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      03-17-2012, 09:35 AM   #1
elerner61
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Drives: '07 Z4M Roadster
Join Date: May 2011
Location: Mount Kisco, NY

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Fiinally..almost Done: Full System Upgrade Keeping Navi Head Unit

So this has been a nice, long project. My goal was to do an extensive upgrade of the Top Hifi with Navigation system in my roadster and play with some new car audio technology while still keeping the stock Head Unit and Navi. The new technology in this case is a Digital Signal Processor from JBL called the MS-8.

I used the MS-8 for a couple of reasons. To get around the limitations of the stock Top Hifi amp, it's idea of equalization for the car and restrictions on what speakers (impedance wise) can be used I would need some sort of line output converter to get a clean signal for my "clean sheet" system. My bare minimum requirements were a clean signal and the ability to use the volume control on the OEM head unit. From my research, only JBL, Audison and Alpine units would fill these needs. In the end I went with the MS-8 because it doesn't seem to require extensive (or even much) audio tuning experience. I didn't want to have to start using a real time analyzer to finish the tune (actually that would have been cool, I just no where near have the time). These units do much more than just line output conversion. To briefly summarize, they provide full control of active crossovers for your drivers and amps and tune/equalize/time align your system to your car using an in-car microphone. There's a 270+ page forum thread on the MS-8 that's followed it from development to now (5 yrs).

The project was done in 3 phases:
1. Insert the MS-8 into the bone stock system, running the stock drivers off the amps in the MS-8. No subs; no way those funky oem drivers can run off a non-oem amp. No behind seat mid drivers; those are just silly
2. Swap out the oem drivers for something better, yet still run off the amps in the MS-8 (20 watts/channel)
3. Add an external amp
4. Add subs

One unknown with this project is that my stock subs emitted relatively little sound . Either the stock amp section for the subs is blown (likely and common) or that's how they really sound. I was able to isolate the subs during the phase 1 when they were the only OEM drivers I still had connected to the OEM amp. Strangely, when I faded the HU to the rear there was very little output from the subs. When I faded to the fronts, the subs did play but mostly when the HU volume was medium and higher. Anyway, the "unknown" is that since I thought my sub amp was blown how would I get sub frequencies into the MS-8 as part of my clean signal. I took a gamble that the signal to the front mid-bass (woofers) was not hi-passed and actually had all the low end frequencies I needed. That ended up to be true. I'm only running with signals from the tweets, mids and mid-bass' as my inputs to the MS-8

So...how did it sound?

Phase I: MS-8 Insertion
Wow! A totally new system. The MS-8 tune/time alignment takes a little getting used to in that it creates a front and center sound stage in the middle of the dash board for the vocals. Plenty of volume though and the stock drivers don't sound half bad. Yeah the tweets do still sound kind of harsh, but the mid-bass' have a pretty good bottom end and their 2 ohm resistance doesn't seem to bother the MS-8 amps. They are sometimes boomy, but overall not bad

Phase II: Swap out new drivers- CDT HD 3-way drivers
Unfortunately the limited depth (around 2") of the stock mid's in the doors kept me from installing 4" replacements. I had a 2-way CDT HD set and I picked up a set of ES-3 mid's to use in the doors. Of the three drivers, the mid-bass in the kick panels were drop-ins with only new holes needing to be drilled. To hold the 3" mids in place I fashioned a particle board mount that holds them from behind and the DRT-25 tweets were a tight fit but some plastic nipping here and there did the trick. And the sound....now we're talking! Much smoother across the entire range. No more metallic sounding high end. The bottom end doesn't hit as hard as the OEM drivers, but it's not boomy at all.

Phase 3: Add external amp
I picked up a Class D, 5 channel ARC XDI 805 for a steal of a price. Can't believe how compact it is. And the sound... HOLY CRAP! I forgot how much good amplification does to the bottom end of a system. Can't believe how solid those mid-bass' hit now. I've been using "Aja" from Steely Dan as my initial test cut during the upgrade and now it has really come alive!

Phase 4: Add Subs
Yes folks, the JL 6W6V3 6.5" subs will fit into the stock locations. There is suitable depth for them, no need for a ring behind the drivers to lift them. One tricky part is drilling new mounting holes for the JL drivers. The front of the sub enclosure is closely contoured to the OEM sub driver mounting holes. And the stock grill will fit just fine if you trim two sides of the inside "grill/guide" (a Dremel makes quick work of this). I pulled the stock cushioning and installed sound deadening (RAAMmat). How does it sound? Almost great! I'm still tuning this. It's my first foray working with subs and figuring out where to cross the mid-bass in the fronts with the subs is my current challenge. I started with 80hz and a 24db/oct slope, but that took out the mid-bass in the fronts too much. I'm now crossing at 60hz with a 12db/oct slope and it sounds much better. The ARC amp. has an external sub volume control that I've mounted behind the passenger seat that's really great for on-the-fly adjustment. I'm going to add some fiberfill to the sub enclosures (I think they sound a little harsh still at times, I can sometimes hear them as well as feel them, could be they're still breaking in). But it's amazing to be able to hear and feel the picking of a standup bass on certain songs.

Here are some pictures of the instal (they're a little large, but actually show detail nicely). It's been a real interesting project and I've still got some cable dressing and tuning to finish up!
Attached Images
     

Last edited by elerner61; 03-17-2012 at 09:46 AM..
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