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[QUOTE=AtomicLexus;11586983]Did you happen to get any photos of the factory box taken apart and the back side of the factory sub?
Here are pics. Note: in addition to installing ring a corner inside the box had to be melted too (x in pic) to accommodate the larger magnet: Audison: 120mm (4.72"), max. location 90mm (3.54"), OEM speaker 50mm ( 1.97") magnet diameter...
Inside back of OEM box OEM speaker (fs 43Hz, ~70W, 2.5 ohms) with fitting screw
Here are pics. Note: in addition to installing ring a corner inside the box had to be melted too (x in pic) to accommodate the larger magnet: Audison: 120mm (4.72"), max. location 90mm (3.54"), OEM speaker 50mm ( 1.97") magnet diameter...
Would the 2-3/4" deep Kenwood or Kicker magnet clear the area you needed to melt away? It is pretty clever having the speaker help strengthen the box with the mount behind the magnet. Also, using the smaller neodymium speaker magnet really makes a drop in replacement difficult. It's just like the non-standard mounting bolt centers for the dash speakers. The goal is to stop easy upgrades.
I couldn't find magnet size data from Kenwood, but it is certain that it only fits if factory box by melted. Did you see how low its sensitivity is? (78 dB...) The Kicker is more sensitive, but the magnet cover is even bigger and the cut-out diameter is quite small (6 15/16"). If you definitely don't want Audison, check out the Focal 20 FSE: https://www.focal.com/sites/www.foca...eet_p20fse.pdf
I have no information about the specific SLK Hertz sub. The factory is the same as Audison's their products have a pretty good reputation, but... if you work with it so much, why don't you add an ideal new one?...
Did you see how low its sensitivity is? (78 dB...) The Kicker is more sensitive, but the magnet cover is even bigger
Take the sensitivity ratings of subwoofers with a grain of salt since there is no standard on frequency used, moreover the 300-3000 normal reference is already out of the efficiency range of a sub whos goal is <150hz.
That testing shows the opposite. Get rid of the outliers and tested vs claimed is close what we see is slightly exaggerated specs from most every manufacturer.
That testing shows the opposite. Get rid of the outliers and tested vs claimed is close what we see is slightly exaggerated specs from most every manufacturer.
The test I linked was just an example of the inaccuracies for sensitivity ratings, and for subwoofers this is on scale a much more complex problem for there are no standards that are based on the subwoofer audio range to make good comparisons. Hence the reason I said to take the low rating sensitivity spec of the Kenwoods with a grain of salt. I'm not pushing for or against any brand, only looking for a sub that will fit sans major mods, that many readers can benefit from. It is great when contributors like tdlnfm and many others go above and beyond to test the limits and share their knowledge so we don't need to reinvent the wheel.
The other problem with subwoofers and sensitivity is that box size, port tuning and multi-chamber designs all drastically effect sound output. If your goal is to have a high SPL ratings, it is easy with many of the boxplot programs to design a box that accomplishes this single note result. When you design a box that results in a much smoother slope, you sometimes lose 6db or more. That is half the sound output, but the end result is more musicality. It just depends on your goal on how you manipulate the box. In our case, the box is fixed, and moreover the box properties are a bit convoluted. So any fine tuning is simply the crossover slope on the amp.
Take the sensitivity ratings of subwoofers with a grain of salt since there is no standard on frequency used, moreover the 300-3000 normal reference is already out of the efficiency range of a sub whos goal is <150hz.
For the Lexus, my goal is find a drop in replacement to recommend, yet your findings show the animal does not exist.
The measurement of speaker sensitivity is standardized: SPL = 1W/m at 1 kHz, but you are right that this data is less suitable for qualifying subwoofers. I am sure that the Kicker is louder than the Kenwood, which is also suggested by its bigger magnet. Low resonance and high efficiency can only be achieved with a large magnet.
Unfortunately, the magnet capacity of the Lexus OEM box is quite limited, but every speaker is a compromise.Comparison: I didn't have Audison before, but this 8" sub + Hifonics sounds very convincing, car shakes, the ML sub I heard in the salon doesn't hit that hard. In my business car a 300W R/F amplifier beats a P2D210 subwoofer, which is a bit more dynamic, but doesn't go down as deep and isn't so articulated. I admit, I sneak into the garage in the evenings to listen to music... I'll drain the battery one day...
Tonight (without listening...) I measured the response of front door speakers, will upload the diagram tomorrow. As you wrote before Atomic, they are very linear.
The measurement of speaker sensitivity is standardized: SPL = 1W/m at 1 kHz, but you are right that this data is less suitable for qualifying subwoofers. I am sure that the Kicker is louder than the Kenwood, which is also suggested by its bigger magnet. Low resonance and high efficiency can only be achieved with a large magnet.
Unfortunately, efficiency is much more complex than magnet size and Fs. Also, in general, lower efficiency speakers when amplified sufficiently tend to produce the best sound; they have lower IM distortion and smoother response with less drastic peaks and valleys. Obviously at a cost of higher power needs. Ultra high end speakers are generally low efficiency and most driven best with class A amps. Class A amp's always running power transformers' wastefulness is impractical for a car. The high quality of the latest generation of economical class D amps even makes class A amps nearly unnecessary, even for high end home systems (I know this will ruffle the feathers of some audiophiles, but an A-B blind listening room test may surprise you).
For those wanting to design woofer and subwoofer enclosures there are many excellent free software programs that once you have the drivers mechanical and electrical properties are easy to plug in what-if scenarios to graphically see the expected response curve before you start your build. You will no longer rely on the cu/ft sealed box recommendations that many manufactures give as a starting place. Some of the programs will help design multi-chamber boxes (think Bose) or transmission line enclosures. These passive designs were far more critical in the old days when few systems had dedicated subwoofer amps, but it is fun to play with nonetheless.
Unfortunately, efficiency is much more complex than magnet size and Fs. Also, in general, lower efficiency speakers when amplified sufficiently tend to produce the best sound; they have lower IM distortion and smoother response with less drastic peaks and valleys. Obviously at a cost of higher power needs. Ultra high end speakers are generally low efficiency and most driven best with class A amps. Class A amp's always running power transformers' wastefulness is impractical for a car. The high quality of the latest generation of economical class D amps even makes class A amps nearly unnecessary, even for high end home systems (I know this will ruffle the feathers of some audiophiles, but an A-B blind listening room test may surprise you).
For those wanting to design woofer and subwoofer enclosures there are many excellent free software programs that once you have the drivers mechanical and electrical properties are easy to plug in what-if scenarios to graphically see the expected response curve before you start your build. You will no longer rely on the cu/ft sealed box recommendations that many manufactures give as a starting place. Some of the programs will help design multi-chamber boxes (think Bose) or transmission line enclosures. These passive designs were far more critical in the old days when few systems had dedicated subwoofer amps, but it is fun to play with nonetheless.
Dear Atomic, let's not forget that this is a Lexus and not an audiophile forum, I deliberately did not want to take it in that direction. Actually, this profound question should have started with the analysis of the Thiele-Small parameters. So, I think we should stay on the ground. If you want to replace the factory subwoofer, you can only choose from a few types, because the others simply won't fit. After I disassembled the box surely know of 2 types that can be considered at all, Audison APS8 (D and R) and Focal 20 FSE, if anyone else has a different experience, please share.
I promised the diagram of the 7" door speaker, attached. You can see that it stays within +/- 3 dB in the 60-250 Hz range. (The dashboard speakers work above it, and the sub works below it.) I think replacing it is unjustified, although the ML version has a 6X9" here, which goes even deeper helping the sub.
What did you use to reshape the sub box inner protrusion to clear the magnet cage? It sounds like only the shallower subs will work, and box mods will still be required. What is the maximum depth that will fit? 3" or ?
Anyone have any comments if the added sub improved the active noise control (road noise cancellation) and active sound control (artificial engine sounding like uncorked headers). I would think both of these features would get better with a subwoofer improvement, but they are on the 350 and 350 F-Sport, and I have the 250 without either of these cool features.
What did you use to reshape the sub box inner protrusion to clear the magnet cage? It sounds like only the shallower subs will work, and box mods will still be required. What is the maximum depth that will fit? 3" or ?
As I wrote before, the maximum depth of the speaker (without ring) is 3".
Subwoofer replacement experiences (Audison APS8D + Hifonics Pluto I):I've been listening to the system for two weeks now and I find it amazing. When listening in the garage (gas engine off), the bass is a bit too much, but just enough on the highway, where the real bass starts at a volume of 50. The factory amplifier (supply unloaded by turning off the bass output) seems to shake the 7" door speakers more, the door vibrates more than before. The transiens are very good the system hits hard, does not flow (Qtc=0,66). Test music
at 2:21" max volume the bass clicks in my brain. If this is not enough for someone a bigger box required. To factory space could also be made of MDF/resin composite, which would fit a 10" (possibly 12") flat subwoofer. However this is a very large and complicated job (due to the precise bodywork connections) which is probably not proportional to the improvement and even stronger body resonance should be expected.
I finally heard (felt?) my subwoofer for the first time today. Up until this point if you would have told me that Pioneer box in the back of my NX was a fake decoy, I would have believed it. Finally got around to installing one of those baby amps that AtomicLexus suggested in between the stock system and stock sub. Very happy with the results. Any Dune fans out there, I can now call the worms... Thump, thump, thump, thump...
The road departing mediocreville was a bit bumpy though. First, I wanted no visible wires or tampering with existing factory wires, so I ordered some connectors compatible with the 12V socket in the trunk from AliExpress to power the amp. I goofed and accidentally ordered 2 male connectors instead of a male and female, so had to reorder. That took some time. If anyone is interested, these connectors work for building a custom harness for tapping power from the rear of the 12V socket without messing with the factory wires.
Next issue, I had a little bit of prior experience with these tiny amps, I had used a Fosi on my home theatre when I had to replace my receiver and forgot that the original one had a powered sub output and the new one didn't, so the Fosi was added to restore function. But for the NX just for fun I decided to buy one of those similar generic amp boards without a case that was much cheaper. I even designed and 3D printed a new case for it with custom NX logos and stuff. Only problem, that cheap pretender sucked terrribly, so back to using a Fosi amp.
@AtomicLexus Thanks for the original suggestions you made, excellent ideas to improve the stock system super inexpensively.
AtomicLexus,
thanks for the great advice on the front speaker replacement, the resistor added to center channel and the subwoofer amp addition. Regarding the stock subwoofer, is there any benefit to putting in some Dynamat behind the sub or anything else to modify to improve the stock sub performance?
Thanks
Last edited by Lexicon1; 10-29-23 at 12:23 PM.
Reason: typo
10-01-23, 01:24 PM
