Posting this for those of you interested in having better bass. I have modelled sub boxes behind the seats but was not satisfied for multiple reasons. So I spent a weekend modeling a new idea.
I apologize for the pictures, better ones to come once everything is buttoned up. The system has the Pioneer DEX P99-RS, Focal subs mids and tweeters, Focal and Sony dedicated amps.

 

Not my sort of thing, but the execution looks excellent. All carbon, or just covered?

You may kill any back-seat passengers if you turn it up

 

Hi Serval,
I think you are on to something.
This is a very creative Idea vs using the floor space or the side furniture in the rear seat by turning the rear deck into a functional acoustic element..
Could the back be enclosed with a forward bass reflex vent to increase efficiency?
Could the tops be angled rearward slightly more to regain some visibility through the rear window and cause the design to look less alternative to the standard rear deck?
Could the idea be expanded to include two-way coaxial speakers for the regular rear channels as well?
Finally, could a bass harmonic recovery digital signal processor (DSP) be used in conjunction with this setup, or even slightly smaller drivers to enhance bass smoothness and reduce the verticality of the fixture required for the drivers?
One such DSP is described in the middle of this page:
https://993servicerepair.blogspot.co...or-993-in.html

Andy

 

"Not my sort of thing, but the execution looks excellent. All carbon, or just covered?
You may kill any back-seat passengers if you turn it up ""


All Carbon, subs are only 6.5 super efficient. All about control not volume

 

Visibility is not impeded in any significant functional way. The enclosure is much smaller that it seems. The box is a sealed design utilizing the irregular space on front of the firewall and top shelf. Taking an inner mold of that space was key, but it was only hard the first time

 

Does the enclosure have sufficient volume to provide low frequencies? FWIW, I have 6" Oz Audio Matrix elite components in my doors. while they are not subwoofers, they get pretty low, to the point I don't feel the need to add a subwoofer. No one ever sits in the back of my car anyway, so if get to that point, I'd probably just use an Audio Innovations box, or something similar. The slim under seat subwoofers also seem promising, anyone have experience with one they recommend?.

The above concept looks great though, how does it sound? Low frequencies are omnidirectional, so the drivers could be reverse mounted also.

 

Agree with this. Just prefer something more stealthy but would love to hear how it sounds.

 

awesome man!

 

As a 90’s high end car audio installer back in the day, if someone would have brought me a 964/ 993 with this install in mind I would have declined in respect of the Porsche Gods. BUT I respect the build and its your car so do what makes it your own.

 

Slight hijack. Has anyone found an active sub that can fit under the driver’s seat? Thanks

 

i'll take my rear footwell subs- and NO to an active under the seat. That would be cool- but probably have zero air movement.

 

just addressing some questions above:

- the install is 100% reversible. The enclosure extends only 8" from the top of the seats, and is curved lower in the middle to reduce visual impact.
- the enclosed volume is within 1% of Focal spec requirements
- I have mid-bass door drivers and tweet separates
- the deck, on top of fitting perfectly with the interior aesthetics, has independent cross-over points for every driver pair (high, mid, mid-bass and bass) IMO best deck on the market
- I tried the box behind the seats solution and as mentioned found it inadequate. I will gloss over space considerations, and just say that the sound is objectively impeded. (both my ears and environmental frequencies measurements)

will post final pictures once the whole interior is done - have more things going on than the sound system

 

I'd like to know what "inadequate" means to the box behind the seats. I have a JL 750 watt, 6 channel amp powering the 2 Focal, 8" subs, 2 A/D/S 2-way plates, 2 Rockford 5" mids on a cross-over to 2 dome tweeters- all driven by a Sony DSP head unit and the sound is incredible. The thump and "feel" into the front seats when you wanna really rock, is more than impressive. Sounds is crystal clear. Frankly, I think the AMP is the key- pure, clean power.

 

I did the following experiment. measured overall frequency response from the driver position with the sub boxes placed behind the seats vs placed on top of the rear shelf (3cm blue stone slab directly on top of the folded rear seats) and it was much flatter when in the latter position . Now, I am sure that with 2 x 8" woofers firing into the back of the seats, you would feel a thump for sure, but the position is compromised, especially since the back of the seat is not rigid. (unless of course you have the subs firing backwards, but then you would need a larger enclosure and it would have to be ported. Try this at home. Move your home theatre subs behind the couch firing into it from 10 cm (4 inches) away. Bass will not be as tight, but the visceral sensation may just move you )) So why do we do that in the car? Only one reason - space, or lack thereof

I am not sure what you mean by "5" mids on a cross-over to 2 dome tweeters", so will assume you mean you have passive cross-overs between the mids and tweeters. If so, that would be at least redundant, since I assume your Sony DSP would be able to set overall cross-over points (active) to ensure seamless transfer of frequency.

Installing sound in a car is by its very nature compromised, so if you're happy with what you have (and you obviously are) then you're already there. I know that Rod Birch at CAI has installed literally thousands of these subs behind the seats boxes, and has delivered awesome systems build around the Kenwood deck, so I do not question that it can sound great. .

But what can I say,.... I think can do better .....

 

AMEN!!!

Clean Power is often overlooked, many look solely at RMS power ratings and disregard THD specs.