The Zaph ZDT3 build

[jinjuku]

So my current project is the Zaph ZDT3 3.5 way speakers. My PSB setup is going on 13 years old. They have really gone the distance and I have been very happy with them. But time to move on:

Bottom chamber with an additional 1.75" X 7.5" brace clamped up front


The top half (both cavities are 0.69 cubic feet)


The Full Monty


The cabinet assembly is glue/clamp/brad nail. All seams are caulked out with a non Silicon RTV sealant. Just bead it on and smooth over w/ a finger. Speaking of brad nailer, I picked up a brad nailer at Harbor Freight for $20, along with a $30 belt sander. Both these 'cheap' tools did a great job. The build quality is more than adequate. For the occasional DIY project, $50 bucks couldn't have been better spent. I wonder what nationally recognized brand name these are clones of?

Other equipment that I will want going forward with future projects:

A bench disc sander; This will help getting components such as bracing to fit properly. The disc portion will ensure the you keep the sanded surface from rounding.

Drill press; drilling terminal cup/port/speaker flange holes perfectly perpendicular.

The wife gets to pick the cabinet veneer.

 

[Puppet Master]

Edit: removed the post

 

[stangbat]

I built the ZDT3, got it done last week. I'll be interested to hear what you think of them when you get yours done.

I can't post pics now since I have <5 posts. PM me and I'll send you some links. I'll also update the thread with pics once I reach 5 posts if anyone is interested.

 

[Sheep]

I hope some more bracing is going in there.

SheepStar

 

[jinjuku]

You mean the bottom right? Of course, don't be silly.

 

[stangbat]

jinjuku, evidently I can't send PMs yet either. Am I going to upset anyone if I post the URLs in the thread despite my low post count?

 

[jinjuku]

I think it would be ok... No one is forcing anyone to copy/paste a url into their browser.

Did you have madisound build the x-over for you? They only charge like $10 additional per...

 

[stangbat]

I think it would be ok... No one is forcing anyone to copy/paste a url into their browser.

Did you have madisound build the x-over for you? They only charge like $10 additional per...

No, I built everything myself. Honestly, the crossovers were one of the easier parts. I was thinking it would be harder than it was, but I got them knocked out pretty quickly.

The completed project is here, and you can get to my gallery from this image:
img406.imageshack.us/my.php?image=dsc4980largeyt2.jpg

A slideshow here:
img135.imageshack.us/slideshow/player.php?id=img135/9980/1207848861w96.smil

When I get to 5 posts I'll post pics. Haven't had a chance to browse around much and post yet.

 

[jinjuku]

Man, that is off the hook. Nice job. How do they sound?

With the internal 1.75 x 7.5 braces did you have to basically cut them to size and then sand a little and fit?

What veneer did you use?

 

[Sheep]

You mean the bottom right? Of course, don't be silly.

What are you using for Dampening material?

SheepStar

 

[jinjuku]

What are you using for Dampening material?

SheepStar

John Krutke calls for Sonic Barrier from Parts Express. So that is what I used. Guy seems to know what he is doing

 

[stangbat]

Man, that is off the hook. Nice job. How do they sound?

With the internal 1.75 x 7.5 braces did you have to basically cut them to size and then sand a little and fit?

What veneer did you use?

I got the braces to fit pretty well without having to do too much massaging. I think I did go back with the radial arm saw and shave a fuzz off a couple of them. If I was doing it again, I'd make those cross braces out of wood instead of MDF. The reason is I used threaded inserts for where the bolts mount. Drilling and putting threaded inserts into MDF is a hairy job. Luckily only one of the holes split the MDF and I glued and clamped it and it is okay.

Did you notice how I changed the front? I made a slight modification.

I used the Band-It red oak veneer from Parts Express. I applied it using the PVA glue iron-on method. It worked really well. If you need more info on this, let me know.

For damping I used Sonic Barrier. I used the 1/2", 1", and 1-1/4" three layer barrier. Two sheets of each was enough with not a lot left over. You can see how I installed it in my pics.

As for the sound, they are way beyond anything I have owned previously. While this is good, it has introduced some problems. They have shown that my listening area is much to lively as the highs are waaaay over accentuated. I bought a sound meter and I'm working on some room treatments to tone things down. I'm sure this is the case whenever you upgrade to better equipment, especially speakers. I also bought some higher value resistors to pad down the tweeter a little bit (2 ohm vs. 1.5 ohm as detailed on Krutke's site).

They really reveal poorly mastered recordings. Some things I enjoyed in the past now don't sound so great. However, some stuff sounds fantastic and much better than I ever imagined. And I'm hearing things in the music I never did before. For example, on Pink Floyd's "Mother" I can now hear the beater contact the kick drum. I never knew that was in the recording

One thing that surprised me is the bass. I didn't expect them to have the bass that they do. They aren't monsters, but the bass is now so tight compared to what I had before.

 

[jinjuku]

I got the braces to fit pretty well without having to do too much massaging. I think I did go back with the radial arm saw and shave a fuzz off a couple of them. If I was doing it again, I'd make those cross braces out of wood instead of MDF. The reason is I used threaded inserts for where the bolts mount. Drilling and putting threaded inserts into MDF is a hairy job. Luckily only one of the holes split the MDF and I glued and clamped it and it is okay.

Did you notice how I changed the front? I made a slight modification.

I used the Band-It red oak veneer from Parts Express. I applied it using the PVA glue iron-on method. It worked really well. If you need more info on this, let me know.

You flushed the speaker baffle with the rest of the cabinet? As far as the Band-It red oak I am assuming you sand the cabinet uniform and then cut a little larger, iron on and then trim. I am not going to screw on the front baffle, I will temporarily use clamps while I dial out the cabinets and then glue and brad nail.

What I want to know is did you apply a sealant/sealer to the entire cabinet (inside and out). I picked up a can of white primer/sealer for the purpose of doing that.

 

[stangbat]

You flushed the speaker baffle with the rest of the cabinet? As far as the Band-It red oak I am assuming you sand the cabinet uniform and then cut a little larger, iron on and then trim. I am not going to screw on the front baffle, I will temporarily use clamps while I dial out the cabinets and then glue and brad nail.

What I want to know is did you apply a sealant/sealer to the entire cabinet (inside and out). I picked up a can of white primer/sealer for the purpose of doing that.

I should clarify, I used paper backed veneer, not iron on veneer. I used the PVA-iron on method to apply the veneer. I'll post a link in the next post since I'll then have 5 posts.

I did not seal the entire cabinet since it would be veneered. I only used it on the baffles since they were painted.

One thing that worked well for me was to coat the edges of the baffles with PVA glue, let it dry, then sand. This sealed the edges of the baffles quicker than using the sanding sealer and I got a nice smooth edge.

 

[stangbat]

Here is a link to the PVA-iron on method:
http://oak.cats.ohiou.edu/~schneidw/audio/veneering.html
I tried using the tape against the edge when trimming like he recommended and I quit using it after one time. It was a PITA to remove and was not necessary. I also glued both cabinets and the veneer before starting. That way when I was ready to veneer, I went at it and didn't have to apply glue and wait for it to dry and worry about getting it on the unfinished veneer.

BTW, I did flush the baffle with the front. I then flared the roundover of the baffle into the 90 degree corner of the front.

I placed the crossovers in the empty space below the bottom enclosure, and I left the bottom open. So I have easy access to the crossovers if I need to tweak/change something.

 

[jinjuku]

I thought that I saw that on the bottom right corner of the baffle.
I am also going to mount the x-over in the bottom recess.

I hope over the next two weekends to get these finished. I was one of the lucky few to get the Aura NT1's. I have a total of four. This will leave me one extra after the L/R/C.

It's funny that John didn't want to do an RS-180 speaker because there are so many other MTM and TM designs out there. But up till the ZDT3, there wasn't a value proposition that I wanted to put the effort into. I think he had a sleeper design and didn't realize it.

The Aura NT1 looks like the tweeter the PSB uses on their Image series BTW.

 

[jinjuku]

BTW, I am planning on using a strong bond spray adhesive vs roll on of glue. I will of course test out. I will update you with the results.

 

[WmAx]

John Krutke calls for Sonic Barrier from Parts Express. So that is what I used. Guy seems to know what he is doing

Sonic Barrier wold be fortunate to have any acoustical dampening value of substantial effect below about 600 Hz. There are far better options, that cost no more, and are probably cheaper.

Apply at lest 1/4" in layers of Peel N' Seal(a generic kind of Dynamat) to the 3/4" MDF walls and then apply 2" thick high density(>4lb/ft^3) rockwool board or fiberglass board(OC705) to all walls, except for the rear behind the drivers, apply 4". In the bottom of the enclosure, apply 4", to prevent possibility of lower frequency standing wave in relation to the cabinet height. The 2" thick material will absorb nearly 100 percent of acoustical reflection/reverberation down to 250-275Hz, with a drop off in effectiveness under this point. The 4" thickness will have nearly 100 percent effectiveness down to 125-150Hz, with a drop off in effectiveness under this point.

Note: moderate bracing and a mass loaded dampening material such as Dynamat/Peel N' Seal will not make a cabinet acoustically irrelevant. But they will help significantly. Far more effort is required in cabinet design/construction in order to effect a very low output cabinet.

-Chris

 

[jinjuku]

Getting back to it...

After a LONG hiatus I am getting back to the project. The center channel is 100% mechanically functional. Just need to finish the cosmetics.

All I can say is: WOW. The mid range and imaging has just bloomed. It's stunning.

 

[sploo]

...apply 2" thick high density(>4lb/ft^3) rockwool board or fiberglass board(OC705) to all walls, except for the rear behind the drivers, apply 4".

Chris, if you're making a box with this much (very dense) padding, how do you adjust the inside volume?

I.e. are you considering the walls of the rockwool to effectively be the inside of the cabinet (for the purposes of volume calculation), and therefore building a much bigger box, or do you keep the same box size and have a much smaller open volume inside?