Blog Forums DIY Speakers and Subwoofers Sealed ~5 cuft UM18-22 Duo – Build Thread

4 voices
17 replies
  • Author
    • #14792

      Hi All,

      Figured I’d post my build here for any who may be interested. Two sealed UM18-22 in boxes about 5 cuft. These are rectangular in order to shorten the depth a bit. Really enjoyed doing the bracing actually, took inspiration off some other builders on AVS then adapted it. Perhaps lower profile than common but super stiff. Glued and then screwed from the outside. 

      Got the principal construction all done on Saturday, cut the circle for the first baffle Sunday and then attached it Monday. Next step is to flush trim then sand flat all the joins and round over all the edges.

      When I built my Cinema 6’s I bogged all the joins which added a lot of pain to the overall build, due to insufficient hardner the first coat. A mistake that only gets made once I tell ye. But in the end the join lines are still showing with a 0.25-0.5 mm ridge, so maybe the bog just couldn’t deal with climate changes effecting the inside of the speaker.

      So for these subs I’m going to try the 50/50 glue and water mixture on all the joins and see how that goes. End goal is to not see any join lines when completed.

      Exterior dimensions are:

      700mm H

      500mm D (measured single baffle)

      510mm W


    • #14796

      This is looking very nice!  Thank you for posting it!

    • #14805

      Completed everyone’s favorite part of any build today, the sanding and roundover routing. Got caked in dust but can start sealing the joins with water and glue next. Had a big vacuum up job as my Dad has a knife forging session with a client tomorrow.

    • #14834

      The first woofer arrived today. Wow, much bigger in real life than I thought haha. Everyone seems to say that though.

      Aiming to get first coat of top coat on this weekend. Ordered 22 pillows from kmart, should be enough poly fill.

    • #14838

      @splinter Hahaha! 🤣 😆 🤣  It is so true.  I remember when I got my first 15″ subwoofer and was blown away.  The funny thing is you think, there can’t be much difference between a 12″ and a 15″ or 18″.  But holy cow it is night and day!

    • #14843

      Got the baffles fully cut out along with all the edge roundovers. 50/50 pva and water has sealed the joins very nicely.


    • #14897

      After a week spent painstakingly filling flattening then priming a ton of screw holes and joins, I finally got the first coat of top on. Looks really nice in person, most of the gloss will flatten once dried. 

      Just finalizing my woofer fixings currently. I got 50mm Allen cap bolts but they’re only threaded half way up the shaft which isn’t enough. So I might have to glue 10mm plywood pieces on the inside to pack out the tee nuts, sigh. Could also get button head wood screws but haven’t found any suitable. I’ll have to be quite careful threading the tee nuts as the UM mounting holes are a good fit for my M6 bolts without much wiggle room.

      When assembling my three Cinema 6’s I only had one tee nut which failed, had to grind off the bolt head with a Dremel.


    • #14993

      Both subs are completed and in! Did some demos last night and wow they really kick. Will post the remaining build pics this evening. My office/theatre is separate to the house by about 30 metres but could hear the intro of Blade Runner 2049 from my bedroom. Fortunately I’m on industrial land with quiet neighbours (a graveyard) so can thump without concern.

      It wasn’t until I got them on the floor off the work bench that I got a proper impression of size. 

      Still got some tweaking to do, getting a big null at 60hz so probably need to bring my rear sub forward of the corner to fix that, but will play with delays on the front sub first.

    • #14995

      @splinter sweet! I’ve been looking forward to hearing your impressions on these! Sounds like they are very impressive. 

    • #15018

      Remaining build pics.

      My 50mm Allen cap screws were only threaded to the half way point, so I had to slice down a stick of 12mm plywood with my bandsaw and glue them on the inside to pack out the mounting hole length. Worked well and there was plenty of excess thread I could use to make sure each bolt was properly threading into it’s tee nut.

      On the inside I pinched the tee nuts with a screw to mitigate risk of blow out, but install was painless in the end (better than when I did my Cinema 6’s, had to grind off one bolt head).

       I stuffed each sub with about 1.8 kg of polyester fluff, roughly 0.75lb per cuft, then stapled in some fabric strips to stop the fluff falling to the bottom, though that may happen over time regardless.

      Perfect fit. Here you can see my vibration damping feet, they’re about 30mm tall and made of really gummy rubber. Do exactly what the SVS ones do but these only cost me $30 for 8. Not much vibration in room thanks to those feet. They do make it super hard to move each sub around as the feet are so grippy.


      And here it is in the front of my messy soundstage! The speakers on the ground are my bass amp and PA foldback monitors. 

      I’ve been running the amp next to my desk while tweaking the miniDSP, once done I’ll hide all the cables away again. 2nd sub placed in the mirrored rear but it’s to disorganised back there for photos at the moment.

      I do regret not taking a photo of both subs completed next to each other haha, but each sub had final assembly next to it’s destined spot.

      Next post sound impressions and measurements.


      I will say there’s been a negative with these so far, and that’s the pressurization of my room. It’s so unbelievably easy with these to hit 100db during demos that while it hasn’t felt loud, my ears have gotten popped like you’ve been diving or descending altitude resulting with slight ache in both ears from the pressure. I’m very careful with my ears, have custom moulded musicians earplugs and the like – just had them running a bit hot for the room maybe. Also wonder if I should’ve gone with two PB-2000 pros hahahha, something ported to avoid that pressurization. 

      Apart from that these things sound awesome.

    • #15019

      Well folks, I was just going to re-take some measurements and re-do my EQ slightly. I had turned my poweramp on and was setting up the sound outputs on my PC when I heard a funny noise and turning my head low and behold was the magic smoke escaping my amp. 🙁

      Hadn’t even watched a full movie yet. 

    • #15020

      @splinter oh my! That is terrible! 

    • #15022


      As Ralphie once said: ” Oh fudge! Only I didn’t say fudge.”

      That’s one really unhappy amplifier. ☹️ If I may ask, how did you wire your voice coils?

    • #15024

      @tvor-ceasar Indeed it is not.

      I wired the red on one side to the +1 on the input, and the black on the otherside to the -1. Then I connected the remaining red and black together. Per other build threads, that should have me wired in series for a 4ohm load.

      Perhaps I just had really bad luck, but the burnout could’ve been a combination of age and not being run for a while. Worked fine for half an hour Monday, Tuesday and Wednesday. I’m going to get it to a tech, being a analogue amp I’m hoping it can be repaired. But at the very least I want to know how it failed. Could turn out to be a very expensive NX6000 but we shall see.

    • #15025

      @splinter – my condolences! Seeing spirits rise is never good.


    • #15114

      We’re back in action! 

      I received a new Behringer EP4000 earlier than expected on Monday so have been able to set everything up and get the subs running again. Initially I had them way to hot and had slight ear ache from the pressure but having balanced them properly with the mains it’s much better. So far only applied some delay to the front sub (which is slightly closer to me) but don’t have any EQ yet. 

      Here are my in room measurements across three positions including mains (crossed at 80hz).

      The response generally matches the REW room sim tool, a hump from 50hz and then a dip just below 80hz. 
      I’m not sure if I’ll really be able to flatten the response much, especially considering my main seat isn’t tooo bad…. Probably just need to knock down around 55hz a couple db. 

      Subs are sounding really good and I’m enjoying them immensely, Dune is gonna be the first big boy bass movie I watch I reckon. Hearing bass I haven’t heard before in my usual demo clips from Blade Runner 2049, Ready Player One, Fury etc.

      The Irene scene in Black Hawk Down looked very impressive, most I’ve seen these woofers move.

      At my volume levels I probably could’ve gotten away with a pair of 15″s or maybe even 3 or 4 12″ subs with a low tuning, but this is what happens when you read too much AVS! 😀

      Can’t leave a flat surface clear when storage space is at a premium.

    • #15115

      @splinter haha! So true about AVS. If you read it too long, you think you need four 21 in subs. Lol. I can only imagine how impressive that sounding. Honestly the responses look pretty good for being in room. If you wanted to cut back a little on the upper frequencies you could EQ them a little if you want. But that’s really going to be a personal preference. Some people prefer their subwoofers to be completely flat while others don’t. I typically have a fairly flat response. However I also don’t mind a hump in like the 55 Hertz range. That’s where you get that nice little punch. And it can be nice if that’s running a little hot. So you might actually really enjoy that. 

    • #15117

      @123Toid Thanks for your thoughts. Yeah I’ve decided to leave them as is for a month and get used to how they sound, as you say a midbass hump isn’t too bad especially for these drivers which can sometimes measure a bit lower on the midbass output compared to others.

      I watched Dune 2021 last night and yeah these subs are super awesome. Effortless extension and a nice amount of tactile considering the super absorbent feet I’ve got them on. I’m really starting to notice the improvements two subs bring compared to just my single PB1000 previously.

      Now all I need to do is break a little ground loop hum…..

You must be logged in to reply to this topic.

©2022 KLEO Template a premium and multipurpose theme from Seventh Queen


We're not around right now. But you can send us an email and we'll get back to you, asap.


Log in with your credentials


Forgot your details?

Create Account