I was thinking of a simple way to improve the performance of the standard sub system. Add a small subwoofer amp connected to the 15 amp auxiliary for power. Optimally, the amp should have a speaker level input, but if not there are many line level converters that will work. These class D amps with the Texas Instruments TPA3116 chip use very low power draw, yet sound amazing. I have 4 in my home connected to Google Audio Chromecast outputting to high quality speakers and everyone is blown away as to how good they sound. I run them 24/7, for the use less then 2 watts at idle. At minimum the amp would need a sub frequency cut off control. The existing sub is producing too much mid bass (muddy) and almost no low bass. The head unit bass control only adds to the problem by boosting the wrong frequencies. By cutting off the mid bass and amplifying just the low bass should solve the problem. Many just add a subwoofer box with an amp, but that takes up valuable space. I'm looking for the most bang for the buck, not to turn it into a boom car.

The results for those not wanting to read the entire thread, read this summary:

I know some may disagree (likely because they did not actually test it), but the door speakers have surprisingly good, efficient and accurate sound and changing them without adding an amp to power the new speakers will not necessarily improve the sound and may even make it worse, and lots of work too.

For the dash, the simple solution is the same for all cars. Just replace the really bad side dash speakers and attenuate the center speaker. There are lots of quality 3.5” speakers that all will sound worlds better than the factory junk. From the $50 Kickers to the $150 JL Audio. In between is the Infinity, JBL, Hertz, Rockford Fosgate and Kenwood that all make excellent replacements. Just make sure the tweeter doesn’t stick out too much and hit the plastic grill. Also be aware that the existing mounting screws WILL work, but they kind of go in at a slight wonky angle at first until you tighten them up.

Get 2 pairs of Metra 72-8109 speaker wire connector adapters or the lower cost knock-offs from AliExpress. One set for the 2 front dash speakers, and the other for the center dash and sub. Don’t attempt to do the job without these. The wiring connectors supplied by Crutchfield are wrong as is the list of speakers that fit.

Many change the center speaker too, and you think that it would sound better, it generally does not. The “surround sound” that Lexus-Pioneer uses is junk, and the best way is to simply throttle the volume of the center with a simple 2-ohm 5-watt resister in line from the positive wire to the speaker. Use the extra adapter. You can also just disconnect the center. If you insist on replacing it with a match to the side, I would still add the resister in line.

For the sub, it matters if you have a hybrid/Plug-in or all gas. You are basically amping the cars sub signal so the sub box in the back can actually produce sound. Currently it is merely decorative and a marketing myth that the factory system has a subwoofer.

The hybrid has the battery in back, and adding a sub amp is easy using one like the Taramps Bass 400 for about $80. Make sure to use a fuse coming off the battery connection and use the wire gauge recommended by the maker of the amp. Infinity/JBL and others make good amps too, but none compare in value and features. Don’t go overboard on volume and too large an amp, for the factory speaker is unlikely to handle the wattage. Remember you are working towards quality sound and not a boom car. If you want that, you need a bigger/better subwoofer and box engineered for the mechanical properties of the sub. Another option is to buy an all-in-one small sub/amp “underseat” style. They too will add the missing bass at twice the cost. Just make sure the tray openings under the rear deck cover will fit the units. Most are too big to fit. The Kenwood KSC-SW11 is a good choice for the smaller units and sound surprisingly good.

For gas, to avoid running wires all the way to the front, the small $50 Fosi M04 mini subwoofer amp works great. Power the amp through the accessory outlet in the side of the back area with minimum 16ga wire. The inside shell of the outlet slides out and there is a little side cover that you can use to reach up inside. This is the toughest part of the job. You will also need a speaker to line level convertor.

For as little as $125 you can make a major improvement to the sound, fixing the 2 shortcomings, no bass and no higher treble. Good luck on your project and if you have questions, they are likely already answered in this extensive thread.

Disclaimer: If something fails due to any mods you made, like you toast your sub speaker by overpowering it, it is unlikely that Lexus will warranty it. This applies to all modifications regardless of who did it. If this is a problem for you, don’t mess with your car.

 

ML is on the right. As you can see, the box is bigger and likely the sub in the ML system may actually produce bass. If you have the ML system, I suggest to leave it as is. It is difficult to counter the EQ curves built into the factory Pioneer amp when you change any speakers. Just accept it is as good as it gets.

 

I wondered pretty much the same thing you posted, if a better amplifier or speaker combination could be installed in the same location since an external set up takes up too much. Hopefully if you come up with something, please post it. Thanks

 

Already working on it, with connectors that I can return to stock if needed. The hard part was finding the connector going into the subwoofer. Be here in a couple weeks.

Using pink noise and a spectrum analyzer, I did an audio analysis of the full system, sub, front door and dash speakers and discovered why the mediocre quality sound. No real low, and very understated in the treble frequencies that add clarity with no highs to add the sparkle. This is intentional, for the goal with Lexus is you upgrade to the ML system that corrects this.

My initial findings:

To my surprise, I discovered the front door speaker response is quite smooth from the mid bass and tapers off nicely. In the past on most other cars, I used a simple 2nd order network crossover added to the door speakers to tone down the treble spike that makes music clarity and vocals in a sound cancellation battle with the dash speakers, combined with the high IM distortion that happens when a big speaker attempts to produce treble. Add this to the lack of 400hz with the center console hump causing sound cancellation at this wavelength is even harder to fix without an active parametric equalizer. But that was not the case. The HU built in EQ was done very well and no changes are necessary and likely would make it worse.

However, the sub is another story. It produces NO low frequencies at all, and produces a similar mid bass response as the door speakers. Essentially a marketing scam to say the car has a subwoofer, although completely useless. It is a reasonable foam surrounded 8" paper cone, and without knowing the mechanical and electrical properties, I have no way to run a box plot program to know how low it can really go without testing it with a proper subwoofer amp feeding it low bass and no mid bass. I suspect my idea will produce a much better low bass and fill in the needed punch. Not like a dedicated high powered sub, but for less than $75, it should sound worlds better. Worst case is to get a small self contained under seat sub and place it in one of the empty openings or mount it on the right side where there is a space. Or replace the factory speaker with something like a Polk db842dvc with a custom trim ring to support it on the factory enclosure. The little TPA3116 amp driving the sub is awesome and should be sufficient.

Now to the dash speaker. While the factory dash speaker is fair, it is nearly absent of frequencies that give music its depth. I'll try a set of 3-1/2" Kickers. I'll let you know how this $50 fix works out. The issue is the mounting screw centers on the factory 3-1/2" are further apart than all other aftermarket 3-1/2 speakers, so I will make a small plastic (from the top of storage box) plate to mount the speaker to and mount the plate to the car. This doubles as a baffle separation so the box (basically the inside of the dash) does not interfere with the sound the speaker produces. There are lots of good 3-1/2" speakers that range from $30 to upwards of $200, yet more money really gets you better power handling. Since I am not adding an amp to the system (remember that this project is the most bang for the buck), speaker efficiency and smoothness in response is more important.

Hopefully, these 2 simple changes (new dash speakers and a small subwoofer amp) will render amazing results. In other cars, it ended up sounding better than their premium systems. Time will tell.

 

Thanks for the great information and I look forward to hearing your findings on what you did to make the system better.

 

Yep, def looking forward to hearing more!

 

That's great info. I'd love to do something cheap and simple to my system that doesn't mess too much with the factory system to improve it. Firmly in the too hard basket for me though. I've two left hands when it comes to stuff like this.

 

If you're left handed, that gives you a big advantage
Anyway, my goal is plug and play with no destruction of any factory connectors or wiring. Just waiting for all the parts to arrive to test the proof of concept.

 

@AtomicLexus I'm left handed. Not sure it will get me anywhere these days though. Used to be a soundman and your long post above brought back lots of memories. I can't do it anymore with the substantial hearing loss. I spent 20 years in the Air force working on the flight line. Then I moonlighted working Live Reinforcement Sound and Stage Monitor Sound until I retired and went full time. I guess all that sticking my head in the speaker cabinets to see if they were working wasn't such a great idea after all. Now I can't hear a dang thing even with these $5,000 Signia Hearing Aids. I've decided not to spend any money on car stereo any longer. I had the ML in my ES models but really never appreciated it.

But THANKS for the walk down memory lane. I loved reading it and re-living the dream.

 

Proof of function success beyond expectations. A simple change in the front dash speakers yielded a world of clarity and higher frequencies, plus took away all the muddy static crap the factory dash speakers have. Then the simple <$50 amp for the subwoofer brought the depth and punch to the sound system that it was lacking so very much. Unbelievable benefit for less than $100 in parts.

For $300-400 gets you better JL Audio (a bit smoother sound) and a higher power amp like Infinity, JBL or Kicker with a bit more power. I wouldn't go too much on the power for the stock speaker may not handle it and you may need to replace the existing 8" sub speaker with a better low profile 8" sub... or perhaps not. The factory speaker appears well made, but who knows. Also, you will likely need to hard wire it direct to the battery, which is easy for the hybrid, but not so much for the gas models.

 

Do you mind sharing the part number of the subwoofer amplifier you used? Thanks

 

Lots to choose from. I used the Fosi Audio M02 Subwoofer Amplifier, however this has been replaced with the M04, for ~$50 at amazon. You can also get this same amp as a TPA3116 100W Subwoofer Amplifier Board (that you will need to figure out how to mount) for about $12 from ebay.

For the Fosi, you will need the 12v power connector into the amp with a 5.5x2.5 (not 5.5x2.1 as most are) with wire gauge the thickest possible (like 14ga).

You will also need a line level convertor. They run for under $10, often called a K-103A impedance convertor. There are lots of options for these too (kicker makes one, and they all work the same).

The hard part is if you want it non-destructive to the factory wire harnesses, the connector going into the factory subwoofer is nearly unavailable. I got mine from Alliexpress. You need special crimp tool to assemble it.

The other connector is a Metra 72-8109 and available everywhere. This is the same for the dash speakers too.

Also, make sure you drive the amp below clipping. I found that the low level convertor at the default (9am) position and the amp freq and vol settings to 1pm seem to work well. I plan on eventually do a clipping test to see the optimal settings. Remember that clipping, moreso than power, harms speakers. Keep in mind the goal is to add the missing low bass, not turn the car into a boom box. That said, the amount of punch that it does produce is amazing, making music a joy to listen to.

Good luck if you plan to do this. Also, not sure of the effect on the Active Noise Control and Active Sound Control. May make the car sound better with the ASC, but the sound cancellation may or may not work as well for the ANC, or may even work better. Mine is a 250 with neither of these features, although it really needs it.

 

@AtomicLexus

thank you so much for taking the time to write that detailed response. I'm not sure exactly what I'll do yet but I definitely want to use some of your ideas and improve my system. Thanks again.

 

Atomic Lexus,

Thank you for the great information! What dash speakers did you choose? Any pictures of the the mount you made (cutting an adapter from a storage box)?

JI

 

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.