Jehnert Porsche drop in driver review:

I was inspired by Ryem3’s budget audio install thread and started looking at easy, reversible ways to improve the somewhat dismal sound quality of my 997.2 Bose system. I appreciate Conrad taking the time to detail and share his journey upgraded his system with mostly drop in Focal speakers. One of the things that gave me pause however was the fact that I didn’t want to modify the drivers nor the car with anything that was not easily and totally reversible. If I ever install an amp, I want it screwed to an existing bracket or to a part that is easily replaceable to go back to a virgin car in the event of stereo removal or a sale.

This constraint led me to jog my memory and look up Jehnert. I remembered from previous systems that they made many “drop in” systems for European cars. They started by building aftermarket upgrades for Porsche cars. They are actually located in Germany on Porsche drive!

When I went to their site, I saw 3 different offerings for the 997 coupe (they also offer cab and 996 solutions).

Their first choice was a double 6.5 midbass per door enclosure, front 3 way. This option included a custom enclosure that permanently modified the door panels with the new speaker pods. Although once installed it appeared oem, it was not reversible. I didn’t want to go through the expense of finding a Cocoa door panel to replace them in the future, so I looked at their next option.

Their next 997 offering was a rear double 6.5” midbass per side 2 way kit with enclosures and grill. I’m not sure about how reversible that kit is, but it seems to be with the worst case being a replacement interior panel. I skipped this option for now although it may be an option to replace the subwoofer down the road. This brings me to the last setup I looked at:

3 way front separates with an 8” midbass, 4” midrange, 1” tweeter (with pod in matching Porsche leather), and 3 way passive crossovers if used with an aftermarket amp. This setup was a true direct drop in. No drilling, cutting or fabricating what’s so ever. The tweeter pods take the place of the tweeter grills and the grill transfers over. Easily reversible. The 4 inch came with the proper tab configuration for Porsche and was a direct swap. The 8” came with a molded baffle for a direct bolt in to the door and if it performed like it did in their BMW kits, it would have plenty of bass/midbass punch. This was the setup I chose.

 

Install:

Unfortunately, due to work and other commitments I was running short on free time so I had the dealer I ordered it through schedule me for an install. They finished the install late at night on a Saturday to accommodate me for a Sunday morning pickup. Unfortunately this left them with zero time to really listen to or tweak the system (not that there is much to do with the stock Bose controlling things) before I got there, except to verify every speaker was working as it should. They did confirm the ease of the install and the fact that there was no fab work involved.

When I arrived at the shop to pick it up, I sat in my car and auditioned the new speakers with familiar CDs and mp3s.
To say I was shocked would be an understatement. It sounded pretty bad. Not bad enough to think something was broken, but just bad enough to think I really just wasted a good chunk of $$. When I turned it up it sounded even worse, but again, not like there was something broken or installed incorrectly. Distorted, lifeless, etc. It sounded like I either bought crappy speakers or they were not playing nice with the stock Bose head unit and amps.

I was already thinking of the next steps (throw more $$ at it)—aftermarket amps, processor, head unit, etc when it dawned on me to ask: “Did you guys disconnect the center speaker?” Their answer was: “No, we meant to ask you when we spoke yesterday but we got distracted in the conversation.” I asked them to disconnect it.

They disconnected the center channel in about 50 seconds and let me know it was done. I sat back in the car and started auditioning my “go-to” tracks. After about 25 minutes of me sitting in the car listening to music, the installer comes and opens the passenger door to see if it improved and what I was thinking.

I didn't even know I was in the car that long. It sounded completely different and was CRYSTAL clear and balanced. The center channel had been overpowering the new speakers earlier (2 ohm vs 4 ohm) and it sounded horrible until it was disconnected.

I’m not going to get into Stereophile terms like “spacious, palpable, airiness, etc” but let me just say the Jehnerts are a SIGNIFICANT improvement to the Bose speakers and well worth the expense. The level of detail, clarity and balance is impressive. It seemed to tighten up the boomy bass too (stock subwoofer for now). I imagine it has to do with how the sub and midbasses interact at their xover points in the car. Not sure, but the improvement is dramatic. They get stupid loud while maintaining their clarity and composure too.

Again, this was a very tight install window between drop off and pick up and the shop did me a favor by working into the night on a weekend to accommodate my schedule and pick up time requirement. I don’t blame them for not disconnecting the center channel or forgetting to ask me about it. I didn't tell them to disconnect it either, which I easily could have when I dropped it off, and avoided the scare. Lesson learned: disconnect or replace the center channel!

It all ended very well!

 

I guess this also verifies conrands install that the speakers alone would give a good result. My feel is really the concentration of bose was to get volume out of their crappy speakers. With the audio mods suggested we lower the impedance of the speakers thereby lowering output but at the same time lowering distortion resulting to oncreased clarity.

 

Looks good, would this be an easy DIY?

 

I plan to meet up with Conrad one day soon to compare setups. Do you have any pictures of your subwoofer install and wiring?

 

Yes, very easy DIY.

 

Thanks, looks like this will be on my to do list.

 

Stage, i will get a few pics and post. Dont look good but it sure sounds great! Plus, when you listen down low, the highs are clearer with tremendous adjustability of the bass

 

Appreciate it. I'm really interested in how you wired it in.

 

Wiring is the simplest brother. I will attempt to describe though i will still get pics. Pull out the terminal connected to the bose sub. You will see 5 female terminals that connect to the 5 male terminals on the bose. These 5 terminals are plus power, neg power, switch signal, neg audio signal, positive audio signal. Just directly connect these to the corresponding terminals on your powered sub. Thats it! No complexity whatsoever. The bose is simply a powered sunwoofer using speaker outputs.

 

How did you input the audio signal? Speaker input or did you convert to rca?

 

As said bro, all was direct. No conversion or anything like that. Simply connect signal, which are speaker level, into sub speaker level input.

 

Here are some pics of the sub at the back seat

 

And the connection

 

One more