Zaph ZD3C w/ DQ25SC16 Tweeter Build

rsbonini

Member
2010-01-29 3:30 pm
I was looking to build the Zaph ZDT3.5/ZD3C speakers but with the same tweeter Zaph used on his ZA5 series designs. Since I was in need of a decent centre channel, I chose to start there.

While I went a different route with construction methods, the cabinet dimensions are exactly as specified. The baffle is not removable but was attached to the box with wood glue and dowels so that a 1" radius could be routed into the top and bottom edges. The finish is a walnut-ish formica. While this is my first speaker build, I've had the invaluable guidance and help of an experienced speaker DIYer.

Below are some photos of the progress to date.

Internal cabinet braces:

zd3c-v-build-01.png



Cabinet assembly:

zd3c-v-build-02.png


zd3c-v-build-03.png



Adding roundovers:

zd3c-v-build-04.png


zd3c-v-build-05.png


zd3c-v-build-06.png



Formica wrap:

zd3c-v-build-07.png



Modifying midrange mounting plate:

zd3c-v-build-09.png


zd3c-v-build-10.png



Cutting driver and port holes:

zd3c-v-build-08.png


zd3c-v-build-11.png


zd3c-v-build-12.png
 

rsbonini

Member
2010-01-29 3:30 pm
First testing and evaluation this week. The woofer and mid crossovers are as per Zaph's original design. Several concepts were attempted for the tweeter crossover, including some really detailed and welcome suggestions from a member of another forum.

Ultimately the local speaker DIYer made a suggestion based on the original Zaph 3rd order crossover, which seemed to provide the best starting point. After some iteration it seems to be at a usable point that sounds pretty good.

Meaurement setup:
IMG-20191212-210723-1.jpg


Response curve:
2019-12-15.jpg


Tweeter X-over circuit:
[IMGDEAD]https://i.ibb.co/5B0ZZv7/dq25-xover.jpg[/IMGDEAD]

I'm not too sure about the measurements lower down, and ultimately I'm just going to trust that Zaph's design is doing what it's supposed to down there. I am wondering if the upper response can be improved. The DQ25 does have a rising response that was expected.

I am wondering though, is it possible to reduce the dip from about 3.5KHz out to 9KHz? Any suggestions for how to do so? I'm wondering if adjusting R15, and using a pair of RC/RL shunts in place of R16 would be the best approach.
 

OlegSh

Member
Paid Member
2010-12-01 11:00 am
Germany
Really great woodworking!

I've build myself a pair of Zaph ZDT3.5 some years ago. They were my second speaker build. I still like them and use them as my main speakers. I also built a box for the center channel and have all the parts for it but did not assemble it yet.

Now to your build. May I ask you, why did you choose another tweeter? Did you model it before starting the actual build?

Regards,
Oleg
 

rsbonini

Member
2010-01-29 3:30 pm
Choosing another tweeter came down to two things: 1) I just didn't like the one originally selected by Zaph, 2) I'd heard builds of Zaph's ZA5 designs, liked them, and wanted to use at least some component I'd actually heard before.

I wanted to model the design but have limited time, so I could either model and hope something came of it one day, or just build it and make it work. I chose the latter. I figure I could always make mounting a plate and revert to the original tweeter if I had to.
 

OlegSh

Member
Paid Member
2010-12-01 11:00 am
Germany
From what I read some time ago, in this design the crossover between the original tweeter and the mid is very critical and the tweeter-mid pair should be treated as one block. Changing one driver requires a complete redesign of the crossover and thus careful consideration of various parameters. I am no expert but I'd guess that it will be difficult to make what you are now trying.
 
I am wondering though, is it possible to reduce the dip from about 3.5KHz out to 9KHz? Any suggestions for how to do so? I'm wondering if adjusting R15, and using a pair of RC/RL shunts in place of R16 would be the best approach.

Have you simmed this at all? Get your driver measurements into X-Sim and work from there.

Looks to me like you need a zobel to flatten out the top, perhaps change C9 to a much smaller value and increase L9 to compensate. Not easy to recommend changes without a hands-on.