# 2008 SL550 stealth SQ system



## VP Electricity (Apr 11, 2009)

The 2008 SL (R230 platform) is one of those Inspector gadget convertible-hardtops with no trunk space. 

We were asked to:

*Upgrade the COMAND nav* to a modern system, but keep it looking as stock as possible. We were specifically asked to not use any of the off-the-shelf installation kits. 

*Upgrade the sound* - to something that sounded good top up or down.

*Not touch the trunk* - needed the space.

So, here's a stock SL cabin:










Tom decided to use the silver-band accent line element in the installation.

*System design*

We went with the Alpine 927 nav system. It has a UI for grownups, it looks good in Euro cars, it sounds good, and it has good (not GREAT, but good) DSP acoustic tuning options. Sat radio was added by request. 

The head unit has two-way crossover settings, with separate front and rear time-domain correction delay settings. We used the F outputs for the tweeter signal and the R outputs for the midwoofer signal. This gave us control of the time delay for each speaker, with three presets, and also gave us a 9-band parametric EQ. It's not nearly as flexible as an outboard processor, but we didn't really have the room or the budget for the outboard processor (we proposed one, but we were asked to go without it). 

We sent those two sets of signals to an Arc Audio KS125.4 Mini. We spent $100 to have Arc modify that amp's standard crossover with a X10 mod, and we used the amp crossover for the tweeter high-pass/midrange low-pass crossover handoff. We set the crossover settings on the bench using pink noise and an RTA before the amp was installed. 

We sent the sub signal to a KS500.1 sub amp. 

The mids and tweeters were Illusion Audio Carbon 6 components. The SL doors are notably shallow, and we needed a high-performance speaker that could fit. 

For the sub, we used the Illusion Carbon 10 in the footwell of the passenger side, firing forward and using the footwell as a horn. 


*Head Unit*

Tom started by building a solid mount bracket for the head unit and mounting it solidly, but recessed into the dash:










Then he started making the bezel:






















































Then he assembled it:











*Amplifiers*

There is a cubby behind the driver's seat where the stock CD changer was. We were removing that anyway. 



















































































*Tweeters and midwoofers*

If you look at the "before" pic above, you'll notice there are no tweeters in the stock system. Bose used a 4" down low in its own enclosure, and depended on it to play all the treble notes. We left that 4" in place, but it's not doing anything (it's isolated from the midwoofer):










So, we used a crossover point of 2600 (the Carbon tweeters are chamnbered and can play down to 2000) and but the tweeters in the Geddes-approved mirror-sail location, close to perfectly on-axis:
































































*Subwoofer*

We seem to have lost the pics of the enclosure fab! It's a sealed enclosure, and this is what it looks like now:










*Final pics*































































*Sound*

Well, it sounded stupendous. The Illusion tweeters did their job amazingly well. They could play detail up high without sibilance on vocals or ringing on piano notes so common with metal designs. The midbass was very good. The acoustic tuning in the head unit's DSP section let us create a strong, high vocal image, but we still had good stage width and god placement between the A-pillars of the various performers on the track. 

The Carbon 10 has gobs of low end. We only were giving it 350W, and it could outpace the front end if asked. 

The Alpine let us do things that usually require a standalone processor or a Pioneer non-nav head unit. 

We pre-set the time settings for driver, passenger, and averaged, as well as the EQ for top-up and top-down curves. 

We lost no storage space (remember, the CD changer was in the amp location before, so we actually added storage space). 

Customer was very happy, and customer's wife said she was surprised at the results we got with 5 speakers and 2 tiny amps.


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## IBcivic (Jan 6, 2009)

Beautiful, clean installation! :thumbsup:


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## timbo2 (Apr 25, 2009)

Great clean work! Well done.


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## Coppertone (Oct 4, 2011)

You guys knocked this out of the box, bravo. I do have one question, if the customer had agreed to using a DSP, which one would you have integrated ?


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## rugdnit (Dec 24, 2007)

The Illusion C10 can definitely get down. I was shocked with I heard the one Bing did in the BMW. Nice work guys!


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## VP Electricity (Apr 11, 2009)

Coppertone said:


> You guys knocked this out of the box, bravo. I do have one question, if the customer had agreed to using a DSP, which one would you have integrated ?


We use a number regularly - the one I like for convertibles is the Mosconi 4to6, with the 4-position rotary switch to step through the presets. Then I can tune one preset for driver's seat top down, one for driver top up, one for both seats averaged top down, and one for both seats top up. 

But the differences among them are less than their similarities. We've worked with the Bits, the MS-8, the 360.3, and we currently use the Mosconi, the 2013 Helix DSP, the Alpine H800, and the Mosconis, as well as the Arc PS8.


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## fast94tracer (Jun 23, 2013)

looks great!!!


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## [email protected] (Nov 7, 2010)

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Don't forget that name! This dude is AWESOME!


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## BlueAc (May 19, 2007)

Nice work...


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## jpeezy (Feb 5, 2012)

hope the customer appreciated the fine job you guys did half as much as we did here! Nice work,especially like the dash kit (lot of work!) i know what a pain in the ass those cars can be,good job!


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## offbrandracing (May 29, 2013)

Looks great. Did you make those tweeter pods from scratch or modify the factory ones to work? Also is you foot well sub fiberglassed in?


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## VP Electricity (Apr 11, 2009)

There are no factory tweeters in the car. Fabricated from scratch. 

Some glass and some wood.


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## offbrandracing (May 29, 2013)

Would you be willing to make me a pair? I could use a set for my upcoming install in DFW.


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## AzzurriAudioworks (Dec 28, 2011)

I'm in awe of the fab work, especially the head unit trim. Your attention to detail is unreal.


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## VP Electricity (Apr 11, 2009)

offbrandracing said:


> Would you be willing to make me a pair? I could use a set for my upcoming install in DFW.


Sure. Just ship the car over.


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## Angrywhopper (Jan 20, 2010)

Omg.. That dash kit is gorgeous. That type of work deserves a reward.


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## Angrywhopper (Jan 20, 2010)

Double post


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## kustomkaraudio (Jun 20, 2009)

Love the dash kit !!! The rest of the install looks very nice as well. Kudo's on a great job.


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