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> "Invisible" audio for the Porsche 914
horizontally-opposed
post Dec 26 2020, 11:20 PM
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QUOTE(djway @ Dec 26 2020, 09:13 PM) *

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.


Had same concerns, but did some research on that in the audio forums (which make we 914 folk seem pretty normal (IMG:style_emoticons/default/laugh.gif) ) and not sure it will make much difference—particularly within the factory enclosure since they're nicely off the floor to begin with.

Was actually slightly more concerned about the bottom of the 914's dashboard blocking or bouncing signal from the highs if mounted as you normally would—but it's a relatively easy thing to change and I may mod these boards or make a second set for just that reason. We'll see.
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bbrock
post Dec 26 2020, 11:44 PM
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QUOTE(horizontally-opposed @ Dec 26 2020, 10:20 PM) *

QUOTE(djway @ Dec 26 2020, 09:13 PM) *

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.


Had same concerns, but did some research on that in the audio forums (which make we 914 folk seem pretty normal (IMG:style_emoticons/default/laugh.gif) ) and not sure it will make much difference—particularly within the factory enclosure since they're nicely off the floor to begin with.

Was actually slightly more concerned about the bottom of the 914's dashboard blocking or bouncing signal from the highs if mounted as you normally would—but it's a relatively easy thing to change and I may mod these boards or make a second set for just that reason. We'll see.


I can only speak for my setup with Infinity Kappas in the stock enclosures. The highs are incredibly crisp to the point of being a bit on the bright side for my taste. So much that I dialed them back a little on the amp and may do more but waiting for that 914Rubber sub box before doing anymore tuning.

BTW, I love that fancy circle cutting jig (IMG:style_emoticons/default/smile.gif)
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horizontally-opposed
post Dec 27 2020, 12:41 PM
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QUOTE(bbrock @ Dec 26 2020, 09:44 PM) *



BTW, I love that fancy circle cutting jig (IMG:style_emoticons/default/smile.gif)



Necessity breeds…crappy homemade tools. (IMG:style_emoticons/default/biggrin.gif)

Dremel has a tool for that, but with none available until sometime in January and 1/3 the price of a really nice cordless Dremel tool for a small piece of metal channel, I decided to roll my own—which got the job done but was far from ideal. So I may look at that tool yet…as this project has already showed me new uses for the Dremel.
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trick-e
post Dec 27 2020, 01:03 PM
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I’ve a set of enclosed Focal tweeters, with directional mounts, and was thinking I might mount them on the A-pillar trim where it meets the dash. Could run the cables through the screw hole. Keeps them up high. Then I thought about using gauge pod trim that replaces the a-pillar trim, but am still scratching my head.

Here’s an idea. https://www.glowshiftdirect.com/universal-s...20Products_Bing
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douglastic
post Dec 27 2020, 03:38 PM
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I put a hidden system in my 68 bug .. mounted the Separate tweeters inside the defrost vents. Sound unobstructed and invisible.

Could you mount your tweeters inside the corner of your dash vents?
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914_7T3
post Jan 9 2021, 04:24 PM
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@horizontally-opposed

Can you share the spec on the ABS plastic that you ordered to create the template for the stock enclosures?

I need to replace my speakers and realized that the original size 5"x7" will not fit. Just ordered a pair of 4"x6" Polk Audio with 1 3/4" mounting depth and need to create an insert in which to mount them in.

Thanks
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horizontally-opposed
post Jan 10 2021, 03:31 PM
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QUOTE(914_7T3 @ Jan 9 2021, 02:24 PM) *


Can you share the spec on the ABS plastic that you ordered to create the template for the stock enclosures?



Yep. Just measured it, and it looks like 3/16 inch—though it might have started as 1/4 inch before I got to sanding the back. (IMG:style_emoticons/default/wink.gif)
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windforfun
post Jan 10 2021, 04:49 PM
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I've done this in many cars. Great work! What's the rms output power per channel of the power amplifier? You may also need a Pi filter after the wiring from the battery to eliminate ignition noise.
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914_7T3
post Jan 11 2021, 07:44 PM
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QUOTE(horizontally-opposed @ Jan 10 2021, 01:31 PM) *

QUOTE(914_7T3 @ Jan 9 2021, 02:24 PM) *


Can you share the spec on the ABS plastic that you ordered to create the template for the stock enclosures?



Yep. Just measured it, and it looks like 3/16 inch—though it might have started as 1/4 inch before I got to sanding the back. (IMG:style_emoticons/default/wink.gif)



@horizontally-opposed

Thanks, I'll get some ordered this week!
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IronHillRestorations
post Jan 11 2021, 10:18 PM
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Put some surface mount tweeters on either side on the top of the dash, firing at the windshield, you'll get all the highs you need

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IronHillRestorations
post Jan 11 2021, 10:29 PM
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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/


WOW! What a meticulous installation.

Then all I could think of was my step father, who was a "Hi-Fi" audiophile all the way back from the early 60's; and how he thought everyone should just speak up and quit mumbling (IMG:style_emoticons/default/biggrin.gif) "Whaaat???"
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horizontally-opposed
post Jan 11 2021, 11:15 PM
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QUOTE(IronHillRestorations @ Jan 11 2021, 08:18 PM) *

Put some surface mount tweeters on either side on the top of the dash, firing at the windshield, you'll get all the highs you need


Violates goal of "invisible," and maintaining a period interior. (IMG:style_emoticons/default/shades.gif)

Also, was surprised to see JL not only recommend against the high-mount tweeters used by most OEMs, but to specifically recommend locating the tweeters and mids exactly where Porsche chose to mount speakers in the 914.

QUOTE(IronHillRestorations @ Jan 11 2021, 08:29 PM) *


WOW! What a meticulous installation.

Then all I could think of was my step father, who was a "Hi-Fi" audiophile all the way back from the early 60's; and how he thought everyone should just speak up and quit mumbling (IMG:style_emoticons/default/biggrin.gif) "Whaaat???"


Yeah, that one is "a little" over the top. (IMG:style_emoticons/default/wacko.gif)

Then again, let's be honest: None of us with a flat six behind our heads are doing our ears any favors... (IMG:style_emoticons/default/wink.gif)
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horizontally-opposed
post Jan 11 2021, 11:24 PM
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Okay, back to a relatively simple but good enough audio system that (hopefully) weighs 20~ pounds (or less).

Based on some of the comments here, I made a minor mod to Johannes' excellent template, allowing the boards to be swapped to either side of the car, and the tweeters to be mounted high or low.

One thing that didn't surprise me: I don't think the inside of my speaker boxes have ever been cleaned. One thing that did surprise me: one had old crusty cloth on it while the other used a thick foam. I'll be replacing both with modern fabric.


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horizontally-opposed
post Jan 11 2021, 11:28 PM
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A bit of test fitting. May use rivets for the mids, as many OEMs do, but we'll see.



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horizontally-opposed
post Jan 11 2021, 11:36 PM
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With the speaker enclosure plan coming into view, it's time to deal with the dash next—which brought me to the time-honored "while you're in there…"

I replaced my head unit with a smart phone about a decade ago and never looked back, replacing it with three gauges canted toward the driver. With no need for a clock, and no desire to install the amp and crossovers behind/under the dash only to have to remove them, I finally decided to order an outside temperature gauge—and will be sending it to North Hollywood Speedometer for a silver dot and (hopefully) a vintage bezel and glass.



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IronHillRestorations
post Jan 13 2021, 11:11 AM
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QUOTE(horizontally-opposed @ Jan 11 2021, 09:28 PM) *

A bit of test fitting. May use rivets for the mids, as many OEMs do, but we'll see.


Those look fantastic
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914forme
post Jan 13 2021, 11:46 AM
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QUOTE(horizontally-opposed @ Jan 12 2021, 12:15 AM) *


Also, was surprised to see JL not only recommend against the high-mount tweeters used by most OEMs, but to specifically recommend locating the tweeters and mids exactly where Porsche chose to mount speakers in the 914.



Not surprised at all with out a proper dsp you can not get sound staging correct. So placing the speakers down low put the two traditional sound locations as close to the same distance to the drivers ears as can be in a car interior. Simple math, gets the sounds waves to your ears as close to possible, minus all the reflection found in the cabin.

Higher end builds in competition world you use DSP and movable tweeters to get the tweeters pointed right to the judges or your ears. I have even seen tweeters with a laser "sights" on it to get them right on target.

As of today I would just go with an amp with a dsp and build the system how ever you can, then get a good set of ears to help you setup the sound stage how you want it to sound. Sony has one, but you can go crazy and spend $1000s on a DSP AMP or A separate DSP, and separate amps to drive what you need driving.
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Rob-O
post Jan 13 2021, 12:47 PM
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Those mids in the adapter plate look way too deep to fit in the stock location. I’d definitely test fit that. With the mid down low like that it’s not about crushing the paper heater hose. You can actually hit the small metal tube that is protruding from the rocker AND if it misses that can still be so deep that it hits the metal panel behind that.
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horizontally-opposed
post Jan 13 2021, 12:53 PM
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QUOTE(Rob-O @ Jan 13 2021, 10:47 AM) *

Those mids in the adapter plate look way too deep to fit in the stock location. I’d definitely test fit that. With the mid down low like that it’s not about crushing the paper heater hose. You can actually hit the small metal tube that is protruding from the rocker AND if it misses that can still be so deep that it hits the metal panel behind that.


Thanks for reminding me to mention: I tested this setup for clearance to the original paper hoses in my car—out the very same concerns.

The JL mids present no issues with clearance.
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914forme
post Jan 13 2021, 01:13 PM
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(IMG:style_emoticons/default/agree.gif) but I had also thought about building a small fiberglass surround to the back of the speakers that allowed the heat to flow through with the same cross section while allowing for the depth of the crush area needed for the larger magnets.

Just a thought

A bit of play dough made into the size of the tube, and smash it on in and see what you get. Then just add flexible coupler up top, the bottoms could be mounted with a simple coupler for transmission. Use the Play Dough to build the mold for the fiberglass part.
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