the same chassis: a 4-channel and a mono. Well. That's just super.

    So I picked out my amp, picked out my new speakers, all the additional stuffs I will need for the install, and ordered it all up. This post will document my install because hey, why not. Some might find it interesting.

    On to the audio bits!

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    Alright, so what do we have here...
    • Rockford Fosgate Punch P1000X5 Amplifier
    • Polk Audio DXi6501 6.5" Component (for the front door)
    • Polk Audio DXi651 6.5" Coaxials (for the rear door)
    • car-speaker-adapters.com speaker brackets, STI specific, front and rear
    • Rockford Fosgate RFK4 amp install kit (4 AWG) with a 150 Amp ANL fuse
    • Rockford Fosgate RFIT6 RCA cables, 6" length (3 sets: Front, Rear, Sub)
    • XTC speaker baffles, 2 for the front door, 2 for the rear
    • Stinger 9-wire speed cable, 20'
    • Stinger PRO 14 AWG speaker wire, 15' (for the sub)
    • Speaker connector adapters, supposedly for the STI
    • Molex 2-pin connectors, for the tweeters


    Front Door Speakers

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    Rear Door Speakers

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    Not really much to say about these guys. I like Polk Audio speakers. I expect these to sound pretty good. The front door speakers are 100 Watts RMS, and the rears are 60 Watts RMS.


    Speaker Brackets

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    Here's a close up of the rear speaker mounted in the adapter (with the XTC baffle trimmed and installed). Supposedly, the STI has a non-standard mounting pattern for their speakers. The Polk's came with adapter brackets, but they require drilling a hole. I ran across the car-speaker-adapters looking up stuff for that other car, and decided to give them a try. They are supposed to be sized exactly to the STI and require no modifications to fit - they "should" screw right in. The rears also space the speaker out a bit to ensure there's no interference with the window. We'll see how these work out. The only downside to them so far is the cost - they are a bit overpriced IMO (however, if you document your install with pics and submit them to the company, they will refund 50% of the purchase price - which I will be doing).

    Also, with these guys, they supply machine screws to attach the speaker. They want you to use super glue with the screws to prevent them from backing out. I opted to use wood screws instead, thinking that the larger threads will engage and hold the PVC better than the machine screws supplied. We'll see...

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    Update: I ended up not using those screws in the install. They were too short. Instead, I used the black course thread screws that came with the speakers (as part of the installation bits). These worked perfectly, and you can see them in the later install pics - the screws are black instead of these silver ones. Also, I send car-speaker-adapters.com the pics and Michael (the owner, I'm assuming) gave me a 50% refund, true to his word on his website. That makes these actually reasonably priced. So I totally recommend these guys - just be sure to take enough good pics so you can get the refund.


    Rest Of the Stuff

    The speaker baffles and speaker connectors:

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    RF RFIT6 RCA cables:

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    RF 4 AWG kit (power cable, ground, and remote cable only) with Lightning Audio in-line ANL fuse holder (150 Amp fuse):

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    Stinger 9-wire speed cable, 14 AWG speaker cable and Molex connectors:

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    So my plans for wiring up the door speakers: simply put, I'm using the OEM wires. The research I've done indicates that at Watts of around 75 RMS and below, the OEM wire is just fine. At Watts over that, larger gauge wire should be used. As it happens, my new amp puts out 75 Watts x 4 RMS (at 4 Ohms) - so OEM wire it is. Okay, with that out of the way, the next question is how to hook up the amp to the stock OEM wires. Enter the speed wire. Essentially, it's 9 wires bound up in a single sheath. 8 of them are for the 4 speakers (pos and neg), and the 9th is for the remote turn-on wire. One runs the speed wire from the amp up to the head unit. At the head unit, I will cut the speaker wires that connect the head unit to the OEM wires, and instead connect the speed wire to the OEM wires. Thus, my amp now drives my new speakers via the OEM wires, and I do not have to run wires through the car (apart from the speed wire).


    The Amp

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    Damn. This thing is robust. The whole thing is basically an aluminum block, with amp guts nestled inside it. It's rated at 1000 Watts, and as per the course for Rockford Fosgate, all their amps are under-rated (or over-engineered, depending on how you look at it). It's rated for 1000 Watts total, but in testing is good for 1337 Watts. Their amps always perform better than what they are rated at.

    I will be running my door speakers at 4 Ohms, and will eventually run a 2 Ohm 10" sub (though for now, I will be keeping my old 10" RF Punch P2, which is 4 Ohms). The 4-channel portion of the amp will thus run at 75 Watts RMS x 4, and the mono amp will be at 150 Watts RMS x 1 at 4 Ohm (but will be 300 Watts RMS x 1 at 2 Ohms when I get a new sub). This amp also has built in clipping detection that looks pretty sweet. Looking forward to that.

    Update: I ended up switching to a new 10" 2 Ohm right away. This amp only pushes like 150 Watts at 4 Ohms - the door speakers essentially drowned out the sub. It was like there wasn't even a sub, way under-powered. So I ordered a new sub and enclosure the next day. At 2 Ohms, 300 Watts from the amp should plenty. Oh and the clipping detection is awesome. Literally takes all the guesswork out. Technically, you can tune by ear - play the test tone and slowly turn up the gain until you hear the pitch change. It does work. You can do this. Or...even easier. Turn up the gain until the light turns blue. Keep turning...once the light turns red, turn it back a bit to blue and you are done. It took me literally 10 seconds to adjust (correctly!) the gain.


    Super Big Question: Can My Car (Alternator) Handle My Amp?

    So this was the cause for some consternation initially. I don't really want to install a new alternator. And I don't want my headlights dimming on hard hits. Luckily for me, I don't play my music that loud. So I'm not too worried about that. But I am worried about prematurely killing my battery and alternator. So the question of the day for me was: can my car in its current form handle my new amp? I arrived at an answer of yes (obviously, as I bought it) - and here's how I did it.

    I did some research, and found this gem at Crutchfield. It's sort of quick and dirty, but I do so trust those guys over at Crutchfield. The general thinking is that a car will use some portion of the alternator output - but not all of it. What's left over is available for other electrical loads (such as an amp). To find the "left over" available with your alternator: take your total Amps that the alt is rated at, assume 60% will be used by the car electronics, which means you have 40% to play with... (Warning, colors in-coming! Color-coding used to (hopefully) make it easier to follow the calculations):

    1.) Alternator Amps * .4 = Available Amps
    So, for me: I've got a 90 Amp alt, which means 90 * .4 = 36 Amps. Therefore I've got about 36 Amps to play with.



    Next, figure out the draw your new amplifier(s) will make on your alt. The start to this is calculating the total Watts RMS your amplifier(s) will produce.

    2.) Number of Channels * Watts RMS (at the Ohm for the speakers) (+ SUM this up for each amplifier installed) = Total Watts RMS of Amplifier
    So, for me: I'm running 4 Ohm speakers in the doors, 4 channels * 75 Watts RMS = 300 Watts; but I've also got the Mono amp, and I intended on running that with a 2 Ohm sub, so that's 1 channel * 300 Watts = 300 Watts. Then sum up all the "amplifiers", 300 + 300 = 600 Watts total.



    Amplifiers, by their nature, are not efficient. Which is too bad. But needs to be accounted for. Being conservative, assume 50% efficiency. This needs to be accounted for in the total wattage.

    3.) Total Watts RMS of Amplifier * 2 = Actual Total Watts RMS of Amplifier
    So, for me: 600 Watts * 2 = 1200 Watts. What this means is that the amplifier(s) is actually working at 1200 Watts to produce 600 Watts. This is because of the 50% efficiency. 50% efficiency is just a rule of thumb - Mono amps are actually pretty efficient, like 80% or so, but to be safe for your estimates, stay with 50%.



    To calculate the amp draw this Wattage will require, divide the Actual Total Watts RMS by the voltage of the car electrics. Which is typically around 13.8 Volts.

    4.) Actual Total Watts RMS of Amplifier / 13.8 Volts = Amp Draw of Amplifier
    So, for me: 1200 Watts / 13.8 = ~87 Amps.



    But wait, this is way more than I have available at my alternator. Well. The average music signal only requires about a third of the total Watts at full volume (where a sine wave test tone will use the full amount - so careful there when using test tones to configure your system). In other words, playing music at full volume will take about 1/3 of the power.

    5.) Amp Draw of Amplifier * 1/3 = Expected Amp Draw of Amplifier
    So, for me: 87 Amps * 1/3 = 29 Amps.



    Lastly, compare the Amps required to that of the extra provided by the alternator...

    6.) Expected Amp Draw of Amplifier < Available Amps = All Good!!
    So, for me: 29 < 36. This means, at full volume, my alternator should be able to handle the load of the amplifier. And for me, I rarely (like actually never) play my music at full volume, so my Amp draw will actually be a little less. All is good!!



    If your Expected Amp Draw of Amplifier is larger than your Available Amps, then either buy and install a larger alternator, or down-size your amplifier(s). Thanks Crutchfield! So I followed this thinking. Maybe, after the install, I'll discover this is all rubbish. At which point, I'll let you guys know. But like I said, I tend to trust the findings of Crutchfield, so I'm not sweating it right now.

    And since this is my DD, and the Mustang is being temperamental right now, I shall wait for the weekend to do the install. More to come!!!


    UPDATE: okay, so I got home late from work tonight. My new sub enclosure was waiting for me. I pulled the old one out, installed the new sub in the new enclosure, put it in the car. Adjusted the amp accordingly, and bob's your uncle. For me, it sounds fantastic. While the stock OEM speakers are pretty good...this is better. Without a doubt. It sounds really good, very "powerful" at only half volume. If I turn it up, it hurts my ears before it really starts to distort. Also, no dimming lights or anything at the volume I listen at. And....no dimming at a volume that starts to hurts my ears. This while idling in the garage. So the alternator in the car can certainly handle what I'm running right now. Granted, it should only be about 600 Watts and not the full 1000 Watts the amp is rated at - perhaps at full Wattage my car would dim. But where I am...it sounds great and doesn't seem to cause any electrical issues!
     
  2. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Alright, got to it last weekend. Took much longer than I anticipated. Anyhoo, I started on the door speakers first. These guys were the factory speakers...and I must say, I'm not entirely sure I should have replaced them. For once, they are actually quality looking speakers. Not paper cones. Looks like some sort of kevlar weave. The car has tweeters in the sail panel behind the mirrors, speakers in the lower front doors, and speakers in the lower rear doors. All door speakers have tweeters in them, in addition to tweeters up in the sail panels. I'll post up some pics of these guys as we go.

    Here's the car in the garage, getting ready for the "tear down:"

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    Front Doors First

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    Stock speakers out, new ones going in. To get the new ones to fit, I used the adapters from car-speaker-adapters.com. In summary, they worked quite well. No drilling into my door required.

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    Replacing the tweeters - the stock one is on the left, new on the right. Clearly, the new one is a bit larger:

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    ...which required me to modify the stock tweeter locations (you can see the tweeters under the mounting bracket:

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    I added on the Molex connector to the tweeter so I can remove it (I guess if I need to):

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    Installing the crossover:

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    Fitting up the speaker baffles...

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    And finished the install:

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    Stock Speaker Reference

    Here's some close-ups of the stock speakers:

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    As you can see - the speakers are actually not too bad looking. The stockers are 4 Ohms, looks like an RMS of 20 Watts, with a max of 40 Watts. So what my new speakers have over these (besides debatable "quality" as these look pretty good) is that they can handle much more power, and have a quite high sensitivity, so theoretically they will sound better. Though after seeing these stockers, I'm not so sure I will be able to hear the difference in quality. At any rate, if I tried to run these off my amp, they would have blown out at some point as the amp pushes 75 Watts RMS (even the "entry" version of the amp pushes 50 Watts RMS - over the max of these speakers).

    Also note the suspended tweeter, rather than mounted on a shaft in the middle of the cone. I would imagine this allows the cone to move better, and thus might actually be a better design than a typical 2-way/coaxial speaker (like my rears) - but I can't say for sure. The bracket that suspends the tweeter also blocks some of the cone, so maybe it's a 6-of-one, half-dozen-of-another situation, and ends up being a wash.
     
  3. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Moving On To The Rear

    The rears are pretty much the same as the front - a little easier though as the rears are 2-way and not components, so no separate tweeters to install...

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    Stockers out, new ones going in (also used the speaker adapter brackets here as well - again, no drilling in the door required):

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    Installing the baffles...

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    And wrapping it up:

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    And that's it for the rears!
     
  4. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Amp Install and Cabling

    Alright, so here's what was in there before, notice the awesome job of wiring (and by awesome, I mean quick and dirty):

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    Took the trims off, the little red wire feeds power to the backup camera - I had just sort of tucked it before, decided it was time to route it properly along with the rest of new amp cables:

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    Routed under the sill, along with the power cable (more on the power cable in a bit):

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    There's a stock ground location under the seat that I ended up using:

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    Head Unit

    Removing the head unit, with current wires:

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    Removed the bits I didn't need, and added in the ones I did (the speed wire, and RCA cables):

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    I severed the speaker connections in the harness between the OEM wiring and aftermarket head unit, and spliced them in to the speed wire that runs to the amp:

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    The speed wire and RCA's are run down behind the radio and under the center console (and then down the side of the seat underneath the carpet where it pops out to the amp):

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    Power Cable

    Power cable at the battery, with the terminal cover modified to allow the amp cable to pass through and still fit on the terminal:

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    The power cable then runs down inside the fender, and inside the splash guard there (I had to remove some body panel bits to get access behind the splash guard - please also ignore super dirty whee;s :( )

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    There's a rubber grommet covered by the splash guard that already has a cable bundle going through - I poked a hole and ran the amp power cable through it. This is where it comes through in the inside, across the firewall behind the pedal box area, and behind the center console over to the passenger side:

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    And the amp:

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    The cables coming out of the carpet are the speed wire (blue cable sheath), ground cable (black cable without split loom), power cable (red cable with split loom), black speaker wire for the sub to the trunk, and 3 sets of RCA cables.

    Tucked under the seat (without the seat installed obviously):

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    And with the seat installed:

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    And all done, everything back together!

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    Update: I was thinking I was going to keep my old sub. Well, changed my mind. This amplifier does not push enough Watts to a 4 Ohm sub. It's drowned out by the door speakers. So I got a 2 Ohm sub and box, waiting for it to arrive (the amp will push 300 Watts to this sub, which should be more than enough; 4 Ohms is 150 Watts).
     
  5. g36 monkey

    g36 monkey Moderator Staff SN95 Supporter

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    woo!
     
  6. Tally_4.6

    Tally_4.6 Well-Known Member

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    Ride over when you're done.

    Wait, that'll never happen.
     
  7. g36 monkey

    g36 monkey Moderator Staff SN95 Supporter

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    Yea for real, he didn't come get involved in man day the other day
     
  8. Tally_4.6

    Tally_4.6 Well-Known Member

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    Hell no he didn't.

    Sent from my SM-G920V using Tapatalk
     
  9. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Wait, wait. What's this man day you speak of? And why wasn't I involved?
     
  10. ttocs

    ttocs Legend

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    all those amplifier calculations from watts/amps, just look at the fuse rating on the amp and it will tell you what that amp can draw. Amp ratings are all over the place and its the best way.
     
  11. g36 monkey

    g36 monkey Moderator Staff SN95 Supporter

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    We had a man day, and you missed it. I had to teach ol boy's room mate how to buff a car, for the second time lol.
     
  12. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Updated all sections - install done!
     
  13. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Yah, I don't agree with that method. Sure, the fuse tells you what the amp can draw. But let's be honest here - I'm not running a 150 Amp alternator. Shoot, even on a less powerful system (which I know works on the car) at 60 Amps fuse - that's still more than half of my stock alternator. So, if the fuse rating is the way to go, then my lights should have been dimming and I should have had electrical problems. But I had none of that. Which tells me the fuse rating is not the whole story. And in fact, fuses aren't the whole story. They are there simply to protect components, and are an indicator, actually, of MORE than what the unit can draw. No - while I agree that the fuse rating is a little more than the max the amp can draw, and in a perfect world one would size the alternator to provide everything the amp could possibly ask for - the reality is that the amp, while playing music at normal to moderate levels (which is what I listen at) is far, far less than the max draw the amp could potentially make on the system. So: to be absolutely covered in all situations, sure - use the fuse rating. For normal situations, use the calculations. Now, if this was a competition car, and was going to sit in a show spot and crank the music as loud as the head unit will go - then yah, fuse rating all the way. But that's just not how I listen to music. Furthermore, the fuse rating is spec'd to the max draw the amp will make - meaning running the lowest possible impedance speakers.

    If I go by the fuse rating alone, that means the biggest amp I could "safely" run on my stock alternator would use a 30 Amp fuse. That's maybe a mono pushing 200 Watts. If that. And I know the car can support larger than that.

    Why I was no has invite!? When's the next one? I am there my dudes!
     
  14. g36 monkey

    g36 monkey Moderator Staff SN95 Supporter

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    I was pretty sure he texted you, and you were unavailable or something. And you also texted a novel. You type a lot lol. <3
     
  15. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Well I'm wordy - that's what I do! Damn, maybe I did have something going on then. I don't remember. WHEN'S THE NEXT ONE!
     
  16. g36 monkey

    g36 monkey Moderator Staff SN95 Supporter

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    It was spur of the moment, we'll try to include you next time lol. My, uh, work car, needs a detailing day lol
     
  17. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Lol, as do my cars. I have this buffer sitting in a box that I haven't used yet, and would like to very much. I've been waiting to get the garage clear so I can do it in the garage and not in the sun, but I don't mind driving someplace and meeting up with you guys and have a day of it. I can bring my stuffs with me. I have a bunch of Chemical Guys stuff. Let me knowwwwwwww!
     
  18. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Update! (I also updated the OP). New sub installed. 2 Ohm. Which means the amp should be pushing about 300 Watts to it. It sounds great - super balanced with the rest of the system. I'm not an audio expert. And I'm sure there's things I could do to make it sound even better, if I knew what I was doing. But as it stands, to me and my novice ears, I think it sounds really, really good. Super pumped. And no dimming. I sat there, idling in the garage, with the headlights on, playing some bass heavy stuff at a (if I'm being honest) too loud volume - and no dimming. No issues. Oh, I had the A/C running too.

    This, to me, means that I can trust in the calculation that I did in the original post. It seems to have worked for me. I will be doing another audio install in a new-to-me truck in a couple months - I will follow the same calculation and size my system accordingly - and document it here in a build thread ;)
     
  19. Tally_4.6

    Tally_4.6 Well-Known Member

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    You responded like 4 hours later saying you were sick, so i cut you a break.

    lol, i only live 10 minutes away
     
  20. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Lol, oh yah. I totally was too. I got like half the people in my office sick. At least, they blamed me. I was pretty miserable. I'm tots down for the next one. And seriously, I need to come over or something. Ugh.