[scramjet]

I have a 2009 335xi (e90) w/Hifi. I was looking at the options for Amplifier and DSP. I am a little confused by the balanced differential inputs requirement for the output of the harness. Does that simply imply that it needs to accept a higher input voltage?

Specifically I was thinking about a miniDSP to XD600/6. I couldn't tell if you could just put something in line (LOC) to reduce the input voltage <2V or if the balanced differential required a "special" RCA connector--I think I understand the common ground, three conductor principle, but is it a requirement in practice?

For reference I'm also looking at:
Focal 130 VRS in front doors (or maybe SLC 210.25NG)
SWS-8Xi underseat

Also, trying to find options for 5.25in in the back deck, but had trouble finding space requirements, I see that SLC 230.25 NG fit with 58mm mounting depth with a little rework. Are there depth restrictions back there? Reference

[Technic]

According to MiniDSP, the BMW balanced outputs are fully compatible with the MiniDSP balanced inputs. No need of any LOC. Please send them an email for a more detailed response.

Other than the old MB Quarts 130 mids, no other 130mm mids will fit in the front or rear of your E90 without modifications. You need 100mm (4") mids.

Please search for 4" speaker recommendations, there is a full thread on that.

Originally Posted by scramjet

I have a 2009 335xi (e90) w/Hifi. I was looking at the options for Amplifier and DSP. I am a little confused by the balanced differential inputs requirement for the output of the harness. Does that simply imply that it needs to accept a higher input voltage?

Specifically I was thinking about a miniDSP to XD600/6. I couldn't tell if you could just put something in line (LOC) to reduce the input voltage <2V or if the balanced differential required a "special" RCA connector--I think I understand the common ground, three conductor principle, but is it a requirement in practice?

For reference I'm also looking at:
Focal 130 VRS in front doors (or maybe SLC 210.25NG)
SWS-8Xi underseat

Also, trying to find options for 5.25in in the back deck, but had trouble finding space requirements, I see that SLC 230.25 NG fit with 58mm mounting depth with a little rework. Are there depth restrictions back there? Reference

[bmw325i]

You need the Mini DSP balanced kit, it accepts balanced inputs.

[scramjet]

Hi, thanks for the reply, I'll follow up with miniDSP:

For the 130mm I was referring to the master speaker list here that lists some 5.25 options for the front door. I'm not beyond doing some moderate modification if I can keep the stock grills; but if it's just not possible I can go the 4in route.

In the previously posted reference link the gentleman uses a hole cutter to expand the 4in deck to accommodate the bigger diameter in the rear deck, is that not possible? I'm planning on doing similar I just haven't seen any depth limits other than what I inferred from that install.

I've got some decent fab skills for adapters and such, I'm just trying to get a feel for the physical limits on stock locations; so it's an absolute no to the Focal 130 VRS in the front doors with stock grills?

[scramjet]

In regards to the balanced inputs, do three conductors come off of the head unit to directly terminate into the DSP or are there RCA connectors, I've seen a couple of iterations of Technic's harness and I'm not sure if I'll need some sort of adapter to get bare wires out from an RCA or not?

I'm not fully comfortable with the balanced inputs, I take that to mean three conductors, but the amps that support balanced differential inputs only support RCA connectors which are inherently 2 conductor. What am I missing?

[Technic]

Originally Posted by scramjet

In regards to the balanced inputs, do three conductors come off of the head unit to directly terminate into the DSP or are there RCA connectors, I've seen a couple of iterations of Technic's harness and I'm not sure if I'll need some sort of adapter to get bare wires out from an RCA or not?

I'm not fully comfortable with the balanced inputs, I take that to mean three conductors, but the amps that support balanced differential inputs only support RCA connectors which are inherently 2 conductor. What am I missing?

The OEM HU uses 2-wires per channel, the positive and the inverted signal.

Please search, this has been discussed ad nauseum.

[scramjet]

The search function has been smoking for the past three or four days due to overload there really isn't much that explains why/what/how so much as "get an amplifier with balanced differential inputs"

My confusion lies in termination at the miniDSP, I've posed the question to them as well. In the manual2.4.2. It shows a balanced signal terminating to three terminals, positive negative and shield. If you terminate with 2 wires "unbalanced" as they call it you jump the shield and ground. Since the RCA cable has an inverted positive and negative, terminating with the jumper in my mind would negate any gains you would get in noise cancelling (i.e. cancel the negative inverted signal)

So far I've just assumed that there is some scientific magic that works with the floating ground between HU and amp, but when you throw a device with a "true" ground in there my understanding falls apart. I think figure 17 in this diagram at the bottom has some relevance, but again, not sure how you get an inverted signal out of a ground/shield or vice versa.

Maybe I'm thinking too much

Edit: changed the website to a better version for termination

[ctuna]

FYI
http://en.wikipedia.org/wiki/Balanced_audio

Balanced or differential input are used to reduce noise.
They are also used with a twisted pair wiring arrangement .
This means there are two signals of equal an opposite polarity,
going down two wires.(no shield in most cases and in the BMW)
There is not a common ground in this setup.
The radio or nav/radio in a BMW uses a twisted pair consisting of
only two wires both of which carry a 5 Volt signal of opposite polarity. There are a lot of amps that will take this signal with no
adapters required.

[Philly328iGT]

I have a HIFI system in my 2011 328i. I just upgraded all my speakers & the sound is great! The problem is I have no push to my speakers. I just bought a JL 600/6 amp & need a harness from Technic. How do I get in touch with him? My amp will be in any day now and I would love to finish my project.

[scramjet]

Still looking for two answers:
-any depth limits on the E90 rear deck?
-any experience with 5.25in in the doors specifically Focal 130 VRS? moderate mods are fine

[Ml3456]

scramjet

Do you need a mini dsp? I thought a HIFI unit can plug in directly to a JL XD600/6, and with Technic's harness this is real easy?? Plug and play sort of.

Regards, ML

[bmw325i]

Originally Posted by Ml3456

scramjet

Do you need a mini dsp? I thought a HIFI unit can plug in directly to a JL XD600/6, and with Technic's harness this is real easy?? Plug and play sort of.

Regards, ML

No the DSP isn't necessary. It will improve sound quality, but it isn't needed.

[chumley]

Originally Posted by scramjet

Still looking for two answers:
-any depth limits on the E90 rear deck?

Interested in rear deck fitment as well. The list of speakers thread is an awesome resource but with respect to the 4" coax's the list is a 3 years old and virtually none of those listed are widely available. Crutchfield and few others for example sell newer versions of the Infinitys but they aren't among the list of speakers that supposedly fit our cars.

Wouldn't be hard to make an adapter plate but it's pretty tight quarters to do major trimming. Not sure on depth.