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Discussion Starter · #1 ·
I wrote this up on another forum under a thread about drone and the sound symposer a few days ago, but decided the work would potentially be more broadly interesting to people, so here it is:

So I spent all afternoon figuring out mostly how the sound symposer works… this may be controversial, but I’m going to just report it like it is. FYI, I have boxster gts with oem exhaust with a Soul VC installed as open/OEM mode. I’m leaning toward buying a Soul valved rear (only).

Anyway, I started by removing the rear carpeting. Then I got a partner and we drove around for a long time running a series of experiments in various modes.

1.) I used a spectrum analyzer on the iphone to see if any of the settings made a measurable difference at idle. It’s pretty easy to stick the mic in the hole. Outcome: symposer does nothing at idle. You can sorta hear the valve activate (maybe) when you hit the sport exhaust button, but nothing at idle appears to alter the sound coming through that pipe in any way.

2.) The symposer has absolutely zero function when the sport exhaust is turned off. Zero. Tried everything. Symposer is silent. Sorry if anyone disagrees, but stick your ear up to it at any speed, any mode, any throttle position, any rpm. Nothing. I’m pretty sure the valve is just closed when sport exhaust is off.

3.) The symposer does function when sport exhaust is on. However, its output appears to be directly proportional to throttle input, at least after a certain point. It’s relatively silent at low throttle input, but if you floor it then the output appears to be generally proportional to the rpms. It is loudest above 5k or so under hard throttle. You can get it to be active in the 2k-3k “drone range” under full throttle, but its definitely not loud at all — and is most certainly unlikely to be causing any drone, unless you count drone as occurring above 5k.

4.) This may be a surprise to some, but it sounds good! Basically, it sounds like real induction noise (because it kinda is?). It’s easy to make it silent with your hand, so you can just simply sit there and control/modulate it with your hand. It’s amusing to control it with your hand actually. And the vast majority of the sound is above 4k rpms.

5.) There is no reason to go to great lengths to completely disconnect it. A plug of foam works as well as your hand, which just simply completely silences it. It’s not more complicated than that… I know someone used a tuning fork/audiology analogy early on in another thread, but that does not hold here; this is a flexible, low mass, little plastic pipe hooked to relatively well damped steel (there’s a raised ridge in the metal where the symposer comes in that will stiffen and kill most resonance in this area, and certainly any from a connected plastic flexible pipe).

Bottom line: it sounds good, and if you don’t like it, just push the sport exhaust button to completely disable it. No reason to pull the car apart. Lastly, and most controversially, this is definitely not the source of the high levels of resonance being reported (I can hear it too with valves forced open). For those who are hearing a difference after disconnecting, well, I think it’s not from this. But if you want to confirm, again, just use the sport exhaust button.

Also of interest, the rear carpet makes a huge difference in interior sound level. This car sounds like the engine is inside the cabin without that carpet and foam padding. You can hear the belts spinning and just more engine noise in general when it’s removed. The engine panel itself is not particularly well damped, so I added some CLD (dynamat) to the cover and to some of the other area that was not well damped before I reinstalled the carpet. The oem carpet has a plug of foam missing right where the symposer exits so that you can hear it better.



Boxster GTS 4.0 Firewall

On the pic I have circled the symposer exit in red, area that is relatively undamped in yellow, and an unknown device in blue (anyone know what this is?). By the way, it’s easy to remove this carpet panel — only the speaker grille is in the way and it removes very easily with near zero risk of damage (pull from medial side)

My conclusion is that the Porsche engineers knew what they were doing and did not introduce drone via their symposer. They delivered a good solution to a problem and added in some real induction noise under high loads at high rpms (and they probably enjoy reading these threads).
 
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Very interesting! I have dozens of customers who have different experiences. With aftermarket OAP's the drone seems to bother them, and after disconnecting the symposer from the cabin (through caps or plugs) all reported a greatly reduced drone and better in cabin experience even with the increase in audible exhaust tone.

I have a customer who also added additional sound damping to the fire wall with the symposer delete and noted additional improvements. I'm not an engineer, but I would have expected additional sound damping material to further isolate NVH from the cabin.

So, in short, on a stock car the Symposer adds experience to the car that's been otherwise tamed (I was told due to ever increasing Euro regs), but it's not engineered with a change in the exhaust system in mind. This is feedback from customers on the road, not hypothetical. I always say "one man's tone is another man's drone".

Dave @ SOUL
 

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2021 718 Boxster GTS 4.0
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2021 Boxster GTS 4.0 Speakers grills come off easily. Pull from middle to outside. Pull the panel down behind the seats. Place choice of material into large black hold. I Used several pieces of foam and covered with bubble wrap and gorilla tape.

Subtle but the lack of overkill on the Intake sound is well worth it. Finally the car sounds like it is supposed to.
 

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Discussion Starter · #9 ·
You all are obviously welcome to stick stuff in that hole, I tried that too, but you can just push the sport exhaust button and get almost precisely the same result from your OEM solution. And it’s reversible! (Just press the factory button again.)

I understand that people report results from going to great lengths to disconnect the plastic pipe, but you can read my analysis at the top of this thread and decide for yourself. It’s fun to take your car apart, so there is that…
 

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Snrubel. Thanks for the comment and careful analysis. I understand Porsche engineer thinking and probably a majority of people think the "artificially Induced" sounds are Cool-I do not, emphatically. From the first minute I drove my new car my mind said something is not right. The symposer is just that-- a poser and it sounds very odd to my ears, not what I am used to. Now without it, with the top down I can hear induction noise coming from the flank (where it is supposed to come from) (compare......308 Ferrari).

While I am at it, I just received Cargraphic 3 mode device that will allow the exhaust valve(s) to either be always open, always closed (sports, or however Porsche wants it---open to ~2,000 rpm CLOSED Open again ~4,000 rpm Closed back to 3,000 rpm. Again, people may think this is cool, and again, I understand why the engineers did it, but again, the Aural experience is not one I am used to and I do not like not having CONTROL. The first time I heard that flappy noise as the exhaust valves closed as the rpms dropped below 4,000 rpm I said what the [email protected]#k was that noise. Now that I know what it is, I would like to be able to control the noise. It may turn out that I mostly keep it on "Porsche engineer" settings with sports exhaust (quieter between 2-4k RPM), but we will see.

If I follow Snrubel correctly, and I got rid of the foam plug in the Symposer outlet hole, I would still have to hear that horrible sucking sound between the seats with the sports exhaust on-------but this defeats the purpose of defeating Porsche's sound engineering principles. I have owned 50+ cars in my lifetime. Was an auto mechanic for british motors and I have a full restoration shop and a collection of High Performance autos..............shame on Porsche for piping in such noises---ugly noises is too harsh a statement. Unusual and artificially introduced noises fits. If you like it---hey, some people like chocolate some like vanilla.
Best,
RickP
 

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Snrubel. Thanks for the comment and careful analysis. I understand Porsche engineer thinking and probably a majority of people think the "artificially Induced" sounds are Cool-I do not, emphatically. From the first minute I drove my new car my mind said something is not right. The symposer is just that-- a poser and it sounds very odd to my ears, not what I am used to. Now without it, with the top down I can hear induction noise coming from the flank (where it is supposed to come from) (compare......308 Ferrari). .......
I couldn't agree more! Finally got around to stuffing a cork (literally) into the sound symposer behind the carpeted panel, huge improvement ! :)
 

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'23 718 GTS 4.0 - 6MT
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Snrubel. Thanks for the comment and careful analysis. I understand Porsche engineer thinking and probably a majority of people think the "artificially Induced" sounds are Cool-I do not, emphatically. From the first minute I drove my new car my mind said something is not right. The symposer is just that-- a poser and it sounds very odd to my ears, not what I am used to. Now without it, with the top down I can hear induction noise coming from the flank (where it is supposed to come from) (compare......308 Ferrari).

While I am at it, I just received Cargraphic 3 mode device that will allow the exhaust valve(s) to either be always open, always closed (sports, or however Porsche wants it---open to ~2,000 rpm CLOSED Open again ~4,000 rpm Closed back to 3,000 rpm. Again, people may think this is cool, and again, I understand why the engineers did it, but again, the Aural experience is not one I am used to and I do not like not having CONTROL. The first time I heard that flappy noise as the exhaust valves closed as the rpms dropped below 4,000 rpm I said what the [email protected]#k was that noise. Now that I know what it is, I would like to be able to control the noise. It may turn out that I mostly keep it on "Porsche engineer" settings with sports exhaust (quieter between 2-4k RPM), but we will see.

If I follow Snrubel correctly, and I got rid of the foam plug in the Symposer outlet hole, I would still have to hear that horrible sucking sound between the seats with the sports exhaust on-------but this defeats the purpose of defeating Porsche's sound engineering principles. I have owned 50+ cars in my lifetime. Was an auto mechanic for british motors and I have a full restoration shop and a collection of High Performance autos..............shame on Porsche for piping in such noises---ugly noises is too harsh a statement. Unusual and artificially introduced noises fits. If you like it---hey, some people like chocolate some like vanilla.
Best,
RickP
I get that most people don't like it, but I'm not sure what the problem is with Porsche's engineers trying to get you closer to your own engine noises via the symposer? It's not artificial like most cars have nowadays through speakers, it's just an amplifier of sorts to what is actually going on inside the engine bay, right?
 

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I read this post (great work by the OP) and some other information here and there.

The Service tech at my dealership told me there is, and I quote, a "delete kit available through aftermarket suppliers". for the symposer.

I don't expect I will mess with mine, but FWIW, here is one such kit:

Fabspeed Porsche 718 GT4 / GTS / Spyder Sound Symposer Delete Kit (2020+)
 

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2021 718 Boxster GTS 4.0
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I get that most people don't like it, but I'm not sure what the problem is with Porsche's engineers trying to get you closer to your own engine noises via the symposer? It's not artificial like most cars have nowadays through speakers, it's just an amplifier of sorts to what is actually going on inside the engine bay, right?
It is artificial in an historical sense. Intake sounds on mid engined cars typically originate from the sides of the car in front of the rear wheels--unless things are open with little to no sound suppression. with the sound symposer, It's just coming from the wrong place and quite frankly, irritating. As I said earlier. Some like chocolate, some like vanilla.
 

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It is artificial in an historical sense. Intake sounds on mid engined cars typically originate from the sides of the car in front of the rear wheels--unless things are open with little to no sound suppression. with the sound symposer, It's just coming from the wrong place and quite frankly, irritating. As I said earlier. Some like chocolate, some like vanilla.
True, I will probably feel more in line with your take after I receive my car in a few months and not being able to enjoy the Burmester sound system. I will keep an open mind.
 

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I created a Youtube video inspired by this post by Snrubel. Check it out to learn all about Porsche Cabin Sound Enhancement.
Thanks, excellent video. Thought I would delete the Sound Symposer and reduce some drone. However, the video states the Sound Symposer has no impact on drone. Will probably do it myself, now that I know all that is needed is to plug up from the interior. Unfortunately, this instructional video demonstrates access with a Cayman and accessing the Symposer conduit on a Boxster from the interior requires a different process.

Not sure how different the process is to block the passage from the passenger compartment. Has anyone documented that process in writing or with a video?
 

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Thanks, excellent video. Thought I would delete the Sound Symposer and reduce some drone. However, the video states the Sound Symposer has no impact on drone. Will probably do it myself, now that I know all that is needed is to plug up from the interior. Unfortunately, this instructional video demonstrates access with a Cayman and accessing the Symposer conduit on a Boxster from the interior requires a different process.

Not sure how different the process is to block the passage from the passenger compartment. Has anyone documented that process in writing or with a video?
Of course drone is subjective and maybe you feel like the sounds it makes in the upper register is droney.
The first post in this thread seems to show how it’s done in the Boxter.
 

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Of course drone is subjective and maybe you feel like the sounds it makes in the upper register is droney.
The first post in this thread seems to show how it’s done in the Boxter.
Doh! My apology, I should have reread this thread.
 
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