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Discussion Starter · #1 ·
A few months ago, I made two three ways active Columns comprising each: one Atohm D300-P04 for the low frequencies, two Dynaudio 20W75 8 Ohms for medium freq and one Dynaudio D260 for highs. The enclosure is filtered and amplified by Digmoda DDC552.

The project was born from the will to transform my existing columns in order to have more bass. I like Rock and Pop, also Dance music so basses are paramount. :clap:
They were each made of one Dynaudio 20W75 8 Ohms and one D260 with a 2nd order filter created by a store selling kits that no longer exists. :sad:

The sensitivity of the tweeter being of about 5dB higher than that of woofer, I wanted to create a system MTM (appolito) and to increase by there the sensitivity of the woofers by 3dB. The modification of the filter would have been rather easy because it is approximately enough to double the components and to change the value of the resistance in serie with the tweeter. Ebay allowed me to find a new pair of woofers that Dynaudio does not market any more as parts. :rolleyesno:

Mr. Petoin Dominique (whom I thank here for his answers to my e-mails) and his site (in french) made me realize that if I wanted to go down low in frequency, I would quickly be limited by the excursion of the membrane of the 20W75. :eek:lddude:
I thus needed a third way dedicated to the basses. :reading:

The filtering of one three ways being a difficult enterprise, I decided to actively amplify all these beautiful people and my choice was made on a Digmoda DDC552 (ordered directly at Digmoda) whose characteristics of power matches perfectly the loudspeakers. :T
It is also equipped with an active filter + EQ that can be configured using a PC, a USB cable an the included D-PRO software.
Dean from Digmoda confirmed this choice and I thank him for all his advises and answers to my mails.

It was necessary to put all this small world in a box and I decided to manufacture broad columns with front mounted drivers.
For the basses, I kept same volume and the same vents as those of the Rafale sub-woofer kit from Atohm but I wanted a front-ported cabinet (the kit is rear-ported).
For mids and highs, I needed a much smaller volume, closed this time.
With a trapezoidal form for the sides , it was relatively easy to make a single cabinet,
the Digmoda amp fitting perfectly at the back. :sn:

Using the Digmoda, it was easy to make a three way filter and adjust output levels. I only used 2nd order filters.
I tried to flatten the bass response curve using the EQ capabilities but I finally decided to make no correction as the sound was much better uncorrected (I am just an amateur !). :ponder:
I tweaked the filters a little bit and the sound is great! :T

I have what I wanted when I started this project: more basses! The rest of the spectrum is as it used to be and I have always been happy with it.
The difference now is that the music really makes me willing to dance. :yay:
Even at low volume, basses are felt and give music more presence.

Some pictures later on when I am allowed by the site...

In the meantime, if someone could send me a link to a page explaining how to measure and time-align the speakers, I would be thankful as I could not find two persons agreeing on the method (time or phase alignment, use the peak, use the threshold, etc...) :justdontknow:
 

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Discussion Starter · #2 · (Edited)
As promised, some pictures:
(Legend on top)

Outboard: the 2 ways speakers I wanted to upgrade.
Inboard: the front plates of the new 3 ways speakers. Ouch! no very WAF :D


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A look inside....


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The new 3 ways next to the previous 2 ways speaker.


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And finished
Front face is painted, the rest is veneered with real oak coated with white glue diluted in water


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:wave:
 

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Very nice build. What software are you using for your measurements?
 

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Discussion Starter · #5 ·
Considering:
- It is better to make measurements at the listening position rather than a meter away
- one need a downward curve in the treble region (curve X ISO 2669, academy mono, B & K house curve, choose what suits you ...)
I performed the following measures (1/3 octave smoothing) in the axis at a distance of 2.6m after some equalization work above 200 Hz

I used REW in automatic mode between 200 and 2000 Hz for a flat response and in manual mode beyond 2000 Hz for the curve (which descends naturally) to be straight.
The calculated data have been copied manually into the D-Pro software supplied with the Digmoda amps and transmitted them via USB from the PC to the speakers (easy!).

We notice that the right speaker placed near a corner gives more level in the low frequencies (blue curve) and a slight depression between 200 and 300 Hz that I have not tried to correct.



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