Dashboard sound system modification
 

Hello,

i have the 986 sound package (HAES speakers) with CD-R 23. My speakers were OK, but i wanted to improve the sound quality. And don't wanted to invest too much money.

First i analyzed the electronic circuit. Just a simple electrolytic cap with 4.7 uF. Hm, that would mean an incomplete -6 dB crossover only for the tweeter at around 8 Khz. Crap.

Next i've tested the cap capacity. One cap was within specs. The other way off. No wonder you can't hear them, when the crossover frequency is way above 8 Khz with a bad cap.

http://986forum.com/forums/uploads02...1521895755.jpg
http://986forum.com/forums/uploads02...1521895777.jpg

So i did some tests with different caps and coils. In the end i decided to use 6.3 uF MKP caps and 0,22 mH coils. To my ears that sounds much better, because the mid frequencies (higher voice frequency) are damped a bit. Still use the fader to reduce power to the dash speakers and give door speakers a little more power.

This is a comparison to the BOSE dash speakers. I preferred the HAES ones, because the are 10 cm in diameter while the BOSE ones are only 8 cm in diameter and didn't had enough lower mid power in this configuration. Tweeters seems to be the same:

http://986forum.com/forums/uploads02...1521895797.jpg

This is the beta product (changed caps from 5.6 to 6.8 uF - see above). Didn't do a photo of the final product, but looks the same:

http://986forum.com/forums/uploads02...1521895827.jpg

If you want to copy the idea, take care that the caps are enough on the inside, so you get the loudspeakers with the casing in the dash without problems.

I always wanted to build my own crossovers. Nice work.
Did you use high end caps & coils like a Mundorf or Clarity?

Hi,

the capacitors are Audaphon MKT foil condensators. The coils are Mundorf. So good quality components (especially compared to the stock cheap electrolytic cap crap), but not really high end. Components i've used in the end are about 16 euros plus shipping.

But i've tested some alternatives 4.7, 5.6, 6.8 uF caps and different coils 0.27, 0.22, 0.18 mH. So in the end material costs incl. tests were about 40 euros.

It's a roadster with wind noises and very nice engine noises and the speakers itself are OK, but really not high end. So i think extrem high quality caps and coils would be overkill. ;) My goal was a better sound quality without too much effort and cost.

This is what I love about your posts...you do the legwork and have solid data to back up why you did what you did. Kudos.

That being said, the HAES speakers are getting some age on them, and honestly were probably selected by Porsche due to price point (vs say MB Quart). I highly respect the crossover you have built (far superior than original, and well made), but the primary component in the audio schematic is the physical speaker and it's components (magnet, voicecoil, cone), and those components aren't easily replaceable, and in my humble opinion you should consider replacing the entire speaker. I give this advice because I am far beyond guilty of spending way too much time redesigning or rebuilding something that could (or should) be replaced, and even though I enjoy it, I sometimes wish someone (besides my wife, lol) would call me out on the futility of my actions.

In any event, thanks for the detailed post and pictures...and darn it, you got me thinking if it's actually possible to improve the HAES speaker...I have my old ones in a box in the garage somewhere. Grrrrrr. ;)

+1 for the women who put up with us.

Hi MWS,

well i agree with you. The speakers are'nt the best, but they are OK.

The adapters and solutions i've seen to solve the sound problem and were easy to buy and setup were not the solution i would go for if i would do it right.

I'm an audio guy. Really good to me would mean to rip everything out and setup a full active 3-way system plus subs with complete measuring, equalizing and time alignment. Starting with the HU, amps, processor, speakers, noise dampening, building alloy adapters for the dash and so on and so on.

My other car has such an audio system - around 2 weeks of building and installation and another 2 weeks of setting everything up correctly. Result sounds really good to me.

But for the Boxster to me that wasn't the right idea. I don't want to add weight to the car and over all i want to leave it stock. So the idea was to keep it very simple and modify without much effort.

So......I own a 2004 with the Bose system.

I replaced the dash speakers with these:

https://www.ebay.com/itm/PAIR-JBL-GTO428-4-inch-2-ohm-105-watts-Car-Audio-Speakers-repl-GTO429-/281288625734?hash=item417e1bce46

Only required some minor cutting with a Dremel tool.

Easy, peasy.

What surprised me, was that they not only improved the sound quality, but the entire system volume want up by a pretty significant amount of db's.

If you can find any of these left somewhere, I highly recommend them as a simple plug-n-play mod for the Bose system.

The head unit and everything else is bone stock in my car.

I like where you are going with the crossover, but like the other folks said, these drivers are sub par and getting old, so you should really upgrade the whole speaker system.

FWIW, from my experience above, just R&R'ing the dash speakers alone makes a HUGE difference with the Bose system. i'm getting WAY more base outta the sub woofer and the door woofers just by changing the dash speakers and nothing else.

Good luck, keep us posted.

That's no wonder. As i've written above the BOSE speaker have a 8 cm (around 3 inch) diameter and the HAES speaker do have 10 cm (around 4 inch) diameter. So for the BOSE system 10 cm mid speakers are a real upgrade in the mid bass range. With the HAES mid speakers there won't be that much difference until you put in real high end mid range speakers that can generate real low end for a 10 cm speaker. So for the BOSE system i would also recommend 10 cm (4 inch) aftermarket speakers.

I'll put the BOSE ones on eBay. In a 996 they will be OK.

I have those gto speakers in my dash now, but replacing with 3 way components hertz mille, going active, with a 996 cabriolet bose pasenger subwoofer.

Project gone way overboard! Lol

Almost have the amp interface finished.

I have had infinity kappas, blaupunkt, and jbl. Out of those infinity sounded best to me. Helps putiing in a 996 6 channel amp, the fader will help adjust the door speakers.

Hm, today after some futher testing i changed the coils back to 0.27 mH coils and left the caps 6.3 uF.

And found something interesting concerning the stock wiring, i didn't notice before.

The BOSE 3" speakers are both in phase. The tweeters seems to be out of phase.

At the moment i have no tools to test the polarity of the tweeters.

The HEAS 4" speakers are different. Left is in phase while right is out of phase. Tweeters are a reverse polarity in comparison to the mid speakers.

Why is one HAES mid speaker in phase and one out of phase? This seems strange to me, because they both are directed in the same direction. And why are the tweeters also both out of phase compared to the mid speakers. Makes no sense to me.

Testing the speakers alone outside the car, the in phase speaker sounded better. So i will do both mid speakers in phase and both tweeters out of phase and test that in the car tomorrow.

Interesting, these cars are old in audio gear standards maybe the manufacture didnt pay much attention to the phasing. Or they phased it that way for the best sound based off the average acoustic enviroment. Been reading up on tuning seems my audio project is not a beginers project! Lol

Hm, good point. I will check the wiring and plugs coming from the amp first. Maybe they wired the wiring harness in a strange way, so that one side is inverse. Will check that first.

OK, today i did a little research.

first checked the M490 wiring diagram. Plus is full color cable, minus is cable with a stripe.

Rechecked that on the car. Male plugs in the car are wired both correctly. Plus = full color, minus stripe pn both sides.

So the right HAES speaker was wired out of phase completely.

Checked the HAES tweeters again. Under the clamp that holds the tweeter in place there is a print that shows the polatity. So the tweeters were not wired inverse in stock wiring. I was wrong there.

http://986forum.com/forums/uploads02...1522240025.jpg

The BOSE tweeters don't have that print on. But they are identical to the HAES ones.

A front picture of a 4" HAES speakers:

http://986forum.com/forums/uploads02...1522240067.jpg

A front picture of a 3" BOSE speakers - shure you notice the difference in diameter:

http://986forum.com/forums/uploads02...1522240092.jpg

Ended up with the plan i had and wired both HEAS speaker systems correctly, so the right one is completey in phase now - both wired the same.

Some things to mention. I noticed some gaps in the speaker housing at the latch and at the tweeters. Used some Teroston 81 to fill the gaps. As we all know speakers don't like housings with gaps.

Gap speaker:

http://986forum.com/forums/uploads02...1522240162.jpg

Gap speaker filled:

http://986forum.com/forums/uploads02...1522240184.jpg

Gap tweeter – picture shows only one – there are a lot - hard to take a photo:

http://986forum.com/forums/uploads02...1522240241.jpg

Gaps tweeter filled:

http://986forum.com/forums/uploads02...1522240274.jpg

Final product:

http://986forum.com/forums/uploads02...1522240296.jpg

Tested the system in the car and think at higher volumes it sounds better than before. Before there were some strange bass interferences in the mid bass area (male voices) that seems to be gone. I think that was because of the inverse polarity of the right speaker.

Everything can be brought back to stock without any problems.

PS: Picture upload in this forum is really annoying.

Are there "better/newer" aftermarket tweeters, to replace the OEM ones?