So like I promised, here's how to get the factory sub and all 4 doors speaker to work with an aftermarket HU

This is the wiring I did, I used a 6 pin harness for everything but the speakers wires for easy servicing, for the speakers I used an RCA cable that I've cut in half and soldered to the 8 wires (make sure you respect polarity) on the B plug

Battery 12v (B+ Cyan_Blue/Yellow on C1)
Accessory (ACC grey on C6)
Ground (GND2 brown on C14)
Power Antenna (ANT+ Black/Red on C12)
Amp remote (AMP+ Pink/Cyan on B11)
FL Speaker (+) BLACK (B2) to RCA
FL Speaker (-) WHITE (B7) to RCA
FR Speaker (+) WHITE (B1) to RCA
FR Speaker (-) RED (B6) to RCA
RL Speaker (+) RED (B5) to RCA
RL Speaker (-) GREEN (B14) to RCA
RR Speaker (+) YELLOW (B4) to RCA
RR Speaker (-) GREEN (B13) to RCA



Wait... where's the sub signal??? There's none, everything is happening at the amp.

The amp is using the signal from FL,FR,RL,RR and feed the sub with it, but the way it work is that it high pass the signal for the doors (~100Hz) and low pass the signal for the sub.

When I started the system after replacing the HU in mine, I didn't have any sub. Went into my deck settings and removed the HPF (High pass filter) that was set at 120Hz. Bam! I can hear the sub, go into my EQ and boost 60Hz and the car is shaking.

Basically all the bass **** on the deck was doing is to boost or lower the lower frequency and only the sub is affected because of the LPF and HPF that is set in the amp.

Now for those who want more punch out of their system, you need to bypass the the nak amp before replacing speakers in your doors. Since there's an HPF set in the Nak amp, even if you put 8" in your doors you wont get much more midbass out of them.

If you already did this and you can't hear your sub, here's some things to check. First make sure your RCA output are set to fullrange (no HPF) in your headunit. Some HU will automatically set an HPF if the sub is enable so check that too.

Next, check that you respected the polarity on all RCA, if you have one inverted it will cancel out (phase inverted) the sub since all channels go to one speaker. To see if that's your problem, simply set the balance to one side and do the same for the fader so that only one speaker play. Crank the lowest EQ settings you have (ideally 80Hz or less) and you should hear the sub.

HTH

 

So how did you go about getting the signal from your head unit to the amplifier?

 

updated my first post

 

Finally someone shows how to integrate the Nak sub. Can someone else try this and report back to confirm it's working.

 

Too bad the pioneer systems are considerably different :<

 

I would have thought that most Nak equipped LS400 owner would have been all over this...

Swapped my Alpine IVA-w205 for a INA-w910 (extra tuning capabilities) and the factory system with the rear speaker off is not bad at all.

Stage height is at the dash, width is from left a-pillar to passenger side mirror and center focus is between 8 to 15inch depending on frequency.

Sub well it's a one note wonder lol, it have very narrow bandwidth (45-80Hz) but this is where most bass is in music so it's not so bad. The amp auto level the sub to prevent clipping at high level, this I hate since you need to crank the low EQ to get some decent output at high level, but when you lower the volume all you can hear is the sub... Full SQ install this spring will finally begin.

 

Well it came too late for me. I bought a 5 channel amp (Rockford Fosgate) and I have no problem with it. I would have loved to save that $200 though.

 

good job here!

i share the same sentiment . i am still determined to find a solution for non-Nak cars.

 

When I replace my HU I plan to use a small dedicated sub amp+sub anyways so I'm not overly bothered.

 

I am surprising my wife by changing out the OEM Nakamichi Hu with a Kenwood so she can have bluetooth and stream hercoandora. Her 1998 LS400 has 261,000 miles on it. I am very happy to have found your post. I plan on having it professionally installed so there are no issues. Thanks a bunch.

 

I can confirm, Lexmoose instructions works for the Nakamichi system. I installed Sony XAV-712HD yesterday, everything works except for the rear left speaker. My car (98) came with Lexus Telephone. The left rear speaker is connected to telephone transceiver. Their is a small speaker relay in my trunk connect to a brick. Nakamichi wiring shows black and yellow wires from the speaker goes to the relay then comes out and goes to the amp. I don't see black and yellow wires in the trunk. Does anybody knows how to make my left rear speaker works?

 

Maybe it's not BLK and YEL at the box

See the diagram that show different color wires

 

Unplug all the connectors from the phone ECU in the trunk. Plug the two large connectors on the "car side" together. There is a white plastic bracket on the bottom of the tool box receptacle that you can plug these two large connectors "through" to keep them up and away from moisture. All the connectors on the car side should be tucked upward so that they don't get wet and corroded. If any of the pins on the two large car side connectors look corroded, you may need to clean them. If the handset in the center console is still there, you might as well unplug it from the connector(s) under the vents you see when the armrest is raised. The handset cradle can be removed by prying out the upper console tray insert with a putty knife or trim removal tool - be careful and work your way around the edges when prying it out as the upper console tray insert is easy to break and not available as a separate replacement part.

 

I disconnected the phone ECU and connected the two wires together. I can now see the black and yellow cables. They are thicker compare to other. Speaker still don't work. No corrosion on the connector. Will it be okay to cut the black and yellow wires and connect them together without using the white connector?
What are the rest of those cables do or go to?

I took out the phone cradle long time ago.
Lexmoose - the wires you circled got me confused because the pin numbers and colors from the schematics don't match the connect going to the speaker relay.

 

I have never encountered a case where factory installed connectors had to be chopped off and bypassed to get speakers to work. Are you certain that you have a good connection for the left rear door speaker where you connected your new head unit?

When there is a phone ECU problem in the trunk, all the speakers are muted - not just one door speaker.

After you have disconnected and removed the phone ECU in the trunk, you will be left with the connectors shown in the attached photos. The small white one will not plug into anything. The two mini UHF cables are for the phone antenna imprinted on the rear window. Ignore the black coax cable in the photo k- it's for an aftermarket phone system I installed.