Dual LMS Ultra build


Distinguished Member
I’ve gained a lot reading about various posters’ experiences with their sub builds so thought it only fair to share my recent experience with my first ever build.

Ever since I started reading the Ultimate Subwoofer Company (USC) thread back in 2013 the thought of doing something for myself fascinated me, however I only ever gave it a passing thought due to my total ineptitude when it comes to carpentry. Instead I just followed the thread with great interest, almost feeling like I travelled the journey along with both Dan & Rob. I even ended up buying one (a USC18) after demoing it against quite a few other high-end offerings, the final one being the mighty Sub2, in my house, professionally set up and using the PBK kit! I actually preferred the USC18 but that might say more about me… J

Although at the time Rob hinted that two might be better than one, (forever the salesman I thought) coming from an MX350 I felt one would be more than enough at that time. Roll on two years and I started to become tempted by the thought of adding another one! (So maybe Rob was right after all..?)

Unfortunately a conversation with Rob revealed that none were available and, having previously kept an eye on the classifieds, I was only too aware that they hardly (if ever) come up for sale. The other option was to do what I’d always fancied doing, build one for myself!

About that same time (September) Parts-Express had a clearance offer on what many feel is one of the best (if not the best) drivers around, the TC-Sounds LMS5400 Ultra found here.

Josh Ricci @ Data-Bass tested it here and when tested it handled up to 4.5kw without damage! (The “max power handling” quoted by TC Sounds is 8kw..!!)

A similar sized (100 litre) DIY LMS5400 Ultra also measured very well in these comparison figures when tested by Ilkka Rissanmen here.

Also compare the LMS Ultra here with the mighty Sub2 here.

The downside of this driver however is its price; in 2012 it was a cool $1150 – gulp! That’s a hell of a lot for a single sub driver no matter how good it is. So the clearance offer of $750 in 2015 seemed too good an opportunity to miss. I ordered two of the very last ones they had, which when landed worked out at £744 each including delivery and taxes. Still pretty pricey!

All seemed to go well at first, an email confirmed they were on their way with the motors and cone assemblies being packaged separately making a total of four packages with a combined weight of 180lbs!!! Yikes!

Worryingly before they had even left the States the tracking information showed that one of the packages (a 69lbs one, so it had to be a motor assembly) had been returned to the depot whilst in transit. It eventually followed the others but about three days behind. Unfortunately that then meant that it was now going to arrive while I was away on holiday. No problem I thought, I’ll give the shipping company a call and let them know to hang on to it for when I get back. I was assured that this would not be a problem as that would happen automatically, but nevertheless a note to that effect would be put on the package(s).

Imagine my horror when just two days into my holiday abroad I received a message on the tracking link stating that unless they were collected within 7 days (I wasn’t due to get back for another 12 days) they would be returned to the sender – all 180lbs worth!! Some frantic phone calls to my neighbour (I no longer trusted their company’s international contact department’s promises) I got him to go down to the depot and explain the situation to someone in person. A follow-up message was also sent to Parts-Express who did the same from their end. This is where the wonderful Cil Padgett from Parts-Express came in but more of that later.

Being suspicious of the fact that one of the packages had needed to go back to the depot mid-transit I made sure I had a camera with me when they finally arrived and I’m jolly glad I did, as can be clearly seen here one of the packages had burst and a pretty poor attempt made to repackage it. (These photos were to prove essential later)



As can be seen here the edge of the driver has cut right through its protective packing, the user manual (not shown here) and the outer packaging! :eek:



When unpacking that motor I noticed damage to the mouth at the centre consistent with it being dropped from some height onto a concrete or similar surface. I was also aware that striking a magnet is a pretty good way to reduce its strength!


Fearing the worst I assembled both drivers and gently ran them in free air to check for any issues. Sure enough, the driver that had sustained damage to the motor assembly could be heard making what sounded like rubbing noises consistent with the voice coil rubbing against the central part of the motor assembly.

A quick phone call to Cil @ Parts-Express and, following a request for photos of both the packaging and the motor, Cil told me not to worry, she had four more in stock and would send one out immediately free of charge. What service!!

Unfortunately my delight was short-lived. Cil got back to me saying that their stock list had been incorrect and that they didn’t now have any left after all. Disaster!! The whole point of me doing this was to have a pair of matching subs and the LMS is such a different driver to the USC18’s SP4 that I didn’t hold out much hope for successfully running two co-located as I had originally planned.

A day or two went past when I received another message from Cil. She had asked around and managed to source another motor and would be sending it out to me immediately free of charge. What a star! Once again such service! I was mightily relieved. Sure to her word a replacement motor assembly arrived within a matter of days and the project was back on track – Phew!

These drivers warrant a Perspex enclosure rather than an mdf one! :)

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Distinguished Member
Now the planning started in earnest, I had the drivers but what to build and how best to build it? I had always been impressed with the performance of the USC18 and so the obvious person to talk to was GeckoDan who designed it. Dan suggested a double-skinned enclosure comprising 25mm MDF with a 6mm outer skin to cover any screw holes and joints which would also add some additional rigidity along with internal bracing. His recommended dimensions were for an enclosure measuring 435mm (21”) cubed INCLUDING feet which would bring the total volume to about 80 litres (this driver is particularly suited to small, sealed enclosures). The enclosure used by Josh Ricci to do his testing on the Data-Bass website was a 4 cu.ft. (113 litre) sealed enclosure. I looked around the AVS website for similar builds using this driver and then consulted with our own AVF resident Guru Mattkhan. I had followed with interest his own twin UXL18 thread here.

Matt calculated the optimum enclosure size would likely be in the region of 85-90 litres to be on the safe side taking into account the need for limiting maximum cone excursion with a suitably powered amp. This apparently gave a calculated ‘Q’ of around 0.65.

This is how it actually finished up…


…0.63, so not a bad estimation.

Taking Dan’s suggestion of 80 and Matt’s maximum of 90 I decided to split the difference with an enclosure volume of 85 litres. Allowing for driver displacement, bracing volume, the 25/6mm construction and a triple baffle I calculated that as requiring an enclosure 435mm (21”) cubed WITHOUT feet. Aesthetically I liked the idea of a genuine cube better so that was decided.

Now the difficult bit, do I buy the wood and do it myself? No – that was an easy decision to make. But who do I get to do it? Various names were suggested and quotes obtained but one of those names kept coming up time and again – ‘Gordy’. His quote was also considerably below that of the others I got so I went ahead and placed the order. Two 85 litre sealed enclosures built as described above including M8 inserts for screw-in feet and all for just under £200 the pair!! Unbelievable value and just not worth doing it myself even if I could! That went some way to offsetting the high cost of the driver.

Ten days Gordy promised me and true to his word ten days later I had an email saying they were ready. As I happened to be passing I decided to save myself the £38 delivery cost and picked them up in person. First impressions on arrival at Gordy’s were that they were bigger than I had expected. Thankfully a lot of that was down to the excellent packaging that Gordy puts around them. Corrugated cardboard and several layers of bubble wrap each.



I had asked Gordy to finish them ready for painting and when I unpacked them later at home that is exactly how I found them to be. Beautifully finished, no joints visible and with nicely radiused 8mm (I didn’t want a larger radius thinking they may look strange when put together) corners, all ready for painting.


Next step was to seal the insides – for this I used Rustins MDF sealant. Not cheap but it seemed to get good feedback.


Next was the question of what and how much damping to apply to the inside? I followed the advice given in this link Cabinet-damping and ordered some good quality felt and damping material. Unfortunately something went wrong with my estimate for the felt and enough arrived to allow me to carpet one of the rooms in my house!



This is the damping material I used, 4 packs per enclosure loosely draped throughout.

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Distinguished Member
Now the question was how to finish them? My original intention had been to get a friend to spray them satin black for me (I didn’t like the idea of gloss due to possible reflections) however I then happened to see first-hand Markymiles’ subs painted with TuffCab. I had previously seen various build threads where TuffCab or similar was used but with mixed results and was never totally convinced, however on seeing Mark’s subs in the flesh I changed my mind. I obtained a couple of samples from Blue Aran, the makers of TuffCab and much preferred the ‘Pro’ version. It was less of a gloss finish than the regular TuffCab paint and appeared similar to the satin finish that I had originally planned for albeit with a more textured surface which I quite liked. It also didn’t require any undercoat making things that much simpler.

I followed Blue Aran’s link on how to apply it. Clingfilm around the rollers between coats cut down on the need to keep washing or replacing them and in the end they turned out even better than I had hoped for. After just the first coat they looked pretty darn good already…


…but after several more coats it looked as close to a professional finish as I could ever have hoped for.



It’s certainly not cheap at £36 for a 2.5kg tin delivered, however that proved to be more than enough for four or five coats to both enclosures with some left over for the inevitable touching up later.

Wiring connections were accomplished via sealed Speakon sockets, 90 degree connectors and Van Damme 2.5mm Blue Series Studio Twin Axial cable.

I took great care when wiring the drivers’ twin voice coils to make sure that I ended up with 4 Ohms resistance from the dual voice coils rather than 1 Ohm(!), reading the wiring diagram several times to make sure I got it right. Then the final step – putting those 86lb drivers into the cut outs…!

I had deliberately not given ‘Gordy’ a dimension for the driver cut-out. He had a lot of experience with making sub enclosures and I felt that if I gave him a specific dimension he would do exactly that, whereas if I gave him the driver’s dimensions he could decide on just how big to make the cut-out. I’m so glad I did it that way as you will see.

Taking advice from other build threads I used the thickest cable ties that would fit in the holes in order to lift each driver and with the wiring in place I gently lowered the first driver – problem! The rubber seal that goes around the edge of the driver rode up on the edge of the enclosure as it went in and it was now firmly jammed in place…! Pulling up on the cable tie then caused one of them to snap! What to do now? This thing was stuck fast! After some careful thought, in order to avoid damaging the cone and its surround I up-ended the enclosure onto part of the packaging that the driver had initially come with, hoping that the massive weight of the driver would push it out. It took three attempts at rocking it to and fro to get it to release but in the end it did. Phew!

Two more unsuccessful attempts to fit it followed, but this time by not allowing the driver to fully seat it was comparatively easy to remove again with the cable ties, but once again each time the rubber seal rode up at the edge.

What to do now? I didn’t want to have to enlarge the size of the cut-out and undoubtedly ruin ‘Gordy’s’ superb handiwork so I decided to use a little Vaseline on both the edge of the rubber seal and the opening itself. SUCCESS! It slipped in beautifully and ended up a perfect fit. Phew!


Using the same method for the second driver made it a doddle, it slipped in beautifully. The drivers were then firmly fixed in place with wood screws – job done!


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Distinguished Member
One of the reasons to go for two separate subs rather than a twin sub setup was being able to move them easily. Using two 86lb drivers in the one large enclosure would have meant it would have been impossible to move them without help and although the REW Room Sim suggests co-locating two subs under my screen is the best option for me, I wanted to have the flexibility to experiment later should I so wish. It also gives me the ability to try out various orientations.

Rearward Firing


Side Firing


Downward Firing


…and Forward Firing


Initially I had planned to go DF as that had proved to work best with the USC18, hence having the inserts put in for the feet, however these drivers looked so goddam gorgeous placed FF I was having second thoughts purely on aesthetic grounds! I ran various tests to see what the measured difference was. As can be seen here with non-EQ’d runs, not a lot that can be measured, but the FF orientation (black on the graph) seems to hold up just a fraction better at both the bottom and top ends albeit with a distinct room null coming into play at just under 80hz that the other orientations didn’t seem to suffer from so much. When listening I felt I could detect a slight difference between the orientations and whilst the DF initially seemed to have a more visceral ‘feel’ at lower levels the FF seemed to have more detail and ‘punch’, particularly when turned up. These may of course have just been my expectations manifesting themselves here of course.


Nearfield produced this..


My experience of DF with the USC18 had been that of increased tactile ‘feel' that firing into a suspended floor gave me but now, when listening to two LMS drivers firing into the floor at ‘realistic’ levels, that tactile ‘feel’ was becoming something of a distraction! Even using the comparatively under-powered (for these drivers that is) iNuke6000 some sort of plinth would be necessary to reduce this. The output these drivers were capable of and the extra ‘slam’ they have over the single SP4 was such that even when placed FF they were now pressurising the room to such an extent anyway that I was getting the same tactile feel from the floor that I was previously getting from the USC18 firing downwards. So for the time being at least, they will remain FF, that is until I get bored looking at those gorgeous drivers. (which could be a very long while…)

You may ask, what about the WAF? Well, I’m very lucky there, when asked for her opinion she just said “I don’t notice them…” :eek:


Distinguished Member
So, now for some calibration. First up I tried a calibration using just Dirac without any other pre-EQ in place. Dirac calculated that the sub would be flat from 20hz to 1Khz, however a check with REW revealed a steady decline from 80hz and below and a steep drop below 20hz that I had noted previously with Dirac. It was a healthy reminder that graphs produced by the 88A are just estimates, it only actually measures before a calibration, not afterwards so it’s always a good idea to check with REW to see what it’s actually done.


Next I modified the Dirac file to 10hz which then pushed the drop down to 12hz.



…and fine-tuned it with the 2X4 to get this…


Finally I did what I should have done from the start and what I had previously done with the USC18. I pre-EQ’d the subs with the 2X4 (much in the way that a manufacturer would normally do with a commercial sub using its on-board amplification) and followed this with the modified-to-10hz Dirac calibration and some further fine-tuning with the 2X4 which finally got me to this (sub only)…


What surprised me was that as the FR cut-off dropped from 18hz to 12hz then finally to 8hz, even films that are meant to have little in the way of output below 20-30hz (Oblivion, Prometheus etc.) sounded (or was that ‘felt’?) noticeably better the lower the FR got which was surprising.

Where from here? Well amplification sufficient to really stretch these drivers is next on the list. I had a SpeakerPower SP2-12000 for a short while and the difference was definitely noticeable, adjectives such as ‘cleaner’, more ‘punch’ and ‘slam’ spring to mind. It became even more noticeable when going back to the iNuke afterwards, it sounded slightly ‘woolly’ in comparison although that is relative! Even with the iNuke in place these drivers still sound pretty amazing.

So, for anyone sitting on the fence and wondering whether or not to take the plunge and go D.I.Y., I’d say an emphatic DO IT! Despite the initial problems with getting the drivers delivered, it’s much simpler than I’d ever imagined given that most of the difficult work was actually done by Gordy! I can’t sing his praises highly enough, his workmanship was superb and his prices rock bottom.

Although it sounds like a cliché I’m listening to all my favourite films again and hearing/feeling them like I’ve never quite heard/felt them before. Wonderful – and with that added feeling of satisfaction that only comes from knowing you Did It Yourself – along of course with all the help that I got from this community. A big thank you to all those that helped with advice, threads etc. and special thanks to: [email protected], @GeckoDan, @mattkhan, @markymiles and of course ‘Gordy’!

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Well-known Member
Amazing Job.

The 80Hz null is due to the crossover, or the subs placing?
Isnt possible to put each sub in a corner?


Distinguished Member
Partly crossover and partly a room null, but as you can see from the un-eq'd traces it's most noticeable with the FF orientation. However it's quite narrow so isn't really noticeable when listening. Needs a bit more fine-tuning... :)


Distinguished Member
Congratulations :thumbsup::thumbsup:

Is this the first "after" build thread?


Well-known Member
Hi Ringnut fantastic work you done there, those subs look amazing and i bet sound amazing too.

Are you using an off board Dirac device? and how much where those drivers? if you don't mind me asking :)

Part 1) LOL just seen your sig ;) MiniDSP, Part 2) ah Jesus maybe i should read the whole thing first before commenting, So you can't buy these drivers any more :(
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Active Member
Nice subs Ringnut but just out of interest, what do you think of the XTZ cinema speakers?


Well-known Member
Hi Ringnut fantastic work you done there, those subs look amazing and i bet sound amazing too.

Are you using an off board Dirac device? and how much where those drivers? if you don't mind me asking :)

Part 1) LOL just seen your sig ;) MiniDSP, Part 2) ah Jesus maybe i should read the whole thing first before commenting, So you can't buy these drivers any more :(

There is another pair sitting in their card board boxes currently in storage on uk soil.......................;)


Well-known Member
Some great info in this thread. I'll come back to it when building my dual subs. Can you go over how you painted them? I also have the Tuff Cab Pro. Did you give it a coat and before it dried go over it again to smooth it out or anything?


Distinguished Member
Thanks. Sure, I'm no expert when it comes to painting so I followed the link carefully. I started by painting the inside edges of the cut out using a normal brush then using gloss paint rollers I started with a small 4" roller on the cut-out side, let that dry for about 3 hours, then did the other five sides one after the other with a larger 9" roller.

Start with a liberal coating first then roll it out getting lighter and lighter with each roll until you have the effect you're looking for. Don't do it in a warm room, the paint will dry too quickly, mid teens should do and use cling film to cover the rollers between coats. Once touch dry, apply the next coat. That's what I found worked best for me.

Enjoying reading your build threads BTW. :smashin:


Well-known Member
I'm thinking it might be worth getting someone else to build my boxes. Is Gordy on these forums or do you contact through eBay?


Well-known Member
Awesome thread and a great build :thumbsup:

That final graph is really excellent, I dream about getting that flat! :laugh:

Now you need to run through all the top-rated films on the data-bass thread and let us have your thoughts on what they are like with such a flat and extended response ;) lol


Distinguished Member
Great job enjoy!! I concur with the more powerful better amp scenario.

Just heard that an SP2-12000 is set to arrive on Wednesday :smashin: so with 3.4kw per channel @ 4 ohms that should really make these drivers sing!

The SP1-6000 (of which the SP2-12000 comprises two) is meant to be able to sustain 6kw @ 2ohms for 4 seconds Scribd :eek: which few others can match. However its main advantage for me, given that it will be in the same room and close to the MLP, is that it remains practically silent. The fans only turn on when things get hot, which IME is rarely. Certainly when using it previously I never once heard it, even in the quietest passages.
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Distinguished Member
Thanks for the link. Yes, I had seen that previously and was partly what convinced me to go with it, plus of course if SpeakerPower is good enough for @mattkhan :smashin:

Once we'd checked the final 'Q' of the enclosures (thanks to Matt once again) and with the SP2-12000 in mind he made this assessment of the power requirements needed to make the most of the LMS Ultras in these enclosures - Xmax being 33mm or 38mm depending on what measure you use and Xmech being 44mm.

"With 110V (which is what a single channel of the speakerpower can deliver), you will cross 33mm at 20Hz and 38mm at 10Hz. You only get to 44mm at 1.5Hz :p I think this suggests that signal chain rolloff will keep you safe :)

The speakerpower is a good fit for getting the max out of this driver in that size box. A plan that turned out nicely!

This gives you 103dB at 20Hz at 3m (I guessed how far away you sit) which turns into 109dB with 2 of them. If we assume room gain adds 12dB/octave from here to counteract the rolloff of the sub itself then you could assume you have max output of ~110dB down to 6-7Hz. It could easily be a few dB more or less depending on room gain but it's hard to work out an accurate figure for that."

I just need to be a bit careful running excerpts like the start of EOT at reference! :devil:
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Remembered (1961-2016)
It seems to fit the bill very well!! How large is your room? Is it something like 18' x 15' or there about as controlling the ringing in a smaller room at high volume levels would be a concern , so room treatment is a must.................................If its in a dedicated cinema room then not too much of an issue.

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