5.25" speaker in rear deck on Coupe?

[Alphaskoom]

I've seen a few posts of a few of you guys replacing the coupe's rear deck 4" speakers with 5.25" speakers with a bit of modding.. what sorta modding are we talking about here? it seems the best pictures i can find are from Crutchfield's install guide. But they only show factory speakers and the slot. The 5.25 speakers would be ideal as i wouldn't have to buy another set of crossovers for my speaker upgrade.

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[BailOut]

I just installed 5.25 Infinity Ref's in the rear. All parts of the install - from the plastic panel removal to the bracket retrofit to the final install and re-assembly - was a huge pain, if I wasn't committed to the speakers (non-returnable) I don't think I'd have gone through with it. That coupled with the poor sound output to the rear speakers channel by the stock HU and me scratching up the rear glass tint during the install to the where it now needs replacement (very tight fit back there) makes me regret it. Unless you install an aftermarket HU, you may not even hear a difference.

Some members on the forum have even advised against installing them... what you may do is rest the new rear speakers magnetically to the rear deck top and test 'em out w/o fastening anything down, see how they even sound vs. stock.

As far as the install went, I had to do heavy modifications of the bracket - cut out the speaker and enlarge the opening by removing the internal lip. Then I had to figure out how to attach the new speaker to the bracket. Glue would be the easiest, but as I was sold out I opted for 2 screws jerry-rigged to the frame.

Pro-tip: double layer the rear deck cutout lip with black tape at the spot where the speaker wire connector is - it is such a tight fit that it will actually touch the side of the cutout, resulting in a system-wide short that takes down all your speakers until it's properly insulated. I also bent the lip slightly with my hammer to enlarge it and accommodate the wire connector.

 

[Alphaskoom]

That sounds pretty labor intensive. Looks like they are sitting a bit higher than the factory ones do, how is their clearance with the factory rear deck covers on there?

I'm going to be using the factory Headunit but planning to use hondahack it and use the Viper4Android Eq balancer and aftermarket amp to power them so i shouldn't have any of the bad EQ problems that just a speaker replacement would do.

 

[Alphaskoom]

if you have any more pictures id love to see them

 

[BailOut]

That sounds pretty labor intensive. Looks like they are sitting a bit higher than the factory ones do, how is their clearance with the factory rear deck covers on there?

I actually had to shave down the height of the OEM speaker bracket by removing the top lip, making it an even, flat surface. This 1/4 inch or so eliminated any issues with height. Also, the rear deck plastic overlay panel has plenty of vertical space built into the 'silo' that aligns with each speaker, so if you have a tweeter that sticks up a bit it shouldn't be an issue.

Here's a picture from the trunk looking up:

 

[Alphaskoom]

hm, that certainly looks doable, im sure a day of dremmeling the old speaker is in order. thanks alot for your help, I'll add some pictures of my own when i get them in and hopefully more are willing to do this themselves.

 

[JT Si]

hm, that certainly looks doable, im sure a day of dremmeling the old speaker is in order. thanks alot for your help, I'll add some pictures of my own when i get them in and hopefully more are willing to do this themselves.

I'm interested to see how you do it. I bought replacement speakers for all around in my Si and I'm not quite satisfied with how much smaller than the OEM speaker all the 4" options are. I did a little A/B testing of OEM vs the Alpine S-S40 I bought and it definitely sounds better but I'd like to not lose the quantity of mid-bass the larger OEM speaker provided.

I was looking at the Alpine S-S50 and it appears to be smaller than the Infinity that BailOut installed, but still appears it might require significant modification to the bracket.

I already cut one speaker out of the bracket so I can take more detailed measurements about various speaker fitment. The raised lip on the top is kind of a pain in the ass, but the Alpine's mounting hole size would fit inside the raised lip and I have a hunch maybe just fit without hollowing out the bracket at all. But the downside is the rear deck cutout would sit on the raised surface of the speaker, which would be around 5mm taller than OEM. Maybe the rear deck could be modified to remedy that, but I have a feeling that leaving the overall height for the rear deck to seat about the same is a better option.

@BailOut did you have to modify the rear deck to fit over the raised edge on your mounting? Or was there enough leeway in the design that it just sits a little higher now? It looks like you added around 5-8mm of height to where the ring on the rear deck seats against the speaker mount...

 

[BailOut]

No modification needed since I shaved off the top lip you mentioned. I believe there's even some space between the speaker and the rear deck plastic panel silo (from peeking through the plastic trapdoors on the rear deck panel).

 

[JT Si]

No modification needed since I shaved off the top lip you mentioned. I believe there's even some space between the speaker and the rear deck plastic panel silo (from peeking through the plastic trapdoors on the rear deck panel).

I'm surprised the speakers sit so high above the brackets in your photo. Is that how they were installed in the end? Or did they end up more flush after you shaved off the raised lip on the bracket?

On my OEM speakers, there's a clear indent in the foam surround of the adapter ring where the silo seats, and I get the idea raising that at all would press up against the rear deck and possibly cause some fitment issues.

 

[BailOut]

Here's how it looks peeking through the trapdoor. The silos are lightly resting on the speaker's outer metal ring:

 

[JT Si]

Here's how it looks peeking through the trapdoor. The silos are lightly resting on the speaker's outer metal ring:

Nice! I guess the rear deck has a little flexibility for the silo to rest a little higher.

 

[JT Si]

I received my 5-1/4" Alpine S-S50's. I don't like how much work I'll have to do to the OEM bracket to mount them, I am not convinced it will work, and they're going to be a really tight fit.

I am going to desolder the tweeter wires from the speaker terminals, remove the tweeter crossover for better basket clearance, and I ordered a sheet of 1/2" PVC to make adapter brackets with.

I'm going to see if the 1" tweeters I installed in the rear deck are enough fill from the rear, and if they aren't I can wire the 5-1/4" tweeters in parallel with the 1" tweeters for a bit of extra sound from the rear.

 

[BailOut]

After hearing awful distortion/rattle from the rear speakers, I decided it was all the impetus I needed to revisit the speakers and do a little investigation/experimentation that would hopefully get to the bottom of things.

First, the rear speaker bracket jerry-rig was still holding up nicely. The problem is that the rear edge of the plastic rear deck cover's silo (not visible from the front once installed) actually rests on the outer rubber edge of the speaker, inhibiting its movement (front edge is ok). So I can't use the jerry-rig anymore, need something proper.

Second, I was perplexed by the poor sound quality from the rear speakers, they were same make/model as the front - just the 5.25" version. Isolating one variable at a time, I discovered:

-The stock HU does indeed send a different version of the signal from the front to the back. A 6.5" speaker sounds positively awful back there compared to the front. Hear it for yourself as I fade back and forth between each one.

-The size difference matters bigly. 6.5-inchers blow away the smaller sizes... hear it for yourself as I switch from the left door (6.5") to the right door (5.25")

In summary: the speakers in the rear are receiving a stunted signal while being themselves stunted. To fix 100%, both an aftermarket HU and jigsawing the rear deck's speaker cutouts to accommodate at least the same size speaker as the front door are required. Of note, a modest improvement would be to splice the rear speaker wires to the front ones (thereby sending the good front signal to the rear too), but I lack the technical knowledge for even implementing that. Perhaps others would know and can chime in.

For now I'm just going to use a 1/2" pvc spacer to properly rig up the rear speakers and call it a day.

 

[JT Si]

Second, I was perplexed by the poor sound quality from the rear speakers, they were same make/model as the front - just the 5.25" version. Isolating one variable at a time, I discovered:

- A 6.5" speaker sounds positively awful back there compared to the front. Hear it for yourself as I fade back and forth between each one.

-The size difference matters bigly. 6.5-inchers blow away the smaller sizes... hear it for yourself as I switch from the left door (6.5") to the right door (5.25")

Yeah, you get an upgrade in sound quality akin to that going from the factory 4" size to a 5-1/4" as well as the upgrade again from 5-1/4" to 6.5". It's just disappointing Honda didn't make the effort to have the coupe's rear deck configuration match the sedan with 6.5" speakers.

Then again, even the sedan with 6.5" speakers faces the same crap rear speaker signal problem.

In summary: the speakers in the rear are receiving a stunted signal while being themselves stunted. To fix 100%, both an aftermarket HU and jigsawing the rear deck's speaker cutouts to accommodate at least the same size speaker as the front door are required. Of note, a modest improvement would be to splice the rear speaker wires to the front ones (thereby sending the good front signal to the rear too), but I lack the technical knowledge for even implementing that. Perhaps others would know and can chime in.

If you are using aftermarket amplifiers, splicing the wires to split the high level signal is not a problem.

If you are not using aftermarket amplifiers, and you splice the wires to drive both speakers, they are going to each get half the power which would be undesirable.

Unfortunately in both cases you would lose fading control.

For now I'm just going to use a 1/2" pvc spacer to properly rig up the rear speakers and call it a day.

If you're going to cut out the rear deck to accomodate 6.5" speakers, you may only need 1/4-3/8 PVC which will give your larger speaker surrounds that much more clearance from the silos. You'll need appropriately shorter screws.

It sounds like you're just going to mount up the 5-1/4" speakers for now?

The stock HU does indeed send a different version of the signal from the front to the back.

Did you have any luck trying out the DSP flat feature? It should fix the signal to the rears, but it might not stay between ignition cycles...

 

[BailOut]

JT:

Yes, after I posted I remembered that doubling the speaker load halves the watts/speaker output. So that wouldn't quite work on the stock HU that outputs little wattage to begin with. It's become genuinely frustrating that honda decided to put these itty bitty speakers back there and then send some filtered/low-volume signal back there too. They're almost useless! Before this I drove an old, simple, 2 door truck, standard cab. Had all of two 6.5 pioneer speakers in there. It sounded pretty good, but I was excited that this car had 4 speakers. What a disappointment it's turned out to be.

Regarding DSP flat, unfortunately I have the simple knobs/buttons HU in mine, as it's not an upper-trim level version.

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