I am going to play around with a rough RTA on the 997.2 bose system today (whole system as well as individual drivers). I won't really be able to isolate drivers, but will close mic the measurement as much as possible. Right now, only have access to Audio Tools on the iPad and will use the built in mic (sufficient for this level of work). Need to buy a lightning connector preamp and then I have a calibrated mic I can use. At least I can get a sense of the freq. ranges each driver is producing to give a rough sense of what the expectation of any built in crossover or eq is for the respective speakers (since there is no way we can change any built in crossover in the bose amp).

 

Cool. I would have done this already, but my challenge is a pink noise source. I have a generator, but it's a balanced XLR device; disc-based sources I have are DVD and HD-DVD, so they're not usable in the Porsche. No way to plug in my laptop to the PCM, either.

How are you getting pink noise (or impulse, if that's your tool of choice)?

 

In an effort to try to better understand the Bose system in the 997.2, today I used a quick and dirty RTA analysis. I used Audio Tools (app) on my iPad for RTA measurement with the built in MIC. I left the doors open to best minimize picking up bass from other speakers than the one I was measuring and tried to make as near field measurements as I could given that I was using the built in Mic in the iPad. Let's assume calibration is good enough for rough work.

I used the same app on my iphone directly into the PCM iPod input as the pink noise generator.

I then consolidated the data and filtered our what is necessarily out of band measurements from a particular driver (i.e., low freq from the tweeters) to clean up the measurements. Attached in the consolidated data.

All tone controls were flat.

So, what are the learnings?

1)Sub seems to cover mid30's-80 Hz and has a nice peak at about 50Hz. No surprise there. That peak will make the system sound more bassey than it is. Bottom octave pretty much missing.

2)Door woofer seems to extend from the lowest bass up well into the midrange band. However, no guarantee I was not picking up the sub at the low end and nearby midrange above it. However, my gut tells me otherwise as the door was open and I was fairly careful. Seems like they may just run full frequency into that driver.

3)All three midranges seem to be crossed over at roughly 250hz and then 4500hz. At the low end that seems about right. At the high end, seems a little high for a crossover point.

4)Tweeters all seem to have the same crossover point at roughly 4500hz.

Thus, when replacing the drivers, one should keep these ranges in mind, but they do not present anything exceptional.

I'm really interested to know the efficiencies of the drivers. Matching them to the Bose drivers would more easily facilitate integration with the existing sub if one were to keep it.

Of course, these measurements are very imprecise and quite subject to any EQ or crossover filters in the Bose electronics.

db

 

After some reconsideration, I want to update my comments on my prior post. Given the near field measurement, I think I drew some incorrect conclusions. I have now posted the raw data for the subs, mids and tweeters and add some additional comments:

Regarding the woofer chart, it appears as though the sub is allowed to naturally roll off.
Regarding the Door woofer, I am now sure if it is allowed to naturally roll off or if there is some degree of a low pass filter. It looks like there may be a first order roll off around 350Hz or so. Assume this is built into the Bose electronics. This should not exceptionally influence woofer choice. The various 6.5"+ woofers chosen by those on this forum appear fine.

Regarding the mids, I think the high pass corner frequency for these is about 200Hz, second order (12db per octave). Given I did not see any crossover components in all the pics on this forum, this is likely done in the Bose amp/electronics. On the high side, I was not measuring near a tweeter and as such I believe these drivers are allowed to naturally roll off at the high end. Thus, substitution of a coaxial 4" for this driver might not be a bad choice. Otherwise, just make sure the driver can handle a 200Hz low end.
(The low bass on the graph is likely from the subs and door woofer - ignore).

Regarding the tweeters, again, ignore the low freqs picked up from the other speakers. There appears to be a 1st order crossover filter with a corner freq of about 5khz which is consistent with the single cap seen in some of the pics of the removed tweeter. A similar setup would likely be fine for replacement as those herein have done.

Again, would love sensitivity data!
I may need to remove a driver from my car to test. I think the rear mid/tweet would be easiest. Assume all drivers (other than sub) have similar sensitivity.

db

 

Thanks a lot for the contributions here! I have plenty of drivers sitting around! If you want to test some, indeed the rears are very easy. Use a trim tool to remove the cover, then the both rear speakers are held on by one screw.

Amazing to see the that the stock sub covers down to mid 30's. This is with 2 5.25" drivers. Given the enclosure, it would seem likely that improving those drivers to the JL Audios might garner some benefit.

I ran the 6.5" in the doors and they sounded very good. There is certainly more bass and deeper base with the IS200 8" woofers though.

Without any measurements, I would subjectively say that the Focal's are a bit less efficient (even with 90db efficiency specs) than the Bose. However, that level of efficiency is easily driven by the Bose amp, a fact that I found totally surprising. I'll admit too that I listen to plenty of hard rock, so I like it loud. The new system does not disappoint.

Who's going to post results after swapping out the sub 5.25" woofers???

 

No question about it. BMW has done a much better job with their systems, especially the Logic 7 you can get in the M3. Do the budge upgrade with new drivers, you'll be very pleased.

 

I ordered a rear set (plate plus mid and tweet) from a junk yard for short $$ and I will use that to test. That way, I don't have to touch the car or be afraid to mess with the drivers. I would like to get my hands on one of the 8" drivers....

Is the midrange in the rear the same as that in the door? The brochure from the 2011 GTS claims both are 8.0cm (3.14") midrange drivers. Assuming the efficiency on all drivers is the same (would likely be given the parallel wiring of the mid to tweeter), my testing should be directionaly accurate for all drivers.

The sub enclosure is a bandpass. That design gives high efficiency across a narrow frequency band and little output beyond the band (up or down). I'm guessing Bose uses this design to give high output from a small box but gives up low extension and uses the door woofers for the upper bass. The box is tuned to the speakers parameters. Replacement with unlike drivers will likely not yield a proper result.

How easy is it to access the connector to the sub? I'd like to test the signal going to it.

db

 

Yes, the midranges are both 3" drivers in the doors and the rear panels. However, I thought that either the signal to rears are reduced or the speakers are slightly less efficient. I believe it is the former, not the latter though. Note that the fader works in odd ways - when you go all the way forward, the sub is cut off and all the way back, I'm not sure the sub is working either.

The sub is easily accessed. Remove the port caps and then unscrew the two large torx screws, one on each side under the ports. The enclosure slides out on tracks. You will need to also remove the seat resting points to allow the enclosure to slide out.

I'm curious how "tuned" the box is to the speakers' parameters. I'd still like to hear about a test swap of other speakers into that unit.

 

Ryem3,


I ordered all my speakers, just one question (for now): Did you replace the center dash speaker or just disconnect? I think you did the latter, but then did wind up replacing it if I follow the thread correctly.


If you did replace, did you add a capacitor? I have the 2 tweeters in the IS200 coming, and also have a pair of Focal TNI 1.5, so I can cover all 3 locations.


Thanks again!


Chris

 

Awesome! You have it correct. The replacement center channel tweeter was from an IS200 kit, so it already had a built-in high pass cap. It blends in nicely.

Keep us posted!

 

So, who's done an install? What happened to my buddy Rick in Asia? Interested to hear some new reports!

 

All my speakers are in and I am hopeful to begin work this week before the holiday hits, but it may have to wait until after.


Chris

 

OOC, are you doing doors, tweets, center and rears? 8's or 6's"? If you are using what we have used and have not read the full thread, please do so.

 

Rick here reporting for duty sirs! Havent gotten the time to do the install so i am doing bits and pieces. Over the weekend i only had time to try to disconnect the center speaker. Let me just say i messed it up by scratching the whole place where it was. That soft touch paint is fragile! Scratched up the speaker area and accidentally placed a wrist with a watch on the chrono, so that was scratched as well. Bummer!
Well nevertheless with tweeters from the focal on the sides, i removed the center speaker and i felt it decgraded the sound! Seriously. The sound felt lacking. I guess its becasue the speakers are not matched yet there were "holes" in the sound. I had to reinstall the center speaker. My guess is the whole set of focals have to be installed before disconnecting the center speaker to get the good sound our brothers here are talking about. Now i have to find a way to repair the messed up soft touch paint!

 

Sorry to hear that. No reason to cause any damage, very unfortunate. Are you using trim tools? Critical for this job and they only cost $20. Griot's garage has a nice set. You definitely don't want to do the door panels without them.
Not sure why the center would have improved the sound that much. It is definitely drowning out your tweeters.