As an opponent of large boxes (smashing windows) or another big boxe in a small trunk, I tried to improve the regular sub in two passes, for which I even bought a clone on web as a guinea pig (30 USD) and a good speaker of my favorite company (it's a matter of taste and everyone's wallet).
My home audio speaker and subs of other LR brothers leaded me to an idea that there is no any bass reflex on Freelander's
subwoofer!
It's a shame ?!
Good or bad, necessary or not - let someone argue elsewhere, going into the specifics of each specific speaker, but I decided to experiment during COVI-19 isolation at home! And I didn’t regret it!
By the way, one feature of the phase inverter was very useful to me - it can be both inside the box and outside. For home speaker design - this is a clear solution - inside! And in our car - there are options - judge for yourself! Sizes, formulas, half a year of searching for various solutions and failures - I'll leave it all outside the brackets. I propose to consider a ready-made solution that does not cause problems in repetition by any Freelander's driver. Have a look at the below pictures!

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Click image to enlarge

Great write up. I am surprised that a phone's microphone will work that low.

Have you thought of 2 smaller diameter ports or even 3 which would give you more clearance & could be recessed, but you would then reduce volume within the enclosure which is not ideal.

Was there any polybatts in the enclosure. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Nothing is ideal.
I have thought about how to offer any solution "easy to repeat" with one port first of all and as I mentioned it was a plan to find the best place inside from the very beginning. Unfortunately there was not space enough inside for my port finally due to specific sub body construction. And I started to search for some free space outside the sub for a port and as result the size has increased during tests and fine-tuning from 145 mm to 175 mm. So free space under the back passenger sit looks like the best solution for me. I'm not familiar with two or three ports system building so you can offer an alternative sub.

But I think all two or three ports will be on the same side finally. I don't see any good alternatives.

I agree that might be mic on smartphone is not the best for low end frequency's analysis

and real low end frequency could be better but it was important to make all tests with one device in one position and on the same level of sound. I did tests 3-4 times for each port size and got the same results with app on smartphone for each of test. So scan's comparison shows some different in results for low frequency and trust me it could be heard easily as well. I plaid on drams in university and I can hear how better bass or double bass and drams are sounds now. I wish to find some lab for correct final test for all frequency spectrum after I will finish all speaker changings and some fine tuning for each of them by myself. For example I changed capacitor on TBe tweeters (from black to red) and result was wonderful! But I have to play again with it's signification to make spectrum flat.

Click image to enlarge

If you have the 'Thiele-Small Parameters' ie data sheet for the speaker you can calculate the port length. Port area should be 1/3 of the cone area (Sd) for 1 port. 1/4 the Sd for 2 ports. 1/5 the Sd for 3 ports.

http://www.electroziq.org/docs/Designing_B...osures.pdf

If you fill your spare LR subwoofer box with water to measure the volume, my guess is 13 litres. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

I have done an Excel spreadsheet for the Thiele-Small Parameters. I can email the file if anyone wants it, PM me.

Imperial input as this seams to be the general state. You can unlock the sheet & change it.
 Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Maybe worth an experiment with larger pipe (if possible) which will have a longer length.

SVS PC-2000 Pro
 Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

Lightwater wrote:

If you have the 'Thiele-Small Parameters' ie data sheet for the speaker you can calculate the port length. Port area should be 1/3 of the cone area (Sd) for 1 port. 1/4 the Sd for 2 ports. 1/5 the Sd for 3 ports.

http://www.electroziq.org/docs/Designing_B...osures.pdf

If you fill your spare LR subwoofer box with water to measure the volume, my guess is 13 litres.

Have you really checked it with water? The first idea to buy the second sub was about how to use water for volume checking.

But I refuse it later due to there are too much holes in sub. My estimation for the first calculation was taken as V=20L. And as I had to increase the calculated port size from 150 mm to the fine-tuned 175 mm so your estimation with V=13 L looks more correct than mine.

Based on your information my 50 mm tube looks an optimal Diameter for one port in sub with 6,5" speaker.


PS I added more white sintepon inside sub to "increase" value and got around ~22L finally:


 MY13 SD4 HSE Lux
IAM2.1 Level 3
Meridian Premium Surround Sound with Extra Upgrade

I had a quick guess at the volume. I have had it out of the car when I installed the acoustic insulation, but that was quite a while ago.

You could fill it with styrene foam balls.
https://www.bigw.com.au/product/large-bean-bag-fill/p/2828640/

Or rice or lentils & measure the volume. It would be close enough.

Or wrap it in a plastic bag, or two for safety, suck out air to shrink the bag, seal & push it into a garbage bin full of water, which is on a set of scales. The displaced water is the volume & probably at a rough guess reduce by a kilogram for the wall thickness.

Or forget the scales & refill the bin in 1 litre increments. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

I see you really like "to think out of box" with a huge ready set of alternatives! As me.

Could you send me your EXL with calculations for two and three ports? MY13 SD4 HSE Lux
IAM2.1 Level 3
Meridian Premium Surround Sound with Extra Upgrade

I do not have a 3d scanner.

The next best option but it is a lot more work is to photograph it with a long lens on 6 sides, XYZ & -X-Y-Z. Put the photos into a 3d program with some known dimensions. Build a 3d object. Shrink it by the wall thickness. Check all polygons & points are perfect. Calculate volume.

Calculating the volume is the easy bit. The rest is a bit tedious. In bag & water is the quickest! Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

I have started to wish about both 3D devices - 3D scanner and 3D printer...
 MY13 SD4 HSE Lux
IAM2.1 Level 3
Meridian Premium Surround Sound with Extra Upgrade

I sent a PM. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

FL2Vano wrote:

I have started to wish about both 3D devices - 3D scanner and 3D printer...

I'm not an audiophile but fascinated by this thread. In the past I changed speaker capacitors on my Octavia VRS on the advice of forum members with a marked improvement.
What is the benefit in fitting the sub woofer pipe for a listener with average hearing ? Jules

Well, firstly you can get some really ugly sound if you don't get it right. It is far easier to have controlled sound in a sealed box which is very solidly built.

If you get reflex sound right you can extend the bass a bit, but it can sound boomy. Bass traps are used in corners of rooms, an unpacked pack of ceiling batts will do the trick in each corner. It is hard enough to get good sound in a room let alone a car. Filling the car with acoustic insulation has changed the sound in my car. I don't think it is quite as loud as before but it doesn't need to be, as outside the car is a lot quieter.

I agree, this is an interesting thread. One really needs the 'Thiele-Small Parameters' of the speaker to give one an easier starting point. Personally I would rather have quality sound over noise. In a previous life I had KEF GT200 automotive series speakers in the car https://www.mx.kef.com/explore-kef/kef-mus...-gt-models , 2 amplifiers, Van den Hul cables running everywhere, & the first car CD player.

I must be getting old, these days tend to listen to am radio, but still through a pair of Wharfedale E50 speakers. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18