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Discussion Starter #1
Hi everyone,

I bought a Dayton Audio RSS265-HO 10" 4 Ohm subwoofer and would like to build a ported enclosure for it.
I plan according to WinISD's recommended 0.7 cu.ft, tuned to 27-29 Hz.
With outer dimensions of about 13x13x18 inch, the slotted port height is around 11.5" by 1", and 45" long.

In other words, I have a very long port for the box size and I wonder how should I fit it in?
I read somewhere that a port should have minimum bends at the minimum possible angle in order to avoid turbulence.

First option:

274894


This way, the port has only one 180 degree turn, and two 90 deg turns.
On the other hand, it has long linear lines which I need to figure how to brace.

Second option:

274895


Here we have four 180 turns. On the pro side - the port panels are shorter and should vibrate less since most of them have the same air velocity on each side (except for the leftest one which separates port air with outer air), since equal air speed = equal pressure on both sides of the panel = no vibration. Correct me if I'm wrong.
Also the box should be more rigid since each port panel is also a brace in essence.

So - which is the better option and why?
Are there any better options that I'm missing?

Thanks!
 

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That screams use a passive radiator instead, there is likely a matching or good match Dayton Audio passive radiator to pair up.

WinISD Pro will do passive radiator, but you will have to enter the box volume you want.
 

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I got bored, there is indeed a matching Dayton passive radiator, it has enough xmax to get by with just one.

Single 75 gram disk gets it fairly close to the default ported design in WinISD, a little more gain midband but rolls off faster on the low end. With cabin gain it is probably close enough to build, but a little tweaking could do better for sure.
 

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Discussion Starter #4
Thanks for the advice, but I'll stick to the ported design:

1. I don't want to spend more $$.
2. The ported design achieves flatter response that extends lower.
3. I am not intimidated by the enclosure design complexity.
4. I don't have a DSP to tweak the passive radiator outcome.

Is there something I'm missing out?
If not - which ported design should I go for?
 

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Discussion Starter #6
You are giving up nearly half of your enclosure for a port. 🤷‍♂️
Yep.
That's the thing with this subwoofer. It requires a very small enclosure (either sealed or ported). It makes a weird design when going ported, but that's the specs of the sub.

That is the root of the problem I described in the first post.
 

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Yep.
That's the thing with this subwoofer. It requires a very small enclosure (either sealed or ported). It makes a weird design when going ported, but that's the specs of the sub.

That is the root of the problem I described in the first post.
Has the sub been modelled with WinISD?
Or are you going off the manufacturers recommendation?

With the volume lot to the port, I might also be considering a passive and port in a dual bass reflex mode with the speaker in the middle...?

But it screams passive radiator to me as well.
 

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Discussion Starter #8
Has the sub been modelled with WinISD?
Or are you going off the manufacturers recommendation?
Modeled with WinISD.

With the volume lot to the port, I might also be considering a passive and port in a dual bass reflex mode with the speaker in the middle...?

But it screams passive radiator to me as well.
Why would you say that? What's wrong with simply ported?

Anyway, since passive radiator is currently not an option (you haven't convinced me yet), which port design would you guys go for and why?
 

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I am amazed that you haven't figured out that by using a passive radiator you can half the size of the box.

Sent from my SM-G965U1 using Tapatalk
 

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Discussion Starter #10
I am amazed that you haven't figured out that by using a passive radiator you can half the size of the box.

Sent from my SM-G965U1 using Tapatalk
I have, but there are other considerations due to which I choose ported (listed by priority):

1. Better aka flatter, lower extending frequency response.
2. I'm fine with the ported box size.
3. 150$ Cheaper (~70$ for the passive, 60$ for the shippong + local tax).
 

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A straighter port will work more closely to how it's modeled. Bracing is trivial, put anything in the center of the port.
 

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Less turns and 45 the inside and outside angles.
 

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I have, but there are other considerations due to which I choose ported (listed by priority):

1. Better aka flatter, lower extending frequency response.
2. I'm fine with the ported box size.
3. 150$ Cheaper (~70$ for the passive, 60$ for the shippong + local tax).
Your answers #1 and #2 indiciate that you may not under how a passive radiator differs from a port.

 

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Discussion Starter #14
Your answers #1 and #2 indiciate that you may not under how a passive radiator differs from a port.
I do, but it is a very nice explanation.

I figured the frequency response by WinISD simulation (Dayton RSS265 PR 10" with 500g added mass vs ported 0.67 sq.ft, tuned to 29.5 Hz):

274990
 

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Discussion Starter #15
The SPL graph (at 300W) does show a more similar pattern, but I don't think I need to spend the extra $$ unless I really want a smaller box, which is not the case (yet). Nor am I concerned of port noise since I listen in moderate volumes.

274991
 

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make your box .8 cu ft tuned @ 32hz then you can eliminate the 180 degree turn at the end of your port. That driver won't hit super low so no real need to tune 27-29hz

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275003
 

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I’d make the box slightly bigger, that’ll make the port shorter. Upsize the box using the first design until you can eliminate the first leg of the port, I bet the box ends up only slightly bigger overall and you can keep the low tune.

Basically I sort of agree with platoon...
 

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Sorry if I misunderstand ports- can't you just use a smaller port area, decreasing the length, and increasing the air velocity? Is there reason to avoid that, since you don't mind noise/listen at casual volume?
 

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How do I calculate effective port length when doing 45s?
Inside length + outside length, and then divide by 2.

Chamfers on the skinny parts, should also help smooth the transition, so as to decrease noise a bit more where the air makes a hard U turn.
 
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