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Owen's DIYSG HTM-12 build

32K views 39 replies 4 participants last post by  Owen Bartley 
#1 ·
With our basement renovation finally making some progress, and the design of the theatre taking shape, it was finally time to decide what speakers to use in the new space. Since I will be putting them behind the AT screen, I knew I wanted three identical speakers up front. I have been planning this project for so long that I've had a lot of different speakers in mind over the years (yes, years)... NatP, Modula MTM, Dayton RS-P WWMTM, Mini Statement... I liked aspects of all of those (and many other) options, but none of them really firmly established themselves as a clear, definitive choice. At least until I discovered DIY Sound Group.

Reading about the SEOS speakers, I knew that this was going to be it. The question was "what flavour of SEOS?" I started out thinking the Fusion 6 would be the one, then moved on to basically consider nearly every model in the Fusion and Cinema lines. Some were easy to eliminate due to their large size. Then I learned that the larger SEOS horns were generally more desirable, and started to focus on that, which led me to the 88 Special. This speaker was shallow, wall mountable, praised for its clarity and output, and it used the big SEOS-15 waveguide. It seemed perfect, and I was just waiting until we got closer to starting the full project before ordering. And then I was pointed to the HTM line, which made me start all over again.

The things that I was looking for in the front stage were: first and foremost, clear and clean dialogue, good output to match a pair of 18" subs, and a depth that would fit behind a shallow 1' false wall in the screen area. The reviews of the 88 Special suggested that it was fantastic for dialogue, and speaking with Erich about my goals and needs reassured me that they would shine in my setup. Once I had checked out the HTM line a bit, which wasn't easy because they were so new that there was barely any information out on them, I became convinced that they might be a little bit better than the 88 Special, and Erich assured me that I would be happy either way. In the end I decided that I have room for the HTM-12, so I'd go for the big woofer and SEOS-15 to make sure I didn't leave any performance on the table. Once I discovered a review of a newly built HTM-10 build online, I was 100% convinced that I was making the right choice. If the 10s impressed that much, the 12s must be spectacular.

I have received my kits, and I'll try to move these along reasonably quickly, but with a 1 year old and a 3 year old at home, there isn't much time for projects. I'm very excited about these, so I'll do my best to put in build time whenever I can, and I ordered the flat packs with them so that will help immensely.

Erich and Matt have been extremely patient and helpful throughout my search, and always took time to answer my questions quickly and thoroughly. If the speakers end up half as good as the customer service experience has been, I'm in for a treat. Thanks again guys.

Here are a few pics... the 5 boxes (I also ordered eight Volt-6 speakers for surround and ceiling duty) going into my car for the drive across the border, Erich's legendary packing, and a baby for scale of the HTM-12 baffle.
 

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#3 ·
Thanks Prof! It's slow going chipping away each night... but I'll just call it a "relaxing pace".

Last night I got some good crossover work in, and have most of the components glued down to the boards. I think everything looks right (minus the missing 2 caps per board), but I want to look at it with fresh eyes before I start to solder. All these little jobs really add up to take a lot of time! I still have to zip tie the larger components, then solder, and then the boards will basically be done, and I can move on to cabinet assembly.

If anyone sees a major red flag, let me know before it's too late!
 

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#6 ·
Thanks Tonto! No pics today, I didn't get enough done!

Prof, I kind of know what you mean. Working with the printed boards from mtg90 was a downright pleasure. I haven't soldered them yet, but it looks like it will be a snap.

Baby steps last night and a little bit of progress. I got the bracing glued into 2 of the 3 speakers, but had to stop before I got to the third. Hopefully I'll get that together tonight, even though we have kids activities and then I have an appointment later in the evening. Then I hope to get the top/bottom/sides on all the enclosures over the weekend.
 
#8 ·
A little bit of weekend progress. With pics for Tonto! :)

The cabinets are now fully assembled, except for the front baffles. It was a bit of a grind, starting with tops and bottoms, and doing one speaker at a time due to lack of a decent workspace, and lack of clamps. I know I have more, but I have to collect some I had loaned out. It can't be said enough... you can NEVER have too many clamps. So, first was tops and bottoms for 1, 2, 3. Then on Sunday I managed to get the sides on all of them too.

I don't think my method or technique was too bad, but they all have a bit of a lip here and there, with some panel overlap. Nothing serious, and I think I have good solid glue joints, so it will just mean a little bit of cleanup sanding before the baffle goes on, and then some good filling and sanding before finishing, as usual.

You can see in a couple of the pics that I reversed a clamp to use as a spreader across the vertical centerline of the enclosure. I might have clamped a bit too hard when doing the tops and bottoms, which forced those panels a bit out of true. Just enough that it would make more work in the finishing stage, so I applied a tiny bit of spreading pressure on the centre brace and it came back in line nicely with the sides when I got them all clamped up.

I ran out of glue pretty early on, so I made a quick run out to Canadian Tire and thought I'd give this stuff a try. Elmer's Pro Bond Max. It goes on nice, and has a good amount of working time before it starts to set. Which is handy when I'm doing 2 panels at a time before I can tighten all the clamps. It looks/feels almost a bit like a glue with some MDF particles suspended in it. Not gritty at all, but a bit different than the Titebond / Gorilla / Straight Elmer's wood glue I had used before. So far I like it.

So next up for this week is to sand the edges flat for the bezel, finish crossovers, finalize a mounting location, and then I guess wait for my eBay binding posts. I forgot to add them to my order from Erich. I'm proud of myself for at least putting a little time in just about every day so far. Gotta keep up the momentum.
 

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#10 ·
Thanks Prof! The cabinets will be super plain as far as finish goes. They'll be behind the screen so they don't have to be beautiful. I have a new gallon of flat black paint ready to go after filling, sanding, and priming. I'm not going to spend a ton of time on them, but I do want to get a good clean finish at least for the paint. Here's a link to a pic of the binding posts from the eBay seller. I hope they'll work out OK.



More small steps done. All I had time to do lately was clean up the boxes with a little sanding. The edges on the face of the enclosure where the front baffle will attach were off by little bits on most of the joints, so I wanted to get a nice flat surface for gluing. I couldn't find my random orbital, so I went old school.

I tried to be careful when taking the lips off not to round the edges over too much but there was definitely a little bit of that in areas where I had to do heavy sanding, which shows in the closeup. While I was at it, I also cleaned up the outside corners and edges so there will be less filler involved in the final product. I started in the garage which was a terrible idea, before I moved out to my "mobile sanding base" a.k.a. the folding work table on the sidewalk.
 

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#12 ·
I have now completed the crossovers, except for the wiring which I'll do tonight. I won't show pics of my soldering, because it started out pretty ugly, and only got marginally better by the end. I'm fairly confident that it will work, but it is far from pretty. I was used to doing much smaller connections, and was having trouble getting the little solder mounds to keep from "collapsing" in on themselves around the stems. By the end I mostly figured out the technique, but it was pretty fiddly.

I couldn't mount the boards yet, because I couldn't find my small zip ties, but I think I have a good location for them. I started to cut and lay out the Ultratouch, which is pretty nice to work with. It turns out one bag is just about the exact right amount for an HTM-12 cabinet, so the 3 bags I have will be perfect. I plan to mount the crossovers on the side of the enclosure, and basically line the inner cabinet with the insulation. I think I remember reading that it was OK to run a layer of it right over the crossover, but I wanted to make sure. I played around a bit with the lining, and have a few options below. the last piece will either go up and over the crossover and line the full side, (pretend the crossover is mounted in that last pic) or along the bottom under the ports and just up to the crossover on the side. I wasn't sure if the lining on the bottom might help to minimize any resonance in the ports, since it would be fairly snug under them.

Hopefully tonight I'll be able to...
- install the crossover wires
- do a quick sound check on each board
- mount the boards
- line all 3 cabinets
- glue and clamp the front baffles

I'm eager to start finishing these, and am still on pace for having them done by Christmas if I don't run into many delays. I did a test fit of the waveguide last night, and it is TIGHT. I'll have to sand a little bit of material out of the inner recessed area before finishing.

** Shoot, I just remembered that I still have to wait for the binding posts to arrive. I guess I could go ahead with finishing and sort of wing it when they arrive... we'll see. **
 

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#13 ·
Well, turns out my list above was a bit ambitious. Lol. That night I got the zip ties done on all boards, and I think I did the wires on one. Last night I was able to buckle down a bit more, and get a few other things checked off the list.

I added all wires. I would have preferred to use nice black/red wires, but this was what I had on hand. Still easy to identify. Then it was time to get excited, because I could hook up the guts and give them a first test listen. At first I just connected everything on the bench. (NOTE: please ignore my current disaster zone work area. This is in the basement which we're currently trying to empty out to get ready for construction. Which means there's junk everywhere as we sort through it all.) The first pic shows that setup, and everything seemed to work properly but it was pretty tough to get an idea of the actual sound. Free air woofers definitely leave some to be desired, so I figured I'd pop a baffle on and test them in place. They definitely sounded better, but I wasn't able to go too loud since it was coming up on 11:00 and everyone else was in bed.

Once I was sure everything sounded right, I did a full layout with the ultratouch, found the best spot for the crossover, taking into consideration the ports and the binding posts I'll need to add, and then marked for pre-drilling. I decided to use Kreg pocket hole screws to mount the boards, because of the large flat head. But I only had 1 1/4" screws, which would have poked out the side of the box, so I added a rubber washer on top of the board and standoffs, which I think will work great. I didn't have time to cut and staple all the insulation in the other boxes, but all crossovers are mounted, and I'm ready to finish that up tonight.

I'm pretty sure I can attach the front baffles after that, and manage the binding post installation through the woofer cutout. I think they're pretty standard binding posts, but I haven't installed anything but terminal cups before. With the ones from my pic a few posts back is there any reason not to go ahead and close up the fronts? I'll still have a good amount of room to work, and I'll be that much closer to filling, sanding, priming, and painting.
 

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#15 ·
Thanks Prof, I'm interested to see what the sound is like for me too. I've had a pair of Paradigm towers for over 10 years now tht I'm very used to, and these will sound very different, I can tell just from the test.

The HTM-12 crosses over from the Eminence Deltalite 12" woofer to the Denovo DNA-325 compression driver at 1,400Hz. It's higher than the 88 Specials I was originally looking at (which cross at 950Hz!), which was said to be a big asset for dialogue. I don't know much about crossover design, so I'm trusting the experts on this one, and I'm sure they'll also shine in that application.
 
#16 ·
We're picking up steam now! Last night I continued with insulation which went very smoothly. I have to say again how nice the Ultratouch is to work with, it made things easy. So, all 3 cabinets lined, with the rear panel on the crossover side just tacked into place at one end. This way I can flip it up to do the binding posts and then pop a few more staples in when that's done.

I figured I might as well go ahead with the baffles, even though my Christmas deadline is basically impossible now. That's OK, it was just a "loose" deadline. Since I had 7 clamps on hand at the moment, it meant I could only do one at a time, so I put one together last night, and then snuck down this morning before showering and heading to work to glue up a second while everyone else was asleep. 2 of 3 cabinets are done, and I'll get the 3rd baffle glued early this afternoon, since I'm in for a half day.

They will all need a preliminary sanding, then a cleanup and treatment with some filler, which I hope to tackle tomorrow. Things are going to be tight because we're having people over Christmas Eve, Christmas Day, and Boxing Day, and I will have a lot of household work and prep to help out with too. I'll try to get a little done each day, and I think it will be reasonable to say I can have these all finished up by New Year's Day.
 

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#17 ·
Let's just ignore all my previous schedules and timelines, OK? Turns out getting work done over the holidays was pretty much impossible, so I just got a chance to do a little bit last night. I got a nice little cordless sander for Christmas, which was great because I have no idea where my old corded one was. What was less great was the fact that the 2 batteries I had were maybe half charged at best, so I had just enough juice to get all the edges done on one speaker before they both gave up on me. It could have been worse.

The edges on this one are all nice and clean now, so I slopped some filler along the joints. This stuff isn't very happy working out in the cold garage, but I made do and got a coat all around. Between the pallet of flooring for the basement and the pile of Christmas recycling that keeps growing, there isn't much room to work in my little single car these days, but it will be my new base of operations to get the speakers finished.

I'll go at it again tonight hopefully, with 2 fully charged batteries and see if I can get both remaining cabinets sanded and filled. We'll see how the batteries last, I did read some comments that the sander chews through them quickly.
 

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#19 ·
I'm chipping away, Prof... one little bit at a time!

Last night was sanding and filling part 2 (of 3). Got a little more done, but even with 2 full batteries I didn't get completely finished. I was able to get most of the baffle lip off, and I even went at it with the sandpaper to get the rest of it close after my batteries died. Now I just need to give the 3rd speaker a final once-over, and some light fill.

I should be good to at least get them primed this weekend. We have zero New Years Eve plans, and we're keeping it that way. If things go smoothly I might even get to put a coat of paint on. I'll probably do 1 coat of primer and 2 coats of paint and call them done. Still waiting on binding posts, but those can be added after the finish dries.
 

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#20 · (Edited)
Happy New Year, everyone!

Basically a "nothing" update today, because I took a break from building over the holiday and either spent time with the boys, or relaxing with my wife instead of freezing my fingers off in the garage. I finished filling and sanding, and it seems like the enclosures came out pretty clean. I had a few small low spots filled in (from over- or under-sanding) and most of the filler left is just sitting in the little pits where I didn't have 100% fill in the glue joints at the outside edge. They might look a bit ugly still, but they're generally baby's-butt smooth. And not caked with filler either, which I like.

I did manage to get a coat of primer on all 3 enclosures, but didn't move on to either a second coat or actual paint. I think I'll skip the 2nd coat of primer and just go straight to paint, and do either 2 or 3 coats if required.

I'll get back to work this week and start painting for real. I'm thinking a small foam roller to minimize texture, we'll see how that works out. Still waiting on binding posts, so I don't feel like I have to push. (also, I don't really have anywhere to put these till the theatre is built in like a year... but you know, priorities.)
 

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#21 ·
Owen,

I thought you should know there are people out there following your thread with great excitement. I'm in a similar position as yourself, building a dedicated home theater in a house I just bought. Like yours, my home theater probably wont be done for about another year or so, but I'm already looking into my speaker options. I want to upgrade to ATMOS and since I love building speakers, I thought I'd do that rather than buy. I've been looking for the perfect DIY option and ran across the HTM-12's. I'm very used to standard home theater Hi-Fi. I have an older, Kenwood THX 5.1 system (LS-X1F LCR's and a matching pair of SW-X1 subs.) They're fantastic, but they feel strained in a larger theater while playing at reference level and the bass pretty much drops to nothing bellow 25hz. Regardless, they are very pretty to listen to, have wonderful detail and flat, non-fatiguing, theater-like sound - just no real dynamics, intensity and pizzazz that I like to hear when I go to the local IMAX. I can't imagine what horn loaded compression tweeters and 12 inch mid drivers sound like in a residential environment but I'm hoping it creates that dynamic punch I'm looking for. I'm just worried about the ear-bleeding, honking fatigue and piercingly uncontrolled mid-range that is usually associated with horns and cheep PA speakers. Since there's not really any reviews out yet on the HTM-12's, I'm excited to read yours. I'm loving your detailed building posts and I'm on pins and needles to read your listening review! Thanks for taking the time to keep us all up to date on this new DIY speaker!
 
#23 ·
Thanks for the kind words, McCool, I'll try not to let you down! lol

I think we're in a great place/time to be starting a theatre build, being able to build with Atmos, 4k, etc. in mind. I know there is always a new thing on the horizon, but I don't think that there will be a significant change in speaker layout required (unless switching to an Auro 3D setup) for a long time. I'll try to make sure all the cables I run are HDCP 2.2 compliant, which should last a little while at least, and high enough bandwidth to pass whatever the latest version of HDMI is capable of, and UHD specs require. What else can happen after 4K and HDR? I don't know, but since I won't even have a full 4K display any time soon, I think I'll be fairly "future-proof" for a while at least. With that in mind, I'll try to run conduit for cables/wires where possible, to make replacement years from now a little easier, and that's about as safe as it can get I think.

I'm really looking forward to experiencing the SEOS speakers, especially with cinematic material. I have a Paradigm setup now, and there's nothing WRONG with them really, but the one big complaint I have is with dialogue clarity and coherence. My hope is that moving to 3 identical speakers, ditching the horizontal centre, and placing them in a more optimal location behind an AT screen will make big strides forward in that area. The SEOS horns have been praised for their clarity and dialogue rendering, and I can't wait to see how they work out. From my initial "drop in test" there wasn't a lot of bass from the 12, but that is by design. In my setup they'll be crossed over to a pair of UXL-18s, so they won't need to handle anything below 60Hz at the most (I'll play with crossover points from around 60Hz to 100Hz or above, since the UXLs are supposed to do well up that high). Are you thinking about replacing the SW-X1s as well? Any early candidates?

Owen..A small foam roller is perfect for the job.. Painting a smooth surface requires no nap..
Thanks Prof! I thought I remembered reading that somewhere. Now I'll have the confidence to try it. I was going to make a joke about ME needing a nap, but couldn't pull it together. I'm too tired. :rofl:
 
#25 ·
It sounds like a pair of subs and maybe a pair of midbass modules, or perhaps additional nearfield subs might work for you. Those seem to be the currently en vogue methods of increasing your tactile bass response, after you've got a capable "standard" sub. If you have lots of space in your room either behind or beside the seats, nearfield subs might be fun. Otherwise if you want a monster stack all tucked away behind the screen (where you've said you have lots of room) then maybe a pair of midbass modules are the way to go. Either way, you have options, and a lot of fun reading ahead. :)
 
#28 ·
After a bit of a slowdown with minimal progress in tiny steps (kids sick, us sick, frigid garage temps, busy schedules), I finally have a step worth showing.

The cabinets are finished with paint. Most surfaces got 3 coats, except the back and bottoms, which got 2 each due to flipping around while painting. The paint is Sherwin Williams Quali-Kote "Blacktop" in a flat finish. To be honest, it has a little more grey/green in it than I would like, but since they'll be behind the screen anyway I settled for "just OK" because it was a gallon of good quality flat almost-black paint from the mistint section and it only cost me $10.00. I have a ton left to do the subs, screen frame, anything else that needs to suck up light and won't be obviously visible in the room. If they were going to be visible, I think I would have tried laminate... that WilsonArt Asian Night is great looking stuff.

I thought I had a foam roller to use, but when I was ready to go it turned out that the roller I had didn't fit the handle I had, so I just uses a regular short nap roller. Again, they'll be behind the screen, so this is more about performance than looks. They really don't look bad, and the paint went on nice and covered well. It has the usual tendency of "flat" paints to show every little mark and finger smudge, so it will be interesting to see how these hold up through the rest of the build. I'll likely have to do some touchup eventually. The green was much more pronounced when the paint was wet, as you can see in the wet/dry comparison below (those closeups were after the first coat).

I'm still waiting for my binding posts. But the cabinets are otherwise ready for them so when they arrive I can get them all assembled and test out some music and movies. I'm excited to see how much of an improvement I get with dialogue. We watched Civil War last night and I have both the "dialogue" setting and the centre channel level cranked up to get intelligible voices in quiet passages. When we watch with the kids in bed I usually turn on the dynamic compression, but I don't think it's actually doing much to help. Anyway, some progress, and I'm just about at the end of this build. Finally.
 

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#30 ·
Sorry Prof., that wasn't very clear. The settings were cranked with my current setup (Paradigm CC 370). One of the main things I'm looking for is getting rid of the horizontal Centre for a matching LCR. I fully expect the new speakers to blow this setup out of the water.

Sent from my LG-H812 using Tapatalk
 
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