Feedback/Advice Wanted: 250L Subwoofer Design (Dayton Audio SS18-22)

[Markie Warkie]

Hi everyone,

I’m planning a custom build of two large subwoofers for my dedicated home theater space, and I want to get some objective, measurement-focused feedback on my design parameters before moving forward with cutting wood and assembling the enclosures.

The goal is high-output, low-distortion performance with clean extension down to the low 20 Hz / sub-20 Hz region. I’m leaning toward a ported desugb rather than sealed to maximize efficiency at the bottom end.

Room Dimensions & Acoustic Context​

• Dimensions: 4.9m Wide x 6.6m Deep x 2.9m High (~32.3 m² or ~94 m³ total volume)

Cabinet Design Parameters​

• Drivers: 2x Dayton Audio SS18-22 18" Signature Series subwoofers (each in its own independent enclosure).
• Enclosure Type: Ported / Vented.
• Internal Volume: ~250 Liters net internal volume per cabinet (accounting for internal bracing and driver displacement).
• Port Specs: Port length1179.8mm
  Cross-sectional area 321.6 cm²
  Port volume37.9 L
  1st port resonance145.4 Hz

Below, I have attached images of my current simulation graphs showing the predicted transfer function response, along with a 3D render of the enclosure mockup showing my tentative layout.

I plan to integrate and measure the final performance using REW and a UMIK-1 microphone once everything is in place. I would highly appreciate any data-driven critiques, structural bracing advice, or optimization suggestions.​

Thanks in advance!

 

[CherylJosie]

This

and this

are breaking my brain. They look like dead air, completely entrapped.

 

[Markie Warkie]

This
View attachment 545007
and this
View attachment 545008
are breaking my brain. They look like dead air, completely entrapped.

Hey sorry for the confusion theres sopposed to the Cutouts but i dissabled them accidentally

 

[technodanvan]

What is the tuning and expected power input for this? I had this sub loaded up already for Josie and, based on your graphs, it might be tuned a little on the low side. I'm guessing you're using around 800 watts?

Is there a graph that shows excursion vs. the 26mm of listed Xmax for this driver at that power level? For comparison, this is tuned to about 25 hz (a pair of 6" diameter ports, ~0.5m long each, cross-sectional comparable to yours @ 365 cm2).

 

[CherylJosie]

What is the tuning and expected power input for this? I had this sub loaded up already for Josie and, based on your graphs, it might be tuned a little on the low side. I'm guessing you're using around 800 watts?

Is there a graph that shows excursion vs. the 26mm of listed Xmax for this driver at that power level? For comparison, this is tuned to about 25 hz (a pair of 6" diameter ports, ~0.5m long each, cross-sectional comparable to yours @ 365 cm2).

View attachment 545032

View attachment 545033

View attachment 545034

I think it would be more instructive to simulate this driver with a pair of its passive radiators than with a pair of ports. Lower tuning of 21Hz in a similarly sized box seems doable and the box design can be simpler. Port harmonic resonance is not an issue either. Major concern would be group delay and overhang with such heavy weights on the passive radiators, but presumably with all that displacement available, the output should exceed the ported design with higher efficiency and lower distortion? Not sure, I don’t have much experience with these things, and tunable passive radiators add an extra dimension of tradeoff that I’ve never simulated, though I’ve done sear-of-pants implementation before home computing was capable of this level of simulation.

https://www.parts-express.com/Dayton-Audio-SS18-PR-18-Signature-Series-Passive-Radiator-295-737

 

[technodanvan]

I'm more familiar with using passive radiators in speakers and small subwoofers but the theory is the same - they offer extremely similar performance to a ported enclosure but are often used when either the modeled enclosure is too large to be acceptable or the port simply won't fit due to length requirements. They also remove the risk of port noise (chuffing) at high volumes. Otherwise, IMO, a properly designed ported enclosure vs a properly designed passive radiator one should basically perform the same.