[Heytree27]

Hi guys - I want to make some replacements/additions to my Logic 7 677 sound system in my e92. This is my first time modifying an audio system and will take the parts to an audio shop to have it installed and tuned.

1) The only thing I want to keep are all of the speakers.
From the documentation I read there are 9 channels total: 7 rated as 40w/2ohm and 2 rated as 70w/ohm. As far as I can tell, BMW does not publish RMS specs so I’m kind of at a loss as far as knowing how much power these factory L7 speakers can take?

I also plan on adding a Rockford fosgate 10 in sub in my trunk that is 2ohm/500w RMS. The amp is monoblock and rated as 500w rms at 2ohm or 300w rms/4 ohm.


2) I do not have satellite radio, phone or Bluetooth in my current stock logic 7 system. I want to replace the MOST HU with a joying HU that has TOSLINK OUTPUT. It also has Coaxial output and a sub out as well.

3) Because I plan on doing away with the stock HU and MOST altogether, I want to power my system with a 8 channel Audison AF C8.14 DSP Amplifier. This amp is rated as 100w rms at 2ohm and 65w rms at 4ohm. The ampl is bridgeable. I would lose the center channel - but I’ve been told that isn’t too big of a deal. The amplifier has digital input for my joying to hook up to it.

Another amp I am considering is the helix v eight mk2 which is 75w rms at 2ohm and also has optical input.

Would I need any adapters or harnesses? Or would I be good to go because I am not using the factory HU?

TIA

[ctuna]

The specs are actually published but may not be accurate.
Because they are at peak power and 10 percent distortion.
See first three in the block of links also.
Replacing speakers with drop in's is pretty easy on these.



http://www.e90post.com/forums/showthread.php?t=1144129
In the above has the output chip specs somewhere in the thread .
So for something like the underseat's the rms true power at 1 percent distortion
is something like 55 . But 1 percent is still a pathetic output spec.
(see entry 18)

BMW stereo types
http://www.e90post.com/forums/attach...4&d=1278871872
http://www.e90post.com/forums/showthread.php?t=352586
http://www.e90post.com/forums/attach...2&d=1266451970
http://www.e90post.com/forums/attach...2&d=1260829447
http://www.e90post.com/forums/showthread.php?t=641323
http://www.e90post.com/forums/attach...1&d=1209780605
http://technicpnp.com/menuDiagrams/d...e90_92_93.html
http://www.e90post.com/forums/showthread.php?t=343673
http://bmwcoders.com/forum/3-er-8/bm...1-e92-e93-291/
http://www.musicarnw.com/page-2/
http://www.e90post.com/forums/attach...1&d=1209780865
http://www.e90post.com/forums/attach...3&d=1169133185
http://www.e90post.com/forums/showthread.php?t=138949

The only amp that actually works with the BMW Most Bus is as a drop in is made by Mobridge
because the optical bus is a proprietary BMW Code.
This is the only amp that directly reads the code.

https://mobridge.us/products/

Technic Harness for Logic 7 retrofit will make life easier.
Also you will have to program out the Most Bus(optical Bus) for at least the SOS function if you replace
the head unit.

Most Audio shops are not good with BMW's do not listen to what they say.
You can get some real crappy results if you listen to what they say.
Helix Audio Fisher products are good.
Be sure to read the Audio build thread at the top of the stereo sub forum page.
Seems you are randomly choosing stuff and hoping it works without much research
so far.

OPTICAL input may be overrated especially in the stuff you are choosing.
Changing the Head Unit can be a can of worms and may not get you any better sound.
When people put in aftermarket head units they usually run RCA's to the new amplifier and use
something like a Technic Harness to adapt it to the old speaker wires.
Or if they are keeping the BMW head unit they reprogram it for Analog output or buy a analog
to Most Bus converter for the Logic 7 amp to get an Input.
If you buy a DSP amp you have to be ready to tune it.

https://musicarnw.com/ on the west coast and unexpected creations on the east coast are noted
as the two premier
BMW stereo shops in the US.

[Heytree27]

Originally Posted by ctuna

The specs are actually published but may not be accurate.
Because they are at peak power and 10 percent distortion.
See first three in the block of links also.
Replacing speakers with drop in's is pretty easy on these.



http://www.e90post.com/forums/showthread.php?t=1144129
In the above has the output chip specs somewhere in the thread .
So for something like the underseat's the rms true power at 1 percent distortion
is something like 55 . But 1 percent is still a pathetic output spec.
(see entry 18)

BMW stereo types
http://www.e90post.com/forums/attach...4&d=1278871872
http://www.e90post.com/forums/showthread.php?t=352586
http://www.e90post.com/forums/attach...2&d=1266451970
http://www.e90post.com/forums/attach...2&d=1260829447
http://www.e90post.com/forums/showthread.php?t=641323
http://www.e90post.com/forums/attach...1&d=1209780605
http://technicpnp.com/menuDiagrams/d...e90_92_93.html
http://www.e90post.com/forums/showthread.php?t=343673
http://bmwcoders.com/forum/3-er-8/bm...1-e92-e93-291/
http://www.musicarnw.com/page-2/
http://www.e90post.com/forums/attach...1&d=1209780865
http://www.e90post.com/forums/attach...3&d=1169133185
http://www.e90post.com/forums/showthread.php?t=138949

The only amp that actually works with the BMW Most Bus is as a drop in is made by Mobridge
because the optical bus is a proprietary BMW Code.
This is the only amp that directly reads the code.

https://mobridge.us/products/

Technic Harness for Logic 7 retrofit will make life easier.
Also you will have to program out the Most Bus(optical Bus) for at least the SOS function if you replace
the head unit.

Most Audio shops are not good with BMW's do not listen to what they say.
You can get some real crappy results if you listen to what they say.
Helix Audio Fisher products are good.
Be sure to read the Audio build thread at the top of the stereo sub forum page.
Seems you are randomly choosing stuff and hoping it works without much research
so far.

OPTICAL input may be overrated especially in the stuff you are choosing.
Changing the Head Unit can be a can of worms and may not get you any better sound.
When people put in aftermarket head units they usually run RCA's to the new amplifier and use
something like a Technic Harness to adapt it to the old speaker wires.
Or if they are keeping the BMW head unit they reprogram it for Analog output or buy a analog
to Most Bus converter for the Logic 7 amp to get an Input.
If you buy a DSP amp you have to be ready to tune it.

https://musicarnw.com/ on the west coast and unexpected creations on the east coast are noted
as the two premier
BMW stereo shops in the US.

1. I do not plan on keeping the logic 7 amp or hu.
2. This is what mobridge told me:
“ Ok so if you want to get rid of the logic 7 amp you have no need for a most adaptor on either end. It's going to be much easier to just run toslink out of the joying into an aftermarket amp like a mosconi. There is no point going toslink -> most then most -> toslink again. You might as well by pass most all together”

^ is that an accurate statement? If so , will the old speaker wires hook up to the Audison or helix amps? Without the need for an adapter or harness? Thats kinda why I was hoping with the amps being primarily 2ohm they would work with the factory speakers. But I don’t know.

3. What is the rms of the logic 7 , 9 output channels?

Thanks and I appreciate your response

[ctuna]

The power specs of the output chips are contained in the following link .
There are two types of chips one that powers the underseats and one that powers the doors and other channels .
If you can read the specs it indicates for instance on chip for the under
seats you will see 70 watt peak output at 10 percent distortion and it
also has a 1 percent distortion 55 watts .

The first three links in the BMW stereo types have the wiring and at least ohms per speaker location .

http://www.e90post.com/forums/showthread.php?t=1144129
In the above has the output chip specs somewhere in the thread .
So for something like the underseat's the rms true power at 1 percent distortion
is something like 55 . But 1 percent is still a pathetic output spec.
(see entry 18)

Technic Harness will allow you to hook up the speakers without having to
cut into the OEM harness.

You will have to change out both the Head Unit and the amplifier/dsp at the same time to get the setup you are describing to work .

You will need to at least program out the SOS error that not having the Most Bus Modules and BMW Head unit in place.

[Heytree27]

Originally Posted by ctuna

The power specs of the output chips are contained in the following link .
There are two types of chips one that powers the underseats and one that powers the doors and other channels .
If you can read the specs it indicates for instance on chip for the under
seats you will see 70 watt peak output at 10 percent distortion and it
also has a 1 percent distortion 55 watts .

The first three links in the BMW stereo types have the wiring and at least ohms per speaker location .

http://www.e90post.com/forums/showthread.php?t=1144129
In the above has the output chip specs somewhere in the thread .
So for something like the underseat's the rms true power at 1 percent distortion
is something like 55 . But 1 percent is still a pathetic output spec.
(see entry 18)

Technic Harness will allow you to hook up the speakers without having to
cut into the OEM harness.

You will have to change out both the Head Unit and the amplifier/dsp at the same time to get the setup you are describing to work .

You will need to at least program out the SOS error that not having the Most Bus Modules and BMW Head unit in place.

1. I listed the peak ohms in my op- sure I forgot the “4” on sub ohms but damn man. They don’t list the rms. I looked through all of your links and none of them addressed my unique situation of removing HU and amp plus keep I g factory speakers. Do you see why I’m asking these questions? I contacted mo bridge before you even recommended them to me.

2. Is this the harness:

https://technicpnp.com/product/logic...-applications/

3. Is running 75w or 100w rms on the factory all speakers besides the subs a problem?

4. Again, thank you.

[ctuna]

1 I don't know what the max power is that the stock Logic 7 speakers are the output chips give you a suggestion . Many people have put after market amps on them here. You should look for those threads.
2 yes that is the harness. but if you run the toslink from and aftermarket head unit to and aftermarket amp that accepts this it would be easier than running 4 analog channels .
3 again there are many people that keep there Logic 7 speakers and run an aftermarket amp.
The under seats should be able to accept more power .

[Heytree27]

Can you elaborate on point #2? Is this harness that allows for factory speaker wires to connect to an aftermarket amp ? Just want to make sure.

I’d honestly say there aren’t al lot of threads of people using all of their factory logic 7 speakers with an aftermarket amp in an e9x. I’d gladly be proven wrong though.

[Heytree27]

Originally Posted by ctuna

1 I don't know what the max power is that the stock Logic 7 speakers are the output chips give you a suggestion . Many people have put after market amps on them here. You should look for those threads.
2 yes that is the harness. but if you run the toslink from and aftermarket head unit to and aftermarket amp that accepts this it would be easier than running 4 analog channels .
3 again there are many people that keep there Logic 7 speakers and run an aftermarket amp.
The under seats should be able to accept more power .

Are you sure this harness isn’t for connecting an aftermarket amp to the logic 7 system (I.e. head unit) ? It has MOST inputs within the adapter which leads me to believe it’s supposed to be used with the factory head unit.

Are the speaker wires for the logic 7 factory speakers different than any other speakers you would use to hook up to an aftermarket amp? That is the crux of my question.

[ctuna]

If you read the description of the harness it says it's for those that want to
completely replace the amp and includes the analog cables to run the standard
RCA's from the new head unit (this is often done with the OEM head unit when programming it to analog output for amps that have no optic ability ). It might include a most jumper to complete the Most loop for those still using a BMW Head unit so the Most bus stays intact.
You will not have a most connector at your amp and you will no longer have a Most Bus if you remove the stock head unit.
But you are not doing that because you are running a toslink cable for the output of your head unit at least that is what you said.

There are two plug on the Logic 7 amp one is the BMW optical Most Bus the other is the Main Connector which is power and speakers.

If you are ripping out the head unit you are ripping out everything on the Most Bus also if you have PDC that will no longer work.

The thing that makes a professional install is reversibility which means not cutting any wires .
The main connector on the right to the amplifier breaks out all the amp to speaker signals and labels them making
it easier to hook up the speakers . And also makes the install reversible.

From wiring diagrams for the members

http://www.e90post.com/forums/attach...1&d=1209780605

the connector on the right(in the technic link) is the speaker output and (power line from the front of the car. you won't be using that)
You also need a power kit to run power from the battery to the amp and it should be fused)
And your amp will need to use signal sensing for the power from that connector as a turn on signal .

(Please note) All the alarms and dings come through the factory stereo and there must be some consideration for that.
Some do it by using something like a connects2 harness which is capable of that.
side effect lots of side effects.

https://connects2.com/Product/ProductItem/CTKBM011
https://connects2.com/Product/ProductItem/CTSBM006

[Captain Buumer]

You can get very good system with 3 way active front (Tweeter + 4" + underseat)+ rear subwoofer.

Also rear 4" is mostly for PDC & they are reduced by 50% so they don't ruin the front concert.
Center channel is useless anyways in our cars. Wasted amplification. Why would you put 4" center channel when you already have 4" speakers on both sides. It just pulls the soundstage to to right and you are no longer in the exact center where all the music happens. You're like bypasser hearing concert far away somewhere on the right.


Ideally you tune with DSP to get feeling like you are driving towards the music - time alignment.
You can easily differentiate different instruments location - drums on the left, singer right in front of you with the pianist slightly to the right. You can feel with your back every punch of bass note but at the same time hear the piano note right when the pedal is let go - perfectly balanced.

Originally tweeters are off axis which means they are pointing towards the steering wheel and not to your head. You loose some clarity if you don't change their angle but this means they need more delicate tuning - otherwise they are too dominant.

Even the E9x base audio setup was damn fine (with added tweeters) & some DSP tuning. it's just they tend to *pop* when you turn the volume higher.
I have 100W RMS amplification active setup and it deafening when i crank it to the max. There is zero distortion and really clear audio but it's way too loud.
15...35W is average i think i use.

Any speaker behind driver position are not really worth the amplification (except the subwoofer). Create reflections and just mess up the spectrum - more so in Logic 7 where passive crossovers are used - this reduces output and you don't have flexibility to individually fix the dips and highs.

In the end stereo always sounds cleaner and better. Buy 2 really good speakers vs 6 average ones? Math supports this statement.

Get some 8+ channel DSP/AMP combo.
Keep OEM HU for sake of having functional car.
Wire the fronts as active and as much of rear as you have channels left (subwoofer also).
This way you get most for your investment.
But you will end up wanting subwoofer also when you have this because naturally we want more and bass adds alot more.

Then you get miles better system than L7.

But the main magic comes from proper tuning which takes time to setup.

If you ask shop to do it then most probably get what the tuner thinks is sounding "right".

If you learn all this stuff & DIY you get exactly what you want and when you feel like something is off you can play around.

Most people are happy with what they get. But once you have experienced a really well done system - you tend to expect that sort of quality everywhere.

You could retrofit Combox to get bluetooth+Phone+USB playback.

Don't expect home audio quality from the car. In the end road noise drowns all the clarity and this is all pointless.

[ctuna]

He wants to replace the Head Unit with non OEM
you know what a can of worms that is .

[Heytree27]

Originally Posted by ctuna

He wants to replace the Head Unit with non OEM
you know what a can of worms that is .

Can of worms? I’m sorry but you’re not really explaining what you’re saying. The technic PnP harness says no cutting of any OEM wires which you pointed me to. So I would still have the factory head unit, if need be.

I’ve seen plenty of threads of people replacing the headunit— most common issue seems to be the SOS code but I need to get that coded out anyways. I don’t even think there is anymore software updates for my car.

Some people will only use OEM, I am not one of those people. But I do want to know what the pros and cons are,
I would appreciate if you explained this can of worms

[ctuna]

The point is also that and aftermarket head unit may not support the alarm sounds and dongs that come through the stereo as the sound system in all but the 2006 model has no separate speaker for those.

Some head unit's do but some require a separate head unit adapter harness to get the alarms to work and the buttons on the steering wheel to work.
This is a separate problem that comes with aftermarket head units.

That's why I put in the connects2 harness link.

Technic harness is for the Amp only you said you where changing the head unit at the same time .

This is why Captain Bummer said "keep the OEM head unit to have a functional car"

Also if you ever have to take the car to a BMW dealership they may tell you to take a hike if the aftermarket head unit interferes with
there diagnostics.

For instance this head unit seems to be popular in Europe.
https://www.joyingauto.com/joying-9-...1-e92-e93.html
Not endorsing it but it designed to take care of some of the interface problems with aftermarket head units in an E90.

[Heytree27]

I actually have that exact joying. But regarding the technic PnP harness: what do I need to be coded to stereo/Hifi, if I’m ripping out the logic 7 amp/hu?

[ctuna]

Only the SOS function if you are replacing the Head Unit and Amp both with aftermarket units . And you might as well unplug that or those modules in the Trunk floor it could include SAT radio if you have that.

The Head Unit programming determines the system type no Head Unit no system type.

[Heytree27]

I’m reading the technic PnP harness description again and it specifically says it is “ designed to replace the MOST (fiber optic inputs) OEM amp …”

It says it will not work if coding is not performed.

So if don’t need coding , why would I need this harness?

Again back to my original question— can the logic 7 speakers connect to an Aftermarket 8 channel amp? Do I even need a harness? Or can the wires just connect to the outputs of the amp?

[Captain Buumer]

Can the logic 7 speakers connect to an Aftermarket 8 channel amp?

Yes. Speakers just need amplification.
Logic7 is just an amplifier that is not powerful enough for the 13 something speakers connected to it.
The Tweeter & midrange are parallel with high pass capacitor so they are 2 ohm.
Others should be 4ohm.
Keep this is mind - you need to either modify the wiring or specify the ohm rating in the software of your DSP if you plan to just swap out the amplifier and keep all the speakers.

Do I even need a harness?

Think of it this way:
if you ever want to sell the car and keep your own amplifier then how to you get the Logic7 system working again?
It's way easier when you just plug in the Logic 7.
it's way harder when you have soldered new connections and need to undo everything.

If you don't care then it's easiest to just cut the wires from connector -> solder to the new amplifier wiring -> done (over 100$ saved)

The technic harness coding part only matters if you plan to keep the original HU.
Meaning HU was outputting optical light (before coding) -> analog low level signal (after coding).
Since you will be using Aftermarket HU this coding part doesn't apply.

[ctuna]

So many people are bad at soldering and can't keep track of what there doing the potential to mess things up is very high and also solder joints are more prone to failures. Nice thing about the Technic Harness is every-wire is labeled.
The difference between a Pro Install is that none of the factory wiring it butchered and the install is reversible.

You could use high quality wire taps but that still is kind of ugly and not as good as not screwing up the factory harness.

I would go with the Technic harness but the following is best non solder connection method I know of
You don't need the Most Jumper in the Technic Harness but it has RCA's to run from the output of the new Head unit if
you choose or have to run analog to your amp .

https://www.posi-products.com/index.html

[Heytree27]

Originally Posted by Captain Buumer

Yes. Speakers just need amplification.
Logic7 is just an amplifier that is not powerful enough for the 13 something speakers connected to it.
The Tweeter & midrange are parallel with high pass capacitor so they are 2 ohm.
Others should be 4ohm.
Keep this is mind - you need to either modify the wiring or specify the ohm rating in the software of your DSP if you plan to just swap out the amplifier and keep all the speakers.


Think of it this way:
if you ever want to sell the car and keep your own amplifier then how to you get the Logic7 system working again?
It's way easier when you just plug in the Logic 7.
it's way harder when you have soldered new connections and need to undo everything.

If you don't care then it's easiest to just cut the wires from connector -> solder to the new amplifier wiring -> done (over 100$ saved)

The technic harness coding part only matters if you plan to keep the original HU.
Meaning HU was outputting optical light (before coding) -> analog low level signal (after coding).
Since you will be using Aftermarket HU this coding part doesn't apply.

Okay I will get the harness. Thank you for explaining the soldering part, I do want to avoid that.

Regarding the ohms:
Can the subs under the seat handle 2ohm? Ive read that you can always go lower but never higher.

[ctuna]

The underseat subs have the ohm rating . Amplifiers have a watts out rating at usually at 2 or 4 ohms.
BMW claims the stock under seats are 4 ohm or so BMW says in the spec sheet they don't give a max wattage.

You have to consult the specs for whatever amplifier you buy.

Amplifiers usually have two output ratings at 4 and 2 ohms for watts out RMS at given distortion level.

Speakers have wattage and power , however OEM car systems for BWM do not advertise the speaker max and other wattage specs.

[Heytree27]

Originally Posted by ctuna

The underseat subs have the ohm rating . Amplifiers have a watts out rating at usually at 2 or 4 ohms.
BMW claims the stock under seats are 4 ohm or so BMW says in the spec sheet they don't give a max wattage.

You have to consult the specs for whatever amplifier you buy.

Amplifiers usually have two output ratings at 4 and 2 ohms for watts out RMS at given distortion level.

Speakers have wattage and power , however OEM car systems for BWM do not advertise the speaker max and other wattage specs.

I guess what I’m asking is - can the 4ohm subs tolerate a 2ohm amp? The Helix amp I’m looking at is rated at 2ohm at 75 rms.

[ctuna]

There is no such thing as a amp rated in ohms.
The output of the amp is rated in RMS watts if it's a good one and there will be
distortion spec to.
You need to study some basic electronics.

That amp will deliver 75 at into 2 ohms load or less into 4 ohm load .
You will usually see both a 4 and 2 ohm rating in the amp manual .

Terms to know RMS power
peak power
distortion number at power .

look for articles on matching speakers to amps like this
https://audiointensity.com/blogs/car...ications-guide