VE Drone

[Drizt]

It doesn't matter what fricken brand of exhaust, they all drone at 115hz, some are masked with 2nd, 3rd, 4th harmonic (noise) is all.

It does matter what brand though as they all have differing levels of drone. X-Force drones a lot more than Di Fillipo for instance.

 

[Drizt]

Just downloaded "Speedy Spectrum Analyser" from the 'Play' store.

Next time my wife is driving I'll have a look to see what is going on with my car.

Pir4te, do you have any screen grabs from your analyser with BEFORE and AFTER plots? I'd like to see how effective your Helmoltz resonators have been.

Edit: How bad would you say the X-Force was for drone before you did the Helmholtz resonators? If you have a plot we can look at that would be great.

 

[Not_An_Abba_Fan]

As far as brands and drone goes, have a read of this thread.

 

[PIR4TE]

Pir4te, do you have any screen grabs from your analyser with BEFORE and AFTER plots? I'd like to see how effective your Helmoltz resonators have been.

Yes, good idea, see below.

Edit: How bad would you say the X-Force was for drone before you did the Helmholtz resonators? If you have a plot we can look at that would be great.

Ok all these readings were the Xforce 2.5" with headers with cats (opened up), calibrated iphone mic at head level, driver's seat, just outside of Sydney on good section of Pacific Highway.
At idle:

When idling all the stuff under 100hz is gold, you can see the +30db mid 120hz, about twice as loud as all other engine noise at idle, but no problem sitting still.

@ 100kph:

@ 110kph:

With Helmholtz @ 100:

With Helmholtz @ various high speed cruising:

You will notice on your spectrum analyzer, particularly at WOT, you can push the peak through the exhaust's harmonics.
Here is Helmholtz WOT @ 2375 the start of our intake and exhaust Time-Area (sexy time):

I include this ^^ to illustrate that car still growls and peaks when it is supposed to, without drone. Stealthy yet boring... a sleeper.
Below vid demonstrates my Black Pearl is stock quiet granny-mobile until ya give it her a bootful of alcohol :yarr:
[video=youtube_share;kUuJi3O85hQ]http://youtu.be/kUuJi3O85hQ[/video]

 

[Drizt]

Thanks for posting.

The y axis is belittling the spikes quite a lot though. 40db to 100db would have been fantastic. Going down to -70db just makes the graphs look far flatter than they really are.

No wonder it sounded very drone'y with 30dB peaks. 10db being said to be twice as loud for comparison.

That said, the Holmholtz resonators seem to have done a fantastic job in taming the very droney x-force catback.

 

[PIR4TE]

The y axis is belittling the spikes quite a lot though. 40db to 100db would have been fantastic. Going down to -70db just makes the graphs look far flatter than they really are.

Agreed, at the time though (three years ago) I thought it amazing to even be able to visualise let alone identify the niggling nuance that nobody else seemed to hear or notice at all.
Now I can render audio graphs as overlay on video with peak holds, rpm, vehicle speed, gear, throttle position...
Looking back at what I was trying to do with this basic app I'm amazed at my own forethought to do snapshots and document it at all!

No wonder it sounded very drone'y with 30dB peaks. 10db being said to be twice as loud for comparison.

That said, the Holmholtz resonators seem to have done a fantastic job in taming the very droney x-force catback.

Yeah I'm stoked, -30db is massive, you simply won't believe what difference that makes to the overall driving experience - excellent highway cruiser now.

 

[Drizt]

Agreed, at the time (three years ago) I thought it was amazing to even be able to visualise let alone identify the niggling nuance that nobody else seemed to hear or notice at all.
Now I can render audio graphs as overlay on video with peak holds, rpm, vehicle speed, gear, throttle position...
Looking back at the app I am impressed I had the forethought to do those snapshots and document it at all!



Yeah I'm stoked, -30db is massive, you simply won't believe what difference that makes to the overall driving experience - excellent highway cruiser now.

Thanks again for posting mate.

I'll have a look at mine tomorrow and post back. I will be surprised if mine is as bad as the unaided x force though.

 

[PIR4TE]

Yes will be interesting for sure. Will be surprised if the frequency is different to everyone else's, perhaps levels.
All readings were weighted to 'C', don't know what that is exactly but allowed me more resolution to the lower frequency spectrum.

 

[Drizt]

Compression weighted gives more emphasis to lower freq. A waiting is unrealistic.

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[Drizt]

C weighted. Stupid phone auto correct

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