Bass output through the hole in the wall.

[Launagis]

Now, that's interesting. And it seems a good opportunity to check my own logic regarding practical implications.
I assume, that Xmax is limiting factor in most scenarios. So I run this kind of simulation through WinIsd:
Two sealed boxes, one 40ltr and one 6000ltr (that would be the volume of the storage room). If we target to hit Xmax at 20hz (I usually put high-pass at 20hz for protection), I get:

40ltr blue, IB green. Power to reach Xmax 88w for 40ltr, 51w for IB.

General SPL at those power levels:

So in the end it would look to me, that with this particular driver I have no real benefits by going with IB - if I equalize output by Xmax at 20hz, IB has less output after that.

Or am I off somewhere?

 

[voodooless]

I would not expect WinISD to model an IB sub properly, especially not with the hole being so much smaller than the woofer is.

 

[audio_tony]

This guy replaced his garage window with a baffle and a large woofer (not practical as the rear of the woofer was outside lol).

 

[somebodyelse]

This guy replaced his garage window with a baffle and a large woofer (not practical as th erear of the woofer was outside lol).

I just get the greyed out area until I click on it, so I was half expecting it to be the one with the DIY fan style sub in the window:

 

[Launagis]

I would not expect WinISD to model an IB sub properly, especially not with the hole being so much smaller than the woofer is.

Sorry, I wasn't clear - in both cases I would cut the hole to 250mm diameter to accommodate woofer, the only difference being the large space or 30-40lrt box behind.

 

[RHO]

Why not design a 4th order bandpass subwoofer?

 

[Launagis]

Why not design a 4th order bandpass subwoofer?

Hm, good question. OK, I did some basic WinIsd modeling with the same driver, Xmax at 20hz with 70w:

There is some reasonable gain in 20-30hz area and some loss after 50hz, which doesn't bother me. Box size seems reasonable and doable. Vent diameter and length (in my case 160mm long and 125mm in diameter) it seems can't be modeled in WinIsd. I'm I fine with the size of the "port"? Also, what does tuning frequency of ~34hz mean in my case?

 

[voodooless]

Vent diameter and length (in my case 160mm long and 125mm in diameter) it seems can't be modeled in WinIsd

Why not? Seems simple enough

 

[Launagis]

Why not? Seems simple enough

Sorry, my bad again. For 125mm diameter it shows vent length to be 1.3m, and for the length to be 160mm, diameter should be 47mm (seems rather low). So I'm back at the start and the subwoofer shown in my first post:

I should make extension for existing hole to be around 1.3m in total and put the box where it lands? Anything I'm not seeing right?

 

[RHO]

Also, what does tuning frequency of ~34hz mean in my case?

That's the tuning of the front volume by the dimensions of the port. You can increase the length of the port by extending it into the enclosure. Or you can make the diameter smaller. Both will result in a lower tuning.
As I understand it, you cannot make it shorter nor want to make it bigger. (which I would do either if I was in your situation)

 

[RHO]

Sorry, my bad again. For 125mm diameter it show vent length to be 1.3m, and for the length to be 160mm, diameter should be 47mm (seems rather low). So I'm back at the start and the subwoofer shown in my first post:
View attachment 435710
I should make extension for existing hole to be around 1.3m in total and put the box where it lands? Anything I'm not seeing right?

Yes, that seems to be the right strategy.

 

[voodooless]

Sorry, my bad again. For 125mm diameter it show vent length to be 1.3m, and for the length to be 160mm, diameter should be 47mm (seems rather low)

Well, yeah, that's how tuning works 125mm is a standard size for PVC pipe I think. It should not be an issue. Just put the box on the floor and connect it with PVC tubing.

 

[RHO]

Is see now that you have 4 drivers.
How much room do you have to build a box?
I don't know how well 4 25cm subs would work with one 125mm port.

 

[voodooless]

I don't know how well 4 25cm subs would work with one 125mm port.

I would not recommend that. Maybe 2 will be okay..

Better get small boxes and put them in other places in the room. Overall, this will give a smoother in-room response.

I modeled the closed variant with a large baffle in another tool (boxsim). 54l vs 1000l doesn't make too much of a difference, maybe 1 or 2 dB on the low end. I would not worry too much about this. A 4th order bandpass will definitely shave a few more dB off of the MaxSPL, an it will drop off below 20 Hz faster than a closed box.

I would almost say that it would not be worth doing the 4th order bandpass in this case.

Bandpass

closed (54l)

Both on BI like baffle. Bandpass does go slightly louder.

 

[Launagis]

As I understand it, you cannot make it shorter nor want to make it bigger. (which I would do either if I was in your situation)

The hole in the wall is 160mm long (the thickness of the wall itself) and 125mm in diameter (metal hvac pipe). I can't make it shorter, and I don't want to make it wider, if I can stay with 125mm and save myself some time by not cutting through the wall. I would cut it wider, if I must, but to make the pipe longer in the storage room is easier.

 

[Launagis]

Is see now that you have 4 drivers.
How much room do you have to build a box?
I don't know how well 4 25cm subs would work with one 125mm port.

I have four drivers, yes, but I have no wish to use them in one spot. The way I see it, I would use one driver in/near the storage room, the other one hides in the shelf and other two good spots are not that easy to hide, but I will have to figure something out. I will try to put subwoofers in different locations to more or less equalize room modes as much as possible. I will try to put all four boxes in those places to test it out before committing to wall cutting.

 

[Ultrasonic]

Whilst this is interesting from a project/theoretical perspective, I would personally block the hole up and use a conventional in-room subwoofer...

 

[dedobot]

Sorry, my bad again. For 125mm diameter it shows vent length to be 1.3m, and for the length to be 160mm, diameter should be 47mm (seems rather low). So I'm back at the start and the subwoofer shown in my first post:
View attachment 435710
I should make extension for existing hole to be around 1.3m in total and put the box where it lands? Anything I'm not seeing right?

Back in the days I had such thing ...a air filter for the grow box in living room

 

[Launagis]

I would not recommend that. Maybe 2 will be okay..

Better get small boxes and put them in other places in the room. Overall, this will give a smoother in-room response.

I modeled the closed variant with a large baffle in another tool (boxsim). 54l vs 1000l doesn't make too much of a difference, maybe 1 or 2 dB on the low end. I would not worry too much about this. A 4th order bandpass will definitely shave a few more dB off of the MaxSPL, an it will drop off below 20 Hz faster than a closed box.

I would almost say that it would not be worth doing the 4th order bandpass in this case.

View attachment 435711
Bandpass

View attachment 435712
closed (54l)

Both on BI like baffle. Bandpass does go slightly louder.

Very interesting. The way I see this:
At 10hz, the output is almost identical - around 78dB. At 20hz, bandpass pulls ahead with 95dB vs 92dB. Sealed goes to reach higher SPL with 110dB vs 105dB. So, if I cut anything below 20hz and equalize everything above to be flat to 20hz level (which means pulling down everything above 20hz), 4th order bandpass would give 3dB extra headroom. I know this is theoretical, but am I right in my assumptions?

 

[Launagis]

Whilst this is interesting from a project/theoretical perspective, I would personally block the hole up and use a conventional in-room subwoofer...

I will not do that! I want hidden subwoofers.