[PJ Gross]

I'm a new 2015 335xi GT owner. I am new to BMWs, but not new to car audio and/or cars. I am pretty impressed with the HK system my car has, but my listening preference is mostly SQ with ability to turn up the bass for certain moods, songs, situations.

I've read a ton of posts in the last month, and would appreciate some input/ pointing to the correct direction, of what I would like to accomplish.

I "think" the HK system is pretty fantastic! It satisfies about 75% of my audio wishes. So I started looking at options.

My first desire would be a clean fitting 10-12" single sub, sealed, fairly high excursion with enough power to remotely turn up sound pressure but just fill out daily listening duties.

I have an email in to Integral to ask whether their sub would fit an F34, but I have a hard time forking over that kind of dough for a compromise that I doubt will do what I want at 250W nominal power. (from their ARC amp in the overall system they sell)

With the HK system, if you were going to add a sub, how would you choose to integrate it?

I would be ok with something as basic as a LOC, then AMP, and custom enclosure. I would get this through someone like Technic on the forum?

One post of a similar solution to note was:
https://f30.bimmerpost.com/forums/sh....php?t=1408166

Remote turn on source is still (I think) a sticking point for the HK system. Lots of input on there, but in one post I think someone found a fuse that could do an "add-a-fuse" to, I would have to re-look up.

Anyway, I still don't know the specs of the HK underseat subs / amp channels. If I could feed more power to them safely, I would just get a 3 channel amp and re-power the underseats and the add on sub at the same time.

I've been pretty happy with their performance, actually. I just miss "feeling" my DMB jam sessions.

Thanks for listening and any link pointing to a thread that might help I would appreciate.

Since there are 3 stock systems that are incorporated in different ways, I was hoping to clarify what/how to handle the HK system.

Thanks,

-PJ G.

[PJ Gross]

Thank you for moving, I saw my mistake after the fact that there was a sub-forum. I also see that I will likely be nicely told to search more. Well, I had thought I searched quite a bit. What I've seen is that through the 3 audio systems, the HK system might have some unique connection considerations. That's why I was asking "how would you integrate a sub" in the HK system? If I read correctly, the underseat HK subs are around 7ohm, so higher impedance and therefore require more power to drive to similar sound pressure levels than the base or hifi woofers.

Thank you for any links that I could reference,
PJ

[Billfitz]

The under seat enclosures are too small to support going significantly lower or louder, no matter what you have for drivers or amps. A rear mounted separately powered sub is the only way to go. The BMW systems have proprietary connections, so a specially made harness is required to tap the amp input to feed a separate sub. I know there are multiple threads on that subject. Finding sub amps that have remote turn on and remote volume control is a matter of doing some searching.

[1QuikWS6]

As stated, best bang for the buck is installing an actual subwoofer in custom enclosure, with it's own dedicated amp & LOC, using the Technic Harness specifically for this install in HK system

There are 2 stages in my mind:

Stg1

• 10" Subwoofer
• Custom Trunk Enclosure
• 1 Ch (Mono) Amp
• Technic harness
• LOC

This will install sub ONLY...

Stg2

• 10" Subwoofer
• Custom Trunk Enclosure
• 3CH Amp (1 Ch for Sub, the other 2 for underseat speakers)
• Technic Harness
• LOC
• New higher quality Underseat Speakers

The Technic Harness can handle either stage.

Previously he would sell the Audio Control LC2i LOC, but he has a new product that is better = PnP 40V LOC

I have the HK (Top HiFi option 688) in my F32. Personally for my sub duties, I went with the Stg2 which included:

• JL Audio 10W3v3 Sub
• Musicar Trunk Enclosure
• JL Audio XD500/3v2 amp
• Technic Harness (Logic7/HK/EPS/Individual Audio/Bang & Olufsen/Bowers & Wilkins add-a-sub harness w/LOC-X)
• BavSound Ghost Underseat Speakers

Here is link to Technic Harness:

https://technicpnp.com/product/logic...harness-wlocx/

And link to thread detailing a similar install (wiring will be slightly different as the new PnP 40V LOC is easier to wire, but different):

https://f80.bimmerpost.com/forums/sh....php?t=1170130

[enjoythemusic]

Interesting, as am also into sq and the HK system in the 435i was a semi-disaster. Changed front doors to Focal separates and added powered sub. In my car, the center channel was a phase/time mess so i unhooked it. Turn on lead is easy, I'm the guy who posted the fuse you can use.

All really depends on how high a budget you have and the talent of the installer.

Under seat woofers are not true subs imho. Dont bother with them much, as others said the sq/ft of enclosure is too limiting. Did some VERY aggressive eq'ing using the Onkyo android app and the under seat woofers have potential, but they'll never 'bump hard' due to a lack of ability to move the appropriate amount of air cleanly.

[PJ Gross]

Originally Posted by enjoythemusic

Interesting, as am also into sq and the HK system in the 435i was a semi-disaster. Changed front doors to Focal separates and added powered sub. In my car, the center channel was a phase/time mess so i unhooked it. Turn on lead is easy, I'm the guy who posted the fuse you can use.

All really depends on how high a budget you have and the talent of the installer.

Under seat woofers are not true subs imho. Dont bother with them much, as others said the sq/ft of enclosure is too limiting. Did some VERY aggressive eq'ing using the Onkyo android app and the under seat woofers have potential, but they'll never 'bump hard' due to a lack of ability to move the appropriate amount of air cleanly.

Thanks guys.
I have no intentions of using the underseats for anything meaningful under 80 hz. I wanted to know if the HK underseats were adequate for higher power and if so how much.
The amp I am eying is the JL hd600/4 and bridge for a mild sub with the other two channels powering the under seats. I have a css pdx-10 in a sealed box left from my CTs-v that would be happy in the boot of the f34 I think.

With the 3 levels of factory radio I just didn't know if it was worth changing the hk mid bass out or just seeing how they do with more power.

[enjoythemusic]

More power helps the under seat, but like you said 80Hz is about where they are really. As you know you need less power to drive an 8" speaker to 80Hz (and even less for a 1kHz signal for a midrange driver) than you do a 40Hz signal for a 12" JL Audio to reach the same SPL (overly generalized, yet generally holds true).

If you reeeeally are serious, it'll take thousands of dollars and multi-channel amp, electronic/DSP crossover for tuning and ensuring phase and time are accurate at the preferred listening position (basically).

[Billfitz]

Originally Posted by PJ Gross

Thanks guys.
I have no intentions of using the underseats for anything meaningful under 80 hz. I wanted to know if the HK underseats were adequate for higher power and if so how much.

They'll take maybe 75w at 80Hz before running out of excursion. Any more than that will have no benefit. I haven't seen any replacement woofers that list excursion capable of taking more than 100 watts. The main advantage to higher power amplification would be lower amplifier sourced distortion, and that would be in the mids and highs, not the lows.

[335JTSD]

I want to go same route and plan on adding a 10w6v3 I already have to my 435i GC. I was told by a local shop I need a drain limiting circuit installed to the tune of $400, not including installation of an Audio Control LC1.800 and bass control knob. Is this necessary? I guess they add a high current relay with a timer that disconnects the aftermarket equipment shortly after the engine is turned off. Labor alone is over 1K. Seems high but they seem to be the best shop in San Diego. So not sure what to do. The other shops seemed to have no clue on what it takes to integrate with the HK 688. I'm afraid of them hacking it together or messing it up.

[Billfitz]

The installation of the LC1.800 appears as easy as it possibly could be, so IMO the price quoted is off the wall. A drain limiting circuit is unnecessary. I doubt even a relay is really required, but you'd have to see what open fuse locations are available in the trunk fuse box to be sure. Integration should be very easy with a Technic harness. I can't imagine you'd have a problem doing it yourself with help from an auto sound forum. They don't just discuss ricers.

[335JTSD]

I thought so too after trying to read through these forums and never seeing a drain limiting circuit mentioned. I'll try to read some more forums and decide if I want to tackle myself. Thank you for your help.

[dss0110]

Hi,

Does anyone have a link or write up on how to amplify the HK underseat subs. Currently have a JL 12 inch sub powered by a JL 500/1 amp without the Technic harness. So was just wondering how I’d go about amplifying the underseats without a harness.

Any help or advice would be highly appreciated.

[Billfitz]

Originally Posted by dss0110

Any help or advice would be highly appreciated.

Don't double post. Do search. You can find things like this: https://f30.bimmerpost.com/forums/sh....php?t=1730058

[dss0110]

Originally Posted by Billfitz

Don't double post. Do search. You can find things like this: https://f30.bimmerpost.com/forums/sh....php?t=1730058

Thanks.

Any recommendations on an amplifier to power the underseats? I've been through many threads and understand the HK subs are 7ohm units. So what would be the best wattage at 4ohm to power those as there aren't many amps out there that show 8ohm outputs on their specs.

[NealfromNZ]

Originally Posted by dss0110

Thanks.

Any recommendations on an amplifier to power the underseats? I've been through many threads and understand the HK subs are 7ohm units. So what would be the best wattage at 4ohm to power those as there aren't many amps out there that show 8ohm outputs on their specs.

Half the 4 ohm power for 8 ohm rating

So an amplifier that’s rated 200 watts @ 4ohms becomes 100 w at 8 ohms.

Factory HK is rated to 125 into 8 ohms so your going to need 300 from an aftermarket to get to 150.

[dss0110]

Originally Posted by NealfromNZ

Half the 4 ohm power for 8 ohm rating

So an amplifier that’s rated 200 watts @ 4ohms becomes 100 w at 8 ohms.

Factory HK is rated to 125 into 8 ohms so your going to need 300 from an aftermarket to get to 150.

Ohhhh I get it. Thanks for all your help