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> "Invisible" audio for the Porsche 914
horizontally-opposed
post Dec 20 2020, 12:43 AM
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Plans to go for a drive in my 914 this weekend were dashed by yesterday's stay-at-home alert, so I finally dug into a minor project I've been putting off: Rebuilding the car's 28-year-old audio system. While it performed well for 15-20 years, a mixture of age, heat, moisture, etc eventually caught up to it.

System goals: 1) Install a system powerful enough to be enjoyed with the top on or off; 2) maintain/improve "period correct" appearance with no head unit and, if possible, no visible speakers; 3) minimize weight; 4) avoid or minimize additional holes/etc.

I'm going into this with the understanding that it's entirely possible the exercise will be futile with a 2.2-liter flat six, but I have been collecting the parts over time and figure it's worth a shot. Some of this stuff has been sitting for years and thus may not be available anymore—but plenty of alternatives are.

Old system components:
Tape cassette head unit Smartphone flopping around on seat > EQ
Pyle graphic EQ turned on/off by factory rear defrost switch
Pioneer fan-cooled amplifier (~1991)
Boston Acoustics four-speaker set in doors (~1991)
Pioneer ducted bass wedge in passenger footwell

New system components:
Smartphone with a proper mount > EQ
Blaupunkt five-channel parametric EQ
JL five-channel amplifier
JL six-speaker set for factory speaker enclosures and door
?? subwoofer in passenger footwell (prepare for now, add later)

Fair warning: This thread may proceed at a glacial pace, as midlife plus a small business means my days in the garage are fairly rare in this chapter. I'm also figuring this out as I go, and will use this thread as a journal and a place to share ideas.
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horizontally-opposed
post Dec 20 2020, 12:47 AM
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Hmm, not able to upload images.

Different browser, no more problem.
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Jett
post Dec 20 2020, 09:21 AM
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QUOTE(horizontally-opposed @ Dec 19 2020, 10:47 PM) *

Hmm, not able to upload images for some reason. Hitting "choose file" does nothing. Will reset my browser and see what happens. Well, tried that to no avail.

Just checked other forums...no problem adding images there. This is something new for me on 914world—anyone else run into this or come up with a workaround?

I assume the pics are too big.

If you send the images to yourself via email, you can choose to reduce the resolution (size) to medium. Open the email, save the “medium images”, and use them to upload.
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Krieger
post Dec 20 2020, 10:58 AM
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Sometime, depending on what I'm attempting to share, I screenshot the pic. Then post the screenshot. Samsung
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horizontally-opposed
post Dec 20 2020, 11:26 AM
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I never read the manual, either—but I was curious what it might say about ideal speaker placement.

As it turns out, the 914 speaker enclosures provide a place to put the tweeters and mids in the preferred location, and I'll keep the larger speakers in the doors since they're already cut.


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bbrock
post Dec 20 2020, 11:29 AM
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QUOTE(horizontally-opposed @ Dec 20 2020, 10:26 AM) *

But, for now, this thread is…stalled. My signal to go back out into the garage and fiddle with low tech some more, and grab some more photos along the way. (IMG:style_emoticons/default/smile.gif)


(IMG:style_emoticons/default/popcorn[1].gif)
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horizontally-opposed
post Dec 20 2020, 09:43 PM
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The mids & tweeters will easily fit into the factory enclosures with the recommended 3.5- to 4.0-inch distance between their centers.

The door speakers will be trickier. The "pro" installers butchered my inner doors back in 1990~. While it's surprising how rigid the doors remain, I'll have to cut even more steel to get the new 6.5s in the same way. So I'm looking to see if I can mount the 6.5 from the other side. (I've never liked the way the speaker has to be pulled to remove the door card, or the way it pinches the door card.) Turns out the 6.5 can be maneuvered into the door, and could be securely held there with three mounting bolts. A curved (3D-printed?) plastic "mounting ring" (1/2 to 2/3rds of one anyway) would add rigidity and aid with sealing, while a Metra cover would protect the back of the 6.5 from rain water. Also thinking about custom cut styrofoam to close the 6.5 into the oddly shaped relief.

Short term, I'll simply bolt my old Boston Acoustics speaker grille to my existing door card, but I have a pair of ABS door card backings from 914Rubber and am thinking about "venting" the 6.5s through holes punched into the depressions in new basketweave over holes drilled into the ABS door card. Not sure this is viable, but it would allow for invisible 6.5s—much like the factory speaker holes seen in early 928s and a variety of other models… (IMG:style_emoticons/default/idea.gif)


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horizontally-opposed
post Dec 20 2020, 09:53 PM
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On, to system components.

Goals:

1) No head unit
2) Mount all electronics directly under the dash, away from moisture & heat
3) Minimize cable runs
4) Keep weight to a minimum

I was concerned about #4, as the new amp felt a lot heavier than the outgoing Pioneer amp. The crossovers felt chunky, as well. So I grabbed the bathroom scale. While I wouldn't trust it for postal use, things don't weight as much as I feared. And no head unit helps.

EQ + amp + crossovers > 10 pounds
Six speakers > 6.6 pounds


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horizontally-opposed
post Dec 20 2020, 09:59 PM
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Goals with the amp are to power the six-speaker setup while providing easy integration of a rear channel and/or a subwoofer down the road. Where the old amp was fan-cooled, this one uses traditional heat sinks.

EQ will be used mainly to accept/attenuate audio from a smartphone and to provide a remote line to turn the amp on or off, but it's nice to have the ability to adjust things.


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bandjoey
post Dec 20 2020, 11:37 PM
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I remembered this stereo setup from some years back. Perhaps it'll bring you some new ideas.

https://www.diymobileaudio.com/threads/old-...install.148283/
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horizontally-opposed
post Dec 21 2020, 12:41 AM
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QUOTE(bandjoey @ Dec 20 2020, 09:37 PM) *

I remembered this stereo setup from some years back. Perhaps it'll bring you some new ideas.

https://www.diymobileaudio.com/threads/old-...install.148283/


I remember that system—I think someone here posted about it, or maybe it was the old 914club?

Audiophile systems are a whole different world…my goal is to build a decent system on a modest budget that doesn't weigh much and won't be apparent unless you turn it on.
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horizontally-opposed
post Dec 21 2020, 01:08 AM
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With speaker locations figured out, next up is locating the other components.

The plan:
-Amp under dash on custom mount, left of the glovebox
-EQ under dash, left of the amp (which puts it near the odo knob)
-LH crossover in well where a head unit would normally go
-RH crossover to right of glovebox


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BillC
post Dec 21 2020, 09:15 AM
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QUOTE(horizontally-opposed @ Dec 20 2020, 10:43 PM) *

The mids & tweeters will easily fit into the factory enclosures with the recommended 3.5- to 4.0-inch distance between their centers.

The door speakers will be trickier. The "pro" installers butchered my inner doors back in 1990~. While it's surprising how rigid the doors remain, I'll have to cut even more steel to get the new 6.5s in the same way. So I'm looking to see if I can mount the 6.5 from the other side. (I've never liked the way the speaker has to be pulled to remove the door card, or the way it pinches the door card.) Turns out the 6.5 can be maneuvered into the door, and could be securely held there with three mounting bolts. A curved (3D-printed?) plastic "mounting ring" (1/2 to 2/3rds of one anyway) would add rigidity and aid with sealing, while a Metra cover would protect the back of the 6.5 from rain water. Also thinking about custom cut styrofoam to close the 6.5 into the oddly shaped relief.

Short term, I'll simply bolt my old Boston Acoustics speaker grille to my existing door card, but I have a pair of ABS door card backings from 914Rubber and am thinking about "venting" the 6.5s through holes punched into the depressions in new basketweave over holes drilled into the ABS door card. Not sure this is viable, but it would allow for invisible 6.5s—much like the factory speaker holes seen in early 928s and a variety of other models… (IMG:style_emoticons/default/idea.gif)

Hopefully this is just a silly question, but have you checked to see if the roll-up window will clear the door speaker when rolled all the way down? Back in high school, I saw plenty of home-grown speaker installations that had collision issues with various moving parts (window, door stay arm, etc.).

A suggestion for an alternate door speaker install:
Install the speaker on the inside (passenger compartment) side of the door sheet metal (like it looks like how your old speakers were installed. Then, trim the door panel to clear the rim of the speaker. Finally, install the speaker grill to the face of the door panel. This should give you more clearance inside the door shell for moving parts and still let you remove the door panel without having to remove the speaker first.
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horizontally-opposed
post Dec 21 2020, 03:49 PM
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QUOTE(BillC @ Dec 21 2020, 07:15 AM) *


Hopefully this is just a silly question, but have you checked to see if the roll-up window will clear the door speaker when rolled all the way down? Back in high school, I saw plenty of home-grown speaker installations that had collision issues with various moving parts (window, door stay arm, etc.).

A suggestion for an alternate door speaker install:
Install the speaker on the inside (passenger compartment) side of the door sheet metal (like it looks like how your old speakers were installed. Then, trim the door panel to clear the rim of the speaker. Finally, install the speaker grill to the face of the door panel. This should give you more clearance inside the door shell for moving parts and still let you remove the door panel without having to remove the speaker first.


There are no silly questions! (IMG:style_emoticons/default/beerchug.gif) I just want to do a thoughtful, methodical audio install, so feedback is welcome.

I did check for window clearance, and everything works well with this setup—at least with the inferior early style window regulator (1970 thru early 1973). This system will actually be cleaner than the old one in terms of the windows, as the crossover hidden in the door (what a life...and one of the crossovers sounded like a maraca when I pulled it out) moves into the cabin and the tweeter mounted high at the center of the door and its wiring will be disabled and/or removed.

The lower front of the doors is "found space," and the curve of the early window regulator almost looks like it was made with a large speaker in mind. Not sure what happens to this concept with the later "scissors" type window lift.

The approach you mention on mounting the speaker is interesting, and could work and/or be better. I'd want to figure out a way to mount the speaker grille to the door card, and the speaker to the door, for a finished look and to avoid figuring out how to trim the opening in the basketweave. May end up going this way, as it would be easier. Only real downside I see is the need to cut my door up even more. Not ruling it out, however…

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djway
post Dec 21 2020, 10:33 PM
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The last 914 I built was like rolling around inside massive headphones and it was amazing. I now make do in a room full of Klipsch (IMG:style_emoticons/default/smile.gif)
This is getting my mind going on the 914 underway (IMG:style_emoticons/default/idea.gif)
I have some technological catching up to do.....
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post Dec 26 2020, 02:07 AM
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Well Christmas delivered me a nice 6 speaker system with crossovers by Focal. A nice Rockford amplifier was included. Someone found an old wishlist.
What Bluetooth receiver do you recommend? Is the Blaupunkt good for what I have?I think all I need is the EQ, bt receiver and any cable not in my old stash. Maybe a sub also.
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horizontally-opposed
post Dec 26 2020, 10:52 PM
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QUOTE(djway @ Dec 26 2020, 12:07 AM) *

Well Christmas delivered me a nice 6 speaker system with crossovers by Focal. A nice Rockford amplifier was included. Someone found an old wishlist.
What Bluetooth receiver do you recommend? Is the Blaupunkt good for what I have?I think all I need is the EQ, bt receiver and any cable not in my old stash. Maybe a sub also.


^ Right on! Car gifts are among the best gifts! I have yet to decide on whether I will add a BT receiver, or just stay with a hard line from my phone into the RCA jacks on the back of the EQ. Or…both. (IMG:style_emoticons/default/smile.gif)

Waiting to see what 914Rubber does with its sub enclosure for the footwell, but building the system out with the later addition of a sub in mind—mainly because the amp I had in a closet was for a hatchback I no longer have. I wonder about adding rear speakers, too, but not until I try out the 6-speaker setup first.
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horizontally-opposed
post Dec 26 2020, 11:03 PM
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Not a huge update, but finished the rough cuts of the boards to mount the tweeters and mids. My thanks to @johannes for the excellent template for the factory speaker enclosures. I still managed to goober some bolt holes, but that's entirely on me.

I decided to use black ABS plastic order from TAP Plastics for the speaker boards, mainly as I wanted a stable mount that would not be compromised by time and/or moisture. I'll isolate the speakers with a bit of rubber, and have some hand finish work to do yet, but my initial worries that I had gone too far with the thickness of the boards disappeared once I cut the larger circles out. They are light, strong, and should work well.


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horizontally-opposed
post Dec 26 2020, 11:07 PM
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In factory enclosure, and with the speakers test fit.


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djway
post Dec 26 2020, 11:13 PM
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My understanding of high frequency sound waves generated by the tweeter that they are more directional than the other waves. Having them down low the listener may not hear the highs all that well.
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