Gone over the deep (bass) end? Dual sealed LMS 5400 build

What started long ago as a simple question about possibly replacing my single 15" Revel B15a sub with a more capable 18" sub to give me better sub (pun intended) 20Hz performance led me here today. Not sure whether to thank or curse those who provided all the advice and recommendations. Well personally, I will thank you all. I will let my bank account do all the cursing.

I am using 1/2" MDF glued to 1/2" Baltic Birch. I am hoping that the MDF will make the enclosure more inert while the BB will give it a nicer final finish. The panels were glued together using PL Premium as well as the joints to avoid any visual screw holes. The box will be a 21.5" cube which should yield approximately 3.4 ft^3 after bracing and driver displacement.

This will be my first attempt at building my own speaker box. Well, sub at least. If it turns out ok, I may try my luck at building a 3 way speaker. All comments, critiques welcome.

Just a note, I started the build about six months ago and have already completed one box. This is the second box which is still under construction. Well, construction is technically done. I'm just staining it now. I just decided to document the second build and wanted to wait until I was nearly done before starting the thread since I am only able to work on it sparingly while my house remodel takes precedence. I didn't want to make this a year long thread with updates every couple of weeks or so.

Enough talking. Now for the build pictures.




Applying glue and spreading it out as even as possible.



Applying pressure and clamps. Waited 48 hours to allow the glue to fully cure.



Panels were bevel cut to lesson the visibility of the seams. I'm hoping this will also provide more surface area for the glue to reduce likelihood of failure. I'm very paranoid so I also screwed the MDF to the BB from the inside. Followed it up with a coat of TiteBond wood glue over the inside of the panel to prevent the screws from backing out as well as ensuring an airtight seal. I cut a groove down the center of the inside of the panels to attach the bracing to.


Bracing cut from old 3/4" CDX plywood I had lying around from my house remodel which is still ongoing to my GF's dismay.

Sorry, not sure why the pictures are not showing up. Hopefully, I can figure it out soon.

Thanks, both for all your advice and help in my previous posts and for these kind words. I have fixed my posts and the pictures should be there now.

Front view of the side, top and bottom panels glued together with bracing installed.




Rear view of the same.

All excess glue was carefully removed from future gluing surfaces to ensure a good bond. I added a bead of PL to ALL joints on the interior of the box to ensure that the box will be airtight once completed. I also coated all interior surfaces with TiteBond for two reasons. First was because the plywood I used was a little old and was flaking on one of the surfaces so I didn't want it to come apart with the pressures it will be getting inside the box. Second was to add another layer of protection against air leaks. Did I mention I'm a bit anal AND paranoid?

I used the same panel construction for the front baffle but added an additional three plies of 1/2" MDF for a total thickness of approximately 2 1/2". I used 2" deck screws to hold it all together in addition to the glue. The driver mounting holes were pre-drilled and I opted to use 10-24 T-nuts.

I have no idea what the weight will be. My back tells me it's a lot. I'll weigh it once it's all completed.

Good eye there. Those are actually 10w7s that were supposed to go into my car. Yes, they are currently running sub duties in my HT. Once these beasts are done, I'll build new boxes and re-purpose them as MBMs. I'll start another thread on that later as I will need help with the details on that as well. I plan on using the MiniDSP to add them to my front channels and running them full range. Not sure if I'll need 2 2x4 balanced units or one 8x8 since I'll need a MiniDSP for the two LMS 5400s as well to HP them at 10Hz.

Thanks! That's what I am shooting for.


Once again, very perceptive of you. I will, indeed, be staining it to hopefully match my front speakers. If that doesn't turn out well then I will try my hand at veneering.


Will do. I have already purchased a mic and installed REW on my laptop. As soon as it's all done I'll be learning to do measurements. Not sure if my laptop's sound card is up to the task or will I need to buy an external sound card in order to make proper measurements. I plan on crossing it over somewhere in the 100Hz - 150Hz range via the MiniDSP.

Thanks. That's what I'm hoping for.

Fully assembled. Installed some spikes on the bottom and drilled the hole in the back for the Speakon connector. Cleaned up all the excess glue that was squeezed out during clamping, sanded everything down, applied wood prep for the stain then sanded again. Repeated the wood prep and sanding until the wood grain did not raise up as per the instructions.

I am now caught up on where I am currently in the process. Hopefully, I should be able to apply the stain this evening when I get home from work.


Here's a quick shot of my equipment "rack". Will need to add another amp or two. Not sure what I want/need to do yet. Currently, the QSC 5050 is powering the existing LMS on one channel. I'll run the other LMS off the second channel and see how it sounds with the MiniDSP set HP at 10Hz. If I need more power I may spring for the LG 14K clone. If that's the case then I can sell the QSC to fund a decent 3/5 channel amp for my speakers. Perhaps the Emotive XPA-3. The Behringer is currently powering the 10w7s, one per channel. The Emotiva XPA-2 is powering my Revel F52 main channels. I am currently running 9 speakers so the added 3/5 channel amp should take some load off of the receiver.

With all these amps I will need to bring in more power. I will be installing a 120A subpanel in the closet. That should make it easier to add outlets as my needs grow. I currently only have a single 20 circuit in there so I have extension cords running to the equipment now. Luckily I have a couple dedicated 20A outlet just outside the closet so the extension cords are only a few feet long each. When I first envisioned my HT I thought all I needed was a nice receiver and a single 20A dedicated circuit so that's all I ran. Who knew I would go crazy so quickly.

Thanks! I've had a few cuts go bad due to the guides and bits go out of alignment mid cut as well. Hence some of the patchwork on the circular cutout you can see if you look closely. All I have is a table saw, mitre saw and a router with circle jig. Only thing I had to buy for this project was the circle jig. The rest I have for my home remodeling project still in progress.


Yea, the closet is a work in progress too. I built a false wall to run the cables down behind it. There is a hole in the center of the wall for a door I am making. I will mount a large Keystone jack wall plate and connect them all to that then run patch cables from the jack to the equipment. The door is there to facilitate future cable replacement and adds easier. I do have a server rack, but have not had time to finish the closet. I work on things piecemeal as I have time in between the house. The closet was partially completed since I was building up the HT room and was wiring the entire house for HDMI, RG6 and Cat6 connections. Once it's all done, you won't be able to see anything but rows of Keystone jack of different connection types. The only visible wires will be the patch cable from the jacks. The cables will be neatly bundled on articulating arms that will allow me to pull the rack out safely.

The fans underneath the AVR I just put there because my Emotiva amp kept shutting off. I'm assuming it was due to overheating so I just put them there a couple days ago for testing. I think i found the culprit though. There was a loose banana plug on the amp. It wasn't contacting anything, but it did come loose probably when I was moving things around. If it doesn't shut off anymore, I can remove the fans and install them in the pro amps as they were originally purchased for.

I purchased the Dayton EMM-6 and a Behringer PS400 phantom power supply for it. Will I still need to get an external sound card or will I be able to use the internal sound card of my laptop?

Got it. Thanks. I have a spare XLR to RCA cable so I just bought an RCA to 1/8" TRS cable. Hopefully I should be all set.

First coat of stain completed. It's not nearly dark enough to match my existing speakers so I'll add additional coats as required.

Question, do stains require sanding between coats like regular paints do? The instructions make no mention of sanding.

Ok, finally got a chance to weigh the beast. Comes out to ~72lbs. Add in a few pounds for polyfill, wiring harness and a few coats of urethane and it should fall into ~75lbs.

Box is finally complete. Four coats of stain and three coats of urethane.


Front of the box with polyfill in place and secured away from the driver.






Bottom of the box with the feet installed.


Rear of the box with the Speakon connector.


Driver ready to be installed.

Rubberized foam was used to help with an airtight seal around the driver frame interface with the box. I cut off the heads of 10-24x4" bolts and screwed them in place to aid in aligning the driver and preventing the driver from crushing my fingers. Once the driver was in place, the temporary bolts were removed and the black hex cap bolts were installed to secure the driver to the box.

The final pictures of the completed box. The dual JL 10w7 were removed to make room for this box. I will colocate these centered underneath the display then move the Revel B15a to the rear behind my couch. I will then separate the 10w7s to individual boxes. I'll either make them into MBMs (if REW measurements are good) or I'll keep them as subs and place one on each side wall.









No REW measurements yet as I have no idea how to use it. Tried playing around with it briefly last night, but was not having much luck yet. All I know is that one QSC RMX 5050 running both in parallel is definitely not enough power for these things. Many decisions need to be made in terms of DSPs and additional amps from here. Some of them will depend on how well the 10w7s will work as a MBM based on REW measurements.

I wasn't too happy with the staining and urethane job I did so once I have some time, I'll be sanding them both down and restaining them. The one on the right is the most recent one I did. The one on the left was my first attempt and I used a different brand stain. They both were cherry stains, but I like the second one better.

That all depends on how far your sub is from the amp. I wouldn't go with anything below 12g. I just used spare 12g wiring I had lying around from wiring my room. I bought a 1000' spool of 12g, stranded, CL2 rated wire for dirt cheap on ebay. I use that for all my speaker connections.