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      03-07-2020, 08:19 PM   #1
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F31 Underseat Sub upgrade

Hi all, I'm a new BMW owner. 2017 F31 with the HK system. I love the car and the HK system sounds pretty good to my ears but like many others think it just lacks a bit of kick in the bottom end. Thanks to tons of posts on the topic, lots of reading in in this thread https://f30.bimmerpost.com/forums/sh....php?t=1311415 and a few emails with johnung I decided on the following:
  • Earthquake SWSxi subwoofers
  • Polk D2000.2 amp
  • Audiocontrol LC2i Line out converter
  • TechnicPnp wiring harness

I haven't really done many audio installs since I was a kid and was pretty intimidated diving into the wiring on my new car but with all the information available here I decided to take my time and give it a go.

After a few weeks waiting for everything to arrive, we're almost set to go. Things not in the photo: KnuKoncepts sub wiring kit



The F31 has a nice little compartment right at the back of the car that fit the equipment I'm putting in perfectly. I mapped the layout on cardboard and made sure everything fit



Then transfered it to a piece of 1/4" plywood and installed t-nuts to fasten everything down. Height was an issue in this location, that's the reason for 1/4" ply.



I wrapped it in grey felt. The carpet isn't black, isn't grey. I didn't find a match so I went with what I thought would look best, that is for something that'll never be seen.



Bolted it all together and test fit



I looked at a bunch of audio installs on the internet and wanted to do a real nice job so I picked up some flex covering for the wiring. It's a bit time consuming but give a nice result.



That's all for tonight, I hope to get the rest of the wiring done tomorrow.
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      03-07-2020, 09:11 PM   #2
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Quote:
Originally Posted by damack View Post
Hi all, I'm a new BMW owner. 2017 F31 with the HK system. I love the car and the HK system sounds pretty good to my ears but like many others think it just lacks a bit of kick in the bottom end. Thanks to tons of posts on the topic, lots of reading in in this thread https://f30.bimmerpost.com/forums/sh....php?t=1311415 and a few emails with johnung I decided on the following:
  • Earthquake SWSxi subwoofers
  • Polk D2000.2 amp
  • Audiocontrol LC2i Line out converter
  • TechnicPnp wiring harness

I haven't really done many audio installs since I was a kid and was pretty intimidated diving into the wiring on my new car but with all the information available here I decided to take my time and give it a go.

After a few weeks waiting for everything to arrive, we're almost set to go. Things not in the photo: KnuKoncepts sub wiring kit



The F31 has a nice little compartment right at the back of the car that fit the equipment I'm putting in perfectly. I mapped the layout on cardboard and made sure everything fit



Then transfered it to a piece of 1/4" plywood and installed t-nuts to fasten everything down. Height was an issue in this location, that's the reason for 1/4" ply.



I wrapped it in grey felt. The carpet isn't black, isn't grey. I didn't find a match so I went with what I thought would look best, that is for something that'll never be seen.



Bolted it all together and test fit



I looked at a bunch of audio installs on the internet and wanted to do a real nice job so I picked up some flex covering for the wiring. It's a bit time consuming but give a nice result.



That's all for tonight, I hope to get the rest of the wiring done tomorrow.
Wow, very thorough planning and execution! It appears that your Polk amp is 2 channels of 250 watts RMS each into the matching 2-ohm Earthquakes. My AudioControl amp is 2 channels of 150 watts RMS into 2-ohms.

Just a heads up that when I called Earthquake Tech Support during my installation we had a discussion and they cautioned me not to set the amp all the way up so that it was putting out the full 150 watts into the Earthquakes. They recommended setting it at 80-90% of max. I turned down the gain setting on my amp when I first powered it all up. Then I slowly adjusted it up. I never really hit an issue. I was listening for symptoms that I had read. But your amp is putting out more power so you may max out the Earthquakes before you max out your amp.

Please keep us posted. I'm curious how it sounds in your F31.
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      03-08-2020, 12:05 AM   #3
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Thanks John. I plan to set the gains with a voltmeter once I power it up just to be on the safe side, and then play it by ear. I rarely listen much over half volume anyways so I don't expect overpowering them to be a issue.
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      03-08-2020, 08:02 PM   #4
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Day 2. I thought with the time change I'd get a sleep in this morning but no dice. Can't sleep, still tired.

This will get things moving



Started with getting the wiring harness put together. All connections soldered and heat shrinked then flex installed over the wires. This took a bit of time. I'm not a quick mover at the best of times, but I was being pretty methodical on this.



I was able to tuck all the wiring behind the carpet under the rear sill and entered the compartment by cutting a couple of access holes. It made for a tidy installation. All wired up. I'm fairly happy with how it turned out, although I just notice posting the picture that I missed a strap on the RCA flex.



Now you see it



Now you don't



Unfortunately I forgot to grab a crimper from work to install the big terminals on the power and ground feeds so I'll hopefully get to that this week. I didn't install the new Earthquake subs under the seat today as I still want to some bass for my daily commute.

Everything was pretty easy to do for a first timer. It has taken way longer than I figured upon, but that's pretty standard for most things I do.

Last edited by damack; 03-08-2020 at 08:07 PM..
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      03-08-2020, 09:25 PM   #5
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Quote:
Originally Posted by damack View Post
Day 2. I thought with the time change I'd get a sleep in this morning but no dice. Can't sleep, still tired.

This will get things moving



Started with getting the wiring harness put together. All connections soldered and heat shrinked then flex installed over the wires. This took a bit of time. I'm not a quick mover at the best of times, but I was being pretty methodical on this.



I was able to tuck all the wiring behind the carpet under the rear sill and entered the compartment by cutting a couple of access holes. It made for a tidy installation. All wired up. I'm fairly happy with how it turned out, although I just notice posting the picture that I missed a strap on the RCA flex.



Now you see it



Now you don't



Unfortunately I forgot to grab a crimper from work to install the big terminals on the power and ground feeds so I'll hopefully get to that this week. I didn't install the new Earthquake subs under the seat today as I still want to some bass for my daily commute.

Everything was pretty easy to do for a first timer. It has taken way longer than I figured upon, but that's pretty standard for most things I do.
A couple things that I remember from the Earthquake install:

The last six minutes or so of this Kies video show the best way to remove the underseat subs.



The edges of the stock carpet was interfering on top of the subs in some spots so I took some sharp kitchen shears and trimmed it back after the Earthquakes were in place.

It is easier to connect the new speaker wire to the trim posts on the Earthquake spacers before you drop the spacer in place in the sub box in the floor.

Hope this helps!
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      03-15-2020, 02:56 PM   #6
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Well I thought that today I'd be able to get the underseat subs installed and finish it up. I immediately ran into a problem. Using the TechnicPnp adapters, it seems that the Earthquake subs are still too deep. The adapter rings are 1/4" but the bottom of the subs hit the bottom of the enclosure and don't allow them to sit down. I'm not sure what's happened or what I missed here, hopefully google has some answers.
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      03-15-2020, 05:01 PM   #7
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If johnung doesn't give a reply PM him. I'd think it would fit, as the F30 and F31 use the same enclosure.
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      03-15-2020, 05:49 PM   #8
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Quote:
Originally Posted by damack View Post
Well I thought that today I'd be able to get the underseat subs installed and finish it up. I immediately ran into a problem. Using the TechnicPnp adapters, it seems that the Earthquake subs are still too deep. The adapter rings are 1/4" but the bottom of the subs hit the bottom of the enclosure and don't allow them to sit down. I'm not sure what's happened or what I missed here, hopefully google has some answers.
This is a SWS-8Xi install with those spacers without a depth issue: https://f30.bimmerpost.com/forums/sh....php?t=1070841

This is an Eton woofer install that required opening the OEM enclosure opening to fit: https://f30.bimmerpost.com/forums/sh....php?t=1066056

Either the OEM woofer enclosures were changed (those threads are for MY2015 F30) for your model year or something else is making contact with the bottom of the SWS and is not the enclosure. The only BMW with SWS depth issues in the OEM woofer enclosure is the F10 5-Series, and only in one enclosure, AFAIK.
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      03-15-2020, 09:32 PM   #9
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Turns out there were a couple of issues. I put some weatherstripping between the adapter and the enclosure and there was still some interference. What I found was the inner diameter of the spacer isn't quite large enough and the caused the speaker to rock a bit. Also with the spacers, I had to trim the part where the connection is just to get it to fit. In the end I had to trim the ribs on the bottom of the enclosure, add some weatherstripping and trim the spacer. I'm not sure if my 2017 is different than previous model years, but that was a pain in the butt.

I wish I could say the rest of the day went smooth, but it was one clusterf#4k after another. The GTO sensing on the LC2i doesn't seem to like whatever signal BMW is giving it, and when I swapped the bypass jumper it still didn't work. I can jumper the 12v power to the remote in terminal and it comes on, but I'm not sure why the bypass jumper doesn't work.

Then my main fuse holder broke.

So I gave it the middle finger and came back in the house. I'll have to let the patience bucket fill back up before trying again.
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      03-15-2020, 11:04 PM   #10
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I'm not sure how you going to tackle the problem where HK system will slope down the bass from 50hz and below. Without proper DSP and EQ, I don't see a way to boost the freq precisely. Accubass would not work as it only lift the signal from 50hz to 125hz according to their product literature.

https://www.audiocontrol.com/knowled...ass-epicenter/

Last edited by pierreye; 03-15-2020 at 11:11 PM..
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      03-15-2020, 11:21 PM   #11
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Quote:
Originally Posted by pierreye View Post
I'm not sure how you going to tackle the problem where HK system will slope down the bass from 50hz and below. Without proper DSP and EQ, I don't see a way to boost the freq precisely. Accubass would not work as it only lift the signal from 50hz to 125hz according to their product literature.

https://www.audiocontrol.com/knowled...ass-epicenter/
Yes, without gutting the hk amp and processing the raw signal there's going to be limitations. Unfortunately that's a costly venture. Hopefully this will give a bit of a boost to the low end and keep me happy.
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      03-15-2020, 11:35 PM   #12
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Just a suggestion, maybe AudioControl d-4.800 will be a better match. Yes, it's more costly but you can keep your HK and use this to EQ the signal. I'm actually been considering D-6.1200 to drive the front 3 speakers + 2 underseat sub. Advantage would be you can individually set the timing and loudness for front 3 speakers which should give you a better soundstage. Will leave the HK amp to drive the rear speakers.
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      03-15-2020, 11:51 PM   #13
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but if you're still grabbing the signal after the HK amp, wouldn't you still have the HK processing limitations? Or are you able to boost the low frequency using the on-board dsp?
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      03-16-2020, 01:35 AM   #14
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Quote:
Originally Posted by damack View Post
but if you're still grabbing the signal after the HK amp, wouldn't you still have the HK processing limitations? Or are you able to boost the low frequency using the on-board dsp?
You can use the DSP to boost the freq.
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      03-16-2020, 04:23 AM   #15
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LC2i GTO does not work with MOST OEM amps. LC2i requires a dedicated remote signal.

Quote:
Originally Posted by damack View Post
Turns out there were a couple of issues. I put some weatherstripping between the adapter and the enclosure and there was still some interference. What I found was the inner diameter of the spacer isn't quite large enough and the caused the speaker to rock a bit. Also with the spacers, I had to trim the part where the connection is just to get it to fit. In the end I had to trim the ribs on the bottom of the enclosure, add some weatherstripping and trim the spacer. I'm not sure if my 2017 is different than previous model years, but that was a pain in the butt.

I wish I could say the rest of the day went smooth, but it was one clusterf#4k after another. The GTO sensing on the LC2i doesn't seem to like whatever signal BMW is giving it, and when I swapped the bypass jumper it still didn't work. I can jumper the 12v power to the remote in terminal and it comes on, but I'm not sure why the bypass jumper doesn't work.

Then my main fuse holder broke.

So I gave it the middle finger and came back in the house. I'll have to let the patience bucket fill back up before trying again.
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      03-16-2020, 07:05 AM   #16
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Quote:
Originally Posted by damack View Post
Well I thought that today I'd be able to get the underseat subs installed and finish it up. I immediately ran into a problem. Using the TechnicPnp adapters, it seems that the Earthquake subs are still too deep. The adapter rings are 1/4" but the bottom of the subs hit the bottom of the enclosure and don't allow them to sit down. I'm not sure what's happened or what I missed here, hopefully google has some answers.
I used the spacer adapters from Earthquake. They fit perfectly for about $20/pair. The wires had connectors that fit securely on the Earthquake subwoofer. And the spring loaded mounting posts made for a quick install with the 14 gauge speaker wire that I used. I bought them from Walmart online. Attached are some photos.

Part# R8SWS
http://www.earthquakesound.com/index...zoo/item/r8sws
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      03-16-2020, 09:10 AM   #17
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Quote:
Originally Posted by johnung View Post
I used the spacer adapters from Earthquake. They fit perfectly for about $20/pair. The wires had connectors that fit securely on the Earthquake subwoofer. And the spring loaded mounting posts made for a quick install with the 14 gauge speaker wire that I used. I bought them from Walmart online. Attached are some photos.
I'm using the Technicpnp adapters as I'm using the factory wiring and didn't want to cut the connectors off. The spacer depth is the same so I wonder if the sub enclosure is different on mine although that seems odd.
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      03-16-2020, 11:07 AM   #18
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Quote:
Originally Posted by damack View Post
Quote:
Originally Posted by johnung View Post
I used the spacer adapters from Earthquake. They fit perfectly for about $20/pair. The wires had connectors that fit securely on the Earthquake subwoofer. And the spring loaded mounting posts made for a quick install with the 14 gauge speaker wire that I used. I bought them from Walmart online. Attached are some photos.
I'm using the Technicpnp adapters as I'm using the factory wiring and didn't want to cut the connectors off. The spacer depth is the same so I wonder if the sub enclosure is different on mine although that seems odd.
I checked realoem and GetBMWParts. They both show the sub and the subbox being sold as a single part number. I thought maybe there was a part number for the subbox to see if they are identical on our cars. They only show part numbers by type of audio option on the car. I have H/K so if you do also, then they should be identical. See photo.

Try calling Earthquake tech support. I had a question during my installation and I remember the guy being very knowledgeable.
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      03-18-2020, 09:13 PM   #19
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After a minor setback and renewed patience, I got back at it yesterday. The speaker issue resolved, although I still don't know why there was a problem.

Wires connected, heat shrinked, ready to go



This is the what I had to do to the underseat enclosures to get them to fit.




All in, the TechnicPnp adapters do make it simple to use the factory wiring, although I had to trim them around the wiring outlet to fit. This is why I think the enclosures may have slightly changed in size.



Connected up the wiring, again the TechnicPnP harness makes simple work of integrating into the factory system without having to cut or splice anything.



All tucked into place



Power supply done.



After a few problems powering up, notably the Audiocontrol GTO feature doesn't work with the factory system. Thanks Encanto above for letting me know. Then the fuse in the main power fuse holder was broken. I tapped the trigger signal into fuse 146 using an add-a-fuse like many others have done. This shuts it down a few seconds after the engine is turned off. I'd like to find a power supply that shuts down the same time as the rest of the audio system so I can listen for a few minutes if I'm waiting in the car without it running.

I need to tune it up but first impressions are pretty good. With the gains turned down I fired up a few songs with a nice bass line and most of the what I was missing before was there. Kick drums give a nice beat that you can feel in the seat. I'll spend some time dialing it in over the next few nights.

While I did have it apart, I did some experimenting with a test tone. With the subs unplugged I ran a tone to see where the mids kicked in. Surprisingly I started to hear at around 70hz. I didn't think they would go that low.
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      03-18-2020, 09:42 PM   #20
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My hi-fi mids measure 10dB down with a flat signal, 15dB down at 70Hz with the OEM amp processing, so they go lower than they need to. For the price BMW charges for the hi-fi and H-K amps you'd think the DSP would be a lot better.
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      03-19-2020, 04:55 AM   #21
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Quote:
Originally Posted by damack View Post
After a minor setback and renewed patience, I got back at it yesterday. The speaker issue resolved, although I still don't know why there was a problem.

Wires connected, heat shrinked, ready to go



This is the what I had to do to the underseat enclosures to get them to fit.




All in, the TechnicPnp adapters do make it simple to use the factory wiring, although I had to trim them around the wiring outlet to fit. This is why I think the enclosures may have slightly changed in size.



Connected up the wiring, again the TechnicPnP harness makes simple work of integrating into the factory system without having to cut or splice anything.



All tucked into place



Power supply done.



After a few problems powering up, notably the Audiocontrol GTO feature doesn't work with the factory system. Thanks Encanto above for letting me know. Then the fuse in the main power fuse holder was broken. I tapped the trigger signal into fuse 146 using an add-a-fuse like many others have done. This shuts it down a few seconds after the engine is turned off. I'd like to find a power supply that shuts down the same time as the rest of the audio system so I can listen for a few minutes if I'm waiting in the car without it running.

I need to tune it up but first impressions are pretty good. With the gains turned down I fired up a few songs with a nice bass line and most of the what I was missing before was there. Kick drums give a nice beat that you can feel in the seat. I'll spend some time dialing it in over the next few nights.

While I did have it apart, I did some experimenting with a test tone. With the subs unplugged I ran a tone to see where the mids kicked in. Surprisingly I started to hear at around 70hz. I didn't think they would go that low.
Nice job! So did your wiring connections look like this diagram, except with the addition of using the A connector on the lower left to reuse the stock speaker wiring?

I had installed new speaker wiring directly to AudioControl amp so I didn't use the A connector on the Technicpnp harness.
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      03-19-2020, 09:15 AM   #22
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Yes, that's exactly it John. Once again thanks for your help on this, your information helped make this go pretty smoothly.
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