Hello all! My 1st 18" PA sub simple build
Printed From: Speakerplans.com
Category: General
Forum Name: Newbie Discussion
Forum Description: Newbie Discussion/Questions. Look less stupid here...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=109469
Printed Date: 26 March 2026 at 5:30pm
Software Version: Web Wiz Forums 12.08 - https://www.webwizforums.com
Topic: Hello all! My 1st 18" PA sub simple build
Posted By: Sidhu
Subject: Hello all! My 1st 18" PA sub simple build
Date Posted: 06 March 2026 at 11:17am
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Hi folks! I've zero building experience nor tools, so will use a local speakerbox shop to cut/assemble this for me. They have a CNC router. Target is to improve on the JBL SRX/STX subs in a budget. Driver im hoping to use the the P.Audio GM18-1800N, which i believe to be a budget clone of the B&C 18SW115. Front slot for ease and convenience. I have available to me a full DSP suite to fine tune, including FIR and IIR. Amplification can be 1200-1300watt Class D or Class H heavy. Eventually i would aim to build 3 pairs so I can do cardioid setups. I will use winisd for sim, then speakerbox.pro for box construction and built in Fusion360, all new to me and learning as I go. I have accounted for, hopefully correctly, 10.5L for driver displacement and another 2 for bracing, handle recesses etc. Please assist me on this build. Many thanks and gratitude. I will post my work next. Best, Sidhu
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Replies:
Posted By: Sidhu
Date Posted: 06 March 2026 at 7:20pm
The TS parameters are identical to the B&C 18SE115 apparently.
WinIsd
Port velocity is peaking @ 19.85m/s 38.66Hz Similar input in https://simulator.00aud.io/ - Enclosure Simulator | 00 Audio yeilds higher port velocity, but im not going to be at 1800watts.     Looks ok? Next ill model in Subboxpro
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Posted By: Sidhu
Date Posted: 06 March 2026 at 7:38pm
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Subbox pro. Woofer displacement set to 10.5L (ill see what braces addup to in Fusion and possibly adjust) Panel list is:
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Posted By: Larry23
Date Posted: 08 March 2026 at 12:07pm
Hi Sidhu  Looking at the modelled frequency response, with - 3db points around 38hz and 68hz, it looks like you could improve the alignment to increase overall efficiency and useable bandwidth quite a bit. I'll have a play with the driver and see what I come up with.
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Posted By: Sidhu
Date Posted: 08 March 2026 at 1:30pm
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Much thanks Larry! I am not too sure what it all means in the real world, or how these sims translate. Once I build and measure ill have a better understanding of the correlation im hoping. My attempt was to keep port velocity and excursion in check and an SPL above 120, This was the only permutation combination resembling common box dimensions that fit that i could figure. Complete driver details:  |
Posted By: Sidhu
Date Posted: 09 March 2026 at 7:53am
I was thinking of running these with the tops cross at 80 LR4, so I was perhaps thinking the -6db points is of importance, ofcourse happy to get more. |
Larry23 wrote:Posted By: fudge22
Date Posted: 09 March 2026 at 12:12pm
The limited bandwidth is more likely due to the use of HPF 4th LR @30 // LPF 4LR@80 than the cabinet tuning. |
Posted By: Larry23
Date Posted: 09 March 2026 at 2:32pm
Thanks! Was wondering what I'd missed.. I've not used Winisd before, and something looked very odd. I modelled the same box in Hornresp and it didn't look anything like that...!!
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Posted By: Larry23
Date Posted: 09 March 2026 at 2:45pm
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You might want to see how this looks on your sims. I came up with a different alignment, with larger cab, and lower tuning. Yours appears to be tuned at ~40hz, which sacrifices a bit of low end extension, and has a knee around tuning frequency, before rolling off quickly. I modelled a 180l cab, tuned to 32hz, port exit 500mm x 90mm, length 550mm. Everything seems to be well in check up to and beyond full input power. F3 is approx 28hz.
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Posted By: Sidhu
Date Posted: 09 March 2026 at 3:48pm
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thank you fudge! Here is the 165L @ 38hz tuning without any filters  |
Posted By: Sidhu
Date Posted: 09 March 2026 at 4:02pm
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Thanks Larry, My understanding of WinIsd is that it auto calculates the port length based on the tuning freq. and port width and height, with a 180L @ 32 tuning, i get a port length of 581.8 Bold is 180L box @ 32hz and other is 165L box @ 38tuning, no filters. Transfer:  SPL:  ConeExcursion:  PortVelocity:  I need to educate myself on to best find a box size, so far, within reasonable size, im imagining a tuning freq around the Fs, then finding a box size after a LPF which get the excursion undercontrol, and the transfer most balanced. From here i move to size vents to control the port velocity.
Thanks folks for the time! |
Posted By: Sidhu
Date Posted: 09 March 2026 at 4:27pm
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Below are some Sims with HPF and LPF filter. LPF for both boxes is @ 100hz LR24 For the High pass, I tried to find the best SPL (LR vs BW), while keeping cone excursion under Xmax at full voltage. Mostly playing around and trying to interpret results. Here is what I have entered. 165L @ 38Hz : HPF 4BW@30 180L @ 32Hz : HPF 4BW@27 transfer Xover Mag 180L cab highlighted (filter tab):  SPL Xover Mag 165L cab highlighted (filter tab)  Cone and port:   Thanks folks! I hope this data makes sense. Best Sidhu |