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My DIY Zaph Audio ZRT speaker build

Feanor

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For the heck of it a couple of year back I decide that I wanted to build a pair of DIY speakers. I had a couple of goals:
  • The new speakers must capable of high quality sound, and
  • They must be less imposing than my then current Magneplanar MG 1.6QR panel speakers
Before and After the new speakers
...
1600891635833.png

1600891708986.png


The hunt was then on for a suitable speaker design.

I had previously done a couple my own speaker designs using Harris Tech's Crossover Pro and Bass Box Pro software that turned out OK. But given my goal of high-quality I decided for a a design by an expert. After much searching looking kits at Madison, Meniscus, Parts Express, etc., I decided on Zaph Audio's ZRT 'Zaph Revelator Towers'. See ... http://www.zaphaudio.com/ZRT.htmlr

The ZRT's are small towers utilizing high quality Scan-Speak drivers, namely:
  • Illuminator D3004/6600 AirCirc Tweeter Textile Dome, and
  • ScanSpeak Revelator 18W/8531G-00 7" Mid Woofer 8 ohm
I selected the 2-way vented alternative versu the 2.5-way closed box because I deemed it would yield enough bass and better suited my budget.

The specs looked good. The frequency response and distortion graphs per the Zaph Audio look like this ...
On-axis measured response:
1600891787647.png


Measured far-field harmonic distortion:
1600891817532.png
f

The drivers and completed crossovers were (and are) available from Madisound. I selected the Goertz 14 ga. copper foil inductors upgrade. ...
https://www.madisoundspeakerstore.com/2-way-speaker-kits/zaph|audio-zrt-2-way-revelator-tower-parts-only-pair/

Zaph Audio designed the ZRT's for Madison's MD38T tower speaker enclosure, 1.33 cu.ft. However this enclosure is no longer available. Since I don't have access to a table saw, I looked for a close pre-fab alternative. This turned out to be Parts Express' Denovo Audio Knock-Down MDF 1.16 cu. ft. Tower Cabinet. Since this cabinet is a little smaller than the originally intended 1.33 cu.ft., I used Bass Box Pro to calculated a different vent length for the smaller volume. I glued an extra 1/4" of MDF to the front of the baffle to make it a full 1" thick.

Since fine cabinet finishing isn't one of my talents, I decided to use a simple painted finish on the MDF. I used a latex flat finish paint and dress the surface with carnauba automobile wax. I fabricated the black cabinet bases myself ...

1600891915336.png


These nearly finished pictures don't show the Part Express Acousta-Stuf Polyfill used to moderately pack the lowest section of each cabinet.

I don't have the equipment to properly test the final result, but it sounds great to me. The ZRT's are more transparent than the Maggies and have slightly better articulated bass ...
1600891993766.png
 
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Feanor

Feanor

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gfinlays

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I've recently built the 20 litre sealed version of this speaker using a baltic birch plywood cabinet to the same dimensions as the no-longer available MD20. Driver integration is superb, sound is very detailed with no harshness, bass is more than adequate and the soundstage is wide and deep. I'm very, very happy with them.
 
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Feanor

Feanor

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I've recently built the 20 litre sealed version of this speaker using a baltic birch plywood cabinet to the same dimensions as the no-longer available MD20. Driver integration is superb, sound is very detailed with no harshness, bass is more than adequate and the soundstage is wide and deep. I'm very, very happy with them.
I'm certainly very happy with my ZRT. I don't think using the slightly small box was a problem.

I'd love to see Amir test the ZRT but it certainly isn't practical for me to ship him a speaker.
 

tmtomh

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Very cool - thank you for sharing @Feanor! Also great to see that even without access to a full suite of woodworking tools one can assemble a very nice pair of DIY speakers.
 

gfinlays

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I'm certainly very happy with my ZRT. I don't think using the slightly small box was a problem.

I'd love to see Amir test the ZRT but it certainly isn't practical for me to ship him a speaker.
Indeed, there were some rumours around a few years back (closely linked to the designer of the 18W8531) that seemed to suggest it was designed for a 22 litre cabinet.

I'm in the UK, so shipping one of mine isn't really practical either......
 

akcole79

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I am building my ZRT in those exact same cabinets and went to look up what design adjustments to make and stumbled across this post. I'm even painting mine bright red as well, to match my turntable. :) A couple questions for you regarding the port:

Did you opt for a rear ported design for any reason other than aesthetics?
Also, how long did you end up making it (port tuning is not completely in my wheelhouse).

Is there anything you did that you wish you had done differently? I built my amplifier (a upgraded Dynaco ST-70) and my preamp (a PH-16 phono preamp), but this is my first foray into speaker building, so if you have the time, I'll take any tips on the project I can get.
 

Bassman999

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This is an older thread I know...
I have these same enclosures and want to have baffles be removeable.
It seems like that was done here based on the gasket and bolts.
Just wondering how it was done.
 

gfinlays

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It looks like Feanor used screws for his. I would consider glueing some small plywood blocks inside the cabinet and fitting threaded inserts or pronged T-nuts (glue them in with epoxy) into them for bolting the baffle on. MDF is not very good at holding fasteners.
 
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