B&C DCX50 Coaxial Compression Driver

B&C DCX50 Coaxial Compression Driver

In this blog post I test the B&C DCX50 mounted to the ES290 Biradial No.1670.

The DCX50 mid frequency uses a paper diaphragm that looks very similar to regular cone speaker. (photo courtesy of tlhp)

The latest coaxial compression driver from B&C uses a polymer diaphragm. 

As we can see below from the published data, the DCX464 has mid-frequency extension up to 6kHz.

However the DCX50's midrange output extends flat to 9kHz with a 12kHz -6dB downpoint (see below). 

 Test Data 

With the DCX50 mounted to the ES290 Biradial, I measured the raw frequency response 

We can see that the response is ±3dB from 350Hz to 9.5kHz. 

The high frequency response is shown below measured at 30cm from the horn mouth. Here we have more variation at ±5dB from 6kHz to 16kHz.

If we overlay the MF and HF we get the following. 

It's a little difficult to see so I've cut below 10kHz for the HF for clarity.

Next I look at time domain performance for the mid-frequency.

The high frequency is shown below. 

I then conducted intermodulation distortion tests at 95dB 1m using a multi-band multitone test signal ranging from 300Hz to 20kHz. We can see the IMD is extremely low for the 500Hz region at -70dB. For reference, my in-house target is at least -60dB, so the performance of the this driver far exceeds the requirements for home audio by about 10dB. IMD rises to -60dB by 5kHz rising to -55dB by 8kHz. 

The high frequency did not fare so well at -50db. I also found out-of-band HF noise at only -40dB in the 30kHz region. 

Listening Impressions

I was immediately struck by the midrange tonal characteristics of this driver as having a distinctly paper sound. In other words, the driver sounds very similar to a paper cone driver. This is not surprising considering it actually is a paper cone. In fact, I was not even aware that this driver was a paper cone when I first listened to it. On the first note I turned to my computer and did a quick google search to see what the diaphragm material was, just to highlight my own absence of bias. Is paper a good thing? I think so. It has a warm melodic character. I attempted to integrate the HF into the mix but I was disappointed with the overall sound quality from the high frequency portion. The high frequency diaphragm is a polyester material and so it did not share the same tonal character as the midrange. 

Subjectively, the midrange has similar lower midrange authority as other large format drivers I've tested such as the DCX464, BMS 4591, and RCF ND950. Distortion is extremely low in the midrange allowing you to easily hear all subtle detail. I could easily follow subtle vocal articulation such as vibrato. 

Considering the excellent midrange performance, I would suggest the midrange only version, model DCM50 which is even lower cost at $488 USD each. This is  similar in cost to the RCF ND950. If you value a more melodic character common to paper drivers, this may be the direction for you. Perhaps this may pair well with tube amplification? I don't know, as I did not test, but it makes me wonder.

From a system design perspective I would suggest a biradial such as the ES290 or Yuichi A290 along with your favorite super tweeter coming in at 10kHz. 


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