Originally Posted by LeX2K

Almost all music is produced for stereo not for a center channel.

Originally Posted by Brooksguy5

AtomicLexus: Thanks for replying. With regard to adding a resistor to the center speaker, can you clarify exactly how to install a resistor on that speaker? Which wire gets the resistor, and where along the circuit? Do I cut one of the wires in the metra connector, and splice in a resistor? If so, which of the two wires? I am comfortable with soldering and insulating the splice.

With regard to the power cable to the amplified sub, I chose the heavy-duty plug and wires linked earlier in the thread, which includes a fuse. I'll check the fuse and switch to a 10 or 15 amp. I have driven a road trip with two 14 hour days with no apparent overheating (though I admit I didn't check those wires mid-journey) with no apparent problems, but I agree that safety should be paramount.

Thanks again for your replies!

Originally Posted by AtomicLexus

And likely why the resister in line with the center dash speaker has so much improvement.

I have a few questions for the forum that have done these upgrades:
Did the blue tooth phone sound quality improve with a replacement center dash speaker? (I forgot to test that) Phone calls sound worse than any car I have been in.
For someone with the NX350 or 350F (NOT hybrid), did the engine sound improve with the amplified sub when active sound control is enabled? (This feature plays a throaty exhaust sound through the stereo when you drive)
For someone with the NX350 or 350F (NOT hybrid), did the active noise control improve with the amplified sub or no change? (This feature uses noise cancellation for road noise)

Originally Posted by Brooksguy5

To the extent its helpful, here was my auditory journey with my NX 350h. I am very, very grateful to everyone who has contributed to this thread (particularly Atomic, Midcow and Tbartman); my upgrades would not have been attempted without their guidance here. To my 71 year old ears, my upgrades have made a world of difference. I am mostly concerned with sound at highway speeds, as I do a lot of road trips. I find the car to be bit noisy, definitely more so than my previous 2008 RX. But with the upgrades, the sound is much improved and certainly acceptable. At the recommendation of Atomic early in this thread, I replaced all 3 front speakers with the Infinity speakers he suggested. I have found the highs and mids to be quite a bit better. Contrary to what Atomic recommended, I replaced the middle speaker as well with one of the Infinity's. I did not put a resistor on that speaker as he suggested, because doing so was a bit beyond my limited skills. And its a car, right? Not a set of headphones. At highway speeds, I don't expect perfect stereo separation of sound. I was also concerned that the middle speaker seems to be the principal source of sound for the phone system, and the nav system. I need those to be clear, and muting that speaker might be problematic for that reason. If Atomic is still out there and wants to jump in with further guidance on that front, I'd listen to him... All 3 of the Infinity speakers were attached using the original screws into both original screw brackets. It was a bit of a stretch, but by starting them at a slight angle they eventually righted themselves and were securely attached (no zip ties). The overall mids from the existing door speakers seemed to be quite adequate, so I am not currently tempted to mess with those. The lows, however, were quite lacking. I did not want to get into the complexity of amping the existing sub, with all the mods that would be necessary to do so. Instead, I simply added an 8" powered sub (details in a post above), wired into the rear power outlet so it would be switched on/off with the car's power. I figure if I need that outlet for something else, it is easy enough to unplug temporarily. It was difficult to figure out how to disconnect the audio input to the OEM sub, but after a bit of frustration and poking around I figured it out (details in a post above), and was able to use a spare metra connector to connect to the high level audio output that originally went to the OEM sub. This 8" sub, tucked behind the wheel well in the cargo compartment but above the cargo floor, has proven to be more than adequate to put out great low end. I am very happy with the overall results, and am also happy that I can easily put this part of the upgraded system back to stock if necessary by simply switching connectors and reconnecting the OEM sub, which remains in place but dormant. I hope that this helps others who might want to go down this road.

Originally Posted by AtomicLexus

Since you have not started the subwoofer project yet, for the same money as the amp you selected, you could get a self contained under-seat style subwoofer and not risk damage to the factory sub by over-powering it with that amp. Sound quality would be similar. Read through the threads. Many have done this, and very easy for the hybrid.

Originally Posted by LeX2K

Stock speaker is 83dB?

Originally Posted by AtomicLexus

Just connect it to the speaker level inputs. Be aware that this amp has a bit of power, 175 watts at 4 ohms. It may be easy to blow the factory subwoofer if you drive it too hard. I doubt Lexus will warranty it if that happens. Also, I assume you are using it with a hybrid and connect it to the battery with a 30a fuse in between. Enjoy.

Originally Posted by fierymonkey

I change my plan I've order jl audio 8W3v3-4 think it might be a better option. And a custom box so no need to worry of burn the stock woofer and storage.

Originally Posted by AtomicLexus

I used a set of Kicker 46CSC354 speakers I had in my old Prius. They are a little bright but have a nice quality tone. Similar (and perhaps a little better) would be the Infinity Reference REF-3032cfx or the very similar JBL Club 322F. A step up in sound smoothness without the exaggerated highs of the others is the JL Audio C2-350x at almost 3x the price. All of these are excellent speakers and should make a major improvement in clarity and higher frequencies over the garbage that Lexus puts in. When you fix the highs and clarity, it does make the missing low bass more noticeable. Improving sound is a rabbit hole of sorts. I was after the most bang for the buck. I explored other speakers, but few can live up to the quality and clarity of the ones I list.

As for the mount, I went to great lengths to create a pattern and cut out an adapter. Just to test my idea, on the other speaker, I just mounted it with the factory clips. There was little difference between the two, and in hindsight clearly not worth the extra effort. I have built many speaker systems, and the box size, port, sealed or transmission line are more critical in low frequencies. Since these little 3-1/2" drivers can't make the low bass anyway, I would not bother.

Don't forget the Metra 72-8109 wire adapters for simple plug and play.

Originally Posted by AtomicLexus

Do I cut one of the wires in the metra connector, and splice in a resistor? YES, THIS WAY YOU LEAVE ALL THE FACTORY WIRES INTACT. WRAP IN ELECTRICAL TAPE AFTERWARDS.
If so, which of the two wires? BEST TO USE THE POSITIVE LEAD THAT IS EASILY IDENTIFIED AS THE LARGER OF THE 2 SPADE CONNECTORS GOING TO THE SPEAKER TERMINALS. IT MAY HAVE A RED DOT ON THE SPEAKER TOO.
I'll check the fuse and switch to a 10 or 15 amp. SWITCH TO A 10amp FUSE AND LIKELY IT WILL WORK FINE AND GIVE A GREATER LEVEL OF PROTECTION.

Originally Posted by AtomicLexus

That driver can produce some series bass, and building your own box is a great project. To get optimal results, you can follow their recommendations of box size (10 liter interior) and port (2" ID x 18" long) or use a box plot program to design the best results based on your speaker that lets you experiment with port sizes for the fixed box size that can fit back there for proper tuning. I have designed many speaker enclosures, from sealed box, ported box, transmission lines and multi-chamber designs. A big mistake people do is simply put a sub in a box and amp it. Most of the time, this renders a big bump at one frequency that makes the single note pounding thump sub with no musicality. The box plot programs can tailer the desired results before you start. If you want, give me the internal measurements for the box you are building and I can check it and perhaps recommended a port size (or not) with an expected frequency curve graph. I suspect that this subwoofer might not work for it may be too deep for the area in the back with a sufficient thickness box structure that minimizes stray resonances. Note that JL Audio makes some nice thin and small box subs too. Also, there are many other makers of excellent subs for less than $100. Unless you are after some really strong bass, you pay a lot more for very little improvement in sound. The rabbit hole of audio goes deep.