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      10-02-2012, 12:27 AM   #1
VP Electricity
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Drives: E91 XDrive
Join Date: Jan 2008
Location: portland oregon

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F30 audio analysis

Hi, all. I'm an E91 owner and a longtime contributor to the audio sections in the E90 and 1Addicts sections, well before we became a sponsoring Authorized Vendor. This post has nothing to do with selling you anything - we got our first crack at an F30 and we are doing some development work in it, and we thought we'd share some of the results of our testing.

The car we worked on today is an F30 328i Sportline with Premium Sound ("harman/kardon"). In addition, we had a HiFi door mid on order for a long time, and it finally arrived, so we can contrast the differences between hk and HiFi mids a bit.

The system has front mids and tweeters in the doors, a center channel, rear door and rear deck speakers, and woofers under the seat.

Today we looked at:

- The door mids
- The door tweeters
- The signal going to the door speakers
- The underseat woofers
- The signal going to the underseat woofers

Tomorrow we will look at more test results.

Door mids, tweeters, and signal



Well, BMW has changed the door midrange a good bit. Instead of bolting the speaker to the back of the door panel, the speaker actually bolts to the sheet metal - using the entire door as the speaker chamber - and then the front of the speaker mates to the back of the door panel with a gasket.



Since the speaker is bolted into a hole in the sheet metal, it is exposed to water. The hk speaker is made of pretty water-resistant materials (injection-molded frame, synthetic rubber surround, poly cone), and has what looks like a 30mm voice coil (larger than most 4" speakers) The HiFi speaker is made of paper and foam and has a more common 25mm (1-inch) voice coil.

The magnet is right up against the window glass. You might be able to go in another mm, but no more than that.

The speakers which people (including us) have often been using in E90 front doors will NOT fit the F30. The speakers we have been using in the E92 can fit and seal up with some spacer development which we are now working on. Whatever adapter is used needs to both mount the speaker to the BMW mounting holes and act as a spacing gasket against the back of the door panel.

I didn't take pics of the tweeter. The tweeter size is unchanged from the E9x and other BMWs. The odd thing about the hk tweeter is the series capacitor - it's gotten hugely upgraded. It's a 4.7uf mylar job, that quite literally is huge - the largest capacitor I've ever seen on a tweeter in an OEM system, and the first mylar I've noticed. Funny how harman, with all their faith in DSP, has decided to use a more costly part in a crossover filter that actually adds to the bill-of-materials cost. They must really believe it helps.

The electrical signal to the front doors looks like this:



(Please note that this is NOT the acoustic response measured with a microphone - this is the electrical response measured on the speaker wires, with the system playing pink noise and the tone controls and EQ all flat).

There is much more equalization going on than the E9x Premium Sound systems used. The crossover looks to be a bit lower, which I would expect, with the 4" speaker being in the door chamber like this - the upper bass should be better than the E9x cars. With any aftermarket speaker, I would expect the dramatic roller-coaster curve would need to be corrected.


Underseat woofer and signal

The underseat woofers in the F30 are listed in at least instance by BMW as "217mm" speakers where the previous Bangle cars all were using "200mm" speakers. They are the same diameter. However, the magnet on the hk woofer is larger than before, and it uses a 3-inch voice coil (like the E9x Enhanced Premium woofers). Like the EP woofers, the impedance of the underseat woofers is around 7 ohms. The signal to the woofer hits 28V on my meter, which is not a true RMS meter, so it's not as high a peak as the EP system's 36V. Tomorrow I will measure the DC content - I have a strong suspicion that the amp is a Class D and that regular signal-sense devices won't work on the outputs.

The woofer on the left is a Logic 7 woofer, the right is the F30 hk woofer (I don't have an E9x hk woofer from the 2010 audio reintroduction of hk handy).





What I didn't get a good picture of is the decrease in depth. The F30 has a much shallower enclosure than other BMWs we've worked on, and the speaker/spacer combos which have been used in the E9x and the E82, etc., again won't fit, I'm afraid. We are working on some solutions.

The signal to the underseat woofers is also heavily EQd, but it seems to be fixed in EQ curve:



The peak is at 50 cycles, and the curve is 14dB down at 20 cycles, so there is a meaningful subsonic high-pass filter in use. This could limit the performance of a trunk sub connected to this low-passed signal (it probably will, without some kind of correction).

Other notes:

- The door panels are surprisingly lightweight. Unlike the E9x door panels, I highly recommend damping them with something, and we will be including something in our F30 kits.

- The hk amplifier has the external power connector like the EP amps. This is another indication that the amp is a "real" amp, not a BTL amp like the Logic 7 and hk amps were for the E9x and E82.

- For bigger systems, the well in the trunk floor is much easier to get wiring into than the well in a 325/328/330 E9x trunk.

- as we expected, the PnP Premium Sound harness fits the hk amp in the F30.


What we have learned so far

- I don't think anyone is dropping SWS in there anytime soon. I suspect they will hit the bottom of the grille if spaced up enough.

- There are some front and underseat speaker upgrades we will be able to offer very soon after some parts development.

- Many amps will clip on that 28V peak signal to the underseats

- With the heavy-handed EQ, I suspect that simple speaker upgrades won't be effective and corrective processing will be even more important than ever. I would want the DA2 in an HK car for a full system, and I might even want some DSP for a subwoofer add.


Tomorrow - acoustic measurements with a microphone, a cursory look at the center and rears, a closer look at the amp, listening tests, and more.
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