Ok b4 some one says do a search did that all morning.and don slap me just thinkin.But how much of a pain is it to install speakers in the actual doors not the kickers?And noticed in some the 4th gen theres a circut board attached to their door speakers this i assume is to work in conjunction with the head unit as i heard something to that effect.What do these boards do?As i have seen 4 systems like this and each was a bose set up factory and i happen to like the quality sound of most factory bose i was thinkin it has some thing to do like boost or filtering.Wonder what those boards would do on an aftermarket awia or alpine head unit??

 

They are probably crossovers to filter the highs/lows (don't know w/o photo) they are used to seperate the high freq. to pass to tweeters and low freq. to pass to mid/subs. And if they are they would work fine with any unit as long as they were hooked up correctly.

 

No they won't. Any sort of passive filter is going to be specific to the speaker that it was designed for. Every speaker has a different frequency response and a different impedance profile (it's a lot more complex than it's nominal "4 ohm" rating) that is going to react differently with the filter.

Back to the original question about putting speakers in doors. It's been done a million times. There are benefits and drawbacks to it. If you have power windows, your window motor is right behind the door panel at the bottom of the door, so it's necessary to build your door panel out a mile to fit the speaker, which to me, looks stupid. You also have to use a ton of dynamat to get that 4' long liberty bell of a door panel to stop resonating. Moisture will eventually ruin the speaker. Imaging, while better than in the dash, will suffer compared to the kick panel location because your path length isn't as well equalized and because the speakers aren't far enough forward.

The benefit to the doors is that your midbass & bass response will be significantly improved over the kick panel location because it'll give that high Q woofer enough room to breathe. Most car audio woofers are a high Q woofer that is designed specifically for very large enclosures like a door.

 

It's not really that different if you use a different speaker (providing the impedence of the other speaker is the similar). I've been building passive crossover boards since 1994, and the physics of electricity haven't changed yet. It all depends on the impedence of the speaker used on the crossover. A cap will cut low freq when wired in parallel and cut high freq when wired in series. A coil does exactly the opposite. I don't care what speaker you put behind it (again, as long as the impedence of the speakers are the similar), you will get the same results. You are either trying to short the freq you don't want or capacitizing the freq you do want. Just like home speakers with built-in crossovers, you will get the same results on whatever stereo you put them on.

 

The impedance profile of a loudspeaker is far more dynamic than you seem to realize, and there is not always simularity between different units. It's usually different enough to completely throw off the filter. In addition, the frequency response of two different drivers will be different, and since the phase response is a function of frequency response, that will be significantly different as well. Having a different phase means that even if your driver rolloff characteristics behave as you hope they will, the integration between the two drivers will still be screwed up.

I just whipped up a quick example by modifying a file that I had on hand. The first pic is what you get when you just slap the calculated values for an LR2 filter into place. With this particular set of drivers, it works a lot better than I expected, but it's still far from ideal. You can see a big bump in response around the 2khz crossover frequency that will be very audible and will make this speaker sound "shouty". Furthermore, this simplistic filter does nothing to eliminate the upper frequency breakup of the driver at 5khz (you can see the ripple in the woofer response) which will be audible as upper frequency harshness. The generic filter also crosses the tweeter at a lower frequency than planned, which will allow it to play in a region that will create a lot of harshness. Another thing that I didn't show here is that the phase integration is terrible. There's about a 75-110* phase shift between the two drivers at the crossover region, which will result in a very poor integration of the two, especially in the off-axis power response. You will clearly hear a woofer and a tweeter instead of a nicely integrated sound.

The second pic is my early prototype filter for these drivers. You can clearly see that the response is much flatter, and the drivers are better controlled through the crossover region. Reversing the polarity on the tweeter shows a deep null, indicating proper phase alignment through the crossover region. Though it works well on the screen with the infinite-baffle driver responses, in car it still needs a lot of work.

Also, here is a link that does a much better job of describing the difference between a generic filter and a proper one:
http://www.speakerbuilder.net/web_fi.../phat/hpif.htm

 

Oh yeah, I almost forgot. What happens when you change drivers but not the filter?

Here's a plot with my filter and the same woofer, but I changed the tweeter to a different model. Same impedance tweeter. Obviously, you don't get anywhere near the same result.

If it was as easy as just slapping together a crossover that works with any driver, people wouldn't have careers in loudspeaker design. The filter is by far THE most important part of a speaker and has the largest influence on how it will sound. Great drivers with a lousy filter will still sound lousy, and you'd be surprised how good you can make shoddy drivers sound if you are good enough with a filter.

 

Jim85iroc, as I can see there is intelligent life on this planet! I agree with you, put my point is that he can take the Bose system out of another car and use it. Perhaps I don't always take into account that not everyone is a fanatic like us. If I were doing this myself, I would have the Fluke out and the fresh smell of solder in my car. I'm glad you went to the depth that you did, but to the average joe, the filters will do the job. As far as your graphs, how close were the impedence of the various drivers you used? When we built the passive crossovers we would measure the imp. of the driver. Next we would use a graph for the specified frequency gains/losses we needed to obtain a flat response for the environment (in most cases a car). The graph would tell if we needed a cap/coil, and the value. In most cases we ended up needing both and depending how you wired the cap/coil combination it would be a low pass at x freq. or a high pass at y freq.
It's not the dynamics I don't understand, it's communication with the general public. You did a far better job then me explaining,

 

ok so if i understand this all i CAN use the boards from the 4th gen speakers and add em ta (say)my speakers in the dash as long as i read the board (which does have hookups printed on it)and apply power where needed grnd audio in and audio out.however this brings up the audio in question.Would i want to tap the low impedance or high imp out put of my after market system.Or is this a trial and error thing.Maybe i should get the tech specs on that system and those boards.Simple enuff ta do once i grab the boards.

 

Both tweeters were "4 ohm" tweeters, but that doesn't mean that their impedance profile is anything alike. Just measuring the resistance of a driver only gives you the DC resistance, but due to the inductive nature of the driver, it's impedance rises with frequency. The impedance also spikes at the driver resonance, which in the case of a tweeter, causes a significant change in the rolloff characteristics of a typical high-pass circuit unless you incorporate an impedance compensation circuit into the filter. If you don't have measurement equipment that's sophisticated enough to measure the driver's resistance at all frequencies, then you'll never really be able to get the passive filter right.

 

Now your talking. The problem with that is most companies use proprietory parts, or the electronic parts are made specifically for that product. A good example of this is my cordless drill. It has a transistor in the trigger that goes bad quite often. You have to buy the whole switch assembly to get the transistor because it's value isn't one readily available. This happens in audio electronics quite often, and bose is not going to want you to have that info! The best thing for you to do is get the speakers that came with the x-overs and see if you can incorperate them into your car.

 

That's right impedence compensation. I knew there was something I was leaving out, because I know you cant measure a speaker like that. My friend and I are geeks about this stuff (he's more into the cb thing, I like audio). Pink/white noise generators, oscope, fluke meters etc. I even fly R.C. helicopters!
Not to get off sub, I'ts been a while since I used passives. Although the wiring nightmare is reduced quite a bit over electronic x-overs. Not to mention it's a lot easier to get unwanted noise in an elec, unless balanced lines are used.

 

Heavy inta the cb/ham stuff myself.So have some understandin.Unforutnately the speakers are scrap as in shreaded.But should still be able to get basic info off em.Thanx all.3's and 8's.

 

Seeing that they're bose, probly worth having them re-coned (it's inexpensive compared to new ones.

 

when i said shreaded guess that was an understatement.The cones are torn off and the coils so shreded that the (what looks like)copper windings are pulled out like spagetti.