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Model S - DIY UHFS Audio Upgrade - This may be a far shot

MSP90D

New Member
Jun 28, 2021
2
0
San Francisco
Hey TMC Family,

I purchased a 2016 MSP90D directly from Tesla, but got shafted on the fact that it said online premium sound and came with no UHFS system. To my "non-surprise" Tesla basically said take it or leave it and lose your deposit and transportation fee. So I took the car and really was upset about the stock audio system.

I replaced the speakers to S4D Light Harmonics, but the MCU2 can only handle so much output so the low end is still lacking a bit. Rich Rebuilds never got back to me on Facebook after a couple of comments .... so on so on ... long story short I'm trying to see if there's any way to add in a stock UHFS amp to supplement the MCU2 internal amp. (If the wiring harness is even there, or if it can be added :) )

I've read so many forum posts about the DC-DC converter going out when putting in an after-market sub and amp combo that I want to try to go as original as possible. If anyone has attempted or knows if it's even possible to DIY the UHFS amp into the MCU2, and then potentially run the cables for the stock RH Tesla sub please let me know. Either or both works just anything to increase the Low End without potentially blowing the DC-DC and voiding my warranty.

Thanks All.
 

matt00x19

Member
Dec 2, 2020
5
9
Portland, OR
MCUs with the non-UHFS system will provide analog speaker level outputs directly to the cabin speakers (which is what you have now). They are coded to power speakers directly. MCUs with the UHFS system will provide the separate premium amplifier with a digital audio signal, which will be interpreted by the processor inside the premium amp and converted from digital to analog. I can almost guarantee that the physical harnesses are also different between each sound package. Even if this was possible in theory, you would need to source extra 8 inch door woofers, 3 inch dash corner speakers, 3 inch rear hatch speakers, and the sub enclosure. You would also need to run speaker wire from the premium amp to each speaker, as the non-UHFS cars likely don't have wires running to those unused locations.
 

beatle

Active Member
Aug 31, 2019
1,269
736
Springfield, VA
UHFS isn't much better than the standard system. It's nice to have a midrange, and the larger midbass drivers and subwoofer help a little bit, but it's nowhere near what even a moderate aftermarket system can do. If you're going to go to such lengths/expense, I would add an amp/DSP and a sub. A good midrange in the stock location is also worthwhile. It might cost more (or not) than the UHFS swap/upgrade, but it'll sound a heck of a lot better.

My own anecdotal evidence is that the ~1100w of aftermarket amplification in my car over the past year and a half has been no problem for the DC/DC converter. Remember, amplifier duty cycle is generally only 1/8 of its maximum unless you're blasting sine waves to the point of clipping the amp.

 

2101Guy

Active Member
Jan 6, 2020
2,267
3,317
USA
One of my loaners once had UHFS. Drove it on a highway trip for couple hours. (My own S did not/does not have UHFS). Main difference by far was bass capabilities in the loaner with UHFS.

Got this and boom, even better bass range/power (adjustable) with this setup. And looks totally stock.

 
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jjlawyer

Member
Nov 8, 2018
36
20
Los Angeles County, CA
There is no good reason to try to shoehorn the UHFS into a non-UHFS car. If you have the light harmonics already, just add in an aftermarket 4 channel amp. I haven's spent much time with the UHFS but a decent aftermarket amp will be way better. I added a 12 inch sub box first and then later added aftermarket speakers in the doors with amps. I was surprised how much bass you can get out of the 6 1/2 inchers in the doors but I did dynamat them. So I would say see if there is enough bass for you with just door speakers and amp as the first step.
 

MSP90D

New Member
Jun 28, 2021
2
0
San Francisco
Thanks all - I forgot to mention that I did dynomat all the doors as well. The reviewers on youtube were right about the light harmonics only making sense in the front 2 cones because there isn't enough juice coming from the stock amp on the back of the MCU to push anymore to the rears.

My real worry was blowing the DC-DC or having an issue with the 12V battery which is why I was trying to go UHFS stock if it was possible. Any suggestions on an AMP that has the same type of on/off technology as the light harmonics speakers. (specifically that they turn off automatically when the car turns off in a matter of a few miliseconds) From reading allot of the forum posts it seems that the issue is the amp staying on and draining juice from the 12v battery which can go out or need replacing, and then by some weird effect also blows out the DC-DC at the same time.

Appreciate the input thus far :)
 

2101Guy

Active Member
Jan 6, 2020
2,267
3,317
USA
I can only report that my same 12v battery has been in the car since I purchased the car (12/2019) and I've had the NVX sub/amp in the car for about a year or so now. And I've not had any issues at all. And my "stats" app shows my phantom drain to be 0.19 "which is better than 70% of users", per the app.
 

Saimaannorppa

Member
Sep 3, 2017
216
257
Finland
I bought an inventory car in 2017 since it had all I wanted except UHFS and had a 15% discount. Figured that aftermarket installers typically do a much higher quality job than car companies for the same money spent. When I replaced standard speaker elements with Light Harmonics, noticed that this is true for Tesla as well: the elements are very cheap and they rely on DSP only to get (in)adequate sound.

I've had a 4 channel 800w class D amp and a 500w 1 channel class D amp for three and half years and no issues. They do switch on/off based on signal in matter of a second when powering on and a few seconds when off.

Based on my experiences, the first thing to do in order to improve the low end is to "dynamat" your doors and add soft padding as well (as you would have inside a loudspeaker). Doors are basically loose and rattling loudspeaker enclosures without it. It's not too hard but aftermarket installers do this as well. No need to do rear doors, the MCU amp cuts out all bass to rear doors anyway.

If you'll have an aftermarket sub fitted, "dynamat" is needed on surfaces in direct or close contact to the subwoofer enclosure as well, to get high quality bass. I noticed a big difference after installing a similar alubutyl product than dynamat in rear wheel arch outside and inside and when filling some echo chambers in trunk with soft foam. My aftermarket sub is basically in same area with a bit larger custom enclosure than the standard UHFS box.
 
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