The plot on the left is frequency response of the BC25 by Peerless.
Note the flatness from 2kHz to 10kHz. This is what you get when the tweeter is mounted on an IEC baffle of 1350mm x 1650mm (53″ x 65″). Now, none of us have speakers with baffles this humongous.
|This is what you get in real life.|
The Blue trace is the raw response of the BC25 with it mounted on my speaker with baffle dimensions of 130mm x 190mm (5″ x 7.5″). That is almost 1/10th of an IEC baffle.
And guess what? The result is it’s no longer flat. In fact, there is 3dB peak at 2,200Hz. This is the effect of baffle diffraction.
The Black trace is with a 12dB/oct filter.
|Tang Band W3-1364SA Crossover|
Let’s turn our attention to the W3.
The Blue trace is the W3 RAW response.
The Black trace is with a 6dB/oct filter.
|Super-Micro Frequency Response|
The above is the summed response with the BC25 wired in reversed phase. Disregard measurements below 500Hz.
Measurements made without any smoothing applied. The Super-Micro is exceptionally flat all the way up to 15kHz. Looks like it doesn’t deviate by more than +/- 2.5 dB.
Distortion is quite acceptable. Mostly 2nd harmonic (Orange Plot).
|Crossover Network |
If you’re keen to build this design, contact me for the component values and the box dimensions.
The Super-Micros exhibit an unusually focused sound. Very little smearing. Vocals and instruments are distinctly separated. And there’s depth in the music. The kind of effect when using a good compression driver/horn setup.
With their super flat frequency response, the Super-Micros are the ideal near field monitors for sound recording. For full range musical playback, just add an external subwoofer. Click on link to see Super-Micro 2.1 in use.
|Update (Sep 30,2016)|
I decided to remove all the passive crossover parts and re-configure the Super-Micro for active bi-amping. This is easily done with my Synergy Kit. I designed the Synergy specifically for testing of 2-way speakers. Since the BC25 is the one giving the most trouble, I started with that.
The 3 plots above are all with the Synergy’s built-in 18dB/oct crossover. Black is at 2,500Hz, Red at 3,500Hz and Blue at 4,500Hz.
This is the response of the Super-Micro when crossed at 2,500Hz (18dB/oct for the W3 and the BC25).
There is a hump at the crossover point (2,500Hz). After that, a depression at 5,000Hz. That valley is not caused by the crossover. It’s the tweeter’s natural response.
This is what the response looks like when crossed at 3,500Hz. Slightly better but still not good enough. The hump is less and the depression is still there.
Now, this is what I call a proper crossover. Frequency at 4,500Hz. See how well the W3 and the BC25 sum.
For clarity, the W3 and BC25 responses are removed. We can now see how incredibly flat the Super-Micro response is. Let’s not forget that no smoothing is applied to the plot. Even I am impressed. That’s why I said the Super-Micros will make fantastic near field recording monitors.
Just to be sure, I listened to the Super-Micros at 2,500Hz, 3,500Hz and 4,500Hz. They do, in fact, sound best at 4,500Hz. It’s a joy to listen to the Super-Micros with my Synergy amps. Nothing like a good active system.
September 17, 2016Projects