Re: Bob, could you rate the different setups ... (archive)

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: on a scale of 1-100?
Hmmm. Thats hard to do since it is so subjective. If we start by derating the max 100 by 20 points based on the theory that everybody thinks his own setup is better than everybody else thinks, then I'd call the first (Passive crossover 2-way) setup a 70 and the full active setup a 78. However, it's really easy to make the active set-up a 2 with the wrong settings, and its hard to make the passive set up lower than a 60. For the purpose of scale, I'd call the factory BMW system a 40, and a factory Honda Civic system a 50.

How much of a difference does biwiring make compared to a standard setup?

In terms of the basic system sound, not much. What I like about it is that you can fine tune the relative woofer/tweeter levels, where just using the switches in the crossover gives you a comparatively coarse +/- 3dB adjustment. This gives more flexibility in allowing for different woofer and tweeter locations than those which may have been assumed when the speakers were designed.

A _properly set_ active can be cleaner and more dynamic than a typical passive. With a top end speaker like an a/d/s/, Diamond Audio or an MB Quart with the Musicomp crossovers the difference is actually pretty subtile. This is because those crossovers use high quality air core inductors and film capacitors in critical places. With speakers that use Iron-core inductors (IMHO one of the worst sins of compromised speaker designs) like Boston, JBL, et.al. the difference is more significant. The big problem with actives is setting them. The subtle clarity improvements are trivial compared to the not so subtle frequency response errors that will happen if they are not perfectly set.

Not really. In fact, on a strictly sound quality basis, bridging is bad. An unbridged amp is theoretically better, but this is on paper. The difference is so subtle that its audibility is doubtful. The advantage is strictly higher power, and the only time you'll hear a difference is if your power needs exceed the unbridged power, causing the amp to clip for more than a few milliseconds. If the lower power amp doesn't reach maximum power, then there is no prctical advantage to the bridged amp. However, with that said, it's unbelievable how much power is actually used on an instantaneous basis. I read that Bob Carver once demonstrated that it took over 1000W of instantaneous power to accurately reproduce the sound of a pair of scizzors at the same level which occured naturally when using a typical pair of bookshelf speakers of the day! However, again experience shows that this is theoretical, because the distortion which occurs in this example is so instantaneous that it is of negligeable audibility. It is however an interesting fun-fact :-)

: : Because my job (prior to March 1) involved evaluating various new car audio products and systems, I've actually had quite a few configurations of the P840 since it was installed. The configuration I recommend to someone who does not have a full acoustic lab at their disposal like I do is:
: : channels 1/2 to the front (335is) tweeters through the passive (335is) crossovers set to "bi-wire" mode
: : channels 3/4 to the rear (A5is) speakers through the passive crossovers of the (A5is) set for conventional single-amp use.
: : channels 5/6 bridged and 7/8 bridged and sent to the front (335is) woofers through the (335is) passive crossovers.
: : The BMW midranges are left disconnected.
: : The P2110 drives the sub.

: : The actual configuration that I personally like the best, and what I am currently running, is like this:
: : ch 1/2 front a/d/s/ 335is tweeters using the P840's active crossover set around 5kHz.
: : ch 5/6 front BMW midranges, again using the P840's crossover set for a bandpass of approx 2kHz-5kHz
: : ch 7/8 front a/d/s/ 335is woofers set for a low pass of approx 2kHz.
: : ch 3/4 running the rears as above.
: : I say "approx" on the crossover frequencies since the final positions were determined by acoustic measurement and listening, so I don't really know the exact electrical crossover point.
: : The only thing wrong with this combination which makes me hesitate to recommend it universally is that it is very easy to make it sound REALLY BAD with the wrong adjustments! This is where the acoustic lab's measurement equipment comes in really handy.

: : I do not use a box. I have the 310rs running free-air mounted on a wood panel firing through the ski-bag opening. (Remember, this is an E34, not an E39). The low "Q" design of the 310rs lets it be used this way without getting muddy or boomy sounding.

: : : I want to do the upgrade but fear that the door panel's will not seat exactly as they do now - noise free.

: : That should not be a problem if you're careful. BMW assembly methods tend to be pretty well designed and are not as fussy as, say, a Mitsubishi. With reasonable care it should go together well.

: : : I was considering just wiring in a new amp and sub and not replacing the speakers. Does anyone know the max power handling of the stock system's speakers?
: : The Nokias I took out of my car are rated at 40W. Mids and tweeters will handle considerably less, but of course when they are crossed over, they only get a portion of the signal, so even if the amp is rated higher they do not actually get more than a few watts sent to them.

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