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HW
12-08-2003, 12:17 PM
anyone replaced just the tweeters in their car? worthwhile? which model? does the oem tweeters have some oddball impedance (ohm) rating? :dunno: one of mine is blown and it's $70cdn for the part so i'm thinking upgrade both tweeters. or is it better to go w/ the whole front set. :dunno:

if i were to replace the front set, are there components that would work well w/o using the crossovers that come w/ the aftermarket speakers?

Kaz
12-08-2003, 12:50 PM
With the work I've been doing with the stereo recently, I've decided that a straight tweeter upgrade might actually be feasible, and might actually make the stock system sound pretty decent, since the highs seem to be a pretty deficient area. Now, I don't know how easy this would be on a coupe, since it seems there is a little bit less space in that tweet/mid pod, compared to the sedan that has a whole separate tweeter pod with plenty of room.

There is an active crossover in the amp already so all you need are a pair of tweeters. No idea what the highpass frequency is, but I'm sure it's high enough since there is a midrange there too. If I had to guess, I'd say it's crossed over somewhere between 4-6kHz. Good aftermarket tweeters are good to 2.5k or so, so that's fine too.

The sedan tweeters are 8ohm, so we could assume the coupe ones are the same. That works out well since many aftermarket tweeters are 8ohm (even tweeters in separates are often 8ohm. The passive crossover's impedance correction network shows 4ohm to the amp).

Right now, I'm in the middle of a stereo re-do, and am temporarily running a set of Focal separates off the stock amp. The highs sound decent but there isn't very much from the midrange down, and the woofer plays way too quietly since the original one was a 2ohm.

Now, I have a pair of stock sedan tweeters that you could take apart to put in the coupe pods if you don't want to experiment, but otherwise I think a little experimentation might be worthwhile. I know of a really small 8ohm tweeter that might work for this purpose. The Audax TM010A39 looks like it might work.

HW
12-08-2003, 01:07 PM
awesome! :D :thumbup: thanks a bunch for the info. i've seen pix of the coupe tweeter pod floating around so i have some idea. also i have the cdn 6 speaker system (no-hifi no hk) so i may have more space to work w/. i just gotta look for some decently priced ones that are 1" dia.
as for mounting, i could go w/ silicon or homemade custom bracket.

re: 2ohm drivers seem tough to find :( if i were to get new drivers as well. :tsk: most aftermarket are 4ohms no?

....

Kaz
12-08-2003, 01:24 PM
awesome! :D :thumbup: thanks a bunch for the info. i've seen pix of the coupe tweeter pod floating around so i have some idea. also i have the cdn 6 speaker system (no-hifi no hk) so i may have more space to work w/. i just gotta look for some decently priced ones that are 1" dia.
as for mounting, i could go w/ silicon or homemade custom bracket.

re: 2ohm drivers seem tough to find :( if i were to get new drivers as well. :tsk: most aftermarket are 4ohms no?

Hmm, I don't know how the 6-speaker system is set up so it may be easier or harder to work with. You'll definitely need to look at the drivers and see what you've got.

Keep in mind that most tweeters are spec'd as '1 inch' but have much larger chassis. The reason I suggested that particular Audax is that it's really small overall.

Kaz
12-08-2003, 02:17 PM
the 6 speaker system is has 4 front and 2 back. no mids in the front and no rear tweeters. although i would like to find out if there is wiring back there for tweeters or biamp coax's.

Interesting. I'd bet the woofers are the same as the 10-speaker, but the tweeters are probably slightly larger and have a wider bandwidth. I have a suspicion they're probably also not 8ohm.

You don't want highs in the back so I wouldn't bother screwing around back there.

HW
12-08-2003, 02:31 PM
Hmm, I don't know how the 6-speaker system is set up so it may be easier or harder to work with. You'll definitely need to look at the drivers and see what you've got.

Keep in mind that most tweeters are spec'd as '1 inch' but have much larger chassis. The reason I suggested that particular Audax is that it's really small overall.

the 6 speaker system has 4 front and 2 back. no mids in the front and no rear tweeters. although i would like to find out if there is wiring back there for tweeters or biamp coax's.

HW
12-09-2003, 02:40 PM
:confused: i just checked the tweeter again and turned up the volume. it appears that there is sound coming from it but just less than the right side. HU problem? or still tweeter? :confused:

Kaz
12-09-2003, 02:45 PM
:confused: i just checked the tweeter again and turned up the volume. it appears that there is sound coming from it but just less than the right side. HU problem? or still tweeter? :confused:

Couldn't say without knowing how the rest of the system works but it sounds like a speaker problem to me.

HW
12-09-2003, 06:45 PM
Couldn't say without knowing how the rest of the system works but it sounds like a speaker problem to me.

oh well, i guess i'll be diagnosing this tonight w/ the door panel off. :( :eek:

HW
12-10-2003, 11:08 AM
well, i opened up the door to peek at what's going on. the tweeter is working but just not as loud as other one. :confused: :( however, i did find some interesting things about the 6-speaker coupe system. there are only 2 wires going to both tweeters and driver :yikes: meaning that the signal going to the door is full spectrum. which is good and bad. good for putting in new speakers. blah :tsk: if you were expecting more from your bmw 6-speaker system. the drivers are 4ohms and made by "haes" :dunno: , the tweeters are 8ohms and appears to have a plastic dome diaphram. the "crossover" was a measured 7uF (probably 6.8uF +/- 10% :dunno: ) electrolytic (bipolar?) capacitor. i couldn't read the values on the cap because it was covered w/ black heat shrink. the cap was in series with the tweeter for a 1st order hi-pass frequency response (-6dB/octave cuttoff). the rears were the same 4ohm "haes" 160mm drivers. the 3 tabbed proprietary speaker mounts were present. the screw was bigger than my torx20 so i couldn't remove the driver. they are part of the plastic driver basket and not removable. the mount for the tweeters were not angled like those of the other systems that i saw posted on the 'net. there is a big empty space where the mids would have been so it appear like this same bracket is used for the 10 speaker system as well which means that if i remove the cutout, i may be able to put in any sized aftermarket tweeter.

it would appear that the combined impedence of the 2-way fronts would be ~2.7ohms but the rears are still just 4ohms. my question now is that if i were to upgrade, would i be getting less power from the HU if i put in aftermarket 4 ohm 2-way components? when the aftermarket rate their speakers as 4 ohm, do they mean the combined? or should i be looking for single 4 ohm drivers and 8 ohm tweeters and use a cap for the crossover. i would like to look into some half decent 2-ways w/ the crossovers in a box deals. the problem i see is that if the aftermarket speakers are 4 ohms combined, i would be getting less power going into the front drivers than the rear fill drivers and that would wrong. :confused: :dunno: then i would have to upgrade the rears w/ aftermarket 2-ways as well to balance it out. i could play w/ the fader but i prefer to have it set to the middle.

Kaz
12-10-2003, 02:02 PM
Ooh! This actually sounds like good news! Full-range signal in the wires is always a good thing, as that gives you lots of options for feeding amps, running crossovers, etc.

Feel free to e-mail me if you want to work on this further, but to answer some questions:

Sounds like you have some understanding of passive crossovers, as a single bipolar cap will provide a 1st-order highpass crossover. I've worked on OE systems that don't even have a cap and fully rely on the drivers' natural rolloff (which is only being used on the woofers here).

I think your options are pretty wide open in terms of where you want to go with this.

HW
12-12-2003, 12:22 AM
looking for 8-ohm component tweeters. who makes them? i've only found one that are made by boston acoustics :dunno:

Kaz
12-12-2003, 12:30 AM
looking for 8-ohm component tweeters. who makes them? i've only found one that are made by boston acoustics :dunno:

You need to check speaker-building sources like Madisound or Solen or something. Most of their stuff is for home speaker building but there are also drivers suitable for (or made for) car use (like that Audax). The pair of Vifa D25AC-05 I got for my project are 6ohm.

HW
12-12-2003, 11:10 AM
You need to check speaker-building sources like Madisound or Solen or something. Most of their stuff is for home speaker building but there are also drivers suitable for (or made for) car use (like that Audax). The pair of Vifa D25AC-05 I got for my project are 6ohm.

are there any things distinguishing a car tweeter from a home speaker tweeter other than the mount? or impedance as well?

Kaz
12-12-2003, 01:14 PM
are there any things distinguishing a car tweeter from a home speaker tweeter other than the mount? or impedance as well?

Well, there are the physical characteristics of course. Mostly the differences have to do with response curves and dispersion patterns. A home driver will be tuned with the knowledge that there will be a finite baffle that it'll be mounted to, and that it'll be playing into a room. Who knows what a car tweeter would be mounted to, and it will also be playing into a much smaller area. And because of that, car tweeters are typically made to have better off-axis response since you're likely not going to be sitting in front of them.

HW
12-13-2003, 01:07 AM
some pictures of the coupe door speakers if anyone is interested. note the black heat shrink around the tweeter wire. the 6.8uF cap is inside. it looks like i can may put new tweeters in either behind the original small circle and bigger circle. maybe cut a piece of mdf the same size as the original tweeter bracket and cut an angled hole in the mdf so that the tweeters go inside the hole and point towards the driver/pass. :dunno:

Kaz
12-13-2003, 02:00 AM
Hmm, interesting... So it looks like the tweeter plugs into one side of the woofer and the car feed plugs into the other side?

The 2ohm woofer out of my car has a completely different connector arrangement.

HW
12-13-2003, 02:30 AM
Hmm, interesting... So it looks like the tweeter plugs into one side of the woofer and the car feed plugs into the other side?

The 2ohm woofer out of my car has a completely different connector arrangement.

not quite. there are actually 2 slots on the opposite side. the one in the front of the picture is not used.

E46CollegePunk
12-17-2003, 08:50 AM
damn. you guys have a lot of fun with this stuff... I have the H/K and all my speakers, save for the OEM subs, are 3ohm.... Direct replacement of everything for Boston Acoustic Z6s and Z tweeters in the rear, with JL Stealthboxes :D

HW
12-17-2003, 10:49 AM
damn. you guys have a lot of fun with this stuff... I have the H/K and all my speakers, save for the OEM subs, are 3ohm.... Direct replacement of everything for Boston Acoustic Z6s and Z tweeters in the rear, with JL Stealthboxes :D

:yikes: :( i don't think i'm about to spend 1k on a pair of speakers. i take it you had to get an amp to run those. those z6's are spec'd for 100W to 200W. so do those z6's fit exactly w/ custom mounts? i noticed that they have those 3 mounting tabs similar to the e46 mid/bass drivers.

E46CollegePunk
12-17-2003, 10:58 AM
yes, the Z6 woofers fit almost perfectly... as far as another amp, im using the factory H/K amp for now.. not the best sound, but same volume levels and MAJOR improvement.. instead of maxing out the speakers, the amp is now maxed out.. not going to blow, but not going to ever sound the best.


And working for a dealer, employee accomodations from Boston Acoustics helped :D

Kaz
12-17-2003, 11:00 AM
yes, the Z6 woofers fit almost perfectly... as far as another amp, im using the factory H/K amp for now.. not the best sound, but same volume levels and MAJOR improvement.. instead of maxing out the speakers, the amp is now maxed out.. not going to blow, but not going to ever sound the best.


Did you find a way to reverse-engineer and redo the crossover points and relative sensitivities of each channel in the HK amp or did you just slap the drivers in without bothering?

E46CollegePunk
12-17-2003, 11:01 AM
straight replaced them.. when i do a new amp, I'll redo the crossovers and wiring... but for now, I just wanted an improvement, and was more than happy

HW
12-17-2003, 11:35 AM
got pictures? :D

did you do the bi-amp setup direct from drivers to HK amp and skipped the BA crossovers? what are the impedences for the individual (mid/bass and tweeter) Z6 drivers? are they the same as the factory HK? :dunno:

maxing out the HK amp? :eek: hows the distortion on that? i take it that you have to crank up the volume knob higher than previously to get the same volume?

Kaz
12-17-2003, 11:55 AM
There's a line you need to tread between 'better' and 'good.' Its easy to be better than stock. As of right now I have stock rear tweeters, HK rear woofers, and Focal 150KS separates without their crossovers in front running on the stock tweeter and woofer connections. Yes, it sounds better than stock, but it sounds far from good. The front tweeter is a LOT louder than the woofer, and all midrange (I'd say from 4khz down to maybe 500Hz) is coming from the back of the car. It won't sound 'good' until I at least have my p840 amp in and set the crossover and levels.

SAB30
12-17-2003, 03:17 PM
The front tweeter is a LOT louder than the woofer, and all midrange (I'd say from 4khz down to maybe 500Hz) is coming from the back of the car. It won't sound 'good' until I at least have my p840 amp in and set the crossover and levels.

Kaz,

I am a little new to this, but in a similar situation on the screamin' tweeter. I just bought a 328Ci and started the upgrade, first step is a set of B/A Pros I have had sitting around for a couple of years. Much to my surprise when I couldn't find any external crossover and saw the mixed impedence on the speakers.

My understanding is that the factory mid signal has no upper crossover point, just the natural roll-off of the stock speaker. That being the case, I connected my B/A tweeter to the mid, so I pick up a little lower frequency than in the B/A cross-over would allow, but leaves less of a gap in frequency than if I pulled in the factory signal for the tweeter which has a higher cross-over point.

So now I have 4 ohm tweeters on an 8 ohm signal, and 4 ohm drivers on a 2 ohm signal. Little 4 ohm resistors in parralel or series will correct my impedence problem and the amp will be none the wiser and think I am still running an 8 ohm tweet and a 2 ohm driver.

Of course all subject to field testing. I should receive the 4 ohm resistors later this week and hope to install them over the weekend.

SAB30

Kaz
12-17-2003, 04:09 PM
My understanding is that the factory mid signal has no upper crossover point, just the natural roll-off of the stock speaker. That being the case, I connected my B/A tweeter to the mid, so I pick up a little lower frequency than in the B/A cross-over would allow, but leaves less of a gap in frequency than if I pulled in the factory signal for the tweeter which has a higher cross-over point.

So now I have 4 ohm tweeters on an 8 ohm signal, and 4 ohm drivers on a 2 ohm signal. Little 4 ohm resistors in parralel or series will correct my impedence problem and the amp will be none the wiser and think I am still running an 8 ohm tweet and a 2 ohm driver.


Hmm, when I had 2 different amps open, it looked like each channel had some sort of circuitry on it, but with an active crossover, it's hard to say whether it was highpass, lowpass or bandpass. That said, I did find it odd that there were 3 inductors (lowpass) inside. :dunno: If you do seem to be getting a lowpass only signal out of the mid wiring, that makes this all the more easier, and your method makes a lot of sense.

Now, in terms of impedance matching, it's not as critical or exact as it might seem. The signal isn't tied to any impedance. The impedance that the particular amp channel 'sees' determines how much voltage gets sent to the driver, thus determining how loud it gets. Also, not every speaker gets to the same volume with the same power input (that's what sensitivity specs are for). It's entirely possible for a 8ohm driver to play louder than a 2ohm running off the same amp. Also, since component sets are made to show a 4ohm nominal impedance to the amp, the drivers separately may or may not be 4ohm. You'll want to check the specs of each driver. If you have access to an RTA or a frequency sweep signal and a SPL meter you could use that to see if you're getting relatively even output from the woofer and tweeter and use the resistors to pad the louder one down or something.

See, this is all such a PITA, that's why I decided to redo everything from the amp out.

SAB30
12-17-2003, 04:35 PM
See, this is all such a PITA, that's why I decided to redo everything from the amp out.

Yeah, I agree on the PITA part and within the next couple of months will replace everything from the amp out too, but for now the cash account is a little low so I'm going in steps.

I have an spl meter, and the tweeters are louder than the driver. I might be able to get my hands on a signal sweep. I'll let you know how I make out with the resistors.

SAB30

HW
12-17-2003, 06:03 PM
SAB: re: connecting the tweeters to the amp mid. if you suspect that original mids were using the natural rolloff of the mid drivers, i'd put a cap in series to filter the lows because those lows could hurt the tweeters (?) they're not designed for big excursions. :eek: also if the amp mid outs are bandpassed, then you're losing the highs.

re: tweeters: you're putting twice as much power to your 4ohm tweeters than before if the original speakers were 8ohms
re: mid/bass: you're putting half as much power to your 4ohm mids than before if the originals were 2 ohm

adding power resistors to your system may help to preserve your equipment but you're loosing amp power through them. P=(I^2)*R (in series) or P=(V^2)/R (in parallel).

speaker impedence also depends on the frequency being fed in.
in s (s=2*pi*freq*j) parameters: impedence = Rdc + s*H

kaz: got pix of the opened amps? :D

re: amp output voltage: i think the amp voltage (while operating in the linear region) is only dependent on the volume knob. it's the current that's dependent on the impedence and voltage. which is why i think you get only half of the original power if you double the impedence.
at least that's my simplistic view of it :p

SAB30
12-17-2003, 06:24 PM
HW,

All good points. At the moment I am driving in silence, well, at least no tunes intall I get the added parts and do some more research.

Do you know what the cross over point for the factory mids is?

If I use resistors so the amp thinks it still drives 8 ohm tweets and 2 ohm drivers what is the issue? The load should be the same on the amp, no?

This was suppose to be a slow, "cost effective", incremental process, the more I think about it and learn, the more I just want to do it now. I have a nice home theater at home, and used to have a nice system two vehicles ago. Made the mistake of throwing in a CD I used to listen to in my old car audio system into my BMW, and oh boy don't I miss a nice system in my car.

sab30

HW
12-17-2003, 06:48 PM
Do you know what the cross over point for the factory mids is?

If I use resistors so the amp thinks it still drives 8 ohm tweets and 2 ohm drivers what is the issue? The load should be the same on the amp, no?

This was suppose to be a slow, "cost effective", incremental process, the more I think about it and learn, the more I just want to do it now. I have a nice home theater at home, and used to have a nice system two vehicles ago. Made the mistake of throwing in a CD I used to listen to in my old car audio system into my BMW, and oh boy don't I miss a nice system in my car.

sab30

no clue what the crossover points are :dunno: i have the measely 6 speaker system :(

w/o going into great detail and math on, i'm not sure. :dunno: the load on the amp may be the same but i'd imagine that the phase of would be off. not sure if that matters too much cuz i'm not an audio guy. to sort of match the 8ohm tweeters, i'd imagine that a 4ohm resistor would be put in series. :dunno: but now your tweeter would be getting 1/2 as much power as it did w/ the original stock.

add a 4 ohmer in parallel to your mid/bass and your amp see a 2ohm load. your mid/bass will be just as loud as before (and still half as loud as the original). only diff is that you are drawing more current from your amp that heats up that resistor.

n.b.: the resistor numbers are just really really rough. that calc for adding in resistors is really something like

imp = Radd + Rdc + 2*pi*freq*j*H
imp is a complex number of the form I + jQ with magnitude (I^2+Q^2)
and w/ a phase that's dependent on I and Q. "j" is the 90 degree operator (aka "imaginary number"). not sure right now but i think the amp see's the impedence magnitude and puts out current accordingly.




:eek: :eeps: oh .. er .. and the disclaimer: the usual .. i take no responsibility in the above ... :blah: :blah:

Kaz
12-17-2003, 07:20 PM
No, no pics of the amp guts. If you saw it, you'd understand why it's so small and crappy, though.

I thought you could use resistors (ceramic wirewounds?) to do impedance (thus indirectly volume) matching as long as there isn't a passive crossover, since if there is one, the changing impedance will hose the crossover setting. That's what LPads are for. Yeah, it eats power but if you can't add gain on the quieter drivers, what are the options?

HW
12-17-2003, 11:41 PM
No, no pics of the amp guts. If you saw it, you'd understand why it's so small and crappy, though.

I thought you could use resistors (ceramic wirewounds?) to do impedance (thus indirectly volume) matching as long as there isn't a passive crossover, since if there is one, the changing impedance will hose the crossover setting. That's what LPads are for. Yeah, it eats power but if you can't add gain on the quieter drivers, what are the options?

do you mean one of those white wirewound ceramic ones? :dunno: power resistors. i guess if you need to drop some tweeter power then yeah.

E46CollegePunk
12-17-2003, 11:52 PM
the Z6 and the OEM speakers are all 3ohm, woofers and tweeters... yes it doesnt sound "good" but its way better than stock.. and i get the same volume out of teh Zs that i did with the OEM stuff...

Maxing out the amp I mean maxing out its capabilities to produce a good sound since the speakers are so much better now.. the amp was the best part before the swap, now the speakers are the better part.

I was going to do Boston Pros, but they are 4ohm and would sound terrible as far as volume leves/distortion levels

Kaz
12-17-2003, 11:56 PM
do you mean one of those white wirewound ceramic ones? :dunno: power resistors. i guess if you need to drop some tweeter power then yeah.

It probably has to dissipate heat, so it seems to make sense to use those. And that's the style of resistor that gets put into passive crossovers for impedance correction or something.