johnf95111

In defense of #4, in a purely engineering take it is not a pratical soultion. Adding a series resistor to a coil will de-Q the circuit and half the power will go up in heat if a 2 Ohm series resistor is added; and yes excessive heat from an under rated resistor, in the wrong spot can cause a fire.

If you are trying to adjust one channel and not the other/s for that particular frequency band in a mixed impedance system it does matter which side of the cross over it is put on . Load balancing in a current sense, but the audio balancing will suffer.

The thing I do have issue with is "and just gamble that the new stereo unit can handle the 2 ohm load". How about making sure it can handle the load and not leave it up to the deity de jour?

I'm in the midst of adding a 10" subwoofer to my system and came across this thread in my research.

Cheers,

T_MaX

You can make or buy a spacer to fit speakers in the rear.

I made these out of PVC pipe and plexi-glass. These are 4 inch JL Audio Mid-Bass speakers with a big mag. As you can see from the schem. all speakers run thru cross-overs. If you look around there are good 2 and 4 ohm speaker on the market that will work just fine.

Okv

May be helpful to someone to know that most likely at least some late model 928's have faulty rear speaker crossover wiring - the tweeter and midrange are switched.

During a redesign of the crossover in the rear, I checked this due to information on http://www.nichols.nu/tip512.htm.
And, yes, they are indeed wrong.
The tweeter gets the mid and low range signal, and the midrange gets the tweeter signal.
To fix this, just swap the green and the yellow wires on the output side on the crossover mounted on the rear of the woofer.

This is on a 1991 GT, with the 10-speaker high-end factory Feinschmecker audio system.

Alan

No - As you can see from the schematic they do not. Speakers II are direct from the amp (internal active crossover - as I already noted).

The crossover for the other 2 speakers (III) are actually mounted on to the rear of the woofers but have no electrical connections to the woofers.

Alan

Marine Blue

Plus one. I just had my subs in the rear redone and they sound great! The amp has trouble driving them at really high volumes when the bass is heavy but for rock, pop etc they sound ten times better. I'm going to send my door speakers for refoaming next winter. $73 for the pair including shipping.

76FJ55

With my limited understanding of electronics I'm not sure Porsche is necessarily mixing impedances. In looking at the above diagram is Porsche factory audio designed to run 2 ohm per channel? The realize the initial question was about mixing 2 and 4 ohm speakers, but if the mids and tweets are run in parallel then you would need 4 ohm speakers to generate a 2 ohm load at location I and III, and the subs at II are run straight off the amp at 2 ohms. So to me it looks like that are mixing 2 and 4 ohm speakers but not mixing amplifier loading. Does this make sense or do I misunderstand the system?

borland

That's right. They are mixing 2 and 4 ohm speakers, but on separate channels (6 channel amp). It is desirable to lower impedance because speaker output rises as impedance decreases. Apparently the amp is capable of driving the factory speakers this way and the factory crossovers provide resistors to adjust levels.

Since the factory amp ratings are unknown, its a good reason to eliminate the factory amp when replacing factory speakers with aftermarket rated speakers, because with a rated aftermarket amp, you can be assured that your amp is capable of handling them without damage to the amp.

odurandina

can you all post some pics of any subs, custom subwoofers you've had done ?

blazing928

Well this was my install , but its changing......
This was Rainbow Profi 6.5" kick bass, two Rainbow M100 4" in the door and a Brax HT1 tweeter, running off a Clarion HXD2, [Also Pioneer DVD for the kids] Brax X2000 for the Critical Mass UL12 sub and a Brax X2400 Graphic edition for the front end.
Serious amount Second Skin Audio sound deadening with more to come.
RF 3sixty 2 processor when it comes back from repair.
Brax Multi controller, Optima battery,
back to Bosch 130w alternator after 200amp Alt fried itself, can't run cool enough at low revs, wiring upgrade.

New system...
Brax Graphic Pro 6.5 woofer, Brax Matrix 2.1 mid and Brax Graphic Pro HT1 Tweet running through Matrix 3 way Xovers, same Brax amps and
CM UL12 sub . Brax mid 2.1 & HT1 tweet will be mounted up on the dash

Alan

My subwoofer and I also made spacers to fit replacement speakers in the rear quarterpanels..

Here the spacer rings look to be a different color but they are actually upholsered in black vinyl to match the interior - they only stand out in photos...

Alan