After two years of half measures and incremental improvement, last week I decided to go all-in for an aftermarket OEM integration unit, and I’m beyond satisfied with the results. OEM integration is a solution for cars like the 221 with complex and deeply integrated infotainment systems that do not play well with normal aftermarket gear. I chose the Audison Prima 8.9. It combines a digital signal processor with an integrated 8 channel power amp. An additional un powered 9th channel is available for a subwoofer and outboard amp. (Hence the “8.9” model designation. Really it’s an 8.1 channel amp.)
The Prima is a great fit for late model Mercedes like the 221 where owners want aftermarket sound but are reluctant to do a “gut job”. It gives you the extra power and sound shaping flexibility of aftermarket signal processors and amps in a compact unit that installs after the factory amp and before the factory speakers. It essentially intercepts the output from the factory amp, cleans it up, fixes the EQ, and sends it along to the factory speakers using the factory speaker wires. (You could of course upgrade the speakers as well but may not feel the need to once the Prima is installed.)
Because the Prima installs very late in the signal chain, all of the car’s COMAND functionality is unchanged.
I decided to use an extra outboard amp to drive the existing factory subwoofer on the rear shelf rather than an aftermarket subwoofer box. While I was prepared to go to a box if necessary, I found the factory sub performed well on its own amp and left it in place. Saved some money and maintained the factory look of the system.
The Prima accepts high level (powered) inputs, which is essential since the factory Harman/Becker amp is fiber optic on the low level side. Great for no noise but impossible to splice into. Taking signal from the high level side is the only option. The Prima drops the incoming voltage back to line level, removes the factory EQ, and then applies a suite of powerful, adjustable signal processing tools. Because the factory amp has a dedicated channel and dedicated wiring for each individual speaker in the car, it just becomes a matter of choosing how to best utilize the Prima’s 8 channels, and routing those channels from the OEM amp’s outputs to the Prima’s inputs, and back from the Prima to the car’s speakers.
Yes, Tons More Volume!
These Go To Eleven!
Clearly owners feel there is a lack of volume in the stock system, since I get that question a lot. The Prima as I have it configured, plus the little 300 watt sub amp, is loud as hell. I’ve played drums in rock bands professionally and for fun since I was 16. Trust me when I tell you I know “loud”. Also, I’m probably half deaf from playing drums and the Prima is still louder than than I’d want to listen to for protracted periods. But the Prima’s real advantage is the digital signal processing and the ability to precisely shape the sound. The power boost is a nice side benefit.
To a certain extent, it’s impossible to get good performance from good speakers without feeding them a decent amount of power, but it’s so easy for manufacturer’s to play with amp wattage specs because that’s all 90% of buyers care about. What matters as well is the speaker’s loads and resistances (measured in ohms), and the speaker’s rated efficiency. For example, as a matter of physics, an amplifier rated at 100 watts per channel into 2 ohms is producing closer to 50 watts per channel into a 4 ohm load (the conventional resistance of automobile speakers) and 25 watts into an 8 ohm load (the conventional resistance of home audio speakers). Likewise, a speaker with a 97db efficiency rating will play louder given the same wattage as one with an 87db rating.
Remember too that an amplifier rated at 100 watts per channel playing at a normal or even moderately loud setting is likely producing less than 40 watts per channel at that volume level.
So try not to get hung up on amplifier wattage as a measure of quality or loudness. An honest 35 watts per channel over 8 channels into a 4 ohm load (the Prima’s rated output) with high efficiency speakers is plenty of power for an environment as small and insulated as a car’s cabin, particularly one like the S/CL.
The Prima comes with several built in, selectable configurations, however Preset 5 works best for the W221. That configuration assigns an independent channel to each of the six front door speakers, and another channel for each two way component set in the rear doors. The OEM subwoofer output gets routed to the Prima’s 9th channel and then to a small sub amplifier. This allows you to use the Prima’s DSP to precisely control the sub,
This configuration leaves the dash center speakers (a midrange and tweeter) and the rear deck midrange surround speakers on the factory amp. They blend perfectly with the Prima’s output, but cannot be controlled individually by the Prima.
I recommend having an authorized Audison retailer handle the installation, because it’s a bear. My shop chose to build a simple amp rack and locate it in the vacant space on the passenger side of the trunk against the rear seatback. The speaker outputs from the OEM amp were cut, new leads soldered on to extend them over to the new amps, and the process was repeated to send the signal back to the car’s speaker leads. They did a first class job and spent a lot of time. Here’s the Prima installed against the rear seatback and the small 300 watt JL sub amp.
The factory amp. The blue wrapped cables are new and carry signal to and from the Prima
Once the trunk liner was reinstalled there was no visible evidence the car had been modded at all.
Now the real fun began. The Prima is configured by connecting a Windows laptop to it via a standard USB cable. The installer routed the USB cable into the cabin between the rear seats in the nook for the armrest, and coiled it up under the cover for the fuse panel that lives in there. A simple 6′ extension cable allows you to sit in the drivers seat to set up the system. The Prima’s Windows software comes with the unit on a CD. The following screen grabs show the settings for each speaker set.
Tuning The 221
There’s some technical stuff that may not be familiar here, however if anyone actually does this mod and wants this tune, the entire configuration can be downloaded from the link at the bottom of this post and you can skip this bit before it causes you to fall asleep.
I start tuning at the bottom, literally, and work my way up, beginning with the bass or “kick” drum. I want ito hear it distinctly rather than it being mixed into a lot of bass and midbass slop, and I want to physically feel it “hit”. Here’s the sub’s tuning. It’s cut off very low at 50hz (meaning nothing over 50hz gets to it) Human hearing begins roughly at 20hz on the low end. A 50hz cut off allows almost nothing but kick drum in the subwoofer. As a result I can keep it very clean, powerful and distinct without boominess. A little EQ to emphasize the “hit”.
Next I want the bass guitar (or low octave keys and synths) to be heard so that I can pick out the actual bass player’s performance in the mix. The front door subwoofers get a band pass filter and play a range between 80hz and 800hz. Some EQ was used to beef up the 50hz to 200hz range. Although the 50hz range is actually below the 80hz the band pass filter is set to, there is a 12db roll off between bands so some lower stuff does sneak in there.
The rear doors are actually the only “full range” speakers in the car, but I just wanted them mainly for midbass reinforcement. They start out fairly low at 100hz and play all the way up to 20,000 htz (the theoretical high frequency limit of human hearing) but they’re equalized to push the midbass and kill most of the mids and highs. I could have cut them off on the high end way sooner but I want a little bit out of the tweeters for ambiance.
Between the rear deck sub, the front door subs and the rear door components the bottom end is taken care of. Next is the midrange.
The midrange is where most of the melodic instruments (guitar, keys etc) and vocals are. If it’s not represented well, performances will sound flat and lifeless. If it’s too hot, the lead guitar, horns, higher octave synth and vocals will sound brassy and harsh. Because of the limit on available powered channels, four speakers bypass the Prima and remain on the factory amp (a mid and a tweet in the dash, two 4″ mids on the rear shelf.)All of those speakers play in the midrange. Those 4 speakers form the surround circuit for the Logic 7 multichannel synthesizer. With Logic 7 activated in surround mode, signal is boosted to the center dash and rear surrounds. This brightens up the mids and also lifts the soundstage, so there is already plenty of mid in the car by design and it became more an issue of controlling it.
The mids in the front doors are band pass filtered from a relatively high 800hz right up to the 3000hz point, where the tweeters begin, but their volume level is decreased by -7.5db. That gave me the presence I was looking for but the 7.5db attenuation pushed the harshness down.
The tweeters pick up everything north of 3000 hz up to 20000 hz. I have Focal tweeters that are a little aggressive so they’re pushed down 3db as well. The tweets are almost all cymbal sound.
When I’m fine tuning my logical frame of reference is the drum performance, since I know what drums sound like live and in the studio. It actually works out, since drums have the greatest dynamic range (soft vs loud) and they play across the frequency spectrum with the bass drum at the low end and the cymbals at the high, with the snare and toms filling out what’s in between. I’ve found that once the drums are “right”, the other instruments also sound right as well.
This was the astonishing transformation I’d been looking for. Plays very loud and very clean with lots of low end grunt, beautiful midrange and high end detail and a wide sound stage. I have to credit the Focal KRS100 components for the overall quality of the midrange and highs. At $750 they should sound good, but I’m glad I spent the money. Most surprising was how well the Hertz DSK 653 two way components ($79 set) sounded on the Prima. In the stock set up the rear door speakers get relatively little signal and I didn’t want to spend a ton on them. But on the Prima, where they can be set for a full range signal and full power, they contribute a lot of the clean, smooth midbass I was hoping for.
The three orphaned speakers…a 4″ midrange and 2″ tweeter on the dash, plus two more 4″ midrange speakers on the rear deck, remain on the stock amp so they’re only affected tonally by the bass/treble controls in COMAND. Still, they blend in perfectly. I use the Logic 7 fake surround mode because it pushes more signal to the center dash and rear deck speakers, which lifts the soundstage from down low on the doors where the main 4″ speakers live to up on the dash where it belongs.
My custom Prima configuration file for download. Saves you having to play with all those buttons and sliders:
Prima Config For W221
Some handy PDF’s:
The Audison Prima 8.9 Users Manual: ap8.9_bit_user_manual
The 221’s Speaker Wiring color codes and schematic:Wiring diagram of loudspeakers
Prima 8.9, $900, JL sub amp, $350, Install and materials $600.
Previous upgrades: Focal KRS100 speakers $650, Hertz 6.5 components, $79, MTX 4″ coaxials $50, Hushmat sound deadening and labor $500. Scroll to the bottom of this blog for details on the speaker upgrades.
1) Just do the Prima and leave the factory speakers in place. The Prima has more than enough processing power to get good results from the factory speakers. Had I done the Prima first, I may not have done the speaker upgrades.
2) Do speaker upgrades using less expensive speakers. Here’s a write up on some bench testing I did comparing the OEM Harman speaker with very inexpensive off brand speakers:
A couple weeks ago I was browsing a wholesale speaker component catalog (what can I tell you…I’m not a big sports guy and I need something to read in the crapper when my wife throws away the Victoria’s Secret catalogues) and I came across the Goldwood GW-204 4″ woofer. Goldwood typically makes 8 ohm drivers for home speaker building, but the 204 is a 4 ohm version, which is the standard for car audio.
As you can see, the Goldwood is quite a bit heftier than the stock Harman 4″, with a huge shielded magnet and motor assembly. Some of that heft is actually the shielding but overall it’s quite a bit more robust. But the best part is that the speaker cone on the Goldwood is conventional treated paper while the Harman is a plastic coated aluminum material Harman calls “Alumaprene”. The metal cone material is why the Harman system sounds as thin and harsh as it does. There are five 4″ Alumaprene speakers, and two 6.5″ Alumaprene speakers in the W221.
I went ahead and ordered one and did a quick A/B listening test, adding a 1″ silk dome tweeter to replicate the set-up in the front doors of the 221. My concern was that the much heartier Goldwood would be a power hog, but it was fine, taking only a little more volume than the Harman. It sounds warm, full and even develops a bit of midbass where the Harman bottoms out and distorts. Paired with the tweeter it sounded great. I wouldn’t hesitate to install the Goldwoods in my car.
Mounting wise I tested the depth in my spare 221 front door module and it’s fine. The Goldwoods (and every replacement 4″ including my Focals) have a square 4 hole mount, where the stock speaker is a 3 hole triangular mount. You’d need to Dremmel off two of the mounting ears, like so:
Goldwood on left.
Now the price. Understand that Goldwood has no marketing expense at all. They don’t have the hype of a name like “Bose” or “Harman/Kardon” where they could charge exorbitant prices for otherwise cheaply made components.
The Goldwoods are $22.56. For a pair. If you want to buy four and replace the two surround speakers on the rear deck, the per unit price drops to $10.19.
Here’s a matching set of 6.5’s for the W221 rear doors, $46.20 for the set.