[Viffermike]

Gang,

Sorry I haven't had a chance to post on my JL 600/6 install. Been a crazy couple of weeks ... and I leave on a 7-day/6-night, 15-state, 3,200-mile road trip on Friday morning, so it'll be a while before I get to it. Hopefully next weekend!

[matt@bavsound]

This may sound like sacrilege, but I always found it best in modern cars (BMW, Audi, VW, Mercedes, Porsche, etc) if I was leaving in the factory head unit to actually add the new amplifier AFTER the factory amplifier to alleviate all such issues with input voltage, car chime through the speakers, bluetooth audio, noise, etc. Most of the systems I built in the early days, and whenever the customer and budget would allow with later vehicles, I ALWAYS replaced the source unit (and any factory amp) as that's simply the best way to go, but sometimes the only option we have is to piggyback onto the OEM system.

There are a number of signal summing devices out there that will let you combine channels coming out of the factory amp to get clean full-range and high voltage signal into your aftermarket amp - AudioControl, JL Audio, Rockford Fosgate, and more. My favorite is the Audison Bit 10 or Bit 10D.

The last system I did this way was a 2016 M6 with and Audison Bit Ten, Bavsound GhostSubs, Focal drivers front and rear (customer request), two JL Audio 10TW3 woofers in a slim enclosure under the rear deck and a JL Audio 900/5. It sounded absolutely phenomenal with no noise to speak of and plenty of output.

I can understand the temptation to bypass the factory amp in these modern cars, but because of all the BS the OEMs put in the way of good, clean signal nowadays, the best bet is to start your signal chain at the output of the factory amp in pretty much every case.

Hope this helps, and it's just one man's opinion, but the industry has been moving this way for quite some time not out of ease of installation, but out of a desire for the best results from a less than ideal situation...

[Viffermike]

Originally Posted by matt@bavsound

This may sound like sacrilege, but I always found it best in modern cars (BMW, Audi, VW, Mercedes, Porsche, etc) if I was leaving in the factory head unit to actually add the new amplifier AFTER the factory amplifier to alleviate all such issues with input voltage, car chime through the speakers, bluetooth audio, noise, etc. Most of the systems I built in the early days, and whenever the customer and budget would allow with later vehicles, I ALWAYS replaced the source unit (and any factory amp) as that's simply the best way to go, but sometimes the only option we have is to piggyback onto the OEM system.

There are a number of signal summing devices out there that will let you combine channels coming out of the factory amp to get clean full-range and high voltage signal into your aftermarket amp - AudioControl, JL Audio, Rockford Fosgate, and more. My favorite is the Audison Bit 10 or Bit 10D.

The last system I did this way was a 2016 M6 with and Audison Bit Ten, Bavsound GhostSubs, Focal drivers front and rear (customer request), two JL Audio 10TW3 woofers in a slim enclosure under the rear deck and a JL Audio 900/5. It sounded absolutely phenomenal with no noise to speak of and plenty of output.

I can understand the temptation to bypass the factory amp in these modern cars, but because of all the BS the OEMs put in the way of good, clean signal nowadays, the best bet is to start your signal chain at the output of the factory amp in pretty much every case.

Hope this helps, and it's just one man's opinion, but the industry has been moving this way for quite some time not out of ease of installation, but out of a desire for the best results from a less than ideal situation...

Hi Matt,

First off: Thanks for the input on this thread. The discussion is definitely interesting -- particularly as it relates to the 2 Series audio system, which is in some ways simpler than other BMW audio systems ... which I feel is part and parcel of the unique set of problems we 2ers deal with when upgrading it.

As I'm sure you're aware, the biggest bugaboo with our 2 Series systems -- and many OEM systems -- is the built-in DSP. We're fortunate in that it lives in the OEM amp module, which can be largely bypassed without affecting other important on-board systems. That makes adding an aftermarket amp feasible relatively easily, and makes some of the aftermarket 'correction' modules you refer to above somewhat unnecessary.

However, we're not fortunate in that the rest of the OEM system is designed to work with that OEM DSP -- including the head unit. The discussion above about the low voltage coming from the HU's outputs is indicative of this. Plainly the system design needed to account for (and partially mask) the low-voltage analog output of the HU, which is used in many other BMW models other than the 2 Series. In those other models, however, the post-HU system is markedly different in that the output doesn't remain analog all the way to the amp -- but in the 2 Series, it does. This, I'm pretty sure, is the reason the output voltage is so low in our systems.

That makes aftermarket processors such as the ones you mention above helpful as line-level voltage boosters in 2 Series cars. Is one absolutely necessary, though? I would argue not -- but that said, such a unit can certainly help sound in ways beyond simply boosting the line voltage. The key is selecting a unit that works with both the specific design of the audio system and personal system goals, because all of those units approach sonic correction from different directions -- and some, such as the JL Audio and many AudioControl units, are not good choices because of how they achieve results:
- Most of the JL Audio DSP units are designed to offset existing DSP. That makes their usefulness limited with an aftermarket amp with a relatively flat signal ... and besides: offsetting a frequency-spectrum curve with another frequency-spectrum curve is a huge no-no sonically.
- Many AudioControl DSP units convert analog signals to digital -- and then back to analog again -- to achieve their effects. For a sonic purist such as myself, this is unacceptable when I already have an analog signal coming out of the HU. Personally, I only want digital conversion to happen once in a system at most.

In systems such as that M6 you refer to, a DSP unit is absolutely necessary because the audio system won't easily allow an amp alone to flatten the sonic spectrum so a baseline for fine tuning can be set. In our cars, it does allow an amp to do this. The issue is HU output line voltage -- which, though not ideal, is certainly work-able with the right amp.

[matt@bavsound]

Originally Posted by Viffermike

Hi Matt,

First off: Thanks for the input on this thread. The discussion is definitely interesting -- particularly as it relates to the 2 Series audio system, which is in some ways simpler than other BMW audio systems ... which I feel is part and parcel of the unique set of problems we 2ers deal with when upgrading it.

As I'm sure you're aware, the biggest bugaboo with our 2 Series systems -- and many OEM systems -- is the built-in DSP. We're fortunate in that it lives in the OEM amp module, which can be largely bypassed without affecting other important on-board systems. That makes adding an aftermarket amp feasible relatively easily, and makes some of the aftermarket 'correction' modules you refer to above somewhat unnecessary.

However, we're not fortunate in that the rest of the OEM system is designed to work with that OEM DSP -- including the head unit. The discussion above about the low voltage coming from the HU's outputs is indicative of this. Plainly the system design needed to account for (and partially mask) the low-voltage analog output of the HU, which is used in many other BMW models other than the 2 Series. In those other models, however, the post-HU system is markedly different in that the output doesn't remain analog all the way to the amp -- but in the 2 Series, it does. This, I'm pretty sure, is the reason the output voltage is so low in our systems.

That makes aftermarket processors such as the ones you mention above helpful as line-level voltage boosters in 2 Series cars. Is one absolutely necessary, though? I would argue not -- but that said, such a unit can certainly help sound in ways beyond simply boosting the line voltage. The key is selecting a unit that works with both the specific design of the audio system and personal system goals, because all of those units approach sonic correction from different directions -- and some, such as the JL Audio and many AudioControl units, are not good choices because of how they achieve results:
- Most of the JL Audio DSP units are designed to offset existing DSP. That makes their usefulness limited with an aftermarket amp with a relatively flat signal ... and besides: offsetting a frequency-spectrum curve with another frequency-spectrum curve is a huge no-no sonically.
- Many AudioControl DSP units convert analog signals to digital -- and then back to analog again -- to achieve their effects. For a sonic purist such as myself, this is unacceptable when I already have an analog signal coming out of the HU. Personally, I only want digital conversion to happen once in a system at most.

In systems such as that M6 you refer to, a DSP unit is absolutely necessary because the audio system won't easily allow an amp alone to flatten the sonic spectrum so a baseline for fine tuning can be set. In our cars, it does allow an amp to do this. The issue is HU output line voltage -- which, though not ideal, is certainly work-able with the right amp.

Well put! I certainly always want to go with the least equipment possible in order to remove the effects of the car environment (glass, hard plastics, etc) and the factory audio "tuning" to get a nice, flat response out of the system. My go-to has always been the Audison BitTen, as it does a really great job of summing all of the available analog signals, converting them to simple analog stereo pairs, while allowing some digital trickery on the middle there (time alignment, parametric eq, crossovers, etc). Plenty of output voltage, and zero noise.

But as you said, it's really possible to pull this off in a 2-series with a simple line driver, or even an amplifier like the JL Audio ones that allow running speaker level voltage directly into the RCA inputs without the need for a converter.

It's always been a shame how much of a walled garden the OEMs try to make their audio systems. I feel like car audio should have been standardized decades ago. If all the carmakers could come together on OBDII, then why not on audio as well?

[Mr Reality]

Your underseat drivers should be 2 ohms so should your factory amp

[Viffermike]

Originally Posted by Dj Johnny

Your underseat drivers should be 2 ohms so should your factory amp

No offense, but that's incorrect. Underseat drivers can be either 2 ohms or 4 ohms depending on model year and Hi-Fi/HK. This has been documented in previous threads; please do a search.

I checked the ohm load of mine (2015 Hi-Fi) with a multimeter; they are 4-ohm drivers.

Do a search for 'SWS8 BMW' online as well; you'll find that Earthquake sells 2-ohm and 4-ohm versions of its drop-in replacement upgrade for the drivers. It has for years because they vary on other Fxx models.

[Mr Reality]

When I checked mine with a multimeter mine was 2 ohms and I was given incorrect information, I was told my car only came with a 2 ohm system. I knew earthquake sold them you just have to cut the wires I was told and alpine I was told sells underseat woofers also

[bmw_fascinated]

I seldom listen to music so I don't want to spend much money on any improvements. However, I bought the TechnicPnP harness to get rid of the annoying ASD sound. This works very well, but there is still this hiss coming from the speakers.
It was stated that there is a noise-offset of about 600mV from an aftermarket amp - now I am wondering what might be the noise floor from the BMW HiFi amp. Did someone measure this as well?
The speaker wires look very thin, so do not think, that the current will be high (what values are to expect?) .
Might it be an option to just solder in some schottky diodes between amp and speaker to cut the noise floor out (voltage drop around 0.4-0.5V)? http://cdn-reichelt.de/documents/dat...360%23MOSP.pdf