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Discussion Starter · #1 · (Edited)
I made a question to the other thread but I think I need more quidance so I don't wanna borrow the other thread.

I don't think I am allowed to post a picture yet, but I try to explain my issue.

Setup is:
- Maelstrom-X 18" Gen2 element
- 2x EX-PR18 passives
- Behringer iNuke NU6000DSP

Current setup: sealed 3.6cu ft downfiring with 5 inch clearance from the floor.

Looking for a net 7cu ft (200L) tuned to 18Hz with ~1775g on both passives.

I have basically 3 options since I'm space limited. Maximum widht of the box is 41", height 26" and depth 24".

Options:
1. Active element firing front and PR's on the sides. 1 passive is 5 inch from the wall, other 5 inch from the AV table. Volume is 6.7cu ft. The issue is I think with the clearance with PR's. Isn't it enough that the amount of moved air by the passive have free way from the sides (area of the "cylinder" sides is more than the area of the element)? But usually in ported designs it is reguired the same clearance as the port's diameter and in this case it is 18"...

2. Active element downfiring with 5 inch clearance from the floor. Both PR's facing front. Widht would be then 41" and height 21" (PR's fit just in the box). At least it looks COOL :bigsmile:. Volume would be 7cu ft. I think the beast would weight at least 90kg so would moving mass of 3.5kg put the box rocking? Any other issues?

3. Active element facing back to wall, PR's front. This is basically the same as number 2 but active element changes the place. Volume is 7.7cu ft. Then the depth of the box would be 22" (~6 inch clearance from the back wall).

Which one to choose...I think I like number 2 the most but I'm not sure it is the best from the 3 options. So please help! :dontknow:
 

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Discussion Starter · #3 ·
That would be a net internal volume of about 10.5 cu.ft.

For option 1, is there also 5" of clearance at the back of the cabinet from the wall?
Dimensions mentioned are the "space" where I should fit everything. So the internal volume of the box varies from 6.7 to 7.7 in the plans.

For option 1 there is only 2 inch clearance from the back wall.
 

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Discussion Starter · #5 · (Edited)
Thanks Mike, so option 1 is at least feasible.

I'll add one more option:
4. Ported with a flared 8" port max. 110cm long. Internal volume 11.6cu ft. Net volume around 10cu ft. Will have minimum tuning around 16.5Hz. Both element and port facing front (port would have one 90deg turn).

I think I still have options 1, 2 and 4 left. Pros and cons:

1.
+ symmetric PR positioning
+ no port issues
- smallest volume 6.7cu ft

2.
+ "outfit"
+ no port issues
+ slightly larger volume vs. option 1 (7cu ft)
- PR's facing front, possible vibrations
(-) downfiring active element

4.
+ 10cu ft
+ loudest down low with 16.5Hz tuning
- 8" port issues
- large box

With a 1.5dB boost @ 20Hz I get similar kind of response with options 1 and 2 vs. 4 according to winisd (option 4 will of course go a bit lower). Output is 2dB @ 20Hz lower (PR excursion at max), but at 16Hz I get 112dB vs. 117dB so 5dB more with option 4...

I already have the PR's, but I think I can get rid of them if option 4 will be final...this is hard... :scratch:
 

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Discussion Starter · #6 ·
And one more to come:
5. Active element and one PR firing front. Other PR exactly opposite side in the back vs. front PR. Clearance to back wall 5 inches (air flow open to up and other side, side wall around 30 inches away from the PR center). Box size optimized it would give a net volume of 9cu ft. Tuning around 17Hz with 1775g added mass I think.

+ "outfit"
+ no port issues
+ much larger volume vs. option 1 (9cu ft vs. 6.7cu ft)
+ symmetric PR positioning
(-) One PR facing back wall with 5 inch clearance

This would be the choice, if one PR facing back wall is feasible. I already have the PR's and one reason I bought them was to go low without a cuffing port...

What do you think?
 

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Yes for option 5. Your model shows 1475 grams added to each PR. Are they capable of that weight? I added a 11 hz HPF, this model has the same output as your model and protects the driver from over excursion and protects the PR's from maximum excursion which is hard on them.

View attachment The Paarma78 Project.wpr
 

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Discussion Starter · #12 ·
I think I can only put the HPF around 15Hz with the Amps DSP...

I dropped the PR mass to 1400g (Exodus EX-PR18). Total would be then 1700g and tuning around 18Hz. According to application notes, maximum recommended total mass is 1885g.
 

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Discussion Starter · #14 ·

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Discussion Starter · #17 · (Edited)
And this is what I can do with iNUKE DSP:


Upper with iNUKE, so effective HPF will be around 16Hz (2nd order butterworth).

EDIT:

One more with comparison to my current setup (103L sealed with boost):


Effective HPF looks to be around 15Hz now. Driver and PR excursion should be inside the limits...

And here's the "final" project I think.
 

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