Thread: W211, NTG2.5, H-K, How does it work together?

My car is MY2009 and is new to me. I've been reading plenty to understand how things work together, specifically in regard to the COMAND system. The optical ring is very interesting and confusing all at the same time. From what I can see, it's much like the old 10BASE2 network system of the 80's, where the digital information daisy-chained around the network. Only in this case, it's optical. But I think it's more than that...

My goal is to figure out if there is any reasonable way to tinker with the existing audio system, as supplied in the car by M-B. I'd like to be able to play with the way the subwoofer is set up... ideally adjust crossover frequency and level. You can adjust bass and treble, fader etc., but NOT the sub, from the driver's seat. I don't want to reprogram the interface to add sub channel controls! Just want to be able to make one time changes that would let me live a little happier with the controls offered. From what I've learned so far, I believe all this happens in the digital domain, so attempting to reach my goal with analog filters downstream of the sub amp would be a waste of time...

Recognizing that this forum isn't an on-line correspondence course on electronics, I think I can ask two questions that I hope can be answered without more effort than I intend!

1) Given the correct STAR (hope I'm using that right) software/interface/access, are there any adjustments available to technicians that allow adjustments to the factory subwoofer settings?

2) Is there a web link that explains how the NTG2.5 system actually works, with some explanation of the digital optical ring? I haven't found one yet... and whether the answer to (1) gives me hope or not, I'd still like to learn more about the system itself.

Thanks!

Working my way through a sea of acronyms, I found a site that does a very good job of explaining the optical network. For the benefit of those following behind me...:

MOST - Home > Home

Combining synchronous and asynchronous data as they describe is interesting.

I think question (1) in my post above is now what's relevant. I'll wager that the bass/treble and even balance/fade function adjustments are done in the digital domain and the information required for each channel is then sent down the fiber to the appropriate amplifier. So odds are, the data transmitted to the subwoofer amp has already had the low pass filter applied (digitally) and the level set. I might be able to intercept the analog high level signal between the amp and speaker coil and do something with it, but if I don't like the cutoff frequency I'm out of luck. Same thing if I tap into a door speaker - I'll bet it has been stripped of the bass information destined for the subwoofer, so that would be a wasted effort.

Therefore the ideal scenario is to be able to make adjustments to the logic in the control unit. Second best is to grab the signal from the speaker wire headed to the subwoofer (hoping the cutoff frequency is acceptable).

So... could a M-B technician, or someone with his computer gear but not his employment restrictions make this sort of digital change? Or is this simply not adjustable?

An obvious third scenario would be to install some sort of costly MOST interface device that would allow you to drive your own amplifier and speaker. I'm not going there... just too costly for the possible benefits realized.

BTW, I'm not coming at this with the desire to turn my car into a boom box. Just the opposite. I want to hear a nice full range *without* cranking things up. The system from the factory is like the rotary in my RX-7... no impressive performance until you wind it up (to 5,000 rpm or more... )

You need to work at speaker level inputs and high end audio equipment.

Originally Posted by BenzModz

You need to work at speaker level inputs and high end audio equipment.

By that you mean disconnect the wires feeding the existing subwoofer and run them into the high level input of a decent aftermarket sub and amp system? Eliminate the existing sub from the system completely?

Originally Posted by Beeeerock

By that you mean disconnect the wires feeding the existing subwoofer and run them into the high level input of a decent aftermarket sub and amp system? Eliminate the existing sub from the system completely?

I would imagine so. The old sub is really small.

MOST is more like token ring than ethernet - i.e its a ring and a broken device breaks the ring.

The subwoofer amp "plug" has left audio, right audio, ground and a power-up signal.

If you are trying to improve Bass, re-route it to a decent amp and subwoofer. The HK sub is not big, and nor is the subwoofer.

The HK subwoofer amplifier connects to the main HK amplifier. The main HK amplifier does the frequency correction etc. I have not checked to see if HK speakers have cross-overs with the out-of-range frequencies being removed atr the amplifier, but take a look and see (you can get at the center speaker quite easily).

Cheers

Richard

Originally Posted by richard

MOST is more like token ring than ethernet - i.e its a ring and a broken device breaks the ring.

The subwoofer amp "plug" has left audio, right audio, ground and a power-up signal.

If you are trying to improve Bass, re-route it to a decent amp and subwoofer. The HK sub is not big, and nor is the subwoofer.

The HK subwoofer amplifier connects to the main HK amplifier. The main HK amplifier does the frequency correction etc. I have not checked to see if HK speakers have cross-overs with the out-of-range frequencies being removed atr the amplifier, but take a look and see (you can get at the center speaker quite easily).

Cheers

Richard

Hi Richard, thanks for your response! I understand the network topology better now, much like the 10Base2 that ran from computer to computer with coaxial cable and no hub or switch. Leaving a terminator off the end broke things! But also similar to token ring too as it seems to finish where it started, unlike 10Base2.

Your information suggests that the subwoofer amplifier is NOT on the optical network, but is instead fed at low levels from the the main amplifier. I had read somewhere (have to believe everything you read on the Internet!! ) that the main amp and the sub amp were separate devices and separate nodes on the optical network and assumed I would have to deal with high level signals only. And that the sub amp would have been fed a pre-equalized digital signal. Your explanation gives me hope!

I found what looks like an amp behind a small panel on the left side of the trunk. Is that the subwoofer amplifier or something else? Plenty of heat sinking, aluminum construction... looks big enough to power the whole car, frankly. Sorry I haven't dug in further... it's dark by the time I get home and cold enough to dim my enthusiasm for poking around in the rain/snow with a flashlight... (by the way, I found a design flaw... the trunk lid has an annoying tendency to drip *inside* the trunk and onto my head! - LOL)

Originally Posted by Beeeerock

Hi Richard, thanks for your response! I understand the network topology better now, much like the 10Base2 that ran from computer to computer with coaxial cable and no hub or switch. Leaving a terminator off the end broke things! But also similar to token ring too as it seems to finish where it started, unlike 10Base2.

Your information suggests that the subwoofer amplifier is NOT on the optical network, but is instead fed at low levels from the the main amplifier. I had read somewhere (have to believe everything you read on the Internet!! ) that the main amp and the sub amp were separate devices and separate nodes on the optical network and assumed I would have to deal with high level signals only. And that the sub amp would have been fed a pre-equalized digital signal. Your explanation gives me hope!

I found what looks like an amp behind a small panel on the left side of the trunk. Is that the subwoofer amplifier or something else? Plenty of heat sinking, aluminum construction... looks big enough to power the whole car, frankly. Sorry I haven't dug in further... it's dark by the time I get home and cold enough to dim my enthusiasm for poking around in the rain/snow with a flashlight... (by the way, I found a design flaw... the trunk lid has an annoying tendency to drip *inside* the trunk and onto my head! - LOL)

What you read is correct but only for specific year models and with certain head units.

You have probably found the main amp. (about 8"x6"x2") it feeds the subwoofer amplifier with 4 wires
Left
Right
Ground (coax shield of above 2)
Power-up signal.

As they are in coax, I suspect low-level, I don't know if the higher frequencies have already been removed by the main HK amp though - I suspect so.

Richard

Originally Posted by richard

You have probably found the main amp. (about 8"x6"x2") it feeds the subwoofer amplifier with 4 wires
Left
Right
Ground (coax shield of above 2)
Power-up signal.

As they are in coax, I suspect low-level, I don't know if the higher frequencies have already been removed by the main HK amp though - I suspect so.

Richard

Thanks very much Richard, I will investigate further!