C7 Subwoofer - Proof of Concept

[JWebb_C7_Comp]

Hey guys,

As some of you may recall, I have been messing around with subwoofer options for my 2018 A6; and, I've done a simple amplifier and in-deck subwoofer installation for test/proof of concept purposes. Details, impressions, pictures and plan below.

Background

1. 2018 A6 Comp
2. Stock Bose system
3. Goal: use as little trunk space as possible, add moderate bass, look stock like (when finished)

Equipment

1. JL Audio 10TW1-2ohm
2. Audio Control ACM 1.3000
3. 300 Watt Amp install kit from Crutchfield
4. Speaker wire
5. Dynamat Extreme
6. 1x2 wood
7. 1/4 x 1.5" bolts w/ washers, nuts, fender washers, and rubber washers
8. 1/4 x 2" bolts
9. 1/4 x 3" bolts w/ washers, nuts, fender washers, and rubber washers
10. #8 bolts, lock washers and nuts

The installation was pretty easy after having reviewed what others have done. Disconnect your battery, run proper power, fuse and grounding. Run speaker wires, tap subwoofer lines from Bose system, and you're ready to test connectivity. In my case, all went as planned. Next, I tore apart my rear deck, removed the Bose equipment and, after using the Dremel tool to grind about 0.5mm out of the front and rear most portions of the "nearly" circular stock cut-out, I dropped the JL sub into place. Since my install is temporary, I only attached 4 of the 8 bolts for the sub, but have already drilled all 8 holes with a 5/32 bit. I made a wooden shim for the front (near seat back) to somewhat "level" the JL unit. Next, I "reinforced" the deck with two long strip of wood running from side to side near both the front and rear of the deck underside. These braces are temporarily attached to the deck via existing, factory holes (using bolts, rubber washers and larger Fender washers). Finally, I placed another "brace" running front to back (between the horizontal braces).


Impressions

1. This takes minimal space in the trunk, leaving trunk floor totally open.
2. I now have a "more complete" sound in the car. Music with which I am familiar seems to include the bass notes, whereas it didn't previously.
3. Even my son's hip-hop sounds pretty good unless volume is over 25 at which point we get just a faint buzzing sound from deck vibrations.
4. Next time I'd use something other than Dynamat because it doesn't have any sound absorbing quality like the product OlyS6 used. And, as a result, I used HMF under the deck as well.
5. Overall, sound is pretty good ----- but, certainly, much more can be done. For a moderate bump in bass, this hit the mark
6. As I have it now, the TEMPORARY braces look terrible, but this was to prove I could fit the sub into the deck, below Bose Subwoofer mount, under the interior portion of the deck while leaving my floor space intact.

Next Steps

I'm going to have the underside of the deck reinforced with a single wooden, HDPE or acrylic "plate" that has threaded inserts for bolts that connect through the top of the deck. That plate will be finished in carpet or alcantara to match the interior of the car.

[JBZ916]

Thanks for the write up on the install - I've been going back and forth between the rear deck install or just going with a small box. I've had sub-boxes in almost all of my vehicles for the last 20 years and I'm at a point where I hate giving up trunk space but yet still want some really good low end also....decisions, decisions.....

[ClaudeG]

wow that looks pretty bad ass! Great write up and job!

[OlyS6]

Nicely done! A few suggestions and questions-

1) On the next iteration, some extruded butyl rubber rope as a rim around the circular opening before you drop the sub in place will help 'deaden' any potential for vibrating the deck even more. You can get it pretty easily from Sound deadener showdown or elsewhere.
2) Flip whatever bolts you can so the ends are pointing upwards rather than down into the trunk- you can even then use shorter ones, or simply dremel off the lengths that you don't want, and they'll be covered by your rear deck cover.
3) You can pop off the screen on your sub, since you'll be using the OEM screen for the rear deck.

Question- I'm not familiar with your exact sub- is it an IB sub and your plan is to have the overall trunk serve as your baffle?

Nice overall solution- you've now got even more trunk space than I have since I've got a box mounted underneath!

[OlyS6]

Thanks for the write up on the install - I've been going back and forth between the rear deck install or just going with a small box. I've had sub-boxes in almost all of my vehicles for the last 20 years and I'm at a point where I hate giving up trunk space but yet still want some really good low end also....decisions, decisions.....

Go with the rear deck! Our cars have pretty good sound deadening already between the cabin and trunk, so just throwing a box in the back (like I did in my car for the first year) is comparatively muffled. With a small amount of reinforcement, (a layer of plywood), the deck surprisingly doesn't rattle at all.

[JWebb_C7_Comp]

Thanks for the comments OlyS6.

For my next iteration, I am very likely to have a local shop (SoundzPlus in Naperville, IL) - that seems to like my temporary solution AND is happy to help with the next go-around, making certain I get the job done right - create a single wooden "plate" that covers the entire bottom of the deck, but for speaker and mounting hardware cut-outs. In fact, they said they'd make a template of cardboard, transfer that to wood and do assembly such that there'd only be ONE piece supporting the underside of that deck. They'd also use SoundSkin (top and bottom) and, as to mounting, they'd use short bolts (trimmed if needed) with black caps. But they recommended making them accessible from underneath. I can see mounting up top, however, because that would look even cleaner. Finally, they've got access to (1) carpet and (2) alcantara to match my interior colors. So, I'm getting prices on each. I'm somewhat inclined to do the Alcantara just because I think it would look really cool... In the end, my trunk would be fully serviceable and look better than stock.

Regarding the JL Audio 10TW1-2 ohm, it is NOT specifically rated for IB installation. That said, I test fit another sub that was IB/free-air rated; and, this JL sounds MUCH better (in my opinion, for my car, with my music preferences). This JL unit has a total speaker Qts of 0.649, which is pretty close to the correct rating for IB use. Moreover, it is a shallow mount, allows me to retain the stock Bose mounting bracket between sub and support portion of the deck (which I have retained to keep the top-side of the deck from rattling or sagging over the long term. Hence, I thought I'd give it a try; and it seems to work as an IB sub. Hence, I plan to keep it that way.

Focal has a nice unit that is marginally more shallow and would also fit nicely into that spot; so, if the JL fails at some point, I may give that a whirl. It's about $150 more than the JL and my general impression of Focal is that they sound great, but are more fragile... I do have some at home and am considering them as replacement separates for my dash.. So, I'm not bashing Focal one bit; I just figured I'd try the JL gear which known for solid subs, particularly if I'm using it outside designated purpose (i.e., IB versus in a box).

Butyl rubber rope is an absolutely tremendous idea and I WILL absolutely implement your suggestion!

I'll keep you all posted as to how this works out. It's pretty space and cost effective and, for me, seems to bring in enough bass without BS rattles and buzzes. Even my teenage son is happy with the change; and, he's not easily impressed with anything -- being a teenager.

[JWebb_C7_Comp]

Thanks for the write up on the install - I've been going back and forth between the rear deck install or just going with a small box. I've had sub-boxes in almost all of my vehicles for the last 20 years and I'm at a point where I hate giving up trunk space but yet still want some really good low end also....decisions, decisions.....

I wrestled with the same issue. I have a large trunk for a reason; and, I didn't want to give it up. I don't know what type of music you like or how loud you play it, but this set-up might work for you. If not, rip the woofer out of the deck and have someone make a box for you....

[JWebb_C7_Comp]

Butyl rope to be delivered Monday.

Shop is matching Alcantara door color for the trunk deck installation.

Install on Friday.

[OlyS6]

Nice! Looking forward to pics! If you ever decide to replace your 3 way fronts, I highly recommend Focal- the tweeters are just amazing, and overall sound reproduction is excellent. I’ve toyed with picking up the Focal sub, but I’ve been happy with my JL so far, and have other mods I’d like to move on to. As long as you have butyl rope coming in, use the amount left over for the woofers in your front doors as well!


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[JWebb_C7_Comp]

Thanks for the comments OlyS6. Have you taken the rear doors apart? Wondering if it makes sense to simply swap the rear door drivers with something a bit tighter? Also, curious if pulling grills only allows enough access to put SoundSkin or Focal Bam throughout the rear doors. Standing outside the car, it's clear there's substantial sound loss at the rear doors, but not hardly as much up front..

Focal is the likely go to for the fronts. It's just a matter of time. At this point, I'm super happy just to have a bit more bass. The sound is vastly improved with that modest upgrade.

Nice! Looking forward to pics! If you ever decide to replace your 3 way fronts, I highly recommend Focal- the tweeters are just amazing, and overall sound reproduction is excellent. I’ve toyed with picking up the Focal sub, but I’ve been happy with my JL so far, and have other mods I’d like to move on to. As long as you have butyl rope coming in, use the amount left over for the woofers in your front doors as well!


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[OlyS6]

Thanks for the comments OlyS6. Have you taken the rear doors apart? Wondering if it makes sense to simply swap the rear door drivers with something a bit tighter? Also, curious if pulling grills only allows enough access to put SoundSkin or Focal Bam throughout the rear doors. Standing outside the car, it's clear there's substantial sound loss at the rear doors, but not hardly as much up front..

Focal is the likely go to for the fronts. It's just a matter of time. At this point, I'm super happy just to have a bit more bass. The sound is vastly improved with that modest upgrade.

I wouldn't mess with the rear door speakers unless/until you decide to go with a DSP to actively control all your speaker outputs. Many folks don't use a rear fill at all, since if not properly programmed, makes your soundstage very shallow. Much more bang for your buck to replace the front component speakers. Unfortunately, just pulling the grill and speaker on the rear doors doesn't get you very much access. You need to pull the door panels, which actually isn't hard:

Use a pry tool on your trim around the inner door handle and the larger speaker grille. Remove the T25 bolts beneath the trim, larger speaker grille, and under the armrest.

Use a pry tool to pop the door panel off; NOTE: there are plastic locking tabs that hold the door panel on- make sure you have all of them pulled upwards to the 'open position' before you try putting the panel back on- you'll hear each of them 'pop' into place as you press the door panel back on. If you don't do this and any of them are in the closed position, it won't go on right- took me many tries before I learned this.

Then you can easily pop out the cable for the door handle, as well as the single (in the rear) or double (for the fronts) electrical connectors, and your door panel is free and clear. Just reverse the steps to put the panel back on. Pretty easy overall- no need to mess with the windows, although the whole operation is easier with the windows down, as it makes it easier to 'hook' the top of the door panels over their place on the sills.

[S4Per]

Nice work, JWebb!

A couple of things to consider:

• If you can, check-in with SubterFuse re IB. I faintly recall him stating that it's not trivial on these trunks to ensure you fully separate the forward and backward waves of the sub.
• Look around / research re speakers as there are lots of options. Most importantly: GO LISTEN to any/all you're considering. Whatever sounds best to you are the right ones. As for other brands, I'd throw out the following: Audiofrog is hugely well regarded, and I really like my Morel setup (Elate Titanium 903) in regards to the smooth tweeters and the thumping of the 9" mid-bass woofers that fit in our doors without much ado (I had Focal KX2's in my last car).

Cheers,
Per

[JWebb_C7_Comp]

IMG_2076.jpgIMG_2078.jpg

I picked-up my car last night. First off, let me give a great shout out to the guys at SoundzPlus. They took my concept and made it a reality; and, they did it very well. As you can see from the pictures here, they've integrated a new ceiling panel for the roof of my trunk/underside of the speaker deck. They also worked with the bracing I had started - adjusted with different hardware and butyl rope as noted above - and they reinforced it further, added SoundSkins, rerouted some of my wiring, re-installed the sub and got everything to look fantastic!

The car still smells just a bit of fiberglass because the panel is still off-gassing, and I haven't really driven it much at all. Once I do, I'll give you all my feedback on sound too. But, I can say that even last week, it was a significant improvement over stock. I'm sure if you had a BOX built with even bigger sub and amp, you could get better, tighter bass, but I wanted my trunk space maximized and this set-up clearly fits my primary needs.

Have a great weekend gents (and ladies).

[nadroj81]

the 12" jl marine sub is an infinite baffle design. (they also have 10s but the 12 handles way more power)

[JWebb_C7_Comp]

the 12" jl marine sub is an infinite baffle design. (they also have 10s but the 12 handles way more power)

Considered the 10”, but if top mounted, I wouldn’t be able to retain the stock Bose mounting bracket, which basically attaches the interior grill/deck to the metal below.. I suppose something new could be fabricated to take its place, but I didn’t want to mess with it..



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[OlyS6]

Looks great! Would like to hear feedback on how you feel it sounds and if they were able to eliminate all rattling.

[JWebb_C7_Comp]

I've had about an hour's worth of good listening time; some of that at high speed with windows open and volume past 30. I've listened to rock, jazz, hip-hop, etc.. The bass is pretty good (but certainly not tooth shatteringly tight), particularly now that I've pushed the "level" control on the AC 1.300 up to about 3/4 output. Gain, however, is at about 1/4. Only when listening to 21 Savage's Bank Account can I hear anything that sounds like a rattle/vibration. I can't tell where it's coming from. Could be the roof, speaker grill, etc.. When listening to my favorite music up to 30 or so, it sounds great, but for the (1) super crisp highs coming off the dash and (2) lack of super tight "kick-drum" out of the front door speakers. These issues, don't have anything to do with the sub-woofer installation, however.

I stopped by the installer's shop today. They gave me a bit of SoundSkin for the "D-pillar" trim, which I've used to replace the white stock foam --- staying well away from any attachment points, electronics or airbag gizmos. We discussed speakers that might be a tad softer at the extreme high frequencies and some that might give some thundering mid-bass. Ultimately, I'm going to set-up some time, have the whole system scoped such that we know frequency output/Db response and, importantly, what the Bose amp/processor is trying to send to each set of speakers. With that "blueprint" known, I can determine what I want to do with the system from there and the guys will be able to help choose (1) speaker options, (2) supporting amplifier(s) and (3) processor capabilities..

All that said, if the system sounded and looked as good when I got the car as it does today, I might have turned down the treble and left it alone. Now, I'm in for a few more tweaks!

At bottom, I'm completely satisfied with the trade-offs associated with the install. A big, sealed box would bring in more sound, etc at the cost of trunk floor space I'm unwilling to give-up. Hence, I think I've got the bass set-up about as good as it's going to get, given my preferences for my taste in music. In the end, this is highly subjective, kinda like running shoes or wine.

Happy to answer any specific questions I can.

[LawDawg]

Bringing this thread back. I'm also in Naperville, and I just installed a Pioneer IB sub in the rear deck with my B&O system. I'm really happy with it, with the exception of one thing...the rattles in the rear deck. I dynamatted the hell out of both the deck itself, as well as the rear parcel cover and speaker grilles. Still get awful rattles at some frequencies. I also have the sunshade, so I suspect that's a problem as well.

Do you think this is a job SoundzPluz could solve, or am I just dicked on account of the sunshade?

[Joe'sS6]

Bringing this thread back. I'm also in Naperville, and I just installed a Pioneer IB sub in the rear deck with my B&O system. I'm really happy with it, with the exception of one thing...the rattles in the rear deck. I dynamatted the hell out of both the deck itself, as well as the rear parcel cover and speaker grilles. Still get awful rattles at some frequencies. I also have the sunshade, so I suspect that's a problem as well.

Do you think this is a job SoundzPluz could solve, or am I just dicked on account of the sunshade?

Same problem here as well but only at very specific freqs. around 40-60 Htz and under very high power volume, when tested using those freqs. test tracks. My car also has soundproofed trunk and the electric rear sunshade, the rattle does come from the headliner, from where the headliner meets the rear window.

It is so rare to get this rattle under normal music listening conditions, that I decided not to dissasemble the headliner and soundproof there, that would be a mayor pita and possible source for other problems.