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twosteps View Drop Down
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    Posted: 30 January 2026 at 2:22am
i've come up on 6x 18lw1400 drivers and id like to make some reflex cabs for em. 

the kit18 seems like the right choice considering it was designed around the driver. however it seems like the cab volume is a bit low, which is probly contributing to the 35hz fall off and i'd like a bit more low end extension. 

i'm wondering if i extend the baffle 68mm to the face of the cab instead of being recessed, should i keep the same port length (moving it up with the baffle)? or should i extend the port by 68mm so the port begins in the same place in the cab (but is longer)? 

i've never tried to modify a plan, and cant seem to get winisd to work, so i'm unsure how it'd effect the performance/tuning. some insight would be greatly appreciated. 

also, i'm not married to the kit18, so if theres other plans available that'd be a good/better fit for the 18lw1400 that can meet my midtops at 100/120hz, please give em a shout =D

thanks
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Bremen_99 View Drop Down
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What about this one? I think its the updated version for HP drivers 

https://www.eighteensound.it/media/W1siZiIsIjIwMjMvMDcvMTcvMTRfMDVfNTlfMzA3XzE4U3ViX3YxXzEucGRmIl1d

I'm heavily considering building 4 of them. 
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twosteps View Drop Down
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Points: 38 		Post Options Post Options   Thanks (0) Thanks(0)   Quote twosteps Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2026 at 7:31am
Originally posted by Bremen_99 Bremen_99 wrote:

What about this one? I think its the updated version for HP drivers 

https://www.eighteensound.it/media/W1siZiIsIjIwMjMvMDcvMTcvMTRfMDVfNTlfMzA3XzE4U3ViX3YxXzEucGRmIl1d

I'm heavily considering building 4 of them. 

i’ve checked that out but like the cab shape of the kit18 and it also seems like a simpler build than this newer design. i currently have 4 of the drivers in eaw sb180’s which have very similar dimensions to the design you posted. seeking something a bit deeper for stacking purposes. 
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Originally posted by twosteps twosteps wrote:

the kit18 seems like the right choice considering it was designed around the driver. however it seems like the cab volume is a bit low, which is probly contributing to the 35hz fall off and i'd like a bit more low end extension. 

i'm wondering if i extend the baffle 68mm to the face of the cab instead of being recessed, should i keep the same port length (moving it up with the baffle)? or should i extend the port by 68mm so the port begins in the same place in the cab (but is longer)?

Hi there,
The 35Hz corner is determined by the box volume, port tuning and driver TS parameters all interacting, so while adjusting box size will give you a slightly different response, it might not be all you want.

Adding 68mm cabinet depth adds ~22 litres to the internal volume, which will only make about 1dB of difference in the half-octave around tuning (yellow curve vs green in the below image. To make a full 3dB difference you would need to increase the cab to around 230l net internal, nearly 60% bigger than the original box (red curve).



The one good thing about increasing the internal volume of a cab is that the required port length for a given tuning actually decreases, so for the 167l option here you would reduce the total vent length to about 260mm - which in turn reduces the total space it takes up in the box so you'd actually end up with about 172l rather than the 167. That 5l difference would only make an extra 0.2dB difference to the response though, so I haven't bothered putting it on the graph.

HTH,
David.



Edited by DMorison - 01 February 2026 at 3:10pm
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cravings View Drop Down
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Points: 7507 		Post Options Post Options   Thanks (0) Thanks(0)   Quote cravings Quote  Post ReplyReply Direct Link To This Post Posted: 01 February 2026 at 6:45pm
Don't remember exactly off top of my head, but the plan has a suggested eq bum of something like 6db 12db per octave at 25hz
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Points: 38 		Post Options Post Options   Thanks (0) Thanks(0)   Quote twosteps Quote  Post ReplyReply Direct Link To This Post Posted: 02 February 2026 at 6:08pm
Originally posted by DMorison DMorison wrote:

Originally posted by twosteps twosteps wrote:

the kit18 seems like the right choice considering it was designed around the driver. however it seems like the cab volume is a bit low, which is probly contributing to the 35hz fall off and i'd like a bit more low end extension. 

i'm wondering if i extend the baffle 68mm to the face of the cab instead of being recessed, should i keep the same port length (moving it up with the baffle)? or should i extend the port by 68mm so the port begins in the same place in the cab (but is longer)?

Hi there,
The 35Hz corner is determined by the box volume, port tuning and driver TS parameters all interacting, so while adjusting box size will give you a slightly different response, it might not be all you want.

Adding 68mm cabinet depth adds ~22 litres to the internal volume, which will only make about 1dB of difference in the half-octave around tuning (yellow curve vs green in the below image. To make a full 3dB difference you would need to increase the cab to around 230l net internal, nearly 60% bigger than the original box (red curve).



The one good thing about increasing the internal volume of a cab is that the required port length for a given tuning actually decreases, so for the 167l option here you would reduce the total vent length to about 260mm - which in turn reduces the total space it takes up in the box so you'd actually end up with about 172l rather than the 167. That 5l difference would only make an extra 0.2dB difference to the response though, so I haven't bothered putting it on the graph.

HTH,
David.

thanks! this is really helpful i appreciate you taking the time. im just trying to figure out how to get better low end response without a +6db boost at 30hz. i like the idea of using a box designed for the driver but im not sure if i want to push the drivers that hard. 

maybe something like the sub18 would be better suited for the low end response im after, but i imagine that'd likely benefit from modification to be better suited for the 18lw1400?
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I was considering oversizing the 18sub slightly to fit my drivers, to get something more like 230 net liters instead of 200, but with the lower vas, higher qts, and the need for acoustic resistance in lots of modern drivers, I feel like just making them "bigger" trades a lot of 40hz and up, probably more overall spl lost than gained, so as usual extension for spl, but I don't think a bigger reflex depending on your driver is just better because they need acoustic resistance. Maybe I'm wrong. Also the drivers im looking at in the 18sub (the updated, not the kit) have slightly higher fs so that could be why a larger box wouldn't work as well for me. The 18lw1400 is listed on the compatible drivers list of the plan I posted, I think its about 200l net 
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Originally posted by Bremen_99 Bremen_99 wrote:

I was considering oversizing the 18sub slightly to fit my drivers, to get something more like 230 net liters instead of 200, but with the lower vas, higher qts, and the need for acoustic resistance in lots of modern drivers, I feel like just making them "bigger" trades a lot of 40hz and up, probably more overall spl lost than gained, so as usual extension for spl, but I don't think a bigger reflex depending on your driver is just better because they need acoustic resistance. Maybe I'm wrong. Also the drivers im looking at in the 18sub (the updated, not the kit) have slightly higher fs so that could be why a larger box wouldn't work as well for me. The 18lw1400 is listed on the compatible drivers list of the plan I posted, I think its about 200l net 

yeah i did some more reading since posting this thread and found a few discussions mentioning how this driver sounds best in smaller boxes because of the improved dampening. and maybe this allows for it to be pushed harder safely (thinking about the +6db at 30hz in the kit18 plan which just seems wild to me lol).
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Points: 68 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Bremen_99 Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2026 at 5:55pm
well the 18lw1400 is not a high xmax driver, but its suggested enclosure size (https://www.eighteensound.it/en/products/lf-driver/18-0/8/18LW1400) is 7.77cuft, larger even than the 18sub, (which is 7cuft) I honestly do not think the project 18 that is even much smaller is a good fit, you want the acoustic loading/resistance to match your driver and its vas, so if you do +6db at 30hz you will reach xmax way quicker than  you think you will, and miss out on the upper response of the driver trying to get more sub tuning db. You won't be able to push it harder safely in a box that far under the recommended size, which is why I posted the updated version for higher power/more modern drivers. If you are chasing more 30hz you will lose a lot in the spl and higher (40-70) bass, especially in a smaller box, from my understanding. 
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Points: 38 		Post Options Post Options   Thanks (0) Thanks(0)   Quote twosteps Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2026 at 9:29pm
Originally posted by Bremen_99 Bremen_99 wrote:

well the 18lw1400 is not a high xmax driver, but its suggested enclosure size (https://www.eighteensound.it/en/products/lf-driver/18-0/8/18LW1400) is 7.77cuft, larger even than the 18sub, (which is 7cuft) I honestly do not think the project 18 that is even much smaller is a good fit, you want the acoustic loading/resistance to match your driver and its vas, so if you do +6db at 30hz you will reach xmax way quicker than  you think you will, and miss out on the upper response of the driver trying to get more sub tuning db. You won't be able to push it harder safely in a box that far under the recommended size, which is why I posted the updated version for higher power/more modern drivers. If you are chasing more 30hz you will lose a lot in the spl and higher (40-70) bass, especially in a smaller box, from my understanding. 

oh yeah if i do build these kit18's i'd likely be doing +3db at 30hz, im balling on a budget and cant afford to replace drivers =D

right now i have 4 of the drivers in eaw sb180's (~200l volume i think) and they sound pretty dang good.
however i've been looking for 2 more sb180 cabs to house these last 2 drivers, with zero luck. so its looking like im gonna have to build some cabs if i want to use all 6 drivers. 

now im trying to figure out the best plan to run em 30-100 for dnb/jungle/dubstep (lots of heavy sub material) since it seems like the kit18 may not be ideal for this application. 
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the 18sub is ideal for 33-100, that's exactly why I'm considering it for my prospective build with B&C drivers. For continuity sake you could just build 2 more sb180 clone cabs, to be honest that is what I would do since you already have so many, no reason to taint the group delay or phase with a slightly differently tuned and sized cab. Definitely a better idea than building two worse mismatched kit18's. I would only build entirely new cabs for all 6 subs if you are switching to a different design, FLH or BP etc, otherwise build 2 clone sb180's. My opinion. 

Edited by Bremen_99 - 03 February 2026 at 11:18pm
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just do more sb180s then?
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