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Discussion Starter · #1 · (Edited)
Ok I just want to start off with I've tried searching for an answer to this exact question, while I did get half of the answer I was looking for from a thread a few years ago, I didn't get the exact question as a whole answered. As it may seem obvious from the title, I'm wanting to add my Amp + Sub that I had in my R32 GTR into my WRX. Unfortunately my WRX came with the Harmon Kardon system making researching this slightly more frustrating. After spending days/weeks on researching how to upgrade the sound system on the Harmon Kardon system. I learned a lot, and I think I have a good base knowledge of the system vs the base stereo on these cars. Can someone correct me if I'm wrong here, and drop some knowledge and either recommend a change or just correct my misinfo. Ty.

So far I've found out the Harmon Kardon system in the VA WRX changes/varies depending on build year. BUT I'm not sure if ALL year Harmon Kardon systems are like this, or if it's just the 2018+ but IIRC the lines coming from the Headunit are Speaker Level(high level) going into the HK amp? I know sounds redundant, and stupid which is why this confused an Audio noob like me who didn't even know what a low level vs. high level (speaker level) was. lmao. Either way, it seems if I want to add a sub amp/subwoofer to this system I'm gonna have to pull a speaker level line (tap at factory woofer) and run those into my amp? Which would require the use of a L2Ci or something similar. I noticed my Memphis amp has support for both low level and high level inputs, which is apparently called a "Variable amp"?? I couldn't find anything about wiring into one of these amps, but since my amp has this feature, I wouldn't need any LOC converter, correct? I can literally just tap the factory subwoofer wires into my Memphis amp, and done-zo?? If so that makes this a whole lot easier, because I wont have to worry about powering the L2Ci, and it's something easy enough that I'm confident doing myself. Unless there's some significant downgrade going this route, how come this isn't mentioned or talked about? At least I couldn't find any threads/posts talking about it. FYI I'm not too concerned if doing this is going to have slightly worse audio quality, as long as it's not a significant difference were going the L2Ci/LOC route is better. The Memphis amp I have is the SRX series, going to a Mojo Mini 6.5". I had to get the 6.5" because it's all that would fit in the back of the skyline that this shop had. I'm not sure if you guys have heard how the Mojo Mini are, but I was blown away at how strong a tiny little 6.5" could be. I don't know my car audio that well, so to my noobie ears it sounded as loud and thumpy as a 12". Would the 8" be overkill? I'm close to the owner of this shop, so I can probably talk to him about trading the 6.5" for an 8". Could this 6.5" or the 8" be mounted in the rear deck where the factory HK subwoofer is???


As for the dash/door speakers, the Harmon Kardon has near full range speakers in the dash correct? Where as the base has mid ranges in the dash? I'd eventually like to replace all speakers, and head unit and just get rid of the HK system all together (don't care for factory nav and making it so bluetooth calls come through the front speakers. I replaced the dash speakers with Infinity Reference 3.5" coaxial full range speakers, front doors are still factory rn. Should I find a pair of component/mid-range 6.5" woofers for the doors? Or will adding coaxials in the front doors be okay as well?

But yeah the thing about the variable amp, was my main question that I need answered. If that's something I can do, then I'm ordering Thanks in advanced!

EDIT: Does anyone know where to get the high level harness for this amp?? Do I even need it? Can I just wire it directly onto the connection/header?
 

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Hi, fellow WRX owner here. Ok let's go over this;

1 yes you can tap off the factory sub and go straight into your amp. Quick and easy as it's already crossed over etc by the HK amp

2 yes the front channels go from the radio to the StarLink module DVD then to HK amp

3. No do not install any sub in the rear deck, they rattle like crazy, get a small box to put it in or even a corner fiberglass enclosure

4 dash speakers from factory are "middlers" but the upgrade from kicker are actual tweeters. If you've got a 3.5"in there already then you can leave it and simply replace the door speakers down the line

5 no do not put coaxial speakers in the front doors as it'll bring your sound down

6 no an 8"isn't overkill in any way

7 replacing factory head unit is your best option to get the best possible sound in these cars as the factory radios aren't the best sound quality wise. Either a good quality aftermarket (Kenwood Pioneer Sony Alpine etc) or a good Android radio like a Joying.

If you've got questions feel free to ask, glad to help. If you like I've got a build log on mine if you want some ideas.


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Discussion Starter · #4 ·
Hi, fellow WRX owner here. Ok let's go over this;

1 yes you can tap off the factory sub and go straight into your amp. Quick and easy as it's already crossed over etc by the HK amp

2 yes the front channels go from the radio to the StarLink module DVD then to HK amp

3. No do not install any sub in the rear deck, they rattle like crazy, get a small box to put it in or even a corner fiberglass enclosure

4 dash speakers from factory are "middlers" but the upgrade from kicker are actual tweeters. If you've got a 3.5"in there already then you can leave it and simply replace the door speakers down the line

5 no do not put coaxial speakers in the front doors as it'll bring your sound down

6 no an 8"isn't overkill in any way

7 replacing factory head unit is your best option to get the best possible sound in these cars as the factory radios aren't the best sound quality wise. Either a good quality aftermarket (Kenwood Pioneer Sony Alpine etc) or a good Android radio like a Joying.

If you've got questions feel free to ask, glad to help. If you like I've got a build log on mine if you want some ideas.


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Ahh your name looks familiar! I think I read a thread you either replied in or started and actually looked through one of your builds. You’re the guy who mounted the amp on the black super short step stool from ikea looking thing in the trunk right? Sorry if you’re not. I’ve read so many threads on this, I just recognize the name. Haha.

as far as door speakers, then I should just replace with component 6.5”? Or I think they’re also called mid-range woofers? Not sure if there’s a difference but seems most if not all components come with tweeters(which I don’t need). These Infinity Reference 3.5” came with I think 250uF or 270uF bass blockers. Someone in a different thread said they didn’t add the bass blockers since it’s already crossed by the HK amp? I assume when I do eventually replace the HU and get an amp I’ll need to add some sort of bass blocker since I won’t be utilizing the stock HK amp at that point?? Also, if I don’t care for the STARLINK system can I rip that lil fella out when I replace HU?? Or is it vital for system function(whole car)?? I could careless about the features about it calling Subaru if I’m in an accident or whatever.

I’ll just keep the lil 6.5” Mini Mojo in its box it came in and trade for the 8” if I feel it’s necessary then. Should I keep the stock woofer mounted(not plugged in) or take it out? Just curious if the hole left behind on the rear deck will benefit or not sound wise.
 

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Hi, no my amps are in the trunk on a board over the spare, LOL. Door speakers wise it depends on your budget, there are numerous " a la carte" options for you. CDT Audio ES-6 line is quite good, Audio frog GS60 is what I currently have. You could always buy a regular component set and not use the tweeter or try both your current and the tweeter to see which you prefer. You definitely want a mid bass not a midrange speaker in this application. I would definitely install the bass blocker, better safe than sorry. I'm attaching some diagrams to help you a bit, I hope LOL. Yes it looks like the factory amp does have the speakers crossed over but I can't be 100% about that. If you are going to replace the radio completely then yes i would say you can eliminate the telematics. For these questions I really would defer to AutoHarnessHouse, call them and ask they are great. By all means keep the sub you have and try it out nothing to loose there. I've linked my build below for you. Let me know if you need anything

 

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Discussion Starter · #7 ·
Ooo thank you!! Your help has been awesome! So one last question… for now… I think….. if I get stuck. I’ll be back heh. I think this is the only question I had. I thought I had a different question to ask but apparently I forgot or it wasn’t important enough. So on my Memphis SRX amp, the high level connector doesn’t seem like it’s anything special. Long story short I lost that connector but judging by my limited knowledge of electronics. It seems like I could just solder on wire extensions instead of having to source a replacement cable? And then just tap/solder the wires accordingly from the Subwoofer correct?? This is what the high level connector looks like. I’ve seen some on eBay for sale, and I’m not too worried about making a semi permanent change like soldering leads off this connector. If I shrink wrap each connector after soldering. I technically should be okay right?? And I assume the leads from the OEM HK sub has a ground I would tap too? Or does the ground connect to chassis?
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Yes you can do that just be sure you get the polarities correct with the center pin of the RCA being positive. No, do not ground anything RCA related. In other words the positive lead from the sub connector to the center pin wire of the rca connector and the negative to the shield or jacket of the RCA connector.

As far as your amp being able to handle the signal, that's the real question. Looking at the picture of the amp it's the SRX250.1? If it is you have a max of 6 volts it can handle on the RCA connectors. The easiest thing i would recommend is to use a voltmeter and measure the voltage going into the subwoofer. Set the voltmeter to AC voltage and do it with the speaker disconnected. If the voltage is less than or in the close neighborhood you're good. If it's much higher you can over drive the amp. Then adjust the gain of the amp to it's best setting. Do you know how to set the gain on your amp?

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Discussion Starter · #9 · (Edited)
I have the srx500d. Not sure if there’s much of a difference. But RCA?? I’m confused now. Haha. Is high level(speaker line) RCA as well? I thought only Low Level was RCA? Taking a look at the OEM Factory HK Subwoofer, it looks like it has a seperate plug with one black wire going to it. So is that not ground then?? Am I missing something here?? So do I have to use RCA?? I thought I was able to just unplug the OEM HK Subwoofer, tap the cables/wires going to the stock sub and just match the polarity to the high level connection on the amp? The subwoofer I’m putting in is DVC as well (OEM is DVC right?) so wiring wise should be straight forward. But clarity on the RCA would be appreciated. I was under the impression I could grab any speaker level wires and just use the high level connection and it would take care of the rest.

as far as the gain question. I remember doing it a long time ago on my 350z, but that was years ago. I know where theknob is. But I don’t remember how to properly set it up. Although it should’ve been setup from being used in the skyline

Edit: taking a break from ripping the amp power wires/cables from the GTR. I remembered the other question. I know you mentioned the 3.5” Infinity Reference Full Range speakers I got to replace the dash speakers will be fine. Do you think I’m better off keeping the 3.5” full range coaxial, or should I just return it and get a replacement midrange for the dash?? Or do I just return it for a set of components and put tweeters in the dash?? I’m kind of liking the idea of the component route, that way I don’t have to shell out a kidney for a decent 6.5” midbass. But if you think the best sound would be midrange dash and midbass woofers in the door I don’t mind spending the extra cash. HU and maybe amp for the rest of the speakers so I can rip out anything and all HK from the car will be next audio mod.
 

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Dude I'm sorry I caused confusion unnecessarily! I would definitely advise you to get a replacement plug, I assume by "I could just solder on wire extensions instead of having to source a replacement cable" you mean soldering directly onto the amp connector then NO don't do that, get the connector. But you can do what I mentioned above. Get an RCA cable and cut off the tips with enough length to work with and use that in to the low level inputs instead. Yes, each channel would correspond to L and R from each of the voice coils (one for L and one for R) to use as your inputs. Gain adjustment is a relatively simple math problem (Voltage = square root of watts x ohms) For example, a 500W RMS amplifier at 2 Ohms would configure like this: 500W RMS X 2 Ohms = 1000W . I copied that from Sonic Electronics so I can't take credit. How to Adjust Amplifier Gains Using a Digital Multi-Meter - Sonic Electronix Learning Center and Blog

I would keep the speakers (REF3022 ?) you've got now and try them out and only if you aren't happy then change something. UNLESS you haven't used them yet, if you haven't then yes replace them with a component set as then you'd have a complete front upgrade. What mid bass were you looking into?
 

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Discussion Starter · #11 ·
So what I’m understanding is this high level input is just a built in LOC? So I assume the stock harness for this would have high level input cables, then rca output cables?? Idk how the amp would do that. Looks like it’s literally just an input (like low level). I think we both maybe a little confused. Hahaha. Ok. So here is a replacement high level connector that’s available new on eBay, and this is why I asked if just soldering leads onto the connector would work, because all this connector does, is what I initially asked, but instead of solder it uses the plastic connector.
Wood Amber Electrical wiring Cable Wire


and here’s what it looks like amp side.
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Musical instrument accessory Musical instrument Electronic instrument Electronic component Electronic engineering


hopefully these pics give some reference and why I’m so confused on the RCA/low level you mention. I’m not using a LOC or device like an L2Ci. Since my amp has this high level input I was curious if I can just tap the subwoofer directly into the high level input on the amp, without having to purchase an LOC. However, if the sound quality is going to be noticeably bad vs using a LOC…. Would you recommend L2Ci orJL Audio makes pretty much the exact same thing, and for the same price as well. But everything says my initial plan “should” work right? Unless I completely missed your explanation on the whole RCA/low level part?? If that’s the case I’m still lost on where the RCA would even come from. All the OEM wiring in the Subaru has no RCA correct? It’s all typical proprietary OEM clips?
 

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Correct, your amp looks like it has a built in LOC so no you do not need one. If the plug pictured is the correct one for your amp then yes take and solder each voice coil output to a channel on that connector and you'll have L and R into the high level input of your amp. I see 5 pins on that connector with the center one being a ground. I don't see in the owners manual (on Crutchfield or Memphis websites) an option for the high level input or how to use that ground pin/wire. I would not use the pin unless it has to be used, maybe contact Memphis Audio to be sure. As for whether to use and LOC or not I would definitely say no don't use one. If your amp already has one take advantage of it and use the built in one. Sound quality won't really matter as its a sub amp and in those low notes it wont make much of a difference. Correct, factory uses no RCA anywhere. Just use the plug and the high level inputs the amp has and you should be good.

Don't wanna ask why the amp is wet but please be sure wherever you mount it that it wont get wet!
 

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Discussion Starter · #13 ·
Oh I had the garage door open, and it was close by the entrance when a random Texas rain monsoon swept by. I made sure it was dry before supplying it any sort of live wire. So yeah, I soldered on some leads and used those quick connect leads, because some dude posted on Nasioc that the leads connecting into the sub were wired backwards or labeled backwards from the factory. Anyways. Going off what the post said and multimeter confirming the post that they indeed were labeled wrong or wired wrong. So I wired them to the amp backwards. But the post was wrong. Despite the multimeter confirming that it’s wired or labeled backwards, it’s actually correct from factory(who woulda thunk right?)

after realizing how quite the sub was and me remembering that the sub was never this quite. I decided to wire them to how it was wired from factory. And whadda ya know? I never knew a fucking 6.5” sub could thump that loud. Lmao. I didn’t blow the sub. Was no where near its limit. Just took me by surprise when I turned the radio on. I’ve had an 8” sub in my 350z before and it could never get as loud and thump as heavy as this little 6.5”. Is size irrelevant to how hard a sub can go boom boom??? Bigger size just mean it’s ability to hit lower frequencies, but how hard and loud a sub can get is the size irrelevant?? So for an example, a 12” sub vs this 6.5” sub both can achieve the same amount of thump and overall loudness. It’s just the 12” can hit lower frequencies?? Or is the Memphis Mini Mojo really that good?? Anyways. Happy to say. The LOC built in the amp works great, and soldering worked. Thank you for all the input and help!!! Couldn’t have done it without ya!! Truly appreciated! I don’t think I answered your question about midwoofers. Uhhh I’m not sure. Some songs the OEM front door woofers seem plenty, but others it sounds like they’re at their limit? Is there any reason you can think of why the door speakers got louder after the amp install??? Does the LPF applied to the subwoofer being applied to the door speakers as well?? IIRC these speaker level wires that I tapped into are coming straight from the headunit into the factory HK amp. yes I know that sounds stupid but apparently that’s how these HK systems are wired. The speaker wires from the HU are all speaker level, and then the HK amp then sends speaker level back to the HU with crossovers and such. Iirc that’s how it’s wired. And the head unit tells the HK amp to go up or down in volume. Idk.It may just be placebo, but I swear the door woofers got louder. Ugh sorry. Went on an ADHD tangent. LOL. What’s a good budget friendly midwoofer/midbass speaker you recommend?? Also are 6x9’s better vs 6.5??

I’m considering returning the Infinity Reference 3.5” REF3032 speakers. And getting a decent component set. But I’m hearing mixed reviews on using tweeters in the dash with the stock HK AMP. But I’ve already took a dremal to the stock dash speaker location. So I think it’s a little late to put anything smaller in. LOL.
 

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Pretty much as in car engines "there's no replacement for displacement" so yes a 12 can normally put it more "sounds"than a 6.5" . The difference is that that 6.5" was designed with a lot of excursion to make up with the difference. Take a 12" with the same design parameters and there'd be no comparison. BUT you've gotten the sound and feeling you want so that's all that reality matters. Congrats!!!

As for the door speakers and their "increased sound" believe it or not that's most likely due to the sub you added. Just because a sub is set to say 80hz and below it DOESN'T mean it's not producing ANY sound above that crossover point. Even at the lower output due to the crossover point, the added sound from the sub beefs up the midbass sound.

Unfortunately 6x9 speakers will not work in our cars. A 6.5" is the best we can do. How and what did you cut out of the dash location, send a pic. To be honest you're probably better off with e 6.5" and a wideband in the dash location. But that'd be after you decide to ditch the factory system. Have you tried it with the stock speaker back in place? You might just be surprised and like it. Send me a picture of what you cut up to see what we can come up with.

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Discussion Starter · #15 ·
So would the LPF and Subsonic Filter I have set on my amp affect the door speakers too then?? I notice some drives they don’t function at all, but other drives they do function. I guess I haven’t tried if they kick on with certain songs that have a bass frequency they kick in on. On the Amp I have LPF set to around 120hz and Subsonic Filter I think I have it set to 35hz?? Whatever the middle setting is. As for the dash I guess “cut up” is a bad term to use on my part. I should’ve said I just took a dremal and widened the hole so the 3.5” would fit snug. The original screw holes are still there for the original dash speakers.

the bass blockers I added for the 3.5” wouldn’t affect the door speakers would they?? I’m just curious what’s causing them to cut in and out. I’ll try the OEM speakers when I get home.

Edit: I should add that when they do cut out the dash speakers become very very high heavy. Like someone cranked the treble all the way. So I basically have no mid sound. Only bass from sub and highs from the 3.5”. Happens quite frequently as well.
 
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