DTQWT-12

[djdube525]

And doing all of this in 95-100 degree heat... Now that's dedication! Hopefully, you're tipping up a cold one after each of these steps.

Thanks for the explanation about the woofer holes... I was wondering the same thing.

[Carlman]

Wow, that is impressive craftsmanship.  You have some great skills, Rich.  That design sure does have all the components of what I would think sounds good... I'm really looking forward to hearing them sing.  
-C

[richidoo]

Carl, Thanks for the compliment. My skills are improving with each project. I hope they sound good too.  I don't see how they cannot sound "good," considering the design and parts quality, and the rep of the designer Troels Gravesen. He is very well respected among DIY speaker builders. The smaller version of this, called DTQWT (twin 10" woofers) has been built a few dozen times and everybody seems to really love them. Mine are the same drivers and crossovers as DTQWT but with  larger interior horns for the bigger (12") woofers. Here's hoping!! They are still boxy plywood speakers so I don't think the cabinet will be as quiet as a 4" thick MDF hifi speaker, but I do hope they will sing and make good music. I hope they will be able to play big so i can enjoy symphonies again. The one other guy that I know of who has built these big ones says that symphonies are awesome with his mastersound 50W parallel 845 SETs.   If the cabs are too noisy I can add more meat to the outside. The interior reflections are the only other cause for concern from my experiences with previous horn speakers, but the felt should take most of that down.

[Face]

Nice work so far!

Using a Jasper jig for the driver cutouts? 

[ebag4]

Hi Ed,
The woofer's OD is 12.5", and the through hole is 11-1/2". The rear panel width is only 11-5/8". The mounting flange recess will cut into the side panels' edge. To flush mount the drivers I need to cut the mounting flange recess before I cut the through hole in order to use the same centering pin location so the recess and through hole are concentric. Recess must be cut before through hole, so the sides must be glued on before cutting the recess. A little trickier but no biggie.
Rich

Thanks Rich, that is quite obvious now that you have explained it  .  Looking great, can't wait to read your impressions.

Best,
Ed

[richidoo]

Face, I use the small Jasper 400 jig for the tweeter hole, and an older model medium sized Jasper for the mid and woofer holes, with a carbide 1/4 porter cable bit. I see that the new mid size Jasper (bottom pic) goes down to 2.25" diameter. Mine doesn't go that small so I have to use the small round jig for small circles.


Small


Big

[richidoo]

Eminence woofer holes are 12 - 7/16" for flange, and 11" for the through hole.

[Bunky]

My god Rich how many manhours do you have in these beauties  your work looks very professional 

[richidoo]

Thanks Bunky! Just don't look too close

I do have quite a few hours in them, haven't been counting - but they are the most involved speakers I have built yet so I expected they would require good effort. I like the work, especially the woodworking. I don't look forward to steps that I have never done before, but after I learn how then it is fun. Some of the steps are fun than others, but I just keep murmuring  "one step at a time" under my breath to get through it. Today making 12 wire lengths for the hookups was pretty tedious, but gotta be done. Now I'm building the crossovers, that should be kinda fun, the parts are so pretty and I know they are awesome quality audio parts so it is exciting to bring them to life. I want to install the crossovers before gluing on the lid.

I look at it like Dr. Frankenstein, making a machine that will come to life, but I am slightly less passionate than him, fortunately.

[mgalusha]

Very cool indeed Rich, can't wait to hear your description of the results.

Not that you need one since you have a Jasper Jig but there is a widget called the Router Buddy that will cut circles from 2" to 18" with no steps, so you can get any size desired. It does require measuring during setup but that is a simple matter with something like a dial or digital caliper. I found out the hard way that cutouts can be so precise that the drivers are a press fit. I forgot to allow for any clearance, cut the holes exactly the same size as the driver and they were hard to get in and worse to get out. Lesson learned.

[richidoo]

Yup, I hate when that happens, hole cut too small and the centering pin is gone... especially in baltic birch which is hard to sand the hole bigger... Thanks for tip Mike. It looks like a nice tool, does just about everything too. I have often wished for finer resolution than Jasper's 1/16" min diameter. It won't be long before my router with small jasper rolls off the table saw (again.)

I was starting to get used to my midfi Infinitys, thinking they weren't too bad. Then I got to hear RichardS's new speakers this past Saturday. Peak Consult Zoltan, with full Tact electronics and 4 driver stereo subs. They sound even better than they look and they look like something out of the Bentley factory. Total refinement at any volume, and they are not even dialed in yet! Now I am much more motivated to finish my speakers asap. My goal is to hear them (in stereo) before I leave for Capital Audio Fest on Sat morning.

[Face]

I have both Jasper Jigs and the router buddy, I believe I used the router buddy once as it takes much longer to set up in comparison to either JJ. 

[richidoo]

A wicked lightning storm last night took out my internet so I was deprived of AudioNervosa and was "forced" to work on my speakers until midnight. My goal was to finish the crossovers yesterday, but there were a few things left to finish this morning. Behold, the brains:


2nd order midrange and tweeter filters together on the left, 1st order bass filter on the right.


With 12" woofer for scale.

The Jantzen electronic parts are extremely high quality. The mid and tweeter coils are copper foil dipped in hot wax to prevent mechanical motion between coils, which makes FM distortion. The bass coil is a huge toroidal core wrapped in thick copper windings. DCR is only  .17 ohms.  Silver Z caps to the tweeters, Superior Z caps to the mids, and non-inductive metal oxide film resistors.

It is looking cloudy so it may rain again today, which would prevent using the router outside to cut the woofer holes. But if it stays dry I'll make a mad dash to the finish today.

[Carlman]

Sweet!  Home stretch!

[richidoo]

One cool thing about this crossover is the ability to adjust the tweeter level. Three different resistors are provide, you can choose which one you want. You can see them all together at the top right. I have the largest value connected now, which is the preference of the designer, but I can increase the tweeter level (twice) if necessary. Just unsolder one resistor from the silver cap and solder on a different cap.

2 hours at the pool with the kids and now it is lightning storm again.      Now you guys can see why I like battery powered audio system, or a Pure Power or Brick Wall protection.   Maybe with these speakers I can try battery amp again. Sol designed a 50W battery amp with bipolar battery supply (two batteries) but we never built it.