A90 Subwoofer - Any And All Info Pertaining To Subs

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30MilesOffshore

30MilesOffshore

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Excellent work tadda! The open ports were an excellent idea to decrease the exhaust pressure being trapped in the chamber. The foam also has a nice OE look to it and blends in great! I put my car back together already and wished that I hadn't because I still want to mess around with it. Thanks for posting up!

Just to clarify your steps with the back plate, you took the aluminum mounting brackets off, then cut and put the foam in place, and then trimmed the foam to reinstall the aluminum brackets into the foam? That's what it looks like in the pictures and would provide the tightest seal around the brackets.
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tadda

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Excellent work tadda! The open ports were an excellent idea to decrease the exhaust pressure being trapped in the chamber. The foam also has a nice OE look to it and blends in great! I put my car back together already and wished that I hadn't because I still want to mess around with it. Thanks for posting up!
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I'm thinking I want to try what you did plus I'm also interested in seeing how a low pass filter will work with the system. I feel it's not getting a clean enough signal for my liking. I found these 80hz 8-Ohm Filters and think they might help give me what I'm looking for.

https://www.parts-express.com/parts-express-80-hz-low-pass-8-ohm-crossover--266-442
I would suggest first lining each enclosure with 1" wadding and adding a port before adding a low pass...I think you might find it's not necessary...I'm extremely pleased with the low bass response now...
 

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Just to clarify your steps with the back plate, you took the aluminum mounting brackets off, then cut and put the foam in place, and then trimmed the foam to reinstall the aluminum brackets into the foam? That's what it looks like in the pictures and would provide the tightest seal around the brackets.
I didn't remove the mounting brackets...I actually used a 4"h length of 2" foam and cut slits into the foam such that the foam could be worked in from the top behind each of the brackets...

Subwoofer 5 2 inch foam insulation.jpg


Excuse my crude foam cutout drawing with dimensions

foam template.jpg
 
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tadda

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And I was actually able to slide in the 1" wadding to line the enclosure walls through one of the elongated exhaust ports...I didn't even need to remove top cover! It take some manipulation once the wadding was in the enclosure to make sure it unfolded against all the walls....Also, I made sure the wadding wasn't covering the exhaust port area...

subwoofer 4  enclosure partitions with wadding and speaker flow.jpg
 

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Looks good. Can't wait to try it. Did you think about covering the port holes with fabric or mesh to keep debris out?
 

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Looks good. Can't wait to try it. Did you think about covering the port holes with fabric or mesh to keep debris out?
Thanks! I really didn't think that would be an issue...just play some low bass and blow it out...ha! just kidding!

It's interesting to note that during heavy bass play how much air is released outwards from the port...

But yes, initially thought about adding this speaker grill below...

exhaust port cover.jpg


But I thought the 2" ported tube would be a better option for channeling the energy outwards...I still may end up adding a black mesh screen over the three elongated ports of the enclosure...

subwoofer port tube.jpg
 
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Sound Check 4:

Gutted the rear trunk again last week and played around with filtering. Currently, feel that the subs frequency and band pass width is too high for my personal liking (approx 100Hz range). I've heard 6x9 that thump harder than these. Wanted to see if I could fine tune this anymore so I added another filter to see what would happen. I had a few expectations before hooking it up: (1) narrowing the frequency range (2) shifting the tuned frequency to a lower Hz.

Filter Used: 80Hz Low Pass 8ohm Crossover (12dB/oct)
https://www.parts-express.com/parts-express-80-hz-low-pass-8-ohm-crossover--266-442

Just made some test connectors and added the filter to Right Sub only and ran some sound checks. I didn't play with the EQ at this time as I wanted to see a direct comparison. After playing several tracks, I began to play with the EQ to see if that would fine tune it even more.

Results:

Definitely lowered the frequency response of the sub. Cut down on vibrations as the sub was focusing on a lower frequency. Sound was cleaner as the sub had eliminated the higher end of the frequency spectrum. But, the one concern I had from past car audio experience did come true. I figured the volume would drop down since the sub was now getting double filtering. The stock HK system was filtering the sub already and then I also added a secondary filter which can lower the output response. Just judging from listening to several tracks I would say the volume was decreased by about 20%. This was a significant difference in my opinion and really hurt the results. So overall, it filtered and cleaned up the sound as expected, but cut the volume too much to make up for the cleaner sound.

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25874.png
 

tadda

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Sound Check 4:

Gutted the rear trunk again last week and played around with filtering. Currently, feel that the subs frequency and band pass width is too high for my personal liking (approx 100Hz range). I've heard 6x9 that thump harder than these. Wanted to see if I could fine tune this anymore so I added another filter to see what would happen. I had a few expectations before hooking it up: (1) narrowing the frequency range (2) shifting the tuned frequency to a lower Hz.

Filter Used: 80Hz Low Pass 8ohm Crossover (12dB/oct)
https://www.parts-express.com/parts-express-80-hz-low-pass-8-ohm-crossover--266-442

Just made some test connectors and added the filter to Right Sub only and ran some sound checks. I didn't play with the EQ at this time as I wanted to see a direct comparison. After playing several tracks, I began to play with the EQ to see if that would fine tune it even more.

Results:

Definitely lowered the frequency response of the sub. Cut down on vibrations as the sub was focusing on a lower frequency. Sound was cleaner as the sub had eliminated the higher end of the frequency spectrum. But, the one concern I had from past car audio experience did come true. I figured the volume would drop down since the sub was now getting double filtering. The stock HK system was filtering the sub already and then I also added a secondary filter which can lower the output response. Just judging from listening to several tracks I would say the volume was decreased by about 20%. This was a significant difference in my opinion and really hurt the results. So overall, it filtered and cleaned up the sound as expected, but cut the volume too much to make up for the cleaner sound.
Good stuff @30MilesOffshore ! :thumbsup:
 
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tadda

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@30MilesOffshore

While you had the top subwoofer enclosures removed did you consider opening up the top rectangular openings into the metal enclosure or at least remove the center metal stip between the two as shown in this pic below?

ported sub opening.jpg


subwoofer 2 underside.jpg
 
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@tadda I gave it some thought but I'm not sure if it will make any improvements. I feel the air flow is pretty good right now. I think by modding this opening it will decrease the rigidity of metal and possibly cause more vibrations. I think dampening the inner chamber made a huge difference.

The section you have red and blue I applied two sheets of deadening. I applied them to the underside so you can't really see them. It's hard to get a picture in there.

Picture below: Green area is where I'm referring to

ported sub opening.jpg
 

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@tadda I gave it some thought but I'm not sure if it will make any improvements. I feel the air flow is pretty good right now. I think by modding this opening it will decrease the rigidity of metal and possibly cause more vibrations. I think dampening the inner chamber made a huge difference.

The section you have red and blue I applied two sheets of deadening. I applied them to the underside so you can't really see them. It's hard to get a picture in there.

Picture below: Green area is where I'm referring to

ported sub opening.jpg
I feel as if that strip could be removed, but not sure how much more of an improvement it would make...I also thought about removing material in center of 3 elongated holes as well but also though the same, i.e. that it might actually reduce structural wall integrity making it less rigid and more susceptible to vibrations...

good stuff btw! :thumbsup:
 

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@30MilesOffshore do we know for sure the two subs are ran parallel? I was thinking of going Audison and putting in their bmw sub replacement, using it as the woofer for the front 3 way setup.
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