BiAmpPro – Auditioning with Hummingbird

Active Hummingbird

I chose the Hummingbird because of the drivers’ impedances. The 5-1/4″ Dayton DSA135-8 midwoofer impedance is 8Ω, which is important since the TDA2050 are in mono-bridge mode. The Dayton ND25FW-4 tweeter, on the other hand, has an impedance of 4Ω. This suits my purpose as I want to hear how the TDA2030A sounds like driving a 4Ω load.

Dayton DSA135-8 with 2.5kHz 12dB Low Pass

The Black plot is the RAW response of the DSA135. The Blue plot is with the BiAmpPro woofer amplifier’s output. Since this section is in mono-bridge, the woofer’s return wire is connected to the -ve output of another TDA2050 and not to Ground. 

I am quite pleased to find that with a 12dB low pass filter at 2.5kHz, the cone breakup peak at 7.5kHz is attenuated by -20dB. At this level of attenuation, the 7.5kHz peak will not interfere with the treble.

Dayton ND25FW-4 with 2.5kHz 12dB High Pass

Next is the Dayton ND25FW-4 tweeter. The Black plot is the RAW response, that is no crossover is used. The Red plot is that of the BiAmpPro with the TDA2030A tweeter amplifier crossover at 2.5kHz high pass.

Astute readers will notice that the tweeter is rolling off at about 1.5kHz instead of 2.5kHz. It is not because the crossover is wrong. The cause is the ND25FW-4 response is not flat. There is a pronounced hump at 1.5kHz. So the crossover is in fact working correctly. 

Hummingbird’s Summed Response with BiAmpPro

Acoustically, the DSA135 and the ND25FW are crossing at close to 2kHz. Even though the crossovers are at 2.5kHz, it is still acceptable because the summation looks fine. Basically, there’s some over-lap from the tweeter but it’s not destructive. Note the +3dB rise at the crossover bandwidth. That’s typical of a Butterworth filter.

Hummingbird Frequency Response with BiAmpPro

The frequency response of the Active Hummingbird using the BiAmpPro is shown above. From this measurement, we can infer that the midrange will have some presence. Vocals will sound slightly forward.

Treble extension is pretty good. It is fairly flat up to 8kHz after which it drops 5dB abruptly. However, it doesn’t roll of completely. From 10kHz to about 16kHz, it still exhibits a flat response.

What is lacking with this Active Hummingbird is the bass. That is quite expected in a small 2-way. The bass is about -6dB below the midrange. Note that this measurement was made with the Hummingbird in 4pi placement. In use, it’s likely the Hummingbird will be up against a wall. This will boost the bass somewhat. More so when it is placed in a corner.

If 2pi or corner loading (pi/2) the Hummingbird is still not enough, we can apply a shelving bass boost with an fc of 250Hz. This will elevate the bass to the same level as the midrange.

Auditioning the BiAmpPro Hummingbird

I have been listening to the Active Hummingbird for a few days and I can’t find any faults with the crossover. Vocals are outstanding, as in the passive Hummingbird-TAThere is no excessive sibilance that irritates the ears. The treble is smooth without any harshness or grittiness. The bass is audible though not as loud as it should be. 

To get more bass, I hooked up the 10″ Albatross bandpass sub that I’ve been using with the Osprey-12. While the sensitivity is good, the Albatross lacks the upper bass to mate seamlessly with the Hummingbird. I eventually replaced it with the Toucan-SF and shifted the crossover frequency higher to 120Hz with a 24dB external crossover. What a difference that made. Now, the bass sounds right. The upper bass can be clearly heard. Overall bass character is tight and dynamic.

Lastly, I would like to touch on the TDA2030A and  the TDA2050 chip amps. The first and only time I heard them was when they were introduced, that’s in 1995. In the blink of an eye, 27 yrs flew by. Imagine my surprise when I powered up the BiAmpPro. The TDA2030A and the TDA2050 sound excellent. Granted, they are not as powerful as the TDA7293 and the LM3886, but when played within their limits, they sound just as good. Actually, at the volume I’m playing, it’s not even 1 Watt and it’s loud enough with me 6ft away. The BiAmpPro definitely has enough power for Nearfield Monitors and Back Ground Music in business establishments.

BiAmpPro PCB

The BiAmpPro should be available for purchase in about a month’s time. I’ve gone through five revisions with this pcb and I’m finally satisfied with the design. I’ll be sending it out to my pcb maker soon, along with other designs.