Hidden storage or source of drone

[Artemis]

Originally Posted by Mahlzeit

4. After 7 miles in mid 70s temps, I removed the towel which was noticeably warm.

Might be the right place to keep your hamburger meal warm.

[Mahlzeit]

Originally Posted by Artemis

Might be the right place to keep your hamburger meal warm.

Come to think of it - I'll put my family portion take-out kabob containers back there. Two benefits: keeps the contents from secure,... AND warm. We should send this to lifehacker.com.

[///1M]

Is there any reason why the H/K unit couldn't be relocated to a different place in the trunk?

(To allow both hidden compartments to be sound-insulated).

[ozinaldo]

Originally Posted by ///1M

Is there any reason why the H/K unit couldn't be relocated to a different place in the trunk?

(To allow both hidden compartments to be sound-insulated).

Mine is already located in a different place from the factory, so why not?

Check the detailed info in the old thread about H/K that I gave a link to in one of my previous posts here yesterday. Here:

http://www.1addicts.com/forums/showthread.php?t=489851

Any good Audio shop should be able to do this easily.

[ozinaldo]

Originally Posted by Derek8819

On the older model 1s that is where all the add on modules like satellite radio and Bluetooth were installed, now that is all built into the head unit.

Couldn't take a photo yesterday but in my car H/K ampf. is hidden inside the driver's side rear wheel arch while this cavity is mostly empty. However, there is a unit (little black box, could be bluetooth) and a cable from it getting inside the car from the back of the rear seats.

For specific market requirements, my car's Prof. Radio unit is not with Assist but I do have optional USB plus bluetooth. No nav. system either but I have the H/K. Any idea what that box might be, which kind of explains why I don't have the silver ampf. located in the cavity?

If I ask this to BMW dealer here they might reply if my car is the new 3 series so you got the picture,....any insight is appreciated

[ozinaldo]

For everyone else following this thread because of its link to drone: I made an unplanned experiment yesterday. After checking the cavity for curiosity somehow I could not close the tray (base trunk liner) back perfectly, it was slightly loose from the ends where it meets the back of rear seats, you would not notice it by looking at it; I discovered this later when I stopped. And there was huge drone while driving to my surprise! Then I was at a car wash and when I finished the job I put everything back good and tight, tapped it on top even to make sure and it was back to normal again with minimal drone, almost 0. Check yours carefully and see if that works with stock exhaust as well. Before new exhaust, I always had drone with stock exhaust but never tried filling the cavity with stuff. Obviously even the slightest air trapped inside that area creates drone.

[Artemis]

Originally Posted by ozinaldo

Before new exhaust, I always had drone with stock exhaust but never tried filling the cavity with stuff. Obviously even the slightest air trapped inside that area creates drone.

The 'drone' you hear is actually caused by the snoring of, and farting by, a tiny ///M gremlin who squatted that cavity. Tell him/her to shut up and behave or to leave the premises at once.

[ozinaldo]

Originally Posted by Artemis

The 'drone' you hear is actually caused by the snoring of, and farting by, a tiny ///M gremlin who squatted that cavity. Tell him/her to shut up and behave or to leave the premises at once.

Snoring and/or farting ///M gremlin

[Aussie_in_London]

Originally Posted by ///1M

Is there any reason why the H/K unit couldn't be relocated to a different place in the trunk?

(To allow both hidden compartments to be sound-insulated).

You can still dynomat the area even with the amp present, unbolt the amp carrier, lay the insulation mat and then refit the amp in its rightful place. job done.....

[Amnizu]

Originally Posted by Aussie_in_London

You can still dynomat the area even with the amp present, unbolt the amp carrier, lay the insulation mat and then refit the amp in its rightful place. job done.....

+1. Dynomat/pad and competeing products are designed to be installed under door interior covers and under stock carpets.

[CarJunkie]

Originally Posted by Mahlzeit

NOTE: I will not address this 'issue' because I don't think it's an issue in the first place. I happen to love the rumble, and don't really consider the drone,...drone in the first place. I removed my 'mod' right after pulling up to my home. I find this discovery interesting, but don't plan to take action. I will however consider an N55 midpipe to uncork some performance and make the 1M exhaust awesome-er. Ultimately, I felt disappointed with the muted character....

I agree. I have the HK amp there, but was still able to get the space mostly filled with a towel to test the theory. The drone decreased, but so did all exhaust note into the cabin. Towel removed!

[EldRick]

I used some dynamat in the bottom of both indents on my 1M, and it reduced the drone a bit, and also made it obvious how much softer the exhaust note is once the engine has warmed up.

My all-options 6/11 build car had only the amp in the right-side cavity, and I used dynamat under it, too. The amp carrier plate comes out easily with two nuts at the center, then slide it toward the center to release a couple of metal tabs. I turned it upside down toward the front, and had a clear field to work on the indent beneath it.

Since the left-side indent was empty, I put a couple of layers of carpet scraps there. I've also put LLoyd's Luxe Mats in the trunk and replaced the OEM floor mats. These are 1/2"-deep-pile carpet mats with 1/8" of rubber on the bottom. They fit perfectly and soak up a bit of noise - very luxurious. The Ebony color is a great match for the interior: http://lloydmats.com/mat-materials/l...le-floor-mats/

Next step in my march toward increased quietude will probably be to use the y-resonator from a 135 mid-pipe to turn down the noise level.

[eeghie]

Originally Posted by Aussie_in_London

And what you find in mine....

No biggy, just that right side module (from Aussie's image) in our cars with either Navi and/or HK sound is the so-called COMBOX. The Hifi or HK amplifier is located in the trunk above/behind the left wheel well. This combox provides all kinds of communication (like BT, phone integration, antenna connections, BT audio streaming and USB). In stripper cars any BT and/or USB is integrated in the headunit and thus that trunk underfloor cavity is completely empty like OP's image.

The physics behind acoustics would make any damping material that you realize at the outskirts of an enclosed space most efficient to reduce drone sounds. So any high density foam material that you can stick to the OEM painted outskirts of your trunk (so this empty cavity is quit a big part of that) will help reduce droning.

At the rear side of the E82 to the left and right, underneath the trunk liner there are two other empty resonating spaces. The right side of these cavities would host CA and PDC modules (and AHK and EDC in E92), but can be filled up with HD foam for further damping.

Some of us love all the sounds that the 1M makes, so be careful to first test your damping solutions, you might just miss this part of our analog experience car.

[Artemis]

Originally Posted by eeghie

Some of us love all the sounds that the 1M makes, so be careful to first test your damping solutions, you might just miss this part of our analog experience car.

Then there is also the Active Sound Design for cranking up sounds inside and outside the car:
http://bmwi.bimmerpost.com/forums/sh...28&postcount=1

[EldRick]

Active Sound Design was described in 1951, in a sci-fi story named "The Marching Morons".

Tastes differ. I've never seen any reason why a fast car needs to be loud, I have no reason to advertise, and I prefer music to engine noise. I am going to transplant a 135 mid-resonator into my 1M to reduce the annoying 2-3K rpm drone when just driving around, which is around 95% of my time in the car.

[Artemis]

Originally Posted by EldRick

I am going to transplant a 135 mid-resonator into my 1M to reduce the annoying 2-3K rpm drone when just driving around, which is around 95% of my time in the car.

Save yourself the effort and headache and simply fit an N55 midpipe (significant reduction of drone):
http://www.1addicts.com/forums/showp...0&postcount=10
http://www.1addicts.com/forums/showp...0&postcount=27

[EldRick]

Good links, but I want this car to be sellable in California (someday after they pry it out of my cold dead hands) and thus the cats need to stay there, since they do CARB visual inspections on used-car registrations, and also for whatever muffling effect they provide.
I'll substitute the N55 resonator for the 1M fake resonator and it will appear as factory.

[MDORPHN]

Originally Posted by Artemis

Save yourself the effort and headache and simply fit an N55 midpipe (significant reduction of drone):
http://www.1addicts.com/forums/showp...0&postcount=10
http://www.1addicts.com/forums/showp...0&postcount=27

Though I don't think they'll do much to reduce the resonant drone, aren't the catted 1M mid-pipes likely to reduce noise more than the non-catted N55 mids?

FWIW, I've used both in conjunction with my catless AR downpipes.


Neil

[EldRick]

Yes - lower noise is a secondary reason (for me) to keep the mid-cats. The combination of cats and resonator should be reasonably quiet.

[EldRick]

I haven't installed the 135 mid-pipe yet, but did discover a way to reduce the drone considerably.
The interior rear deck panel, directly beneath the rear window, is composed of some sort of plastic/buffalo-hair composite, much like the trunk floor panel. This stuff is pretty much acoustically transparent and resonant at bass frequencies like the 2K-3K resonance, which you can verify by tapping on it with a fingernail.
Directly below that rear interior deck is an open area in the body sheet metal above the trunk - a hole about 4"x12" centered under the rear deck - see picture. That is where much of the exhaust noise gets into the cabin, through the rear deck.



As an experiment, I cut a piece of scrap carpet, visible in the image, that I was able to slide a few inches into each side and fore and aft of the hole, thus blocking it and providing some damping, and lo and behold, quite a bit less exhaust sound gets into the cabin.
Unfortunately I'm not sure whether blocking this off has any ill effects - maybe overheating a blower for defrost, or blocking airflow through the cabin.
Anyone know what's in there?

[Tom303]

Great discovery. Now I did to give this a try.

[EldRick]

I got the 135 mid-resonator installed today using BMW pipe couplers, as in Dackalone's excellent writeup (and actually using his OEM pipe). Being a good citizen (and wanting the car to be California-salable some day) I kept the 1M cats, and spliced the 135 real-resonator into the system in place of the 1M fake-resonator y-pipe.

Outside sound is affected very little - it is still bassy, robust, and convincing, and the resonator changed it only slightly.

Inside, the exhaust note is a bit quieter at idle and at steady speed, while letting you hear all the lovely mechanical sounds from that sweet six when you use it.

The blatant 1M resonance peaks at 2300 and 2800 are suppressed by about 75%, making the car feel more like a sophisticated BMW and less like a Camaro with lookit-me pipes. I can hear my music while just driving around, and even talk with a passenger without raising our voices much. The car feels much more civilized for daily use without giving up performance, which is what I was seeking.