The ChilL-baffle2

Updated on: February 24th 2019

After enjoying my ChilL-baffle speakers for quite some time, I thought that it was time for a design update. To achieve better bass and dynamics, I decided to add a 15" woofer to the design. I found a suitable driver at the PureAudioProject website.

The 15" OB-A15Neo woofer offered there has a few interesting characteristics: suitable for open baffle usage, QT of 0.72, a similar sensitivity at 94.6 dB/W as my Supravox Bicone, fs at 40.4 Hz, low distortion and a very large Xmax (6.03mm):
To investigate what the impact of adding the 15" Neo woofer is, I did some simulations with BoxSim. This tool helped me to simulate the frequency response with various driver locations and crossover filters. As additional equalizing will be done on PC Side, I chose a very minimalistic passive filter:

For now, the Supravox itself will not be filtered. To help the bass response a bit further, I decided to add a 12cm deep wing to the design:

First, the simulated response with only a Supravox Bicone driver:

Secondly, the simulated response with added OB-A15Neo woofer:

Not a spectacular deep bass yet, but the bass response has significantly improved under 100 Hz compared to the previous single full-range driver design.

After all the simulation work, it was time to try the design out! Geert came by to help.

Locating the centre of the 15" woofer.

Routing and sanding the woofer hole.

Mounting of the woofer.

Connecting to my Ncore amplifier (and filters).

Mod1: glueing the additional side panel.

Mod2: adding spikes to the bottom side.

After the construction and some burn-in of the woofers it was time to do some measurements of the completed speaker:

I used Room EQ Wizard with a calibrated Mini DSP UMIK-1 measurement microphone to measure the frequency response: (at 1m distance, 1/12 smoothing)

The overall response is reasonably flat. Luckily, the simulated dip around 700 Hz is not too bad in reality. The most significant dips are around 6.5 kHz and 250 Hz. Treble is rolling off already from ~10 kHz. Bass starts falling off very quickly below ~45 Hz.
I use a custom made tool to do equalisation on PC side.

Most of the major dips and the frequency extremes are compensated (note that later I added a filter to compensate for the 250 Hz dip as well).
I have been using the new setup for roughly a year now. In the beginning, I must admit that the Neo woofers sounded slower and duller than I had hoped for. Luckily, over time this changed drastically! The 15" Neo woofers really need some time to become fast and dynamic. Also, I made some improvements on the audio equipment itself to help the speed.

My current setup is:
  • Winamp with MAD decoder and custom output plug-in
  • Custom software for equalisation
  • Soekris DAC with Amanero USB to I2S module
  • USB TTL serial controller for digital volume control
  • 2.1m balanced microphone cable
  • NCore amplifier reduced gain (R141 removed)
  • Van den Hul CS-122 speaker cable
  • The Chill-baffle2... (with 2nd order filter for its woofer)

  • I am very happy with the improvements in sound realized with the new speakers and equipment. The speaker can be a lot of fun, especially with tracks with drums, bass and/or percussion. Tightness and deepness of bass have been greatly enhanced and dynamics have been improved. The speaker is great for fusion and funk IMHO. Instrument realism is improved as well, the sound is fuller than before while still being transparent. Dialog is easy to follow. They sound a bit like studio monitors, but without harshness. You can listen to them for hours without getting listening fatigue (at reasonable sound levels naturally). Well, the fatiguing part is that they can persuade you for nightly listening sessions... :-P

    Maybe a bit of coherence is lost compared to the single driver design, but the better bass makes up for this. Weakest point of the set are the highs. By equalisation I can raise the level above 10 kHz so that the treble is more in balance, but using a full-range driver for high frequencies has its limitations.

    In the meantime, I already think about the third incarnation of the Chill-baffle with a Heil AMT tweeter... oh well... :-)

    I would like to thank Geert Middel for helping me to build these speakers!

    Back please!!!