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Take out the screws, pull out the connector, stick it in the garage and get back the boot space.
 
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@1soupdragon1 Thanks for your comment, but the laws of physics cannot be changed, no matter how many ports or foldback twists and turns they put into a tiny box. What it all boils down to is the ability to move a body of air. They knew this instinctively in the 1500's when they first started building pipe organs with massive 64' wooden pipes. If you get the chance visit Winchester or Salisbury cathedrals when they have a practice or a concert and you will see what I mean. You feel the lower frequencies, not just hear them.
I'd be surprised if the Bose sub in the Tekna will ever get to 50hz, I suspect it will be nearer to 150hz with maybe a few harmonics below that.
It does have it's own little amplifier in the box btw.
Tony.
Yeah, when I first saw this Bose box in the boot, back in 2017, of a loaner I was not even that sure what it was... an amp? Surely not a speaker? Anyway, it just got in the way of my stuff! Lol

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Saying that, Bose like to feck about with weird stuff like wave guide blahdy blah...trying to get bass out of sound docks and that type of thing. I definitely think it reaches lower than a standard 4 inch driver, although how deep is anyone's guess - 50hz area perhaps
Doing a quick sine wave sweep by ear from an app on my phone, mine (with the adjustments I mentioned earlier) is flat down to about 35Hz and still has useful output to about 30Hz, falling off rapidly below that.
 

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@1soupdragon1 Thanks for your comment, but the laws of physics cannot be changed, no matter how many ports or foldback twists and turns they put into a tiny box. What it all boils down to is the ability to move a body of air. They knew this instinctively in the 1500's when they first started building pipe organs with massive 64' wooden pipes. If you get the chance visit Winchester or Salisbury cathedrals when they have a practice or a concert and you will see what I mean. You feel the lower frequencies, not just hear them.
All true to a large degree but you're forgetting one critical point - a car is not the same acoustic environment as a living room or outdoors. You don't need nearly as much driver volume displacement for the bass in a car to reach the same SPL at the listeners ears due to it being such a small, enclosed environment many times smaller than even a small British living room. In a sense you're actually sitting inside the speaker cabinet when you're sitting inside a car.

Furthermore because it's such a small, more or less pressurised environment you get 12dB/oct "room gain" below a certain corner frequency which depends on the volume of air in the car. In a typical car the size of a Leaf that turnover frequency is approximately 50-60Hz, that means in theory if you build a closed box woofer system with a natural roll off of 12dB/oct that starts at around 50-60Hz, the "room gain" of the small car environment counteracts the natural closed box roll off resulting in a near flat response to stupidly low frequencies, or in practice well below 30Hz due to the car being imperfectly sealed.

This is exactly the same principle that allows miniature in-ear ear buds to go down to stupidly low frequencies of around 25Hz or even lower with ease. If you test them you'll find the resonant frequency of the driver is well into the lower midrange with a free space roll off of 12dB/oct below that, but this matches the "room gain" of the tiny ear canal resulting in a perceived flat response down to very low frequencies.

This is why car subwoofers are often closed boxes not ported - they better match the "room gain" of the car. If you use a bass reflex or bandpass system (which I'm assuming the Bose unit in the Leaf is) then you won't get the advantage of room gain to very low frequencies as the gain increases at 12dB/oct but the woofer output falls at 24dB/oct, so there will still be a certain point where the bass cuts off fairly abruptly.
I'd be surprised if the Bose sub in the Tekna will ever get to 50hz, I suspect it will be nearer to 150hz with maybe a few harmonics below that.
It does have it's own little amplifier in the box btw.
Tony.
Instead of guessing do some measurement or testing... :)

It operates from about 30Hz to 60Hz, there is almost no output above 60Hz and that's where it crosses over with the front door speakers which go down to roughly 60hz. Output is pretty solid down to about 35Hz and the fundamental is still audible at 30Hz, below that you'll only hear some doubling. I haven't opened it but I'm guessing its a bandpass box with an upper cut-off of 60Hz.

The fundamental error Nissan (or Bose) made with this subwoofer is they completely botched the level matching between the subwoofer and the other speakers in the car - the subwoofer level is around 6 to 8dB below the level of the front door speakers at the crossover point. As a result the summed response is overpowering in the mid and upper bass leaving an almost inaudible low bass response. In the default configuration the subwoofer might as well not be connected.

When I set the Font/Rear fader to -2 it's reducing the drive to the front door speakers by approximately 8dB while keeping the drive level to the subwoofer (and rear door speakers) the same, this gives a much more agreeable match and has the subjective effect of extending the low frequency response from 60Hz down to about 35Hz.
 

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Are you sure the amp is in the right suspension turret and not in the same box ? I was under the impression it was a fully integrated woofer/amp, but I haven't had mine out to be fair.
There is definitely an Amp in the suspension turret and the wiring for the sub passes through it, but it may not be doing anything for the Sub which I haven't opened up.

@andrew*debbie posted a couple of useful drawings and further information here:

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All true to a large degree but you're forgetting one critical point - a car is not the same acoustic environment as a living room or outdoors. You don't need nearly as much driver volume displacement for the bass in a car to reach the same SPL at the listeners ears due to it being such a small, enclosed environment many times smaller than even a small British living room. In a sense you're actually sitting inside the speaker cabinet when you're sitting inside a car.

Furthermore because it's such a small, more or less pressurised environment you get 12dB/oct "room gain" below a certain corner frequency which depends on the volume of air in the car. In a typical car the size of a Leaf that turnover frequency is approximately 50-60Hz, that means in theory if you build a closed box woofer system with a natural roll off of 12dB/oct that starts at around 50-60Hz, the "room gain" of the small car environment counteracts the natural closed box roll off resulting in a near flat response to stupidly low frequencies, or in practice well below 30Hz due to the car being imperfectly sealed.

This is exactly the same principle that allows miniature in-ear ear buds to go down to stupidly low frequencies of around 25Hz or even lower with ease. If you test them you'll find the resonant frequency of the driver is well into the lower midrange with a free space roll off of 12dB/oct below that, but this matches the "room gain" of the tiny ear canal resulting in a perceived flat response down to very low frequencies.

This is why car subwoofers are often closed boxes not ported - they better match the "room gain" of the car. If you use a bass reflex or bandpass system (which I'm assuming the Bose unit in the Leaf is) then you won't get the advantage of room gain to very low frequencies as the gain increases at 12dB/oct but the woofer output falls at 24dB/oct, so there will still be a certain point where the bass cuts off fairly abruptly.

Instead of guessing do some measurement or testing... :)

It operates from about 30Hz to 60Hz, there is almost no output above 60Hz and that's where it crosses over with the front door speakers which go down to roughly 60hz. Output is pretty solid down to about 35Hz and the fundamental is still audible at 30Hz, below that you'll only hear some doubling. I haven't opened it but I'm guessing its a bandpass box with an upper cut-off of 60Hz.

The fundamental error Nissan (or Bose) made with this subwoofer is they completely botched the level matching between the subwoofer and the other speakers in the car - the subwoofer level is around 6 to 8dB below the level of the front door speakers at the crossover point. As a result the summed response is overpowering in the mid and upper bass leaving an almost inaudible low bass response. In the default configuration the subwoofer might as well not be connected.

When I set the Font/Rear fader to -2 it's reducing the drive to the front door speakers by approximately 8dB while keeping the drive level to the subwoofer (and rear door speakers) the same, this gives a much more agreeable match and has the subjective effect of extending the low frequency response from 60Hz down to about 35Hz.
Simon- There is an element of truth in your contention, most of my experience has been with massive PA with subwoofer systems for large venues, I have installed/repaired many Bose cannon systems in multiple nightclubs and other venues for instance. When designing these systems, there are many factors to be taken into consideration, apart from the physical characteristics of the venue, furnishings, curtains health and safety etc., and I know how the smallest change can throw all the most careful calculations and measurements out of the window.
That is why I know from experience there is no point whatsoever in attempting to test the inside of a vehicle for optimum sound levels. As you point out, you are literally sitting inside the speaker enclosure.
I would dispute the assertion that you gain extra bang at the lower frequencies in a vehicular environment.

If you have the time, take a look at this paper by Southampton University. It is mainly concerned with active noise cancelling in a car environment, but they don't even attempt to show any frequencies below 200hz.(PDF) Sound Field Control in the Automotive Environment
 

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Simon- There is an element of truth in your contention, most of my experience has been with massive PA with subwoofer systems for large venues, I have installed/repaired many Bose cannon systems in multiple nightclubs and other venues for instance. When designing these systems, there are many factors to be taken into consideration, apart from the physical characteristics of the venue, furnishings, curtains health and safety etc., and I know how the smallest change can throw all the most careful calculations and measurements out of the window.
That is why I know from experience there is no point whatsoever in attempting to test the inside of a vehicle for optimum sound levels. As you point out, you are literally sitting inside the speaker enclosure.
I would dispute the assertion that you gain extra bang at the lower frequencies in a vehicular environment.

If you have the time, take a look at this paper by Southampton University. It is mainly concerned with active noise cancelling in a car environment, but they don't even attempt to show any frequencies below 200hz.(PDF) Sound Field Control in the Automotive Environment
Sounds nice. Years ago I used to import and flog Bose stuff on eBay for a good profit until shutdown by the vested interests :(:LOL: What's the current term... side hustle?
 

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Simon- There is an element of truth in your contention, most of my experience has been with massive PA with subwoofer systems for large venues,
Yes, a totally different scenario. Car audio is quite unique due to the small volume of air that the bass is trying to "pressurise", and the short length of a vehicle interior puts your lowest "room mode" quite high in frequency - typically around 60-70Hz for a 2.5 metre long cabin interior.
I would dispute the assertion that you gain extra bang at the lower frequencies in a vehicular environment.
Have a look at the following graph - it's room gain/cabin gain measurements taken from many different cars by JBL.


While the different cars vary a lot and you don't get a full 12dB/octave at the bottom end (due to air leaks basically, a car is not fully airtight) the upwards trend below about 70Hz is universal and is pretty clear. The room/cabin gain effect is very real and all high quality car stereo systems (of which the Leaf is NOT one! :) ) take this into account and this is why good OEM car stereo installations are bespoke to each model of car including the hidden EQ curve when the controls are set to "flat".

It's relatively easy to do these kind of measurements yourself as you can just do a nearfield measurement of a test woofer (which gives more or less free space response accurate from 200Hz down to as low as the woofer can go) to establish it's own response, then put the woofer in the rear of the car and a microphone in the front and take a normal measurement. Subtract the two and you have cabin gain measurements like those in the graph.

Another way to look at it - have you ever put a measurement microphone inside a sealed box woofer ? If not, try that some time... :) You'll find that the low frequency response inside the box slopes up at the bottom end. This is analogous to the listener being in the "box" that is a closed car cabin.

Don't get me wrong - I'm not saying the system in the Leaf is great. It's not, it's mediocre, but some of that is due to improper setup and integration of the drivers. And it does genuinely go down to 35Hz and produce fundamentals there once the level imbalance issue is corrected with the Front/Rear fader. Of course it can't produce high SPL, it's only a small driver. But at normal listening levels you are getting fundamentals down to a little below 35Hz you're not just getting harmonics as you suggested earlier.

Hell, I've got a small pair of bass reflex bookshelf speakers set up in the kitchen with 4" drivers and they go down to about 50Hz in a room much larger than a car cabin, so a similar size driver in a suitably tuned bandpass enclosure in a much smaller sealed car cabin environment is capable of going lower than that.
 

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Simon, thanks for the graphs, I learned something from them.
My main contension is the fact that a 4" speaker is incapable of producing a frequency range down to anything much below 150hz. I know since my college days technology has moved on a bit, but even with modern esoteric materials available, you are still limited by physical constraints. You can't put a quart into a pint pot.
Interesting discussion, thanks for your input.
 
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