The results from Saturday's testing:

I'm confused. The swap is a good thing to do on non-HiFi systems, and doesn't seem to do anything for HiFi systems.

Many thanks to Robin and to Kevin for their patience and the use of their cars. Many thanks to D Unit for the loan of the tool. Many thanks to Schatzy62 on the East Coast for verifying many things and generating more data. Thanks to Ryephyle for doing the same. Thanks to many more, I'm sure, for prodding, asking questions, and trying things.

What I know for sure:

Part numbers on the X9331 connectors:

Male: BMW 1378137
Female: BMW 1378139-B5

Shcatzy62 confirmed that the HiFi and non-HiFi systems use the same head units; part numbers for nav and non-nav are the same.

I confirmed the flat response at the X9331 connector in HiFi systems for both front and rear channels, and weird performance at the rear woofer, including the bump from 40 to around 80Hz, pointing questioning fingers at the HiFi amp.

I'd have to agree with NSX Jr's hypothesis that there's a programming difference, someone telling the head to do different things.

What we did:

Eric arrived first with his (leased) 07 MCS HiFi (no nav) build date 2007/02.

I'd gathered and pre-flighted my test equipment. I also prepared more CD copies of my bass test playlist. The first three tracks are from the Denon Audio Technical CD: channel check (l and r), phase check, and then a 0dB 40Hz sine wave, both channels. Following those three tracks is an assortment of music with strong/interesting bass.

Popped the CD into Eric's MCS. Track 3? Wow! Plenty of bass! Sounded great! Played a few more tracks, and they sounded very good as well, at least on par with my channel-swapped MCSa and subwoofer. The subwoofer adds punch not present in Eric's car, but that's to be expected.

Robin arrives with his 07 MCS (build date 2007/03) with Nav. Robin has removed the rear seat in his MCS and replaced it with a very custom cabinet holding among other things two Infinity Kappa 6x9 speakers, which are wired to the connectors for the old HiFi rear woofers and tweeters.

Put one of the test CDs into Robin's MCS. Track 1, track 2, track 3?

No bass on track 3! What? We're getting sound on the rear, but no bass?

The only conclusion I can reach is that something is different on Robin's MCS!

Eric's car is leased. Robin's isn't. Eric's car sounds just fine; no reason to pull things apart, and it's leased, not sure I want to rip into it with as much abandon...

So Robin's car became the guinea pig.

Running curves:

Repeating the same process as before in my 08 MCS, driving the system from the AUX connector with controls set flat, measuring the response at the X9331 connector, front and rear channel response is damn flat from 50Hz to 16 KHz, with a sharp rolloff from 50Hz down to 20Hz, down about 7dB at 20Hz from a 2KHz reference:



Curves Front 1 through Rear 5 are as before, reflecting measurements taken on my 08 MCSa non-HiFi.

The last three curves are the interesting ones. (Note that while I took the data, the graphing and interpolation is Excel's. If you want the raw data so you can do your own graphs, drop me a note and I'll send it to you.)

The two X9331 curves are right on top of each other, the response pretty much dead flat from 50Hz up to 16KHz.

The last one is measured at the rear woofer. There's some serious messing around going on in that amplifier! Big peak around 50Hz, with a sharp dip around 100Hz. A closer look around that area shows boost from 40Hz to 80Hz, with a sharp drop at 90Hz and the bottom at 100Hz.

What is it that makes Kevin's car sound so different from Robin's?

I don't know!

It certainly seems, as NXP Jr hypothesizes, the head acts differently in HiFI and non-HiFi systems. Programming? Detecting the HiFi amp? Don't know!

Things to do:

Take Kevin's car apart?

Run curves at different volume levels? It would be nice if I could automate some of the testing, to speed it up, and also take more sample points.

Thanks again to Kevin, and to Robin, for his patience!

 

I have a 2008 MCS Clubman with the HiFi otion, build date is early July. I went to the following site and downloaded a test tone cd to play with:

http://www.realtraps.com/test-cd.htm

I then went to Radio Shack and bought a digital sound meter for ~ $50 which I thought would be wise before ripping the car apart to change connectors/speakers etc.

While the cd has tones in 1 Hz increments from 10-300, I did some quick tests just hitting every 10 Hz from 10-290. I was primarily trying to identify whether the hi-pass filtering was present on the rear feeds from the head unit. From the charts I produced, and now from other measurements from K6 its clear the HiFi doesn't have the hi-pass filtering on the rear.

There is some very odd shaping of the spectrum from 30-120 Hz however and there is still a very large difference in the front vs rear particularly from 70-100 Hz. Its still unclear to me at least what is causing this. From K6's measurements it appears its down to the amp, speakers, the cabin acoustics or some combination of these 3.

For me in most cases I am satisfied with the HiFi. On most songs its quite good, but only good after you learn to fiddle with the settings. Some songs just won't play well at all on the bass end no matter how much fiddling.

For the charts, I set the volume to an acceptable ear level, left it alone and had the bass treble settings at 0. The 3 graphs are fadder at 0 = blue, fadder all the way front = red and all the way back = green.

 

I agree that there is something telling the head unit that there is an amp connected. That is probably why the HiFi amp has a connection to the Central Computer
I hate to ask this question but it is one that i would look at as there is not reason via measurement that the bass should be there.

Has any one rechecked the polarity on the rear speakers in Robin's car?

It can be a very easy mistake to make and easy to fix. I should know i have done it before. The easy thing to try is to swap only the wires to one speaker if the bass comes back there was the problem.

At least I know that my measurements were some what accurate.



Again has the obvious been checked? it can be easily over looked.

Before taking Kevin's Lease apart can you recheck the polarity on Robin's rear speakers

I will be finding out by tuesday if i can get my hands on some other testing equipment. I will let all know what happens.

 

K6rtm,
Where is the hi fi rear woofer? I dont see one on my hi fi system.

 

Sound measurements are a little tricky here. Recognize that the response measured going into the speaker will be different from the Sound Pressure Meter reading in front of the speaker (this difference is the speaker's response) which will again be different from the response at the ears of the person in the driver's seat (this difference is the response of the car's interior).
I suspect that the amplifier might be compensating for one or both of these in an attempt to create a (hopefully) optimized response at the driver's ears.
Also, when more than 1 speaker is being driven, the Sound Pressure Meter measured response will vary depending on the relative phase from the multiple speaker sources. Moving the meter a few inches will result in an entirely different response.

 

Absolutely 100% agree. The charts I posted are showing the characteristics of the whole system from head unit, through the amp, the speakers and the cabin acoustics. Each part in the chain adds to the response at the meter.

 

Eric--

Thanks again for all your help in this crazy task.

The measurements I performed, represented by that last weird curve, were electrical measurements of the woofer channel of the amp. Just measuring amplitude -- not measuring phase. I was also only feeding (and measuring) the left channel of the system, so acoustic phase cancellation doesn't come into play here.

(When we hooked up the subwoofer, which takes L and R and mixes them down, I had a crossover in one channel -- and it was quite audible. Opening up one side increased the bass level. We tracked down my wiring error, fixed it, and had much more bass! Here, we're only driving and measuring one channel, hoping to eliminate or at least reduce the number of free variables.)

Does that help?

 

The HiFi System uses a 6x9 woofer on each side of the rear and a separate tweeter on each side of the rear.

Each woofer (6x9) in the rear has its won amp channel and each tweeter in the rear has its own amp channel for a total of 4 amp channels driving speakers in the rear of seat area of the car.

 

I forgot to add one other note. The test cd you can create from the website is great for identifying vibrations in the cabin. I have at least 2 frequencies, and probably more, where when played loudly cause the cabin to vibrate and resonate. I'm sure this is interfering with the overall sound quality in the cabin when the volume is turned high. If I can't fix these myself, at least I can reproduce them easily if I need to bring it in to be fixed.

 

I just had to ask as the obvious is sometimes the hardest to remember to check.

It just seems so odd that my car, Kevin's car, and it seems like some others seem to have no problem producing the bass just that to some of our ears it is rather muddy or lacking of definition.

I am just trying to assist in figuring out what might be the problem.

Does you Denon Audio Check CD have a phase check track on it. I know mine does and to be honest both the inphase and out of phase portions of the rack do not sound correct. Kind of like both are slightly out of phase but not completely. Sort of like the Inphase which should have both drivers pushing out at the same time is not, more like owe is lagging behind like maybe 90 degrees out of phase rather than at 0 or 180 out.

Again i am waiting to see if i can borrow some equipment from someone to test out this theory and also do some other testing.

From a few measurements i took is also seems like the front and back speakers (woofers) are out of phase form each other. And that would not be a good thing.

 

I agree this makes my bean hurt, but that's why I love the interwebs -- there are people out there that have the brains and what it takes to make it better. All I know is that I want the Harmon Kardon back from my 06 and the Hi-Fi system can go in the trash.

All I can say is THANKS for doing all the investigation and I look forward to the final verdict!

 

The Denon Audio Technical disc has a simple phase check -- a voice in phase, and then one channel flipped 180 degrees to create an out of phase result.

What we want (and I'll try and put together this week) is a set of test waveforms that let me track the waveform through the system -- something recognizably asymmetric -- a low-frequency sinewave, say, with a lower amplitude high-frequency burst around the positive peak. I can do something similar with the arbitrary waveform generation capability of the HP3314A, and I'll probably play with that.

A few test tracks of that will give us another tool to investigate with.

A car is a really tough audio environment, full of dips and resonances (and that's not counting driver and passengers!) -- I don't think you necessarily want an electrically flat response from the system, but acoustically as close to a flat response (both in amplitude and time domains). Tough to do!

Keep asking the simple questions -- they force us to (re) examine our assumptions, and are the hardest to answer!

 

It would be interesting to compare the info on the radio's "Service Mode" screen between the HiFi and non-HiFi versions. I poked in mine today and didn't see anything obvious, but who knows...

Proceed as follows to call up the Service mode:

• Terminal 30g ON (key on / engine off)
• Switch off the radio
• Switch on the radio again
• Within 8s for a duration of 8s, press the button for manual station-search function
• The radio switches into the Service mode

 

I was going off his chart it lists
front 1
front 2
front 3
rear 4
rear 5
then hi fi woofer
so it would be 2 woofers,no?

 

I do not know where you got this chart but post #73 of this thread gives the amplifier channel and which driver it is for.

Here is a link to post 73 of this thread.
https://www.northamericanmotoring.co...1&postcount=73

 

I've been following this thread and I find it fascinating. There's a lot of good, honest brain-power at work here. Keep it up guys, I can't wait to see a final assessment on the Hi-Fi system.

With 10 speakers in that system, all it'd take would be one speaker wired in reverse phase to start mucking up the sound stage. I would think that in production, it could be an extremely easy error to make. Not one easily noticed in post production quality testing, either.

I won't see my lil' guy until next month. Can't wait to see what sounds I get out of my hi-fi.

 

The chart I'm referring to is on post 103.

 

That was just ONE (1) of the 6x9's in the rear of the car as a test.

It is actually a frequency response curve. and it show a very odd response.

I suspect from that response they only bothered to do one until some other conclusions can be come up with.

 

Fascinating thread guys. While I don't pretend to understand it all I did see one question...
What is it that makes Kevin's car sound so different from Robin's?

Eric's car is stock. Robin messed with the back 6x9's in his. Question above is whether Robin could've swapped polarity in his rears by accident. I'd say the stock car is the gold standard, right?

 

If so, this would mark the first time in recorded history that British wiring was referred to as a gold standard.

Hell, this stuff is probably all put together by robots these days anyways. Robots don't wire out of phase.

 

...And my measurements were phase-agnostic, looking only at amplitude.

The phrase "Lucas Electrics" has come up, but when you look at the diagrams and see colour codes such as GE (yellow) and SW (black), you know that Joe Lucas, the Prince of Darkness, is nowhere in sight!

Some good news today, though -- got a call from the Mini dealer on my car. When I took it in with what I referred to as the "BOZO light" (the airbag warning), I confessed to having the seats out of the car, but I'd done that in the past, and put things back in sequence, checking connectors, etc, before reconnecting the battery and starting it up.

Turns out I've got a bad seat position sensor, and it's orthogonal to what I've been doing -- i.e. not my fault! Good news and bad news -- the good news is that it won't cost me money, but the bad news is I won't get my car back for another day or two. The 5.2V8 in the Jeep has plenty of get up and go, but it doesn't corner like the Mini (and I'm not going to try!).

 

k6rtm:

 

I had a good friend who is an audiophile read over the thread and he asked a question (not having seen any of the connections I didn't know how to answer him)-- it sounds like in the Hi-Fi system that the amp is part of the problem/solution so would it be possible to switch the connections coming out of the amp to the back speakers instead of having to tear apart the interior to get to those speakers? Again, I don't know but thought I would ask.

 

It's possible to switch things at the output of the amp. The pinouts are documented.

But given my anomalous results from last Saturday, when Kevin's HiFi system sounded great, and Robin's sounded not so great, I would like to understand things better.

Oh, getting to the amp is the same as getting to the left rear speaker -- go read the speaker swap thread and learn what a joy that is! "B" pillar cover, "C" pillar cover, rear seats ... to start! It takes less than an hour to expose the stuff, but it's a lot of work.

 

It is also a pain to get all the panels back in without smashing the plastic snaps when they don't all light up perfectly.

Amp is the finned box on the left rear.