[Damaskus325]

I guess I could run my Focals on 2 front channels, the under seats on the 5 and 6 channels and keep my Boston sub running on its current amp then. I don't really need my rear speakers anyways. Question is will 175w to each of the under seats fry them? That's considerably more than the power they are getting now.

[alexwhittemore]

Originally Posted by Damaskus325

I thought technically, the OEM speakers in the HiFi are 4 ohm but the factory amp wires them in parallel with the tweeters making a 2 ohm load.

I'm now nearly certain this is the case. If "all the speakers in the hifi setup" were 2 ohm, that would mean the amp channels each drive 1 ohm loads, which would be silly.

Originally Posted by ctuna

Are you sure you have a Hi Fi 676 system the wiring is pretty simple no parallel wiring except for the tweeters and mids in the door.(which is taken care of by the aftermarket crossover)

all speakers in the Hi Fi system are 2 ohm
The stock amp has 6 channels (2 for floors 4 for doors/rear deck)

Originally Posted by Damaskus325

I am positive I have the Hifi system. I took the OEM speakers out to see how my Focals would sound with the factory amp (awful by the way) and I distinctly remember the tweeter and speaker stamped with 4 ohm. I assume the rear speakers are the same. ...

I ended up buying the OEM replacement driver for the front. Neither the replacement nor either of my original drivers are marked with their impedance - not to say that none were, ever, but in light of that...

Originally Posted by ctuna

Documentation disagrees with you and when I took mine out they
were 2 ohm. And also measure that through an ohmeter.

http://www.e90post.com/forums/attach...2&d=1266451970
from the above.
channels
10 loudspeakers
• 2 treble loudspeakers, front 26 mm
• 2 mid-range loudspeakers, front 100 mm
• 2 bass loudspeakers, 217 mm
• 2 mid-range loudspeakers, rear, 100 mm
• 2 treble loudspeakers, rear 26 mm
Bandwidth: 40 Hz to 20.000 Hz
Max. acoustic pressure: 104 dB
Amplifier power:
2 x 40 W (2 Ω) Bass
4 x 25 W (2 Ω
Note the under seats are 2 ohm also.

I think both of you might be misremembering seeing markings at all. See attached photo - that's all that's written on my original speaker, anywhere.

That documentation also agrees with my assessment. It says 2 treble, front, two mid, front, two treble, rear, two mid, rear, two under-seat. That is to say, FR/FL/RR/RL are all tweeter+mid pairs, wired in parallel. If all of those are 4 ohms, that means the channel load is 2. Totally consistent with 2 ohms by 6 channels on the amp.

Also, ctuna - measuring the DC resistance of a speaker is all but meaningless - resistance is not the AC impedance we're talking about here. I measured both old and new speakers with an LCR meter at 1kHz and got around 3.6 and 3.8 ohms. That's 4 as far as I can tell. Using 120Hz instead shows about 22 ohms - subwoofers these are not. At DC I get 2.8 ohms, which seems a pretty good indication that it's not the measurement of interest.

In other words, replace your hifi amp with a mass market amp and you'll probably have a bad time, because those channels won't be stable down at 2 ohms load. But replace any individual speaker (not the actually-2-ohm under-seats) with a different 4-ohm speaker, and you'll be fine.

EDIT: Also, FWIW, that document linked doesn't mention ANYWHERE what any individual speaker impedance is. It says

Amplifier power:
2 x 40 W (2 Ω) Bass
4 x 25 W (2 Ω)

Which is to say, the mid-high channels drive 25W @2ohm load. NOT that any individual speaker is 2 ohm. We can reasonably assume, form that info, that the stock underseats are 2ohm, since nothing else is plugged in. But in technical point of fact, it would be equally valid to describe the amp as above if the underseats were 4 ohms drawing 20 watts each.

[ctuna]

If you don't believe the BMW documentation there is no point for
me to argue with you.
You can believe what you want but this is what has been listed on this
board since early aftermarket builds starting as early as 2008.
I know the actual impedance of a speaker won't necessarily mean it's
resistance measurement is the same.

"I'm now nearly certain this is the case. If "all the speakers in the hifi setup" were 2 ohm, that would mean the amp channels each drive 1 ohm loads, which would be silly."

whats your logic for this conclusion?
Most would exclude the tweeter impedance.
I don't know how you could just assume that the tweeter is the same and now it's a 2 ohm tweeter in parallel with 2 ohm mid.

When you buy a set of component speakers it lists the
impedance for the pair (tweeter and mid )as a matter of convention. This the standard for the auto stereo industry. Don't see anybody ever specing it any different . But it might be in ultra high
end.

[alexwhittemore]

Originally Posted by ctuna

If you don't believe the BMW documentation there is no point for
me to argue with you.

The problem here is we're reading different meaning from the same line of that documentation. See my logic at the bottom of the post - the documentation describes amp channel parameters, which holds as accurate if each mid-high channel is driving two parallel 4 ohm speakers. At the risk of too much detail, you MIGHT be used to "two 4 ohm components IS 4 ohm!" because of coaxial setups and component setups using passive crossovers. A properly matched passive crossover could well present two 4 ohm drivers in "parallel" as a 4 ohm load over the entire range. But we know that's not the design here, because the wiring harness goes straight in to the midrange, not through a branch of a crossover first. There does appear to be some kind of blocking filter in-line with the tweeter, which would make sense to block low frequencies. But in this wiring, what that'd really do is present a 4 ohm load down at relatively low frequencies (tweeter blocked and not in play), and a 2 ohm load at higher frequencies where both speakers are drawing power. From an amp loading electrical perspective, that's totally acceptable. From an acoustics perspective, it'd tend to make the overall output a little high-heavy rather than well balanced, but, like... yeah, makes perfect sense with the stock setup of this car

You can believe what you want but this is what has been listed on this
board since early aftermarket builds starting as early as 2008.

Which is why I assumed until making my own measurements that it was the case. But then, it's often the case that a herd of non-professional enthusiasts happens to get it wrong. The real question if you assume the crowd is wrong is "why haven't they figured it out yet, wouldn't someone have noticed?" and the answer here, I think, is "probably not" - generally anyone on the forum who's spent the money on speakers either buys a set designed to work with the stock amp and doesn't question that (bavsound), or also changes out the amp. Interesting note here, bavsound refuses to quote speaker impedance for their drop-in setup for basically this very reason - needless confusion. https://www.bavsound.com/Product/sta...-bmw-e90-hi-fi (see FAQ). As it happens, one of the other "drop in replacements" suggested in this very thread was the Helix Match series - they advertise 4 ohm. To be fair, it's unclear if they intend those to be installed in parallel with the stock tweeters, since they don't provide OEM-compatible connectors. This confusion is part of why I didn't buy them - maybe Bavsound is on to something there, hah.

"I'm now nearly certain this is the case. If "all the speakers in the hifi setup" were 2 ohm, that would mean the amp channels each drive 1 ohm loads, which would be silly."

whats your logic for this conclusion?

Sure - if every individual driver in the system is 2 ohm, that means FR/FL/RR/RL are all pairs of 2ohm in parallel with 2ohm = 1ohm. (That wouldn't apply to the underseats, since they're solo - they'd still present a 2ohm load)

[Damaskus325]

The other issue here is that I have searched for months about changing my system and I think I may be the first to use the amp I have in my upgrade. Everyone who replaces the OEM amp seems to use the JL 600/6, which is due to the balanced differential output of the OEM head unit. In addition to that factor, the JL amp is also 2 ohm stable across each channel so what the factory speaker rating is hasn't posed an issue to most. I have quite a bit of audio gear from my E39 and opted to change my head unit, so no need for any special amp. I have some old gear gear that I actually wish I could fit but can't because of the stupid E92 slim doors. I would put my Boston Pro50SE babies in but I have opted to make this install easier and go with speakers I know fit. Anyways, I was simply going to use my Sony DSP amp to run everything besides my sub and can't because apparently, these OEM speakers are 2 ohm and my amp is 4 ohm stable for 4 of the 6 channels. Like it told ctuna earlier, I will just amp my Focals up front and under seats and leave the rears dead.

[ctuna]

If you read the description and wiring diagram for Hi Fi 676 option there
is a dedicated channel for each location defined by a door being a location or
a floor on each side being a location. The only system that uses parallel connections is the base system , defined as the stereo system, where the floor is in parallel with a door and there is no separate amp only head unit power .

There is even a block diagram of the wiring for the hi fi system.

http://www.e90post.com/forums/attach...1&d=1209780865

nothing is in parallel its a 6 channel amp.

[alexwhittemore]

Originally Posted by Damaskus325

Anyways, I was simply going to use my Sony DSP amp to run everything besides my sub and can't because apparently, these OEM speakers are 2 ohm and my amp is 4 ohm stable for 4 of the 6 channels. Like it told ctuna earlier, I will just amp my Focals up front and under seats and leave the rears dead.

FWIW, I do believe you could still stick to that original plan even with 4ohm channels, as long as you go to each mid/tweeter pair and install a crossover that splits the frequency range so at no frequency is there <4 ohms of total load.

Of course, there's probably a reason BMW wired these components this way, it it probably has something to do with sounding bad if you do what I suggest. But then I don't know - maybe it was just cheaper to design in a 2ohm x 6 amp than to design in proper crossovers at each site.

[alexwhittemore]

Originally Posted by ctuna

nothing is in parallel its a 6 channel amp.

Ahh - that's where you're verifiably wrong. That wiring diagram is correct, for sure - notice how there's a + and - wire shown on each channel? But on the two "Mid-bass" channels there's only one cone shown, where on each of the other 4 there's a mid and a tweeter? The mid and tweeter share the same plus and minus on their respective channel - in parallel.

EDIT: mac mangled the annotated picture. If it's not sufficiently obvious, both plugs share contacts - same pieces of metal going between both, and the locations are interchangeable when you're plugging in the tweeter and amp-side. Also FL=front left. Not FC, my writing is just awful.

[Damaskus325]

Hold it. I just forgot about this. Focal made a drop in component set for the E90. It wouldn't fit the E92 because the depth is slightly more shallow. Anyways, according to Crutchfield, they are 4 ohm drop in. If an E90 had the hifi and these fit, wouldn't the 4 ohm impedance cause an issue? They wouldn't get enough power right? Here is the link.

https://www.crutchfield.com/S-O6lbCD...n-IFBMW-S.html

[Damaskus325]

Why would a premier speaker company like Focal design drop in speakers that wouldn't fully utilize the factory amp?

[ctuna]

component speakers are speced as a set not as separate speakers
with equal impedence. The likely hood is that any tweeter has much
higher impedance than the mid its associated with .
It also draws a fraction of the power because of this as it only has to to amplify
the high frequency's. It doesn't have to power a big cone with bigger
mechanical excursions.

Your picture might be accurate but you really think that
a tweeter has equal impedance or draws equal power in relation to its mid.

Focal makes different grades of 4 inch component sets.
The power they are happy with is different between the
models.

Some might be designed for a BMW OEM system but which
one of the three. They all have different outputs.
Bavsound try's to solve the problem by offering different
impdences as do some other company's

[Damaskus325]

Your right about different sets of Focals but those are made SPECIFICALLY for our cars. If they are drop in speakers that are 4 ohm, wouldn't that make them waaaay under powered with the hifi amp? It gives out 4x25w at 2 ohm supposedly right? The Focals would get half of that maybe. 12.5w to 40w rms speakers would sound awful.

[ctuna]

I looked at my old hi fi speakers and
the tweeter is labeled 4 ohms and measures about that
bypassing the filter capacitor that is inline with them.
the woofers or mids aren't labeled and measure 2 ohms
I realize this is just a static resistance measurement but
I don't have a signal generator and scope to do a frequency chart with voltage and current measurements.

[Damaskus325]

I knew I wasn't crazy! I knew I saw 4 ohm on something in there. At least I feel better about that. If you measured 2 ohms, I guess there is no arguing with a multimeter. I should have just used mine and put that question to bed. Thanks man.

[ctuna]

Its not really the correct way to measure impedence but it
often gives a relative indication. My Jehenert Xe 200's measure
7 ohms of resistance but they are 4 ohm rated speakers.

I think that bavsound designed there doors for the Logic 7
amp .

[alexwhittemore]

Originally Posted by ctuna

I think that bavsound designed there doors for the Logic 7
amp .

Again, not really relevant, since they don't list impedance. But no - they have drop-in kits for both hifi and top hifi. Not clear whether they use the same drivers, but visually it looks like they do.

[Damaskus325]

Originally Posted by alexwhittemore

Again, not really relevant, since they don't list impedance. But no - they have drop-in kits for both hifi and top hifi. Not clear whether they use the same drivers, but visually it looks like they do.

That's what it looks like to me also. The Focal component set, Ifbmw-s, and the coaxial set, ifbmw-c both state they are 4 ohm speakers. They list their speakers impedance because they assume some may use an aftermarket amp down the road. The weird thing about Bavsound is, they state their speakers can handle 100w rms for an aftermarket amp but state no ohm rating. They have to know most competent audiophiles will match there amps to components based on power handling AND impedance but they give no such data. Mind boggling.

[ctuna]

They have never published there specs ,(at least on there door
speakers) which is one
of the big reasons I would choose something else.
They suggest that an aftermarket amp of around 50 watts
a channel.

There original purpose was just to supply speakers.
They promised and amp for years never came up with one
and now offer a Helix indirectly through Bimmertech .

There are many drop in speaker kits now.
Not from the usual Japanese company's though.

[alexwhittemore]

Originally Posted by ctuna

I don't have a signal generator and scope to do a frequency chart with voltage and current measurements.

Hey, it turns out, I do!

The line of 0.1X gain corresponds to a load of 4 ohms.

It's a 4 ohm speaker.

[Damaskus325]

Well ok then. This keeps getting better and better. It now makes sense why Focal would make 4 ohm coaxial and component sets specifically for these cars. I didn't think they were idiots. Im just going to at least try running my OEM rears with my amp at minimum gain. If anything, my amp should go into protection mode if the impedance of the speakers is genuinely lower than 4 ohms.

[alexwhittemore]

Originally Posted by Damaskus325

Well ok then. This keeps getting better and better. It now makes sense why Focal would make 4 ohm coaxial and component sets specifically for these cars. I didn't think they were idiots. Im just going to at least try running my OEM rears with my amp at minimum gain. If anything, my amp should go into protection mode if the impedance of the speakers is genuinely lower than 4 ohms.

No, that's the opposite conclusion. The speakers are 4 ohms. Because each of the 4 main channels has two speakers in parallel attached to it, the amp sees a 2 ohm load on each channel.

The point is, replacing any (non-mid-bass underseat) component in the system with a 4 ohm aftermarket will work. But replacing the AMP to drive the otherwise stock system DOES require a 2ohm by 6 channel amp.

Another acceptable option would be using a 4ohm amp, but unplugging the tweeters on all channels so only the 4" components are plugged in (of course, that'll sound extra meh).

Yet another acceptable solution would be to rewire the stock tweeter and 4" with a proper 4 ohm crossover to both. But there's probably a reason BMW didn't do this in the first place, and it may be that the setup sounds bad if you cut off the high end from the 4" drivers.

[ctuna]

they use a single inline capacitor on the tweeter wire connector assembly
for a high filter. No bulky crossover to install and its cheap. But I don't
think its as sophisticated as anything you get with a component set in
terms of a crossover.
Backseat speakers don't add much to the sound according the the pure stereophiles.
I think there is a bigger chance of burning up the speakers than damaging
the amp.