Do you have a 718 GT4/Spyder/GTS 4.0L and are you more sensitive to the amount of cabin drone/resonance in your car, whether it be stock or accentuated by various aftermarket exhaust configurations? You’re not alone, and if you’ve been following our Exhaust Development Thread you might know that Porsche has piped extra sound into your cabin through the firewall right behind your seats via a vibrating diaphragm called a Sound Symposer (and this is not the only car they do this in). Over the past month or so a few Rennlist members and customers of ours have been pursuing DIY modifications of deleting that sound symposer, and have reported significant reduction in drone/resonance in the cabin with different exhaust setups including various manufacturers. Spurred by this feedback, we documented the process for the Porsche community to reference, and hear the difference for ourselves.
KIT INCLUDES TWO CAPS TO COVER ENGINE SIDE OF SYMPOSER AND FIREWALL PORT
If you have any questions about this process or the results – please contact us. Modify your vehicle at your own risk.
To start, here is a Porsche diagram to show the full scope and functionality of the sound symposer:
With all engine covers removed, here’s the symposer as it sits from the factory:
Symposer section removed and remaining tubing capped:
Interior side of the cabin port:
The resulting delete is effective in reducing in cabin drone even on a stock 718. Here is a guide we made to show the process (on a Boxster GTS but the steps will be very similar for other models).
DIS295 (Rennlist) –
My car is the one pictured in John’s write up. My participation in this R&D arose from my complaining about the symposer noise to him and how I felt it was artificial and intruding into the cabin. This led to the symposer’s main hose & diaphragm removal and plugging of both the cabin/firewall port and the hose that is still being activated by vacuum. Once completed, John & I took a ride to see what, if any, was the effect. The symposer’s direction of intake sounds, when activated by vacuum, were now gone from the cabin. The cabin was quieter, but the engine vacuum/intake sounds could still be heard, but they emanated from the outside and were muted by the windows being up as well as the top.
Since then I have put a few hundred miles on the setup both solo and with wife(last night for about 50 miles). Both of us find the cabin quieter without the bothersome intake sound under both top up & top down conditions. Exactly what I had envisioned and wanted. Now I’m planning on installing SOUL’s oap to improve the exhaust sound..
Weekend weather was amazing so I took some time out to perform the sound tube delete. Glad I did. The cabin is much more civil now. Less boom and drone. Sound progression is more linear and natural. Also hear more of the engine and exhaust character.
Dave H. –
I too was having this “artificial” boom intrude into the cabin from this factory setup. I also noticed that with the cylinder cut process, that Porsche engineered in for fuel economy, exasperated the situation even further. I did a DIY delete of the symposer piping – what a difference. Don’t forget to hit the button to defeat the “auto shutoff” – this also disables the cylinder cut – no more “on/off throttle transition” of this noise. Oh, and add the Soul OTA pipes and their valve controller. You’ll be very happy with all four of these working in harmony!!!!!!