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After some trial and error, I’ve finally landed on a method to transform our decent subwoofer into a mini monster. Here’s the breakdown of work and parts required:

1- Remove sub enclosure.
2- Remove stock DVC sub.
3- Cut and fit Resonix CLD sound deadener to every flat surface inside the enclosure.
4- Cut and fit Resonix CLD to the outside as well.
5- Mount poly reinforcing ring to enclosure opening.
6- Remove stock wiring and grommet, retain the grommet.
7- Slide grommet onto new wiring and RTV it in place.
8- Insert Polyfil.
9- Insert and wire up 8” Alpine Type R subwoofer.
10- Reinstall loaded enclosure with rubber grommets under the mounting feet.

Now, you will need to feed this little beast some power to make it rumble. I used my JL Audio XD1000/1 wired at 4 ohms to send 600 watts to it. The results are astounding. I’ve redone the back end of my entire competition grade system because of how good this performs. Pics below....

Resonix: ResoNix Sound Solutions – Premium Automotive Sound Treatment Solutions

Mounting Ring:

Wire Connection: https://www.amazon.com/gp/aw/d/B01ETROGP4?psc=1&ref=ppx_pop_mob_b_asin_title

Polyfil:

RTV: https://www.amazon.com/gp/aw/d/B0002UEN1U?psc=1&ref=ppx_pop_mob_b_asin_title

Subwoofer:
 

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2019 Touring: since March-2019
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Hello Ironchef, I was just thinking about you the other day because I was actually looking into upgrading my Sub, so this came at a perfect time.

The main difference is that I am wanting to use the OEM Amp to power it. Do you have any idea of the number of Watts being sent to the OEM sub, by the OEM amp?

I will be sure to do all the extra insulation you mention.

Other than that how is your system sounding now???
 

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Discussion Starter #5
Hello Ironchef, I was just thinking about you the other day because I was actually looking into upgrading my Sub, so this came at a perfect time.

The main difference is that I am wanting to use the OEM Amp to power it. Do you have any idea of the number of Watts being sent to the OEM sub, by the OEM amp?

I will be sure to do all the extra insulation you mention.

Other than that how is your system sounding now???
So, the techniques above will net a much better enclosure capable of handling power and sound production. But I can’t remember if the stock sub is a 1 or 2 ohm unit. Now, the power from the stock amp is pretty low but either of these might just work for you:

If stock is 2 ohm:

If stock is 1 ohm:
 

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2019 Touring: since March-2019
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Thanks, it is 2 ohm, and yep, that was one of the the two I was looking at!

Hey did you calculate the OEM Sub enclosure size? And is it ported?

This is what the (above) Sub lists for enclosures:
  • sealed box volume: 0.5-1.2 cu. ft.
  • ported box volume: 0.66-1.2 cu. ft.
Just wanted to be sure the OEM matches the requirements...

Cheers!
 

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Discussion Starter #7
Thanks, it is 2 ohm, and yep, that was one of the the two I was looking at!

Hey did you calculate the OEM Sub enclosure size? And is it ported?

This is what the (above) Sub lists for enclosures:
  • sealed box volume: 0.5-1.2 cu. ft.
  • ported box volume: 0.66-1.2 cu. ft.
Just wanted to be sure the OEM matches the requirements...

Cheers!
It’s a sealed enclosure that downfires into the floor. As to volume, I didn’t measure since the Alpine requires a mere 0.15 cu ft. My guess would be that it’s around 0.3 cu ft, but that’s just a guess.
IMO, I wouldn’t lose sleep over the volume. It’s far more important to enhance the structure of the enclosure, especially since the factory amplifier outlet is limited. Spend the money though and get the Resonix. I’ve worked with just about every sound deadening product and this one is hands down superior and a big part of the success of this modification.
 

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2020 Honda Passport Touring AWD, Gray/Blk
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Nice write up IC! I was hoping to upgrade the sub. Have you changed out your speakers as well?
 

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2020 Honda Passport Touring AWD, Gray/Blk
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He Zero, It's an awesome looking system, but be warned: don't look unless you have lots of money....lol

Haha.. Too late.. I already looked. One thing I love doing to my cars is making sure they have a great sound system. With the amount of time I spend in my cars, I need to have good quality sound system.
 

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Nice mod! Really like the custom enclosure. It is a great space for something like that if you aren't storing things there. I did competition style systems long ago and don't have the interest or time any more but applaud those who do and still enjoy seeing what people come up with.

I also did similar mods to the stock sub enclosure but left it connected to stock amp and also added a cheaper Rockford Punch 300 8" powered enclosure tapped off the sub line level. The stock sub is dual 2 ohm. Without an add on amp, the stock amp is woefully underpowered for a Pioneer or Alpine sub or any high power sub really- I tried and would not advise anyone waste the time or money.

I carry too much gear for other things to dedicate permanent space in this car to amps and equalizers and more, so adding the removable Rockford enclosure was a good solution and it is more controlled and lower frequency capable than I would have expected for a budget 8". I also updated all four door speakers to Infinity coax to have something more accurate and sensitive, but retained the stock amp for them. It sounds great (for what it is) and the extra sub is removable in seconds when I need to carry more gear in the cargo area.

Getting fairly quiet tires and installing a proper amount of vibration damper, mass loaded vinyl, and closed cell foam made the largest difference in the quality of being in the cabin, and of the audio- far more than anything I did to the audio system itself. Making the cabin quieter along with disconnecting the fake exhaust sound (yes, really Honda...) and active noise cancelation module, made a quality improvement as well. I'd advise anyone spending significant time and money on audio for this vehicle- properly treat your doors, roof, hatch and floor with the right materials- which is NOT ten layers of dynamat or covering every inch with it- beyond a certain amount is zero benefit. 25-40% coverage of a single layer of a quality butyl vibration damper on resonant sheet metal or plastic, closed cell foam in open spaces and roof under headliner, and properly decoupled 1/16" mass loaded vinyl on floor and doors can take audio, and peace, to a new level in this vehicle.
 

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Hi Storm303, I want to add a stand alone powered sub similar to what you describe... Did you use a line out converter to connect yours? Or is there a line level out somewhere? I haven’t done much car audio stuff but I have a powered JBL sub lying around that I would like to use and I’m wondering how you tapped into the system to feed your Rockford?

Nice mod! Really like the custom enclosure. It is a great space for something like that if you aren't storing things there. I did competition style systems long ago and don't have the interest or time any more but applaud those who do and still enjoy seeing what people come up with.

I also did similar mods to the stock sub enclosure but left it connected to stock amp and also added a cheaper Rockford Punch 300 8" powered enclosure tapped off the sub line level. The stock sub is dual 2 ohm. Without an add on amp, the stock amp is woefully underpowered for a Pioneer or Alpine sub or any high power sub really- I tried and would not advise anyone waste the time or money.

I carry too much gear for other things to dedicate permanent space in this car to amps and equalizers and more, so adding the removable Rockford enclosure was a good solution and it is more controlled and lower frequency capable than I would have expected for a budget 8". I also updated all four door speakers to Infinity coax to have something more accurate and sensitive, but retained the stock amp for them. It sounds great (for what it is) and the extra sub is removable in seconds when I need to carry more gear in the cargo area.

Getting fairly quiet tires and installing a proper amount of vibration damper, mass loaded vinyl, and closed cell foam made the largest difference in the quality of being in the cabin, and of the audio- far more than anything I did to the audio system itself. Making the cabin quieter along with disconnecting the fake exhaust sound (yes, really Honda...) and active noise cancelation module, made a quality improvement as well. I'd advise anyone spending significant time and money on audio for this vehicle- properly treat your doors, roof, hatch and floor with the right materials- which is NOT ten layers of dynamat or covering every inch with it- beyond a certain amount is zero benefit. 25-40% coverage of a single layer of a quality butyl vibration damper on resonant sheet metal or plastic, closed cell foam in open spaces and roof under headliner, and properly decoupled 1/16" mass loaded vinyl on floor and doors can take audio, and peace, to a new level in this vehicle.
 

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Hi Storm303, I want to add a stand alone powered sub similar to what you describe... Did you use a line out converter to connect yours? Or is there a line level out somewhere? I haven’t done much car audio stuff but I have a powered JBL sub lying around that I would like to use and I’m wondering how you tapped into the system to feed your Rockford?
My powered Rockford sub enclosure has a stereo line level input with high impedance (four wires, 2 per stereo channel of the input). This let me tap into the factory speaker wire for the sub without affecting the 2 ohm load. If your powered sub has similar line level inputs you are all set. If not you will need a line level converter.

I tapped the stock harness between factory amp and sub, on the wires for both voice coil pairs (+/- for two pairs, four wires total).

The factory sub speaker wire is easily tapped where it crosses the cargo floor from the opposite side and plugs into the factory sub.

One of the factory sub wire pair colors in the loom is red+ and white-. The other channel is Brown+ and Grey-. This is for the Touring and Elite model of course and might be different on a different trim.

If I get a chance, I will take a picture of this install later.
 

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Storm303, Thanks for the info!

It looks like my sub, a JBL GT-BassPro 12, also has the stereo level 4 pin input, and when that is in use the amp doesn’t need a remote-on signal either. So I won’t need a line out converter.

The remaining thing to figure out is since I’m in an EXL, it is looking like the OEM sub is being fed with 2 wires rather than 4. I think I saw somewhere else on this form that the actual stock subwoofer itself is the same between the lower and higher trims, but it’s a dual voice coil fed with two wires (and less power) in lower trims and four wires (and more power) on Touring/Elite.

What I’m wondering now is if those two wires feeding the OEM Sub would be sufficient to tap into and kind of splice the two signals into four for the four pin JBL input, or if that would change the Ohm load... Or if I will have to go find one of the rear door speaker wires for the other “half” of the 4 pin hi level tap.

Any thoughts there?

My powered Rockford sub enclosure has a stereo line level input with high impedance (four wires, 2 per stereo channel of the input). This let me tap into the factory speaker wire for the sub without affecting the 2 ohm load. If your powered sub has similar line level inputs you are all set. If not you will need a line level converter.

I tapped the stock harness between factory amp and sub, on the wires for both voice coil pairs (+/- for two pairs, four wires total).

The factory sub speaker wire is easily tapped where it crosses the cargo floor from the opposite side and plugs into the factory sub.

One of the factory sub wire pair colors in the loom is red+ and white-. The other channel is Brown+ and Grey-. This is for the Touring and Elite model of course and might be different on a different trim.

If I get a chance, I will take a picture of this install later.
 

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Storm303, Thanks for the info!

It looks like my sub, a JBL GT-BassPro 12, also has the stereo level 4 pin input, and when that is in use the amp doesn’t need a remote-on signal either. So I won’t need a line out converter.

The remaining thing to figure out is since I’m in an EXL, it is looking like the OEM sub is being fed with 2 wires rather than 4. I think I saw somewhere else on this form that the actual stock subwoofer itself is the same between the lower and higher trims, but it’s a dual voice coil fed with two wires (and less power) in lower trims and four wires (and more power) on Touring/Elite.

What I’m wondering now is if those two wires feeding the OEM Sub would be sufficient to tap into and kind of splice the two signals into four for the four pin JBL input, or if that would change the Ohm load... Or if I will have to go find one of the rear door speaker wires for the other “half” of the 4 pin hi level tap.

Any thoughts there?
I think you would be ok tapping off two wires of the factory sub harness. Just get the +/+ and -/- paired from both channels of the 4 wires on your JBL sub. Or, your JBL might allow wiring only two wires, might check the manual. Some powered subs can take a + from one channel and - from the other, others need both pairs connected (like mine).

Line/speaker level inputs are always high impedance, like 10k ohms or similar. So to a 2 ohm (or EXL 4 ohm if it is two wires split to two coils) load like the factory sub, the high impedance taps should not make a difference in power delivered. Only a very tiny current will flow to the taps of your JBL sub, while almost all goes on to the factory sub.

Also note, you will need to disconnect the active noise cancelling module most likely or you may get sub hum. This is because the factory sub damps road noise by playing out of phase noise back (inaudible but some effect). I am pretty sure the EXL has this too. Extra subs and their amps can confuse the system feedback loop.

I noticed almost no road noise change when I pulled mine, and the fake exhaust sound that is subtly played on the speakers to make it sound 'tougher' is gone, which I am glad for. The change is slight but makes for a better audio experience.
 

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Thanks again Storm! I got the 4 pin harness in the mail today and spliced the two wires into the four and it works great!

Taking the trim panels off to get to the ANC module was the most delicate part of the job but I’m glad I did it. I’ve driven the first 2500 miles on the vehicle with the ANC module intact and I’m amazed at how much fake engine sound was being piped in now that it’s off for the first time today. Maybe my brain is exaggerating the difference but when I give it some heavy gas pedal it sounds much less “taxing” on the engine than what I think I was hearing while the module was intact. It didn’t seem to be just low end / bassy exhaust either but also a fake engine whine that’s higher in tone. Maybe I’m imagining things though.

I wish it was something Honda would give the head unit full ability to control. I wouldn’t mind having 10% of what it was remaining piped in.

I’m going to mess with EQ a good bit and maybe down the road look at the sound deadening project and Infinity 6532ex speakers for the front doors. For now, the added low end from the JBL seems to allow the stock speakers to focus more on the mid to upper end of the spectrum than they were.

I think you would be ok tapping off two wires of the factory sub harness. Just get the +/+ and -/- paired from both channels of the 4 wires on your JBL sub. Or, your JBL might allow wiring only two wires, might check the manual. Some powered subs can take a + from one channel and - from the other, others need both pairs connected (like mine).

Line/speaker level inputs are always high impedance, like 10k ohms or similar. So to a 2 ohm (or EXL 4 ohm if it is two wires split to two coils) load like the factory sub, the high impedance taps should not make a difference in power delivered. Only a very tiny current will flow to the taps of your JBL sub, while almost all goes on to the factory sub.

Also note, you will need to disconnect the active noise cancelling module most likely or you may get sub hum. This is because the factory sub damps road noise by playing out of phase noise back (inaudible but some effect). I am pretty sure the EXL has this too. Extra subs and their amps can confuse the system feedback loop.

I noticed almost no road noise change when I pulled mine, and the fake exhaust sound that is subtly played on the speakers to make it sound 'tougher' is gone, which I am glad for. The change is slight but makes for a better audio experience.
 

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Thanks again Storm! I got the 4 pin harness in the mail today and spliced the two wires into the four and it works great!

Taking the trim panels off to get to the ANC module was the most delicate part of the job but I’m glad I did it. I’ve driven the first 2500 miles on the vehicle with the ANC module intact and I’m amazed at how much fake engine sound was being piped in now that it’s off for the first time today. Maybe my brain is exaggerating the difference but when I give it some heavy gas pedal it sounds much less “taxing” on the engine than what I think I was hearing while the module was intact. It didn’t seem to be just low end / bassy exhaust either but also a fake engine whine that’s higher in tone. Maybe I’m imagining things though.

I wish it was something Honda would give the head unit full ability to control. I wouldn’t mind having 10% of what it was remaining piped in.

I’m going to mess with EQ a good bit and maybe down the road look at the sound deadening project and Infinity 6532ex speakers for the front doors. For now, the added low end from the JBL seems to allow the stock speakers to focus more on the mid to upper end of the spectrum than they were.

Nice! Glad you got your first change working. Have you tried turning off the DTS sound? I found at first it sounded empty, but then realized it is way more clear and leave it that way now. Adds a bit of clarity to the low end especially.

I bet you won't miss the exhaust for long. Once I had some mass loaded vinyl in my doors and about 60% of the floor, it feels more serene and luxurious, and I can still hear the engine noise over my really quiet tires. Removing ANC actually does clear up the audio by removing those out of phase noise signals from the stock system and put slightly more power to the speakers on the factory amp. For my part, the amount of road noise it was removing was very miniscule, it might only have been removing the variable cylinder rumble which I can barely hear on this car anyway.

I too wish it was easy to toggle on or off the exhaust or configure it, along with ANC. If these engineers would cooperate more with popular modifications like stereos and wheel sizes, we all would not have to spend so much effort and money. Options are the best, but I guess each thing they have to support adds complexity to supporting the car.
 

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I’m thinking the DTS is a feature on the trims above EXL as I’m not seeing it in the sound menu.

I definitely do not have quiet tires right now as I’m in Michigan and I have snow tires on. I think I’ll live with it for now and down the road I’ll look into the sound deadening if/when I do the door speakers. But this is a definite improvement for now without fake noise and with a more full lower end.

Nice! Glad you got your first change working. Have you tried turning off the DTS sound? I found at first it sounded empty, but then realized it is way more clear and leave it that way now. Adds a bit of clarity to the low end especially.

I bet you won't miss the exhaust for long. Once I had some mass loaded vinyl in my doors and about 60% of the floor, it feels more serene and luxurious, and I can still hear the engine noise over my really quiet tires. Removing ANC actually does clear up the audio by removing those out of phase noise signals from the stock system and put slightly more power to the speakers on the factory amp. For my part, the amount of road noise it was removing was very miniscule, it might only have been removing the variable cylinder rumble which I can barely hear on this car anyway.

I too wish it was easy to toggle on or off the exhaust or configure it, along with ANC. If these engineers would cooperate more with popular modifications like stereos and wheel sizes, we all would not have to spend so much effort and money. Options are the best, but I guess each thing they have to support adds complexity to supporting the car.
 
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