Volvo C70 convertible sound system build log

I removed the black wing-lets from the wing and noticed a difference in aerodynamics becasue the rear of my C70 turned easier and I felt less resistance at the steering wheel when changing lanes. I will make some wing-lets that match the contour / profile of the convertible top & the window molding.

I am really looking for more sound quality then out right spl. My plan is to mount the big tweeter in the dash & fire it back towards the driver and passenger with the mentioned mini subs on each side. I have some suspension and engine mods planned so I am going to ditch the pop-up roll bars behind the back seat and build a full cage.

Removing the pop-up roll bars will increase the size available for the rear sub enclosures - a set of 8's in the factory locations or any average size subs. The space to be gained is about 14" x 10" x 3.5" times 2 "one roll bar on each side". I am putting a great deal of thought into the design of my roll cage but one thing is clear, the front bars for the front hoop will be going down thru the tweeter holes in the dash.

So I want to recess a small tweeter at ear level in each bar & aim them at the driver and passengers ears but that is a year or so down the road.

As for sound damping I thought about factory sound damping sheets & dynamat and said to myself that is just a sheet of asphalt. Tar paper for a roof is like a sheet of asphalt and shingles, well shingles almost are a sheet of asphalt. So I went and purchased a pack of shingles, some thin pink foam isolation that was in a big roll and the to top it off some roofing cement. on the label it said trowel grade or trowel ready & it was the only roofing cement for vertical applications.

After I tint the windows on my C70 I will protect the fresh tint with some masking paper and then remove the doors and put them fender stands. my plan is to clean the inside of the doors with paint thinner and prep the surface really well. Then I have 3/4 of gallon of concert etch that I have left form when I used it to prep the gas tank of my Suzuki Bandit 1200 for a coat of tank sealer.

{just so you know} if the etch is poured on raw aluminum it will leave a deep dark gray coating / stain on the aluminum but anyway I will prep the doors with a coat of etch and let that dry after I wipe off the excess. Then I will do some calculating as to the curves & shapes of the insides of the doors, how to cut and position shingles and mask off everything I want to protect from the roofing cement.

Then I will brush over the shingles with a wire brush to remove any loose materiel and put them in the powder coating oven a phew at a time to warm them, {its 20 or 30 deg} then with rubber gloves and a spreader / trowel I will put a layer of the roofing cement on the inside of the doors. and then a very thin coat on the shingles and put them into position. I will do what ever looks best so their might be some over lap.

I think I will leave a inch or so space at the edges, then I will apply a even coat of roofing cement over the whole shingle covered area, then I will lay a double layer of the foam and stick it to the layer of roofing cement. I will let the doors sit for 24 or so hours on the fender stands to they are 180 degrees from their normal position so the cement can cure and seal.

I spent like $65 at Home Depot. The main thing that I am worried about is masking off everything I don't want to get the roofing cement on. The shingles & roofing cement will deaden & provide a degree of dampening. The foam will dampen and give the speakers sounds waves a softer cushion to absorbed into so they don't rebound & clash with the movement of the cone.

I will make sure to take pics, as for the aerodynamics I noticed a difference when I remove the wing-lets. I was looking at the rear wings on race Vipers, BMW and Ferrari's and the curve of the main area of the wing on some is very simpler to the curve on my wing - the structural difference is carbon fiber versus plastic.

When I looked at the wing-lets on those wings they used rectangles wing-lets. Some times a perfect rectangle and others had a rectangle with the top line curved to match the contour of the wing & then the rest a rectangle positioned vertical to the horizontal wing. So when I compared the wing-lets used on race cars to the ones that came on my wing, the ones that came with mine were wrong, I suppose they were ricer style - the manufacture thought they looked sweet but the taste when driving was.sour.

I purchased the wing as kind of a egg all rolled as a way to dip into the sauce and I figured I would spat out any parts I didn't like - particularly the side spates / wing-lets. With the general tso tapping I do when driving around town I noticed a difference in how the wing made the C70 feel and so I have some other aerodynamic mods planned.

The C70 is a European convertible so I won't make it look salty, I'll make it look hot like a pepper becasue my aerodynamics are at steak, I'll take pic's so you can peel the pages back like an onion.

Its been to cold for me to work on my C70 aside from bring in one of my headlights & marker lights to wrap them with blue transparent vinyl. After giving the a/c vent opening in the dash some more thought I think I am going to pass on installing a big tweet and 2 3inch mini subs. Three components would have looked crammed, instead I am just going to build a small box for two mini subs and then send them like 20 or 30 watts.

Well as for the C70's gauges, the ones on my C70 are basic and the water temp gauge has no numbers. The turbocharged 5 cylinder engine in my Volvo can make 300hp reliably with the right mods. My C70 is a 190HP low pressure turbo & the high pressure model makes like 235 ish HP. So with some modes my C70 can make more power reliably and then I would need to keep track of the motor. A 300HP stick shift convertible with a system and some suspension mods would be a fun & quick street car.

Many people would use a air fuel ratio gauge but I was thinking about using a digital voltmeter gauge hooked to the O2 sensor as a air fuel ratio gauge because I am just kind of strange like that.

I went to the pawnshop today to pickup some tools I had on layaway and just look at the audio equipment { for the third or forth time now} out of curiosity I asked what the three subs sitting on a top shelf were and one of them was a 12" JL W3. It wasn't in a box but it was in very good condition.

The guy that was showing me the subs I've know for years and he has or had a GSXR. Just so that I could remember how a single JL 12 sounds he turned on their JL test sub that they use to test amps. its in a big vented box, then he hooked up a W3 in a small sealed box and kicker comp 12 in a small vented box. The subs were being powered by a Memphis amp.

The dude gave me a great price on the W3 but I wanted to think about it for a minute and went next door to the tool shop. While thinking about the sub I figured I might as well try to do a package deal and buy some amps. I've been eying some JL amps for awhile - they came for sale {out of pawn years ago when I was working their} a JL 500/1 & a JL 450/4v2.

When I looked at the audio equipment a second time I took my time and really looked at the amps, I asked about a price for the JL W3 and the JL amps and another package deal with two Polk MOMO carbon fiber series amps. a 500/1 & a 975watt four channel. The JL package was more then I wanted to spend so I went with the Polk MOMO amps and the JL W3

My plan is to run the 8"s in my doors and the 8"s behind & built into the rear seat off the four channel. and run the W3 off the 500/1. The factory sound system has a four channel 400watt alpine amp, and the subs in the doors are 8 ohm and so are the 4 inch mids so they are wired parallel thru the competent speaker cross overs.

Some how their is a center channel and two 6.5 on the sides behind the front seats. I don't know if the center channel is run off the head unit & I don't know were the tweets receive signal from yet? it might be form the cross over in the doors, I need to trace the wires.

So I am planning to run some quality 4 ohm 4" mids in the doors and then figure out how to run two mini subs in the a/c dash vent area and run some tweets in the dash. When I out-grow the factory dolby pro-logic hu and upgrade, I might replace the factory alpine amp because it doesn't have RCA's & has no adjustments.

I didn't plan on putting any audio equipment on layaway and I was really leaning towards a 15" sub but the 12" W3 & Polk amps are a big step forward in building my system.