Customer complaints about the apparent lack of deep bass in his 435i HK system. No matter how the 7-band EQ and Bass adjustments are set, the elusive deep bass that he is looking for is just not there.
Well, without a trunk sub it will never be.
So the idea is to add the trunk sub and provide an adjustable power upgrade to the 7ohm OEM mid-bass woofers to keep up with the new sub bass. And first of all, this upgrade must be price-effective.
Thus a JL Audio 10W0v3 BassWedge Ported built-in box/sub was selected by the customer. And then an XD500/5v2 as the 3-channel amplifier -stereo for the OEM woofers and mono for the sub. An Audiocontrol LC2i active line output converter is selected to interface between the OEM amp and the XD500/3v2 using a Technic PnP HK harness -100% PnP, 100% reversible back to stock as this is a lease.
The LC2i active LOC is used in the HK OEM system in particular due to the 30V+ peaks of the OEM amp woofer outputs. No remote turn on is possible with the OEM amp as all its outputs are Class D -
no existing signal sensing circuits can trigger with those Class D output signals. The LC2i can handle up to 40V peaks.
Now the install...
HK OEM amp (12V accessory jack connectors can be seen on the trunk right trim panel):
Technic PnP HK harness to be plugged in between the OEM amp and the OEM amp harness in the car (no messing around with OEM amp power or MOST connector):
The Technic PnP harness for the HK allows the install of a trunk sub, extra power to the underseat woofers or both installs, no need to cut any wires:
Custom LC2i/XD500/3 mounting rack in a slanted design to clear trunk floor when closed -completely removable:
Direct battery and ground connections:
Custom cables connected to the LOC and woofer connectors at the Technic PnP HK harness (remote signal not shown):
Trunk sub Molex quick-disconnect:
Trunk sub installed:
Notes:
1. Midbass and sub bass everywhere. In any song. Even Cha-cha-cha.
2. Woofers and sub were tuned with the iDrive Bass adjustment in the center. The purpose is to use the Bass adjustment as a bass "knob" for both the OEM woofers and trunk sub, while the 100Hz 7-band EQ slider is the trunk sub level adjustment. Trunk sub was set to 100Hz low pass, OEM woofers were set at 80Hz high pass for some overlapping. Gains were set minimum for the sub (anything more and it was overwhelming), and 9 o'clock for the OEM woofers.
The LC2i was set to output via the Main port (no need for the Accubass feature of the Bass port). The remote turn on was set to turn on only the LC2i and then the XD500/3 to turn on via signal sensing from the LC2i. The purpose of this arrangement is simple: the OEM 12V accessory port at the trunk turns on when any door/trunk is opened, exactly like the OEM amp. However, it turns off in about 13 minutes or so. That is too long for the XD500/3 to be on -it will draw too much current from the battery.
The solution was to keep only the LC2i on/off via the 12V accessory port line and make the XD500/3v2 to turn on/off
only when the iDrive is on/off. The XD500/3v2 receives its inputs only when the iDrive outputs a signal via the LC2i. No signal, no XD500/3v2 turn on. The LC2i current draw is tens of times
less than the XD500/3v2 thus battery load would be insignificant for just 13 minutes. No need to tap or run a wire from the iDrive OEM remote turn on signal to the trunk either.
The 12V accessory port wiring is just above the OEM amp. A custom blade connector interface was created for the OEM 12v accessory jack -no wires tapped, 100% PnP, 100% reversible back to stock.
The XD500/3v2 is set to use only 2 RCA inputs to generate 3 channel outputs.
3. Although the OEM woofers are 7 ohms and the XD500/3v2 is rated at 75W RMS/150W max at 4 ohms, they sound way louder with the technically less than 150W than the OEM amp supposedly 125W at 7 ohms. I mean, they were so loud and deep with this XD amp that I suggested to the customer to return the sub if he liked what he was hearing/feeling.
He politely refused. He wanted more of that.
Once you go Bass you cannot go back.
4. The Basswedge trunk sub is something else for its price. Yes, it takes quite a lot of trunk real state, it is not an elegant solution, it is bulky. But it solves all sub bass problems. All of them. Deep, loud, tight bass. Perfect complement to the OEM woofers new midbass impact.
Customer was happy. Very happy.
