2023 SBA GSub Alternative
Printed From: Speakerplans.com
Category: Plans
Forum Name: Ported Enclosures
Forum Description: Post all your reflex and bandpass and 'other' boxes with holes in stuff here...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=107939
Printed Date: 26 March 2026 at 6:55pm
Software Version: Web Wiz Forums 12.08 - https://www.webwizforums.com
Topic: 2023 SBA GSub Alternative
Posted By: vertx
Subject: 2023 SBA GSub Alternative
Date Posted: 15 June 2023 at 10:05am
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Design Goals Also, as CNC and CAD is more accessible today in 2023 than in 2001 (GSUB) - this design will include full 360 CAD model available to download in all standard 3D file types, in addition to 2D CNC layout nesting for your local CNC shop. Suitable for entry level sound systems looking for a cheap but high quality 2x18” design with stacks of low end that doesn’t require large amounts of amplifier power and when truck pack sizing is not an issue. Should anyone wish to build I'd be happy to provide some build advice along the way and come and perform some calibrated measurements of frequency response, maximum real world SPL, waterfall and other time domain measurements, and impedance via REW + DATS. 3 x 18mm B/BB Birch Plywood $550 AUD 2 x SBaudience ROSSO-18SW650 = $700 AUD 1 x Neutrik ST-NL4MPRXX = $7 AUD 1 x Titebond Ultimate 3 Wood Glue 1L = $36 AUD 16 x M6 threaded inserts/furniture nuts = $17.60 AUD 16 x M6 40mm bolts = $12.80 AUD 1 x Bag of R2.5 polyfil = $100 AUD CNC machining time = Depends on your shop but I'd guess this would be between $600 - 1200 AUD 1 x paint, varnish, oil, etc. to builders choice = .......... Total Cost Guide = $2023.4 AUD I'd say you could absolutely do it for less if you were frugally minded - also good to keep in mind going with four 'adequate driver' 2x18's for a system is more displacement/output at maybe similar cost than going for half as many, very expensive big BL/XMAX neo jobbies. As these are 'relatively low wattage' per box before XMAX limit you may well get away with running two enclosures per side off one of your select fav Chinese 1RU Class D amps at a 2ohm load per side and still have some headroom to spare. for those sweet sweet transients, keeping your amp rack costs low and allowing you to live the dream whilst still making rent. Fusion model URL: https://a360.co/3PeIrfL" rel="nofollow - Construction should be easy peasy - all butt joints ready for screw/glue or glue/clamp action. I would recommend Titebond Ultimate 3 for any outdoor use as it's waterproof, not to mention easy to work with. Drivers should be bolted into the 36mm double thickness baffle using long M6 threaded inserts/furniture nuts screwed into the rear of the baffle before full assembly and glue-up. If you have a router handy, and either a large radius chamfer or round-over bit (10-12mm for example) it might be worth running it over the long edges (540mm) of the inside and outside of the main port walls, unlikely to give much of an audible difference but it will look quite nice. I would also recommend using a large radius round over bit for all external enclosure edges to assist with ply peel/delaminate over time - especially if you will not be painting the enclosure. Grilles should be made of 2-4mm powdered coated stainless steel and fixed to the baffle grille strip via builders choice. SpeakOn connector plug rebate size is for a Neutrik ST-NL4MPRXX Drivers: 2 x SBAudience ROSSO-18SW650 Material - 18mm Birch Plywood Limiting factor in design: Linear driver XMAX (Same as GSub tbf just with more output before XMAX) Other notes: My personal experience with using GSubs is that when driven hard both port chuffing and power compression is an issue. Power compression is harder to get around without cooling systems, but the chuffing caused by air velocity in the vent is reduced in this design compared with the GSub by using a slightly larger port volume/dimensions so when EQ’ing at port tuning frequency to get that extra extension and output we are not exacerbating the chuffing on musical peaks, therefore reducing the levels of acoustic distortion and increasing cleaner output. Comparison to GSub via WINISD: Max SPL at XMAX for both - Purple is the SBA ROSSO, dark green is PD.186. Filters: 24db Butterworth HP at 29hz Simulated response (with no EQ at port tuning frequency) = 32hz to 200hz usable frequency range (-6db) Simulated response with PEQ at tuning = -3db at 33hz
Enclosure Gross volume = 436.10400 litres Minus Drivers = 16.16 L Minus Bracing = 4.66 L +2.65 L + .8 L = 8.11 L Minus Handles = 13.65 L (Port/vent volume already excluded) Total = 37.92 L Enclosure Net volume = 398.19 L
Looks like there may even be an extra 1/2 remaining on the last sheet you could use to make a set of dolly boards to lug your amps/subbies around with And above all else, remember to have some fun, make some saw dust, and play it loud! ------------- www.instagram.com/translate.sound |
Replies:
Posted By: smitske96
Date Posted: 15 June 2023 at 11:56am
| Nice one! On how much port area did you settle eventually? |
Posted By: vertx
Date Posted: 15 June 2023 at 12:17pm
I've updated original post with some reference drawings (for those without a web browser that will let them Live View the 3D CAD model which lets you explode, measure, view/hide individual bodies) so that should cover the dimensions, just 30mm wider and 76mm taller and a little deep by a few mm I believe (port dimensions).
------------- www.instagram.com/translate.sound |
smitske96 wrote:Posted By: vertx
Date Posted: 15 June 2023 at 12:21pm
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Also I should note I'm more than happy to update this design for people based on any comments/feedback/etc I'm not attached to it at all, but was thinking this afternoon how well the GSubs have done for me over the years and thought if I can design something that AUS/NZ people could use in lieu of the GSub (especially now shipping is extra $$$) then why not knock it out in Fusion/WinISD and make it accessible!
------------- www.instagram.com/translate.sound |
Posted By: Aurora
Date Posted: 20 June 2023 at 1:52pm
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Looks like a good design, I'm weighing up the idea of getting some 2x18 reflex boxes built but have yet to settle on a design, I was thinking about the G sub but would making it wider achieve any differences with the port noise, i.e making it 636mm wide instead of 536mm, It was designed 20 odd years ago when drivers were only rated for 500-600w now drivers are 1000w+. |
Posted By: vertx
Date Posted: 21 June 2023 at 2:15am
Generally I'd recommended thinking about your goals/design targets first. i.e How many people do you plan to cover, indoors or outdoors, etc. You may not need fancy flared port 2x18" with high BL/high XMAX/High cost drivers. You're targets might be better met with more less costly drivers providing more displacement. That's sort of the point of this GSub alternative. Once you start looking at high power modern drivers, standard ports won't allways cut it. To have a rectangle port large enough to handle the additional vent velocity becomes impractical, not to mention (and these next comments are my personal belief only and I have yet to prove with measurement but these will come) has reduced output, which is a function of a not only a choke-up of air in the vent and particle shredding, but less smooth/efficient acoustic impedance match between driver and enclosure and the way they interact to form an acoustic system, not to mention port gain becomes nonlinear without a port flare at high output, and also reduced port gain bandwidth (this last one is a possible big one I'm looking into i.e optimising port gain bandwidth via use of flared vents). A few months back I sent my brother, a developer, all of the available information I could find regarding optimising vented enclosure ports for maximum output - he has come up with a very early version of a web app that one day after lots more testing could be generally accessible. I'm currently testing a number of various vent flare geometry for single and double 18" enclosures optimised for very high output drivers. But this is not the point of the original post/design as the solution in this alternative Gsub design is aiming for easy of build/construction for beginners, lower cost drivers, etc with the idea in mind you just build more cabs to achieve any output goals you might have, whilst reaping the benefits of low frequency output available to you by choosing a vented enclosure. Here is a little sneaky peak of the webapp for flared vent. At this stage it must be used in conjunction with another simulation app of your choice to determine simulated frequency response expectations, but maybe one-day, with some more time on-hand I can convince my brother to develop it further to include more functionality including the simulated airvent speed, frequency response, and various types of flared ports other than square/rectangle, i.e circular. At the moment the frequency response and vent speed can be checked in another app and if it's up to say around 55m/s peak or so at tuning in WinISD a vent with flare ratio of 0.50 or greater seems to contain the "chuff" but too much flare results in less port gain bandwidth (I think).  ------------- www.instagram.com/translate.sound |
Posted By: DMorison
Date Posted: 21 June 2023 at 3:04pm
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Hi Vertx, Good looking project, thanks for sharing it. One Q I have; have you built boxes using that style of brace at the back of the vent before? I'm curious if it's big enough to start affecting the end correction WRT the air movement at the back of the vent, possibly affecting the tuning frequency? Thanks, David.
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Posted By: vertx
Date Posted: 22 June 2023 at 3:57am
Generally I always add an internal flange to a port - for instance if it's circular like below:
 and then use the largest roundover radius bit I can find for my 6-8mm router collet on the inside and outside, making it like a donut (there's a few papers on this type of thing floating around the internet), the idea being to keep port air speed down and any nasty port resonances from causing either frequency response issues or time domain issues in your midrange (this is more so important for a woofer rather than a subwoofer). Likewise, with a square or rectangle port I do not like to have it terminate without a "baffle" of sorts, or a "flange", for the same reasons as above. To be fair I haven't actually measured impedance of any of my enclosure with and without the flange to see if there is a noticeable difference in tuning as it's usually where I need it to be first or second try these days but I suspect it would have less of an effect on tuning frequency and impedance than filling the enclosure with polyfil or other internal wadding. ------------- www.instagram.com/translate.sound |
Posted By: DMorison
Date Posted: 22 June 2023 at 12:39pm
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Thanks, Lots of us are aware of the idea of flanged/flared ports, I'm sure fewer of us (myself included) have ever built & tested with them. It's good to know you're still getting predictable tuning frequencies with the flange. Cheers, David.
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Posted By: AyniSound
Date Posted: 08 May 2024 at 2:59am
| Thank you for this 2023 update! It has helped immensely. The shop I'm getting to cut was asking for cad files and we chose gsubs for their simplicity in assembly. I am just starting out down this diy audio path after 15 years of ravings haha. Do you have any recommendations for tops with these? |
Posted By: vertx
Date Posted: 08 May 2024 at 4:50am
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Sort of depends on your use case, budget, rest of the system, etc. A 12" + 1" vented enclosure would work. A 15" + 1.4" vented enclosure would work. Both pretty easy to design if you wanted to give it a go. Could also try one of Scott Hinsons MEHs, or Peter Morris 60/90d tops. Commercially something like a Nexo PS15 could work second hand. ------------- www.instagram.com/translate.sound |
Posted By: AyniSound
Date Posted: 08 May 2024 at 2:40pm
| We are trying to keep it pretty budget friendly and we're looking at x15s. Thought I would ask you since we are going to use your gsub remix haha |