'73 Stereo Install

[DC3]

I installed a new stereo system in my '73 last fall and just now got around to dealing with the photos.

I went with a Kenwood X693 Head Unit, Kenwood XR-4S class D 4 channel amp (120 watts per channel), Boston Acoustic S75 4"x6" speakers in the dash, Boston Acoustic SL65 6 1/2" speakers in the kick panels, and a Polk Audio MM840 8" subwoofer. I'm using a 120GB iPod Classic as the main source of music. I ripped the music in Apple's lossless format for best audio quality and I ran the docking cable under the console into the ash tray

I'm using the head unit to drive the dash speakers for fill, using the front 2 channels of the amp for the kick panel speakers and bridging the rear 2 channels of the amp for the subwoofer.

The amp is really too much for the kick panel speakers I selected so I dialed the gain back a bit and have to remember not to crank it all the way. Couldn't find a suitable Class D amp with less wattage and I really needed more for the sub anyway.

All in all I am extremely happy with the way it turned out. The sound is awesome. I can't believe how much bass the 8" Polk sub puts out. Very tight bass without being boomy. It will definitely get your attention.

I've used Boston Acoustic speakers in the past and really love their sound so I was very happy I could make them fit.

I didn't document the head unit, speaker and amp install with photos since there are plenty of photos on the web for that but I did document how I built the fiberglass subwoofer enclosure.

Here's some pics of the finished install. I'll document the enclosure construction beginning with the next post.







The speaker grills are also designed for the Boston 6 3/4" speakers so they stick out a bit in this installation but I don't mind. Looks fine with the doors closed.



I mounted the amp in the jack compartment and found a smaller jack that I could put in a water proof boat bag and store in the wheel of the spare tire.

Class D amps run very cool compared to other amps so I was not overly concerned with mounting it in an enclosed location. Nevertheless, I decided to give the compartment a bit of added ventilation and used some 2" aluminum soffit vents from Lowes.



Here's the sub mounted over the driver's side wheel well.

 

[DC3]

Subwoofer Enclosure Construction

I knew I didn't want a big subwoofer box taking up space in the back. The corner above the driver's side rear wheel was just begging for a sub but I wasn't sure the space was big enough. Some quick calculations revealed a space big enough for an 8" sub but the enclosure was going to have to be an irregular shape to accommodate the space.

I decided to start with some foam blocks I picked up in the craft section at Walmart. The idea was to use the foam to sculpt the enclosure and then fiberglass the resulting shape.

I began gluing foam blocks together and sculpting until I ended up with this shape:





The subwoofer specs called for an enclosure with a certain interior volume. I taped some heavy plastic over the foam shape as tight as I could and then cut it free and taped it back together to get a hollow model of the shape. I then found a cardboard box that was the correct volume for the sub. Filled the box with some foam shipping pellets and then poured those pellets into the plastic model to estimate the volume of the enclosure. I got lucky and my shape was nearly the correct volume. I did add more foam to increase the volume just a little to account for the thickness of the fiberglass and the sound deadener I intended to install on the inside. The enclosure volume doesn't have to be perfect but it does need to be within the range specified by the sub manufacturer for best sound.

After I got the shape about right, I installed a wooden ring for mounting the sub. I then stretched some panty hose over the enclosure and put a coat of resin on it to stiffen everything up for the first layer of fiberglass.



Here is the enclosure after 4 layers of fiberglass and the center ring cut out. 3 layers would probably have been sufficient but I had the materials to add the 4th layer so I did.



I then began removing the foam from the inside using an ice cream scoop.



To be continued with the next post.

 

[DC3]

Here is the completed enclosure along with the speaker terminals that will be installed on the back:



Hole cut for speaker terminals:



Test fit:



I had to remove the astrovent vacuum operator and linkage for the enclosure to fit properly. I just left the astrovent doors hanging open for the time being. I'll probably seal them shut when I add air conditioning.

Here's the box with sound deadener installed on the interior and unbacked carpet covering the exterior:





The bracket was used to mount the enclosure to the seat belt bolt. I used well nuts to secure the enclosure to the back wall. You can barely see the bolts in the interior of the box in the next photo.



If I had it to do again, I would make the enclosure just slightly smaller. With the 4th layer of fiberglass and the carpet being thicker than I needed the enclosure sticks out a bit more over the wheel well than I intended. This prevents the battery compartment door from opening all the way. It's not so bad that I have to hold the door open or that it impedes getting in or out of the battery box but it would have been better for it to be able to open normally.

Another minor drawback with this sub location and my enclosure is that I can no longer mount a factory rear window tray to store the rear window when I have it out. No big deal, I'll figure something else out. By the way, I highly recommend the removable rear window conversion if your Vette doesn't have it but can accommodate it.

This system rocks. It has more than enough volume to overcome wind and exhaust with the tops off and the back window out. It's amazing how good it sounds when parked with the engine off.

DC

 

[Arthur Brown]

wow, the enclosure looks great. Pantyhose ??? Never thought about using it for fiberglass, sometimes the simplest things are overlooked LOL

 

[DC3]

wow, the enclosure looks great. Pantyhose ??? Never thought about using it for fiberglass, sometimes the simplest things are overlooked LOL

Thanks. I don't remember where I picked up the panty hose trick. Probably on the web somewhere.

Tall thin guys like me get strange looks at Walmart when buying queen sized black panty hose. :blush:

DC

 

[Richard454]

wow, the enclosure looks great. Pantyhose ??? Never thought about using it for fiberglass, sometimes the simplest things are overlooked LOL

Thanks. I don't remember where I picked up the panty hose trick. Probably on the web somewhere.

Tall thin guys like me get strange looks at Walmart when buying queen sized black panty hose. :blush:

DC

I don't think it's just the panty hose...Buying flower arrangement stuff put's you over the top.

Great idea w/ the panty hose- I've always used old t-shirts.

 

[Fuelie74]

I love it. That is the first sub box I have seen put into a C3 that I actually like.