StevenZ's DIY Jeff Bagby Helix Dome speaker build

StevenZ

Active Member
Welp, I've been bored for a while and wanted to sling some sawdust, however with the kids and work I'm finding less and less time to actually build anything from scratch. Drawing the CAD file and programming it to our router takes just a small amount of time, but adds one more layer on top of everything else (as well as ordering the material and actually running the program on our CNC). SO, I took the easy way out this time and ordered a DIYSoundGroup kit from Eric H. The kit is a relatively new design from Jeff Bagby that uses a custom-spec woofer special to DIYSG and one of Jeff's favorite tweeters by SB Acoustics (not beryllium).

Having built 3 designs from Jeff previously (DIYSG Fusion-12, Overnight Sensation, Mandolin) I'm familiar with Jeff's voicing on his designs and know they're going to be very comfortable to listen to. So I picked the Helix design with dome tweeter (ribbon design on the back-burner indefinitely). The design is a simple 2-way rear ported cabinet which is a pretty decent size. I'll be using these here at the office and am hoping low level volume will be engaging enough to side-step The Gatekeepers, my Markaudio Alpair 7.3s that have been here for the better part of 8yrs now. These speakers have outlasted the very best designs I've built, most of which include world-renowned drivers from SB Acoustics, Seas and Scanspeak, beryllium tweeters, etc. That's how highly I think of them in this application.

I think though, even if they DON'T side-step the Markaudios, which I'm kind of expecting, it'll be fine since I need a deeper diving speaker than what the little Alpairs can offer as to avoid actually putting in a couple of subwoofers here. From the minimal reviews I can find it seems like they'll be pretty high performance with the Denovo 7" driver being the real wildcard. No real esoteric parts are used here, especially in the crossover which use some pretty basic Bennic parts and others.

Eric's ship time is typically about a week and I ordered on last Thursday so I'd assume the whole kit will be here in roughly a week and a half from today / beginning of march. The kit comes with the front baffle already cut to size and with driver cutouts and rabbets done. I opted for the flatpack cabinets and custom PCBs for crossover layout. All that's left for me to do is order up a couple terminal cups, some wire, and maybe some polyfill.

Will post photos as I unpack the kit and begin the build. Stay tuned, folks!
 

StevenZ

Active Member
The kit arrived today and I have to say, I'm very impressed! I've used a similar tweeter to this in another of Jeff's designs (Mandolin) and it had the dimple dome but I'm not sure if they were metal faced like this one is. Either way, the tweeter looks fantastic and feels STOUT in the hand. The woofer I'm sure is some custom-spec driver from China, which isn't a knock at all but just noticed a model number stamped into the frame and did a quick Google search to find out that it's a generic frame, but the driver is custom spec, so not much more info on it other than what's posted on the DIYSG website. Either way, it feels great in the hand and looks to have excellent quality in construction.

Overall, quality looking kit, quality looking drivers, standard issue XO components that will do the job and an A+ packing job by Eric @ DIYSoundGroup.com I'm also quite impressed by the CNC panels. The cuts are smooth and the paths are nicely done. Everything fits perfectly. The only thing I'll need to do, and this is just personal preference, is to do a small 1/8" round-over on the inside cutouts of the internal bracing. This should optimize air flow a little and I've done it on all my speakers before without any ill-affect.

Will hopefully start assembling the XOs tomorrow and maybe just maybe have the cabinets assembled by Friday. We'll see.

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John Frum

Secret Society Member
Looks like a fun, rewarding build, Steven!

I've never found serious fault with any speaker Jeff has designed.
 

rogerfederer

Junior Member
this looks like a fun build. will follow this thread!
once again you have grabbed my interest re your markaudio 7.3 build. would love it if you could share the design at some point:)
 

StevenZ

Active Member
this looks like a fun build. will follow this thread!
once again you have grabbed my interest re your markaudio 7.3 build. would love it if you could share the design at some point:)

I'd say if you want to get the most out of them, contact Dave @ Frugal-Phile and buy his Fonken design and build that. It's not too difficult and will net the best results. My cabinet isn't anything to write home about and there's really something special with the alignment of Dave's own designs and these drivers. It'll be worth the effort, trust me.
 

rogerfederer

Junior Member
I'd say if you want to get the most out of them, contact Dave @ Frugal-Phile and buy his Fonken design and build that. It's not too difficult and will net the best results. My cabinet isn't anything to write home about and there's really something special with the alignment of Dave's own designs and these drivers. It'll be worth the effort, trust me.
what about pensil 7s? look easier to build
 

StevenZ

Active Member
Looks like these will be very nice speakers! :)

You are an artist with building speakers. :)

I wish I could take credit for the cabinets. Thankfully DIYSoundGroup makes it easy and offers fully cut front baffles and knock down cabinets. I took the easy road this time. All my other builds were from scratch though.
 

StevenZ

Active Member
Progress! Primer has been sprayed and Bondo has been applied to the MDF edges and brad nail holes. This is the major problem with butt jointing MDF; sealing the edges is a real PITA especially if you're planning on a painted finish. Obviously veneering them would be the most ideal solution here... but I have high hopes for the color I chose.

Cheers!

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MDF edge grain is a total pain. I usually use some wood glue mixed with water rub that in to the edge grain for a few thin coats, sand lightly with a block and I can usually then primer. Sometimes I still put a thin, skim coat of bondo on the edges before primer.

What color you planning on?
 

StevenZ

Active Member
MDF edge grain is a total pain. I usually use some wood glue mixed with water rub that in to the edge grain for a few thin coats, sand lightly with a block and I can usually then primer. Sometimes I still put a thin, skim coat of bondo on the edges before primer.

What color you planning on?

Planning on a color we had leftover from a customer job called "sea salt". We use pigmented lacquer".
 

StevenZ

Active Member
Speakers are done! Unfortunately the spray shop used the wrong color.... BUT, I'm still happy with the way they turned out. They're like a cool white/blue/gray color thing. The sound so far is quite nice and exactly what I had expected. Still within the first hour of break-in and I'm sure I have a long way to go with them till they're fully loosened up.

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MikeyFresh

Moderator
Staff member
Speakers are done! Unfortunately the spray shop used the wrong color.... BUT, I'm still happy with the way they turned out. They're like a cool white/blue/gray color thing. The sound so far is quite nice and exactly what I had expected. Still within the first hour of break-in and I'm sure I have a long way to go with them till they're fully loosened up.

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Far out, that might be the world's only Claymore Retro desktop amp/monitor stand.
 
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