AmpsLab-Spk Projects Control 5 – Electronic Crossovers and Bi-amping (Part 7)

Control 5 – Electronic Crossovers and Bi-amping (Part 7)

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Synergy 18dB/oct Electronic Crossover

Having redesigned the Control 5 passive crossover, I just can’t resist to see whether the performance can be improved further with electronic crossovers. 

Out came the Synergy, my bi-amp kit using 2 units of LM3886TF chip amps. I developed this kit because I wasn’t happy with the quality of the electronic crossovers in the market. Almost all the crossovers today are tuneable but for the Synergy, I chose to have 5 fixed frequencies instead. The user can select via dip switches frequencies from 2kHz, 2.5kHz, 3kHz, 3.5kHz and 4kHz.

How is the Synergy crossover different from the upgraded passive crossover. I will start with the woofer first. The Blue plot in Fig 1 is with the upgraded 2nd order low pass passiver crossover.

Fig 1 – Woofer Passive Crossover at fc=2.5kHz (12dB/oct)

Fig 2 – Woofer Active Crossover at fc=2.5kHz (18dB/oc)

The Blue plot in Fig 2 is with the Synergy electronic crossover set at 2.5kHz (18dB/oct). The cone breakup peak is now lowered by  -20dB. 

Fig 3 – Tweeter Active Crossover at fc=2.5kHz (18dB/oct)

The Blue plot in Fig 3 is the RAW response of the tweeter. The Red plot is with the Synergy electronic crossover set at 2.5kHz high pass.

Fig 4 – Woofer Low Pass and Tweeter High Pass at fc=2.5kHz

Fig 4 shows the woofer and tweeter responses with the Synergy electronic crossover at 2.5kHz. Acoustically, the two drivers are crossing at about 2.2kHz.

Fig 5 – Control 5 Woofer and Tweeter Summation

The Black plot in Fig 5 shows the summation of the woofer and tweeter. The summation indicates that both drivers are summing well as no cancellations are observed on either side of the crossover frequency.

Fig 6 – Control 5 Frequency Response with Synergy crossover

Fig 6 is the final frequency response of the Control 5 with the Synergy 18dB/oct electronic crossover. This is a flatter response than the upgraded passive crossover.

Fig 7 – Synergy Control 5 Waterfall

Fig 8 – Synergy Control 5 Toneburst Energy Storage

The Waterfall and Toneburst Energy Storage plots are in Fig 7 and Fig 8. 

Control 5 sound quality with the Synergy

Does the Control 5 sound better with active biamping? Definitely. It sounds more dynamic and clearer than the previous one with the upgraded passive crossover. However, it’s quite impossible to differentiate the two, even in a controlled A/B test. It takes a highly trained ear to tell the two apart.

Part 1 – Thiele & Small Parameters
Part 2 – Woofer & Tweeter Measurements
Part 3 – Frequency Response
Part 4 – Step & Waterfall Measurements
Part 5 – Sound Quality
Part 6 – Upgrading the Crossover
Part 7 – Electronic Crossovers and Bi-amping

Note: Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.

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