BMW 1-Series Forum (F20) 135i - > Second Generation 1 Series Forum > 2012 BMW 1-Series Sporthatch (F20) Discussion > F20 Base Sound System Upgrade: Is it safe?
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      06-04-2022, 07:39 PM   #1
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F20 Base Sound System Upgrade: Is it safe?

Thereís a lot of discussion online, especially on the f30 forums, on the safety of upgrading the base sound system. I thought Iíd add my two cents to this discussion.

I have the base sound system which consists of 6 speakers (4 mids + 2 subs) and no dedicated Amp. My plan was to upgrade the mids and add tweeters without spending too much money.

First things first, having no dedicated amp means that the amp is actually a board inside the head unit. I wanted to make sure that the HU can support the changes Iím going to make.
The mids that came with my F20 are the 65139288769. They are 8 Ohm speakers and are connected in parallel to the 4 Ohm subs under the seats. One thing to keep in mind is that a speaker's impedance is a function of frequency. The impedances I mentioned above are nominal impedances which should be the minimum impedances or at least very close to the minimum. This means that the minimum impedance of the two speakers together is 2.67 Ohm. The mid also has no capacitor on it like the base e90 speakers used to have. Those two facts lead me to believe that the HU amp can support 2 Ohms. It wouldnít make sense to a have a 2.67 Ohm load on a 4 Ohm channel from the factory.
To make absolutely sure, I spent a few minutes getting to the head unit and found out it's a Magneti Marelli EN2 which seems to be the same HU as the Entry Nav but without the navigation. I found the Entry Nav technical Specs online. You can too by googling "Manual-para-referencia_EN2". Unlike its title, it's actually in English. I found this on page 123:

Now that I know that the head unit can support 2 Ohm speakers, what remains is to make sure that the speakers are indeed 2 Ohm. The parts I got were the 2-HK-MIDHORN-956 from AliExpress and Skar Audio TWS-01 tweeters from amazon. Theyíre both 4 Ohms, but the tweeters come with a 2KHz High Pass Filter (crossovers) and the mids are super lacking when it comes to high frequencies which makes me think that their impedance at high frequencies rises rapidly.
Here are the mids with and without the tweeters:
This means that mids and tweeters should remain above 4 Ohms. A 4 Ohm load (mid + tweeter) in parallel with another 4 Ohm load (sub) is 2 Ohms. This means that the speakersí impedances (all 3 of them that are being driven by the same channel) should never fall below 2 Ohms.

The main problem with having a lower impedance than the maximum is the increased current consumption and overheating. However, by looking at the specification sheet, the amp seems to have protections against both. Additionally, I never raise the volume above 50%. Most of the time I have it at around 25%. Considering that doubling the volume increases the power consumption by 4 times (if Iím not mistaken), that Iím sticking to low volumes, and that the HU can support full volume at 2.67 Ohms, Iím not too worried about overloading or overheating the head unit.

I did the upgrade a few days ago and everything seems to be fine. Iím quite impressed by the improvement in sound quality. Knowing me, Iíll probably end up deciding to add an amp at one point in the future, not because I want better sound but because modifying my car seems to be really fun. For the time being however, the mids and tweeters upgrade is enough.
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      08-03-2022, 11:17 AM   #2
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I have seen many people upgrading to H&K system so I guess it is safe if you use that amp. I'm planning to upgrade to H&K myself since the car came with basic Hi-Fi and It sounds awful. From what I read online it is fine if you install the H&K subs even they are 4ohms instead of 8ohms like the Hi-Fi ones. that will generate some heat at the amp for sure but if you don't push it to the limit I think it would be fine.
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